FrequencyPlanning_ed05_DR02

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All rights reserved 2005, Alcatel

Frequency Planning


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All rights reserved 2005, AlcatelFrequency Planning/ 26-07-2005

Overview

FP PrincipleFP Definition

Network evolution

Cell Planning - Frequency Planning

Interference TheoryCarrier types - Multiple Reuse Pattern MRP

Manual Frequency Planning

BSIC Planning

Frequency Planning Process RMS Frequency Planning


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Frequency Planning

Principle


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FP Definition

Frequency Planning is the process made o provide toeach TRX in the network a certain frequency

Frequency planning is done in order to provide thehighest spectrum efficiency (higher capacity with lessresources)

The frequency allocation is done in such way that allthe FP constraints are fulfilled: Co-cell/co-site/neighbour separation constraints

Overall interference is reduced


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GSM Frequency Spectrum

GSM 850 DL: 824-849 MHz, UL: 869-894 MHz

200 kHz channel spacing 124channels

ARFCN 128 -251

GSM 900

DL: 935-960 MHz, UL: 890-915 MHz 200 kHz channel spacing 124

channels

ARFCN 1 124

E-GSM

DL: 925-935 MHz, UL: 880-890 MHz

200 kHz channel spacing Additional 50 channels

ARFCN 0, 975 - 1023

GSM 1800 DL: 1805-1880 MHz, UL: 1710-1785

MHz


ARFCN 512 885

GSM 1900

DL: 1850-1910 MHz, UL: 1930-1990MHz


ARFCN 512 -810


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Impact of limited Frequency Spectrum

Bandwidth is an expensive resource

Best usage necessary

Efficient planning necessary to contain good QoS when the

traffic in the network is increasing

smaller reuse (high traffic with less resources)

MRP usage

implementation of concentric cells / microcells/dual band

implementation of Frequency Hopping Baseband Hopping (BBH)

Synthesized Hopping (SFH or RFH)

N k E l i C


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Network Evolution - CoverageApproach

First issue in a network life-cycle is to provide coverage

Network design changes rapidly

The frequency plan has to be adapted after each network extension

Planning method must be flexible and fast (group method)

During first steps manual frequency planning possible

N t k E l ti C it A h


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Network Evolution - Capacity Approach1/3

With the growing amount of subscribers, the need formore installed capacity is rising

Possible Solutions:

Installing more TRXs on the existing BTS

Implementing additional sites

More frequencies on air higher interference



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Installing more TRXs - AdvantagesNo site search/acquisition process

No additional sites to rent (saves cost)

Trunking efficiency Higher capacity per cell

Installing more TRXs - DisadvantagesMore antennas on roof top (Air combining)

Additional losses if WBC has to be used

Less (indoor) coverage

More frequencies per site needed

Tighter reuse necessary decreasing quality/ increase interference



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Implementing additional sites - AdvantagesReuse can remain the same (smaller cell sizes)

Needs less frequency spectrum

higher spectrum efficiency

Implementing additional sites - DisadvantagesSite search/acquisition process needed

Additional site cost (rent)

Re-design of old cells necessary (often not done)


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What is frequency reuse?

As the GSM spectrum is limited, frequencies have to bereused to provide enough capacity

The more often a frequency is reused within a certainamount of cells, the smaller the frequency reuse

Aim:Minimizing the frequency reuse for providing more capacity

REUSE CLUSTER:Area including cells which do not reuse the same frequency

(or frequency group)


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RCS and ARCS 1/2

Reuse Cluster Size - RCS If all cells within the reuse cluster have the same amount ofTRXs, the reuse per TRX layer can be calculated:

cellTRX

BRCS

/#=

cellTRX

BARCS

/#=

Average Reuse Cluster Size - ARCS If the cells are different equiped, the average number of TRXs

has to be used for calculating the average reuse cluster size:


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RCS and ARCS 2/2

The ARCS is giving the average reuse of the network when using the wholebandwidth and all TRXs per cell

E.g: if we want to have the reuse of all non hopping TCH TRXs, we have to use thededicated bandwidth and the average number of non hopping TCH TRXs per cellto get the ARCS of this layer type.

