Planning Part_5 - Frequency Planning

7/31/2019 Planning Part_5 - Frequency Planning

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Soc Classification level

/1 Nokia Siemens Networks

FrequencyFrequencyPlanningPlanning


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Module objectives

DESCRIBE FREQUENCY PLANNING CRITERIA

CALCULATE THE FREQUENCY REUSE FACTOR

DESCRIBE FREQUENCY ALLOCATIONMETHODS

At the end of this module you will be able to


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Content of FrequencyPlanning GUIDELINES


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Frequency Planning GUIDELINES


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Tighter re-use of ownfrequencies

more capacity more interference

Target to minimise

interferences at an

acceptable capacitylevel

First when a completearea has beenfinalised

Automatic frequencyplanning tools

R

D

Frequency PlanBasics


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Why frequency re-use ?

8 MHz = 40 channels 7 traffic timeslots = 280 users

max. 280 simultaneous calls??!

Limited bandwidth available

Re-use frequencies as often as possible

Increased capacity

Increased interferences

Trade-off between interference level and capacity

Allocate frequency combination that creates least overall interference

conditions in the networkInterference is unavoidable

minimise total interferences in network

Frequency PlanBasics


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Criteria

The frequency planning criteria include the configuration

and frequency allocation aspects. The configurationaspects consider the:

Frequency band splitting between the macro and micro base

stations, Frequency band splitting between the BCCH and TCH layers, Frequency band grouping and

Different frequency reuse factors for different TRX layers.

Frequency allocation aspects include

frequency planning thresholds (QOS requirements) C/I requirements Percentage of co-channel and adjacent channel interference

Frequency PlanFrequency Planning Criteria


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Macro - Micro

needed because of inaccurate coverage predictions betweenmacro and micro layers not needed if accurate coverage predictions available in thefuture

BCCH - TCH

needed to ensure a good quality on BCCH frequency (in order toensure signalling)

Frequency PlanFrequency Band Splitting


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Frequency grouping

+ Frequency hopping (coherence bandwidth)+ Intermodulation+ Frequencies assigned to all TRX layers at one time+ Frequencies evenly used

- Limitations for automatic frequency planning algorithms- Fixed frequency reuse factor

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14

BCCH 1 2 3 4 5 6 7 8 9 10 11 12 13 14

2. TRX 15 16 17 18 19 20 21 22 23 24 25 26 27 283. TRX 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Frequency PlanFrequency Band Grouping


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f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14 f15

BCCH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

2. TRX 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

1. Micro 31 32 33 34 35 36 31 32 33 34 35 36 31 32 33

2. Micro 37 38 39 40 41 42 37 38 39 40 41 42 37 38 39

Frequency planning for different TRX layers

different freqency reuse factors for different TRX layers frequency planning for different layers

Frequency PlanDifferent Frequency Reuse Factors for Different TRX Layers


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C/I requirements

- C/Ic = 15 dB, C/Ia = -6 dB (Note Overlay-Underlay concepts)

Interference probability

- 2% co-channel and 5% adjacent channel interference

Frequency separations

- cell/site separations- combiner limitations

Frequency PlanFrequency Allocation Thresholds


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Do not use

Hexagon cell patterns

Regular grids

Systematic frequency allocation

Use

Interference matrix calculation

Calibrated propagation models

Minimise total interference innetwork

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D

f2

f3

f4f5

f6

f7

f3

f4f5

f6

f2

f3

f4

f5

f6f2

f3

f4f5

f6

f7

f2

f3

f4f5

f7

f2

f3

f4f5

f2

f3

f4f5

f6

f7

Frequency PlanBest Method


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Frequency PlanRe-Use-Factor

RuF

Average number of cells that have different frequencies

Measure for effectiveness of frequency plan

Trade-off: effectiveness vs. interferences

Multiple RuFs increase effectiveness of FP

Compromise between safe, interference free planning and effective resource

usage

1 3 6 9 12 15 18 21

safe planning(BCCH layer)

normal planning(TCH macro layer)

tight re-use planning(IUO layer)

same frequencyin every cell(spread spectrum)


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Frequency PlanMultiple Re-Use-Factor

Capacity increase with multiple RuFs

e.g. network with 300 cells

Bandwidth : 8 MHz (40 radio channels)

Single RuF =12

NW capacity = 40/12 * 300 = 1000 TRX

Multiple RuF

BCCH layer: re-use =14, (14 frq.) Normal TCH: re-use =10, (20 frq.)

