Frequency Planning

GSM Frequency Planning

ZTE university

Objectives of this course

To master the basic concepts of GSM frequency planning

To master different kinds of frequency reuse methods and frequency reuse principles

To know automatic frequency planning To master the principles and methods of neighbor cell

planning To master the principles and methods of BSIC planning To master common anti-interference technologies

Contents

An overview of frequency planning

Frequency reuse methods

Automatic frequency planning

Neighbor cell planning

BSIC planning

Anti-interference technologies

The status and functions of GSM frequency planning in radio

network planning Influences over the network capacity and the base station configuration

Interference prediction and emulation

The status and functions of GSM frequency planning in network

optimization Reduce interferences, improve C//I, and improve call quality

Optimize frequency resources

Enhance the operation value

The importance of GSM frequency planning One of the important items of network planning

One of the important measures of network optimization

Functions of frequency planning

Frequency bands of GSM system

GSM

system

Uplink/

MHz

Downlink/

MHz

Bandwidth

/ MHz

Duplex

separation/

MHz

Channel

number

GSM900 890 ~ 915 935 ~ 960 2 ×25 45 124

EGSM900 880 ~ 915 925 ~ 960 2 ×35 45 174

GSM1800 1710 ~

1785

1805 ~

1880

2 ×75 95 374

GSM1900 1850~1910 1930~1990 2 ×60 80 299

Channel numbers of GSM system

Channel separation Each carrier frequency occupies 200 KHz bandwidth,

adopts TDMA, and has 8 physical channels. Channel configuration

GSM900MHz frequency band ： fu(n)=890.2MHz+(n-1)*0.2MHz fd(n)= fu(n)+45MHz

GSM1800MHz frequency band ： fu(n)=1710.2MHz+(n-512)*0.2MHz fd(n)= fu(n)+95MHz fu(n) ： Uplink frequency, sent by MS, received by a base

station fd(n) ： Downlink frequency, sent by a base station, received

by MS

Regular hexagon1

Coverage areas

Radio cluster1

Regular hexagon n

.

.

.

Radio cluster m

.

.

.

1) Radio clusters should be contiguous.

2) In adjacent radio clusters, the center-to-center distance between any two co-channel reuse areas should be the same.

Principles for the formation of cellular structure

Radio clusters should be contiguous.

In adjacent radio clusters, the center-to-center distance between any two co-

channel reuse areas should be the same.

Principles for the formation of cellular structure

Definition of adjacent channel interference

Co-channel interference C/I When different cells use the same frequency, another

cell may interfere with the serving cell. This is called C/I, that is, their ratio.

According to GSM specifications, C/I should be more than 9dB (C/I>9dB). In a project, 3dB margin will be added, so C/I>12dB is required.

Adjacent channel interference C/A: Under the frequency reuse mode, an adjacent channel

may interfere with the channel used by the serving cell. The ratio of these two signals is C/A.

According to GSM specifications, C/A should be more than -9dB (C/A>-9dB).

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BCCHi

cellown

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I

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Calculation of carrier-to-interference ratio (C/I) of co-channel/adjacent channel

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When the frequency is reused in

a normal way:

The distance between any two

adjacent areas which use the

same frequency should be D.

Therefore, any three adjacent

areas which use the same

frequency form a regular

triangle.

From the picture, it can be seen

that:

There are 6 interfering

resources of the first circle,

and there are 12 of the

second circle.

Co-channel interference model

)/( BICP

C/I(dB)

Gauss distribution of

probability density

Co-channel interference protection ratio threshold B

Co-channel interference

protection margin Zp

The shadow area means

interference probability

C/I (dB) probability density

distribution

Co-channel interference model

Co-channel interference probability

According to the interference model, the C/I ratio of MS B to MS A is as follows:

So when call drop

will occur.

A

B

C

D

d2

d1

Cell 2

Cell 1 d2

d1

dBd

dkdB

I

C9log'2)(

2

1

69.11

2 d

d

Adjacent channel interference

Near—far interference

Collection of system data

Check the completeness of data

The planning is based on the decided frequency reuse mode.