Each cell has only one BCCH. Therefore the BCCH reuse is an RCS and not anARCS!

The lower the ARCS is: the higher is capacity traffic (more TRX/cell)

The higher interference is

Traffic capacity/inference is always a trade-off


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Reuse Cluster Size 1/2

Sectorized sites

4 sites per reuse cluster

3 cells per site

REUSE Cluster Size:4X3 =12 1 2

3

4 5

6

7 8

9

10 11

12

1 2

3

4 5

6

7 8

9

10 11

12


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Reuse Cluster Size 2/2

Sectorized sites

3 sites per reuse cluster

3 cells per site

REUSE Cluster Size3X3 = 9

1 2

3

4 5

6

7 8

9

1 2

3

4 5

6

7 8

9


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Frequency Reuse: Example

No sectorization

7 cells per cluster

BCCH RCS = 7

TCH Reuse: Depending on BW

and Number of installed TRXsper cell

Example:

B= 26

4TRXs per cell

interfererregion

63

1726=

=

GuardBCCHRCSTCH

RCSTCH

RCSBCCH


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Cell Planning - Frequency Planning

Can frequency planning be seen independently from cell planning?

Bad cell planning

Island coverage disturbing the reuse pattern

Big overlap areas bigger reuse necessary

Good cell planning

Sharp cell borders good containment of frequency

Small overlap areas tighter reuse possible

Discussion

Influencing Factors on Frequency


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Influencing Factors on FrequencyReuse

Topography

Hilly terrain Usage of natural obstacles to define sharp cellborders tighter frequency reuse possible

Flat terrain Achievable reuse much more dependent on the

accurate cell design

Morphology

Water low attenuation high reuse distance

City high attenuation low reuse distance

Examples for different frequency


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Examples for different frequencyreuses

Big city in the south of Africa:BCCH reuse 26

Irregular cell design

Mixed morphology

Lots of water

Flat terrain plus some high sites

Big city in eastern EuropeBCCH reuse 12

Regular cell design Flat area

Only urban environment

I f Th 1/2


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Interference Theory 1/2

C/I restrictions9dB for co-channel interference

-9 dB for adjacent channel interference

dista nce DR

Received PowerP

rec

C/ I

Prec, A Prec, B

0

I t f Th 2/2


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Interference Theory 2/2

Probability density function [%]

0,0%

1,0%

2,0%

3,0%

4,0%

5,0%

C/I [dB] C/ImedC/Ithr

Margin

Interferer probability [%]

0%

20%

40%

60%

80%

100%

-20 -15 -10 -5 0 5 10 15 20

C/I - C/I thr[dB]

Interferer probabilityC/Imed is the calculated carrier to

interferer ratio at a certain location (pixel)

ARCS Pint[%]

6.5..9.0 107.0..9.5 7.58.5..11.0 5.012.0..16.0 2.5

C i T BCCH i


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Carrier Types - BCCH carrier

BCCH frequency is on air all the time with full power

BCCH BCCH interference is always present

If there is no traffic/signalling on TS 1 to 7 dummy bursts are transmitted

No interference reductions mechanisms are allowed, like:

PC (Power Control)

DTX (Discontinuous Transmission) are not allowed

BCCH needs a clean frequency plan since it is used for all mobiles within thenetwork

C i T TCH i


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Carrier Types - TCH carrier

PC allowed and recommended for UL and DLReduction of transmit power according to the actual path loss

Careful parameter tuning for DL necessary

DTX allowed and recommended for UL and DL

Discontinuous TransmissionIf there is no speech, nothing is transmitted

Generation of comfort noise at receiving mobile

TCH not in use no signal is transmitted

Special case: Concentric cellsDifferent re-uses for inner and outer zone are possible

Multiple reuse pattern 1/2


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For different types of carriers, different interferencepotential is expected

BCCH layer needs a higher REUSE then on other layers:

as the BCCH carrier has the highest interferer potential because of

being on air all the time the BCCH channel itself is accepting only low interference

