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I am currently investigating a problem were calls on GSM are dropped with cause reason “recovery on timer expiry”. An initial investigation of the core network timer shows no evident problems with the timer settings however i from K15 traces of the A interface, i noticed that in most cases, the call drop occurs when NO connect ACK is recived from the MS. The call is connected normally however after some time, it drops with reason “recovery on timer expiry”. It seems that a timer is started when the msc sends the CONNECT message and it is stopped when CONNECT ACK is received. If no CONNECT ACK is received before expiry of this timer, the call is released. Did anyone see this type of behaviour before? Why is the connect ACK not being sent by MS (possible poor radio conditions?) Any help on this would be greatly apreciated. Network here is Siemens BR9.0
“i am currently investigating a problem were calls on GSM are dropped with cause reason “recovery on timer expiry”. An initial investigation of the core network timer shows no evident problems with the timer settings however i from K15 traces of the A interface, i noticed that in most cases, the call drop occurs when NO connect ACK is recived from the MS. The call is connected normally however after some time, it drops with reason “recovery on timer expiry”. It seems that a timer is started when the msc sends the CONNECT message and it is stopped when CONNECT ACK is received. If no CONNECT ACK is received before expiry of this timer, the call is released. Did anyone see this type of behaviour before? Why is the connect ACK not being sent by MS (possible poor radio conditions?) Any help on this would be greatly apreciated. Network here is Siemens BR9.0″
I have the same problem , but im my case I see that the ms send connect ack but I don’t know if the MSC receive this messagei have the same problem with a Ericsson network. Did you solve this?
Hi,
Have you guys tried having a trace on the Test cell phone at the MSC end and running them in parallel to trace weather the message is lost on the way or MSC receives the messages from MS or not.
Work with NSS assistance should be fruitful.It is T313 timer which MSC start after sending the Connect and wait connect ack. If T313 expire before ack then MSC will release the call.
Dears,
we’ve faced exactly the same problem. call setup –> dedicated mode –> call drop –> disconnect and the call continue in dedicated mode then idle mode.
cause reason of drop call is “recovery on timer expiry” which is due to the expiry of T313.
Any suggestions to solve such issue?
Two scenarios are possible,
1. A Faulty handset.
2. RF UL Quality issues causing no reception at the MSC Level.
Probably you should check if the issue is being generated from one IMEI or IMEIs of same vendor if its a faulty handset or a chinees company’s phone then its best to contact the customer and ask him to change his handset. Else you can improce the RF Quality of try increasing the T313 timmer.Hello All,
Could you help me to answer below questions.
T313 = 30sAn application parameter determines the time supervision period between sending of CONNECT message and receiving of CONNECT ACKNOWLEDGE message using the T313 timer. Value range = 1s-255s
We need to check on the following: – Is there any another timer on the BSC/RNC that is linked to this timer? – In MIC1 network, the timer is set to default (30s), what are the risks of decreasing / increasing this timer? – What could be the advantages of changing this timer value? – what are the possible impact on the call flow? (Delay on call connection….) – What is the particular impact of this timer during an IRAT handover from 3G to 2G? Does this timer has any impact on call drops? – Does the expiry of this timer impactCause i = 0x80E6 – Recovery on timer expiry
MSRN is getting from HLR, but call is not terminating as network busy showing in mobile.
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