Njhx460d - Frequency Planning

Mason Communications Training: WCDMA Radio Planning CourseModule 4: Network Design

Section 4.6: Frequency Planning

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www.masoncom.com

© Mason Communications Ltd 2001

4 Network Design4.6 Frequency Planning

WCDMA Radio Planning Course



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Frequency Planning

4.6.2© Mason Communications Ltd 2001

Where are We Now?Introduction

UMTS Overview

Access Technologies

WCDMA Introduction

Model Architecture

UMTS Standards

Mobile RadioChannel

Narrowband Channel

Wideband Channel

Local Mean Signal

Path Loss

Diversity

DesignElements

Basic Radio Principles

Antennas and Feeders

Interference

Matched Filters and

Rake Receivers

WCDMA Physical Layer

NetworkDesign

Operator’s Design Guides

The Planning Process

Polygons

Site Placement

Antenna Placement

Forward Capacity Planning

Course Overview

Conventional Optimisation

3G Optimisation

Radio Resource Management

Optimisation

CourseWash Up

Frequency Planning

LinkBudgets

Where are We Now?

The Course Map shows which section we are now on.



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Frequency Planning


What is in This Section?

Co- and Adjacent Channel Interference

Frequency Reuse

GSM Frequency Planning Examples

Summary

NetworkDesign



Site Placement

Polygons

Antenna Placement


LinkBudgets

Frequency Planning



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Why is this Section Important to You?

• Frequency Planning is of central importance in GSM

• Both GSM and UMTS are interference-limited networks because of the fact that frequencies are reused

• In GSM, interference cannot be tolerated, and GSM requires “macro management” of the interference in the form of Frequency Planning

• In UMTS, a level of interference is tolerated, and UMTS employs a range of “micro management” schemes to manage the interference

• This section is included for completeness as a recap of principles in GSM, and as a reminder that the situation is very different in WCDMA

Why is this Section Important to You?



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How Will You Learn?

Discussion Worked Examples

How Will You Learn?



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Where are We Now?


Frequency Reuse


Summary

NetworkDesign



Site Placement

Polygons

Antenna Placement


LinkBudgets

Frequency Planning



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Frequency Planning

• Once cell locations planned where needed, then must plan the frequencies of each cell

• Limiting factor in a cellular system is the number of available frequencies

• To meet the traffic demand a cellular system re-uses these frequencies throughout the network

• Frequency reuse causes potential problems such as co-channel and adjacent channel interference



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Co-channel Interference

• Interference caused by the use of the same frequency in other cells

• In order to receive the wanted signal this interference must be much less than the wanted signal

• A measure of the amount of interference experienced is the Carrier to Interference ratio (C/I)

• The required C/I is achieved through the use of a suitable reusedistance

Reuse Distance



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Adjacent Channel Interference

• Interference due to transmission on an adjacent channel

• Usually adjacent channels are not allocated within the same cell

F0 F1 F2 F3



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Where are We Now?


Frequency Reuse


Summary

NetworkDesign



Site Placement

Polygons

Antenna Placement


LinkBudgets

Frequency Planning



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Frequency Reuse

Cell

Base Site

Frequency 1

Frequency 2

Frequency 4

Frequency 5

Frequency 3

Frequency 6

Frequency 7



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Frequency Reuse

Cell Cluster



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Frequency Reuse



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Frequency Reuse

f2f3f1

f6 f4f5

f7f2

f3f1

f6 f4f5

f7

f2f3f1

f6 f4f5

f7

• Example shows a 7 cell re-use or ‘cluster’ size

• Possible cluster sizes are given by the equation:

where i and j are non-negative integers

22 jijiN ++=



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Cluster Sizes

• Example cluster sizes are given in the table below

i012232

j110102

Cluster Size1347912

3 1 133 2 164 0 194 1 21



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Typical Re-use Patterns

Re-use Pattern of 3

1

3

1

32 2

13

1

22

3

32

14

32

14

32

14

32

4

32

14

21

4

21

4

4

2

31

7

5

64

2

31

7

5

6

4

2

31

7

5

6

4

2

31

7

5

6

Re-use Pattern of 4 Re-use Pattern of 7



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Sectored Re-use Patterns

• The equation N = i2 + ij + j 2 may also be applied to cell plans incorporating sectored cells

• A sectored reuse is described as AxB where – A is the site reuse factor– B is the number of sectors per site

• For example a 3/9 reuse pattern means that there are 3 sites and 9 frequency groups in each cluster

