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18th February 2008 at 07:01 #51035KassemGuest
Thanks in advace for your reply
coud you please help me what the reasons for TCH Drop due to “Error indication: T200 expired”
Kassem18th February 2008 at 08:18 #51036MicheleGuest
T200 is an air interface timer regulating the communication between MS and BTS. It defines the rate of repetition of a message (on BTS side) on the air if it is not acknowledged by MS.
If the message was repeated N200 times and no answer was received by MS, an error indication with cause T200 expired is provided to BSC.
Probably there is not a correct setting of T200 or N200 or the DL quality/level is very bad. Another problem could be the use of the same BSIC between adjacent cell, causing some problem during handovers.19th February 2008 at 05:43 #51037KassemGuest
Thanks alot for your reply Michele
coud you please help me what the reasons for TCH Drop due to “Connection failure: radio link failure”
Thanks alot kassem19th February 2008 at 05:51 #51038PixGuest
you should ask all your questions at once 🙂
radio link failure : the radio link counter has expired. It means that during few consecutive seconds (def. 9s), there was no SACCH UL that was succesfully decoded by the BTS.
It is an indication of the TCH quality : if the SACCH could not be decoded, then the TCH probably can’t be decoded either.19th February 2008 at 06:00 #51039KassemGuest
Thanks alot Pix for your fast reply
Pix ,could you help me also for these
please I have some questions:
What the reasons for TCH drop due to these Counters:
1-Error indication: unsolicited DM response, multiple frame established state
2 Error indication: sequence error
3 Connection failure: T_MSRFPCI expired
4 Connection failure: distance limit exceeded
5 Connection failure: handover access failure
6 Connection failure: radio link failure
7 Connection failure: remote transcoder failure19th February 2008 at 07:55 #51040MicheleGuest
3 T_MSRFPCI expired: on the new channel no ms rf power capability indication were received in BTS (from BSC) within 20 sec fron Channel Activation. In this case probably MS was never presented on the new channel (no SABM was received in BTS);
5 handover access failure: T3105 expires ny1 times and MS never accessed on the target cell;
4 distance limit exceeded: the distance between MS and BTS exceed the maximum allowed one into the cell (attribute excessiveDistance) and so the call is released;
7 remote transcoder failure: no DL TRAU frames were received in DL direction after channel activation (for the timer TTRAU).
Do you work with SIEMENS BSS?20th February 2008 at 05:50 #51041KassemGuest
Yes , I am working in Siemens network.and I Faced all above Problems
your cooperation high appreciated
Thanks alot21st February 2008 at 07:22 #51042NKGuest
I do not understand why MSRFPCI should be provided by the BS.It should be provided by MS.
NK21st February 2008 at 07:33 #51043MicheleGuest
Hi Kassem, as you know in Siemens BSS Handover and Power Control algorithm are implemented in BTS instead of in BSC. So MS capabilities sent from MS to BSC (transparent to BTS) are then forwarded from BSC to BTS by an Abis message (RF MS Power Capability Indication).
If BTS doesn’t receive this message (from BSC) in a time of 20 sec from Channel Activation a Connection failure with cause T_MSRFPCI expired is generated.24th February 2008 at 05:42 #51044KassemGuest
Thanks for your reply Michele/Pix
In siemens Vendor we have the default Value for T200
Parameter format: sdcchSAPI0 – facchTCHF – facchTCHH –
sacchTCHSAPI0 – sacchSDCCH – sdcchSAPI3 –
if we face TCH Drop due to T200 Expired,we change in default value,lead to improvement
please advice us about it
Thanks in advace for your reply27th February 2008 at 13:13 #51045KassemGuest
please help me about last question27th February 2008 at 14:21 #51046pixGuest
T200 is directly proportional to the delay expected on the ABIS link :
with terrestrial Abis, this value shall be 300ms
with satellite Abis, it shall be incremented to 1000ms (1 second)
thererfore, you can try to increase this timer until the T200 stops expiring. Basically, you should look for the root problem : what is causing such high delays on the Abis interface ? Is your link stable ? Are your LapD stable ? What about the boards that take care of LapD at BTS side (SUM or TRX) and at BSC side (TSU or TCU) ?
Is there any congestion/overload on these boards ?
Pix28th February 2008 at 08:45 #51047MicheleGuest
the problem found by Kassem is on air interface (LAPDm).
Which is the release SW on field? BR9.0? It seems that there are some MS types having some problem with low T200 values.
I can suggest you some settings used on field by an Italian network operator. It doesn’t claim any problem and has a very very low tassfail.
NY1=7028th February 2008 at 10:20 #51048ZbigniewGuest
do you have some information about the TCH drop reasons
2 Error Indication: Unsolicited DM Response, Multi Frame Established State
3 Error Indication: Sequence Error
in Siemens BSS ?
Zbigniew28th February 2008 at 10:48 #51049pixGuest
thanks for your inputs.. maybe you can explain a little bit :
T200 supervises Ack on the LapD, so ok, it is impacted by internal MS delay as well.
Basically, how can you ensure the problem is in the Air interface ? It’s based on experience I guess ?