Belajar KPI

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Belajar KPI

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Contoh Kasus:

OJT KPI Sumalirja

By : Robertus Pekujawang

Contoh Kasus:

1. SDSR decrease on Sawangan Sector 2 and 3 cause traffic drop (20 August 2007)

BSC:33 / BTSM:23 If SDSR decrease, there are 3 possibilities reason why : caused by blocking (SDCCH addition), hardware problem, or interferrence.

Check on Batrana what makes SDSR decrease.

By checking on Batrana, SD blocking is zero and by checking on Map info there is no interference, so temporary conclusion, this problem was caused by hardware problem. Ask to scan alarm by OMC. (cari log alarm dari OMC) (gambar Mapinfo tgl itu) (gambar Batrana)2. DCR increase on Sinon Sayang (20 August 2007)

By checking on MapInfo, sector 2 has no adjacent to site Motoling, so when MS go far away from Sinon Sayang, signal strength from Sinon Sayang decreases and there is no adjacent to handover to, or available adjacent too weak (compare to handover treshold) for MS to handover to. When signal strength goes to minimum value, drop call occur. By checking on Batrana, most failed happen due to Radio Link Failure and T200. Considering MS condition on hilly area RDLNKTO then set to 15 (default : 7, max : 15) to give more chance for MS to try (more failure before decide to drop). RDLNKTO and PCRLFTH also set to a value in relation to RDLNKTBS based on formula. T200 set to a higher value. Every time check a site, make sure that neighbourhood already complete.

070820_Sumal_Aldo_101Cell NameBSCBTSMBTSNObjectNoParameterNew ValueOld Value

Sinon Sayang5761BTSRDLNKTO1512

1PWRC0RDLNKTBS6452

1PWRC0PCRLFTH6048

1BTST200145-31-38-90-70-29-16888-62-62-180-180-90-135

2BTSRDLNKTO1512

2PWRC0RDLNKTBS6452

2PWRC0PCRLFTH6048

2BTST200145-31-38-90-70-29-16888-62-62-180-180-90-135

(gambar dari MapInfo) (gambar dari Batrana) (gambar dari KPI Tool)T200 = LapDm Timer 200 (BTS timer , unit= 5 ms and 10 ms) Parameter format: sdcchSAPI0 - facchTCHF - facchTCHH -sacchTCHSAPI0 - sacchSDCCH sdcchSAPI3 -sacchTCHSAPI3.Should be set in correspondence with the channel mapping and channel characteristics on the radio interface. When the BTS transmits a DL layer-2 frame on the air the BTS starts the timer T200 and waits for the acknowledgement frame from the MS. If the acknowledgement from the MS is not received within T200 the transmission of the layer 2 frame is repeated and T200 restarted. The total number of repetitions is restricted to N200, a fixed value specified by GSM which depends on the control channel types:

N200(SDCCH)=23, N200(SACCH)=5,

N200(FACCH/FR)=34, N200(FACCH/HR)=29

If T200 expires after the last layer 2 frame repetition the BTS sends

an ERROR INDICATION with cause .T200 expired N200+1 times. (followed by a RELEASE INDICATION) message to the BSC, which releases the associated resources (Call Drop).RDLNKTBS = Radio Link Time Out BS (Radio link counter BS) (Downlink)Define initial value of counter S within the BTS. Every time the BTSM/MS unable to decode a SACCH message on the uplink/downlink, S counter is decrement by 1, vice versa incremented by 2. As soon as the counter S in the BTS reaches 0, a Connection Failure Indication message with cause radio link failure is sent to BSC and the BSC initiates a release of the concerned connection (Call Drop).

RDLNKTO = Radio link timeout MS (counter) (Uplink)

Similar to RDLNKTBS but for MS. If S reaches 0, the connection is released and MS return to idle mode (This action caused Call Drop).Relationship between RDLNTBS and RDLNKTO =

S = 4 + 4 x RDLNKTO

S= RDLNKTBS so RDLNKTBS = 4 + 4 x RDLNKTO or vice versaPCRLFTH = Power control radio link failure thresholdIf the RDLNKTBS decrease and reach PCRLFTH value (thats why RDLNKTBS > PCRLFTH), the BTS immediately increases the BS and MS transmit power to the maximum.

Note : this parameter only relevant if if the parameter related to power control set to true.