Tight TCH layer: re-use = 6, (6 frq.)

NW cap. = (1 +2 +1)* 300 = 1200 TRX


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Co-cell separation

e.g. 3 (4 for GSM1800)

600 (800 ) kHz spacing between frequencies in the same cell

Co-site separation

e.g. 2

400 kHz spacing between frequencies on the same site

Co-channel interferences from neighbouring sitesAdjacent channel interferences from neighbouring sites

Frequency PlanConstraints


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Frequency PlanManual Allocation

A1 B1 C1 D1 E1 F1 G1 H1 A2 B2 C2 D2BCCH 1 26 3 28 5 30 7 32 9 34 11 36

TCH 25 2 27 4 29 6 31 8 33 10 35 12

E2 F2 G2 H2 A3 B3 C3 D3 E3 F3 G3 H3

BCCH 13 38 15 40 17 42 19 44 21 46 23 48

TCH 37 14 39 16 41 18 43 20 45 22 47 24

With Frequency Groups: 8 groups, 6 ARCFN each

A1 B1 C1 D1 E1 F1 G1 H1 I1 L1 A2 B2 C2 D2 E2 F2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

G2 H2 I2 L2 A3 B3 C3 D3 E3 F3 G3 H3 I3 L3 M3 N3

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

O3 P3 Q3 R3 M4 N4 O4 P4 Q4 R4 M5 N5 O5 P5 Q1 R5

33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

BCCH

BCCH TCH

TCH

With Separated Bands: 10 groups BCCH, 6 TCH, 3 ARCFNeach


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Allocation Criteria

Take into account both: theoretical dominance area and

planner's knowledge of the site

Starting point:

critical site or critical area

"cluster approach"?

"dynamic" BCCH allocation

No more than 60-70 sites!!!

Conclusion

Method 1 is simpler than method 2

Method 2 is more accurate

(RuFBCCH > RuFTCH, intracell HO)

C/I C/A C/I C/A

groups x x x x

sub-bands x

TCHBCCHsimplicity

Frequency PlanManual Allocation


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Frequency allocation algorithms implemented inplanning tools

Compute compatibility matrix across total cell area

(heavy computing!) Allocate same frequencies in sufficiently separatedcells

Allocate frequencies until traffic needs of all cells aresatisfied

Boundary condition: minimise total networkinterferences

No closed solution available for this problem

Iterative procedure

Frequency PlanAutomatic Allocation


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Interferenceparameters setting

Separationparameters setting

Interference matrix calculation

Separation matrix calculation

Frequency allocation Analyzeresults


Choose the following parameters for all network layers

Co-cell separation

Co-site separation

Target level for co-channel + adj channel interference

Frequency band allowed

Algohorithm:


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Interference matrix

Element (i,j) = amount of interference caused on cell i by cell j

Comparison parameter = co-channel (adj channel) C/I

Separation matrix

Element (i,j) = minimum channel separation between cell i and cell j

Comparison parameter = maximum C/I (C/A) probability

Co-site, co-cell and adj-cell separations manually set


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Evaluation criteria

Check the avg co-channelinterferenceparameter

Check the channel distribution Check the contraints violationlist

Use the Interference Analisystool

Automatic frequency

plan

Manual analysis and errorcorrection

Finalresult


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A

BC

15km

internationalborderline

Frequency PlanFrequency Coordination

Regulations for international boundaries

18 dB V/m at borderline

18 dB V/m at 15km distance from border for preferential frequencies

Set of preferential and reserved frequencies must be mutuallyagreed between operators


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Intermodulation interference can be avoided by

Ensuring that the base station site equipment quality is such high that the

intermodulation does not exist, Grouping the frequencies such that the intermodulation products do not cause

interference or Allocating the frequencies such that the intermodulation products do not cause

interference or

its complex influence on the frequency planning can be made easier by

Preventing the power control (only for the downlink intermodulation products) or

Directing the intermodulation products to the BCCH frequencies (there is nodownlink power control on the BCCH).

Frequency PlanIntermodulation


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Exercises / Questions Is the frequency grouping of the reuse factor 15 enough to

maximise the performance of the frequency hopping?

Does the 1800 MHz GSM network cause interference to the 900MHz networks?

Why does the frequency band have to be split?


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References

1. J. Lempiinen, M. Manninen, Radio Interface System Planningfor GSM/GPRS/UMTS, Kluwer Academic Publishers 2001.

Planning Part_5 - Frequency Planning

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