Gsm Planning Engg

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October 4, 2001 RAJIV / GSM- Plg 1

GSM Planning & Engg.ALT CENTRE

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Rajiv KumarDGM (TX-II)

ALTTC Ghaziabad


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GSMNETWORK PLANNING PROCESS - I

Service Area

Estimation of traffic demand Available frequency resources.

Evolving an optimum coverage schemeof placing the cells over the entireservice area so as to provide completemobility to the subscribers.

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GSMNETWORK PLANNING PROCESS- II

Traffic demand estimation

-Population distribution-Car usage distribution

-Income level distribution-Land usage distribution

-Telephone usage distribution.

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GSMNETWORK PLANNING PROCESS-III

Estimation of Cell Radius

Service Area

Terrain conditionsDensity of foliage

Man made structures

Signal level at an unit distance from basestation

Signal strength decay per decade of distance. MOBILE RADIO NETWORK PLANNING

SOFTWARE TOOLS : TORNADO from SIEMENS

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GSMNETWORK PLANNING PROCESS-IV

MOBILE RADIO NETWORK PLANNINGSOFTWARE TOOLS

Propagation Predictions based upon various

propagation models e.g OKUMARA- HATA,WALFISCH-IKEGAMI or special external modelswritten by the users

Interference analysis

Automatic frequency planning

Coverage analysis by contour plots

Comparison with actual radio field measurements

Efficient tool to load,analyze and display systemperformance evaluation

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GSM PLANNING:THE BASIC PROCESS

1. CAPACITY PLANNING

2. COVERAGE PLANNING

4. EQUIPMENT PLANNING

3. PARAMETER PLANNING

5. OPTIMIZATION.

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E l B i Pl i (1/3)


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Example : Basic Planning(1/3) Say the customer wants to launch his network

with 20 sites or for 10,000 subscribers in a city

. The following assumptions are made in the planning process :

25 mE average traffic per subscriber

Grade of Service 2% Mobile to Mobile traffic 10%

Mobile to PSTN traffic 70%

Land to Mobile traffic 20% Average to cell duration 90 seconds

Traffic capacity of 1 carrier with 7 TCHs = 2.94E(approximately 120 subscribers ); a 1/1/1 site will have

capacity of approximately 350 subscribers.Traffic capacity of 2 carrier with 15 TCHs = 8.2E(approximetly330 subscribers). A 2/2/2 site will have acapacity of about 990 subscribers.

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Example - Basic Planning (2/3)Case 1: For specified number of sites (20)

1/1/1 sites (350 subs per site) 7000 subscribers.

2/2/2 sites (990 subs per site) 19800 subscribers.

Case 2: For specified capacity requirement (10000)

1/1/1 sites.10000/350 . 30 sites.

2/2/2 sites.10000/990 . 11sites.

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For 10000 capacity, at 25mE traffic, the total traffic

is 250E. We assume a hypothetical distribution oftraffic as shown below:

We may choose 2/2/2 sites for first 3area types and 1/1/1 sites for the rest.

This makes a total of 18 sites. After customers approval,site selection is done.

Example - Basic Planning (3/3)

Area Type % tfc tfc 1/1/1 2/2/2

Urban high density 20 50E 6 2Urban 30 75E 10 3

Industrial 15 37.5E 5 2

Suburban 25 62.5E 7 3Highways 5 12.5E 2 1

Quasi open 5 12.5E 2 1

Total 100 250E 32 12

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RF LINK BUDGET UL DLTRANSMITTING END MS BTS

Tx RF Output 33 dBm 43 dBmBody Loss -2.0dB 0dBCombiner Loss 0dB 0dBFeeder Loss (@2dB/100m) 0dB 1.5dBConnector Losses 0dB 2dB

Tx Antenna Gain 0dB 17.5dBEIRP 31dBm (A) 57dBm ( C)

RECEIVING END BTS MS

Rx sensitivity -107 dBm -102 dBm

Rx. Antenna gain 17.5dB 0dBDiversity Gain 3dB 0dBConnector Loss 2dB 0dBFeeder Loss 1.5dB 0dBInterference Degradation Margin 3dB 3dB

Body Loss 0dB 3dBDuplexer Loss 0dB 0dBRx Power -121dBm -96dBmFade Margin 4dB 4dBRequired Isotropic Rx .Power -117dBm (B) -92dBm ( D)

Maximum Permissible Path 148dB 149dB

RF LINK BUDGET

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B

T

S

Multipath Environment


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Calculate the path loss in a BTS site in an Urban environment,given the following parameters

Frequency : 900 MHz

Cell radius : 5Kms

BTS antenna height 30 m

Mobile antenna height 3m.

