- This topic has 43 replies, 1 voice, and was last updated 12 years ago by krish.
24th September 2009 at 06:33 #58669BijoyGuest
Reducing Max no. of Retransmission will reduce SDCCH Holding time for sure.If your site is having a very high SDCCH Blocking ,reducing it will definitely improve your SDCCH Blocking.
Rach Success ratio=immediate asssignment commands/RACH requests.
Poor RACH suceess may be due to poor radio environment,like CO-BCCH-BSIC in nearby sites,Phantom RACH(especially in very low traffic sites),BTS sensitivity,No SDCCH.you can also increase the RACH min. access level(def. -105) to improve RSR.24th September 2009 at 08:22 #58670RexGuest
which value(%) is acceptable for Rach success ratio?
Thanks.24th September 2009 at 08:38 #58671RGGuest
As per my understanding:
MaxRetrans relates to RACH retry for different Access Cause.
As our OMCR server only pegs/trigger (increment)the counters on the basis of Abis messages or Ater messages. So, in real we cant calculate our RACH Success Ratio. That is one of the reason “RACH Success Rate” is calculated using the response from the BTS with message “Channel Act Ack” for “Channel Act” send by the BSC. “Immediate Assignment Reject” directly relates to the Hadware fault as this transparent message is send after recieving the “Channel Required” from BTS and when in the BSC allocation table required resource is not present.24th September 2009 at 12:54 #58672krishGuest
K bijoy right.but can u help me to find out parameter rach access threshold para in eric?24th September 2009 at 13:01 #58673RexGuest
what is importance of enabling Immediate assignment reject in BSC, what’s its role?
Thanks,25th September 2009 at 11:59 #58674RGGuest
Immediate Assignment Reject is the default signalling RR message from BSC in respond to channel request when requierd resource is not available in the BSC allocation table.14th October 2009 at 17:29 #58675KRISHGuest
once again abt rach max retran .
if i have its value 4 andi have high sd blocking due to high traffic then in this case by decreasing it 2 ,as per said by u it will decrease sd blocking
but can u tell me if on my first rach bts will not allocate sdcch then ms will try second time so here actually sd is not assign form bts side so how it will reduce sd blocking?
and whatever i said above is it beneficial to inprove rach success?15th October 2009 at 03:28 #58676pixGuest
SD blocking is when the BSC is not able to allocate a SDCCH channel to the MS. In other words, it is when the BSC doesn’t send an “immediate assignment” message back to the MS.
Since the MS sends the RACH twice only, instead of three times, then there are only 2 blocking counted, instead of 3.
The best feature to reduce congestion is to use the Immediate Assignment Reject, and set the WI_OC to > 2s.
Pix15th October 2009 at 16:36 #58677krishGuest
thanks for reply. but i want to know if ms sends 2 time rach request and no response from bts side then in picture where sd comes because bts is not giving sd and because of that ms sends 3 ,4 time rach request.so it how to increase sd blocking……
and second if i have poor rach success ratio and my bcch-bsic and hardware is ok then by increasing rach max retrans from 2 to 7 and tx integer from 10 to 50 will help to improve rach success ratio.. plz explain..16th October 2009 at 20:46 #58678PixGuest
When 1 RACH is not answered by BTS, it is internally counted by the BSC as “1 SD blocking”.
So … 3 RACH from one MS, not answered = 3 SD blocking.
pix23rd October 2009 at 10:29 #58679krishGuest
Hi Thanks pix,
and second if i have poor rach success ratio and my bcch-bsic and hardware is ok then by increasing rach max retrans from 2 to 7 and tx integer from 10 to 50 will help to improve rach success ratio.. plz explain..24th October 2009 at 16:28 #58680krishGuest
hi bijoy & krish,
Can u help me for improving rach suceess?24th October 2009 at 17:10 #58681PixGuest
RACH success will be improved by proper TX INTEGER tuning (50) and activation of the IMMEDIATE ASSIGNMENT REJECT message.
The number of retrans is, IMO, useless, but you can give it a shot anyway !
Pix25th October 2009 at 14:25 #58682krishGuest
Hey as per said by u if i will change the value of tx from 10 to 50 will help me in imroving rach sucess and whats the importance of parameter S with this tx ?
And if i activate the imme assign reject
then it will help me in imroving rach sucess ratio? And also sd blocking?26th October 2009 at 18:56 #58683PixGuest
For S and TX INT yes, they work in couple.
Look at 3GPP to find the exact formula… but otherwise you can simply use the default value of TX INT = 50 with S = …? (isn’t it written somewhere in your docs ? i can check tomorrow for the S value, i forgot 🙂 )
For IMM Asg Reject : yes, it will reduce sd congestio and racch failure etc… Why didn’t you enable it already ? we gave you all details about this feature in past posts…