Sequence error

[plannerguy]

Hi all

I have a serious call drops in my network when anylsed found that issue is with "sequence error "
if any knows the same pls explain

Regards
Plannerguy

[plannerguy]

hi

experts please through your inputs.....i am barely in need of help...

i mean TCH drop.......


Regards
Plannerguy

[plannerguy]

Hi all

Same thing is seen during TEMS dive test as Data Link failure:Sequence error


Experts pls help


Regards
Plannerguy

[zhanglw268]

From the Spec. GSM 08.58 section 9.3.22, we know the sequence error is one of the reason for a release on the radio link layer. When BTS layer 2 received a Layer 2 message from MS, it verifies the received message to see whether the received frame number is valid, if the received frame number is greater than the last expected verified I-Frame number BUT NOT equal to the next expected verified I-Frame number. BTS Layer 2 will build a MDL_ERROR_INDICATION message with "sequence error" cause and send it. Meanwhile BTS Layer 1 can build a MDL_ERROR_INDICATION messge and send it as well. This is same at Mobile side.


The sequence error may be caused by the MS, the air interface(Um) and the BTS. From BTS side , it may be a software, firmware or hardware problem. From the experience, Network optimization can improve the system performance.

The reason is: If network plan is not very good, when Mobile reached to some extreme situation, such as the complex building group, the edge of the bad covered cell and radio interference. As the path loss, propagation delay, cause the frame bursts cannot be transmitted and received within the real time slots.i,e Cannot be synchronized. Maybe it will result the I Frame problem during the transmission and receive. when the MS handover to other cell, the problem also can disappear.

The problem is very likely to occur when you have interference from a co-channel MS on a cell with the same TSC (ie BCC not BSIC). Therefore simply changing the BSIC by selecting a unique NCC will not solve the problem - you need to ensure that the BCC (and therefore the TSC) changes. A consequence of this is that the BSIC plan should be designed to maximise the distance between co-BCC cells.

You have to clarify everything and narrow down the problem, and try to find out the problem pattern, and it is not easy to find out the problem, so it is very complex to investigate this issue, if you find it very often, it is suggested that you open a ticket with the Radio vendor to investigate further.

[plannerguy]

Hi

Thanks zhang

the explainatation given was excellent....

will have a look on same and will get back you withy results.


Regards
Plannerguy