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We are using SIEMENS EQUIPMENTS with BR9. Recently we have upgrade our software from BR7 to BR9. After upgrading we are facing problem with micro BTS BS82II. The site is connected via SATELLITE. When link is down and after it comes up then the site will work for couple of minutes but after then only signalling is there but no traffic. Immediate assignment is very low. We check the statistics and found like there are lots of SDCCH drops due to T_MSRFPCI expiry. Could anybody give some solution regarding this. Thanks in advance.
Hi ajay!
could you specify the problem. Since as i know immediate assignment is phase to allocate SDCCH channel and in this phase there is no SDCCH drop since SDCCH hasn’t been allocated. SDCCH drop is happen in case SDCCH has been occupied.rgd//uzn
UZN,
beware : the definition of a “sdcch drop” changes depending on the vendor. What Siemens call a SDCCH Drop might be considered as a SDCCH assignment failure in alcatel… you never know.
hi pix,
thanks for your information. This is really a new for me, since i have worked in 2 vendors and both give the same definition of immediate assignment.Hello UZN,
I remember a thread in this forum where we noticed such a confusion between 2 vendors, sdcch drop vs. sdcch assignment unsuccess. But maybe i don’t remember correctly. Other times (many many times), it’s the optimizer himself that makes the confusion 🙂
With which vendor have you worked with ?
i have been working in E///, last year i joined to NSN for 2 years.
thx
Yes immediate assignment is phase to allocate SDCCH channel but when MS request for channel to BTS then BTS will send message CHNRD(Channel Required) to BSC and then BSC send message CHNAV(channel activation SDCCH) to BTS. Here BSC will increment counter for attempted SDCCH and IMMEDIATE ASSIGNMENT as well.When BTS receive CHNAV message from BSC then it sends CHNAK message to BSC and T_MSRFPCI counter is started. Now BSC will assign immediate assignment message to BTS. If BTS does not receive immediate assignment message time between T_MSRFPCI then the call gets dropped. This means that SDCCH and IMMEDIATE ASSIGNMENT will be dropped. This means that yes there is SDCCH drop during immediate assignment. Please correct me if I am wrong.
We got the solution. Actually what happened was that, When we migrate to BR9 then there was bug in software. T200 timer handling capability was only 500msec but actually we were having 620 msec delay in abis.ajay,
then yes, with all due respect, your description is not correct : there is no dedicated connection yet, Immediate assignment is still considered as part of the sdcch assignment phase. Therefore the problem you are describing is a sdcch assignment failure and not a sdcch drop 🙂
Glad you found your problem 🙂
Thanks Pix for correcting me. So in our case we are having two different cases.
First case is Immediate Assignment Failure Rate which is because of BTS not receiving CHNAV message from BSC or BSC not receiving CHNAK message from BTS as I have said previously which is SDCCH assignment failure.
Second case is SDCCH drop due to T_MSRFPCI which is the case after Successful Immediate Assignment.
Thank you once again.What is the possible cause of SDCCH Drop due to Abis Failure
huh… Abis failure 😉
what is the cause of traffic abnormal release ? can anybody explain plz. ?
mamun,
call drop!
due to..poor coverage
high interference
faulty hardware (in BTS, Abis, BSC, Ater or TC)
failure during handoverwould you plz tell me any one why SDCCH is drop?
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