TCH layers can be planned with a smaller REUSE

Inner zones of concentric cells are able to deal with the

smallest reuse in non hopping networks



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REUSE clusters for

INNER ZONE layer

TCH layer

BCCH layer

GSM restrictions


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GSM restrictions

Intra site minimum channel spacing 2

Intra cell minimum channel spacing 2 from Alcatel G2 BTS, (3 specified by GSMstandard)

fA

1

,fA

2

,fA3

,...

fB1,f

B2 ,fB3,...

fC1,fC2

,fC3,...

Frequencies fAx,fBx,fCx, must have atleast 2 channels spacing

Frequencies fx1,fx2,fx3, must have at

least 2 (or 3 depending on HW used)

channels spacing

Intermodulation problems 1/2


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IM Products GSM900 In a GSM 900 system intermodulation products of 3rd and 5th order

can cause interference

2 * f1,t f2,t = f2,r / 2 * f2,t f1,t = f1,r

3 * f1,t 2 * f2,t = f2,r / 3 * f2,t 2 * f1,t = f1,r

Frequency planning must avoid fulfilling these equations

Both frequencies must be on the same duplexer

To avoid intraband IM inside GSM900 the following frequencyseparations shall be avoided:

75/112/113 channels

IM5 IM3



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IM Products GSM1800 In a GSM 1800 system, only intermodulation products of 3rd order can

cause mesasurable interference

2 * f1,t f2,t = f2,r / 2 * f2,t f1,t = f1,r

Frequency separations to be avoided

237/238 channels

IM Products Dual Band (GSM900/GSM1800)

f1800,t f900,t = f900,r

Decoupling between the GSM 1800 TX path and the GSM 900 RX pathis less than 30 dB (e.g. same antenna used!)

Treating neighbour cells


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Treating neighbour cells

Cells, which are not declared as neighbour cells but are located in theneighbourhood may use adjacent frequencies if it is not avoidable, butno co channel frequencies

Cells which are declared as neighbours, thus have HO relationships,must not use co or adjacent frequencies

If an adjacent frequency is used, the HO will be risky and at least audible by the user.

Sometimes due to big frequency constraints separations of 1 channel for neighbourcells (with low amount of HO) is acceptable.

Where can I find neighbour cells?


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Where can I find neighbour cells?

At the OMC-R for each cell a list of neighbour cells is defined

Maximum number of neighbours: 32

The list of neighbours and their frequencies is transmitted to

the mobile to be able to perform measurements on thesefrequencies

In case of a HO cause, the HO will be performed towards thebest neighbour


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BSIC

BSIC allocation


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BSIC allocation

Together with the frequencies the Base Transeiver StationIdentity Code (BSIC) has to be planned

BSIC = NCC (3bits) + BCC (3bits)

The BSIC is to distinguish between Base Stations using the

same BCCH frequency

The aim of BSIC planning is not to use the samefrequency/BSIC combination on cells influencing each other

BSIC can be planned by the A9155 RNP tool

Spurious RACH


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Spurious RACH

Bad BSIC planning can cause SDCCH congestion causeby the spurious RACH problem, also known as GhostRACH

This problem occurs, when a mobile sends an HOaccess burst to a TRX of cell A using the same

frequency as a nearby cell B uses on the BCCH

Both cells using the same BSIC and Training SequenceCode TSQC, the HO access burst is understood by thecell B as a RACH for call setup

Therefore on cell B SDCCHs are allocated everytime aHO access burst is sent from the mobile to the cell A


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Frequency Planning Process

Network Life Cycle


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Network Life Cycle

Frequency planning occurs in all phase during network life-cycle

During planning phase (roll-out phase)

During optimization phase

Frequency Planning Process - Contents


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Frequency Planning Process Contents

Analysis of existing FP FP Inputs

FP Strategy Definition

Preparation Work

FP Creation Frequency Plan validation

Frequency Plan Implementation

Post Implementation Tasks

Reporting


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Analysis of existing FP

Analysis of existing FP 1/2


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This step is done during: Optimization phase Network densification steps

