wcdma ps call Drop caused by handover behaviour

[zeezzoo]

hi friends,

I need your help please .

i have a dropped call in PS drive test that caused by handover behavior.
the scenario is as follows :
1- active set contains SC1 . after that SC2 is added to the active set .
2- after adding SC2 , UE_Tx_Power started to increase
3- now SC2 is better than SC1
3- the UE sent MR asking for deleting SC1, but after 14 sec from adding SC2 , the utran deletes SC2 (the best link) .
4- after deleting SC2 , UE_Tx_Power still high . Ec/No is very bad ==> drop happens

i checked RTWP for SC1 & SC2 :
SC1 -91
SC2 -86

but after the drop , a new call was established on SC2 (with a bigger distance from the site) with lower UE_Tx_Power .

can you help ???

[KoJaa]

You might have an undefined neighbor near you dt route. It seems to me that the system automatically disconnects you as the ue detected a cell that is stronger by around 12 db than your active set but not present on you neighbor lists. The system does that to prevent further interference


hi friends,

I need your help please .

i have a dropped call in PS drive test that caused by handover behavior.
the scenario is as follows :
1- active set contains SC1 . after that SC2 is added to the active set .
2- after adding SC2 , UE_Tx_Power started to increase
3- now SC2 is better than SC1
3- the UE sent MR asking for deleting SC1, but after 14 sec from adding SC2 , the utran deletes SC2 (the best link) .
4- after deleting SC2 , UE_Tx_Power still high . Ec/No is very bad ==> drop happens

i checked RTWP for SC1 & SC2 :
SC1 -91
SC2 -86

but after the drop , a new call was established on SC2 (with a bigger distance from the site) with lower UE_Tx_Power .

can you help ???

[kentck86]

hi friends,

I need your help please .

i have a dropped call in PS drive test that caused by handover behavior.
the scenario is as follows :
1- active set contains SC1 . after that SC2 is added to the active set .
2- after adding SC2 , UE_Tx_Power started to increase
3- now SC2 is better than SC1
3- the UE sent MR asking for deleting SC1, but after 14 sec from adding SC2 , the utran deletes SC2 (the best link) .
4- after deleting SC2 , UE_Tx_Power still high . Ec/No is very bad ==> drop happens

i checked RTWP for SC1 & SC2 :
SC1 -91
SC2 -86

but after the drop , a new call was established on SC2 (with a bigger distance from the site) with lower UE_Tx_Power .

can you help ???

hi,

It could be drop due to userinactivity, kindly check if the RRC Connection release cause:userinactivity?

[agenov]

So far what is cleared that RNC didn't received the first 1B event (most probably due to bad UL because of higher power used by UE/ RTWP is higher during that time for some reason - possible reasons are high traffic, external issue, Hardware and etc./). Probably it is related to NodeB L1 communication lost i.e Sync. Failure. Do you have the cause value for this release? Any available trace or logs from the RNC side/Cell level KPIs could also be indicative and useful/ before event occurred?



BR
Alex


hi friends,

I need your help please .

i have a dropped call in PS drive test that caused by handover behavior.
the scenario is as follows :
1- active set contains SC1 . after that SC2 is added to the active set .
2- after adding SC2 , UE_Tx_Power started to increase
3- now SC2 is better than SC1
3- the UE sent MR asking for deleting SC1, but after 14 sec from adding SC2 , the utran deletes SC2 (the best link) .
4- after deleting SC2 , UE_Tx_Power still high . Ec/No is very bad ==> drop happens

i checked RTWP for SC1 & SC2 :
SC1 -91
SC2 -86

but after the drop , a new call was established on SC2 (with a bigger distance from the site) with lower UE_Tx_Power .

can you help ???

[zeezzoo]

@Kojaa
Thank you my friend . i think this is not my case because after removing the good radio link , i have a scrambling code (let's call it SC3) in the detected set that has very good Ec/No (-4 dB) and one Scrambling code in the active set with poor Ec/No (-24 dB) . then the drop happens . but those two cells should not be defined as neighbors because the real cause here is : deleting the Best Radio Link in the active set which by the way has SC3 as a neighbor .
do you have some documents where i can read about the case you talked about ?? (releasing serving RL if there was another RL in detected with 12 dB higher) . my equipment is huawei 6900 . I'll appreciate it .

[zeezzoo]

hi,

It could be drop due to userinactivity, kindly check if the RRC Connection release cause:userinactivity?

thanks my friend but it's not due to user inactivity I already checked it's related to radio .

