- This topic has 52 replies, 1 voice, and was last updated 11 years, 6 months ago by homa.
9th June 2009 at 11:43 #51948PixGuest
This failure is VERY strange, it’s very difficult to identify the problem.
Does it happen on all cells of the BSC? Or only on cells with external neighbours ? (from other BSC)
Try to reduce the size of TCH queues (T11 less than 6 seconds, BTS Q LENGTH less than 5), try to disable Forced Directed Retry (EN FDR = Disable), try to disable Fast Traffic HO (En_Fast_Traffic_HO = disable), try to forbid external directed retry (EN_EXT_DR = disable). Attempt those actions only one by one. Don’t rush 🙂 The External Directed Retry and Queuing could generate BSS errors if it is not understood by MSC correctly.
If you still have failures, then it’s perhaps a discrepancy between NSS and BSS. Check that your NSS have the latest patches… (that happened to me… NSS update fixed the problem)
Also, check BSC Radio parameters are in line with MSC configuration. For example, below, there are some parameters set in BSC that must be checked by MSC team, so that both sides are using the same timers, same messages, etc.
T(iar) & T(ias)
T11 & T11_FORCED (T11 forced Must be < assignment timer in the MSC (trr1)) T9110 etc...17th September 2009 at 07:03 #51949msmGuest
what are the major causes of tch assignment failures in GSM8th December 2010 at 18:51 #51950homaGuest
how to find feeder swap in drive test10th December 2010 at 00:58 #51951El mariachiGuest
There r 2 kinds of swapped feeders or sectors u may detect when making a drive test.
1- cross sectors, feeders (TX, RX) of sector 1 are used for sector 2 and Vice versa.
U detect this when u r in the coverage area of S1 but u find you are served by the frequencies of sector 2 and when u need to make a HO to the other sector, it occurrs in an opposite way.
2- cross feeders, feeders(TX,RX) are connected in the place of each other in a certain antenna.
There will be no coverage transmitted by this sector.
When u make a DT. U will find that sector is not serving.
U may suspect the sector us down or crossed sectors.10th December 2010 at 16:25 #51952homaGuest
how we can reduce call drop11th December 2010 at 15:54 #51953El mariachiGuest
To reduce the call drop resulted by the swapped feeders, just reconnect the feeders in a correct way.
You may go after the feeders starting from the BTS to the antennas to ensure correctly connection.21st December 2010 at 16:49 #51954homaGuest
CDR Sequence error in seimens vendor24th December 2010 at 14:19 #51955homaGuest
what is tch assignment failur