KPI ANALYSIS.pdf

7/25/2019 KPI ANALYSIS.pdf

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KPI ANALYSIS

REASONS 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 BSC

One BSC = One LAC

One BSC= 660* 8 = time slots but if dual rate isimplemented that it consider as two slots.

One BSC= two Lac also but for city one LAC b/c iteffects 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 whichsupports 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 BSC

1TRX=117 subscriber

1 subscriber=25 m erlangs (TCH)

1 subscriber=.004 m erlangs(SD)

1 TRX=2.94 erlang(2% GOS )




If BSC 3VI, OSS is 4 and System is S11 then max capacity ofBSC is 660 TRXs.

If OSS 4.2 and system S12 is using then max capacity of BSCwill be 2000TRXs



KPI’s to be monitored

SD Blocking

SD Drop

TCH Blocking

TCH Assignment TCH Drop

HOSR



9295HOSR31.5TCH Drop

9898.5TCH Assignment

0.50.5TCH Blocking

1.71.2SD Drop

0.50.25SD Blocking

Non-ShowcaseThreshold

ShowcaseThreshold

ParameterKPI’s to be monitored



Get

ServiceGetSDCCH

EstablishSD Channel

Est. TCHConn.

Call Phone Ref. Phone

SD Blking

SDCCH Seizer

TCH Blking

CSSR or TCH

Assignment

Call Establishment

Call completionRate (TCH Dropcall)



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 linkfailures,HW problems or many other reasons.

If a call is abnormally disconnected, a Clear Requestis sent to the MSC .If the Call is disconnected in anormal Fashion then Clear Message with cause codeCall Control is sent. It is important to establish what

types of calls are failing, and over what percentage ofthe network it is occurring.



SDCCH CHANNEL :

SDCCH is a dedicated channel which isusing 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. WhenMS connects with NW then RACH and AGCHare provided. After AGCH,SDCCH isprovided but if SDCCH is not provided at this

time due some problems or due tounavailable of SD by BSC ,it’s called as SDBlocking. There are no of reasons for that.If

such a case arises the customer will not beable to originate any call.



Difference Between Blocking and

Congestion:

It is very important to know difference

between blocking and congestion. Somepeople think that both are same, but theydiffer from each other. If all the SD resources

are full and not available for SD assign thenits come into congestion. If at a particulartime 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 SDBlocking-

1. Check the No. of SDCCH channel Available, if less thenincrease SD channel taking care that there is no TCH Blocking.

2. Check LAC boundary, If location update is more then change theLAC of that site and set C2 and HYS.

3. Use of Dynamic SDCCH (It is a BSC parameter and will beapplied on whole BTS).

4. Hardware check / shift SD to new time slot

5. Some 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 callorigination and at that time due to some problem or any

mismatch comes by which SD loss occurs, it is called asSD Drop. It occurs between allocation of SD and before TCH

allocation. Sometimes SD drop occurs because queuingis not activated in the system.

If SD drop is high plz look on parameters like-overshooting , shift the SD time slot , may be hardwareissue, 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 orientthat antenna



If SD Drop is high:

If SD drop is high plz look on parameters like-

Overshooting Shift the SD time slot

Hardware issue

Interference Change the values of RXP PMAX

It may be uplink or downlink issue in which cells for ULput 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 Utilization Heavy 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 properfrequency 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.



Cont…

High 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 signalinginstead 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 caseBCCH 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 ofCDMA.

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 TCHResource.



Reasons for TCH Blocking:

Some of them are-

High Utilization of TCH

Time 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 thetraffic of that cell with the neighboring cell bychanging tilt or orientation.



Useful Report for TCH Blocking:

135 TCH Congestion



TCH Assignment:

It’s 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 shouldtend to 100%.

It degrades due to HW problems.



Reasons for TCH Assignment failure:

Hardware

Fault(TRXs,Combiner,Duplexer,Cables) VSWR

High Path Loss.

Faulty TMA.

High TCH Blocking.

Loose connections. DR being used extensively



Solutions for removal of TCH Assignment:

Clear VSWR IF TRXs are faulty lock them and try to replace

them soon to avoid blocking Path Imbalance clear. Connection from BTS to Antenna

Connector connection Check TMA. Check Duplexer,Combiner,TRXs

connections,Multicuppler etc. Check BOIA card. Check BB2F Card.



Reports for TCH Assignment:

ZEOL to check alarms 208 for path imbalance

196 for UL-DL interference

ZAHP for Flick report



TCH Drop:

Drop during conversation is known as TCH

drop. It takes place after connect ACK msgon TCH.TCH drop occurring.

For TCH drop first cross check the BCCH of

that cell, hardware issue may be, changeRXP and RLT value. Find out there is anyinterference ,neighbor defined.



Reasons for TCH Drop:

Wrong Parameter Planning.

BAD HOSR. Hardware Fault.

High TR Fail.