BCCH planning

Prediction of system interference analysis

Is the result satisfies the planning requirements?

Data review

The output of a report

Handover planningTCH planning BSIC planning HSN planning

Procedures of frequency planning

Contents





BSIC planning


Frequency reuse

Frequency reuse: It means that the same frequency is reused in a digital

cellular system. Usually the limited frequency is divided into several groups, so each group is to be used by an neighbor cell.

Several concepts of frequency reuse

Frequency reuse The origin is the limited frequency resources. The same group of frequency covers different areas. The reuse

coefficient indicates the reuse frequency.

Co-channel frequency reuse distance The areas which use the same frequency should keep a distance

from each other. This distance is called co-channel frequency reuse distance D.

Interference protection ratio Co-channel interference protection ratio C/I≥9dB. In a project, 3dB

margin will be added, so C/I>12dB is required. Adjacent channel interference protection ratio C/I ≥ － 9dB. In a

project, 3dB margin will be added, so C/A>-6dB is required. Adjacent channel protection ratio of 400KHz C/I≥ － 41dB

Frequency reuse method

Standard packet frequency reuse technology Multi-reuse pattern Tighter frequency reuse technology Multi-layer of networks technology Concentric circle technology Construction of dual band network

(GSM900/1800)

dB

dBI

C

18

)2.7(2)8(

2log10

)(

44

4

18dB>12dB

4×3 reuse

4×3 reuse Definition: “ 4×3” reuse

divides frequency into 12 groups, which will be distributed to 4 sites alternatively. In other words, each site can use 3 groups of frequency.

C/I

4×3 reuse

4×3 reuse example 1 Suppose the carrier has 7.2M bandwidth, 36 frequency.

4×3 frequency reuse is shown as follows:

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

1 2 3 4 5 6 7 8 9 10 11 12

13 14 15 16 17 18 19 20 21 22 23 24

25 26 27 28 29 30 31 32 33 34 35 36

4×3 reuse

An example of 4×3 reuse

The phenomenon that adjacent base stations use the same frequency does not exist. However adjacent channel opposite cells still exist.

Pattern 1 ： D1---A2 ； Pattern 2 ： D2---A3 ； Pattern 3 ： D1---A2 ； Pattern 4 ： D2---A3 ； Pattern 5 ： D3---A1 ； Pattern 6 ： D3---A1

4×3 reuse

4×3 reuse example 2 Suppose the carrier has 7.2M bandwidth, 36 frequency.


A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

1 2 4 3 5 8 7 6 9 11 10 12

13 14 16 15 17 20 19 18 21 23 22 24

25 26 28 27 29 32 31 30 33 35 34 36

4×3 reuse

An example of 4×3 reuse

Except 1, 4, other patterns have co-channel opposite cells:

Pattern 2: C1---A2;

Pattern 3: B2---A3;

Pattern 5: C1---A2; B2---A3; D3---A1;

Pattern 6: D3---A1

dB

dBI

C

3.13

)57.5(2)7(2

2log10

)(

44

4

13.3dB>12dB

3×3 reuse

3×3 reuse “3×3” reuse divides

frequency into 9 groups which will be distributed to 3 sites alternatively. In other words, each site can use 3 groups of frequency.

C/I

A1 B1 C1 A2 B2 C2 A3 B3 C3

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

3×3 reuse

An example of 3×3 reuse Suppose the carrier has 7.2M bandwidth, 36 frequency.


A1

A2

A3

B1

B2

B3

C1

C2

C3

C1

C2

C3

B1

B2

B3 A1

A2

A3

A1

A2

A3 C1

C2

C3

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B2

B3

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A2

A3

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B3

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C2

C3 A1

A2

A3

A1

A2

A3 B1

B2

B3

C1

C2

C3

3×3 reuse

An example of 3×3 reuse Pattern 1: There are no adjacent channel cells. Pattern 2:

C1---A2; C2---A3; C3---A1

9.43dB<12dB

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A3

A1

A2

1×3 reuse

1×3 reuse “1×3” reuse divides frequency

into 3 groups, which will be distributed to 1 site alternatively. In other words, each site can use 3 groups of frequency.