Also calculate the Attenuation slope for this site.

Lp =[69.55+26.16 log(f)- 13.82 log (hBTS) -a (hm)]+ [44.9 -6.55 log (hBTS)] log(d)

a(hm) = { 1.1 log (f) -0.7 }hm-{1.56 log (f) -0.8}

26.16 log (f) = 77.28dB13.82 log (hSTS) = 20.41dB

[44.9-6.55log (hSTS)]log (d) = 24.62 dB

a(hm) = 3.81 dB Path LossLp =69.55+77.28 -20.41 +24.62 -3.81= 147.23dB.

Attenuation Slope= [44.9-6.55 log (hSTS )]/10=35.225/10 =3.5225.

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Example- To Calculate cell radius (d)

Calculate the cell radius for a site that has:

Frequency : 900 MHz BTS height: 30meters

Mobile height: 3 meters BTS ERP: 55dBm

Expected RSS at the cell boundary (d=R) = -75dBm.

Lo= 122.61 dB; = 3.5 (calculated in the previous example).

122.61 -75+35 log (d) =55dBm.

log (d) = 7.39/35 =0.2111

Therefore d= antilog (0.2111) =1.62 Kms.

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Si l V i ti


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Signal Variations

FastFading

Slow Fades

Long term

average

Distance

RSS

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GSM


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GSM

IMPCS-COVERAGE

CAPITAL CITIES

BUILDING --- 40 %

In Car --- 70 %

Out door --- 90 %

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OTHER CITIES

BUILDING --- 20 %

In Car --- 40 %Out door --- 90 %

Cell Planningand C/I issues


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Cell Planning and C/I issues

Assume all cell are of the same size

All cells transmit the same power.

The path loss is not free space and is governed by the

attenuation constant .The reuse distance D and cell radius R are related to

the C/I as given below:

(D/R) = 6 (C/I)

The C/I is in absolute value.

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Freq Reuse & C/I Requirement

N D/R= 3N C/I= 10log(1/6(D/R)3.5

3 3.00 8.917 dB

4 3.46 13.29 dB

7 4.58 21.80 dB

9 5.19 25.62 dB

12 6.00 29.99 dB9

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CO-CHL INTERFERENCE


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D

R

A Multi Cell Environment


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Frequency Planning AspectsA1 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 2425 26 27 28 29 30 31 32 33 34 35 36

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A1

A2

A3 B1

B2B3

D1

D2D3 C1

C2

C3

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Antenna Diversity

B

T

S

B

T

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Horizontal Separation

B

T

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Vertical Separation

B

T

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Composite Separation

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General Cell Planning AspectsALT CENTRE

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General Considerations - TRX Requirement

Traffic Requirements ( Erlangs)

Grade of service required

Typical Call Model

Number of carriers from Traffic requirements

Control Channel Determination Equipment Configuration

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Excerpts fromErlangB Table

No.ofTrunks

Grade of Service

0.01% 0.10 0.50% 1.00% 2.00% 4.00% 5.00%1. 0.0001 0.001 0.005 0.0101 0.0204 0.0417 0.05262. 0.0142 0.0458 0.1054 0.1526 0.2235 0.3333 0.3813

3. 0.0868 0.1938 0.349 0.4555 0.6022 0.812 0.89944. 0.2347 0.4393 0.7012 0.8694 1.0923 1.3994 1.5246

5. 0.452 0.7621 1.132 1.3608 1.6571 2.0573 2.21856. 0.7282 1.1459 1.6218 1.909 2.2759 2.7649 2.96037. 1.0541 1.5786 2.1575 2.5009 2.9354 3.5095 3.7378

8. 1.4219 2.0513 2.7299 3.1276 3.6271 4.283 4.5439. 1.8256 2.5575 3.3326 3.7825 4.3447 5.0796 5.3702

10. 2.2601 3.092 3.9607 4.4612 5.084 5.8954 6.215711. 2.7216 3.8511 4.6104 5.1599 5.8415 6.7272 7.076412. 3.2069 4.2314 5.2789 5.876 6.6147 7.5827 7.9501

