High PS Call Drop

[khaledkhoudi]

Hello experts,

I need your advice about PS call drop.

In our network, two RNCs have a high PS call drop.
When i check the KPI it's due to RF. so i checked the PCHR and i found the cause of these call drop is RTWP.

The cells which affected the most our RNCs already have a congestion in the HS user so i that's why the RTWP is high in these cells and that's what causes the call drop.
My questions to you are:

1- Do you confirm this analysis ?
2-How can we solve the HS user congestion without expansion (I mean increase the license or add the second carrier)

Vendor is Huawei

I am waiting for your feedback

Thanks.

[tthach830]

You said the cells are having congestions so maybe the drops are due to congestion.

I would suggest checking admission KPI and also your RTWP. If your RTWP is high that means you're losing capacity due to high noise. Also check your RNC utlization/loading to make sure he has enough capcity to handle data.

[yafawi79]

Boss. If you have high congestion caused by hs users you can reduce max number of hs-pdsch codes from 15 to 5 for example. While keeping min codes number equal to 1. Also number of hs-scch can be tuned from 2 to 3 or 4. This means that every 2ms 3 or 4 users will be shualed which will affect the dl throughput.

[khaledkhoudi]

I already check the RTWP and it's high. so you confirm my analysis?

[khaledkhoudi]

Boss. If you have high congestion caused by hs users you can reduce max number of hs-pdsch codes from 15 to 5 for example. While keeping min codes number equal to 1. Also number of hs-scch can be tuned from 2 to 3 or 4. This means that every 2ms 3 or 4 users will be shualed which will affect the dl throughput.

If i decrease the codes the user experience will be bad (the user throughput will be lower). Do you have other suggestion ?

[agenov]

Can you please share PCHR tool you use for this analyze, does it support R12 and later?
Before make any conclusions check all KPIs related with the drop. No one here can confirmed anything just like this especially with so brief info provided, you need to do deep investigation i.e imsi trace if needed, drive test, check more of the KPIs for RAB release, possible mobility issue and etc. The reasons for such behaviour could be too many, of course could be your explanation as well. Regarding your second question you need to relief the HSDPA traffic i.e to offload the cell by changing HO, cell reselection parameters, antenna design change if possible,cpich power change, you may also use different load algorithms and etc etc etc.

BR
Alex

Hello experts,

I need your advice about PS call drop.

In our network, two RNCs have a high PS call drop.
When i check the KPI it's due to RF. so i checked the PCHR and i found the cause of these call drop is RTWP.

The cells which affected the most our RNCs already have a congestion in the HS user so i that's why the RTWP is high in these cells and that's what causes the call drop.
My questions to you are:

1- Do you confirm this analysis ?
2-How can we solve the HS user congestion without expansion (I mean increase the license or add the second carrier)

Vendor is Huawei

I am waiting for your feedback

Thanks.

[BryxKeisha]

Hi Mate,

Check first in your PCHR tool about the propagation delay. I'm experiencing also the same here but I found some cells that overshoot. These overshooting cells serve UEs that are quite far from them, thus adding to its traffic and load and causing congestion plus high RTWP. Secondly, you can modify some parameter like UCELLCAC (Call Admission) and UCELLLDR (Load Reshuffling). You just have to modify the necessary actions to be taken there. Hope this helps.

[shahinsha]

Hi

Is 3GDT Feature is On in RNC.. Are there any simultaneous PDP Context Failures in SGSN??

[khaledkhoudi]

Hi Mate,

Check first in your PCHR tool about the propagation delay. I'm experiencing also the same here but I found some cells that overshoot. These overshooting cells serve UEs that are quite far from them, thus adding to its traffic and load and causing congestion plus high RTWP. Secondly, you can modify some parameter like UCELLCAC (Call Admission) and UCELLLDR (Load Reshuffling). You just have to modify the necessary actions to be taken there. Hope this helps.

Hi Keisha,

Which parameters to modify in UCELLCAC and UCELLLDR to reduce the congestion?
Waiting your feedback

[khaledkhoudi]

Can you please share PCHR tool you use for this analyze, does it support R12 and later?
Before make any conclusions check all KPIs related with the drop. No one here can confirmed anything just like this especially with so brief info provided, you need to do deep investigation i.e imsi trace if needed, drive test, check more of the KPIs for RAB release, possible mobility issue and etc. The reasons for such behaviour could be too many, of course could be your explanation as well. Regarding your second question you need to relief the HSDPA traffic i.e to offload the cell by changing HO, cell reselection parameters, antenna design change if possible,cpich power change, you may also use different load algorithms and etc etc etc.

BR
Alex

Hi Alex,

Thanks for your constant help

But i still need you help on this problem. The PS call drop is high 4% in the busy hour
When i check the KPI these two counters are the major reasons for the drops : PS RABs Abnormally Released Due to RF for Cell and PS RABs Abnormally Released Due to GTPU Failure for Cell.
From the PCHR, these counters contribute the most:

DropCall_DueTo_RB_RECFG(DCCC)_TimeOut

DropCall_DueTo_Ul_Radiolink_Failure

IURelated

DropCall_DueTo_TRBRst

I am counting on your help.
By the way the tool i am using to read the PCHR files is NPMaster (Huawei) and yes it supports RAN12 and 13.

BR,