GSM Radio Network Planning

GSM Radio Network Planning and Optimization Chapter 5 GSM Radio Network Planning Confideniality level

Table of Contents

Chapter 5 GSM Radio Network Planning..................................................................................3

5.1 Overview...................................................................................................................... 3

5.2 Planning Foundation....................................................................................................5

5.2.1 Coverage and Capacity Target Confirmation....................................................5

5.2.2 Performance Target Confirmation.....................................................................6

5.3 Coverage Analysis.......................................................................................................7

5.3.1 Area Division.....................................................................................................7

5.3.2 Radio Environment Survey.............................................................................10

5.4 Network Structure Analysis........................................................................................11

5.4.1 Middle-Layer Station.......................................................................................11

5.4.2 High-Layer Station..........................................................................................12

5.4.3 Low-Layer Station...........................................................................................13

5.5 Traffic Analysis..........................................................................................................14

5.5.1 Traffic Prediction and Cell Splitting.................................................................14

5.5.2 Voice Channel Allocation................................................................................17

5.5.3 Control Channel Allocation..............................................................................20

5.6 Base Station Number Decision..................................................................................23

5.6.1 Characteristics of 3-sector base stations in urban areas.................................23

5.6.2 References for Design of Base Station Parameters........................................25

5.6.3 Uplink and Downlink Balance..........................................................................27

5.6.4 Cell Coverage Estimation................................................................................34

5.6.5 Base Station Address Planning.......................................................................37

5.6.6 Coverage Prediction........................................................................................39

5.7 Design of Base Station Address................................................................................39

5.7.1 Address design...............................................................................................39

5.7.2 Project Parameter Decision............................................................................42

5.8 Location Area Design................................................................................................58

5.8.1 Definition of Location Area..............................................................................58

5.8.2 Division of location areas................................................................................58

5.8.3 Others.............................................................................................................63

5.9 Dual-Band Network Design.......................................................................................64

5.9.1 Necessity for Constructing Dual-Band Network..............................................64

5.9.2 GSM 1800MHz Coverage Solutions...............................................................65

5.9.3 Location Area Division for Dual-Band Network...............................................67

5.9.4 Traffic Guidance and Control Strategies of Dual-Band Network.....................69

5.9.5 Dual-Band Networking Engineering Implementation.......................................71

5.10 Design of Indoor Coverage System.........................................................................75

5.10.1 Characteristics of Indoor coverage................................................................75

5.10.2 Indoor Antenna System Design.....................................................................76

2006-01-05 All rights reserved Page 1 of 124


5.10.3 Capacity Analysis and Design.......................................................................83

5.10.4 Frequency Planning......................................................................................85

5.10.5 Traffic Control................................................................................................85

5.11 Tunnel Coverage.....................................................................................................86

5.11.1 Characteristic of Tunnel Coverage................................................................86

5.11.2 Tunnel Coverage Solution.............................................................................87

5.11.3 Tunnel Coverage Based on Coaxial distributed antenna system..................89

5.11.4 Tunnel Coverage Based on Leaky Cable System.........................................92

5.11.5 Coverage Solutions to Tunnels in Different Length.......................................99

5.12 Repeater Planning.................................................................................................101

5.12.1 Application Background..............................................................................101

5.12.2 Working Principles of Repeater...................................................................106

5.12.3 Repeater Network Planning........................................................................108

5.13 Conclusion.............................................................................................................120



Chapter 5 GSM Radio Network Planning

5.1 Overview

The design of radio network planning (RNP) is the basis of the construction of a

wireless mobile network. The design level of network planning decides the future

layout of a network.

During network planning, the documents concerning base station distribution,

channel assignment, and cell data must be outputted. And the major tasks

involved are as follows:

1) Analyze carriers’ requirements on network coverage, capacity and quality.

2) Analyze the coverage and capacity features of the candidate mobile

communication systems and bands, and then analyze the investment

feasibility through estimating the network scale.

3) Decide the network structure and base station type based on further

analysis.

First analyze whether to construct a layering network according to user

distribution, propagation conditions, city development plan and existed

network conditions, and then analyze the sites within this area to decide

whether to use omni antennas or directional antennas to meet the

requirements on coverage and capacity.

4) Estimate the number of base stations

Before estimating the number of base stations, estimate the coverage

distance of base stations of various types in various coverage areas. The

factors deciding the effective coverage area of a base station include:

Valid transmit power of the base station

Working bands to be used (900 MHz or 1800 MHz)

Antenna type and installation position

Power budget

Radio propagation environment

Carriers’ indexes on coverage

Then through calculating the coverage distance and dividing the coverage

areas, you can obtain a rough number of base stations for various coverage

areas.

5) Plan an ideal base station address according to cellular structures.

According to geographic maps or administrative maps and with the help of

on-the-spot surveys, you can have a full understanding of the areas to be

planed, and then mark the area where the number of users is large as a



target address. After that, mark the addresses of other base stations

according to the ideal cellular structure and the result of link budget.

6) Calculate the number of channels of the cells of each base station

Estimate the traffic of a base station according to its ideal location, and then

obtain the number of carriers and channels needed by each base station by

checking Erl table according to the indexes of call loss rate.

Decide the frequency reuse mode according to band width, network quality

requirement, and equipment supportability.

Estimate the maximum base station configuration type according to the

frequency bandwidth and reuse mode provided by the construction carriers.

If the system capacity in some areas cannot be met, you need to add more

base stations or cells to the system according to cell splitting principles and

actual conditions. After that, reselect an ideal base station address on the

map and re-estimate the number of channels required by the base station.

7) Predict the coverage area and decide the project data, namely, perform the

preliminary emulation. The specific tasks are as follows:

Select the design indexes

Select the minimum received power and the penetration ratio index at the

coverage area edge.

Select the design parameters, which includes:

Antenna height (above the ground), antenna azimuth angle, antenna gain,

antenna tilt angle, base station height above sea level, base station type,

feeder length, antenna feeder system loss, combining and distribution

modes, transmitter output power, receiver sensitivity, base station diversity

reception, and diversity gains.

Predict the coverage area of each cell according to the propagation models

in different areas, and then give the opinions on adjusting the base station

address, antenna direction, antenna tilt angle, and antenna height in the

areas where dead zones may be present and signals are poor. Finally,

provide the project data.

8) Select actual base station address and decide base station type:

Perform filed examination according to the ideal base station addresses,

and then record the possible addresses according to various construction

conditions (including power supply, transmission, electromagnetic

background, and land taken over). Finally, recommend a suitable address

based on integrated consideration of the deviation from the ideal base

station address, the effect on future cell splitting, economic benefits, and

coverage prediction.

After the base station address is selected, decide the actual base station

type according to the number of base station channels.



After the base station type is decided, you need to make a scheme for

antenna configuration. For moving a network, if you intend to provide a best

combination scheme for the antenna feeders, you must fully investigate the

combination of the antenna feeders of the original carriers, plan the future

expansion of the base station, and design the combination of the antenna

feeders supported by current equipments.

9) Plan frequency and adjacent cell

Decide the frequency and adjacent planning according to the actual base

station distribution and type.

10) Make cell data

To ensure that the network runs stably, you must design the parameters

relative to performance for each cell. These parameters include system

information parameters, handover parameters, power control algorithm

parameters, and so on.

Note:

For the selection of handover bands, the handover algorithms to be enabled,

and whether to use frequency hopping, power control, and DTX, they must

be decided in coverage prediction and frequency planning, because the

related parameters will be used in emulation.

In addition, sections 5.9 and that later introduce the solutions to the planning of

dual-band network and the planning in special occasions.

5.2 Planning Foundation

5.2.1 Coverage and Capacity Target Confirmation

Before planning a network, you must confirm the network coverage and capacity

target and relative specifications from carriers. They are specified as follows:

Definition of coverage areas

Specific division of the service quality in coverage areas

Grade of service (GoS) at Um interface

Prediction of network capacity and subscriber growth rate

Available bands and restrictions on using bands

Restrictions on base station address and the number of carriers

Penetration loss in cars or indoor environment

Performance and sensitivity of base stations

Rules on base station naming and numbering

Information of the base stations in the existing network

Engineers perform the network planning and guide the subsequent construction

work according to the previous technical specifications. Because any change of



these specifications will affect network construction, you must discuss these

specifications with carriers and get their confirmation.

5.2.2 Performance Target Confirmation

Carriers emphasize much on the future network quality. Therefore, network

planning engineers must judge the indexes concerning network performance

according to construction difficulty and experience, and then cooperate with

carriers to design a reasonable solution.

Generally, the performance of voice services can be judged according to KPI

indexes, which are specified in Table 5-1

Table 5-1 Descriptions of KPI indexes

Number KPI index Meaning Test methodReference

value

1TCH congestion

ratio

TCH seizure

failures/attempted

TCH seizures × 100%

OMC < 2%

2SDCCH congestion

ratio

SDCCH seizures and

all busy

times/SDCCH seizure

requests × 100%

OMC < 1%

3 Call drop ratio

TCH call drop

times/TCH

occupation success

times × 100%

OMC < 2%

4Handover success

ratio

Handover success

times/handover

attempted times ×

100%

OMC > 92%

5 Call setup timeAverage call setup

timesDrive test < 10s

6Coverage

probability

The percentage of the

received level greater

than -90 dBm

Drive test > 90%

7

FTP average

download rate

(kbps)

Applied to GPRS Drive test ≥ 16

8FTP average

upload rate (kbps)Applied to GPRS Drive test ≥ 3.2

9Forward/reverse

transmission delayApplied to GPRS Drive test < 20s



10 Ping success ratio Applied to GPRS Drive test ≥ 90%

11 Ping average delay Applied to GPRS Drive test < 3.5s

12Mean opinion score

(MOS)

The voice quality is

divided into fiver

levels from excellent

to bad.

Drive test ≥ 3

Note:

The KPI indexes vary slightly with carriers.

The mean opinion score (MOS) in the previous table is divided into five levels,

which are specified in Table 5-2.

Table 5-2 Mean opinion score (MOS)

Quality level Quality evaluation standard

5 Excellent

4 Good

3 Fair

2 Poor

1 Bad

Note:

The call whose quality is above level 3 can access the mobile

communication network.

The call whose quality is above level 4 can access the public network.

5.3 Coverage Analysis

5.3.1 Area Division

I. Types of coverage area

The signal propagation models are applied in accordance with the propagation

environments in areas of different types. The signal propagation models decide

the design principles, network structures, grade of services and frequency reuse

modes for the radio networks in coverage areas. In order to decide the cell

coverage area, you can the radio coverage areas into the following four types:

Big city

Middle-sized city



Small town

Countryside

Error: Reference source not found lists the divisions.

Table 5-3 Coverage area division

Area type Description

Big city

Dense population

Developed economy

Large traffic

Dense high buildings and mansions distributed in

center areas

Flourishing shopping centers

Middle-sized city

Relatively dense population

Relatively developed economy

Relatively large traffic

Dense buildings distributed in center areas

Active and promising shopping centers

Small town

Relative large population

Promising economic development

Moderate traffic

Relative dense buildings distributed in center areas

A certain scale of shopping centers but with great

potentiality

Countryside

Scattered population

Developing economy

Low traffic

In addition, you must consider the coverage of the areas at the intersections and

various transport arteries, including:

Express way

National high way

Provincial highway

Railway

Sea-route

Roads in mountain areas

Generally, it is recommended to apply omni base stations in the countries plains

and the areas with restricted landforms. In big cities, middle-sized cities, and

along expressways, it is recommended to apply directional base stations.



II. Define the field strength at coverage area edges

When defining the field strength of the uplink edges of a service area, you must

consider the factors listed in Table 5-4.

Table 5-4 Typical factors concerning the definition for the filed strength at

coverage area edges

Factor Value

Mobile station sensitivity -102 dBm

Fast fading protection 4 dB (3 dB for countryside)

Slow fading protection 8 dB (6 dB for countryside)

Noise (environmental noise and

interfering noise) protection5 dB

Remark:

To ensure the indoor coverage in big and middle-sized cities, you can

consider 15dB for the average penetration loss between buildings and

consider adding 5dB to the protection margin.

Generally, the propagation loss of GSM 1800MHz signals is 8 dB greater

than that of the GSM 900MHz signals in average.

Radio links have two directions, namely, uplink direction and downlink

direction, and the coverage area is defined by the direction in which the

signals are poor, so you must consider the uplink and downlink balance.

Therefore, if you intend to plan an ideal network, you must make a good

power control budget so that the uplink and downlink can be as balance as

possible.

III. Define coverage probability

The definition of coverage probability varies with the coverage areas, and the

coverage probability is gradually improved along with the construction of the

network.

In China, the coverage probability can be defined according to Table 5-5.

Table 5-5 Definition of coverage probability at different stages and in different

areas

Construction

stageAreas Coverage target



Early stage

Significant national tourism areas,

expressways, national highways,

and the areas along busy railways.

Full coverage.

Other major roads, railways and

sea-routes

The coverage probability

must be greater than

90%.

Development

stage

Key areas, such as government

offices, press centers, airport

lounges, waiting rooms of train

stations, subways, commercial

office buildings of high ranks,

entertainment centers, and large

shopping malls.

With the development of

the network

construction, the number

of users grows larger

and they require

services of higher grade,

so the quality of indoor

coverage of the areas in

the left column must be

greatly enhanced.

Remarks:

Generally, a call must be ensured to access the network at 90% of the places

and 99% of the time within the coverage area.

For the outdoor environment in big cities, the two ratios must be greater.

For the areas in countryside, the two ratios can be lower.

For transport arteries, different standards are applied, and the coverage

probability can be defined in accordance with the types of the arteries.

5.3.2 Radio Environment Survey

Through surveying radio propagation environments, you can get familiar with the

overall landforms, estimate the rough antenna height, and select the proper radio

propagation model, among which the radio propagation model helps you

estimate the number of base station when predicting the coverage. If necessary,

you must adjust the propagation model.

For GSM 900MHz, the formulas estimating radio path loss in different areas are

simplified in Table 5-6.

Table 5-6 Formulas estimating radio path loss in different areas

Formula Application

area

Propagation model

adopted

Example



PLDU = 147.2 +

8d + 40.5lgd

Densely

populated

urban areas

Walfish-Ikegami If carrier frequency = 925

MHz, hBTS < hobstacle, and d <

0.5km, hBTS = 25mhobstacle =

30m, street width = 25m,

building width = 50m

PLU = 128.73 +

38lgd

Common

urban areas

Walfish-Ikegami If carrier frequency =

925MHz and hBTS > hobstacle,

hBTS = 25m, hobstacle = 20m,

street width = 25m, building

width = 50m

PLSU = 126 +

35lgd

Suburban

areas

Okumura-Hata If carrier frequency =

925MHz, hBTS = 30m

PLRU = 116 +

35lgd

Countryside

areas

Okumura-Hata If carrier frequency =

925MHz, hBTS = 30m

Note:

The four formulas provided in this section are applicable to simple estimation

during project survey only. For later planning, you must adopt the precise

propagation models. If necessary, you must further adjust the propagation

models through CW measurement.

5.4 Network Structure Analysis

When considering the layout of base stations, you must deeply analyze network

structure. Generally, according to network layers, a network can be divided into

middle-layer, high-layer, and low-layer. The base stations at the middle-layer

bear the greatest traffic in a network

5.4.1 Middle-Layer Station

I. Definition and application

A middle-layer station in big and middle-sized cities is defined as follows:

The antenna is installed on building tops.

The antenna height ranges from 25 to 30 meters, which is greater than the

average height of the buildings.

It covers several blocks.



In small towns and countryside areas, except the high-layer stations are

designed for controlling traffic flow or for landform reasons, most of the base

stations are middle-layer stations.

II. Advantages

Compared with high-layer stations, middle-layer stations can utilize frequency

resources more efficiently. Compared with low-layer stations, middle-layer

stations can absorb traffic more efficiently. Therefore, the middle-layer stations

bear the greatest traffic in a network.

III. Distance between stations

The average distance between most middle-layer stations range from 0.6 to 5

km except in countryside areas. In big cities, the distance between some middle-

layer stations is shorter than 0.6 km. However, it is suggested that the distance

between middle-layer stations in big cities cannot be shorter than 0.4 km. If this

distance is too short, the buildings will produce strong interference against the

signals of the base stations. In this case, to control the coverage area is quite

demanding.

IV. Challenges

Because no suitable ground objective is available, to ensure the quality of

service of a network is quite demanding. According to the experience on project

construction and maintenance, great challenge is present in the selection of base

station address, station design, project construction, network maintenance, and

network quality.

5.4.2 High-Layer Station


A high-layer station in big and middle-sized cities is defined as follows:

The antenna height ranges from 10 to 50 meters, which is far greater than

the average height of the buildings.

Its coverage areas contain the areas covered by multiple middle-layer

stations.

Because the high-layer stations make poor use of the frequency resources, they

are mainly applied to the traffic networks where people move fast in big and

middle-sized cities.

In addition, to control construction cost and meet coverage requirements, you

can install some high-layer stations in suburban areas, highroads, small towns,

and countryside areas.



II. Functions

The high-layer stations must be as fewer as possible but be as effective as

possible. They mainly provide services to the fast-moving subscribers in cities.

Note:

The coverage of high buildings is realized by indoor distribution systems.

5.4.3 Low-Layer Station


A low-layer station is defined as follows:

The antenna height is shorter than 20 meters, which is shorter than the

average height of the buildings.

The antenna can be installed on the outer walls of the lower floors of a

building, on the top of lower roofs, or in the rooms of a building.

Generally, at the early stage of the network construction, signal network design

is applied, so most of the base stations are middle-layer stations. After the basic

network is established, you must adjust the base stations and add new base

stations according to traffic and coverage requirements.

For populated commercial areas where the traffic is heavy, you can use low-

layer stations, which are constructed with micro cell layer and distributed

antenna system. In this case, not only the requirements on indoor coverage are

met, but also the interference and difficulties of base station selection caused by

short distance between stations are avoided. With the development of the

network, the low-layer stations will develop into the layering network structure.

II. Other considerations

The coverage area of a low-layer station is small, so it can fully use frequency

resources but cannot absorb the traffic efficiently. As a result, ideal traffic cannot

be ensured if the base station deviates far away from the areas where the traffic

is heavy.

Therefore, when constructing a low-layer station, you must consider whether the

base station is used to make up coverage or solve the problem of heavy traffic,

because the construction purpose is directly related to the selection of the

address and type of the base station.

Note:

A layering network cost much frequency resource, so it is not recommended for

the networks where the frequency resource is inadequate.



5.5 Traffic Analysis

5.5.1 Traffic Prediction and Cell Splitting

I. Traffic prediction

The network construction requires the consideration of economic feasibility and

rationality. Therefore, a reasonable investment decision must be based on the

prediction of the network capacity of the early and late stage.

When predicting network capacity, you must consider the following factors:

Population distribution

Family income

Subscription ratio of fixed telephone

Development of national economy

City construction

Consumption policy

After predicting the total network capacity, you must predict the density of

subscriber distribution. Generally, base stations are constructed in urban areas,

suburban areas, and transport arteries. Therefore, you can use the percentage

of prediction method.

At the early stage of construction, the subscribers in cities account for a larger

percentage of the total predicted subscribers. With the development of the

network construction, the percentage of the subscribers in suburban areas and

transport arteries grows. The traffic of each subscriber is 0.025 Erl in urban areas

and 0.020 Erl in suburban areas.

The formula calculating traffic is:

A = (n × T) / 3600

Here,

“n” is the call times in busy hour

“T” is the duration of each call, in the unit of second.

In this way, the number of voice channels needed for a base station can be

obtained through predicting the traffic.

Note:

When estimating the number of voice channels needed for a base station in the

future, you must consider the effect caused by cell splitting.



In a GSM system, you can use Erl model to calculate the traffic density that the

network can bear. The call loss can be 2% or 5% depending on actual

conditions.

Because restrictions on cell coverage area and the width of the available

frequencies are present, you must plan the cell capacity reasonably. If good

voice quality is ensured, you must enhance the channel utilization ratio as much

as possible.

In actual networking, if the network quality is ensured at a certain level, two

capacity solutions are available, namely, a few stations with high-level

configuration and multiple stations with low-level configuration. Both the

advantages and disadvantages of the two solutions are apparent, so which one

should be used depending on the actual conditions of an area.

For network construction, you can expand the capacity either through adding

base stations or through expanding the base station capacity. The expansion

strategies adopted must be in accordance with the traffic density in an area. For

example, the strategies such as adding 1800 MHz base stations, expanding

sector capacity, adding micro cells, or improving indoor coverage can be used to

expand network capacity.

II. Cell splitting

Cell splitting is quite effective for the expansion of network capacity. An omni

base station can split into multiple sectors, and a sector can split into multiple

smaller cells. In other word, you must plan cell radius in accordance with the

traffic density of an area.

Cell splitting means more base station and greater cost are needed. Therefore,

when planning a network, you must consider the following factors:

The rules and diagrams of frequency reuse are repeatable.

The original base stations can still work.

The transition cells must be reduced or avoided.

The cell can split without effect.

Cell splitting is quite important in a network. The followings further describe the

cell splitting based on 1-to-4 splitting.

Cell splitting is used to split a congested cell into multiple smaller cells. Through

setting the new cells whose radiuses are smaller than the original cells and

placing them among the original cells, you can increase the number of channels

in a unit area, thus increasing channel reuse times. In this case, system capacity

is expanded.

Through adjusting the project parameters relative to antenna feeders and

reducing transmitter power, you can narrow the coverage area of a cell. Error:



Reference source not found shows that a cell splits into four smaller cells by half

of its radius.

Figure 5-2 Schematic diagram of cell splitting (1-to-4)

As shown in Figure 5-2, smaller cells are added without changing the frequency

reuse mode. They are split proportional to the shape of the original cell clusters.

In this case, the coverage of a service area depends on the smaller cells, which

are 4 times outnumber of the original cells. To be more specifically, you can take

a circle with the radius R as an example, the coverage area of the circle with the

radius R is 4 times that of a circle with the radius R/2.

According to Figure 5-2, after cell splitting, the number of cell clusters in the

coverage area increases. Thus the number of channels in this coverage area

increases and the system capacity is expanded accordingly.