• In this case each cell consists of 3 sectors



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Typical Sectored Re-use Patterns

1/3 Re-use Pattern4/12 Re-use Pattern

107

2

11 96

48

9

5

3

2

9

84

11

7 512

13

4

69

10

1

6

8

3

3/9 Re-use Pattern

5

2

5

31

6

79

2

8

1 3

4

1

3

1

32 2

13

1

22

3

3

24

7

76

1



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Example: Given the above diagram and the geometry of a hexagon, derive an equation for D in terms of N and R

f2f3f1

f6 f4f5

f7f2

f3f1

f6 f4f5

f7

f2f3f1

f6 f4f5

f7

Frequency Re-use Distance

• The Frequency Re-use Distance is the distance between base stations using the same frequency group

D



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Frequency Re-use Distance

SolutionD2 = a2 + b2

2b = 5R 3

2a = 3R

4D2 = 9R2 + 25R2 x 3

4

D = R 3N

D2 = 21R2

Db

a



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Example Re-use Distances

D = R 3N

3R

4.6R

6R

7.55R

D

3

7

12

19

N



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Carrier to Interference Ratio (1)

Assuming interference only from first tier :

I D-n

C R-n

where n is the radio path loss exponent

Effective interfering tier

R

D

CI

C

Ikk

K==

==∑∑

1

(( ))CI

R

D

Nn

n

n

== ==−−

−−6

3

6



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Example:

If a carrier to interference ratio of 15 dB is required for satisfactory performance of a cellular system, what is the re-use factor and cluster size that should be used if the path loss exponent is a) n = 4, b) n = 3 ?Assume only the first tier causes interference and that there are 6 co-channel cells within the first tier. Assume all interferers are equidistant from the mobile.



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Solution

( )

a) n = 4Consider 7 cell reuse,

3N

dB7 cell reuse can be used

=

= =

=

4583

45836

73527

18 66

4

.

..

.

CI

( )

b) n = 3

Consider 12 cell reuse,

3N

dB

12 cell reuse must be used

=

= =

=

6

66

36 0

1556

3CI

.

.



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3dB gain over non-sectored case (15.56)

I 3= = 18.57dB C ( 3N)n

Interference from only 3 cells of first tier

Effective interfering tier

D

Carrier to Interference: Sectored Cells

R



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Frequency Reuse Distance

• A large reuse distance results in low co-channel interference and low capacity

• A shorter reuse distance will result in a higher capacity but higher levels of co-channel interference

• The lower the interference the better the speech quality

• Frequency planning therefore results in a compromise between quality and capacity

Reuse Distance



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Spectral Allocation and Number of Channels

• The number of channels available to a particular operator is dependent upon their spectral allocation and the bandwidth of each radio channel

• For example an allocation of 2x5 MHz would allow

– 25 GSM 200 kHz duplex carriers– 5 IS-95 (CDMA) 1.25 MHz duplex carriers– 166 AMPS 30 kHz duplex carriers



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Frequency Groups

• In order to facilitate frequency planning, frequencies are divided into frequency groups

• If total number of frequencies is N, and number of frequency groups is F then each group will contain N/F frequencies

• Cells are allocated frequency groups to facilitate frequency reuse



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Where are We Now?


Frequency Reuse


Summary

NetworkDesign



Site Placement

Polygons

Antenna Placement


LinkBudgets

Frequency Planning



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GSM Frequency Planning Example

• Assume an operator is allocated 2x7.2 MHz

• This allows 36 frequencies (200 kHz carriers)

• In GSM frequencies are given an Absolute Radio Frequency Channel Number (ARFCN)

• The ARFCN and UL/DL frequencies are related by

nFuplink )MHz2.0(MHz0.890 +=

MHz45+= downlinkuplink FF

1241 ARFCN, ≤≤= nn



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GSM Frequency Planning Example

• We assume that our operator is allocated GSM frequency channels 1 to 36

• And that a 4/12 (4 sites, 12 frequency groups per cluster) re-use pattern will be used

• This therefore provides 12 groups with 3 frequencies per group

• Groups are labeled (A1,B1,C1,D1,A2, …, D3)

• Where the letter relates to the site and the number relates to the sector

• This allows simple frequency allocation resulting in the following Frequency Allocation Table



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GSM Frequency Planning Example4/12 Frequency Allocation Table

Frequency Group 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

Frequency(ARFCNs)

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



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GSM Frequency Planning Example4/12 Cell Plan