Overshoot.

Outage.

Due to Low Coverage.

Due to ICM Band(CDMA)



Solutions for removal of TCH Drop:

Check Parameter:

Check the BCCH Plan (C/I or C/A). Co-BSIC & Co BCCH.

Check the Timer T 100(should be 20 ms)

Check Overshooting: If a cell is picking call from long distance,

Check the sample log according to TA..

Site Orientation.

Effective tilt should be check.

Mount position should be check



Cont..

Improve HOSR:

Check the Hopping plan.

Check the Neighbor Plan

High TR Fail: Check and clear TR fail from oss end.



Cont..

Bad Coverage:

If the drop call is due to low signal strength uplink, check thereceive path of this particular TRX. Check receiver sensitivity,

VSWR, feeder connection and etc. Drops due to Low SignalStrength.

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.

Effective tilt should be check.

Mount position should be check.



Cont..

Check HW:

Check Alarms on site.

Check TRXs.

Check Slips.

Check the Hopping plan.

Check BB2F card.

Check VSWR,

Path imbalance.

Connector Connection.

Check TMA



Cont..Drop Reason because of HW Issues: if drops are only on one site, then go for a check for that particular

even attach with that site.

If drops are on all sites connected to a single link, then check theslip or interference on that Abis interface.

If Drops are distributed on all site of the BSC, then check the slipson A-ter.

Down Time of the cell.

TRX condition.

BTS should not getting the temperature alarm continuously.



Reports for TCH Drop:

166 for TCH Drop

ZEOL for alarms.

ZAHP for Flicks.

232 for TA report.

208 Path Imbalance report.

204 for BTS report. 216 for all parameter.

196 for UL-DL Qul.




HOSR:

Hand over success rate:

If HOSR will be good TCH drop will also begood.

If Handover success rate degrades call drop

rate will take place.



Reasons for HOSR:

Improper Neighbor planning. CO-BCCH-BSIC issues in Neigh. Parameter Check. HSN clash. SL value.

LAC boundary. DAC value mismatch. Syn mismatch.

Overshoot. HW Issues. Low Coverage



Solutions for removal of HOSR:

Arrange Drive Test: The best way to find the real issues for HO fail make

DT and check layer 3 msg gor HO fail.By DT it is veryeasy to find the fail between cells.

Neighbor Tuning:

Try to retune neighbors Avoid CO-BCCH-BSIC neighbors.

Avoid extra neighs.

Delete long distance neighs. Check neighs are defined form both ends.

If there are high fail delete and recreate neighs.



Cont..

Parameter Check:

1. Retune SL.It can change bw -90,-95,-105.2. Check HSN.

3. Check SYN.

4. Retune LDR, LUR, IDR, IUR.5. Retune LMRG, QMRG, PMRG.

DAC value Check:

1. Check DAC value. If DAC value is high or low tune it atthe TH value. It should be 2050.



Cont..

Overshoot: When neighs are far away then chances of HO fail increases. In

this case ping-pong HI takes place by which fail takes place. So itthe inter distance is high its batter to del that kind of neigh.

LAC Boundary-

Check LAC boundry. High fail takes place there will be Inter BSC cells.

High fail takes place there will be Inter MSC cells.

Define proper LAC in neigh cells.



Cont..

HW Issues: Clear HW issues.

Check TRXs.

Check outages.

Check BOIA Card. Because if it is faulty incoming and outgoingHO will be fail.

Clear Reports: Clear ZEAT.

Clear 60.

Clear 67.

Clear 61.



Reports for HOSR :

153 reports for HO fail bw two cells.

154 HO analyses.

60 for discrepancy. 67 for Sync report.

61 for one way neigh.

ZEAT for CO-BCCH-BSIC neighs

74 for HO definition report.

ZELO for inter MSC HO report.

150 for high HO fail.

157 for high HO attempt and call ratio.

158 for intra BSS HO observation.




High RACH Failures:

Other reasons look for Random access

statistics, if there is a lot of random accessfailures try to check hardware too. It includesthorough hardware audit including CF

Reloading, IDB Setting and reloading,Software synchronization, filter check etc)

Al



Some Important Alarms:

BTS Operation Degraded (7604) - It shows VSWR on cell.

TRX Operation Degraded (7607)-It shows critical alarm on TRXs.

Channel Fail Rate (7745)-It shows faulty TS on TRXs. BCF Operation degradation ()-It shows DAC value alarm.

Ex-TCH Interference (7744)-TRXs faulty or back plan problem.

Mean Holding Time(7743)-to detect faulty channels.

Working SD Ratio Below TH level (7712)- .Its for the ratio of SDs.

LAPD Fail-TX link fail.

Antenna Connection Faulty (7606)-Shows faulty in cableconnections.

High Temp Alarm-TRXs begins fluctuating.



THANK YOU

- Anurag Srivastava

KPI ANALYSIS.pdf

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