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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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ALTTCCO-CHL INTERFERENCE
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
S
Horizontal Separation
B
T
S
Vertical Separation
B
T
S
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
RF Carriers Needed depend upon:
Number of Subscribers to be served
Average traffic per subscriber
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
RF Carriers Needed depend upon:
Number of Subscribers to be served
Average traffic per subscriber
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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