78899587 Frequency Planning

HUAWEI TECHNOLOGIES CO., LTD. All rights reserved

www.huawei.com

Internal

OMF 007001

Frequency Planning

ISSUE1.4

HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved

Chapter 1 Chapter 1 Frequency planningFrequency planning

Chapter 2 Chapter 2 Tight frequency reuseTight frequency reuse

Chapter 3 Chapter 3 Frequency hoppingFrequency hopping


Content of Frequency planning

� Frequency resource of GSM system

� Requirement for interference and carrier-to-interference ratio

� Signal quality grade coding

� Concept of frequency reuse

� 4*3 frequency reuse


GSM 900 :

GSM 1800 : 1710 1785 1805 1880

Duplex distance : 95 MHz

890 915 935 960

Duplex distance : 45 MHz

Frequency Resource of GSM System


Frequency Band Configuration

� GSM900:

�BTS receiver (uplink ): f1 (n) =890.2+ (n-1)*0.2 MHz

�BTS transmitter (downlink ): f2 (n) =f1 (n) +45 MHz

� GSM1800:

�BTS receiver (uplink ): f1 (n) =1710.2 + (n-512) * 0.2 MHz

�BTS transmitter (downlink ): f2 (n) =f1 (n) +95 MHz


All useful signals carrierAll useless signals interference=

GSM standard: C / I >= 9 dB

In practical projects: C / I >= 12dB

Useful signal Noise from environment

Other signals

Requirement for Interference and Carrier-to-Interference Ratio

C/I =


Effect of Interference

� Decrease of signal quality

�Bit error

− Recoverable: channel coding, error correction

− Irrecoverable: phase distortion

�System interference model

− Unbalanced: uplink interference ≠ downlink interference

− Asymmetrical: the interference is different at the MS and

BTS ends


RXQUAL Mean BER BER range

class (%) from... to

0 0.14 < 0.2%

1 0.28 0.2 ... 0.4 %

2 0.57 0.4 ... 0.8 %

3 1.13 0.8 ... 1.6 %

4 2.26 1.6 ... 3.2 %

5 4.53 3.2 ... 6.4 %

6 9.05 6.4 ... 12.8 %

7 18.1 > 12.8 %

Fairly good

Intolerable

Good

Acceptable

Signal Quality

� Receiving quality (RXQUAL parameter)

� Level of receiving quality (0 ... 7)

�Bit error rate before decoding and error correction


{fi,fj..fk}

{fi,fj..fk} {fi,fj..fk} {fi,fj..fk}.. ..

Macro-cell system

d

Micro-cell system

Concept of Frequency Reuse


The Reason of Frequency Reuse

� Frequency resource is limited. If there is 8MHz frequency

resource, 8 MHz = 40 channels * 8 timeslots = 320

==> max. 320 users can access the network at the same

time.


Looser reuse

Higher frequency reuse

efficiency, but interference

is serious. More technique

Is needed.

Tighter reuse

0 10 20

Little interference, but frequency

reuse efficiency is low.

Reuse Density�Reuse density is the number of cells in a basic reuse

cluster.

− 4*3：12

− n*m：n*m

− n: BTS number in a basic reuse cluster

− m: Frequency group number in a BTS


[fn]

[fn]

D

[fn]

R

Reuse of a frequency causes the co-channel interference

Problem of Frequency Reuse


Interference (C/I) Estimation

( )6

1γ

−=

q

I

C

1/2

q = D/R = ( 3 k )


R

D

This old-fashioned frequency distribution

mode is not recommended

Frequency Reuse Patterns

�Purpose: to minimize the interference in the whole network with

the final frequency allocation plan

�Theoretically

− Regular hexagon cell

− Regular network distribution

− Cell cluster

− Multiplexing distance

D = R *sqrt(3*K)


A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3 A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