C/I

MA1 1 4 7 10 13 16 19 22

MA2 2 5 8 11 14 17 20 23

MA3 3 6 9 12 15 18 21

1×3 reuse An example of 1×3 reuse

Suppose the carrier has 7.2M bandwidth, 36 frequency. BCCH adopts 4×3 reuse, TCH adopts 1×3 frequency reuse + synthesized hopping, maximum Fraction Load is 50%, and one separation frequency is used between BCCH and TCH. Suppose CA of TCH is 1-23.

It should be guaranteed that there is no adjacent channel of MAIO for 3 cells under one base station.

MAIO should be the same for cells on the same direction of a base station.

HSN should be the same for 3 cells under the same base station. HSN should be different for adjacent base stations. On the other hand,

the distance between base stations of the same HSN should be as far as possible (HSN reuse).

Reuse coefficient 6

6 MHz bandwidth

BCCH reuse coefficient 12

Reuse coefficient 9

Suitable for micro cells

MRP

According to MRP technology (Multiple Reuse Pattern), a frequency band is divided into several orthotropic BCCH frequency bands and several TCH frequency bands. Each frequency band works as an independent layer. Different layers adopt different frequency reuse patterns, which become tight to each other from layer to layer.

BCCH adopts the 43 reuse pattern or a higher reuse coefficient.

Hierarchical planning is adopted for BCCH and TCH, and micro cell frequency is reserved.

BSIC decoding is not relevant to TCH load,

which will not influence BSIC decoding.

Simplify the configuration of a neighbor list.

Adopts anti-interference technologies like DTX,DPC,HP and so on for TCH carrier frequency.

Since each layer is independent, it is easy for separate maintenance.

Advantages of MRP

MRPMRP

MRP

An example of MRP Suppose the carrier has 7.2M bandwidth, 36 frequency

which are from 60 to 95. On basis of MRP, 36 carrier frequency falls into four groups, that is, 12/9/8/7. For details, refer to the following table.

Channel

types

Logical channel TCH1 service

channel

TCH2 service

channel

TCH3 service

channel

Channel

number

60 61 62 63 64 65

66 67 68 69 70 71

72 73 74 75 76 77

78 79 80

81 82 83 84 85

86 87 88

89 90 91 92

93 94 95

60

64

68

6266

7063

67

7161

65

69

7275

78

7376

7972

75

787477

80

8991

93

9092

94 9092

9489

91

93

8183

85

8284

8682

84

8183

85

86

1) BCCH 4 3 2) TCH1 3 3

4) TCH3 2 3 3) TCH2 2 3

MRP

60728189

64 75 8391

85 93 6878

62738290

66 76 8492

70808594

63 7282 90

67 75 92 84

71 8678 94

65 77 8391

61748189

85936980

MRP

Concentric circle

An ordinary cell is divided into two circles: an underlayer and an overlayer.

Ordinary concentric circleIt helps to decrease the transmission power of the underlayer. The handover is based on path loss and TA.

Intelligent concentric circleThe underlayer and the overlayer have the same

transmission power. The handover is based on C/I.

•The call is established on the overlayer.•When the measured C/I is larger than Good C/I threshold, the overlayer is switched into the underlayer.•When measured C/I is smaller than Bad C/I threshold, the underlayer is switched into the overlayer.

同心圆Concentric circle

Two ways for the realization of concentric circle

Ordinary concentric circle

It does not need to change the network structure.

Some special handover algorithms need to be

added. However, generally speaking, it is easy to

be realized.

There are no special requirements for the handset.

The improvement of capacity is limited.

Usually, the increase is 10-30%.