A1 A1A1 A1

A1 A1 A1



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A1 A1A1

B1

B1

B1

B1

B1

A1

B1

A1

B1

B1

A1 A1



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C1

A1 A1A1

B1

C1

B1

B1

C1

B1

C1

B1

C1

A1

C1

B1

C1

A1

B1

C1

B1

C1

B1

A1 A1



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C1

D1

A1

D1

A1

D1

A1

B1

C1

B1

B1

C1

B1

C1

B1

C1

D1

A1

C1

B1

C1

A1

D1

B1

C1

B1

C1

B1

A1

D1

A1

D1



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C1

D1

A1

D1

A1

D1

A1

B1

C1

A2

B1

B1

C1

A2

B1

C1

A2

B1

C1

D1

A1

C1

A2

B1

C1

A1

D1

A2

B1

C1

B1

C1

A2

B1

A1

D1

A1

D1



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C1

D1

B2

A1

D1

B2

A1

D1

B2

A1

B1

C1

A2

B1

B1

C1

A2

B1

C1

A2

B1

C1

D1

B2

A1

C1

A2

B1

C1

B2

A1

D1

A2

B1

C1

B2

B1

C1

A2

B1

B2

A1

D1

B2

A1

D1

B2 B2




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C1

C2

D1

B2

A1

C2

C2

D1

B2

A1

C2

D1

B2

A1

B1

C1

A2

B1

B1

C1

A2

B1

C1

A2

B1

C1

C2

D1

B2

A1

C2

C1

A2

B1

C1

B2

A1

C2

D1

A2

B1

C1

B2

B1

C1

A2

B1

B2

A1

C2

D1

B2

A1

C2

D1

C2 B2 B2 C2




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C1

C2

D1

B2

A1

C2

C2

D1

B2

A1

C2

D1

B2

A1

B1

D2

C1

A2

B1

B1

D2

C1

A2

B1

C1

A2

B1

D2

C1

C2

D1

B2

A1

C2

C1

A2

B1

D2

C1

B2

A1

C2

D1

A2

B1

D2

C1

B2

B1

D2

C1

A2

B1

B2

A1

C2

D1

B2

A1

C2

D1

C2 B2 B2 C2




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C1

C2

D1

B2

A1

C2

C2

D1

B2

A1

C2

D1

B2

A1

B1

D2

C1

A3

A2

B1

B1

D3

D2

C1

A3

A2

B1

C1

A3

A2

B1

D2

C1

C2

D1

B2

A1

C2

C1

A3

A2

B1

D2

C1

B2

A1

C2

D1

A3

A2

B1

D2

C1

B2

B1

D2

C1

A3

A2

B1

B2

A1

C2

D1

B2

A1

C2

D1

C2 B2 B2 C2




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C1

C2

D1

B3

B2

A1

C2

C2

D1

B3

B2

A1

C2

D1

B3

B2

A1

B1

D2

C1

A3

A2

B1

B1

D2

C1

A3

A2

B1

C1

A3

A2

B1

D2

C1

C2

D1

B3

B2

A1

C2

C1

A3

A2

B1

D2

C1

B3

B2

A1

C2

D1

B3

A3

A2

B1

D2

C1

B2

B1

D2

C1

A3

A2

B1

B3

B2

A1

C2

D1

B3

B3

B2

A1

C2

D1

B3

C2 B2 B2 C2




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C3

C1

C2

D1

B3

B2

A1

C3

C2

C3

C2

D1

B3

B2

A1

C3

C3

C2

D1

B3

B2

A1

C3

B1

D2

C1

A3

A2

B1

B1

D2

C1

A3

A2

B1

C1

A3

A2

B1

D2

C1

C2

D1

B3

B2

A1

C3

C2

C1

A3

A2

B1

D2

C1

B3

B2

A1

C3

C2

D1

B3

A3

A2

B1

D2

C1

B2

B1

D2

C1

A3

A2

B1

B3

B2

A1

C3

C2

D1

B3

B3

B2

A1

C3

C2

D1

B3

C2 B2 B2 C2

C3




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C3

C1

C2

D1

B3

B2

A1

C3

C2

C3

C2

D1

B3

B2

A1

C3

C3

C2

D1

B3

B2

A1

C3

B1

D3

D2

C1

A3

A2

B1

B1

D3

D2

C1

A3

A2

B1

C1

A3

A2

B1

D3

D2

C1

C2

D1

B3

B2

A1

C3

C2

C1

A3

A2

B1

D3

D2

C1

B3

B2

A1

C3

C2

D1

B3

A3

A2

B1

D3

D2

C1

B2

B1

D3

D2

C1

A3

A2

B1

B3

B2

A1

C3

C2

D1

B3

B3

B2

A1

C3

C2

D1

B3

C2 B2 B2 C2

C3




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• Given such a frequency plan and a cell radius of 3km would lead to a frequency re-use distance of