4*3 Frequency Reuse


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

34 34 35 36 37 38 39

40 41 42 43 44 45 46 47 48 49 50 51

52 53 54 55 56 57 58 59 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

Illustration of Frequency Allocation of 4*3 Frequency Reuse






Tight Frequency Reuse Technology

� Multi-layer reuse pattern

� Underlaid and overlaid cell

� 1*3

� 1*1


Multi-layer Reuse Pattern


BCCH: n1

TCH1: n2

TCH2: n3

…

TCHm-1: nm

n1 ≥n2≥n3 ≥n4 ≥...... ≥ nm

And n1+n2+...+nm=n

Multi-layer Reuse Pattern


Multi-layer Reuse Pattern Frequency Allocation

� Suppose that the available frequency carrier is 10MHZ, channel

number is 46～94, the Multi-layer reuse pattern should be:

RC type Allocated

frequencies

Number of available

frequencies

BCCH 46~57 12

TCH1 58~66 9

TCH2 67~74 8

TCH3 75~82 8

TCH4 83~88 6

TCH5 89~94 6


BCCH TCH1 TCH2 TCH3 TCH4

{f1,f3,f5...f23}

{f1,f2,f3,f4,f5...f40}

{f2,f4..f22,f24...f40}

Multi-layer Reuse Pattern Frequency Allocation


cap NBW

re use

i

i

.=−

∑

Advantages of Multi-layer Reuse Pattern

� Capacity increase when reuse density is multiplied:

�Supposing there are 300 cells

�Bandwidth: 8 MHz (40 frequency)

� Normal 4*3 reuse: reuse density=12

� ==> network capacity = 40/12 * 300 = 1000 TRX

� Multiple reuse:

�BCCH layer: re-use =14, (14 frq.)

�Normal TCH layer: re-use =10, (20 frq.)

�Aggressive TCH layer:re-use = 6, (6 frq.)

� ==> Network capacity = (1 +2 +1)* 300 = 1200 TRX


The inner circle covers a smaller area, and the

frequency can be reused more tightly.

Underlaid/Overlaid Frequency Allocation

Overlaid-cellUnderlaid-cell


Super fn

Regular fm Regular fm

Regular fm

Super fn

BCCH 15f Regular 12f Super 6f

BCCH Reuse density: 15

R TCH TRX reuse density: 24

S TCH TRX reuse density: 12

Overlaid/Underlaid Frequency Configuration

Super fn


BCCH14+TCH36：：：：

1BCCH+3TCH

1BCCH+3TCH 1BCCH+3TCH

1BCCH+12’TCH

1BCCH+12’TCH 1BCCH+12’TCH

1*3 1*1

1*3 and 1*1 Reuse Patterns


TRX1 TRX2 ... TRX7

TRX8 TRX9... TRX14 TRX15 TRX16...TRX21

TRX1 TRX2 ... TRX7

TRX8 TRX9... TRX14 TRX15 TRX16...TRX21

The red items are BCCH RCs

Illustration of 1*3 TCH Frequency Allocation


Frequency Planning Principle

� There should be no co-channel frequency carriers in one BTS.

� The frequency separation between BCCH and TCH in the same cell should

be not less than 400K.

� When frequency hopping is not used, the separation of TCH in the same

cell should be not less than 400K.

� In non-1*3 reuse mode, co-channel should be avoided between the

immediately neighbor BTS.

� Neighbor BTS should not have co-channels facing each other directly.

� Normally, with 1*3 reuse, the number of the hopping frequencies should be

not less than twice of the number of frequency hopping TRX in the same

cell.

� Pay close attention to co-channel reuse, avoiding the situation that the

same BCCH has the same BSIC in adjacent area.


