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Planning and Optimization Of GSM Cell
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By Sumantri Pramudiyanto (+6281703544310)Jakarta, April 7th , 2009
GSM Cell Planning and OptimizationStudy Case : Sragen Area
Materi berikut merupakan open content, bersifat free utk didistribusikan
ContentCell Planning ProcessIdle Mode OperationBSS ParameterRF Optimization flow chartStudy Cases of RF Optimization
Cell Planning Process
Cell planning can be described briefly as all the activities involved in determining which sites will be used for the radio equipment, which equipment will be used and how the equipment will be configured
Traffic and coverage AnalysisCollecting required dataMaking discussion with the client to know their
demand.Analyzing traffic and coverageRequired data :
• Geography data
• Demography data
• Data of around network
• Available frequency
• Number of customer which
wish to cover
Customer demand :
• GOS 2%
• 95 % Indoor coverage
• (C/I > 12 db) > 95%
Nominal Cell Plan - Dimensioning (1)Geography and Demography data taken from sragen.go.id
Table 1 Geographic + Demographic data Table 2 Demographic data per years
Wide of area which will be covered
Target subscriber• After the data available, we need to divided the region into
smaller cluster, then classify the subdistrict into cluster depend on traffic, contour area, and etc.
• From the demographic data (Table 2) , we able to calculate % growth of population.
573333 = 437556 x (1+r)6
r = 0.046
• Assume that, in 2010 the operator want to cover 10 % subscriber in the region, so the number of subscribers to be covered :
Pt = 10 % x 57333 x (1+0.046)3
Pt = 65629
• If traffic allocation per subscriber equal to 60mE then total traffic in Sragen area = 65629 x 60 mE = 3937.74 E
nrPoPt )1(
Nominal Cell Plan - Dimensioning (2) From the geographic data we can determine Erlang distribution
by density in each cluster.
The next step, we can calculate the number of required sites depend on traffic.
Using erlang B table we can count number of sites for cluster sragen tengah (GOS 2%, 1585.85 Erlang) 1586 TS ~ 227 TRX
Sragen tengah locate in center of town and has high traffic we use configuration 5/5/5 so the number of sites required in this cluster : 227/15 TRX = 15 Sites
With the same way we can calculate number of sites for the others cluster:Sragen Timur = 9 sites (Config 4/4/4)Sragen Barat = 12 sites (Config 4/4/4)Sragen Utara = 9 sites (Config 4/4/4)
Nominal Cell Plan – Link Budget Link Budget Calculation is required to achieve system balance
between uplink and downlink signal. Output from system balance is a cell size in every sites. We can calculate coverage area per sites in suburban and rural
cluster by equation L = k x R2
Lsite suburban = 1.95 x (1.865)2 = 6.78 km2
L site rural = 1.95 x (2.67)2 = 13.90 km2
The next step, calculating number of sites related to coverage.
Choose the biggest one
Link Budget
Nominal Cell Plan - Result
Sragen Utara
Sragen Timur
Sragen Tengah
Sragen Barat
CW Test / Model TuningIn order to find out
appropriate propagation model, RF Engineer should perform CW Test.
Drivetesting should be performed encircle the route and represent all of azimuth.
Input all of drivetesting result to the planning tools then conducting calibration to get appropriate propagation model.
SurveySurvey is required to ensure whether the nominal
cell position can be realized or not ?In general, The RF Team should give alternative
nominal or informed SAR ( ± 300m) to survey team, in case the nominal cannot be realized.
The survey team should take the panoramic photo around the nominal (0-360 degree), and report to the RF team if appear obstacle around the nominal.
Panoramic photo used to determine coverage target/azimuth
Survey team also need to survey : road to nominal, electricity, space for equipment.
Detail PlanningAll of nominal coordinates must be fixed in detail
planning phase.Scope of works in Detail Planning :
Frequency PlanningParameter Planning (BSIC, MAList, MAIO, HSN, etc)Adjacency planning
The main key in conducting frequency planning is avoiding co-channel and adjacent interference.
For TCH Frequency planning, we able to apply SFH or Baseband hopping in order to reduce the interference.
Detail Planning – Frequencies Allocation
SFH Pattern 1x1 will be applied in this implementation Number of Malist frequencies can be calculated by using
equation :
Maximum configuration for the sites 5/5/5, so that number of required frequencies :
Nfreqs/site = (12 – 3 ) x 2 + 3.2 = 24 Frequencies
FL =NTRX
# HoppersX 100%
3 sectors with 24 hopping frequencies :
-TCH = 3 TRXs FL = (3/24)*100% = 12,5%
-TCH = 4 TRXs FL = (4/24)*100% = 16,67%
Detail Planning – Frequencies Allocation
MAIO = 0 8 16
MAIO Step = 2
SFH Allocation untill configuration 5/5/5
Detail Planning – HSN Planning
Drivetest for QOD Program.ppt / 24.04.2008 / VS
HSN used to the parameter that differentiates the hopping algorithm between two cells having the same MAList.