13. 3.7133 4.8305 5.9638 6.6072 7.4015 8.43 8.934914. 4.2387 5.4464 6.6632 7.3517 8.2003 9.2977 9.729515. 4.7811 6.0772 7.4755 8.108 9.0096 10.175 10.6327

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Capacity Planning- Required TCH Channels -I

RF Carriers Needed depend upon:

Number of Subscribers to be served

Average traffic per subscriber

Grade of service

150 Sub

150 Subscribers

GoS = 2%

25mE Traffic per

150 25 mE = 3.75 E

At2% GoS

8 TCH Required

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Capacity Planning- TCH Channels Required -II




Grade of service

200 Sub

200 Subscribers

GoS = 2%

25mE Traffic per

200 25 mE = 5.0 E

At2% GoS

10 TCH Required

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Capacity Planning- TCH Channels Required -II I




Grade of service

300 Sub

300 Subscribers

GoS = 2%

25mE Traffic per

300 25 mE = 7.5

At2% GoS

13 TCH Required

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An Example (1/7 )

Given that:

40000 subs in a Location area

Average traffic per subs = 25 mE

Calculate P Traffic in this cell = 30 E

SMS ratio = 0.1

Other parameters assumed as given in the Table

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An Example (2/ 7 )Step 1 : Calculate P ( Pages per second) :

40000 subs in a Location area

Average traffic per subs = 25 mE Hence total traffic E=40,000 25 mE= 1000 E

Average number of mobile terminated calls = 20 % = 6,000

Average Call Duration = 120 sec.

Hence the call rate (Calls/hour) = E (120/3600)

Calls/hour = 1000 (120/3600) = 30,000

Assume two pages per cell . Hence number of pages / Hr=12,000

Number of pages per second = 12000/3600 = 3.333

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AnExample(3/ 7 ) TT


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An Example (3 / 7 )

Step 2 : Calculate NPCH ( Number of Paging Channels) : NPCH

NPCH = 3.333/(2 4.25)= 0.392

For this we need values

call = e ( 120/3600) = 900 calls/hr in the cell

= P /(2 4.25)

Step 3 : Calculate NAGCH ( Number of AGCH Channels) :

SMS = call SMS = 900 0.1 = 90

LU = call L = 900 7 = 6300

AGCH = ( call + SMS + LU ) /3600 =(900 +90+6300)/3600 = 2.025 /second

N AGCH = 2.025/ (2 4.25) = 0.2382

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AnExample(4/ 7 )LTT


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An Example (4 / 7 )

Step 4 : Calculate NPAGCH ( Number of PAGCH Channels) :NPAGCH = ( NPCH + NAGCH ) / UCCCH

Where , UCCCH is the % utilization of control channels

Typically , UCCCH= 0 .33

NPAGCH = ( 0.2382 + 0.392) / .33 =1.909 blocks NAGCH

This means we need a minimum of 2 CCCH blocks

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AnExample(5/ 7 )AL

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An Example (5 / 7 )

Step 5 : Calculate SDCCH Requirement :

{{{{ call TC + LU (TLU+Tg ) + SMS (TSMS+ Tg) }}}} /3600

We need SDCCH channel duringCall set-up , Location updates& SMS

Hence Erlang offered for SDCCH Channel

We Know that

Tg=4 , TC =5 ,TLU = 4, TSMS= 6 seconds from the table

SDCCH Channel Erlang = ( 900 5 + 6300 9 + 90 10 )/3600= 17.25 E

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AnExample(6/ 7 )AL

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An Example (6 / 7 )

Step 6 : Calculate SDCCH Channels :From Erlang Tables with GoS =1 % & E = 17.25 we see that

SDCCH Channels = 27

Each Time slot accommodates =8 SDCCH Channels

Hence we need 3 independent Time slots & one Combined Time sloto accommodate 27 SDCCH Channels

Control channel Planning

TS 0 = Combined time slot (BCCH + 4 SDCCH) ..fBCCHTS 1 = SDCCH ( 8 SDCCH Channels) ..fBCCH

TS 1 & TS 2 ( 16 SDCCH Channels) .fx ,any other freq.

in the cell

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AnExample(7/ 7 )ALTTC


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An Example (7 / 7 )

Step 7 : Number of RF Carriers need Cell Traffic = 30 E

At

2% GoS

39 TCH Required

Time slots required for traffic channels = 39

Time slots required for control channels = 4

Total Time slots required 39 + 4 = 43

So RF Carriers needed = 43/8= 5.375 = 6 (say)

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THANK YOU

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