EPWCRLFW = TRUE

Addition:

EMSPWRC = (Adaptive, Classic, or Disable)

EBSPWRC = (Adaptive, Classic, or Disable)

BBHOP => EBSPWRC = Disable atau Adaptive

SFH => EBSPWRC = Classic atau Adaptive

EMSPWRC selalu aktif.

3. High DCR and TCHB on Wakal Sector 1, Drop HOSR on another sector (20 August 2007)

Configuration of this site is 2/4/4 (BSC:58/BTSM:12) Because TCHB on Sector 1 is very high, maybe one TRX down on this sector. This conclusion taken by calculating the erlang use erlang calculator (www.erlang.com/calculator/erlb)

Because one TRX on Sector 1 is down thus it caused HOSR drop on another Sector because MS on another sector can not perform handover to sector 1. Ask to scan alarm by OMC. (cari log alarm dari OMC) (Cari data get kpi tanggal ini) (contoh kalkulator erlang) (gambar batrana)

4. Drop HOSR on Sawangan (21 August 2007)

By checking on DbTree all adjacent already complete, but by tracking using MapInfo we found out that adjacent to surround site suddenly vanish. This problem was caused by rehoming of surround site of Sawangan by unknown party without LAC update on TGTBTS.

Ask RDP to update TGTBTS.

(gambar Mapinfo)5. DCR increase on Sinon Sayang (27 August 2007) BSC:57, BTSM:6 By checking CTRX report on Batrana, the visualization of RXLEV to RXQUAL and RXLEV to TA on sector 2 and 3 look weird, thus possibility reason for this case is hardware problem.

Ask to scan alarm by OMC.(cari log alarm dari OMC) (cari gambar Batrana)

RXLEV vs TA

RXLEV vs RXQUAL

6. DCR increase on Sinon Sayang (28 August 2007) BSC:57, BTSM:6 Justification: Contour (use Google Earth and Global Mapper).

Attempt and Drop comparison on Batrana (low traffic, so even small drop, in

Percentage become big).

CU perftest on OMC to find out the condition of CU.

RDLNKTO and T200 set to maximum value.(cari action list) (cari getKPI)070829_SuLutMalGo_Maya_101

Cell nameBSCBTSMBTSNObjectNoParameterNew ValueOld Value

Sinon Sayang GSM5760HAND0ENAQUALEVHOMTRUEFALSE

5760HAND0MAXFAILHO32

5760HAND0HOAVLEV6-24-2

5760ADJC0QUALLEVHOM7069

5760ADJC1QUALLEVHOM7069

070830_SuLutMalGo_Maya_101

Cell NameBSCBTSMBTSNObjectNoParameterNew ValueOld Value

Sinon Sayang GSM5760BTSRDLNKTO1512

5760PWRC0RDLNKTBS6456

5760PWRC0PCRLFTH6052

5760BTST200175-100-100-175-175-90-17588-62-62-180-180-90-135

7. Drop HOSR on Sawangan Sector 3 and 1 (4 Sept 2007) BSC:33 / BTSM: 23 Check on Handover report at Batrana and find out on what adjacent more handover failure happen. On sector 1 it seem that failure happen on its adjacent no. 1 and 2 on table Uplink Strength (UL).

Parameter setting in relation to strength or level (HOLTHVDL,HOLTHQUUL) > parameter set to be higher => so it need more time before condition for HO reached

On sector 1 handover failed due to better cel = 0 (Handover failure commonly happen due to Quality and Level => very small on Quality because even on low level, quality is good => failure on quality commonly caused by interferrence). So handover is planned it hard to handover due to level but easier due to better cell. In this case ELEVHOM set to TRUE, LEVHOM set to a bigger value, and HOM set to a smaller value. On sector 3 SDSR value so close to acceptance value. By checking on Batrana, it caused by T200, so T200 then set to a bigger value.

HOSR on sector 3 also bad. By checking on Batrana, the problem almost equal to sector 1, thus action taken equal to sector 1.