We can choose best pairs HSN to reduce collision frequencies between server and adjacent.
Detail Planning – Coverage Result
Coverage Prediction Sragen Kota
Coverage Prediction Sragen Utara
Coverage Prediction Sragen Timur
Coverage Prediction Sragen Barat
NCC = 4,5
NCC = 2,3
NCC = 0,1
NCC = 5,6
Detail Planning – Interference Prediction
C/I Sragen KotaC/I Sragen Barat
C/I Sragen TimurC/I Sragen Utara
Installation and System TuningAfter Installation done, the installation team
need to conduct commisioning (VSWR Measurement, check hardware installation )
The Drive test team also need to verify whether the BTS serving target correctly or not
Then, Acceptance Test Procedure is conducted to check how well the KPI meets the demand.
Pre Launch Optimization performed to achieve the KPI Target for new site or TRX expansion.
IDLE MODE OPERATIONNormal Cell Selection
Search all the RF channels , take samples during 3-5 s and
calculate averages. And put them in ascending order with respect to
signal level. Then tune to the strongest RF channel.
Search for the frequency correction burst in that
carrier in order to varify if it is a BCCH carrier
Camp on the cell
Try to synchronize to the carrier and read
the BCCH data.
Is it a BCCH
carrier?
Is it a correct
PLMN ?
Is the cell barred?
Is C1>0
Tune to the next highest
RF channel which is not
tried before
No
No
NoNo
Yes
Yes
Yes
Yes
C1 = (A - Max(B,0))
A = Received Level Average -
p1
B = p2 - Maximum RF Output
Power of the Mobile Station
p1 = rxLevelAccessMin
Min. received level at the
MS required for access to
the system
p2 = msTxPowerMaxCCHMax.
Tx power level an MS may
use when accessing the
system
Cell ReselectionC1 + cellReselectOffset - temporaryOffset*H(penaltyTime-T) T < = penaltyTime
C2 =C1 + cellReselectOffset …………………………………………. T > penaltyTime
1 when T < = penaltyTime H(x) =
0 when T > penaltyTime
Cell Reselection Histerysis
BSS ParameterBTS Parameter RxLevAMI (0-63) Minimum signal strength for access the BTS in idle mode. CRESOFF (Cell Reselection Offset) (0-25) used for C2 Calculation, normally used in dual
band network (GSM<>DCS) RACHBT (RACH Busy Threshold) (0-127) defines a threshold for the signal level on the
RACH HRACTT1 (0-100) Half Rate Activation Threshold T3212 (0-255) Parameter LUP Periodically MAXRETR (1,2,4,7) Maximum Retransmission on RACH SDCCHCONGTH (0-100) SDCCH Congestion threshold RDLNKTO (0-15) Timer for Radiolink timeout
Power Control Parameter LOWTLEVD/U (0-63) the lower threshold of the received signal level on the
downlink/uplink for power increase UPTLEVU/D (0-63) defines the upper threshold of the received signal level on the
uplink/downlink for power reduction LOWTQUAD/U (0-7) the lower threshold of the received signal quality on the downlink
for power increase UPTQUAU/D (0-7) defines the upper threshold of the received signal quality on the
uplink for power reduction PWRINCSS (DB 2,4,6) defines the step size used when increasing the MS transmit
power PWREDSS (DB 2,4) defines the step size used when reducing the MS transmit power
BSS Parameter (2) Handover Parameter HOLTHLVDL/UL (0-63) defines the receive signal level threshold on the
downlink /uplink for inter-cell level handover decision. HOLTHQUDL/UL (0-7) defines the receive signal quality threshold on the
downlink/uplink for inter-cell quality handover decision
Adjacent Parameter RXLEVMIN the minimum received signal level the adjacent cell must
provide to be regarded as a suitable target cell for handover HOM Handover margin for better cell LEVHOM parameter defines the handover margin for handovers due to
uplink level or downlink level QUALLEVHOM this parameter defines the handover margin for handovers
due to uplink quality or downlink quality
RF Optimization Flow ChartStart
Identify KPI Formula
Identify the problems
SDSR Problems ?
Check TRX
Quality
Check Alarm
Check Interference
Check all others cause (Radio link
Failure, T200, Transcoder) from
statisticsHOSR
Problems ?
Check SDCCH Blocking
Check TCH
Blocking
Check Alarm
Check co-channel and
co-BSIC
Check Interference
Check Neighbor Relation
Check Handover Failure Per
Cause
Check Handover Parameter
DCR Problems
Check TRX
Quality
Check Alarm
Check co-channel and
co-BSIC
Check TA
Check Interference
problems
Check Malist, MAIO and
HSN
Check measurement from statistics
Take Action list
Y
Y
Conclusion Every New Network need good plan for
avoid problems that will be arise.Commonly there are six step in conducting
planning.The most critical problems in performing
cell planning process is interference.the New Sites onair need to be optimized to
achieve the KPIPre Launch Optimization is done for new
sites on air or expansion sites.