You can adjust the coverage area of the new cells through reducing the transmit

power. For the transmit power of the new cells whose radiuses are half of that of

the original cell, you can check the power “Pr” received at the new cell edge and

at the original cell edge, and make them equal. However, you must ensure that

the frequency reuse scheme of the new micro cells is the same as that of the

original cell. As for Figure 5-2,

Pr [at the edge of the original cell] = Pt1R-n, and,

Pr [at the edge of the new cell] = Pt2 (R/2)-n

Here,

Pt1 and Pt2 are the transmit power of the base stations of the original cell and the

new cell, and n is path fading exponent. If make n = 4, make the received power at



the edge of the new and original cell equal, the following equation can be

obtained:

Pt2 = Pt1/16

That is to say, if the micro cells are used to cover the original coverage area and

the requirement of S/I is met, the transmit power must be reduced by 12 dB.

Not all cells need splitting. In fact, it is quite demanding for carriers to find out a

perfect cell splitting scheme. Therefore, many cells of different scales exist in a

network simultaneously. As a result, the minimum distance among intra-

frequency cells must be maintained, which further complicate frequency

allocation.

In addition, you must pay attention to the handover because success handover

ensure the all subscribers to enjoy good quality of service regardless of moving

speed.

As shown in Figure 5-2, when two layers of cells are present within an area but

their coverage scale is different, according to the formula Pt2 = Pt1/16, neither all

new cells can simply apply the original transmit power, nor all original cells can

simply apply the new transmit power.

If all cells apply great transmit power, the channels used by smaller cells cannot

be separated from the intra-frequency cells. If all cells apply lower transmit

power, however, some big cells will be exclusive from the service areas.

For the previous reason, the channels in the original cells can be divided into two

groups. One group meets the reuse requirement of the smaller cells, and the

other group meets the reuse requirement of the bigger cells. The bigger cells are

applied to the communication of fast-moving subscribers, which requires a fewer

handover times.

The power of the two channel groups decides the progress of cell splitting. At the

early stage of cell splitting, the channels in the low-power group are fewer. As

the requirement grows, more channels are needed in low-power group. The cell

splitting does not stop until all channels within this area are applied in the low-

power group. In this case, all cells in this area have split into multiple smaller

cells, and the radius of each cell is quite small.

Note:

Commonly, you can restrict cell coverage area through adjusting the project

parameters of the base station.



5.5.2 Voice Channel Allocation

I. Voice channel decision

The base station capacity refers to the number of channels that must be

configured for a base station or a cell. The calculation of the base station

capacity is divided into the calculation of the number of radio voice channels and

the calculation of the number of radio control channels.

According to the information of base stations and cells and the density

distribution of subscribers, you can calculate the total number of the subscribers.

Then according to the radio channel call loss ratio and traffic, you can obtain the

number of voice channels that must be configured by checking Erl B table.

Generally, you can decide the number of voice channels as follows:

11) According to the bandwidth and the reuse mode allowed by current GSM

networks within the areas to be planned, you can obtain the maximum

number of carriers that can be configured for a base station.

12) Each carrier has 8 channels. You can obtain the maximum number of voice

channel numbers that can be configured for a base station by detracting the

control channels from the 8 channels.

13) According to the number of voice channels and call loss ratio (generally 2%

dense traffic areas and 5% for other areas), you can obtain the maximum

traffic (Erl number) that the base station can bear through checking Erl B

table.

14) Through dividing the Erl number by the average busy-hour traffic of

subscribers, you can obtain the maximum number of subscribers that the

base station can accommodate.

15) According to the data of subscriber density, you can obtain the coverage

area of the base station.

16) After the areas are specified based on the subscriber density, according to

the area of an area and the actual coverage area of the base station, you

can calculate the number of needed base stations.

17) For important areas, you must consider back up stations and the

cooperation between carriers. For example, an important county needs at

least two base stations and three important carriers.

18) For the areas where burst traffic is possible, such as the play ground and

seasonal tourism spots, you must prepare the equipments (such as carriers

and micro cells) and frequency resources for future use.

19) The dynamic factors, such as roaming ratio, subscriber mobility, service

development, industry competition, charging rate change, one-way charge,

and economic growth, must be considered.



20) To configure a base station, you must consider the transmission at the Abis

interface so that the capacity can be met while saving transmission. For

example, the application and concatenation of the Abis interface 15:1 and

12:1 should be considered.

21) For indoor coverage and capacity, you can use micro cells and distributed

antenna systems. For the coverage in countryside areas and highroads, you

can use economical micro base stations. For the transmission in

countryside areas and highroads, you can use HDSL because it is cost

effective.

22) Prepare the some carriers, micro cells, and micro base stations for new

coverage areas and future optimization.

23) In some special areas, you can use the base stations consisting of omni and

directional cells, but you must consider the isolation between omni antennas

and directional antennas. For traffic control, you can use the algorithm in

terms of network layers.

24) For some highroads which require a little traffic by large coverage, you can

use the two networking modes. They are:

(A micro base station with single carrier) + (0.5 + 0.5 cell with two set of

directional antennas)

A micro base station with single carrier + 8-shaped antenna

II. Relationship between carrier number and bearable traffic

Erl traffic model can calculate the traffic that a network can bear. The call loss

ratio can be 2% or 5% according to actual conditions. Table 5-1 describes the

relationship between the number of carriers and the traffic that a network can

bear according to Erl B table.

Table 5-1 Relationship between the number of carriers and the traffic that a

network can bear

Number of carriers in

each cell

Number of

TCHsTraffic (Erl)

– – 2% 5%

1 6 2.27 2.96

2 14 8.2 9.73

3 21 14.03 16.18

4 29 21.03 23.82

5 36 27.33 30.65



6 44 34.68 38.55

7 52 42.1 46.53

8 59 48.7 53.55

9 67 56.25 61.63

10 75 63.9 69.73

According to this table, the larger the number of carriers and the call loss ratio

are, the greater the traffic that each TCH bear, and the greater the TCH

utilization ratio is (the channel utilization ratio is an important indicator of the

quality of network planning and design). If the number of subscribers of a base

station is small, you can consider delaying the construction.

Because restrictions on the coverage area of a cell and the bandwidth of the

available frequencies, you must plan a reasonable capacity for the cell. If good

voice quality is ensured, you must take measures to enhance the channel

utilization ratio as much as possible.

For the construction of the dual-band network, you can use the frequencies with

wider bands to enhance channel utilization ratio, which is helpful for traffic

sharing.

In actual applications, when the traffic on each TCH accounts for 80-90% of total

given by Erl B table (the call loss ratio is 2%), the congestion ratio in this cell rise

greatly. Therefore, we generally calculate the traffic that a network can bear by

taking the 85% of the traffic given by Erl B table as a reference.

III. Example

The capacity of a local network needs to be expanded. According to the service

development, population growth and mobile popularity, the subscribers in this

area are expected to reach 100,000 in 2 years.

If only the followings are considered:

Roaming factor (according to the development trend of traffic statistics) =

10%.

Mobile factor (the subscriber moves slightly within the local network instead

of roaming) = 10%.

Dynamic factor (with burst traffic considered) = 15%.

The network capacity = 100000 * (1 + 10% + 10% + 15%) = 135,000.

However, because the congestion is present, we generally calculate the traffic

that a network can bear by taking the 85% of the traffic given by Erl B table as a

reference. As a result, the network capacity must be designed as follows:



The network capacity = 135, 000/85% = 158,800, about 160,000.

5.5.3 Control Channel Allocation

I. SDCCH allocation

Stand-alone dedicated channel (SDCCH) is an important channel in a GSM

network. Mobile station activities, such as location update, attach and detach,

call setup and short message, are performed on SDCCH. The SDCCH is used to

transmit signaling and data.

Table 5-2 describes SDCCH configuration.

Table 5-2 SDCCH configuration principles

No cell broadcast channel (CBCH)

TRX

number

SDCCH configuration

General cell Internal cell Edge cell

1 SDCCH/4 SDCCH/4 SDCCH/4


3 SDCCH/4+SDCCH/8 SDCCH/4+SDCCH/8 SDCCH/4+SDCCH/8

4 2*SDCCH/8 SDCCH/4+SDCCH/8 2*SDCCH/8

5 2*SDCCH/8 2*SDCCH/8 2*SDCCH/8

6 SDCCH/4+2*SDCCH/8 2*SDCCH/8 SDCCH/4+2*SDCCH/8

7 SDCCH/4+2*SDCCH/8 SDCCH/4+2*SDCCH/8 3*SDCCH/8


Cell broadcast channel (CBCH) is present

TRX

number

SDCCH configuration

General cell Internal cell Edge cell


2 SDCCH/8 SDCCH/8 SDCCH/8+SDCCH/4

3 SDCCH/4+SDCCH/8 SDCCH/4+SDCCH/8 SDCCH/4+SDCCH/8


5 2*SDCCH/8 2*SDCCH/8 2*SDCCH/8+SDCCH/4



6 SDCCH/4+2*SDCCH/8 SDCCH/4+2*SDCCH/8 SDCCH/4+2*SDCCH/8

7 3*SDCCH/8 SDCCH/4+2*SDCCH/8 3*SDCCH/8

8 3*SDCCH/8 3*SDCCH/8 3*SDCCH/8+SDCCH/4

It is difficult to induce a traffic model for the SDCCH; especially it even becomes

impossible after the large-scale application of layering networks and short

messages. Moreover, the equipments of some carriers support SDCCH dynamic

allocation function. As a result, the traffic model for SDCCH must be adjusted

according to actual conditions.

The advantages of the SDCCH dynamic function are as follows:

Adjusting SDCCH capacity dynamically

Reducing SDCCH congestion ratio

Reducing the effect of initial SDCCH configuration against system

performance

Making SDCCH and TCH configuration more adaptive to the characteristics

of cell traffic

Optimizing the performance of the systems under the same carrier

configuration.

In conclusion, the SDCCH dynamic allocation function is divided into two types,

namely,

Dynamic allocation from SDCCH to TCH

Dynamic recovery from SDCCH to TCH

II. CCCH allocation

Common control channels (CCCH) contain access grant channel (AGCH),

paging channel (PCH) and random access channel (RACH). The function of a

CCCH is sending access grant message (immediate assignment message) and

paging message.

All traffic channels in each cell share the CCCH. The CCC can share a physical

channel (a timeslot) with SDCCH, or it can solely occupy a physical channel. The

parameters relative to the CCCH include CCCH Configure, BS AG BLKS PES,

and BS PA MFRMS.

Here,

CCCH Configure designates the type of CCCH configuration, namely,

whether the CCCH shares one physical channel with the SDCCH. If there

are 1 or 2 TRX in a cell, it is recommended that the CCCH occupies a

physical channel and share it with the SDCCH. If there are 3 or 4 TRXs, it is

recommended that the CCCH solely occupies a physical channel. If there



are more than 4 TRX, it is recommended to calculate the capacity of the

paging channels in the CCCH according to actual conditions first, and then

you can perform the configuration.

BS AG BLKS PES indicates that the number of CCCH message blocks

reserved to the AGCH. After CCCH configuration is done, this parameter, in

fact, decides allocates the ratio of AGCH and PCH in CCCH. Some carriers

can set sending priority for the “access grant message and “paging

message”. When the former message set to be prior to the later one, the BS

AG BLKS PES can be set to 0.

BS PA MFRMS indicates the number of multi-frames that can be taken as a

cycle of paging sub-channels. In fact, this parameter decides the number of

paging sub-channels that a cell can be divided into.

Note:

In CCCH configuration, the location area planning, paging modes and system

flow control must be considered.

5.6 Base Station Number Decision

After traffic and coverage analysis, according to the selected base station

equipments and parameters, you can obtain the coverage areas of various base

stations through link budget. The coverage area helps you calculate the number

of base stations required by each area. Then you decide the base station

configuration according to traffic distribution. Finally, you must perform emulation

using relative planning software so that coverage, capacity, carrier-to-

interference ratio can be assured and interference can be avoided.

5.6.1 Characteristics of 3-sector base stations in urban areas

Cellular communication is named because the coverage areas of base stations

are extruded through small cellular-shaped blocks. In urban areas, for the

purpose of capacity expansion and radio frequency optimization, mainly 3-sector

base stations are used. This section explains some basic concepts of a 3-sector

base station.

For the concept of the cell radius, see Figure 5-2.



Figure 5-2 3-sector cellular layout

This is a standard 3-sector cellular layout. According to Figure 5-2, the distance

between two 3-sector base stations is R + r, here R = 2r. However, “R” is mainly

used in cell radius estimation because the direction along “R” is the direction of

the major lobe of the directional antenna. In the design for cellular layout,

however, “r” indicates the cell radius.

In a cellular cell, if the included angle between a direction and the direction of the

major lobe of the antenna, the coverage distance along this direction is r = R/2,

and the path loss along this direction is about 10dB less than that along the

direction of the major lobe of the antenna (for the deduction, it is introduced in

the following), namely, the equivalent isotropic radiated power (EIRP) along this

direction can be about 10dB less than that along the major lobe.

According to this feature, in the cellular layout of this kind, you can adopt the

directional antenna whose azimuth beam width ranges from 60 to 65 degrees

because their horizontal lobe gain diagram also meets this feature.

If “R” is the cell radius, the cell area is S = 0.6495 × R × R. Sometimes the “r” is

used as cell radius, so the cell area is S = 2 5981×r×r. Therefore, when

calculating the cell area, you must make clear whether “r” or “R” is used.

Figure 5-3 shows the relationship between “R” and “r”.



Figure 5-3 Relationship between “R” and “r”

The followings deduce the EIRP required along “R” direction and “r” direction.

As shown in Figure 5-3, the coverage distance along “r” direction is half of that

along “R” direction, namely, r = R/2. To keep even coverage, you must make the

field intensity at the edges of the cell equal, namely, RxlvelB = RxlevelC.

Suppose that the EIPR transmitted from cell A is EIRPR and EIRPr along “R”

direction and “r” direction respectively, and the city HATA mode is used for path

loss, the path loss from point A and B is expressed as equation (1) :

EIRPR – RXLEVB = 69.55 + 21.66lgf - 13.82lgh1 + (44.9 - 6.55lgh1) lgR (1)

And the path loss from pint A to point C is expressed as equation (2):

EIRPr- RXLEVc = 69.55 + 21.66lgf - 13.82lgh1 = (44.9 - 6.55lgh1) lgr (2)

Subtract (2) from (1), the equation (3) is expressed as follows:

EIRPR - EIRPr =(44.9 - 6.55lgh1)×(lgR – lgr) =(44.9 - 6.55lgh1) × lg (R/r) (3)

Introduce R = 2r, the equation (4) is obtained as follows:

EIRPR - EIRPr = 0.3 × (44.9 - 6.55lgh1) (4)

Figure 5-4 shows the relationship between antenna height and values of (EIRPR

- EIRPr).

Figure 5-4 Relationship between antenna height and values of (EIRPR - EIRPr)

As shown in Figure 5-4, when the antenna height “h1” increases from 5m to

100m, the values of (EIRPR - EIRPr) decrease from 12 to 9.5, which can be

roughly treated as 10dB.

5.6.2 References for Design of Base Station Parameters

When estimating the number of base stations, you must perform uplink and

downlink budget. Based on the coverage division and propagation environment

survey, you can obtain some project parameters and apply them to link budget.

Table 5-1 lists some recommended base station parameters



Table 5-1 References for base station parameters

Coverage target

Big and middle-sized

citiesSmall cities Highroads

Network type GSM 900MHz GSM 900MHz GSM 900MHz

Antenna gain (dBi) 15 17 18

Coverage target

Big and middle-sized

citiesSmall cities Highroads

Network type GSM 900MHz GSM 900MHz GSM 900MHz

Antenna

height

Densely

populated

urban

areas

25 – –

Other urban

areas30 30 –

Suburban

areas35 35 35

Countryside

areas45 45 45

Antenna

diversity gain

(dB)

Densely

populated

urban

areas

4 – –

Other urban

areas4 4 –

Suburban

areas3 3 3

Countryside

areas3 3 3



Building

penetration

loss (dB)

Densely

populated

urban

areas

25 – –

Other urban

areas20 20 –

Suburban

areas15 15 –

Countryside

areas15 15 –

Car penetration loss (dB) 10 10 10

Slow fading

margin (dB)

Densely

populated

urban

areas

8 – –

Other urban

areas8 8 –

Suburban

areas8 8 8

Countryside

areas8 8 8

Note:

The more densely the base station addresses, the lower the antenna height is.

The building penetration loss in northern cities is greater than that in southern cities.

5.6.3 Uplink and Downlink Balance

After base station parameters are specified, you can perform link budget to

estimate the coverage area of the base station. In addition, you must consider

the sensitivity of the base station equipments at this time.

In a mobile communication system, radio links are divided into two directions,

namely, uplink and downlink. For an excellent system, you must perform a good

power budget so that the balance is present between uplink signals and downlink

signals. Otherwise, the conversation quality is good for one party but bad for the



other party at the edges of the cell. If uplink signals are too bad, the mobile

station cannot start a call even if signals are present.

However, the because the fading for uplink channels and downlink channels is

not totally the same and the other factors such as the difference of the

performances of receivers are present, the calculated uplink and downlink are

not absolute, but the there a fluctuation of 2 to 3 dB.

The measurement report on uplinks and downlinks at the Abis interface can tell

whether the uplink and downlink reach a balance. In addition, dialing tests in

actual network can also tell whether the balance between uplinks and downlinks

are reached. If the conversation quality on downlinks uplinks becomes poor

simultaneously, it means that the downlinks and uplinks are balance.

Note:

Some carriers provide the traffic statistics on uplink and downlink measurement,

which can also tell whether the balance between uplinks and downlinks are

reached.

I. Link budget model

Figure 5-5 shows the link budget model.

Figure 5-5 Link budget model

When calculating uplink and downlink balance, you must consider the functions

of the tower amplifier first. In a base station receiving system, the thermal

movement of the active parts and radio frequency (RF) conductors cause

thermal noise, which reduces the signal-to-noise ratio of the receiving system. In

this case, the receiving sensitivity of the base station is restricted and the



conversation quality is reduced. To improve the receiving performance of the

base station, you can add a low-noise amplifier under the receiving antenna. And

this is the principle of the tower amplifier.

The contributions of the tower amplifier to uplinks and downlinks are judged

according to the performance of its low-noise amplifier and gain. In fact, it is the

tower amplifier that reduces the noise coefficient of the base station receiving

system. The power amplifier can improve the coefficients for the uplink receiving

system (start from the output end of the receiving antenna). However, if the

functions of the tower amplifier are quantified by this, the uplink improved value

can be represented by the NFDelta (it is the reduced value of the noise coefficient

of the receiving system) after a tower amplifier is added to the system.

(1) No tower amplifier

When there is no tower amplifier, the sensitivity of the equipments at the

duplexer input interface at the top of the base station cabinet are taken as a

reference.

For downlink signals, if,

Mobile station receiver output power = Poutm

Base station diversity received gain = Gdb

Base station receiving level = Pinb

Base station side noise deterioration = Pbn

Antenna receiving gain = antenna transmitting gain (according to reciprocity

theorem)

The following equation can be obtained:

Pinb + Mf = Poutm + Gam – Ld + Gab + Gdb – Lfb – Pbn

Generally, Pmn is almost equal to Pbn, so the following equation can be

obtained:

Poutb = Poutm + Gdb + (Pinm – Pinb) + Lcb

(2) With tower amplifier

If a tower amplifier is present, the improved value of the noise coefficients of the

uplink receiving system can be represented by NFDelta, so the equation Poutb =

Poutm + Gdb + (Pinm – Pinb) + Lcb can be developed into the following

equation:

Poutb = Poutm + Gdb + (Pinm - Pinb) + Lcb + NFDelta

The two equations, Poutb = Poutm + Gdb + (Pinm – Pinb) + Lcb and Poutb =

Poutm + Gdb + (Pinm - Pinb) + Lcb + NFDelta are used to calculate base station

transmit power when the uplinks and downlinks are balance. Here,

Pinb is the base station receiving sensitivity

Pinm is the mobile station receiving sensitivity



Gdb (antenna diversity receiving gain) is 3.5dB

According to the requirements in protocols GSM05.05, the mobile station

transmit power and the reference receiving sensitivity of the mobile station and

base station are specified in Table 5-1. At present, however, the sensitivities in

actual systems are greater than the reference values listed in the following table.

Table 5-1 Base station transmit power and reference receiving sensitivity of

mobile station and base station

Network type Mobile station

transmit power

Reference

receiving sensitivity

of mobile station

(dBm)

Reference receiving

sensitivity of base

station (dBm)

GSM 900MHz 2W (33dBm) -102 -104

GSM

1800MHz

1W (30dBm) -100 -104

Note:

From September, 1999 on, the reference receiving sensitivity of mobile station

is -102 dBm as required in GSM protocols. Considering the compatibility of the

previous mobile stations, we adopt -100dBm as the receiving sensibility of the

1800 MHz mobile stations.

II. Bass station sensitivity

This section further introduces the base station sensitivity and the functions of

the tower amplifier.

Receiver sensitivity refers to the minimum signal level needed to by the input end

of the receiver when the certain bit error rate (BER) is met. The receiver

sensitivity detects the performances of the following components:

Receiver analog RF circuit

Intermediate frequency circuit and demodulation

Decoder circuit

Three parameters are used to measure the receiver bit error performance. They

are frame expurgation rate (FER), residual bit error rate (RBER), and bit error

rate (BER). When a fault is detected in a frame, this frame is defined as deleted

one.

Here,

FER indicates the ratio of the deleted frames to the total received frames.

For full rate voice channels, the FER is present when the 3-bit cyclic



redundancy check (CRC) detects errors or bad error indication (BFI) is

caused. For signaling channels, the FER is present when the fire code

(FIRE) or other packet codes detect errors. The FER is not defined in data

services.

FBER indicates the BER that are not announced as deleted frames, namely,

it is the ratio of the bit errors in the frame detected as “good” to the total

number of bits transmitted in “good” frames.

BER indicates the ratio of the received error bits to all transmitted bits.

Because BER occurs at random, the statistical measurement is mainly applied to

measure receiver error rate. That is, sample multiple measuring points on each

channel and when the number of measuring points is certain, if the BER of each

measurement is within the required limit, the BER of this channel meets the BER

as required.