Example of 1*3 Frequency Reuse

� Suppose 900 band: 96～124

� BTS configuration: S3/3/3

� BCCH layer: 96～109 reuse pattern: 4*3

� TCH layer: 110～124 reuse pattern: 1*3


Group 1 (MA1): 110 111 112 113 114 Cell1

Group 2 (MA2): 115 116 117 118 119 Cell2

Group 3 (MA3): 120 121 122 123 124 Cell3

TCH Consecutive Allocation Scheme


TCH Interval Allocation Scheme

Group 1 (MA1): 110 113 116 119 122 Cell1

Group 2 (MA2): 111 114 117 120 123 Cell2

Group 3 (MA3): 112 115 118 121 124 Cell3


Comparison Between Multi-layer reuse and 1*3

� For Multi-layer reuse pattern, either Base band hopping or RF hopping can

be used. But for 1x3 reuse, only RF hopping can be used.

� Multi-layer reuse pattern is a gradual process for TCH frequency planning.

In other words, the reuse is rather loose in TCH1 layer and it is quite close

in the last TCH layer (such as TCH5). The reason for this pattern is that

base band hopping is used in the Multi-layer reuse pattern. When there are

rather few frequency carriers, the hopping gain is small. Therefore, more

frequency carriers should be allocated for the layer with small TCH and

then the reuse coefficient is relatively large. When RF hopping is used in

the Multi-layer reuse pattern and there are a large number of frequency

carriers, the hopping gain is high and the reuse coefficient can be very

small. In addition, the Multi-layer reuse pattern is of a free pattern. It is

different from base band hopping, in which the reuse must be loose in the

first TCH layer and more close in inner layers.


Comparison Between Example of Frequency Planning and 1*3

� The frequency planning for the 1x3 mode is simple and it is easy to plan

the frequency for new added BTS.

� 1x3 mode requires a rather regular BTS location distribution.

� For the cells with fixed number of TRX, when the traffic is heavy, the 1x3

provides higher service quality than that of Multi-layer reuse pattern.

� TRX can be easily added to the 1x3 network, but TRX number of hopping

should not exceed the product of the allocated hopping frequency

number and the max RF load ratio.

� BCCH of Multi-layer reuse pattern can take part in the frequency hopping,

while BCCH in 1x3 mode can not.






Content of Frequency Hopping

� Class of hopping

� Advantages of hopping

� Parameter of hopping

� Collocation of hopping data


Frequency Hopping


Class of Hopping

� Hopping can be implemented in two ways

�Base-band hopping

�RF hopping

� Class according to the min hopping time unit

�Timeslot hopping

�Frame hopping


Base Band Hopping Principle


RF Hopping Principle


Class of Hopping

� Frame hopping

�Frequency changes every TDMA frame. The different

channel of one TRX uses the same MAIO.

� Timeslot hopping

�Frequency changes every timeslot. The different channel of

one TRX uses the different MAIO.


Advantages of Hopping

� Get an agreeable radio environment.

� Provide a similar communication quality for every user.

� Tighter reuse patterns are possible to be used for larger

capacity.


Smoothen the rapid fading (Rayleigh fading)

Frequency Diversity of Hopping


Smoothen and average the interference

Interference Diversity of Hopping


Hopping Parameters

� All the parameters which are related to hopping are configured

in cell/configure Hopping data

� Hopping mode: the mode used by the BTS system, including

three options: not hopping, base band hopping and RF hopping.

� MA (Mobile Allocation Set): the set of available RF bands when

hopping, containing at most 64 frequency carriers. The

frequency being used must be those of the available frequency


Description of Hopping Parameters

� HSN：hopping sequence number（0～63）.

� HSN=0：cycle hopping.

� HSN≠0：random hopping. Every sequence number

corresponds a pseudo random sequence.


Hopping Parameters

� MAIO (Mobile Allocation Index Offset): used to define the initial frequency

of the hopping.

� Be careful to configure the MAIO of same timeslot in all channels,

otherwise interference occurs.


Description Hopping Parameters

� At the air interface, the frequency used on a specific burst is an

element in MA set. MAI is used for indication, referring to a

specific element in the MA set.

� MAI is the function of TDMA FN, HSN and MAIO.

www.huawei.com

Thank You

Documents

78899587 Frequency Planning