KPI ANALYSISREASONS AND SOLUTIONS

Some Relations-1-One BSC=6 BCSU (Base Control signaling unit).One BCSU = Support 110 TRX. 1 TRX= 8 time slots.Total no. of TRX = 110 *6=660 TRX in single BSCOne BSC = One LACOne BSC= 660* 8 = time slots but if dual rate is implemented that it consider as two slots.One BSC= two Lac also but for city one LAC b/c it effects SD blocking and LAC updation on that channel.

Some Relations-2-One BSC= 1 to 248 BCF.

One BSC= 1 to 248 BTS

One BTS means = one sector of any configuration

One BCF means= one site of three or four sector

BCF= Base control function.

BTS= Base transceiver system.

NSEI= is hardware and software device which supports the GPRS in n/w

Some Relations-3-One NSEI= supports 64 BTS and 128 TRX if any one of them is full then we can assign second NSEI port in same BSC1TRX=117 subscriber1 subscriber=25 m erlangs (TCH)1 subscriber=.004 m erlangs(SD)1 TRX=2.94 erlang(2% GOS )2 TRX=8.2 erlang(2% GOS )3 TRX=14.6 erlang(2% GOS )4 TRX=21.2 erlang(2% GOS )If BSC 3VI, OSS is 4 and System is S11 then max capacity of BSC is 660 TRXs.If OSS 4.2 and system S12 is using then max capacity of BSC will be 2000TRXs

KPIs to be monitoredSD BlockingSD DropTCH BlockingTCH AssignmentTCH DropHOSR

KPI s to be monitored

ParameterShowcase ThresholdNon-Showcase ThresholdSD Blocking0.250.5SD Drop1.21.7TCH Blocking0.50.5TCH Assignment98.598TCH Drop1.53HOSR9592

Get ServiceGet SDCCHEstablish SD ChannelEst. TCHConn.Call PhoneRef. PhoneSD BlockingSDCCH SeizerTCH BlockingCSSR or TCH AssignmentCall EstablishmentCall completion Rate (TCH Drop call)

What is Dropped Call?All cell resources are available but calls are failing, then we have a call drop scenario. This could be caused by software errors, congestion, C7 link failures,HW problems or many other reasons.

If a call is abnormally disconnected, a Clear Request is sent to the MSC .If the Call is disconnected in a normal Fashion then Clear Message with cause code Call Control is sent. It is important to establish what types of calls are failing, and over what percentage of the network it is occurring.

SDCCH CHANNEL :

SDCCH is a dedicated channel which is using for LAC updation, Call setup, SMS in idle mode. It works in UL & DL.

SD Blocking:SD blocking means that you are not getting SD resource for the call origination. When MS connects with NW then RACH and AGCH are provided. After AGCH,SDCCH is provided but if SDCCH is not provided at this time due some problems or due to unavailable of SD by BSC ,its called as SD Blocking. There are no of reasons for that.If such a case arises the customer will not be able to originate any call.

Difference Between Blocking and Congestion:It is very important to know difference between blocking and congestion. Some people think that both are same, but they differ from each other. If all the SD resources are full and not available for SD assign then its come into congestion. If at a particular time call is attempted and it fails then it known as Blocking.

Reasons for SD Blocking:Some of them are-LAC boundary.HW Prob.

Solutions for removal of SD Blocking:Here are some steps by which we can reduce SD Blocking-Check the No. of SDCCH channel Available, if less then increase SD channel taking care that there is no TCH Blocking.Check LAC boundary, If location update is more then change the LAC of that site and set C2 and HYS.Use of Dynamic SDCCH (It is a BSC parameter and will be applied on whole BTS).Hardware check / shift SD to new time slotSome times BMA and HYS parameters are useful to remove SD Blocking.

Usefull Reports For SD Blocking:Use 182 to analyses SD Blocking reasons.130 for SD congestion.