The reason is to define: Define if available RNP data can be used for the generation of a new

FP

Sites coordinates, cell impacted, height, azimuthsThe strategy used for FP (non-hopping, hopping)The possible outcome of a new FP KPI expected to be improved Define if a FP is needed

Spectrum definition Possible coverage problem FP brings no benefit in these areas Hardware used define co-cell the channel separation (2 or 3)



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Analysis of existing FP consists in: A9155 analysis Import csv files into A9155 (through A9155 PRC Generator) Coverage plots areas with bad coverage C/I Plots areas with high interference

Separation constraints violation

Analysis of the usage of the frequency band Define type of hopping OMC-R analysis Define areas with low KPI Analysis of the frequencies from that areas

Reporting Should be the base of the FP strategy chosen


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FP Inputs

FP Inputs


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p

FP Inputs must be provided by customer before starting the FP. target area of the new frequency plan has to be defined, as well asthe list of all involved cells from this area.

frequency spectrum. The FP targets must contain the availablefrequencies. If there are usage constraints related to the frequencyspectrum they must be provided.

Day Y, when the new frequency plan has to be ready forimplementation. The new plan must take into consideration thenetwork configuration planned for this day.

FP Quality Indicators used for frequency plan validation (beforeimplementation) Not the well know KPI New indicators: like C/I plots

The expected results from the FP should be clearly stated fromthe beginning, and the whole strategy should be driven bythese goals.


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FP Strategy Definition

FP Strategy 1/3


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gy

FP Strategy contains the different methods used duringfrequency allocation process

It consists of defining:Spectrum Partitioning

Macro layer / Micro layer

BCCH / TCH Guard Bands / Joker Frequencies

Decision on Frequency Hopping Implementation

for QoS improvement

due to capacity saturation

FP Strategy 2/3


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Frequency Coordination at the Planning/Country Border

Planning Border Take into consideration the frequencies ofthe first ring outside planning area

Country Border as defined in ETC recommendation

Frequency Coordination at Co-Existence of SeveralSystems. It must avoid

Spurious Emissions

Receiver Blocking

Intermodulation Products

BSIC Allocation Strategy

FP Strategy 3/3


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Frequency Planning Activation ModeMessage Mode (PRC activation)

Massive Logical Update (MLU)

Definition of Hot Spot Areas Set a higher priority during FP for areas with high traffic

Handling of Sites with Untypical Configurations


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FP Preparation Work

FP Preparation Work 1/2


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Retrieve data needed for FP: Logical data (csv files)Physical data: sites coordinates, heights, antenna types, tilt

A9155 AFP Dry Run Identify the possible problems that might occur and the time

needed OMC Neighbors Relationships Clean-upBad neighbour planning bad frequency plan

A problem in most running networks too many neighboursdeclared

Neighbour plan to be checked/optimized

FP Preparation Work 2/2


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Experience Database

Computed from field feedback during network operation It is based on: Old reports

Anomaly reports

RNP/RNO experience

Prepare Before/After Comparison In order to compute the KPI before FP implementation (for a later

comparison)

Can be: Drive tests

OMC-R Statistics


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FP Creation

FP Creation


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FP is created using a A9155 AFP Module BSIC planning has to be done as well

All parameters defined during the strategy phaseshould be reflected in the tool (see AFP training)


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Frequency PlanValidation

FP Validation


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Validation is done to take the decision about theimplementation of a new FP

There are several means of evaluating a FP (beforeimplementation)

Interference calculationConstraints violation

Visual analysis of frequencies plan

Frequency distribution.