The improvement of capacity is related to the

traffic distribution. Since the power of the underlayer

is small, it is not easy for it to absorb the indoor traffic.

It is suitable for the outdoor traffic which is densely

distributed around the base station.

Intelligent concentric circle

It can make use of the present site, and there is little

change of the network.

C/I measurement and estimation, and some special

handover algorithms need to be added.

There are no special requirements for the handset.

The improvement of capacity is remarkable.

The increase is from 20% to 40%.

The improvement of capacity is related to the

distribution of traffic. It is related to the traffic

absorbed by the underlayer.

It is suitable for cells of intense traffic, which are

near the base station.

Concentric circle

Necessity

Newly constructed GSM network Not many subscribers;

More subscribers Channel congestion

Capacity expansion of the carrier frequency;

More subscribers Traffic congestion and

maximum carrier frequency configuration under the

present frequency resources Cell split

Features

Each time when splitting occurs, the radius of the base

station coverage will become half of the original one.

The number of base stations is 4 times of the original number.

The splitting is not unlimited.

Cell split

Procedures for the choice of frequency reuse pattern The configuration of maximum carrier frequency of a base station is

based on the present frequency reuse pattern of the GSM network planning area, and the allowed bandwidth.

The maximum traffic which can be offered by each base station is based on the number of voice channel, the indicators of call congestion rate, and the check of Erlang B table.

The minimum base station radius can help to calculate the maximum traffic intensity requirements which can be satisfied by the base station under the present frequency reuse pattern.

Then make a comparison of the data mentioned above and the traffic intensity required by the areas of high traffic intensity. If the former is smaller than the latter, it indicates that the capacity required by subscribers can not be satisfied with the present frequency reuse pattern. Tighter frequency reuse pattern needs to be adopted, and the procedures mentioned above need to be repeated.

Finally, the frequency reuse pattern of the network planning area is determined.

Multi-layer netw

ork

BCCH layer

TCH1 layer

TCH2 layer

TCHn layer

TCHn+1 layer

TCHn+2 layer

900 micro cell

Overlay

Underlay

Frequency-

hopping

group

Frequency-

hopping

group

MRP bands

900 macro cell 1800 macro cell

1800 micro cell

Dual band

network

“ 4×3”reuse

Dual-layer reuse pattern

Multi-layer reuse pattern

Evolution of frequency reuse pattern

Main principles for frequency planning

Under the same base station, no co-channel/adjacent channel is allowed.

Co-channel should be avoided for adjacent base stations. Both co-channel and adjacent channel should be avoided for opposite cells.

As to frequency-hopping of radio frequency, HSN of cells under the same base station should be the same. However, adjacent channel for MAIO should be avoided.

The same BCCH and the same BSIC should be avoided within a short distance.

If a high mountain is located between base stations, it should not be treated as an neighbor cell. However, if a large body of water exists between base stations, it should be treated as an neighbor cell.

When frequency-hopping occurs, a part of frequency band of BCCH should be reserved to adopt 4×3 reuse pattern or a higher reuse pattern.

In consideration of geographical factors, if a site is constructed on a high mountain, it should be configured with independent frequency.

GSM900 macro

GSM1800 macro

GSM900 micro GSM1800 micro

P-cellP-cell

Multi-layer network technology

Contents





BSIC planning



Automatic frequency planning makes use of some planning software

to realize automatic frequency allocation of carrier frequency, and

allocation of color code. Its purpose is to reduce the frequency

collision rate of the whole network.

Automatic frequency planning makes use of some planning software

to realize automatic frequency allocation of carrier frequency, and

allocation of color code. Its purpose is to reduce the frequency

collision rate of the whole network.

The planning software calculates automatically to allocate frequency for carrier frequency in the most reasonable way. The calculation is based on a series of factors, e.g., interference relationship, handover relationship, geographical distribution, and so on.

The planning software calculates automatically to allocate frequency for carrier frequency in the most reasonable way. The calculation is based on a series of factors, e.g., interference relationship, handover relationship, geographical distribution, and so on.