(cari gambar Batrana) (cari action list)

070904_Sulutmalgo_Aldo_101

Cell nameBSCBTSMBTSNObjectNoParameterNew ValueOld Value

Sawangan GSM33230HAND0HOLTHQUDL65

0ADJC0LEVHOM7169

0ADJC0HOM6369

0ADJC1LEVHOM7169

0ADJC1HOM6369

2BTST200145-31-38-90-70-29-16888-62-62-180-180-90-135

2HAND0ELEVHOMTRUEFALSE

2ADJC0LEVHOM7169

2ADJC0HOM6369

2ADJC1LEVHOM7169

2ADJC1HOM6369

HOLTHQUDL = Handover lower threshold quality downlink (5= 3,2% to 6,4%; 6= 6,4% to 12,8%) In this case will give more tolerance to higher BER. Defines the receive signal quality threshold on the downlink for inter-cell quality handover decision.

ELEVHOM = Enable level handover margin (FALSE/TRUE)LEVHOM = Level handover margin (unit:1db, 69 = 6 dB, 71 = 8dB)

The level handover is triggered if the UL or DL receive level of the serving cell falls short of the thresholds HOLTHLVUL resp. HOLTHLVDL. (In case of Handover due to Level/Strength)

If ELEVHOM = FALSE

the target cell only has to fulfil the handover minimum condition

RXLEV_NCELL(n) > RXLEVMIN(n) + Max(0,Pa).

to be included in the target cell list of the INTERCELL HANDOVER CONDITION INDICATION with the cause values uplink strength or downlink strength.

If ELEVHOM = TRUE

also the level difference between the serving cell and the neighbour cell (power budget PBGT) is considered. In this case the neighbour cell only appears in the target cell list if its power budget exceeds the entered level handover margin:

PBGT(n) > LEVHOM(n)

in addition to the handover minimum condition. (Better Cell)HOM = Handover margin (unit:1db, 63 = 0 dB, 69 = 6dB)

This parameter defines a threshold for the power budget handover (handover to another cell if this cell

offers a higher transmission level (irrespective of whether the power level of the actual cell is above the minimum)) In this case PBGTHO must be true.Handover triggered if the power budget of a specific neighbour cell exceeds the handover margin set for the ADJC object representing this cell.8. Drop HOSR on Sinon Sayang sector 1 (4 Sept 2007)

DCR already good but HOSR getting worse on sector 1.

By checking database using DbTree, RACHBT had set to 114 by unknown party thus set to it default value 109.

By checking on Batrana there are a lot of failed caused by BC and Strength.

ELEVHOM set to true, HOM set to a bigger value (handover due to better cell will be more difficult), LEVHOM set to a bigger value.

070904_Sulutmalgo_Aldo_101

Cell nameBSCBTSMBTSNObjectNoParameterNew ValueOld Value

Sinonsayang5760BTSRACHBT109114

1BTSRACHBT109114

2BTSRACHBT109114

0HAND0ELEVHOMTRUEFALSE

0ADJC0HOM6966

0ADJC0LEVHOM7169

0ADJC1HOM6966

0ADJC1LEVHOM7169

RACHBT = RACH busy thresholdThis attribute defines a threshold for the received signal level during network access and handover access. A signal level exceeding this threshold is interpreted as a busy RACH or a busy FACCH (when transmitting CHANNEL REQUEST (RACH) or Handover ACCESS (FACCH)).Minimum signal level threshold an MS can use RACH.Dilapangan biasanya setting RXLevAmi bersamaan dengan setting RACHBT dimana apabila RxlevAmi diperbesar maka semakin mudah MS untuk mengakses channel sehingga walaupun Rx Levelnya besar apabila RxLevAmi dan RACHBTnya belum mencapai sesuai dengan yang disetting maka MS tidak akan dapat mengakses channel . RXLEVAMI dapat mengurangi jumlah handover.Adalah threshold untuk level signal RACH. Tujuan utama dari parameter ini adalah untuk menghindari beban SDCCH yang tidak perlu. BTS akan mengukur level signal tiap timeslot RACH dan menentukan apakah signal request diterima atau tidak. Jika signal terima lebih besar atau sama dengan nilai RACHBT maka RACH burst akan diindikasikan BUSY (ada satu atau lebih MS yang mengakses jaringan)KPI Value

SDSR (SDCCH Successfull Rate)

Stand-alone Dedicated Common Control Channel (SDCCH) is a signalling used for call initialization, sms, and location update. SDSR is a ratio between total successfull SDCCH to total attempt by MS to get SDCCH.Acceptance value by Telkomsel for SDSR :For GSM/Stand Alone DCS : Urban = 93.00 %

Sub Urban = 92.50 %

Rural = 91.50 %

For Co-Located DCS :Urban = 97.40 %

Sub Urban = 98.10 %

Rural = 95.80 %

For Indoor Coverage :Indoor Stand Alone = 98.30 %

Indoor Collocated = 97.00 %

Checking Step: 1. Check a site on KPI Monitooring tool if SDSR decrease.

