microsoft power point - 6 omf007001 frequency planning issue1

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Frequency Planning


Contents

1. Frequency Planning

2. Tight Frequency Reuse

3. Frequency Hopping


Content of Frequency Planning

� Frequency resource of GSM system

� Concept of frequency reuse

� Requirement for interference and carrier-to-interference

ratio

� 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


{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.

� If every frequency is reused N times

� Max. 320*N uses can access the network at the same time.


Requirement for Interference and Carrier-to-Interference Ratio

All useful signals carrier

All useless signals interference=

GSM standard: C / I >= 9 dB

In practical projects: C / I >= 12dB

Useful signal Noise from environment

Other signals

C/I =


Looser reuse

Higher frequency reuse

efficiency, but interference

is serious. More technique

Is needed.

Tighter reuse

0 12 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


4*3 Frequency Reuse

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


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

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


Contents


2. Tight frequency Reuse



Tight Frequency Reuse Technology

� Multi-layer reuse pattern

� Underlaid and overlaid cell

� 1*3 or 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


� 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

Advantages of Multi-layer Reuse Pattern


� Capacity increases 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

Advantages of Multi-layer Reuse Pattern


The inner circle covers a smaller area, and the frequency can

be reused more tightly.

Underlaid/Overlaid Frequency Allocation

Overlaid-cell

Underlaid-cell


Overlaid/Underlaid Frequency Configuration

Super fn

Regular fm Regular fm Regular fm

Super fn

BCCH 15f Regular 24f Super 12f

BCCH TRX reuse density: 15

Regular TCH TRX reuse density: 12

Super TCH TRX reuse density: 6

Super fn


BCCH14+TCH36：：：：

1BCCH+3TCH

1BCCH+3TCH 1BCCH+3TCH

1BCCH+12’TCH

1BCCH+12’TCH 1BCCH+12’TCH

4*3

1*3

1*3 or 1*1Reuse Patterns

1BCCH+36’TCH

1BCCH+36’TCH 1BCCH+36’TCH

1*1


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 or 1*1 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 Frequency Planning� An example network in a specific place, BTS are densely

located. The topography is plain. The maximum BTS

configuration is S3/3/2

� Initial planning:


Example of Frequency Planning

� Final frequency planning:


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.

� 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.


Contents


2. Tight Frequency Reuse



Content of Frequency Hopping

� Class of hopping

� Advantages of hopping

� Parameter of hopping

� Collocation of hopping data


Frequency Hopping


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


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

FH bus


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.


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


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.

� 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.

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microsoft power point - 6 omf007001 frequency planning issue1

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