Automatic frequency planning tools available in ZTE now

目前主要有两类：目前主要有两类：

ZTE will put forward some automatic frequency planning /optimization tools which are researched and developed by itself ——CNP/CNO-G.

ZTE will put forward some automatic frequency planning /optimization tools which are researched and developed by itself ——CNP/CNO-G.

Automatic frequency planning tools

Introduction of tools Factories

CNP ① An automatic frequency planning software based on

simulation prediction.

② The data is based on the path loss value of simulation

prediction.

ZTE

AIRCOM AIRCOM

AFP

① It is based on the C/I information of MR data measured

and reported by handsets of the present network.

② Both the simulation data and handover data can be

referred to.

ACTIX

CNO-G① Both the information of geographical distribution and

antenna azimuth is referred to.ZTE

AIRCOM/CNP automatic frequency planning algorithm

The principles for the realization of Aircom/CNP are similar: The simulation of path

loss of signals during the transmission is based on some engineering parameter

information, e.g., 3D digital map, longitude and latitude, antenna information and so

on. The whole replanning area is rasterized. In each raster, the predicted level of each

cell is calculated for C/I prediction. On basis of the data, the interference matrix is

generated so as to carry out the automatic frequency planning according to the matrix.

The principles for the realization of Aircom/CNP are similar: The simulation of path

loss of signals during the transmission is based on some engineering parameter

information, e.g., 3D digital map, longitude and latitude, antenna information and so

on. The whole replanning area is rasterized. In each raster, the predicted level of each

cell is calculated for C/I prediction. On basis of the data, the interference matrix is

generated so as to carry out the automatic frequency planning according to the matrix.

AIRCOM/CNP data are not valid enough, since the data comes from simulation prediction, which is limited to the accuracy of digital map, and can not comprehensively reflect the real subscriber experience. However, this tool is suitable for newly constructed network. That’s because the newly constructed network has no MR data, and C/I value can only be obtained from simulation prediction.

AIRCOM/CNP data are not valid enough, since the data comes from simulation prediction, which is limited to the accuracy of digital map, and can not comprehensively reflect the real subscriber experience. However, this tool is suitable for newly constructed network. That’s because the newly constructed network has no MR data, and C/I value can only be obtained from simulation prediction.

AFP automatic frequency planning algorithm

AFP data mainly comes from C/I data reported by handsets of subscribers, which is

specific and accurate.

Pair relationships of cells of the whole network can be obtained through BA

scheduling. Besides, the following factors can also be taken into consideration, e.g.,

handover relationship of the present network, simulation prediction relationship of

newly constructed sites, customized protection relationship of VIP sites and so on.

Different kinds of data can be considered in an integrated way. For details, please refer

to Special Subject Manual for GSM Network P & O – MR-based Tool Application of AFP.

AFP data mainly comes from C/I data reported by handsets of subscribers, which is

specific and accurate.

Pair relationships of cells of the whole network can be obtained through BA

scheduling. Besides, the following factors can also be taken into consideration, e.g.,

handover relationship of the present network, simulation prediction relationship of

newly constructed sites, customized protection relationship of VIP sites and so on.

Different kinds of data can be considered in an integrated way. For details, please refer

to Special Subject Manual for GSM Network P & O – MR-based Tool Application of AFP.

Interference relationship

(MR)

Interference relationship

(MR)

Handover relationship

(Handover)

Handover relationship

(Handover)

Prediction relationship

(Prediction)

Prediction relationship

(Prediction)

Planning principles

(Strategy)

Planning principles

(Strategy)

Tools

(AFP)

Tools

(AFP)

Configuration of penalty value

(Priority Setting)

Configuration of penalty value

(Priority Setting)

PlanPlan

Differences between the automatic frequency planning tools

① The accuracy of data: AFP is based on real subscriber data of the

network, while AIRCOM/CNP is based on simulation prediction.

② A rich variety of data: For AFP, it is possible to make a

comprehensive consideration of data and pair relationships of cells.