• With 3 frequencies per group

km1812*33 ==D




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GSM Frequency Planning Example - 3/9

• We again assume that our operator is allocated GSM frequency channels 1 to 36

• And that a 3/9 (3 sites, 9 frequency groups per cluster) re-use pattern will be used

• This therefore provides 9 groups with 4 frequencies per group

• Groups are labeled (A1,B1,C1,A2, …, C3)

• Where the letter relates to the site and the number relates to the sector

• This allows simple frequency allocation resulting in the following Frequency Allocation Table



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GSM Frequency Planning Example3/9 Frequency Allocation Table

Frequency Group 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 18Frequency(ARFCNs)

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36



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A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3



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A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

B1

B2

B3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3




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A1

A2

A3

B1

B2

B3

C1

C2

C3

A1

A2

A3

B1

B2

B3

C1

C2

C3

A1

A2

A3

B1

B2

B3

C1

C2

C3

A1

A2

A3

B1

B2

B3

C1

C2

C3

A1

A2

A3

B1

B2

B3

C1

C2

C3

A1

A2

A3

B1

B2

B3

C1

C2

C3

C1

C2

C3

B1

B2

B3

C1

C2

C3

C1

C2

C3

A1

A2

A3

B1

B2

B3

A1

A2

A3

B1

B2

B3

C1

C2

C3




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• Given such a frequency plan and a cell radius of 3km would lead to a frequency re-use distance of

• With 4 frequencies per group

• Leading to a higher capacity than the 4/12 system but an overall lower C/I and therefore lower quality.

km15.69*33 ==D




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GSM Frequency Planning ExampleBCCH Planning

• Given 3 frequencies per group, at least one of these frequencies will be used to carry the Broadcast Control Channel (BCCH) on timeslot 0 within each cell

• All other slots of BCCH frequency filled with dummy bursts if unused

A1

A2

A3



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• The BCCH is very important for call setup and HO

• Must be planned to avoid excessive interference

• To achieve a higher C/I BCCH can be assigned a different frequency to nearby cells using same group

A1

A2

A3A1

A2

A3

GSM Frequency Planning ExampleBCCH Planning



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Fractional Loading

• Much tighter frequency reuse plans such as 3/9 maybe employed through the use of Slow Frequency Hopping (SFH) and fractional loading

3/9 Re-use Pattern

5

2

5

31

6

79

2

8

1 3

4



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Fractional Loading

• Since SFH averages the interference experience by a particular BTS/MS within the system, if only a number of channels are occupied a much lower level of interference is experienced

A1

A2

A3 A1

A2

A3



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Partial Reuse

• A novel reuse scheme whereby users close to the base station use a tighter reuse than those further away



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Where are We Now?


Frequency Reuse


Summary

NetworkDesign



Site Placement

Polygons

Antenna Placement


LinkBudgets

Frequency Planning



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Summary

• This section on Frequency Planning is a review of Frequency Planning for GSM

• It is included for completeness as a recap of principles in GSM, and as a reminder that the situation is very different in WCDMA

Summary



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The End of Frequency PlanningIntroduction Network

DesignDesign

Elements

Basic Radio Principles

Mobile RadioChannel

Optimisation

Narrowband Channel

Wideband Channel

Local Mean Signal

Path Loss

Diversity

UMTS Overview

Access Technologies

Model Architecture

UMTS Standards

WCDMA Introduction



Polygons

Site Placement

Antenna Placement

Frequency Planning


Course Overview

Radio Resource Management

Antennas and Feeders

WCDMA Physical Layer

Interference

Matched Filters and

Rake Receivers Conventional Optimisation

CourseWash Up

3G Optimisation

LinkBudgets

Any MoreQuestions?



NJHX460D REV D

Presentation

Title

Date

Tel: +44 (0)161 877 7808

Fax: +44 (0)161 877 7810

Client

Mason C

omm

unications Ltd5 E

xchange Quay

Manchester M

5 3EF

England



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ill not be reproduced, copied,lent or disclosed, directly or indirectly, or used for any purpose other than that for w

hich it was

specifically furnished.

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Njhx460d - Frequency Planning

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