However, the number of sampled measured points and the limit value of the BER

must meet the following conditions:

For each independent sampled measuring point, the times for it to pass a

“bad” unit must be as fewer as possible, that is, the probability must be

smaller than 2%.

For each independent sampled measuring point, the times for it to pass a

“good” unit must be as more as possible, that is, the probability must be

greater than 99.7%.

The measurement has vivid statistical features.

The measuring time must be reduced to the minimum.

As a result, you can measure the receiver sensitivity through measuring whether

the receiver BER has reached the requirement while entering sensitivity level to

the receiver.

Enter the reference sensitivity level to the receiver according to Table 5-1 in

various propagation environments. For the data produced after receiver

demodulation and channel decoding, the indexes for FER, RBER, and BER are

more favorable that that defined in Table 5-2.

Table 5-2 Requirements on static and multi-path reference sensitivity

Requirement on receiver

sensitivity

Propagation condition

Static TU50 TU50 RA250 HT100

Channel type Parameter

No

frequency

hopping

No

frequency

hopping

Frequency

hopping is

present

No

frequency

hopping

No

frequency

hopping

FACCH/H (FER) 0.1% 6.9% 6.9% 5.7% 10.0%

FACCH/F (FER) 0.1% 8.0% 3.8% 3.4% 6.3%



SDCCH (FER) 0.1% 13% 8% 8% 12%

RACH (FER) 0.5% 13% 13% 12% 13%

SCH (FER) 1% 16% 16% 15% 16%

TCH/F9.6&H4.8 (BER) 10–5 0.5% 0.4% 0.1% 0.7%

TCH/F4.8 (BER) – 10–4 10–4 10–4 10–4

TCH/F2.4 (BER) – 2 10–4 10–5 10–5 10–5

TCH/H2.4 (BER) – 2 10–4 10–4 10–4 10–4

TCH/FS (FER) 0.1/a% 6a% 3a% 3a% 7a%

Class Ib.

(RBER)0.4/a% 0.4/a% 0.3/a% 0.2/a% 0.5/a%

Class II

(RBER)2% 8% 8% 7% 9%

Note:

The requirements on BCCH, AGCH, PCH, and SACCH are the same as that on

SDCCH.

The value of “a” in this table depends on the channels. It is 1 for base stations, and 1 to

1.6 for mobile stations.

III. Contributions of tower amplifier to base staiton sensitivity

In terms of technical principles, the tower amplifier reduces the noise coefficients

of the base station receiving system, which is helpful for improving the sensitivity

of the base station receiving system.

In an actual system, to improve the receiving performance of the base station,

you can add a low-noise amplifier near the feeder of the receiving antenna.

In a mobile communication system, the receiver sensitivity = noise spectrum

intensity (dBm/Hz) + bandwidth (dBHz) + noise coefficient (dB) + C/I (dB).

Here the noise spectrum intensity, bandwidth, and noise coefficient are system

thermal noise. C/I is the signal-to-noise ratio required at the Um interface. In a

narrow band system, C/I indicates the modulation performance required by the

receiver baseband, and it is a positive number.

In a spreading communication system, because spread spectrum gain is

present, the value of C/I is far beyond the requirement of the modulation

performance of the receiver baseband, and it is a negative number.



When there are n* cascaded receivers, the equivalent noise coefficient is as

follows:

Here,

Gn indicates the receivers gain at each level (including the loss at each

level).

Fn indicates the noise coefficient of the receivers at each level.

The noise coefficient of the passive device is equal to its loss, and the gain of the

passive device is the reciprocal of the loss.

According to the previous equation, the noise coefficient of the cascading system

is determined by the receivers at the first level.

It must be pointed out that the linear values of the parameters must be applied in

the previous equation, so the “F” is a linear value, which must be converted into

a logarithm. Moreover, according to this equation, the noise the cascaded

receivers are determined by the noise coefficient (F1) of the receivers at the first

level.

However, when the tower amplifier stops working, because the loss is present on

duplexer and bypass connectors, about 2dB of redundant loss is introduced on

reverse link.

According to the equation , the

following two assumptions conclude the regularity of the effect of tower amplifier

on the base station system.

(1) Assumption 1

Hereunder is a series of assumptions:

F1 = 2.5 dB (1.7783), noise coefficient of the tower amplifier

F2 = 4.5 dB (2.8184), noise coefficient of the base station

G = 2 (15.849) dB, tower amplifier gain

Loss of the feeder and other passive devices = 3 dB (2)

Gain of the feeder and other passive devices G0 = –3 dB (1/2)

Noise coefficient of the feeder and other passive devices F0 = 1/G0

When the tower amplifier is not added, the noise coefficient of the base station

receiving system with the antenna output end as reference point is as follows:

F = F0 + (F2–1)/G0 = 10*log (2 + (2.8184–1)/0.5) =7.5dB



When the tower amplifier is added, the noise coefficient of the base station


F = F1 + (F0 – 1)/G + (F2 – 1)/(G*G0) = 10*log(1.7783 + (2 – 1)/15.849 +

(2.8184 – 1)/(15.849 × 0.5) = 3.2dB

At this time, the added tower amplifier improves the noise coefficient, and FDelta is

4.3dB, that is, the uplink is improved by 4.3 dB.

(2) Assumption 2


F1 = 2.2 dB (1.6596), noise coefficient of the tower amplifier

F2 =2.3 dB (1.6982), noise coefficient of the base station

G = 12 (15.849) dB, tower amplifier gain

Loss of the feeder and other passive devices = 3 dB (2)

Gain of the feeder and other passive devices G0 = –3 dB (1/2)

Noise coefficient of the feeder and other passive devices F0 = 1/G0

When the tower amplifier is not added, the noise coefficient of the base station


F = F0 + (F2 – 1)/G0 = 10*log (2 + (1.6982 – 1)/0.5) = 5.3dB

When the tower amplifier is added, the noise coefficient of the base station


F = F1 + (F0 – 1)/G + (F2 – 1)/(G*G0) = 10*log(1.6596+(2 – 1)/15.849 + (1.6982

– 1)/(15.849 × 0.5)) = 2.6dB

At this time, the added tower amplifier improves the noise coefficient, and FDelta is

2.7 dB, that is, the uplink is improved by 2.7 dB.

According to the previous calculation, the following conclusions can be obtained:

The tower amplifier improves the noise coefficient of the base station

receiving system, thus improving the receiving sensitivity of the base

station.

The tower amplifier improves uplink signals effectively, which is also helpful

for improving the receiving sensitivity of the base station.

The gain of the antenna amplifier reduces the effect of the components

installed behind the tower amplifier against noise coefficient.

When the feeder is long and the loss of the feeder is great, if the tower

amplifier is added, the noise coefficient of the base station receiving system

and the uplink signals will be greatly improved.

The smaller the noise coefficient of the tower amplifier is, if the tower

amplifier is added, the greater the noise coefficient of the base station

receiving system is improved. However, if the noise coefficient of the tower



amplifier is too great, it may cause the noise coefficient of the base station

receiving system to deteriorate.

When the receiving sensitivity of the base station is great and the feeder is

short, the tower amplifier makes a little improvement on the noise coefficient

of the base station.

If the tower amplifier improves the base station sensitivity, the base station

is more sensitive to outside interference.

5.6.4 Cell Coverage Estimation

In actual project planning, the effective coverage area of a base station largely

depends on the following factors:

Effective base station transmit power

Working band (900MHz or 1800MHz) to be used

Antenna type and location

Power budget

Radio propagation environment

Carriers; coverage requirements

Based on the indexes of QoS for the mobile network and the actual applications,

this section introduces the coverage area of the base station in different

environments theoretically.

Table 5-3 lists the assumptions of the minimum received level required in various

environments.

Table 5-3 Assumptions of the minimum received level required in various

environments

Application

environments

Minimum

received level

(dBm)

Other indexes

The mobile

station works as

the receiver.

The first floor of

the high buildings

in big cities

-70

Mobile station sensitivity: -102 dBm

Fast fading protection: 3dB

Slow fading protection (indoor): 7dB

(the standard deviation is 7dB for

indoors and 8dB for outdoors, the

pass ratio is 90% in coverage areas)

Penetration loss: 18dB

Interference noise: 2dB

Environment noise protection: 2dB



The mobile

station is the

receiver.

In cars.

The first floor of

the general

buildings in urban

areas.

-80




Penetration loss: 10dB



Outdoors. -90






If the following assumptions are present:

The antenna height of GSM 900MHz and GSM 1800MHz base stations are

30 meters.

The sensitivities of the GSM900 MHz 2W (33 dBm) mobile station and GSM

1800MHz 1W (30 dBm) mobile station are -102 dBm and -100 dBm

respectively.

The mobile station height is 1.5 meters and the gain is 0 dB.

When the combiner and divider unit (CDU) is used, the sensitivities of the

900MHz base station and 1800MHz base station are -110dBm and -

108dBm respectively.

The CDU loss is 5.5dB, and the SCU loss is 6.8dB.

The gain of the 65-degree directional antenna is 13dBd for the 900 MHz

mobile station and 16dBd for the 1800MHz mobile station.

The feeder is 50m in length. For 900MHz signals, the feeder loss is

4.03dBm/100m. For 1800MHz signals, the feeder loss is 5.87dB/100m.

In general cities, select Okumura propagation model.

No tower amplifier and the downlinks are restricted according to the

calculation of the uplink and downlink balance.

According to the previous assumptions, the calculated results are as follows:

(1) Outdoor coverage radius of the 900 MHz base station in urban areas

The minimum received level of the mobile station Pmrminminmin 90 dBm. The

coverage radius is calculated according to the maximum TRX transmit power.

The maximum TRX transmit power for the 900 MHz base station Pbt 40 W (46

dBm).

The EIRP of the base station antenna is:

EIRPPbt Lcom Lbf Gab 46 5.5 2.01 13 2.15 53.65 (dBm)



Here,

LCOM indicates the combiner loss

Lbf indicates the feeder loss

Gab indicates the antenna gain of the base station

And the allowed maximum propagation loss is:

Lp EIRP Pmrminminmin 53.65 ( 90) 143.65 (dB)

According to the Okumura propagation model introduces earlier,

Lp 69.55 26.16 lglg f 13.82 lglghb (44.90 6.55 lglghb ) lglgd Ahm

Here,

hb indicates the antenna height of the base station.

hm indicates the antenna height of the mobile station.

“f” = 900 MHz.

Ahm (1.1 lglg f 0.7)hm (1.56 lglg f 0.8) 0.01 (dB)

According to the previous known number, the outdoor coverage radius of the 900

MHz base station in urban areas can be obtained, that is, d = 2.8km.

(2) Coverage radius of the 900 MHz base station in urban buildings

The minimum received level of the mobile station Pmrminminmin 70 (dBm).


Therefore, the coverage radius of the 900 MHz base station in urban buildings

can be obtained, that is, d = 0.75km.

If the previous assumptions are present, this indicates that the 900 MHz base

station can cover the outdoor areas 2.8 km away, but for the subscribers on the

first floor of the buildings 750 m away, the quality of the received signals is not

satisfying.

(3) Coverage radius of the 900 MHz base station in suburban areas



The Okumura propagation model in suburban areas must be modified as follows:

Lp 69.55 26.16 lglg f 13.82 lglghb (44.90 6.55 lglghb ) lglgd

Ahm 2[lglg(f/28)]2 5.4

Therefore, the coverage radius of the 900 MHz base station in urban areas can

be obtained, that is, d = 5.4km, so it is obvious that the coverage radius of the

base station with the same configuration is larger in suburban areas that in urban

areas.



(4) Outdoor coverage radius of the 1800 MHz base station in urban areas

The minimum received level of the mobile station Pmrminminmin 90 (dBm). Because the

maximum transmit power of the 1800 MHz TRX is 40W (46dBm), the coverage

radius is calculated based on this maximum transit power.

EIRPPbt Lcom Lbf Gab 46 5.5 2.93 16 2.15 55.73 (dBm)

Lp EIRP Pmrminminmin 145.73 (dB)

For the 1800 MHz base station, the Okumura propagation model is:

Lp 46.3 33.9 lglg f 13.82 lglghb (44.90 6.55 lglghb ) lglgd Ahm

In addition, f = 1800 MHz and Ahm (1.1 lglg f 0.7)hm (1.56 lglg f 0.8) 0.04 (dB).

According to the previous known number, the outdoor coverage radius of the

1800 MHz base station in urban areas can be obtained, that is, d = 1.7km.

(5) Coverage radius of the 1800 MHz base stations in urban buildings



If the previous assumptions are present, this indicates that the 1800 MHz base

station can cover the outdoor areas 1.7km away, but for the subscribers on the

first floor of the buildings 500m away, the quality of the received signals is not

satisfying.

5.6.5 Base Station Address Planning

I. Overview

When planning base station addresses, first you must estimate the number of

the base stations needed in various coverage areas according to the coverage

distance and the divisions of the coverage areas. For the convenience of

prediction and emulation, you must plan an initial layout the base station

addresses with the help of maps and the estimated results.

II. Planning methods

The base station address can be planned based on standard girds, or it can be

planned from a specific area.

(1) Plan base station address based on standard grids

First you set the base stations in the coverage areas according to the distance of

the standard grids, and then adjust the address layout and project parameters

according to the estimated coverage results to meet the coverage requirement.

After that, continue the planning according to the following instructions:

If a satisfying address layout is obtained, you must analyze the capacity of

the base stations to be planned according to this layout, and determine the



reasonable number of base stations. When designing the capacity, you

must calculate the number of TRXs needs to be configured for each base

station, and then analyze and adjust the configuration of the base station

according to the number of the configured TRXs.

The adjustment of the configuration of the base station is determined by

subscriber distribution. If the number of base stations in some areas does

not meet capacity requirement, another base stations must be added.

(2) Plan base station address based on a specific area

According to this method, you are required to start the planning from the areas

where the subscribers are most densely distributed or the planning work is quite

hard to be performed. As a result, you must fully survey the subscriber

distribution, landforms, and ground objectives within the coverage area to

position the key coverage area where the center base stations should be

planned. And these center base stations function as ensuring the coverage and

capacity in important areas.

After the layout of these center base stations is determined, you can plan other

base station addresses according to coverage and capacity target. And this is

how the final layout of the base station addresses come from. After the overall

solution is determined, the subsequent steps are performed according to the first

planning method.

Note:

The difference of the traffic intensity and the abnormality of the landforms

and ground objectives result in irregularity of the radio coverage. Therefore,

the distance between base stations varies. Generally, this distance is

smaller in the areas where traffic intensity is great. In some hot areas, you

can ensure the system capacity by using micro cells and distributed

antennas to provide multi-layer coverage.

For restrictions from frequency resources are present, you must consider

avoiding interference while ensuring system capacity.

There is no standard available for the layout of the base station addresses.

A good planning solution is selected based on the integrated performance of

the network.

5.6.6 Coverage Prediction

The coverage prediction is to predict the coverage of the network to be

constructed according to the selected base station addresses, designed base



station types, suitable electronic maps, and network planning tools to judge

whether the coverage meet the requirements of the subscribers.

The coverage of a base station is determined by the following factors:

Indexes of QoS

Output power of transmitters

Available sensitivity of receivers

Direction and gain of antennas

Working bands

Propagation environment (such as landforms, city constructions)

Application of diversity reception

If the predicted results of the network coverage fail to meet the requirements,

you can take the following adjusting measures:

When there are subscribers distributing beyond the cell coverage area, but

it is not economical for you to install a base station, you can use a repeater

to ensure the requirement of those subscriber.

When the signals are weak or blind zones are present within the coverage

area, you can consider whether to use micro cells according to actual

conditions.

If a large blank area is present between neighbor cells, you can increase the

antenna height and add base stations according to the principles of cell

splitting.

When the cell coverage area fails to meet the co-channel interference index,

you can adjust the frequency configuration of the cell, adjust base station

addresses, or adjust design of the parameters, such as antenna

specification, antenna height, azimuth angle, tilt angle, and transmit power.

Note:

When taking these adjusting measures, you must consider the mutual effect

between base stations.

5.7 Design of Base Station Address

5.7.1 Address design

Generally, in GSM radio network planning, the base station address is designed

according to the following requirements:

The address must serve to the reasonable cell structure.



Based on the comprehensive analysis of the electronic maps and paper

maps, you can select several candidate addresses from the perspective of

coverage, anti-interference, and traffic balance.

In actual conditions, carriers are required to discuss the selected addresses

with owners. Generally, the addresses must be located within the area 1/4

radius of the cellular base station.

During the early construction stage when only a few base stations are

installed, the base stations must be located in the center of the areas

where subscribers are densely populated.

For the selection of the base station addresses, the priority must be given

to the important areas, such as government offices, airports, train stations,

news center, and great hotels so that good conversation quality can be

assured. Furthermore, overlapped coverage must be avoided in these

areas.

For other coverage areas, the base station addresses are designed

according to standard cellular structures. For the suburban areas,

highroads, and countryside areas, the design of base station addresses

has little relation with cellular structures.

Without affecting the layout of base stations, you can select the

telecommunication buildings and post offices as the base station addresses

so that the facilities, such as the equipment room, power supplier, and iron

tower can be fully utilized.

The direction of antenna major lobe must be in accordance with the area

where the traffic intensity is great. In this case, the signal strength of the

area can be enhanced, so does the conversation quality. Meanwhile, the

direction of the antenna major lobe must be deviated from intra-frequency

cells so that the interference can be controlled efficiently.

In urban areas, it is recommended that the overlapped depth of the

antennas in adjacent sectors cannot excel 10%. In suburban areas and

small towns, the overlapped depth between coverage areas cannot be too

great, and the included angle between sectors must be equal to or higher

than 90°.

In addition, for actual design, you must consider the mapping relationship

between carrier number and cells. Generally, more carriers are configured

for the cells with high intensity.

The azimuth angle must be designed according to not only the traffic

distribution in the areas around the base stations, but also the performance

of the overall network.

Generally, it is recommended to adopt the same azimuth angle for the 3-

sector base stations in urban areas so that the complicated network



planning can be avoided after cell splitting in the future. Moreover, the

antenna major lobe cannot directly point to the straight streets in populated

urban areas, because it can cause cross-coverage.

In the areas connecting urban and suburban areas, and along transport

arteries, you must adjust the azimuth angle according to coverage target.

Generally, the base station address is not considered on the high mountains

in urban and suburban areas. To be more specifically, the high mountains

are those over 200 to 300 meters higher than above the sea-level).

Otherwise, not only strong interference and weak signals may be present

within the coverage area, but also the base stations are hard to be installed

and maintained on high mountains.

New base stations must be installed at the spots where the traffic is

convenient, the power supply is available, and the environment is secure. In

contrast, new base stations must not be installed at the spots near the radio

transmit stations with high power, radar stations, and other equipments

which produces great interference, because the interference-field intensity

cannot be greater than that defined by the base station.

The base station addresses must be far away from forests or woods to keep

the receiving signals from fading.

The transmission between base station controllers must be considered in

the design of the base station address.

When selecting a base station address from high buildings in urban areas,

you can divide the network into several layers with the help of the building

height. The antenna height of major base stations must be a little higher

than the average height of buildings. Generally, the antenna height of the

base stations in populated urban areas ranges from 25 to 30 meters. In

suburban areas (or the antenna points to suburban areas), the antenna

height ranges from 40 to 50 meters.

Along highroads or in mountain areas, the base station address is selected

based on full survey of the landforms. For example, the address can be

determined in an open area or at the turns of the highroads.

When selecting a base station address from the cities characterized by

mountains and hills and from the areas where high buildings are

constructed with metals, you must consider the effect of time dispersion. In

this case, the base station address must near reflected objectives. When

the base station is far away from reflected objectives, you must adjust the

directional antenna to the reverse direction of the reflected objectives.



Caution:

Time dispersion mainly refers to the intra-frequency interference arising from the

time difference between the master signal and other multipath signal arriving at

the receiver in terms of space transmission. According to the requirements in

GSM protocols, the equalizer of the receiver must carry the time window with

16μs (equivalent to 4.8 km). The multipath signal with time difference greater

than 16 μs is regarded as intra-interference signal. In this case, you must

consider whether the level difference between the master signal and multipath

signal meet the carrier-to-interference ratio (C/I), namely, the master signal is 12

dB greater than the multipath signal at least.

5.7.2 Project Parameter Decision

After finishing designing a base station address, you must decide the project

parameters needed for the base station installation. These parameters include:

Latitude and longitude of the location of base station antenna

Antenna height

Directions of the antenna

Antenna gain

Azimuth angle

Tilt angle

Feeder specifications

Transmit power for each cell of the base station

And the previous parameters are decided through field survey.

Before beginning field survey, you must familiarize yourself with the overall

project and collect the materials and tools relative to the project. They are:

All types of project documents

Background information

Information about the existing network

Local map

Configuration lists required in contracts

Relative tools (including digital camera, GPS, compass, ruler, and laptop

computer)

Note:

Make sure that all the materials and tools are usable before setting out.



The following items must be emphasized before field survey:

The GPS must be placed in an open land to position the latitude and

longitude of a base station

Make a detailed record of the surroundings around the base station, such as

the distribution of the buildings, facilities with strong interference, and the

equipments sharing the same base station address.

It is better to record the previous information with a camera.

Prevent the compass from magnetizing, because the magnetization will

cause great deviation during the measurement.

Field survey determines the layout of the base station addresses ultimately. The

field survey for the base station includes optical measurement, spectrum

measurement, and base station address survey. They are specified as follows:

Optical measurement

Measure if a barrier that may reflect electrical waves around the base

station, such as high buildings.

Spectrum measurement

Check if the electromagnetic environments around the base stations are

normal at present or in recent days.

Base station address survey

Check the installation conditions of antenna and equipments, power supply,

and natural environment.

The following sections introduce the design for antenna installation.

I. Environment for antenna installation

The environment for antenna installation can be divided into the environment

near the antenna and the base station. For the environment near the antenna,

you must consider the isolation between antennas and the effect of iron tower

and buildings against the antenna. For the environment near the base station,

you must consider the effect the high buildings within 500 meters against the

base station. However, if the height of the buildings is properly used, you can

obtain the intended coverage area.

