Handover failure

[kass33]

Hello,

I had a handover failure but i don't understand why. Below the log message for layer 3 :


106702 14:20:00.798 L3 DL RR Handover Command
BCCH: 49 BSIC: 00(dec) 00(oct)
Channel Type: TCH/F + FACCH/F and SACCH/F
TimeSlot: 6 TrainingSeq: 0
Hopping: Yes, MAIO: 2 HoppingSeq (HSN): 50
HandoverRef: 38 OrderedPowerLevel: 5
Target CA List: 34 46 (Variable Bit Map)
Channel Mode: Speech full rate or half rate version 3 (AMR FR/HR)
AMR - Multirate speech version 1:
Codec Count: 1
Codec Mode 1: Codec 12.20kbps,
Initial Codec Mode Indicator: Use Default
Initial Codec Mode: Codec 12.20kbps
Signal handoff from CHINON_EDF(CHINON_EDF_3) to Unknown(Unknown)

106703 14:20:00.798 Nemo Handover Attempt

Context Id: 152
Number of header parameters: 1,
Handover/handoff attempt type: GSM handover between cells,
Current cellular system: GSM,
Number of current system parameters: 3
Channel number: 20,
Timeslot number in use currently: 0
Band: GSM 900
Attempted cellular system: GSM,
Number of attempted system parameters: 3
Attempted channel number: 49,
Attempted timeslot: 6,
Band: GSM 900
106704 14:20:00.798 Nemo AMR Status
Cellular system: GSM
AMR Mode uplink: Codec 4.75kbps
AMR Mode downlink: N/A
AMR Last mode command: Codec 4.75kbps
AMR Last mode request: N/A
AMR Channel Type:
106705 14:20:00.798 Nemo AMR Link Quality Estimate

Cellular system: GSM,
AMR Link quality estimate (dB): 24.0 dB
106706 14:20:00.888 Nemo GPS information

Longitude: 0.107943,
Latitude: 47.2727,
Height: 20.000000 m,
Distance: 214653,
GPS fix quality: with GPS,
GPS satellites: 9, Velocity(km/h): 135 kph
106707 14:20:00.968 Cell measurement (CELLMEAS)

Cellular System: GSM
Band BCCH BSIC RxLev RxLevSub C1 C2 C31 C32 HCS HCS Cell ID LAC RAC Srxlev
Serv: GSM 900 20 2 -85 -84.0 - - - - 0 - 64604 18690 1 -
Neig: GSM 900 36 11 -89 - - - - - - - - - - -
Neig: GSM 900 23 21 -90 - - - - - - - - - - -
Neig: GSM 900 10 35 -92 - - - - - - - - - - -
Neig: GSM 900 49 0 -94 - - - - - - - - - - -
Neig: GSM 900 4 0 -96 - - - - - - - - - - -
Neig: GSM 900 29 23 -97 - - - - - - - - - - -
Neig: GSM 900 7 5 -98 - - - - - - - - - - -
Neig: GSM 900 15 - -100 - - - - - - - - - - -
Neig: GSM 900 12 1 -101 - - - - - - - - - - -
Neig: GSM 900 11 25 -101 - - - - - - - - - - -
Neig: GSM 900 1 - -101 - - - - - - - - - - -
Neig: GSM 900 2 34 -102 - - - - - - - - - - -
Neig: GSM 900 3 20 -103 - - - - - - - - - - -
Neig: GSM 900 25 4 -104 - - - - - - - - - - -
Neig: GSM 900 30 16 -104 - - - - - - - - - - -
Neig: GSM 900 14 17 -104 - - - - - - - - - - -
Neig: GSM 900 6 15 -105 - - - - - - - - - - -
Neig: GSM 900 9 - -106 - - - - - - - - - - -
Neig: GSM 900 47 - -106 - - - - - - - - - - -
Neig: GSM 1800 608 - -112 - - - - - - - - - - -
106708 14:20:00.968 Carrier Per Interference (CI)

Cellular System: GSM
Number of timeslot C/I measurement results: 0
Channel C/I: 15.6 dB
Number of channels: 3,
ARFCN C/I (dB) RSSI (dBm)
5 15.10 -84.90
8 15.80 -85.60
16 16.00 -86.70
106709 14:20:00.968 Nemo AMR Status
Cellular system: GSM
AMR Mode uplink: Codec 4.75kbps
AMR Mode downlink: Codec 4.75kbps
AMR Last mode command: Codec 4.75kbps
AMR Last mode request: N/A
AMR Channel Type:

106710 14:20:00.968 Nemo AMR Link Quality Estimate

Cellular system: GSM,
AMR Link quality estimate (dB): 22.0 dB
106711 14:20:01.887 Nemo GPS information

Longitude: 0.107537,
Latitude: 47.2729,
Height: 20.000000 m,
Distance: 214691,
GPS fix quality: with GPS,
GPS satellites: 9, Velocity(km/h): 135 kph
106712 14:20:02.887 Nemo GPS information

Longitude: 0.107127,
Latitude: 47.2731,
Height: 20.000000 m,
Distance: 214729,
GPS fix quality: with GPS,
GPS satellites: 9, Velocity(km/h): 135 kph
106713 14:20:03.888 Nemo GPS information

Longitude: 0.106713,
Latitude: 47.2733,
Height: 20.000000 m,
Distance: 214766,
GPS fix quality: with GPS,
GPS satellites: 8, Velocity(km/h): 135 kph
106714 14:20:03.968 Nemo Handover Failure

Context Id: 152



Could you please from the log above give me an idea about the handover failure ?

Thx in advance

[yurii]

Hi kass33

you should pay atention : mobile does not detect any BSIC it can not have value =0
target cell BCCH=49 ch and bsic = 0 ( if I understand correctly you log )
But to solve this situation I think is to insatll new site ( cause you do not have good coverage in that place...or maybe to install new DCS cell on closer site in that direction--- to improve coverage )
...or try to scan all band to find undeclared neighbor cell !

another way is : try to analyse if target cell with BCCH = 49 can have the same BCCH ( 20 ch ) declared as neighbor !!!

BR
your friend

[stilloboy]

Hello,

I had a handover failure but i don't understand why. Below the log message for layer 3 :


Could you please from the log above give me an idea about the handover failure ?

Thx in advance

I believe, from the limited data you've provided, the target cell suffered from poor DL coverage, as the following picture shown below indicates, since Rxlev of target cell = -94dBm < -84dBm - which can be considered poor.

KRs,
Stilloboy

[kass33]

Thx for your response, but why i could not see your attachment ?
BR,

[zhanglw268]

From your message, it looks like that it is a handover due to congestion in the serving cell with AMR half rate, the system found that an congested cell freq 49 with weak coverage than the serving cell, ordered the mobile going to Full rate with hopping informaion on timslot 6 of the BCCH, but hopping message content seems wrong, but there was no other message to show how mobile acted when it tried the handover.

Check the hopping settings and also check other messages to narrow down the problem.

[DaSlasher]

From the logfile analysis...it looks like handover attempt was happening to a worst nbr (could be due to CLS/congestion) which had DL SS 10dB lower than the server. This could mean that this cell is located very far from the server effecting higher pathloss on the UL and also there could be some other cell with the same BCCH 49 or adj channel 48/50 that caused interference on this 49 0 cell. Also, there could be some HW issues on this target cell...perhaps the UL is even much weaker, Hence the handover access msg on the UL from the MS couldn't be decoded.
Please check the HO stats of the source cell and see if handover attempts to this 49 0 cell are always successfull or not...there could be some other cell with the same BCCH-BSIC 49-0 in the area (change the BSIC on one of them).