KPI cannot be used in this phase


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Frequency PlanImplementation

Frequency Plan Implementation


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Implementation of the frequency plan is done viaOMC-R through the PRC

PRC can be created:Manually

For very small changesUsing External Tools

A9155 PRC Generator Module


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Post ImplementationTasks

Post Implementation Tasks


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To check the frequency plan after implementation, intensive QoSanalysis must be performedOMC-R

Drive tests

Compute KPI for before/after comparison

The optimization solutions for possible problems are:Using joker frequencies

Use MAFA to find clean frequencies

Manual optimization

All problems occurred must be reflected in an updated ExperienceDatabase (used for future FP)


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Reporting

Reporting


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Reporting step should containAt least one week network monitoring for before/after

comparison, to show

The QoS Improvement

Capacity increasement (if this was the main reason for FP)

All problems encountered during entire FP process

Possible improvements/suggestions in the overall Alcatel FPProcess


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New FP method: RMSbased FP

Radio Measurement Statistics


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RMS creates statistics on the network QoS:based on field measurements

Measurements are performed by each mobile during a call

RMS Different Outputs at TRX level

on neighbor cells (C/I)on downlink and uplink quality & level

on number of consecutive bad speech frames (BFI)

on Radio Link Counter (UpLink only)

on Path Balance and on Timing Advance

on Power and number of channel seizures9 Voice quality indicators

Used forRMS FP

RMS Frequency Planning Basics


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The Frequency Planning target is to improve networks QoSto reduce overall network interference

For all cells, RMS creates a C/I report for each neighbour

Measured interference is used by A9155 for frequency planning

RMS Measurement

Neighbour C/IGenerate RMS

files

A9155

Creates IM

New FPbased onRMS IM

RMS Measurements OMC-R A9155 A9155

RMS Frequency Planning


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RMS limitation for FP:Measurements are done only for declared neighbours in OMC-R. This

leads to:

Interferer BCCH frequencies, which are not neighbours, are not measured

RMS interference matrix is not reflecting the complete network interference:

Report only for declared neighbours

Interference is existing but is not measured

Solution:Generate artificially more neighbours during RMS measurements

(dummy neighbours)

Dummy neighbours can be:

Real cells (with very high HO_MARGIN)

Logical cell with the BCCH frequency to be measured (dummy cells)

Dummy Neighbours Principle


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RMS measurementswithout dummyneighboursCell close to serving cell

but not neighbours are:

not reported

not contributing to overallinterference matrix

Serving cell

Neighbour cell

Other cells

Some interferer BCCH

frequencies are notreported

Dummy Neighbours Principle


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RMS measurements

with dummyneighboursAll cells close to the

serving cell aremeasured andreported to the OMC-R

Target is to measureas many differentBCCH as possible

Dummy neighbours: Not real neighbours

Different BCCH than: Serving cell

Neighbour Cells

Serving cell

Neighbour cell

Dummyneighbour

cell

RMS Based AFPProcess Flow


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Conclusions

Discussion: Subdivide FrequencyBand?


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Any subdivision of the frequency band is reducing the

spectrum efficiency!

As the BCCH has to be very clean, it is neverthelessrecommended to use a separated band and select a biggerreuse

Microcells/Inner zones of concentric cells do not need a

separated band if they are dedicated for hotspot coverage

If there is a continuous layer of microcells/inner zones, it makesplanning easier when using a separated band

Any other separations should be avoided if possible!

Hint for creating a future proofed FP


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If a frequency plan is implemented, using all available

frequencies in the most efficient way, it is very difficult toimplement new sites in the future!

New sites would make a complete re-planning of the surroundingarea or the whole frequency plan necessary

To avoid re-planning every time when introducing new sites, it is

recommended to keep someJoker frequencies freeThese Joker frequencies can be used for new sites (especiallyBCCH TRXs) unless it is impossible to implement new siteswithout changing a big part of the frequency plan

New frequency plan necessary!

Summary of Abbreviations


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RCS - Reuse Cluster Size

ARCS - Average Reuse Cluster Size

MRP - Multiple Reuse Pattern

GSM - Global System for Mobile Communication

B - Bandwidth

Prec - Received Power

C/I - Carrier to Interferer ratio

WBC - Wide Band Combiner

BSIC - Base Transceiver Station Identity Code

ARFCN - Absolute Radio Frequency Channel

FrequencyPlanning_ed05_DR02

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