If a directional antenna is installed on the wall, the radiation direction of the

antenna is perfectly perpendicular to the wall. If its azimuth angle must be

adjusted, the included angle between the radiation direction and the wall is

required to be greater than 75°. In this case, if the front-to-back ratio of the

antenna is greater than 20 dB, the effect of the signals reflected by the wall in

reverse direction against the signals in the radiation direction is quite slight, as

shown in Figure 5-6.



Figure 5-6 Included angle between antenna and wall

When installing an antenna, you must consider whether large shadows will be

present within the coverage area of the antenna. The shadows are produced

mainly because the base station is surrounded by some huge barriers, such as

high buildings and great mountains. Therefore, the antenna must be installed in

the areas with no such barriers.

When a directional antenna is installed on building roofs, you must prevent the

building edges from barring the radiation of antenna beams. Therefore, to reduce

or ease the shadow, you can install the antenna near building edges.

Because the building roofs are diversified and complicated, if an antenna must

be installed far away from building edges, the antenna must be installed higher

than the roof. In this case, the wind load of the antenna must be considered.

Table 5-1 and Table 5-2 lists the recommended height between antenna and roof

for GSM 900 MHz and GSM 1800 MHz without the consideration of the effect of

the antenna tilt angle.

Table 5-1 Recommended height between antenna and roof for GSM 900 MHz

Distance between antenna and building

edge (m)Height between antenna and roof (m)

0 – 1 0.5

1 – 10 2

10 – 30 3

> 30 3.5

Table 5-2 Recommended height between antenna and roof for GSM 1800 MHz

Distance between antenna and building

edge (m)Height between antenna and roof (m)



0 – 2 0.5

2 – 10 1

> 10 2

II. Antenna isolation in GSM system

To avoid inter-modulation interference, you must leave certain isolation between

the receiver and transmitter of the GSM base station, namely, Tx - Rx: 30 dB and

Tx -Tx: 30 dB. They are applicable to the situation that a GSM 900MHz base

station and a GSM 1800MHz base station share the same address.

The antenna isolation depends on the radiation diagram, space distance, and

gain of the antenna. Generally, the attenuation introduced by the voltage

standing wave ratio (VSWR) is not considered. The antenna isolation is

calculated as follows:

For vertical arrangement, Lv = 28 + 40lg (k/λ) (dB)

For horizontal arrangement, Lv =22 + 20lg (d/λ) – (G1+G2) – (S1 + S2) (dB)

Here,

Lv indicates the required isolation.

λ indicates the length of carrier waves.

k indicates the vertical isolation distance.

d indicates the horizontal isolation distance.

G1 indicates the gains of the transmitter antenna in the maximum radiation

direction, in the unit of dBi.

G2 indicates the gains of the receiver antenna in the maximum radiation

direction, in the unit of dBi.

S1 indicates the levels of the side lobes of the transmitter antenna in the 90°

direction, in the unit of dBp, and it is a negative value relative to the main

beam.

S2 indicates the levels of the side lobes of the receiver antenna in the 90°

direction, in the unit of dBp, and it is a negative value relative to the main

beam.

Table 5-3 lists the values of S for antennas of different types.

Table 5-3 Values of S for various antennas

Antenna type Value of S (dBp)

65°fan-beam antenna -18





Note:

The value of S can be determined according to the directional diagram of the

antenna. When the omni antenna is used, the S is 0.

The followings introduce the requirements on the antenna mount in GSM

900MHz and GSM 1800MHz.

(1) Directional antenna

In one system, the following requirements must be met in terms of isolation:

The horizontal distance between two antennas in the same sector must be

equal to or greater than 0.4m.

The horizontal distance between two antennas in different sectors must be

equal to or greater than 0.5m.

In different systems, the following requirements must be met when two antennas

are in the same sector and direction:

The horizontal distance between the two antennas must be equal to or

greater than 1m.

The vertical distance between the two antennas must be equal to or greater

than 0.5m.

The distance between the bottom of the antennas and the enclosing wall of

building roof must be equal to or greater than 0.5m.

The included angle between the line connecting the bottom of the antenna

to the antenna-facing roof and the horizontal direction must be greater than

15°.

In addition, the included angle between the line connecting the two antenna

mounts and the antenna direction are required in Table 5-4.

Table 5-4 Range of the included angle between the line connecting two antenna

mounts and antenna direction

Antenna lobe width in horizontal plane (degree) 60-70 90 90

Included angle between mount-connecting line

and antenna direction (degree)> 40-50 > 55 > 70

(2) Omni antenna

The antenna separation for omni antennas is required as follows:

The horizontal distance between antennas must be equal to or greater than

10m or the vertical distance between antennas.



The vertical distance between the antennas must be equal to or greater

than 0.5m.

The distance between the bottom of the antennas and the enclosing wall of

building roof must be equal to or greater than 0.5m.

III. Anrenna isolation of GSM and CDMA base station

The analysis of the interference in CDMA and GSM systems must be based on

the frequency relationship and the transmitting and receiving features of the two

systems. Three types of interference are present, namely, spurious interference,

congestion interference and cross-modulation interference, among which the

spurious interference affects the system most. Therefore, the spurious

interference is a key concern in network design. Compared with the spurious

interference, the cross-modulation interference and congestion interference has

little effect on the network, so they are not introduced hereunder.

The followings describe the spurious interference of the CDMA2000 1X against

the GSM 900MHz.

Currently, bands of China Unicom’s CDMA2000 1X and that of the GSM

900MHz are listed in Table 5-5

Table 5-5 Bands of China Unicom’s CDMA2000 1X and that of GSM 900MHz

System BTS transmitting band (MHz) BTS receiving band (MHz)

GSM 900MHz 945-960 890-915

CDMA 870-880 835-835

As listed in Table 5-5, the bands of the two systems are close to each other, the

interference against each other will easily occur. Mostly, the transmission of

CDMA2000 1X base station will interfere with the reception of GSM 900MHz

base station.

The disclosure signals of the CDMA band falling into the channels of the GSM

base station receivers will enhance the noise level of the GSM receivers. In this

case, the GSM uplinks become weak, which will reduce the coverage area of the

base station and worsen the quality of the network.

If there is not enough isolation between base stations or the transmitting filter

interfering base stations does not provide enough out-of-band attenuation, the

signals falling into the band of the interfered base station receiver may strong,

which will increase the noise level of the receiver.

The deterioration of the system performance is closely related to the strength of

interference signals, and the strength of interference signals is determined by the



factors, such as the performance of the transmitting elements of the interfering

base stations, the performance of the receiving elements of the interfered base

stations, the distance between bands, and the distance between antennas.

Figure 5-7 shows an interference model.

Figure 5-7 Interference model diagram

According to Figure 5-7, the signal from the amplifier of the interfering base

station is first sent to the transmitting filter, and then it attenuate due to the

isolation between the two base stations. Finally, it is received by the receiver of

the interfered base station. The power of the spurious interference arriving at the

antenna end of the interfered base station can be expressed by the following

equation:

Ib＝PTX AMP－Pattenuation－Iisolation＋10 lglgWBint erferferf ered

WB int erferferf ering

Here,

Ib indicates the interference level received at the antenna receiving end of

the interfered base station, in the unit of dBm.

PTX-AMP indicates the output power at the amplifier of the interfering base

station, in the unit of dBm.

Pattenuation indicates the out-of-band suppression attenuation at the

transmitting filer.

Iisolation indicates the isolation between the antennas of the two base stations,

in the unit of dB.

WBinterfered indicates the bandwidth of the signals at the interfered base

station.

WBinterfering indicates the measurable bandwidth of the interfering signals, or it

can be understood as the bandwidth defined by spurious radiation.

Regulate the previous equation and the following equation can be obtained:



Iisolation＝PTX AMP－Pattenuation－Ib＋10 lglgWBint erferferf ered

WB int erferferf ering

Suppose the transmit channel number of CDMA2000 1X is the last one on its

working band, that is, 878.49MHz, the spurious signal level on the band of 890-

915MHz must be equal to or lower than -13dBm/100kHz. If you intend to put this

assumption into practice, you can filter and combine each transmitted channel

number by using band-limited filter with a bandwidth of only 1.23MHz. The band-

limited filter of this type has great out-of-band attenuation, which can reach 56 dB at 890

MHz and 80 dB at 909 MHz. Here you must consider the worst situation, that is,

the frequencies at the highest end of the CDMA system interfere with the

frequencies at the lowest end of the GSM system.

In this case, Iisolation = (-13dBm/100kHz) - 56 - Ib + 10lg (200kHz/100kHz)

Here Ib indicates the highest interference level (dBm) allowed by the receiving

end of the interfered base station. If the receiving sensitivity of the interfered

base station is ensured, the outside interference level are required to be 10 dB

lower than the back noise of the receiver. In this case, the sensitivity affected

only accounts to about 0.5 dB.

The back noise of the GSM receiver is the sum of the noise intensity, bandwidth,

and noise coefficient. If the noise coefficient is 8 dB, the back noise is -

174+noise coefficient+10lg (200000) = -174+8+53 = -113 (dBm). Therefore, the

maximum spurious interference allowed is -113-10 = -123 (dBm/200kHz).

As a result, the spurious interferences from other systems falling at the GSM

receivers are required to be smaller than -123 (dBm/200kHz); otherwise, the

spurious interferences will seriously affect the GSM system.

Therefore, Iisolation = (-13dBm/100kHz) – 56 - Ib + 10lg (200kHz/100kHz) = -13- 56-

(-123dBm/200kHz) + 10lg (200kHz/100kHz) = 57 dBm/200kHz.

That is, according to the assumption, the isolation between a CDMA antenna and

GSM 900MHz antenna must be at least 57dB regardless whether they share the

address or not.

Many ways can be used to reduce the interference. For example, you can adopt

the following ways:

Design enough distance between antennas

Filter the out-of-band interference of the transmitter

Add different equipments to the filter, such as receiver, duplexer, and

divider.

According to the requirements in TIA/EIA-97 protocols, the spurious interference

from the CDMA antenna interface falling within the GSM 900MHz receiving

bands must be less than -13 dBm/100kHz. Therefore, the problems, such as

mutual interference and co-address construction must be considered in the initial

design.



To be specific, you can filter and combine each transmitted channel number

using a limited-band filter with the bandwidth of only 1.23 MHz. The band-limited

filter of this type has great out-of-band attenuation, thus the space distance

between the antennas of the CDMA system and GSM system must be

shortened.

In addition, to minimize the interference, you must keep suitable isolation

between the antennas of the CDMA system and GSM system.

The antenna isolation is calculated according to the following two formulas,

which has been introduced earlier:

For vertical arrangement, Lv = 28 + 40lg (k/λ) (dB)

For horizontal arrangement, Lv =22 + 20lg (d/λ) – (G1+G2) – (S1 + S2) (dB)

According to the two formulas, the requirements on the isolation between the

antennas of CDMA system and GSM 900 MHz system are specified in the

following three circumstances.

The antennas of the CDAM system and GSM 900MHz system do not share

the same address, with the antennas horizontally opposite to each other, or

the antennas of the two systems share the same address, with the antenna

type of omni antenna.

Suppose the effective gains of the antennas of the two systems in the

maximum radiation direction are 10 dBi (with the feeder loss considered),

and the interference signals are 890MHz, according to previous analysis,

the isolation between the CDMA system and GSM system is required at

least 57dB.

Therefore, the following equation can be obtained according to the previous

formula:

57 = 22 + 20lg (Dh/λ) – (10 + 10)

And the horizontal distance between the two antennas is d = 190m.

Table 5-1 lists the isolation requirements between omni antennas of the two

systems.

Table 5-1 Isolation requirements between omni antennas of CDMA system

and GSM 900MHz system

Effective antenna gain in

radiation direction (dBi)

Antenna isolation

requirement (Db)

Antenna distance

requirement (m)

10 57 190

10 57 599



The antennas of the CDMA and GSM 900 MHz system share the same

address (the antennas are installed on the same platform and horizontally

separated), with the antenna type of directional antenna.

Suppose that the two antennas are horizontally placed, and their tilt angle is

65°, and that the effective gains of the two antennas in the radiation

direction are 15dBi.

And if the side lobe of the 65°antenna is -18dB in the horizontal plane, the

effective gain of the antenna in this direction is (15 – 18) dBi = -3 dBi.

Therefore, 57=222+0lg (Dh/λ) - {(15+15) + [(-18) + (-18)]}.

According to the previous equation, the horizontal distance between the two

antennas are d = 9.5m.

Table 5-2 lists the isolation requirements between directional antennas of

CDMA and GSM 900 MHz systems.

Table 5-2 Isolation requirements between directional antennas of CDMA

and GSM 900 MHz systems

Effective antenna gain in

radiation direction (dBi)

Antenna isolation

requirement (Db)

Antenna distance

requirement (m)

10 57 190

15 57 599

The antennas of the CDMA and GSM 900 MHz antennas share the same

address (the antennas are not installed on the same platforms of the iron

tower and vertically separated), with the antenna types of directional

antenna and omni antenna.

In this case, the equation 57=28 + 40 lg (k/λ) is present.

According to this equation, the vertical distance between the two antennas is

d = 1.8m.

Note:

The previous descriptions are just theoretical detections. In actual networking,

other types of antennas may be installed at the same address. In this case,

some equipment indexes must be considered, among which the important ones

are spurious radiation, the interference power of the interfering signals to

interfered signals, and the antenna isolation.



IV. Installation distance between antennas

Diversity technology is the most anti-fading effective. When two signals are

irrelevant to each other, the horizontal distance between the diversity antennas

must be 0.11 times that of the valid antenna height. The higher place the

antenna is installed, the larger the horizontal distance between diversity

antennas is. When the distance between diversity antennas is equal to or greater

than 6m, however, the antenna is hard to be installed on an iron tower.

In addition, the distance required by vertical diversity antennas is 5 to 6 times

that of the horizontal diversity antennas when the same coverage is ensured.

Therefore, the vertical diversity antenna is seldom used in actual projects, but

antennas are often vertically installed to meet isolation requirement, especially

omni antennas are vertically installed.

In addition, for highroad coverage, the line connecting two receiving antennas

must be perpendicular to the highroad. If space diversity is used, the diversity

distance is the perpendicular, as shown in Figure 5-8.

Figure 5-8 Space diversity distance of directional antennas

Table 5-1 and Table 5-2 lists the required distance between GSM antennas

(suppose no barrier is present between the antennas)

Table 5-1 Required diversity distance between omni antennas

Isolation requirement: Tx-Tx, Tx - Rx: 30 dB

Vertical distance

(recommended)Horizontal distance Remarks

GSM 900MHz:

Tx-Tx, Tx - Rx≥ 0.5m Gain = 10 dBi: 8m

Distance between

antenna and tower:

2m

GSM

1800MHz: Tx-

Tx, Tx - Rx

≥ 0.25m Gain = 10 dBi: 4m

Distance between

antenna and tower:

2m



GSM 900MHz

+ GSM

1800MHZ: Tx-

Tx, Tx - Rx

≥ 0.5m Gain = 10 dBi: 1m

Distance between

antenna and tower:

2m

Diversity requirement

GSM 900MHz:

Tx-Tx, Tx - Rx–

≥ 4m (recommend

6m)

Distance between

antenna and tower:

2m

GSM

1800MHz: Tx-

Tx, Tx - Rx

–≥ 2m (recommend

3m)

Distance between

antenna and tower:

2m

Table 5-2 Required diversity distance between directional antennas

Isolation requirement: Tx-Tx, Tx - Rx: 30 dB

Same sector

antennas

Vertical distance

(recommended)Horizontal distance Remarks

GSM 900MHz:

Tx-Tx, Tx - Rx≥ 0.5m

For 65 antennas,

antenna gain: 15

dBi: 0.4m

No effect from

tower structure in

forward direction

of the antenna

GSM

1800MHz: Tx-

Tx, Tx - Rx

≥ 0.25m

For 65 antennas,

antenna gain: 15

dBi: 0.2m

No effect from

tower structure in

forward direction

of the antenna

Adjacent-sector

antennas (on

the same

platform)

Vertical distance Horizontal distance Remarks

GSM 900MHz:

Tx-Tx, Tx - Rx– ≥ 0.5m –

GSM

1800MHz: Tx-

Tx, Tx - Rx

– ≥ 0.5m –

Diversity requirement



GSM 900MHz:

Tx-Tx, Tx - Rx–

≥ 4m (recommend

6m)

No effect from

tower structure in

forward direction

of the antenna

GSM

1800MHz: Tx-

Tx, Tx - Rx

–≥ 2m (recommend

3m)

No effect from

tower structure in

forward direction

of the antenna

Note:

The installation for GSM 900MHz and GSM 1800MHz antennas is flexible, but

no matter what specifications are used, they must meet the requirements on

isolation and distance. In addition, in actual projects, barriers are present

between antennas. For example, a tower is always present between two omni

antennas, so you must shorten the horizontal distance between them.

V. Design of base station parameters in residential areas

A large number of residential areas are distributed in urban areas, so this section

introduces the design of base station parameters in these areas.

(1) Features of residential areas

Residential areas in urban areas are characterized by regular arrangement of

buildings, and they can be divided into the following types as listed in Table 5-3.

Table 5-3 Division of residential areas

In terms of Description

Building height

High-building residential areas: above 10 floors (30 meters)

Multi-floor residential areas: 5 to 8 floors (15 -30 meters)

Villas and low residential areas: less than 4 floors (12 meters)

Building

intensity

Great-intensity residential areas: the distance between

buildings is within 10 meters.

Middle-intensity residential areas: the distance between

buildings ranges from 10 to 20 meters.

Low-intensity residential areas: the distance between

buildings is larger than 20 meters.

Construction

material

The walls of the residential areas are constructed with

concretes.



The walls of the residential areas are constructed with bricks

and concretes.

The walls of the residential areas are constructed with hollow

blocks.

Notes:

The thickness of the buildings varies with the regions and

climates. Three specifications are available, namely, 24m,

47m, and 49m. Generally, the walls are thicker in southern

parts and thinner in northern parts.

(2) Antenna installation in residential areas

The address where the antenna should be installed in residential areas is hard to

be determined. Generally, when adopting micro cells, you can install the antenna

within a residential area near to the target coverage area.

In this case, the antenna can be installed in the following spots:

On outer walls (not roofs) of a building

On pillars

Install a micro cell in underground garages

For the residential areas large in size and regular in arrangement, the antenna

can be installed as shown in Figure 5-9.

Figure 5-9 Installed position of micro cell antennas

To realize better stereo coverage, you can install the antenna at wall corners

with enough height, namely, 1/2Hbuilding Hantenna 3/4Hbuilding. In this case, the

azimuth angle of the antenna must be designed as shown in Figure 5-10.




If the antenna is installed at a wall corner, the major lobe of the antenna can

radiate the space between buildings. Generally, the major lobe of the antenna

cannot face the walls of the buildings nearby directly.

If frequencies are reusable among these micro cells, the directions of antennas

must be consistent with each other. In addition, you can also use the cell splitter

to enable a cell to coverage the areas in two directions, as shown in Figure 5-11.

In this case, however, the frequency utilization ratio may decrease and extra

power splitter will introduce loss of 3 dB.

For the residential areas with regular arrangement, the directional antennas

whose horizontal beam width is 90° to 120° and vertical beam width is greater

than 30° are recommended.

Under certain conditions, the micro cell antenna can be installed on the pillars

within a residential area, as shown in Figure 5-11.


For the residential areas with irregular arrangement, the antenna can be installed

on the walls of a building, so the reflected waves can coverage the walls of

opposite buildings, as shown in Figure 5-12. In this case, the antennas whose

horizontal beam width is greater than 120°and vertical beam width is greater

than 30°are recommended.




(3) Antenna selection

When the walls of a building is selected as an installed position, you can use the

build-in antenna of the micro cell directly, or other antennas with small size.

According to coverage features of residential areas, when selecting the

specifications for the micro cell antennas to be used, you must consider the

following factors:

Antenna gain

Horizontal beam width

Vertical beam width

Polarization mode

Visual effect (antenna size, shape, and weight)

The antenna gain is recommended less than 9 dBi for micro cell antennas.

Because the coverage area of a micro cell antenna is small and the installed

position is near to the coverage area, the antenna gain can be adjusted to a

smaller value, especially if the gain of an antenna is greater than 10dBi, its size

is large, which may cause opposition from residents.

The selection of the horizontal and vertical beam width for an antenna is related

to radio environment. If a micro cell antenna is installed on a wall, the antenna

height is lower than the average height of surrounded buildings. In this case, if

both the indoor coverage of lower floors and higher floors can be assured, you

must select the antennas with greater vertical beam width. According to the

height of buildings, you can select the directional antennas whose vertical beam

width ranges from 35°to 80°.

The selection of the horizontal beam width of the micro cell antenna and the

installed position of the antenna are related to coverage target. In this case, you

can select the directional antennas whose beam width ranges from 60° to 150°,

or you can choose omni antennas or bi-directional antennas (8-shaped

antennas).

Both vertical polarization antennas and dual polarization antennas can be

selected for a micro cell. The coverage area of a micro cell in urban areas is

small, so the diversity reception is unnecessary. In this case, a vertical

polarization antenna can meet the coverage requirements in residential areas.

As for the dual polarization antenna, however, it is expensive and large in size,

so it is not recommended.

The visual effect must be emphasized for the micro cell antennas installed in

residential areas. They must be small and moderate. In addition, they must be

light for installation convenience. If the contract between the color of the antenna



and that of the surrounded buildings is great, you must color the antenna with the

same color of the buildings.

Note:

In some cases, you should consider adopting dual-band antennas. When

selecting a small-sized antenna, you should consider whether its maximum

output power can bear the micro cell output power. When adopting short jumpers

instead of 7/8 feeders, you should consider whether the antenna connector (N-

shaped male/female, 7/16 DIN header) matches the jumper connector.

5.8 Location Area Design

5.8.1 Definition of Location Area

In GSM protocols, a mobile communication network is divided into multiple

service areas according to the codes of location areas. Thus the network pages

a mobile subscriber through paging its location area.

Location area is the basic unit of paging areas in a GSM system. That is, the

paging message of a subscriber is sent in all cells of a location area. A location

area contains one or more BSCs, but it belongs to one MSC only.

