OMF007001 Frequency Planning ISSUE1.5

8/3/2019 OMF007001 Frequency Planning ISSUE1.5

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OMF 007001

Frequency Planning

ISSUE1.5



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

Chapter 1

Chapter 1 Frequency planningFrequency planning

Chapter 2Chapter 2 Tight frequency reuseTight frequency reuse

Chapter 3Chapter 3 Frequency hoppingFrequency 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 =





Interference Ratio


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 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




A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3 B2

B3

C2

C3

D2D3 A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1D1

A2

A3B2

B3

C2

C3

D2

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




Chapter 1

Chapter 1 Frequency planningFrequency planning






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 n2n3 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 4694, the Multi-layer reuse pattern should be:

RC type

Allocated

frequencies

Number of

availablefrequencies

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 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




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




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 Reuse density: 15

R TCH TRX reuse density: 12

S TCH TRX reuse density: 6

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 samecell.

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:






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 thatbase 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 verysmall. 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 Multi-layer reuse 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.




Chapter 1Chapter 1 Frequency planningFrequency planning






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

HSNhopping sequence number 063

HSN=0cycle hopping.

HSN0random 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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OMF007001 Frequency Planning ISSUE1.5