Frequency Planning and Neighbor Cell Planning

8/10/2019 Frequency Planning and Neighbor Cell Planning

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Frequency Planning and

Neighbor Cell Planning

ISSUE1.0


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Chapter 1 Frequency planning

Chapter 2 Tight frequency reuse

Chapter 3 Frequency hopping

Chapter 4 Neighbor Cell Planning


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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


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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


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Frequency Band Configuration

GSM900:

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

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


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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

Requirement for Interference and

Carrier-to-Interference Ratio

C/I =


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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 =


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Effect of Interference

Decrease of signal quality

Bit error Recoverable: channel coding, error correction

Irrecoverable: phase distortion System interference model

Unbalanced: uplink interference downlinkinterference

Asymmetrical: the interference is different at

the MS and BTS ends


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RXQUAL Mean BER BER rangeclass (%) 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


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{fi,fj..fk}

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

Macro-cell system

d

Micro-cell system

Concept of Frequency Reuse


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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.


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Looser reuse

Higher frequency reuseefficiency, 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*312

n*mn*m

n: BTS number in a basic reuse cluster

m: Frequency group number in a BTS


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Interference (C/I) Estimation

6

1

q

I

C

1/2

q = D/R = ( 3 k )


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R

D

This old-fashioned frequency distribution

mode is not recommended

Frequency Reuse Patterns

Purpose: to minimize the interference in thewhole network with the final frequencyallocation plan

Theoretically

Regular hexagon cell

Regular network distribution

Cell cluster

Multiplexing distance

D = R *sqrt(3*K)


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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 A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3

D2D3

A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

4*3 Frequency Reuse


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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


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Chapter 4 Neighbor Cell Planning


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Tight Frequency Reuse Technology

Multi-layer reuse pattern

Underlaid and overlaid cell

1*3

1*1


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Multi-layer Reuse Pattern


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BCCH: n1

TCH1: n2

TCH2: n3

TCHm-1: nm

n1 n2n3 n4 ...... nm

And n1+n2+...+nm

=n

Multi-layer Reuse Pattern


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Multi-layer Reuse Pattern Frequency

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

number is 4694, the Multi-layer reuse pattern should be:

RC type Allocatedfrequencies

Number ofavailablefrequencies

BCCH 46~57 12

TCH1 58~66 9

TCH2 67~74 8

TCH3 75~82 8

TCH4 83~88 6

TCH5 89~94 6


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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


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cap N BW

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


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cap N BW

re use

i

i

.

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


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The inner circle covers a smaller area, and the frequency

can be reused more tightly.

Underlaid/Overlaid Frequency

Allocation

Overlaid-cellUnderlaid-cell


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Super fn

Regular fm Regular fm

Regular fm

Super fn

BCCH 15f Regular 24f Super 12f

BCCH Reuse density: 15

R TCH TRX reuse density: 12

S TCH TRX reuse density: 6

Overlaid/Underlaid Frequency

Configuration

Super fn


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BCCH14+TCH36

1BCCH+3TCH

1BCCH+3TCH 1BCCH+3TCH

1BCCH+12TCH

1BCCH+12TCH 1BCCH+12TCH

4*3 1*3

4*3 and 1*3 Reuse Patterns


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TRX1 TRX2 ... TRX7

TRX8TRX9... TRX14 TRX15TRX16...TRX21

TRX1TRX2 ... TRX7

TRX8TRX9... TRX14 TRX15TRX16...TRX21

The red items are BCCH RCs

Illustration of 1*3 TCH Frequency

Allocation


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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 shouldbe not less than 400K.

When frequency hopping is not used, the separation of TCH in the samecell should be not less than 400K.

In non-1*3 reuse mode, co-channel should be avoided between theimmediately neighbor BTS.

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

Normally, with 1*3 reuse, the number of the hopping frequenciesshould be not less than twice of the number of frequency hopping TRXin the same cell.

Pay close attention to co-channel reuse, avoiding the situation that thesame BCCH has the same BSIC in adjacent area.


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.

Example of Frequency Planning

An example network in a specific place, BTSare densely located. The topography is plain.The maximum BTS configuration is S3/3/2

Initial planning:


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Example of Frequency Planning

Final frequency planning:


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Example of 1*3 Frequency Reuse

Suppose 900 band: 96124

BTS configuration: S3/3/3

BCCH layer: 96

109 reuse pattern: 4*3 TCH layer: 110124 reuse pattern: 1*3


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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


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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


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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 carriersshould 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.


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Chapter 4 Neighbor cell planning


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Content of Frequency Hopping

Class of hopping

Advantages of hopping

Parameter of hopping

Collocation of hopping data


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Content of Frequency Hopping

Class of hopping

Advantages of hopping

Parameter of hopping

Collocation of hopping data


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Frequency Hopping


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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


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Base Band Hopping Principle


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RF Hopping Principle


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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.


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Advantages of Hopping

Get an agreeable radio environment.

Provide a similar communication quality for

every user.

Tighter reuse patterns are possible to be usedfor larger capacity.


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Smoothen the rapid fading (Rayleigh fading)

Frequency Diversity of Hopping


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Smoothen and average the interference

Interference Diversity of Hopping


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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


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Description of Hopping Parameters

HSNhopping sequence number063.

HSN=0cycle hopping.

HSN0random hopping. Every sequence number

corresponds a pseudo random sequence.


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Hopping Parameters

MAIO (Mobile Allocation Index Offset): used to define the initialfrequency of the hopping.

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

otherwise interference occurs.


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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.


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Chapter 4 Neighbor cell planning


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Why

Handover is based on the neighbor relationship. Existing problem of neighbor planning No neighbor relationship, no handover

Co-BCCH and co-basic between adjacent cells leadto handover failure.

redundant neighbors

missing neighbor


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Neighbor Cell Description

There are table BA1 and table BA2.

Table BA1 describes BCCH frequencies of the adjacent cells to be measured when the MS is in

idle mode.

Table BA2 describes BCCH frequencies of the adjacent cells to be measured when the MS is in

dedicated mode.

There are two kinds of neighbors

bidirectional neighbors

unidirectional neighbors

Bidirectional neighbors are common, and unidirectional neighbors are used in special

condition, such as overshooting


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The cells of co-site must be set as neighbor cells The cells confronting directly must be added to neighbor list

The cells facing toward the same direction should be neighbors The cells shooting by the original cell

The cells shooting at the original cell

The cells, one site apart, face to face should be neighbor cells.

Neighbor Planning Principle


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Demonstration (ideally)

co-site cellConfronting cell

same directional cell

one site apart

face to face cell

Original cell


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Frequency Planning and Neighbor Cell Planning

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