Figure 5-13 shows the division of service areas.

Figure 5-13 Division of service areas

5.8.2 Division of location areas

The coverage area of each GSM PLMN is divided into multiple location areas, in

which an MS is positioned. The size of a location area, namely, the area covered



by a location area code (LAC), plays a key role in a GSM system. Therefore, this

section mainly introduces the principle for planning location areas.

I. Dividing the location area according to the distribution and behaviour

of mobile subscribers

The distribution of location areas in cities and suburbs is different. Generally,

suburban areas or counties occupy independent location areas. In cities, the

distribution of location areas is similar to a concentric circle. (The areas in the

internal circle can be divided into several location areas due to the requirements

on capacity. The concentric circle can be divided into several fragments.)

Practice has proved that if the location areas are divided according to the

previous methods, as shown in Figure 5-14, both coverage and call-connected

ration can be improved.

Figure 5-14 Division of LAs

In addition, if two or more location areas are present simultaneously in a big city

of great traffic, the landforms, such as mountains and rivers within this city can

be used as edges of the location areas. In this case, the overlapped depth

between the cells of the two location areas can be reduced. If no such landforms

available within this city, the areas (such as streets and shopping centers) with

great traffic cannot be used as edges of the location areas.

Generally, the edge of a location area is oblique instead of parallel or

perpendicular to streets. In the intersected areas of urban areas and suburban

areas, to avoid frequent location update, you must design the edges of location

areas near the outer base stations instead of the base stations just installed at

the intersections.

II. Calculating coverage area and capacity of a location area

If the coverage area of a location area is too small, the mobile station will

perform frequent location update. In this case, the signaling flow in the system



will increase. If the coverage of a location area is too larger, however, the

network will send a paging message in multiple cells until the mobile station is

paged. In this case, the PCH will be overloaded and the signaling flow at the Abis

interface will increase.

The calculation of location areas varies with the paging strategies designed by

different carriers. During early network construction stage, the traffic is not great,

so a location area can accommodate more TRXs. However, it is still necessary

for you to monitor the PCH load and traffic growth. When the traffic grows great,

you can enhance the PCH capacity by adding a BCCH to the system, but the

number of voice channels can be added is reduced by one accordingly.

Generally, the capacity of a location area is calculated as follows:

The number of paging blocks sent in each second × the number of paging

messages sent in each paging block = the maximum paging times in each

second. As a result, the number of paging times in each hour, the traffic allowed

in each location area, and the number of carriers supported in each location area

can be deducted.

The followings introduce the items present in the previous paragraph

respectively.

(1) The number of paging blocks sent in each second

1 frame = 4.61ms, 1 multiframe = 51 frames = 0.2354s; suppose the number of

access grant blocks is AGB, the number of blocks, the number of paging blocks

sent in each second is calculated by the following formulas:

For non-combined BCCH, the number of paging blocks sent in each second

= (9 – AGB)/0.2345 (paging block/second).

For combined BCCH, the number of paging blocks sent in each second = (3

– AGB)/0.2345 (paging block/second).

For non-combined BCCH, the AGB is 2 according to Huawei BSC. Therefore, the

number of paging blocks sent in each second is 29.7 (paging block/second);

when AGB is 0, it is 38.2 (paging block/second).

For combined-BCCH, the AGB is 1, so the number of paging blocks sent in each

second is 8.5 (paging blocks/second); when the AGB is 0, it is 12.7 (paging

block/second).

According to the previous analysis, the larger the number of AGB, the smaller the

number of the paging blocks sent in each second and the smaller the paging

capacity is. Moreover, the paging capacity of the combined BCCH is far less than

that of the non-combined BCCH.



Note:

Generally, a combined-BCCH cell and a non-combined-BCCH cell are not

configured simultaneously within a LAC, and the number of AGB must be

consistent with a location area; otherwise the paging capacity of the location

area will decrease (now the paging capacity of the cell with the least paging

capacity is the paging capacity of the location area).

However, if the capacity of a location area is small and the LAC resource is

scarce, you can configure the combined-BCCH cell and non-combined-BCCH

cell within a LAC to enlarge the number of traffic channels for O1 and S111 base

stations.

(2) The number of paging messages sent in each paging block (X)

According to section 9.1.22 of GSM0408 protocols, each paging block has 23

bytes, and can send 2 IMSI pages, or 2 TMSI and 1 IMSI pages, or 4 TMSI

pages.

According to the paging strategies of Huawei MSC, if the IMSI paging

mechanism is adopted, the number of paging messages sent in each paging

blocks is 2 (paging times/paging block); if the TMSI paging mechanism is

adopted, it is 4 (paging times/paging block)

(3) The maximum paging times in each second (P)

The maximum paging times in each second is calculated by the following two

formulas:

For non-combined BCCH, P = (9 – AGB)/0.2345 (paging block/second) ×

(paging times/paging block).

For combined BCCH, P = (3 – AGB)/0.2345 (paging block/second) ×

(paging times/paging blocks).

If the IMSI paging mechanism is adopted, for non-combined BCCH, when AGB =

2, P = 59.47 (paging times/second); when AGB = 0, P = 76.47 (paging

times/second). For combined-BCCH, when AGB = 1, P = 16.99 (paging

times/second); when AGB = 0, P = 25.49 (paging times/second).

If the TMSI paging mechanism is adopted, for combined BCCH, when AGB = 2,

P = 118.95 (paging times/second); when AGB = 0, P = 152.93 (paging

times/second). For combined BCCH, when AGB = 1, P = 33.98 (paging

times/second); when AGB = 0, P = 50.98 (paging times/second).

According to the previous analysis, the paging capacity under IMSI paging

mechanism is half of that under TMSI paging mechanism.

(4) The traffic allowed in each location area (T)



When designing the capacity for a location area, you must be attention that the

paging capacity of a location area cannot break its limit. For network expansion,

you can collect the times of the busy-hour paging orders delivered by BSC from

OMC, and then convert the times into the number of paging orders sent in each

second.

If no traffic measurement data is available, such as in the case of new network

construction, you can calculate the traffic allowed in each location area by

assuming a traffic model.

For example, if the average conversation duration is 60s and the ratio of the

times for the mobile station to be successfully paged to the times of total pages

is 30%, the 60s of conversation duration matches 1/60 calls (in the unit of

second. Erl), and 30% of calls is generated by the called parties. Therefore, the

successful calls of the 30% mobile stations are 0.05 times (that is, 1/60*30% =

0.005), in the unit of second. Erl.

If the 75% of the mobile stations respond to the first page and 25% respond to

the second page, the mobile stations responding to the third page can be

neglected. (It is just an assumption, which may be different from actual

conditions.). Therefore, 1.25 pages are needed if a mobile station is successfully

called each time (25% of the pages must be resent). In this case, the following

equation is present:

Y = 0.005*(1+25%) = 0.00625 paging times/(second. Erl)

Suppose the congestion on paging channels will occur when the paging capacity

is 50% greater than maximum theoretical paging capacity, the original paging

messages are still present even the paging queue is full in the BTS. In this case,

the paging capacity in one second is P*50%.

Therefore, the traffic allowed in each location area can be calculated according

to the formula T = P*50%/Y, and the specific values are listed in Table 5-1.

Table 5-1 Traffic allowed in each location area

Paging

mechanismT (Erl) AGB (block)

BCCH

combination mode

IMSI

4757.86 2Non-combined

BCCH


BCCH

1359.39 1 Combined BCCH




TMSI


BCCH

12234 .49 0Non-combined

BCCH



(5) The number of carriers supported by each location area (NTRX)

Each TRX had 7.2 TCHs in average, so the maximum traffic of each TRX in each

hour is 7.2.

Therefore, the number of carriers supported in each location area can be

calculated according to NTRX = T/7.2 and the specific values are listed in

Table 5-2 Number of carriers supported in each location area (TRX/LA)

Paging

mechanismNTRX (TRX/LA) AGB (block)

BCCH

combination mode

IMSI

660 2Non-combined

BCCH

849 0Non-combined

BCCH

188 1 Combined BCCH

283 0 Combined BCCH

TMSI

1321 2Non-combined

BCCH

1699 0Non-combined

BCCH

377 1 Combined BCCH

566 0 Combined BCCH



Note:

All the previous assumptions do not include the effect of the point-to-point short

messages against on paging capacity. If the conversation times of a subscriber

are equal to the number of the short messages to be sent, and if the sent ratio

and received ratio are consistent with each other, the paging times/second. Erl

will double in busy hour and the capacity of the location area will reduce by half.

Therefore, some common short messages must be sent on CBCH.

5.8.3 Others

This section introduces some other information about location area design.

The capacity of a location area is closely related to paging mechanism, and

is directly related to the combinations of AGB and BCCH. When the

combinations of AGB and BCCH are inconsistent with each other in a

location area, the capacity of the location area is determined by the cell with

the smallest capacity. Therefore, the combinations of AGB and BCCH must

be designed to be consistent in location area planning.

If the number of point-to-point messages grows large immediately, the

number of paging messages will increase, but the number of supported

subscribers will decrease. In this case, you must control and protect the

flows in the system.

Because the traffic density varies with location areas, it is recommended

that the combined-BCCH cells, non-combined-BCCH cells, and multi-BCCH

cells form a location area respectively. When a cell with BCCH/SDCCH

combination, the location area can be as large as possible when the paging

capacity of the BTS does not reach the limit. However, because all paging

messages will be broadcasted in all cells within a location area, the cell with

BCCH/SDCCH combination is the bottleneck of the location area.

The LAC is a kind of number resource. Therefore, you must cooperate with

carries to plan location areas.

5.9 Dual-Band Network Design

5.9.1 Necessity for Constructing Dual-Band Network

The earlier GSM mobile communication network is constructed on the 900 MHz

band. With rapid growth of subscribers, the network capacity also grows rapidly.

Therefore, the lack of frequency resources and radio channels is a major

concern for mobile telecommunications.



Many methods can be used to expand the capacity of a GSM system, including:

Adding macro cell base stations to the system

Reducing distance between base stations

Adopting aggressive frequency reuse technologies (such as MRP and 1×3)

Adding micro cells to the system

Applying half rate to the system

However, all these methods cannot thoroughly solve the problems concerning

network capacity. As a result, the GSM 1800MHz network is introduced (uplink:

1805–1880 MHz; downlink: 1710–1785 MHz). And the network integrating GSM

900MHz and GSM 1800MHz can meet the growth of network capacity.

The application of GSM 1800MHz can bring the following advantages:

It does not occupy the bands of GSM 900MHz and has a communication

bandwidth of 75M. Therefore, it breaks the bottleneck of GSM 900MHz in

terms of frequency resources.

The system networking, project implementation, network planning, and

network maintenance of a GSM 1800MHz network are almost the same with

that of a GSM 900MHz network.

The GSM 1800MHz and GSM 900 MHz can share a base station, so a

GSM 1800MHz network can be finished in a short time, which is quite

helpful for network expansion.

Dual-band mobile phones now accounts for a major part of the total, so a

GSM 1800MHz network can provide services to the dual-band subscribers.

In this case, the capacity pressure on GSM 900MHz can be greatly eased.

5.9.2 GSM 1800MHz Coverage Solutions

I. Propagaiton features of GSM 1800MHz

The propagation features of the electromagnetic waves of 900 MHz and 1800

MHz are different in the following aspects:

The propagation loss in free space

The propagation loss of the 1800 MHz signals is 6 dB greater than that of

the 900 MHz signals in free space.

Penetration loss

The penetration loss of the 900 MHz signals is greater than that of the 1800

MHz signals, but their difference is slight.

Diffraction loss

The longer the waves, the smaller the diffraction loss is. The diffraction

ability of the 1800 MHz signals is poorer than that of the 900 MHz signals.



II. Dual-Band Networking Mode

There are three dual-band networking modes, namely, independent MSC

networking, co-MSC/independent BSC networking, and co-BSC networking,

among which the former two are called independent networking, and the later is

called hybrid networking.

III. Coverage requirements on GSM 1800 MHz

Outdoor coverage

The outdoor coverage can be easily realized when the distance between

base stations are not large. In necessary cases, you can add a GSM

1800MHz base station at the address of the original GSM base station. And

in some places, you should consider add a new base station.

Indoor coverage

To ensure that the indoor coverage of GSM 1800MHz is good, you must

control the distance between the base stations installed in urban areas

within 1000 meters. In China, however, the buildings in most cities are

constructed by concretes and metals, so the penetration loss is great. As

result, the distance between base stations in urban areas of China ranges

from 500 to 800 meters.

IV. Coverage mode of GSM 1800MHz

(1) Scattered coverage in hotspot areas

At the early network construction stage, the GSM 1800MHz base stations are

scattered in hotspot areas. When the capacity configured for a GSM 1800 MHz

base station is small, you must solve the problems, such as SDCCH congestion,

TCH congestion, and frequent update between GSM 1800MHz and GSM

900MHz. The cost in early construction stage is small.

Figure 5-15 shows the scattered coverage of GSM 1800MHz in hotspot areas.

Figure 5-15 Scattered coverage of GSM 1800MHz in hotspot areas



The coverage of the dual-band network of this mode is based on the original

GSM 900MHz network. The GSM 1800MHz base station is constructed in some

hotspot areas, so the seamless coverage of GSM 1800MHz is not available in

this case.

If a dual-band mobile phone starts conversation in an area covered by GSM

1800MHz, after leaving this coverage area, it hands over to the GSM 900MHz

cell where it originally was. And the handover of this type is called the inter-band

handover caused by coverage.

If a dual-band mobile phone starts the conversation in an area covered by GSM

900MHz, but because the traffic in this area is great, the mobile phone will hand

over to an area covered by GSM 1800MHz. And the handover of this type is

called the inter-band handover caused by capacity.

The scattered coverage in hotspot areas only relieves capacity problems in a

short term. Moreover, frequent inter-band frequency handover increase the

signaling load, which results in the loss of system capacity.

(2) Seamless coverage in hotspot areas

If the coverage of this mode is available; the GSM 1800 MHz network can share

greater traffic for GSM 900MHz network and expand the system capacity. In

addition, it is cost-effective.

(3) Perfect seamless coverage

If a GSM 1800MHz network adopts the coverage of this type, the advantages are

as follows:

The seamless coverage area within a city can be realized.

The GSM 1800MHz network can share the traffic load for GSM 900MHz

network as much as possible.

The system capacity can be greatly expanded.

The ratio of the handover between layers is small.

The quality of the network is quite satisfying.

The frequencies can be planned by patch.

The carriers can be expanded step by step.

However, there are still disadvantages. They are as follows:

The number of base stations is large.

The work load of network planning and optimization is huge.

The investment is large.

The base station addresses cannot be decided once.

Figure 5-16 shows the perfect seamless coverage of GSM 1800MHz in hotspot

areas.



Figure 5-16 Perfect coverage of GSM 1800MHz in hotspot areas

If a GSM 1800MHz network adopts this coverage mode, it can be easily

expanded to meet future coverage.

Compared with the scattered coverage in hotspot areas, the perfect seamless

coverage is characterized by great intensity and large area. Therefore, the ratio

of inter-band handover under this coverage mode is far smaller than that under

scattered coverage mode. As a result, the signaling load is reduced greatly.

Therefore, this coverage mode is an ideal coverage solution. If a GSM 1800MHz

network adopts this coverage mode, it does not necessarily attach to the GSM

900MHz network, instead, it can form an independent network.

5.9.3 Location Area Division for Dual-Band Network

The location area division for dual-band network is suggested as follows:

If 1800 MHz cells and 900 MHz cells are under the control of two MSCs

respectively, their location areas are different. Therefore, you must set

related parameters to maintain the mobile stations stay in the 1800 MHz

cells where the traffic is absorbed. In this case, the times for the mobile

station to handover between the two bands and reselect cells will decrease.

Meanwhile, when designing signaling channels, you must fully consider the

load resulted from location update.

If 1800 MHz cells and 900 MHz cells share a MSC, at the early network

construction stage, they are suggested to use the same location area

without affecting the network capacity. If the restriction on paging capacity is

present, two location areas must be divided for them either in terms of band

or geographic location, as shown in Figure 5-17 and Figure 5-18.



Figure 5-17 Location area division based on band

Figure 5-18 Location area division based on geographic location

If the location area is divided in terms of band, because frequent location

updates are resulted from inter-band handover and cell reselection, you must set

related parameters to maintain the mobile stations stay in the 1800 MHz cells

where the traffic is absorbed. In this case, the times for the mobile station to

handover between the two bands and reselect cells will decrease. Meanwhile,

when designing signaling channels, you must fully consider the load resulted

from location update.

If the location is divided in terms of geographic location, the frequent location

updates resulted from inter-band handover and cell reselection can be avoided.

However, you need to modify the related data of the original 900 MHz network. In

addition, at the edges of the location areas, because the location updates

caused by intra-band and inter-band handover and cell reselection is present

simultaneously, the signaling flow is huge at these edges. As a result, you must

carefully design the edges of the location areas.



5.9.4 Traffic Guidance and Control Strategies of Dual-Band Network

I. Traffic guide of Dual-Band Network

At early construction stage of a dual-band network, traffic control concerns how

to use the new GSM 1800MHz network to share the traffic flow for the GSM

900MHz network. According to the original intension of the GSM 1800MHz

network, the traffic can be guided according to the following principles:

25) At the early construction stage of a dual-band network, the GSM 1800MHz

network is mainly applied to absorb the traffic of the dual-band subscribers

so that the load of the GSM 900MHz network can be eased.

26) When the number of dual-band subscriber grows large, each band must

share the traffic so that the inter-band handover times can be reduced.

Figure 5-1 shows the process of traffic guide and control strategies.

Figure 5-1 Process of traffic guide and control strategies

The various traffic control strategies can be realized through adjusting parameter

settings as follows:

1) In idle mode, when the mobile station is selecting cells after it is switched on

and reselecting cells when it is in standby state, you can set higher priorities

for the 1800 MHz cells by designing the system parameters, including CBQ,

CBA, CRO, TO, and PT. In this case, subscribers are more likely to stay in

the 1800 MHz cells. As a result, their calls are established on the 1800 MHz

cells.

2) If traffic congestion is present in the service cell when a mobile station is

setting up a call, the system applies directed retry function to assign the

mobile station to a TCH in the neighbor cells of the service cell and adjust

the traffic allocation.

3) In conversation state, the traffic must be guided to the 1800 MHz cells in

lower layers and levels according to the hierarchy cell structure. In addition,



you can use Huawei dual-band handover algorithms so that the traffic load

can be allocated more properly.

II. Hierarchical Cell Structure

According to the hierarchy cell structure of the dual-band network, a GSM

system covering an area can be divided into four layers, as listed in Table 5-1.

Table 5-1 Four layers of a GSM system

Layer Description

4

This layer consists of umbrella cells, namely, GSM 900MHz macro

cells. They provide upper coverage and connect the fasting moving

mobile stations.

3This layer consists of GSM 900 micro cells, and most of the

subscribers are gathering in this layer.

2

This layer consists of the GSM 1800MHz cells whose coverage area

is similar to that of the GSM 900 MHz cell. It is designed in case of

frequency resource emergency. In the future, most of the dual-band

subscribers will gather in this layer.

1

This layer consists of the mini cells of GSM 1800 MHz and GSM

900MHz. They are designed for covering hotspot areas and dead

zones.

Figure 5-2 shows the hierarchy cell structure of a dual-band network.

Figure 5-2 Hierarchical cell structure of a dual-band network

To enable the network to develop smoothly and flexibly, you can divide each of

the four layers into multiple levels, and then you can set multiple priority classes

(for example, 16 classes) for the levels in each layer. This method is not only



helpful for adjusting the traffic load in part of the areas. Therefore, the

hierarchical cell structure enhances the cooperation of the current network

equipments and meets the devolvement of the future network.

In terms of traffic priority, the cells in lower layers and levels has higher priorities,

namely, the cells in lower layers has the priority to absorb the traffic.

The handover algorithms of a dual-band network are listed in Table 5-1.

Table 5-1 Handover algorithms of a dual-band network

Name Description

Inter-layer and inter-level handover

algorithm

The network support to control the cells

according to their priority classes.

Emergency handover algorithmIt manages the emergent cases, such as

TA, BQ, and fast level fall.

Load sharing handover algorithmIt enables cells to share load with each

other.

Handover algorithms based on

speed and sensibility

It helps fast-moving mobile phones to

perform handover flexibly.

Interference handover algorithmIt helps reduce interference and enhance

voice quality.

Edge handover algorithmIt provides mobile phones with better

levels and service qualities.

PBGT handover algorithm based

on path loss

It supports mobile phones to hand over to

a better cell.

Co-MSC/BSC handover control

algorithms–

5.9.5 Dual-Band Networking Engineering Implementation

During network construction and optimization, a dual-band network is debugged

and commissioned step by step, which facilitates debugging the new GSM 1800

MHz networks and the original GSM 900MHz networks that has been expanded

respectively. After each signal network is perfectly adjusted, you must debug

each base station in the dual-band network. And you cannot stop the debugging

until the whole dual-band network is finished.



The construction of a whole dual-band network can be divided into three stages,

namely, deployment preparation, signal 1800 MHz network debugging, and

900/1800 MHz dual-band network debugging.

I. Deployment perparation

The coordination of dual-band technologies and network planning must be

finished in this stage. The coordination of dual-band network technologies is a

prerequisite for the cooperation of different carriers’ networks. Network planning

is the first step in network construction and involves many tasks, including base

station address survey, channel number planning, electromagnetic background

test, coverage test, and so on.

The followings must be emphasized in dual-band cooperation:

The customers, the third party (the designing institute or the original

equipment supplier), and the new equipment supplier must be cooperate

with each other well.

If one party meets a tough problem during the debugging of the dual-band

network, the engineers from a third party must be present in site and help

position the problem.

The 900 MHz BSC and 1800 MHz BSC must synchronize their clocks with

the same source clock. Meanwhile, the clock of each base station in the

existing GSM 900 MHz network can lock the clock of the BSC, and the clock

of the BSC can lock the clock of the MSC.

When modifying the parameters related to dual-band handover (such as

modifying the parameters at the BSC side or MSC side), you must notify

that to other two parties.