2. Check on Batrana what make SDCCH failed or blocked (high traffic) e.g. SD_Drop_Radiolink_failure, SD_Drop_T200, SD_Drop_unidentified, then set related parameter.

3. Also check on MapInfo if interferrence happen, and ask RNP to retune if needed.

4. Ask OMC to scan alarm to check hardware status.

HOSR (Handover Successfull Rate)

Handover that monitored by KPI team are only outgoing and intra BSC handover.

HOSR is a ratio between successfull handover to total handover attempt.

Acceptance value by Telkomsel for HOSR :

For GSM/Stand Alone DCS : Urban = 92.00 %

Sub Urban = 90.00 %

Rural = 87.00 %

For Co-Located DCS :Urban = 95.00 %

Sub Urban = 94.00 %

Rural = 95.10 %

For Indoor Coverage :Indoor Stand Alone = 93.00 %

Indoor Collocated = 94.50 %

There are four reason for MS to do handover :

1. Quality

Handover due to quality occur when quality (BER or FER) of sinyal received by MS fall to a value below treshold. If value for treshold set to a higher value it mean that system will be more tolerance to signal quality so it will need more time before treshold reached (handover occur) and vice versa for a smaller value. Failure on handover due to quality generally very small, because even on low level or low strength signal, quality still good enough. Main reason for failure on handover due to quality is interferrence because it make quality go very bad.

2. Level or strength Handover due to level or strength occur when level of sinyal received by MS fall to a value below treshold. If value for treshold set to a smaller value it mean that system will be more tolerance to signal level so it will need more time before treshold reached (handover occur) and vice versa for a higher value. This kind of handover can combined to handover due to better cell by applied another parameter i.e ELEVHOM, LEVHOM and HOM. If ELEVHOM = TRUE, also the level difference between the serving cell and the neighbour cell (power budget PBGT) is considered. In this case the neighbour cell only appears in the target cell list if its power budget exceeds the entered level handover margin:

PBGT(n) > LEVHOM(n)

in addition to the handover minimum condition.3. Distance

Handover due to distance occur when MS reach treshold define how far a MS can go. This treshold closely related to Timing Advance (TA).

4. Better Cell

Handover due to better cell occur when signal level received by MS from neighbour site is better than serving site.

Checking Step:

1. Check a site on KPI Monitooring tool if HOSR decrease.

2. Check on Batrana handover report what make handover failed based on handover kind : Quality, Strength or Level, Power Budget, and Better Cell. Set related parameter to repair a handover type or to combine those kind of handover type to get better HOSR. Failed handover on quality generally caused by interferrence, and ask RNP to retune.3. Check on database if there are parameter set or change to not recommended value and repair it to a recomended value.

4. Check neighbourhood and interferrence on MapInfo.

DCR (Drop Call Rate)There are three reason for Drop Call :1. Full

2. Radio Link Failure

3. InterferrenceDCR is a ratio between drop call to total call made by subscriber.

Acceptance value by Telkomsel for HOSR :

For GSM/Stand Alone DCS : Urban = 0.70 %

Sub Urban = 0.95 %

Rural = 1.15 %

For Co-Located DCS :Urban = 0.50 %

Sub Urban = 0.40 %

Rural = 0.65 %

For Indoor Coverage :Indoor Stand Alone = 0.4 %

Indoor Collocated = 0.3 %

Checking Step:

1. Check a site on KPI Monitooring tool if DCR increase.

2. Check on Batrana what make a call to drop e.g. TCH_Drop and TCH_Attempt, TCH_Drop_Radio_Link_Failure, TCH_Drop_T200, TCH_Drop_Remote_Transcoder_Failure. Set related parameter to repair DCR.

TCHB (Traffic Channel Blocking)

BHT (Busy Hour Traffid)

RLF Counter S

SACCH Frames

decoded SACCH message

not decoded SACCH message

Radio Link Failure Warning Power Command

Radio Link Failure

RADIO_LINK_TIMEOUT = 8

PC_TIMEOUT = 2