Bedsides, the requirements for antenna parameters are not strict.

However, for AIRCOM/CNP, the data only comes from simulation

prediction. Besides, it largely depends on the propagation model,

antenna information, accuracy of digital map, and so on.

① The accuracy of data: AFP is based on real subscriber data of the

network, while AIRCOM/CNP is based on simulation prediction.

② A rich variety of data: For AFP, it is possible to make a

comprehensive consideration of data and pair relationships of cells.

Bedsides, the requirements for antenna parameters are not strict.

However, for AIRCOM/CNP, the data only comes from simulation

prediction. Besides, it largely depends on the propagation model,

antenna information, accuracy of digital map, and so on.

Advantages of automatic frequency planning

① Time-saving & labor-saving: Frequency replanning can be realized by the machine,

because of which people are freed from the manual planning which is troublesome

and time-consuming. Especially for a large network, this method takes greater effects.

② Objective and accurate: Subjective factors are avoided to the fullest extent. The

advantages of AFP’s network model and its compatibility with the present network

can guarantee the quality of the planning results.

Suppose there are 3 BSC, 1700 carrier frequency, and the frequency of the whole network needs to be modified, the workload for this is calculated as follows:

　 Manual planning

Automaticplanning

Efficiency evaluation (according to staff

needed)

3 people 1 person

Efficiency evaluation (according to time)

More thanone week

1-3 days

Accuracy 50% 90%

No matter how large the network is, only 1-2 engineers are needed at the headquarters to form a plan. So the larger the network is, the more advantages MR solution will show.

Contents





BSIC planning


Main principles for neighbor cell planning

No co-channel or same BSIC is allowed between the serving cell and neighbor cells, or between the neighbor cells themselves which belong to the same serving cell.

No co-channel is allowed between the serving cell and neighbor cells.

The configuration of neighbor cells is not without any limitation. The default number of neighbor cells is no more than 31. According to the engineering experience, it is suggested that the neighbor cells should be less than 24.

Except for special conditions, usually, two-way neighbor cell relationship is required.

Principles of neighbor cell planning for urban areas

Principles of neighbor cell planning for suburban areas

Types of unreasonable neighbor cell planning

Unidirectional neighbor cellsToo many neighbor cellsToo few neighbor cells

Results

Call dropHandover failure

Frequent handoverIslanding effect

Abnormal overshooting handoverUnbalanced traffic

Reduction of handover accuracy……

Unreasonable neighbor cell planning

Contents





BSIC planning


Definition and value range of BSIC

Definition of BSIC NCC ： Network Color Code BCC ： Base transceiver station Color Code

Value range of BSIC NCC ： 0 ～ 7 BCC ： 0 ～ 7

Functions of BSIC

Principles for BSIC planning

Contents





BSIC planning


Anti-interference measures

If the activity factor of DTX is p, the gain is calculated as follows:

pI

C

pI

CdBIC log10log10log10)(/

DTX

Base Band HoppingBase Band Hopping

Synthesized HoppingSynthesized Hopping

Frequency Hopping

基带跳频Base band hopping

射频跳频Synthesized Hopping

HSN Hopping Sequence Number

MAIO

Mobile Allocation Index Offset

MA List Mobile Allocation List

Fractional load

It describes the frequency hopping tracks.

It describes the frequency where TRX of each

cell starts frequency hopping.

It describes the list of frequencywhich have frequency hopping

It describes the load relationship between the number of carrier frequency taking part in

frequency hopping and the number of frequency in MA.

Several important parameters related to frequency hopping

Benefits of frequency hopping

Frequency diversity – Against Rayleigh fading

Benefits of frequency hopping

Interference diversity – equalization of interference

DPC

With DPC, BTS will not work with the maximum transmission power unless the MS is located at the cell boundary.

The location of interfering MS is all about probability, which is especially true under the circumstance of frequency hopping. Suppose the factor of DPC is p:

Documents

Frequency Planning