Call Blocked : Reason "No Circuit/Channel available"

[vasili_koslov]

Hello experts,

We have a case in drive test result and OSS KPIs. There are many blocked calls and reason looks "No Circuit/Channel available" in layer3 message. At first we thought congestion exist and I checked it. But there is no congestion during test time. Then we sent a drive tester team for verification. Drive tester could not do call sometimes in area. It is not related only one cell. we have same problem in all cluster. We think It is related Core network.

Do you have any idea? what is the problem?

[vasili_koslov]

No idea from anyone?

[gerchase]

Have you check the Access Control parameters?

[dext]

Check the congestion KPI , all kind of congestion. The message appears due to blocking cause your mobiles can access the network, also if this is particular to one cell you might want to check Any Alarms on the site. also check the RF condition when such issue appears.
can you do end to end tracing from LMT for this issue. it will get better understanding.

[vasili_koslov]

No. not only one site. I mean all region. Also RF conditions very good when issue appears. Already checked all congestion KPIs. There is no congestion.


Check the congestion KPI , all kind of congestion. The message appears due to blocking cause your mobiles can access the network, also if this is particular to one cell you might want to check Any Alarms on the site. also check the RF condition when such issue appears.
can you do end to end tracing from LMT for this issue. it will get better understanding.

[vasili_koslov]

Give detail please for relation between access control parameters and my issue.


Have you check the Access Control parameters?

[samuraial]

Well there could be a couple of things affecting your call:

1-) check E1 connection or transmission counters if there are drops or problems
2-) check the rate the call drop occurred and see if it is due to one AMR rate
3-) check Core network in order to do cs trace and they can see the root cause if it is from their side.
4-) License issue
5-) UGW/MSC configuration issues

It could be a wrong/missing configuration or could be a bottleneck usually due to core insufficient resources.
From your side you could do a CDT trace, Uu interface trace, IU CS trace and core from the other side a CS trace.

On RNC as I suppose this is 3G you can check the counters of IUCS and IUPS if not wrong to see for congestion if any.
Also was this new site/s added recently? any expansion in the network?

B/R

[electron]

No. not only one site. I mean all region. Also RF conditions very good when issue appears. Already checked all congestion KPIs. There is no congestion.

Hi Vasili,

one thing ; do you have LTE and you are trying to have CSFB to WCDMA or GSM and this is happening? such thing cab be observed in multi technology scenario please confirm at first then will give you some hint what to check.


Cheers

[vasili_koslov]

Not exist LTE. call started WCDMA and call blocked occurs in 3G.


Hi Vasili,

one thing ; do you have LTE and you are trying to have CSFB to WCDMA or GSM and this is happening? such thing cab be observed in multi technology scenario please confirm at first then will give you some hint what to check.


Cheers

[samuraial]

You need to give more answer to my questions my friend.
Was this a network expansion: gsm to umts site upgrade, new RNC expansion etc.?
Did your DT engineer check the AMR rate of call failures!?
Did you see the security mode counters if they have an increase or not!?
A CDT RNC trace would be nice together with a CN cs trace. For Huawei I can help in analyzing them, others don't have the tools.
Did you ask your core guys to check the configuration?(to avoid err on their side?)

Also to avoid access parameters and such please compare parameters with CME(cell based, NodeB base).


B/R

[ulhwbest]

Hello,

Have you also checked the OSS KPI during the time of Drive Test?
Check the RRC Setup Success Rate, RRC failure reasons, RAB Setup Success Rate and it's RAB failure reasons

Regards