[zeezzoo]

So far what is cleared that RNC didn't received the first 1B event (most probably due to bad UL because of higher power used by UE/ RTWP is higher during that time for some reason - possible reasons are high traffic, external issue, Hardware and etc./). Probably it is related to NodeB L1 communication lost i.e Sync. Failure. Do you have the cause value for this release? Any available trace or logs from the RNC side/Cell level KPIs could also be indicative and useful/ before event occurred?



BR
Alex


Thanks friend . unfortunately no trace was done for this DT . but i also think that high RTWP is the reason for this drop . but who is responsible of deleting SC1 from the active set ? is it RRM ?

[KoJaa]

I think you just described the one that I'm talking about, your SC3 is seen as detected set with a very good Ec/No of -4db while you have -24db as the best one? I think Adding the SC3 would solve your problem, if it is not intended to serve that location then that SC3 is overshooting creating problems on that area.

The one i'm talking about is with e// vendor I'm not sure if this also applies on huawei. Below is the description from ALEX.

"The number of dropped call events due to missing neighbors during the recording. A high number indicates that the cell has undefined neighbor cells that cause interference and dropped calls, and therefore should be defined as neighbors. A drop will occur if the missing neighbor is stronger than the active set + releaseConnOffset , so the statistics depends on the parameter value. "

the value of releaseconnoffset is 12db


@Kojaa
Thank you my friend . i think this is not my case because after removing the good radio link , i have a scrambling code (let's call it SC3) in the detected set that has very good Ec/No (-4 dB) and one Scrambling code in the active set with poor Ec/No (-24 dB) . then the drop happens . but those two cells should not be defined as neighbors because the real cause here is : deleting the Best Radio Link in the active set which by the way has SC3 as a neighbor .
do you have some documents where i can read about the case you talked about ?? (releasing serving RL if there was another RL in detected with 12 dB higher) . my equipment is huawei 6900 . I'll appreciate it .

[agenov]

When the NodeB looses sync. (UL) at layer 1 it will initiate RL release procedure toward the RNC. If you had LMT trace you may search for it or to check in Nastar and M2000 KPIs whether you have many drops with this reason.

BR
Alex


Thanks friend . unfortunately no trace was done for this DT . but i also think that high RTWP is the reason for this drop . but who is responsible of deleting SC1 from the active set ? is it RRM ?

[zeezzoo]

When the NodeB looses sync. (UL) at layer 1 it will initiate RL release procedure toward the RNC. If you had LMT trace you may search for it or to check in Nastar and M2000 KPIs whether you have many drops with this reason.

BR
Alex

but in my case i have ative set update that removed the best RL (SC1) instead of removing the bad RL (SC2) . does this apply also for losing Sync ??

[zeezzoo]

I think you just described the one that I'm talking about, your SC3 is seen as detected set with a very good Ec/No of -4db while you have -24db as the best one? I think Adding the SC3 would solve your problem, if it is not intended to serve that location then that SC3 is overshooting creating problems on that area.

The one i'm talking about is with e// vendor I'm not sure if this also applies on huawei. Below is the description from ALEX.

"The number of dropped call events due to missing neighbors during the recording. A high number indicates that the cell has undefined neighbor cells that cause interference and dropped calls, and therefore should be defined as neighbors. A drop will occur if the missing neighbor is stronger than the active set + releaseConnOffset , so the statistics depends on the parameter value. "

the value of releaseconnoffset is 12db

no there's no overshooting cells . but the scenario should be like this :
-SC1 in active set
-add SC2 to active set
-delete SC1
-add SC3 to active set ; where SC3 & SC2 are already defined as neighbors

but on the ground i have this :
-SC1 in active set
-add SC2 to active set
-delete SC2 (Ec/No -7 dB) from active set instead of removing SC1 (Ec/No -24 dB)
-now i can't add SC3 (Ec/No -4 dB) to active set because it's not a neighbor to SC1 . they shouldn't be defined as neighbors . the real problem is why the system removed SC2 .

[yudil]

Did you have checked the capacity or alarm of the SC2? Why SC3 shouldn't be define as a neighbor of SC1 even that interfered that area. Is it too far away?

[agenov]

doesn't matter whether the cell is the best or not. Also you don't know what UL conditions were no matter DL was good enough.My suggestion is to check statistics in M2000 and Nastar(CHR/CALL FAULT analyze) if you have or to repeat the test with LMT trace in parallel. Something else if SC3 is reported in this point on this levels and quality you should consider it as adding into neighbouring list or if you think it is overshooting to take relevant antenna design change actions.

BR
Alex


but in my case i have ative set update that removed the best RL (SC1) instead of removing the bad RL (SC2) . does this apply also for losing Sync ??

[cococrunch]

Did you see MR with event 1B in SC2? or is it SC1 in the MR?