If the some problems concerning the cooperation of dual-band network

arise, a meeting must be organized, in which each party discuss with each

other on how to solve the problems.

Both the designing institute or the original equipment supplier and the new

equipment supplier must provide the project implementation plan, cutover

plan, and precise cell information.

II. Signal 1800 MHz network debugging

At this stage, you need not modify any data of the original GSM 900 MHz

network, but it is still the GSM 900MHz network provides services to subscribers.

The GSM 1800MHz network does not absorb traffic.

When debugging the GSM 1800MHz network, you must adjust the following

parameter so that the existing subscribers can be least affected.

In the system message data list, set the parameter “CBA” to “NO” to prevent

general subscribers from selecting and reselecting the 1800 MHz network.



Theoretically, general subscribers can hand over to the 1800 MHz network, but

in fact, the handover relationship is not configured with the dual-band network,

so the general subscribers cannot enter the 1800 MHz network.

After that, you use the testing mobile phone which can access the network by

force to perform dialing test in each cell. If all goes normal, you can test

coverage, handover, power control, interference, downlink and uplink balance,

power adjustment, the coverage of the GSM 900MHz network, and the coverage

of the GSM 1800MHz network.

Through these tests, you can not only discover the problems present in the

networks, but also adjust the channel number, power, tilt angle, and parameter

setting and optimize the parameter configuration for the GSM 1800MHz cell. In

this case, the coverage and operation of the single GSM 1800MHz network can

be ensured.

III. 900/1800 MHz dual-band network debugging

After finishing the single GSM 1800MHz network debugging, you must change

back the parameter “CBA” to “YES” and configure the data for dual-band

handover. The tests involved into the dual-band network debugging include:

Cell reselection and location update

Traffic load control

Continuous conversation mode

Automatic dialing and scan

Dual-band network handover

Calls and handovers initiated on major streets

Calls and handovers initiated on edge areas

Dialing tests in poor coverage areas and indoor environment

Dialing tests in outdoor and indoor environments in key areas

Table 5-2 lists the test items during cell selection and handover

Table 5-2 Test items during cell reselection and handover

Test state Test time

When a mobile phone

performs cell selection in

idle mode (CRO, C1,

and C2.)

When the mobile phone performs cell selection

from a 900MHz cell to an 1800MHz cell.

When the mobile phone performs cell selection

from an 1800MHz cell to a 900MHz cell.

When a mobile phone

performs handover in

conversation state

The mobile phone first establishes the conversation

in a 900MHz cell, and then hands over to an

1800MHz cell.




in an 1800MHz cell, and then hands over to a

900MHz cell.


in a 900MHz cell, and then hands over to an

1800MHz cell, and finally hands over back to a 900

MHz cell controlled by the same MSC.


in an 1800MHz cell, and then hands over to a

900MHz cell, and finally hands over back to an

1800 MHz cell controlled by the same MSC.

At this stage, you must configure the dual-band data for the GSM 900MHz and

1800MHz cells. The data includes neighbor cell relationship, layer and level

setting, handover type, and handover threshold. In this case, when a mobile

phone is in idle mode, it can reselect an 1800MHz cell, the GSM 1800MHz

network can absorb the traffic of dual-band subscribers, and the subscribers can

perform handover between 1800MHz cells and 900MHz cells.

At the beginning, you can control the GSM 1800MHz network to absorb only a

small part of the traffic of subscribers through adjusting the setting of CRO and

handover threshold. When good cell reselection and dual-band handover are

ensured, you can take measures to enable the GSM 1800MHz network to

absorb more traffic, with the prerequisites that no congestion is present among

cells and the network quality is ensured.

At this stage, the following parameters must be configured:

The parameters related to cell selection and reselection, including CBA,

CBQ, ACCMIN, CRH, and CRO.

The parameters related to neighbor cell relationship, layer and level setting,

and handover.

The configuration of the previous parameters must be based on the prerequisite

that the cooperation of the GSM 1800MHz cells and GSM 900MHz cells is

normal.

After the GSM 900MHz and 1800MHz dual-band network is enabled, you must

do the followings:

1) Find out the problems present in the network through multiple means, such

as drive test.

2) Adjust and optimize the network according to the problems so that the dual-

band network can run stably.



3) Check if the dual-band network runs stably, analyze all the traffic statistic

data, and check the network operation indexes.

4) Make sure the problems and take effective measures according to the

analysis of the drive test and traffic statistics.

5) Adjust the related parameters and retest the network till the network indexes

meet the design requirements.

Thus, a dual-band network is constructed and optimized according to the three

stages as introduced in this section.

5.10 Design of Indoor Coverage System

5.10.1 Characteristics of Indoor coverage

With the rapid development of economy, hotels, commercial centers, large-scale

flats, underground railways, and underground parking areas are arising by batch.

As a result, mobile stations are more frequently used in indoor environment.

Thus, they require better indoor mobile communication services.

Generally, the following problems are present in indoor mobile communication

systems:

From the perspective of coverage, the complex indoor structure and the

shielding and absorbing effect of the buildings cause great radio wave

transmission loss. As a result, the signals in some areas may be weak,

especially the signals in the first and second floors in the underground are

quite weak, or even there are dead zones. In this case, mobile stations

cannot necessarily access the network, there is no paging response, or

subscribers are not in service areas.

From the perspective of network quality, the factors interfering radio

frequencies are probably present in upper floors of high buildings. In this

case, the signals in service areas are not stable, so “ping pong effect” may

occur and conversation quality cannot be ensured.

From the perspective of network capacity, if mobile stations are frequently

used in buildings, such as large-scale shopping centers, conference halls,

some areas in the network cannot meet the requirements of subscribers. In

this case, congestion may occur on radio channels.

If the indoor coverage is realized by a repeater, an outdoor high-power base

station, or a great-height outdoor antenna, the following problems may arise:

The penetration loss is great, so the indoor coverage is not satisfying. In this

case, a large number of dead zones are present, so subscribers cannot

keep conversation.



If a repeater is adopted, the level of original signals must be high. In

addition, the cross-modulation and intra-frequency interference is great, so

the conversation quality is weak and call drop ratio is high.

The network capacity is limited and the call connected ratio is low.

The frequency planning is hard to be performed for the network and the

network capacity is hard to be expanded.

The “detached island effect” is great.

The value-added services are restricted for group subscribers due to

network quality and capacity.

To enhance the grade of service, we must improve indoor coverage immediately.

When designing an indoor coverage system, we must make the following

considerations:

A new indoor coverage system cannot affect the existing network.

Enough capacity of an indoor system must be ensured.

An indoor system must support new services and functions.

The chapter analyzes the design of indoor coverage system from the following

aspects:

Indoor Antenna System Design

Capacity Analysis and Design

Frequency Planning

Traffic Control

5.10.2 Indoor Antenna System Design

I. RF design

(1) Link budget

In an indoor coverage system, the link budget formula is as follows:

Pant MSsens RFmargargarg IFm argargarg BL LNFm argargarg Lpath Gant

Here,

Pant = antenna input interface power

RFmarg = Raleigh fading margin

IFmarg = access margin (depends on environment)

LNFmarg = design margin (generally, it is 5 dB)

BL = body loss (900MHz: 5 dB; 1800/1900MHz: 3 dB)

MSsens = mobile station sensitivity

Lpath = path loss

Here, Lpath = 20logd (m) + 30logf (MHz) - 28 dB + α. When there no barrier loss,

Lp = 20logd (m) + 30logf (MHz) - 28 dB. The “α” indicates the loss caused by othe

r bariers.



Table 5-1 lists the penetration loss caused by some typical barriers.

Table 5-1 Penetration loss caused by some typical barriers

Barrier Penetration loss (dB)

Partition wall 5–20 dB

Floor > 20 dB

Furniture 2–15 dB

Thick glass 6–10 dB

Train carriage 15–30 dB

Elevator Around 30 dB

Tunnel curve 10–40 dB/km (for the signals from fixed sigal sources)

Rectangle tunnel 10–15 dB/km

Cylindrical tunnel 35–40 dB/km

Note:

Because the penetration in cylindrical tunnels is great, leaky cables are applied

in cylindrical tunnels.

When performing link budget, you must consider the followings:

In an indoor multi-antenna system, the link budget for test points must be in

accordance with the link with the minimum loss.

Under the same converge area, the EIRP at each antenna interface must be

consistent, and the error must be controlled within 10 dB.

The uplink signal must be designed to a high value, so antenna diversity is

unnecessary.

To reduce uplink interference, you must properly set the maximum transit

power of the mobile station and enable the power control function of the

mobile station.

A certain margin must be leaved for error correction and future system

expansion.

The estimation and design for interference margin vary with the distance

from the outer wall. The smaller the distance, the larger the interference

margin is designed.

(2) Service quality design (interference degree)

Table 5-2 describes the interference degrees of indoor cells in different

situations.



Table 5-2 Interference degree of indoor cells

Situations Interference degree

The indoor cell and the surrounded buildings are

of the same height, and frequency reuse degree

is greater than 12.

The outdoor coverage system has little effect on

the indoor cells.

The indoor system has dedicated frequencies

and frequency reuse seldom exists.

Little interference

The situation and frequency reuse are intervenient

between the two.General interference

The buildings within the indoor cell are higher

than surrounded buildings.

The frequency reuse degree is smaller than 9.

Great interference

Note:

The actual interference level changes with network layout and frequency re-

planning, and it can be tested according to actual situations.

(3) Service quality design (interference margin design)

The greater the interference in an area, the greater the interference margin

(IFmarg) is designed, and the higher the level the mobile station needs to receive,

as listed in Table 5-3.

Table 5-3 Relationship between interference and mobile station receiving level

Actual level interference degree Mobile station receiving level (dBm)

Great -65

General -75

Little -85

Note:

When a dual-band system is adopted in the indoor environment, the indexes of

mobile station receiving level are designed according to the 1800 MHz system

standard.



II. Antenna system design

When designing an indoor distribution system, you must first survey the building

type, structure, interference environment, customers, and then analyze the path

loss. Finally, decide the antenna type, number, and installation location

according to the requirements of an area.

This section introduces the antenna design guidelines in some typical cases.

(1) Single cell

If the indoor coverage is realized by a signal cell, each antenna must be

designed to ensure that signals are evenly distributed in the coverage area.

Generally, it is recommended to install the antenna in a zigzag way, as shown in

Figure 5-2.

Figure 5-2 Antenna design guideline in signal cell

(2) Multi-cells

If the indoor coverage is realized by multiple cells, a certain distance must be

leaved between intra-frequency reuse cells. Each antenna must also be

designed to ensure that signals are evenly distributed in the coverage area of

each cell. If the frequencies are reused frequently, it is recommended to install

the antennas on different layers at the same position of the layer, as shown in

Figure 5-3.



Figure 5-3 Antenna design guidelines in multi-cells

(3) Closed building

A closed building has the characteristics, such as thick outer wall, great signal

attenuation, and little leakage. In addition, it is little affected by outdoor intra-

frequency cells. Therefore, the frequency between floors is easily to be planned.

For the antenna design guideline in a closed environment, see Figure 5-4.

Figure 5-4 Antenna design guideline in closed environment

(4) Half-open environment

For a half-open building, the outer wall is made of glasses, so the signal

attenuation is small. Within the building are the open conference halls, which are

greatly affected by outdoor intra-frequency cells, so you must plan dedicated

frequencies or adopt the multi-antenna system with low output power to limit the

edges of the indoor cells within the building, as shown in Figure 5-5.

Figure 5-5 Antenna design guideline in half-closed environment

(5) Frame-structure building

For a frame-structure building, the number of internal walls is large and they are

thick. Therefore, if the antenna is installed at the corridors, the antenna output

power must be high so that good coverage can be ensured. In this case, signals

will leak at the windows near the corridor, so you must plan dedicated

frequencies for the building. The distance of the intra-frequency cells between

floors is larger than that in other environments. For the antenna design guideline

in frame-structure building, see Figure 5-6.



Figure 5-6 Antenna design guideline in frame-structure building

(6) Office building

The indoor environment of office buildings requires high grade of services, so its

coverage is realized by several directional and omni antennas. You can control

the coverage area easily through properly designing the effective radiation power

in the cell. For design guideline, see Figure 5-7.

Figure 5-7 Antenna design guideline in office building

(7) Parking area

Parking area has no special requirement on capacity and mobile station

receiving level (-90 dBm). For a parking area, the elevator, escalator, entrance

and exit are key coverage areas, as shown in Figure 5-8.



Figure 5-8 Antenna design guideline in parking area

(8) Supermarket

Supermarkets have certain requirements on coverage and capacity. The

antennas can be designed according to actual structure of the buildings. For the

antenna design guideline, see Figure 5-9.

Figure 5-9 Antenna design guideline in supermarket

III. Survey

The antenna design and installation is finally decided according to the survey,

which includes the following aspects:

Detailed coverage area and signal quality and converge requirements

Distribution of the signals in coverage areas

Composition of buildings in coverage areas

Signal access location and mode

Installation position



According to the survey, you must output the final topological structure diagram,

antenna cabling scheme, and list of materials. Generally, the omni antenna is

installed at the ceiling center. The small directional antenna is hung on the inner

side of the outer wall, with the radiation directed to indoor part. In this case, the

effect of the antenna against the outdoor system can be reduced to the

minimum, so the C/I requirement of the outdoor system can be met.

If possible, you can test the coverage and adjust the antenna design according

to the test result, or re-plan the frequency to ensure the voice quality. Generally,

if the radiation power at the antenna interface is 10 dBm, the 2 dBi small indoor

omni antenna is used. In this case, if the walls are densely distributed in the

areas within 30 meters from the antenna, the coverage level can reach -70 dBm.

5.10.3 Capacity Analysis and Design

Before analyzing the capacity, you must define the type of the indoor service

area. For details, see Table 5-1.

Table 5-1 Definition of indoor service area type

Indoor

service area

type

Characteristic Example

Public

service area

The traffic is hard to be predicted.

The population number varies with day

and night.

The capacity characteristics, such as

uneven distribution and bursting must

be considered.

The grade of service and the traffic of

each subscriber are similar to that for

outdoor cells.

Airport, shopping

center, and play

ground.

Commercial

service area

The existed fixed networks are

frequently used.

The traffic is relatively fixed and easy to

be calculated.

High service quality is required.

Generally, the grade of service (GoS) is

1%, the traffic of each subscriber can

reach 0.1 Erl.

Office building

and commercial

hotels of high

ranks.



For the cell organization mode of distributed antenna system, see Figure 5-10.

Figure 5-10 Cell organization mode of distributed antenna system

As shown in Figure 5-10, there are two cell organization modes of distributed

antenna system, namely, single cell and multiple vertical split cells. The single

cell is applied to the indoor environment which requires smell coverage area.

The multiple vertical split cells are applied to the indoor environment with dense

traffic.

Likewise, a single cell will split when the capacity does not meet the requirement,

with vertical splitting the splitting mode. Generally, a cell will vertically split into at

least three cells so that frequency reuse can be ensured. Four layers must be

present between two intra-frequency cells, as shown in Figure 5-11. To avoid

interference between frequencies, you must take measures to prevent a cell from

horizontally splitting.

Figure 5-11 Vertical cell splitting



5.10.4 Frequency Planning

If the dedicated frequency is adopted in indoors, the frequency planning is

relatively simple. Generally, the frequency reuse mode in business service areas

is almost the same as that in pubic service areas. If the frequency resource is

adequate, you must try best to use dedicated band for indoor coverage. If not,

you can search the available channel numbers with relatively small interference

through scanning the channel numbers. If the frequency resources of the 900

MHz cannot meet requirements, you can introduce the 1800 MHz frequency;

namely, use a dual-band system.

If you steal frequency resource for indoor system due to no available dedicated

frequency, you must pay attention to the followings:

Do not select the frequencies of the neighbor cells.

Ensure that the BCCH frequencies are not interfered.

The interference on the TCH frequencies can be reduced with the help of

radio frequency hopping.

Search the available uplink frequencies through using BTS equipments to

scanning the uplink channel numbers.

Search the available downlink frequencies through using drive test

equipment to scanning the downlink channel numbers.

If the hierarchical cell structure is not used, the cell with the strongest signal

level is the service cell, and the interference from neighbor frequencies can

be neglected.

If the hierarchical cell structure is used, the cell with the strongest signal

level cannot necessarily be the service cell, so you must take measures to

reduce the interference from neighbor frequencies.

Because the environment is urban areas is quite complicated, especially the

effect of the antenna back lobe is present, the service areas for high buildings

are greatly interfered, so you must carefully plan the frequencies for the indoor

coverage of high buildings. Generally, for the lower floors, you can plan the

frequencies according to general method. For the higher floors where the

interference is strong, you can use dedicated channel numbers. However, the

final frequency planning must be based on practical tests.

5.10.5 Traffic Control

The indoor coverage system for high buildings can be taken as a system

independent of outdoor systems if the coverage of the indoor system is good.

Theoretically, you can only consider the cell selection and reselection, handover

relationship, and the compact on outdoor networks at the entrances and exits of

the building.



However, the actual conditions are quite complicated. For example, the signals

outside of the building may be strong. In this case, if a mobile station is powered

off, it may camp on an outside cell. Therefore, when optimizing the network, you

must set the one-way adjacent cell and two-way adjacent cell according to actual

conditions and set the parameters, such as CRO and TO to a proper value

according to the regularity of cell selection and reselection. In addition, you can

set the indoor cells to a high priority so as to reserve more traffic. And the inter-

layer handover threshold and hysteresis are defined and adjusted according to

actual conditions.

5.11 Tunnel Coverage

5.11.1 Characteristic of Tunnel Coverage

At present, most of the tunnels are dead zones, so you must make out special

solutions for tunnel coverage. The tunnel types include railway tunnel, highroad

tunnel, and underground railway tunnel. Each tunnel has its characteristics, and

they are specified as follows.

For the highroad tunnel, it is wide. The coverage in the highroad tunnels is

relatively stable. When there are vehicles passing by, you can select the

antennas with a larger size to obtain a higher gain, so the coverage distance is

larger.

For the railway tunnel, it is narrow, especially when there is a train passing by;

only a little room is left in the tunnel, so the radio propagation is greatly affected.

Moreover, the train has great effect on radio signals. Since the antenna

installation room is quite limited, the antenna size and gain are greatly restricted.

In addition, because general cars cannot be driven to such tunnels, the tunnel

coverage is hard to be tested. Therefore, the planning for highroad coverage is

different from that of the railway coverage.

The length of tunnels ranges from several hundred meters to several kilometers.

For short tunnels, you can adopt flexible and economical means to realize the

coverage. For example, you can install a general antenna near one end of the

tunnel, with the radiation directed to the inside. For long tunnels, however, you

must adopt other means. Actually, the coverage solution varies with tunnels, so it

is designed according to actual conditions.

Figure 5-12 and Figure 5-13 show the cross section of the single-track railway

tunnel and multi-track railway tunnel. The smaller the area of the cross section,

the greater the loss when a train passes through the tunnel. The related

calculation and analysis are based on the multi-track railway tunnels and

highroad tunnels. For the calculation and analysis for single-track tunnels, the

protection margin can be 5 dB greater than that of multi-track railway tunnels.



Figure 5-12 Cross section of single-track railway

Figure 5-13 Cross section of multi-track railways

Before planning tunnel coverage, you must prepare for the following data:

Length of the tunnel

Width of the tunnel

Number of tunnel holes (1 or 2)

Needed coverage probability (50%, 90%, 98% or 99%)

Structure of the tunnel (it is constructed with metals or concretes)

Number of needed carriers (1–30)

Minimum receiving level in the tunnel (generally, it ranges from -85 dBm to -

102 dBm)

Distance between tunnel holes

Whether AC/DC is available

Whether the hole can be punched in the tunnel wall

Signal level at the tunnel entrance

Existed signal level in the tunnel

5.11.2 Tunnel Coverage Solution

I. Link budget

Indoor radio link loss is mainly decided by path loss medium value and shadow

fading. A tunnel can be taken as a tube. The signals are transmitted through the

reflection of walls and straight transmission, with straight transmission the major



form. ITU-R suggests an indoor propagation model on page 1238, which is also

effective for tunnel coverage. The formula is as follows:

Lpath = 20 lg f + 30 lg d + Lf (n) - 28 dB

Here,

“f” indicates frequency (MHz)

“d” indicates distance (m)

“Lf” indicates penetration loss factors between floors (dB)

“n” indicates the number of floors lying between the mobile station and

antenna.

The Lf (n) can be neglected in tunnel coverage, so the following equation can be

applied in the calculation of the radio propagation in tunnels. That is:

Lpath = 20 lgf + 30 lg d - 28 dB

Table 5-1 lists the path loss in different tunnels.

Table 5-1 Path loss in different tunnels

Distance (m) GSM 900MHz (dB) GSM 1800MHz (dB)

50 82.0 88.1

100 91.0 97.0

150 86.3 102.1

200 100.1 106.1

300 105.3 111.4

II. GSM signal source selection

A GSM signal source and a set of distributed antenna system are a must for

tunnel coverage. For tunnel coverage, the GSM signal source is selected

according to the radio coverage, transmission, traffic, and the existing network

equipments near the tunnel. A macro cell base station, a micro cell base station,

or a repeater can work as a GSM signal source for the tunnel coverage.

For the coverage of railway tunnels and highroad tunnels, the indoor macro cell

base station is seldom used as signal source, but it can be used for an

underground railway which requires the coverage of platforms and entrances. In

this case, the capacity of the signal source must be great. In most cases,

however, the tunnel coverage is realized by micro cell signals.

For the areas to be covered, if the nearby network capacity is adequate, the

capacity expansion is unnecessary. And if there are good GSM signals available,



namely, the donor signal level meets the requirements of a repeater (for

example, -70 dBm); a repeater can work as the signal source for the tunnel

coverage. With the increase of traffic, however, you must use GSM base stations

to replace the repeaters.

Adequate isolation must left between donor antenna and retransmission

antenna, though it will cause difficulty in antenna installation. Generally, the log-

periodical antenna with great front-to-back ratio is used as the retransmission

antenna.

The general antenna (wireless repeater), coaxial cable, and optical fiber (optical

repeater) can connect a repeater to a donor cell.

