GSMTo understand KPI Parameters

KPI PARAMETERS• KPI’s or Key Performance Indicators are the Parameters Fixed by

the Service provider to Monitor and Judge the Performance of their

Network , on daily basis , in co-ordination with Circle D&P Team .• The Parameters , covered are :• HLR• VLR• Radio NBH (Network Busy Hour)• Radio BBH (Bouncing Busy Hour)• Switch BH• D1• D3

HLR• The HLR is considered as a very important database that stores

information of the subscribers belonging to the covering area of a MSC. It also stores the current location of these subscribers and the services to which they have access.

• The location of the subscriber corresponds to the SS7 address of the Visitor Location Register (VLR) associated to the terminal.

VLR The VLR contains information from a subscriber's HLR necessary in order to

provide the subscribed services to visiting users. When a subscriber enters the covering area of a new MSC, the VLR associated to this MSC will request information about the new subscriber to its corresponding HLR. The VLR will then have enough information in order to assure the subscribed services without needing to ask the HLR each time a communication is established.

The VLR is always implemented together with a MSC , so the area under control of the MSC is also the area under control of the VLR.

Radio Traffic

Radio traffic: Half rate traffic + Full rate trafficHalf rate: Speech rate: 6.5kbps Data: 4.8KbpsFull rate: Speech Rate:13Kbps,Data: 9 Kbps

Radio NBH : Network Busy Hour :This is the sum of half rate and full rate traffic of busiest hour of the network. This is generally in between 7-8, 8-9 or 9-10 PM.

Radio BBH : Bouncing Busy Hour :This is sum of half rate and full rate traffic of each cells into the network with respect to its busiest hour in the whole day.

Switch BH

• Switch Busy Hour =(NTRALACCI + NTRALACCO)/NSCANWhere NTRALACCI= Accumulated traffic level IncomingNTRARACCO= Accumulated traffic level outgoingNSCAN = Number of accumulation (Scan)

• In NTRALACCI, the counter value of TRALI is measured.

• TRALI: Number of occupied devices on the route (incoming traffic level), it isincremented when a device is occupied on an incoming routes and it isdecremented when a device becomes idle on an incoming route.

In NTRALACCO, the counter value of TRALO is measured.

TRALO: Number of occupied devices on the route (outgoing traffic level), it isincremented when a device is occupied on an outgoing routes and it is decrementedwhen a device becomes idle on an outgoing route.

D 1

• DescriptionA drop on SDCCH does not mean a failed call set-up since it can be used for procedures thatonly require an SDCCH like a location area update or SMS. In fact as the SDCCH holdingtime for call set-up is just under 3 seconds and about twice as long for SMS, drops for SMSshould be over represented.

The KPI does not include released SDCCH connection due to TCH or transcoder congestion(i.e. the CNRELCONG counter), as it is seen in the TCH assignment success rate KPI.The drop rate is related to all SDCCH establishments in the cell; no compensation has beendone for SDCCH handovers, but as the mobiles normally camp on the SDCCH a short timeSDCCH handover occur seldom.

A high SDCCH drop rate may be due to: Poor coverage Interference Equipment faults (e.g. BTS or mobile related)

D 3Description

• To capture the subscriber perceived drops in a cell the number of calls terminated in the cell are considered, i.e. compensation is done for incoming and outgoing hand-over's for all internal and external cell relations. It is important to note that the TCH drop counters are stepped as soon as a TCH is established even if there has yet not been any B-answer, this is also applies when TCH is used for signaling. If the TCH is dropped before the B-answer the subscriber will experience it as a failed call set-up rather than a dropped call. If TCHs are used extensively for signalling one reason for increased TCH drops could be transcoder congestion, it can be seen in the counters THNRELCONG, THNRELCONGSUB, TFNRELCONG and TFNRELCONGSUB.

• TCH connections that are lost are during handovers are also seen as TCH drops in the counters.

• If Adaptive Multi Rate (AMR) is used the subscriber will experience better speech quality and is more likely to hold on to the call until it drops rather than disconnecting the call due to poor speech quality, thus the drop rate might increase slightly when AMR is introduced. There are separate dropped call counters for AMR, which allows drops for AMR connections to be monitored separately.

As HOVERSUC includes successful SDCCH hand-overs, the drop rate on cell level can be skewed if there are a large number of SDCCHhand-overs. The mobile though camps on the on the SDCCH only a short period of time and number of SDCCH hand-overs is normallysmall compared to the total number of TCH assignment, typically less than one percent.

A high TCH drop rate may be due to: Poor coverage Interference Hardware faults (e.g. transcoder, BTS or mobile related) Subscriber behavior (e.g. causing sudden loss by entering an elevator or pulling out the battery) Handover failure Too high timing advances (TA)

FORMULA

• 1. SDCCH DROP% (DROP 1)

CNDROP * 100CMESTAB

• 2. TCH DROP% (DROP3)

TNDROP * 100TCASSALL

• 3. TCH set-up success rate

(CCALLS-CCONGS) * (CMESTAB-(CNDROP-CNRELCONG) * TCASSALL * 100 CCALLS CMESTAB TASSALL

• 4. Subscriber perceiver Congestion Or Blocking

CNRELCONG + TNRELCONG• TASSALL

•

• 5. Network Perceived Congestion

TCONGAS + TCONGSHOTCALLS

•

• 6. SDCCH Congestion

CCONGS * 100CCALLS

•

• 7. HO Success Rate

(SUMOHOSUCC + SUMEOHSUCC) (SUMOHOATT + SUMEOHATT)

• 8. No. of HO Decisions

(HOTOLCL + HOTOKCL +HOUPLQA + HODWNQA + HOEXCTA +HOASWCL + HOATTLSS + HOATTHSS + HOTOHCS)

• 9. HO Attempts To Ho Decisions

HOCNT (No. of HO Decisions)

10. Ping Pong Ho

HODUPFTHOVERSUC

11. Random Access Attempts

CNROCNT+ RAACCFA

12. Random Access Success

CNROCNT (CNROCNT + RAACCFA)

•13. Answer to Paging total Random Access

RAAPAG *100% RAAPAG+ RAOTHER+ RAEMCAL+ RACAL+ RAOREQ

• 14 .Mobile Originated Random Access

RAOREQ *100% RAAPAG+ RAOTHER+ RAEMCAL+ RACAL+ RAOREQ

•

• 15. Rejected Immediate assign•

• CNROCNT- (RAAPAG+ RAOTHER+ RAEMCAL+ RACAL+ RAOREQ ) * 100 CNROCNT•

•