SD Drop:As per diagram shows when we assigned SD for call origination and at that time due to some problem or any mismatch comes by which SD loss occurs, it is called as SD Drop.It occurs between allocation of SD and before TCH allocation. Sometimes SD drop occurs because queuing is not activated in the system. If SD drop is high plz look on parameters like- overshooting , shift the SD time slot , may be hardware issue, interference, change the values of RXP, PMAX, may be issue of uplink or downlink issue in that cells for UL put a TMA in that cell and for DL provide tilt ,re orient that antenna

If SD Drop is high:If SD drop is high plz look on parameters like- Overshooting Shift the SD time slot Hardware issueInterference Change the values of RXP PMAX It may be uplink or downlink issue in which cells for UL put a TMA in that cell and for DL provide tilt Re orient that antenna

Reasons of SD Drop:Hardware Fault.Interference.MAIO mismatch.Bad Coverage.High TR Fail.Outage.Overshooting.Abis Drop.High Path Loss.Wrong Parameter Planning.Due to ICM Band(CDMA)High LAPD UtilizationHeavy blocking and DR feature being used extensively

Solutions for removal of SD Drop:Interference:Check the BCCH Plan (C/I or C/A).Co-BSIC & Co BCCH.Use latest ND 111 and MapInfo to find out proper frequency to reduce interference.Arrange Drive Test:The best way to find the real issues for Interference makes DT.Check interference by Interference scanning.Check clean BCCH by frequency scanning.

Overshooting:LAC Planning.If a cell is picking call from long distance, Check the sample log according to TA.Cell orientation need to be defined according to clutter.Mount position Effective Tilt.

ContHigh TR Fail:Check and clear TR fail from OSS end.

Bad Coverage:If the drop call is due to low signal strength uplink, check the receive path of this particular TRX. Check receiver sensitivity, VSWR, feeder connection and etc. Drops due to Low Signal Strength.

If the drop call reason is due to low signal strength downlink, then, check the transmit path. Check cards, feeder and etc.

Use MapInfo or Google Earth to find location of sites.

Cont..

High LAPD Utilization:Check LAPD util report from OSS, and define 32 kbps signaling instead of 16kbps

Hardware Fault:Check Alarms.TRX condition.Check Path Imbalance.VSWR of the Cell.Connector Connection.Some times you will find issues on BCCH TRX.In this case BCCH shift from one to other TRX will reduce SD drop.

Cont

Due to ICM Band(CDMA):Some time SD drops takes place due to near sites of CDMA.

Check the ICM band value of that site.

Use BPF (Band pass filter).

Use the spectrum analyzer.

Cont..

Check for parameter:Check the Timer T 3101

Check the Timer T 200(20ms)

T11 Expired(10 s)

MAIO check.

Useful Reports for SD Drop:Use report ZEOL to find the alarms.Use 208 for Path loss analysis.Use 196 for UL-DL Interference.Use 163 report for SD drop.Use report 216 for detail SD Drop.232 report for TA report.62 for Adj cell having same or adj freq.ND 111 for freq plan.204 for BTS and cell report.

TCH Blocking:When TCH is not allocated to the user after SD allocation ,it is TCH Blocking.It is the failed call attempts which the MS user can notice. It takes place due to lack of TCH Resource.

Reasons for TCH Blocking:Some of them are-High Utilization of TCHTime slot faulty.Lock TRXs.HW Problem.

Solutions for removal of TCH Blocking:Implement half rate or Dual rate.Check FRL & FRU.Add another TRX.If TRX addition not possible, try to share the traffic of that cell with the neighboring cell by changing tilt or orientation.

Useful Report for TCH Blocking:135 TCH CongestionYAHA TAK PADTEIN HAIN AAJ

TCH Assignment:Its a process of by which TCH is assigned to the MS.After the SD request MS gets TCH successfully and the call transfers to TCH it means TCH assignment is successful.For the best KPI TCH assignment should tend to 100%.It degrades due to HW problems.

Reasons for TCH Assignment failure:Hardware Fault(TRXs,Combiner,Duplexer,Cables)VSWRHigh Path Loss.Faulty TMA.High TCH Blocking.Loose connections.DR being used extensively

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