For tunnel coverage, the installation space and auxiliary equipments are quite

limited, so micro cell base stations and repeaters instead of macro cell base

stations are often applied in tunnel coverage.

In mountain areas, repeaters are more likely used because strong signal level

often exists at the mountain tops near the tunnel. In this case, the antenna

isolation requirement can be easily met. If the signal level of the existed network

near the tunnel is not strong enough, you can use a micro cell for the tunnel

coverage.

III. Antenna feeder system selection

After deciding the GSM signal source, you must configure the antenna feeder

system for the tunnel coverage according to actual conditions. Three types of

configuration are available, namely, coaxial feeder passive distributed antenna,

optical fiber feeder active distributed antenna, and leaky cable. Hereunder

introduces the tunnel coverage based on coaxial feeder passive distributed

antenna and leaky cable.

5.11.3 Tunnel Coverage Based on Coaxial distributed antenna system

In a coaxial distributed antenna system, the following RF components are used:

Feeder (3/8", 1/2", or 7/8") and jumper

Power splitter

Power splitter

Antenna

This section introduces three tunnel coverage solutions based on the coaxial

distributed antenna system.

I. Solution 1

Figure 5-14 shows the tunnel coverage solution based on the bi-directional

passive distributed antenna system.



Figure 5-14 Tunnel coverage solution based on bi-directional passive distributed

antenna system

According to this solution, if the needed minimum signal level is -85dBm (the

location probability is 50%), you must add a margin of 8 dB if the want to

enhance the location probability to 90%.

If the gain of the bi-directional antenna is 5 dBi, the loss of the equal probability

power splitter and the jumper is 2 dB, and the feeder with the specification of

7/8" is used, the path loss in 100 meters is 4 dB and the output power of the

equipment is 39 dBm.

Suppose that the level of the signals transmitted by the first bi-directional

antenna is -85 dBm at the tunnel entrance, you can calculate the distance

between the antenna and the tunnel entrance using the following equation:

Pout- Lpath (d) – Lcable (d) – Ljumper + Gant = -85dBm + 8dB90%_loc.Prob

Here,

Pout indicates the output power (39dBm).

Lpath (d) indicates the path loss from the first bi-directional antenna to the

tunnel entrance.

Lcable (d) indicates the cable loss.

Ljumper indicates the jumper loss (2 × 2 dB).

Gant indicates the antenna gain (5 dBi).

If introducing the previous data to the equation, you can obtain the sum of the

Lpath (d) and Lcable (d), that is, 117 dB.

For the relationship between distance “d” and Lpath (d) and Lcable (d), see

Figure 5-15, in which the curve indicates Lpath (d) and the slant line indicates

Lcable (d).



Figure 5-15 Relationship of path loss and 7/8” cable loss

According to Figure 5-15, you can obtain that d = 301m through estimation.

If a power splitter is adopted for the first antenna, a loss of 3dB must be added.

In this case, the sum of Lpath (d) and Lcable (d) is 114 dB.

According to Figure 5-15, you can also obtain that d = 261m through estimation.

For railway tunnels, train filling will affect signal propagation, so a protection

margin of 5dB must be considered when the antenna is installed in the tunnel. In

this case, d = 240m. That is, if a bi-directional antenna is installed in the tunnel, it

can coverage a distance of 480m.

If a power splitter is adopted for the second antenna, the coverage distance

between the first antenna and the second antenna will be shortened unless an

amplifier is used.

The followings analyze the coverage when no amplifier is adopted for the second

antenna.

The total power output by the first power splitter (it is installed at the first

antenna) Pout1 is expressed as follows:

Pout1 = Pout – Lcable (d) - Ljumper - Lsplitter = 39dBm –Lcable (261m) - 2dB -

3dB= 23.56 dBm. (The cable loss in 261m is about 10.44 dB, jumper loss is 2

dB, and the power splitter intersection loss is 3dB).

Suppose the overlapping level between the two antennas is -85 dBm, the

distance between the second antenna and the first antenna is: d2 = d + x. Here,

“d” indicates the coverage distance of the first antenna (261m), and “x” indicates

the coverage distance of the second antenna in the single direction.

According to the previous analysis, the following two equations can be obtained:



Pout1 – Lcable (261m) – Lcable (x) – Ljumper + Gant – Lpath (x) = - 85dBm

+ 8dB90%_loc.Prob

Lpath (x) + Lcable (x) = 108.56dB

Plus the two equations, you can obtain the value of x, that is, 100m. This means

that when no amplifier is adopted, two antennas can coverage a tunnel distance

of 722m, namely, 2*(261 + 100) m = 722m.

If you adopt cascaded antennas, the transmit power is relative low due to the

coaxial cable loss. In this case, you can use the amplifier to amplify the power.

II. Solution 2

If a tunnel is not long, you can adopt a simpler coverage mode, as shown in

Figure 5-16.

Figure 5-16 Tunnel coverage solution based on a single antenna

According to this solution, a directional antenna is installed at the tunnel

entrance, with the radiation directed to the inside. The following analyze this

coverage solution.

In this solution, Pout = 39 dBm (suppose that the output power of the GSM

signal source is 8W).

If the Lpath (d) indicates propagation loss, the sum of Lcable (d) and Ljumper is

5dB, the antenna gain Gant is 8 dBi, and the needed received level is -77dBm,

the Lpath (d) is expressed as follows:

Lpath (d) = 39dBm - 5dB + 8dBi – (-77dBm) = 119 dB

According to the equation Lpath (d) = 20 lg10f + 30 lg10d - 28 dB, the value of

“d” can be obtained, that is, 858m.

The previous analysis is applicable to highroad tunnels. For railway tunnels, you

can consider a margin of 10 dB due to the effect of train filling, but the coverage

distance of the antenna in railway tunnels is calculated the same as that in

highroad tunnels. According to the calculation, d = 398m.



5.11.4 Tunnel Coverage Based on Leaky Cable System

If adopting leaky cables to realize the tunnel coverage, you must find the

specifications of the leaky cables and complete the leaky cable design according

to the following steps:

6) Decide coverage factor

7) Calculate the gain of the bi-directional amplifier

8) Estimate the length of the leaky cable between the feeder source and the

first amplifier

9) Estimate the length of the leaky cable between the amplifiers

10) Decide the number of needed amplifiers

The followings describe these steps in details.

I. Decide coverage factor

The following information is needed for deciding the coverage factor:

Coupler loss

Number of carriers

Coverage probability

Coverage factor indicates the loss in the areas 2 meters beyond the leaky cable

(along the vertical direction). This loss includes the coupler loss of the leaky

cable and protection margin required by the coverage probability. If 90% of

coverage probability is required, you must add 8dB to the medium level. Some

leaky cables specify the relationship between the coverage probability and

coupler loss.

The coverage factor is determined by the parameters, such as coupler loss, RF

carrier number, coverage probability, and tunnel type. For the decision of

coverage factor in concreter tunnels, see Figure 5-1. For the decision of

coverage factor in metal tunnels, see Figure 5-2. When deciding the coverage

factor, you can fix a point in the graph and mark a horizontal line through this

point, and this line intersects required coverage probability. This intersection

point is the coverage factor.



Figure 5-1 Coverage factor in concrete tunnels

Figure 5-2 Coverage factor in metal tunnels

For example, if the leaky cable with a coupler loss of 71 (900 MHz) is used, the

RF carrier number is 18, and the coverage probability is 90, the coverage factor

in a concrete tunnel is -77 according to Figure 5-1.

II. Decide cable length between GSM signal source and the first amplifier

Before deciding cable length between GSM source and the first amplifier, you

must obtain the following information:

Transmit power of the signal source (dBm)



Jumper loss: 1 dB

Connector loss: 1 dB

Leaky cable loss: 2 dB

Transmit power at the feeder source (dBm)

When calculating the power at a point of the feeder, you must subtract the feeder

propagation loss from the GSM signal source. If a wireless repeater with an

output power of 18 dBm (18 carriers) is used as the GSM signal source, and the

attenuation from the jumper to feeder, and from the feeder to the leaky cable is 7

dB (That is, the power from the repeater is transmitted from a jumper to a feeder,

and then from the jumper to a leaky cable, so four connectors are needed.

Generally, the attenuation is 2 dB for each jumper, 1 dB for each feeder, and 0.5

dB for each connector, so the total attenuation is 7 dB.), the transmit power at

this point is 11 dB. For the connection of leaky cable, see Figure 5-3.

Figure 5-3 Connection scheme of leaky cable

Suppose the needed signal level in a tunnel is -85 dBm, the signal level at the

first amplifier must be equal to or greater than -85 dBm. The coupler loss and

longitudinal propagation loss of the leaky cable are present between the signal

feeder point and the first amplifier. They are calculated according to the following

equation:

LossLong = 11dBm – (-85dBm) + Losscoup. Here, Losscoup indicates the coverage

factor, and it is -77dB when 90% coverage is ensured. Therefore, the LossLong is

19 dB (that is, 11dBm + 85dBm -77dB = 19dB).

The cable length between the signal feeder source and the first amplifier can be

obtained according to Figure 5-4 and Figure 5-5. For example, suppose that the



attenuation is 4.3dB/100 for the leaky cable, you can mark a plumb line at the

point indicating 4.3dB. This plumb line will intersect the curve indicating 19 dB at

a point, and then you mark a horizontal line starting from this point. The

horizontal line will intersect the right vertical axis at a point. And this point shows

the cable length. According to this example, the distance between the signal

source and the first amplifier is 440m (that is, 19/4.3 = 440m).

Figure 5-4 Cable length between amplifiers in metal tunnels

Figure 5-5 Cable length between amplifiers in concrete cables

According to the previous figures, the left vertical axis indicates “Required

RADIAMP Gain”, which can be replaced by the radial loss of the leaky cable, but

it makes no difference.



III. Needed amplifier gain

Before calculating the maximum amplifier gain, you must collect the following

information:

The minimum acceptable signal level (dBm)

Coverage factor (dB)

The maximum output loss allowed by a single carrier (dBm)

If the amplifier is not added, the signal level output by the leaky cable for the

longest transmission distance is equal to the difference of the minimum

acceptable signal level and the coverage factor.

The signal level at the leaky cable beyond the longest transmission distance may

be lower the minimum acceptable level, so an amplifier must be added to amplify

the signals to the maximum output power allowed by a single carrier. The

amplification of this power is related to the specifications of the amplifier and the

number of carriers. If the maximum output power allowed by a single carrier is

known, the amplifier gain can be calculated as follows:

Needed amplifier gain = the maximum output power allowed by a single carrier

(it depends on the number of carriers) – (the minimum acceptable signal level –

coverage factor)

Along the leaky cable, the maximum output power allowed by each carrier of a

bi-directional amplifier is related to the number of carriers that have been

amplified. This is considered mainly for the intermodulation interference is

present, because the intermodulation interference will increase with the total

number of carriers that have been amplified, as shown in Figure 5-6.

Figure 5-6 Relationship between the maximum output power allowed by a single

carrier and the number of carriers that have been amplified



Needed amplifier gain = the minimum acceptable signal level – coverage factor +

the maximum output power allowed by a single carrier.

According to the previous equation, if the minimum acceptable signal level is -85

dBm, the coverage factor is -77, and the maximum output power allowed by a

single carrier is 5 dBm, the needed amplifier gain is 13 dB.

IV. Decide cable length between amplifiers

Before deciding the cable length between amplifiers, you must know the needed

amplifier gain and the cable loss (dB/100m). Figure 5-4 and Figure 5-5 help you

decide the cable length between amplifiers. For example, in a concrete tunnel, if

the amplifier gain is 13 dB and the cable attenuation is 4.3dB/100m, the cable

length between two amplifiers is 300m.

V. Decide the number of needed amplifiers

Before deciding the number of needed amplifiers, you must know the following

information:

The cable length between the feeder source and the first amplifier

The cable length between amplifiers

The tunnel length

If the previous information is known, the following formula can be used to

calculate the number of needed amplifiers. That is:

The number of amplifiers ≥ (the tunnel length – the cable length between the

feeder source and the first amplifier)/(the cable length between amplifiers),

rounding up to the nearest integer.

According to the formula, if the tunnel length is 1000m, the cable length between

amplifiers is 300m, and the cable length between the feeder source and the first

amplifier is 420m, 2 amplifies are needed. That is, (1000 – 420)/300 = 1.93, so

the nearest integer is 2.

After deciding the number of needed amplifiers, you can optimize the distance

between amplifiers. That is, you can obtain the distance between the two

amplifiers by dividing the remaining distance by the number of needed amplifier.

According to the previous example, it is 580/2 = 290m, namely, the distance

between the two amplifiers is 290m, as shown in Figure 5-7.

Figure 5-7 Distance between amplifiers



VI. Remarks on leaky cable installation

The leaky cable must not touch any metal. Generally, a leaky cable must be

installed at a spot 5m away from concrete walls and at least 10m away from

metal walls. In addition, a leaky cable must be installed near to the coverage

area. You cannot necessarily consider the line-of-sight propagation, because the

signals leaking from the cable will fill the space nearby.

5.11.5 Coverage Solutions to Tunnels in Different Length

This section introduces the coverage solutions to tunnels in different length. In

actual networking, the following coverage solutions may be used:

Micro base station (or repeater) + a single antenna

Micro base station (or repeater) + distributed antenna system

Micro base station (or repeater) + leaky cable

Before deciding which coverage solution should be adopted, you must consider

the followings:

Is the GSM signal near the tunnel entrance strong enough?

Is there any available transmission link near the tunnel?

Generally, if the existed signal level near the tunnel entrance (including nearby

mountains) is lower than -80 dBm, the micro base station is recommended. If it is

greater than -80 dBm, the micro base station or the repeater is recommended. If

problems concerning transmission are present, the repeater is recommended.

When using the repeater, you must consider that certain isolation is required

between repeaters.

I. Coverage solution to short tunnels

Generally, the tunnels shorter than 100m are defined as short tunnels. When

planning the coverage for these tunnels, you must consider the coverage areas

near the tunnels. If several tunnels are close to each other, you can install a base

station or a repeater between the tunnels. If adopting a micro base station, you

must adopt the bi-directional antenna. If the antenna gain is 5 dBi, you should

install the antenna at the tunnel entrance so as to ensure coverage.

When designing tunnel coverage solutions, you must fully consider that fact that

cars and trains move at a high speed, so how to ensure normal handover after

the cars or trains steering into the tunnels is of vital importance.

If the repeater is used as the GSM signal source and the signals outside the

tunnel and the signals within the tunnel belong to the same cell, no handover

problem will occur. If the micro cell is used as the GSM signal source and the

signals outside the tunnels and the signals within the tunnel belong to different

cells, the signals in the outside cell will drop dramatically when the train steers



into the tunnel. In this case, handover failure may occur and call drop will be

resulted in.

To solve this problem, you can consider adopting the following methods:

Adopt the bi-directional antenna for the tunnel coverage, because it can

provide enough overlapping area for handover.

Enable special handover algorithms, such as fast level fall handover

algorithm. In this case, a mobile station can hand over to another cell when

the signal level falls fast.

Select the directional antenna with small front-to-back ratio.

II. Coverage solution to middle-length tunnels

This section introduces several typical coverage solutions to railway tunnels.

The followings are a series of assumptions:

The Huawei BTS3001C (the maximum output power is 8W) is used as the

GSM signal source.

The repeater with 1 amplified carrier and a maximum output power of 2W is

considered.

The lowest receiving level is designed to -85 dBm, and the coverage

probability is 90% (with a protection margin of 8 dB).

For railway tunnel coverage, because the train will affect signal

transmission, if the antenna is installed at the tunnel entrance, the protection

margin must be increased by 10 dB. If the antenna is installed in the tunnel,

the protection margin must be increased by 5dB.

The dedicated directional antenna with the specification of DB771S50NSY,

the horizontal half power angle of 60°, and the antenna gain of 8 dBi is used

at the tunnel entrance.

The bi-directional antenna with the specification of K738446 and antenna

gain of 5 dBi is used within the tunnel.

According to these assumptions, if a micro base station (39 dBm) is used as the

GSM signal source, the coverage distance is 400m when the antenna with a gain

of 8 dBi is installed at the tunnel entrance, and the coverage distance is 480m

when the bi-directional antenna with a gain of 5 dBi is installed in the tunnel.

If a repeater (33 dBm) is used as the GSM signal source, the coverage distance

is 250m when the antenna with a gain of 8 dBi is installed at the tunnel entrance,

and the coverage distance is 360m when the bi-directional antenna with a gain of

5 dBi is installed in the tunnel.

Therefore, for the tunnels shorter than 500m, you can use the combination of a

micro base station and a single antenna (or a repeater) for the tunnel coverage.

For curve tunnels, you can install a bi-directional antaean in the tunnel.



According to on-site survey on the cross-section, the available antenna size, and

the tunnel length, you can use the antenna with a higher gain to coverage the

tunnels a little longer than 500m.

III. Coverage solution to long tunnels

For the tunnels longer than 500m, you need to use the distributed antenna

system or the leaky cable for the coverage. The followings introduce the

coverage realized by the combination of a micro base station and a leaky cable

(or a repeater).


The Huawei BTS3001C (the maximum output power is 8W) is used as the

GSM signal source.

The repeater with 1 amplified carrier and a maximum output power of 2W is

considered.

The lowest receiving level is designed to -85 dBm, and the coverage

probability is 90% (with a protection margin of 8 dB).

The leaky cable with the specification of SLWY-50-22 and the radial loss of

5dB/100 m is used.

The coupler loss may be 77 dB when the 90% of signals are received.

According to these assumptions, if a micro base station (39 dBm) is used as the

GSM signal source, the coverage distance is 800m when only the leaky cable

but no amplifier is used. If a repeater (33 dBm) is used as the GSM signal

source, the coverage distance is 680m when only the leaky cable but no

amplifier is used. The coverage distance will be larger if leaky cables with

smaller loss are used.

For the coverage of still longer tunnels, you must use amplifiers to amplify

signals. That is, you can use either the distributed antenna system or the leaky

cable for the coverage solution. In terms of technical indexes and installation

space, coverage solution based on leaky cable is recommended. In terms of

cost, you must select a suitable coverage solution base on actual conditions.

5.12 Repeater Planning

5.12.1 Application Background

With rapid development of mobile communication networks, people have higher

requirements on service quality. They hope to enjoy mobile services anywhere

and anytime. As for telecommunication carriers, they cannot enable a base

station in some dead zones due to the reasons such as cost and transmission

conditions. In this case, a repeater can provide an auxiliary and economical

means to coverage the dead zones.



I. Repeater types

For the division of repeater types, see Table 5-1.



Table 5-1 Division of repeater types

Division

standardType Remark

Transmission

mode

Wireless repeater

A wireless repeater adopts a set of donor

antenna to receive the signals from the base

station. After amplifying the signals, it adopts

a set of retransmission antenna to forward the

signals in another direction. Generally, a

wireless repeater has only one receiving path,

so the diversity antenna is unnecessary.

Optical repeater

An optical repeater transmits signals using

optical fibers, so the repeater side and base

station side must have the optical

transmission capability.

Channel

bandwidth

Bandwidth selection

repeater

A bandwidth selection repeater is also called

wideband repeater, and it can select a

frequency (for example, the frequency with a

bandwidth of 6M, 19M, or 25M) and amplify it.

Channel selection

repeater

A channel selection repeater is also called

narrow band repeater or frequency selection

repeater. It amplifies the selected channel

numbers only. It is a narrow band repeater

and amplifies a limited channel numbers.

New styleSolar energy

repeater

A solar energy repeater is of the wideband

type. It is similar to a general wideband

repeater except that its power is solar energy.

Product type

Wireless frequency

selection repeater

Currently, the types of the repeaters listed in

the left column are in commercial use.

Optical frequency

selection repeater

Wireless wideband

repeater

Optical wideband

repeater



II. Comparison between repeater and micro cell

For the comparison between the repeater and micro cell, see Table 5-2.

Table 5-2 Comparison between repeater and micro cell

Micro cell Repeater

Many equipments and a long period

are needed for constructing a micro

cell.

A repeater is installed in a flexible way

and the base station equipments and

transmission equipments are

unnecessary.

A micro cell can expand the system

capacity. When the cells near a base

station are busy, a micro cell can be

used to ease the congestion.

A repeater can absorb traffic. When a

cell is idle, it brings the traffic to this

cell, thus enhancing the utilization

ratio of the equipments. A repeater

does not expand the capacity for a

system.

The system needs to allocate channel

numbers to a micro cell, but this is

hard to be realized in the areas where

the frequency resource is scarce.

The system does not need to allocate

channel numbers to a repeater, but it

must prevent the repeater from

interfering with other cells.

Note:

The filter of an intra-frequency repeater will produce a delay of about 5μs.

Theoretically, the maximum effective coverage distance of a GSM cell will be

smaller than 35km in this case.

A GSM system must enable the dynamic power control function, which is

transparent to a repeater. Generally, you must adopt the automatic level control

technologies (ALC) for a repeater.

Note:

When the ALC technology is applied to a repeater, if a mobile station is too near

to the repeater, the repeater will reduce the gains for all the mobile stations

within its service area. In this case, the conversation quality of some mobile

stations will become poor, or even call drop may occur; especially the mobile

stations far away from the repeater are greatly affected.



III. Application characteristics

Repeaters are mainly used to cover the dead zones in vast open land, and they

are the extension of the base stations. A repeater improves the coverage but

does add up to the traffic capacity of a network. However, because it enlarges

the coverage of the base station, the total traffic volume increases.

A wireless repeater applies the radio transmission mode, with short construction

period and effective cost. An optical repeater adopts optical fiber as transmission

medium, so the transmission loss is small and transmission distance is large, but

construction cost is greater than that of the wireless repeater.

The application advantage of the wireless repeater lies in low transmission

requirement. If you plant the optical fiber, there is no price advantage against the

construction of a micro cell base station. In this case, considering the network

quality, you are recommended to select the micro cell base station.

Compared with wideband repeater, a narrow band repeater has better

performance and provides better signal quality. However, the following problems

are still present in application:

The carriers of a narrow band repeater must outnumber the carriers

configured for the source base station; otherwise the repeater cannot

capture a channel.

The number of paths of many repeaters is set to 4, so the base stations

outnumber 4 carriers cannot work as the signal source.

