Error indication: T200 expired

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.

Assem,

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.

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?

Hi! Michele,

I do not understand why MSRFPCI should be provided by the BS.It should be provided by MS.

Regards,
NK

Thanks for your reply Michele/Pix
In siemens Vendor we have the default Value for T200
T200=29-31-38-90-70-29-168,
Parameter format: sdcchSAPI0 – facchTCHF – facchTCHH –
sacchTCHSAPI0 – sacchSDCCH – sdcchSAPI3 –
sacchTCHSAPI3.
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 reply

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 ?

Regards,
Pix

Hi Michele,

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 ?

Thanks,

Zbigniew