For the base stations with radio frequency and frequency hopping, if the

frequencies in the frequency hopping set outnumber the paths selected by

the repeater, the conversation cannot be maintained.

When the channel number of the donor cell of the repeater changes, you

must adjust the channel number, otherwise the problems such as channel

assignment failure, call drop, and interference will occur.

The wideband repeater allows the base station to adopt frequency hopping, and

you do not have to adjust the channel number of the repeater after the channel

number of the donor cell changes if the channel number is within the bandwidth

of the repeater. However, the wideband repeater will amplify all the signals within

the band, so it causes great interference against other cells.

No matter whether the optical fiber or wireless repeater is applied, the sum of the

radius of the service area of the repeater and the distance between the repeater

and base station cannot break the TA limitation. For general base stations, the

distance between a repeater and the base station must be shorter than 35

kilometers.

The optical repeater can be used in the areas where the GSM radio signals

cannot reach and no space is left for a repeater. Because the transmission loss



of optical fiber is small and its bandwidth is wide, the optical repeater is quite

helpful for transmitting RF signals.

Either an omni antenna or a directional antenna can be selected for an optical

repeater according to the actual landforms. For an optical repeater, its

transmission does not have to be isolated from the reception. In addition, the

address of an optical repeater is easy to be decided. Generally, an optical

repeater is applied in the dead zones within countryside, highroads, touring

areas, factories, and urban areas.

In remote mountain areas and along highroads, you can also consider using a

solar energy repeater.

In conclusion, the repeater is used for the following purposes:

Enlarge coverage area and eliminate dead zones.

Strength the field strength and enlarge converge of the base stations in

urban areas.

Ensure the coverage along the highroads and tunnels.

Realize indoor coverage.

For the application of the wireless repeater and optical repeater, see Figure 5-8

and Figure 5-9.

Figure 5-8 Application of wireless repeater



Figure 5-9 Application of optical repeater

5.12.2 Working Principles of Repeater

I. Wireless frequency selection repeater

Figure 5-10 shows the working principles of a wireless frequency selection

repeater. The repeater receives the RF signals from the selected base station

(donor antenna) and amplifies and forwards the signals. The antenna receiving

the signals from the base station is called donor antenna, the other antenna is

called retransmission antenna.

Figure 5-10 Working principle of wireless frequency selection repeater



According to Figure 5-10, the working principles of a wireless frequency selection

repeater are as follows:

1) The low-noise power amplifier processes the signals (received by the donor

antenna) from downlink carriers.

2) The signals (900 MHz RF signals) are down converted into 71 MHz

intermediate frequency (IF) signals.

3) The IF filter (with a bandwidth of 200 KHz) amplifies the 71 MHz IF signals

and up converts the signals into the 900 MHz RF signals.

4) The retransmission antenna (service antenna) transmits the signals to the

coverage areas.

The uplink signals are also processed according to the previous procedures.

II. Wireless wideband repeater

Figure 5-1 shows the working principles of a wireless wideband repeater.

Figure 5-1 Working principle of wireless wideband repeater

The wireless wideband repeater works as the same way as the wireless

frequency selection repeater except the filter part. The bandwidth of the filter of

the wireless wideband repeater is fixed. Generally, it is 6M, 19M, or 25M.

III. Optical repeater

Figure 5-2 shows the working principles of an optical repeater.



Figure 5-2 Working principle of optical repeater

The difference between the optical frequency selection repeater and the optical

wideband repeater lies in the coverage end. The former adopts the frequency

selection components, but the later adopts the variable bandwidth options.

Compared with the wireless repeater, the optical repeater does require isolation

between donor antenna and retransmission antenna.

5.12.3 Repeater Network Planning

I. Repeater address selection

There is no special requirement on the repeater address selection except the

following items:

A repeater address must lie between the donor base station and the dead

zone, and the azimuth angle between the donor antenna and the

retransmission antenna cannot be smaller than 90°, as shown in the

following figure.

If the service antenna is a directional antenna, the repeater must be

installed about 200 to 500 meters beyond the dead zone. If the repeater is

installed within the dead zone, the coverage quality cannot reach the best,

as shown in the following figure.



When the repeater is used to coverage the dense residential areas at the

edges of the urban area, it cannot face the buildings, because great

penetration loss will be caused. In this case, the repeater must be installed

at the one side of the building, as shown in the following figure.

The areas to be covered must meet the requirement of line-of-sight

transmission.

The repeater address must ensure the received signal level required by the

repeater. Generally, the received signal level ranges from -50 dBm to -80

dBm.

No strong carrier whose channel number is the same as that of the donor

base station is present at near the repeater address.

The landforms, buildings, or towers where the donor antenna and

retransmission antenna can be installed. (The donor antenna must be

directed to the base station and the retransmission antenna must be

directed to the service area of the repeater. In addition, the isolation

between the two antennas must be greater than 170 dBc.)

II. Antenna selection

When selecting the antenna for a repeater, you must consider the followings:

Select the proper antenna gain according to the signals and coverage

condition



Do not adopt the omni antenna because the wireless repeater is affiliated to

the intra-frequency relay system, otherwise the system will perform self-

excitation.

The communication between the donor antenna and the donor base station

antenna is point-to-point communication, so you must select the antenna

with high gain or narrow horizontal beam width. For example, to reduce

interference, you can select the reflector antenna or the log-periodical

antenna.

Select retransmission antenna according to the characteristics of a

coverage area. For a large coverage area, you can select the general

directional antenna with high gain. For tunnel coverage, you can select the

Yagi antenna or the spiral antenna. For indoor coverage, you must select

the antenna specially designed for indoor use. No matter in what occasions,

you must control the transmit direction of the retransmission antenna to

prevent the retransmitted signals from feeding in the donor antenna.

The front-to-back ratio of the antenna must be as great as possible (it is

better to be greater than 30 dB) so that a better isolation between the donor

antenna and retransmission antenna can be ensured.

III. Requirements on antenna isolation

The isolation between repeater antennas depends on the host gain, but the host

gain cannot excel the isolation coefficient for self-excitation. According to the

requirements in GSM protocols 03.30, the isolation must be at least 15 dB

greater than the host gain. In actual project design, you can judge whether the

installation position meets the requirements on antenna isolation according to

on-site measurement.

According to the formulas calculating the antenna horizontal isolation introduced

in II. , the following formula can be deducted:

AH = 31.6 + 20 lgd – (Gt + Gr) dB (900 MHz)

AH = 37.6 + 20 lgd – (Gt + Gr) dB (1800 MHz)

Here, “d” indicates the distance between the donor antenna and retransmission

antenna, in the unit of meter. Gt and Gr indicate the antenna gain relative to the

major lobe in the direction of the two antennas. If the two antennas are back-to-

back installed, Gt and Gr indicate the front-to-back ratio of the antenna, as

shown in Figure 5-3.



Figure 5-3 Horizontal isolation of repeater antennas

The formula calculating the vertical isolation of repeater antennas is as follows:

Av = 47.3 + 40 logd dB (900 MHz)

Av = 59.3 + 40 logd dB (1800 MHz)

Figure 5-4 shows the vertical isolation.

Figure 5-4 Vertical isolation of repeater antennas

If the horizontal isolation and vertical isolation are present simultaneously, the

total isolation can be calculated by the following formula:

AS = (AV - AH) a/90 + AH, here AV indicates the vertical isolation; AH indicates the

horizontal isolation; and “a” indicates the antenna included angle.

Figure 5-5 shows the combination of vertical isolation and horizontal isolation.



Figure 5-5 Combination of vertical isolation and horizontal isolation

Figure 5-6 shows the antenna isolation when the donor antenna and

retransmission antenna are horizontally installed.

Figure 5-6 Antenna isolation when donor antenna and retransmission antenna

are horizontally installed

As shown in Figure 5-6, the donor antenna and retransmission antenna are

installed on the top of the building. Suppose the host gain is 100 dB, the isolation

between the two antennas can be 120 dB. If the front-to-back ratio of the donor

antenna and the retransmission antenna is 30 dB, when no barriers are present

between the two antennas, the requirement on the isolation can be met.

If the space loss of the signals between the two antennas is 60 dB, the horizontal

isolation distance can be obtained, that is, d = 26m.



During project implementation, you must select the antenna installation position

according to on-site measurement. You can use a signal source and a receiver

for the repeater. If the signal attenuation between the signal source and the

receiver reaches 60 dB, it means that the antenna installation position meets the

requirement on antenna isolation.

When installing the antenna for a repeater, you must pay attention to the

following items:

If the antennas are horizontally installed, the host of the repeater must be

installed between the donor antenna and the retransmission antenna (it

must be nearer to the donor antenna.)

A good isolation must be ensured regardless that the antennas are

horizontally or vertically installed. When they are horizontally installed, it is

better that there are some barriers lying between the donor antenna and the

retransmission antenna, because you do not have to particularly design a

large installation space to ensure antenna isolation in this case.

IV. Uplink and downlink balancce calculation

For a GSM repeater, the link balance is realized by four links, namely, the uplink

and downlink between the donor base station and repeater, and the uplink and

downlink between the repeater and mobile station.

This section employs the wireless repeater applied in outdoors as an example to

calculate the link balance. To simplify the calculation, we introduce the effective

donor path loss (EDoPL), which includes all the loss and gain from the output

end of the base station combiner or the input end of the multi-path coupler to the

input end of the repeater, as shown in Figure 5-7.

Figure 5-7 Link balance of repeater

The link balance is calculated according to the following two formulas:

For downlinks, Pbout - EDoPL + GRD - LRF + GRA - Lpass - Pmn = Pmin.



For uplinks, Pmout - Lpass + GRA - LRF + GRU - EDoPL - Pbn = Pbin.

Here,

Pbout indicates the output power of the base station.

Pmout indicates the output power of the mobile station.

GRD indicates the downlink gain of the repeater.

GRU indicates the uplink gain of the repeater.

LRF indicates the feeder loss of the retransmission antenna.

GRA indicates the gain of the retransmission antenna.

Lpass indicates the path loss the mobile stations from the repeater to the

service area.

Pbn indicates the attenuation margin of the mobile station.

Pbin indicates the receiving level of the base station.

Pmin indicates the receiving level of the mobile station.

BTSsens indicates the base station sensitivity.

MSsens indicates the mobile station sensitivity.

If the uplink EDoPL and downlink EDoPL are equal to the uplink path loss and

the downlink path loss from the repeater and mobile station, the attenuation

margin of the base station is equal to that of the mobile station. Therefore, if you

subtract the formula calculating uplink balance from the formula calculating

downlink balance, you can get Pbout - Pmout + GRD - GRU = Pmin - Pbin.

If the links are balance, the equation Pmin - Pbin = Dsens = MSsens- BTSsens is present.

In this case, the formula calculating link balance is Pbout - Pmout + GRD - GRU = Dsens.

Therefore, the Dsens is fixed after the base station equipments are selected.

Moreover, the output power of the base station and mobile station may be

decided in GSM system planning. As a result, to achieve the balance of the

whole links, you need to adjust the uplink gain and downlink gain of the repeater

only.

The followings employ the repeater system installed in outdoors as an example

to calculate the whole link balance.

For downlink budget of the outdoor repeater , output power of the transmitter

(+43dBm) – loss of the combiner (4dB) – EdoPL (90dB) = input power of the

repeater (-51dBm) + downlink gain of the repeater (80dB) = downlink output

power of the repeater (+29dBm) – feeder loss of the retransmission antenna

(3dB) + gain of the retransmission antenna (18dBi) – path loss of the repeater in

the coverage area (127dB) = input level of the mobile station (-83dBm) –

attenuation margin (20dBm) = the mobile station sensitivity (-103dBm).

Note:

To obtain the value of EDoPL, you can measure the input level of the donor

repeater and output level of the base station combiner first, and then obtain the



difference between the two, and the difference is the value of EDoPL. In addition,

the gain of the mobile antenna must be converted to 0 dBi.

For uplink budget of the outdoor repeater, output power of the mobile station

transmitter (+33dBm) – path loss of the repeater in the coverage area (127dB) +

gain of the retransmission antenna (18dBi) – feeder loss of the retransmission

antenna (3dB) = input power of the repeater (-79dBm) + uplink gain of the

repeater (80dB) = output power of the repeater (+1dBm) –EdoPL (90dB) = input

level of the base station (-89dBm) – attenuation margin (20dBm) = base station

sensitivity (-109dBm).

Note:

Because you do not have to consider the diversity function, the attenuation

margin on uplinks is the same as that on downlinks. According to the previous

link budget, the downlinks are restricted by the output power of the repeater, the

uplinks are restricted by the output power of the mobile station, and the noise

restricts the maximum gain (EDoPL-10 dB), so the link balance is present.

However, this is the most common situation. Actually, you must calculate the

margin for all links when installing or optimizing the repeater system. The latest

repeater supports the uplink gain and downlink gain to be set respectively.

Hereunder is an example.

There is a base station covering parts of a highroad. Its coverage radius is

about 20 km.

The measured signal strength at the edges of the base station cells is -

93dBm.

The microwave link tower on the top of the hill near the base station is

selected as the address of the repeater.

In the areas (including mountains) 350m below the top of the tower, the

received level of the mobile station is -71 dBm.

The log-periodical antenna with a gain of 18dBi and an azimuth angle of

35°is used as the donor antenna.

The antenna is installed at 15 meters under the tower top and faces the

base station.

If the previous conditions are present, the signals output by the repeater are -54

dBm. If a plane antenna with a gain of 17 dBi and a horizontal azimuth angle of

60 degrees is installed at the top of the tower and the antenna radiates to the

reverse direction of the donor antenna, the requirements on antenna isolation

can be met even if the gain of the repeater reaches 85 dB. In this case, the

output power of the repeater is 30 dBm. And the level of the signals in the areas



along the highroad which are 20 km beyond the tower can reach -90 dBm.

Therefore, the radius of the cell along the highroad is enlarged by 50%.

Note:

If a retransmission antenna is installed at the top of the tower, you must ensure

that the received signal level in the zero point filling areas near the tower.

V. Repeater output power control

When adopting a repeater, you must pay special attention to the effect of the

intermodulation products against the system. The intermodulation products of the

repeater depend on the number of the amplified carriers, the output power of

each carrier, and the linearity of the amplifier. For the linearity of the amplifier,

see Figure 5-8.

Figure 5-8 Linearity of the amplifier

Third order intermodulation will increase with output power due to the

nonlinearity of the amplifier. Therefore, you must control the output to a certain

degree to ensure that that the indexes on third order intermodulation meet the

requirements. The following formula shows the relationship between the output

power of each carrier of the repeater and the requirements on third order

intermodulation.

Po = IP3 + (PIMP/2) +10 lg (N/2)

Here,

Po indicates the output power of each carrier (dBm)



IP3 indicates the third order section of the amplifier (dBm)

PIMP indicates the level of the third order intermodulation (dBc)

N indicates the number of carriers

If the third order section of the amplifier of a typical repeater is 50 dBm, and the

intermodulation level must be lower than -45 dBc according to the requirement of

the wireless communication institutes in Britain, the relationship of the output

power of each carrier and the number of carriers is listed in Table 5-1.

Table 5-1 Relationship of output power of each carrier and the number of

carriers of a repeater

The number of carriers The output power of each carrier (dBm)

2 +24.5

4 +21.5

10 +20.5

20 +17.5

VI. Repeater gain setting

The gain of the early repeaters must be set manually, but the latest gain of the

latest repeaters can be automatically set. For the repeaters whose gain is set

manually, the sum of the repeater gain and the protection margin must be equal

to or smaller than the repeater isolation; otherwise, the self-excitation of the

repeater will be caused. Here the repeater isolation indicates the isolation

between the donor antenna and the retransmission antenna of the repeater.

Generally, the protection margin ranges from 10 dB to 15 dB.

VII. Repeater adjacent cell planning

The coverage areas of a repeater may overlap other donor cells, so you must

configure the corresponding adjacent cell relationship for the repeater to ensure

normal handover. In addition, you must pay attention that the frequencies in the

coverage areas of the repeater and that in the donor cells cannot be the same

frequency and neighbor frequency.

VIII. Effect of delay processing against repeater planning

If only one repeater cannot fully cover an area (such as a narrow and long

tunnel), you can use several cascaded repeaters to provide the coverage. The

selection of the address and antenna for the repeater of each level is the same

as that for a single repeater.



However, the repeater will amplify the same frequency and it takes some time for

the repeater to process the signal, so there is a delay for each signal segment. If

the delay is greater than the time for the GSM system to identify the time

window, the intra-frequency interference will occur. Therefore, you must consider

the effect of the delay when adopting cascaded repeaters, because the delay will

also accelerate the time dispersion and shorten the coverage distance.

If adopting the optical repeater, you must consider that the transmission speed of

the signals in optical fibers is 2/3 that of in free space, namely, if the extension

cell technology is not used, the maximum transmission distance of the signals in

optical fiber is 35 km multiplies 2/3 (about 23.3 km) due to the restriction on

transmission delay.

In addition, if one of three synchronous cells adopting the optical repeater, the TA

of two cells will be different due to the difference of transmission mode and rate.

In this case, the synchronous handover failure will occur. Therefore, you must

adopt the asynchronous handover to obtain the TA of a new cell, which works as

the handover target cell.

The delay processing varies with repeater types. Some take 2 to 3 μs and some

takes 5 to 6μs. In a GSM system, the delay of two signals cannot be greater than

16μs. For the effect of repeater delay processing against time dispersion, see

Figure 5-9.

Figure 5-9 Effect of repeater delay processing against time dispersion

In Figure 5-9, the distance between point A and the repeater “d” is 2.1km. The

delay for the mobile station at point A to receive the signals from the repeater

and the cell is as follows:

(2.1km + 2.1km)/c (light speed) + 3μs = 14μs + 3μs = 17μs > 16μs.

In this case, the intra-frequency interference may be present. If the difference of

the levels of the two signals is equal to or lower than 12 dB, the conversation

quality will be affected.

The time dispersion will cause intra-frequency interference, and the time

dispersion is caused by the overlap of the signal source cell and the repeater



coverage area. Therefore, you must select the signal of the secondary cells in

the coverage areas of the repeater instead of the signals of the major service cell

as the source signal of the repeater. In this case, the time dispersion caused by

overlap can be avoided.

IX. Effect of background noise against repeater planning

Suppose that the maximum received noise level allowed by the base station is

DN, if the uplink background noise level of the repeater host is too great, the base

station channels will be congested when the noise level at the base station is

greater than DN. However, how to set the repeater without affecting the base

station? They are introduces as follows.

If the following assumptions are present:

The transmitted signal strength of the base station is Tb.

The received signal strength of the base station is Rb.

The received downlink signal strength of the base station host is Dr.

The transmitted uplink signal strength of the base station host is Ut.

In this case, the path loss between the base station and the repeater is Tb-Dr, so

Rb = Ut – (Tb-Dr). As a result, if the repeater does not affect the base station, Rb <

DN, so the following two inequities are present:

Ut – (Tb - Dr) < DN

Ut < Tb-Dr + DN

According to the previous analysis, the repeater does not affect the base station

if the uplink background noise level output by the repeater host is lower than (Tb-

Dr+DN). From this perspective of review, the background noise must be

particularly emphasized in repeater planning because it is easier to bring

interference than other types of base stations.

X. Specifications of wireless repeaters

For the specifications of some repeaters in commercial use, see Table 5-1.

Table 5-1 Specifications of parts of repeaters in commercial use

Source &

Reference

Type/band

/channel

selective

Power (W)

Downlink

(Uplink)

Gain (dB)

Downlink

(Uplink)

Noise

Figure

(dB)

Downlink

(Uplink)

3rd order

intercept

(dBm)

Downlink

(Uplink)

No. of

channels

Size

(mm)

AFL



GSM

900MHz

Band 1, 5, 10,

20, 25

30, 50, 80,

95 (30, 50,

80, 95)

4.5 (4.5) 40, 47,

50, 54

(40, 47,

50, 54)

N/A 460x

550x

220

(10W)

GSM

1800MHz

Band 1, 5, 10,

20,25

30, 50, 80

(30, 50,

80)

< 4.5

(<4.5)

40, 47,

50, 54

(40, 47,

50, 54)

N/A 460x

550x

220

(10W)

GSM Channel 1, 5, 10,

20,25

30, 50, 80

95, (30, 50,

80, 95)

6.0 (6.0) 40, 47,

50, 54

(40, 47,

50, 54)

1, 2, 4, 8 460x

550x

220

(10W)

GSM

1800MHz

Channel 1, 5, 10,

20,25

30, 50, 80

95, (30, 50,

80, 95)

< 6.0

(< 6.0)

40, 47,

50, 54

(40, 47,

50, 54)

1, 2, 4, 8 460x

550x

220

(10W)

Allgon

AR 1200

GSM

900MHz

Band 50-90 5 52 N/A 440(W)

530(H)

174(D)

AR 120

GSM

900MHz

Channel 24 dBm

(20) dBm

40-60 < 6.0 2 230(W)

285(H)

120(D)

AR 2100

GSM

1800MHz

Channel 33 dBm

(2-channel)

30 dBm

(4-channel)

50-90 5 1-4, 5-8 440(W)

530(H)

174 or

240(D)

Mikom



MR 340 Channel 32 dBm

(2-channel)

28 dBm

(4-channel)

85-89

(2-channel)

82-86

(4-channel)

6-8 2-channel

modules

per

cabinet

[2]

425(W)

255(H)

110(D)

5.13 Conclusion

Network planning is the foundation of a mobile communication network,

especially the wireless parts in a mobile communication network costs great and

is of vital importance to network quality, so you must make a good planning at

earlier stage, which is helpful for network expansion and service update in the

future.

Network planning requires engineers to analyze coverage, decide network

layers, and analyze traffic based on relative technologies and parameters, and

finally output the results of RF planning, including base station layout and scale.

RF planning, as well as the application of cell parameters, determines the cell

coverage. The cell coverage must be properly designed so that the mobile

station can always enjoy the best service at the best cells. In addition, the cell

coverage must be designed in a way conducive to network capacity expansion.

This chapter also introduces the solutions to dual-band network, indoor

coverage, tunnel coverage, and so on. Last, this chapter introduces the repeater

application.


Documents

GSM Radio Network Planning