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HI,
thanks pix but can u tell me from 3gpp where and how to check?
and if i want to check immediate assignmenet reject is enable or disable then how to check it?
Hi,
imm ass reject is a BSC parameter in Alcatel.
BR,In case your RACH is low, can you please share if the cell has got Excessive TA drops? Is MAXTA reduced on this cell? Because one reason for RACH failure is due to the detection of excessive timing advance in a RACH access burst which will be rejected and counted as failure.
Also, when checking for BCCH/BSIC combinations, make sure you are concentrating on the BCC Part of the BSIC. because it might be that two co-BCC / BCCH cells are located in near vicinity creating high RACH failures.
hi pix,
How to check from 3gpp? Can u send some link?
And if imme assignment will enable then after first rach request bts will send imme assign reject due to lack of sd? Is it right?or some other reason?
Then in this case how it will improve rach sucess?because here i am not getting rach ?
http://www.google.com/search?q=3GPP
the reject message contains a timer, the MS reads this timer and will wait “T” before a new attempt.
the reject allows to spread the retransmission of channel requests, rather than let the MS send consecutive Channel Requests.
It increases the probability to get a SDCCH (congestion occurs in micro peak)Hi pix,
here i want to ask after my first rach request if there is no sdcch then imme assign reject messege wil be send by bts and only in this case we can control sd congestion? ok is it right?
but here it wil be considered as rach failure so how it improve rach sucess ratio?
Jrish,
There should not be so many RACH failure… if they are too high, then there is probably something wrong somewhere in your settings.
What is the failure rate, exactly ?
Hi pix,
i want to say and ask only this things
for improving my rach success ratio (1) if tx will increase from 20 to 50 ok? will help me?
(2) max retrans form 4 to 2 will help me?
(3) if imme assign reject enable then how it will help or not?
and for sd congestion
if i enable imme assign reject then it will help me to reduce sd congestion? is it right?
1/ Yes, it COULD. Try it to measure the impact.
2/ Yes, the indicator should look a little better.
3/ I don’t know how is computed the RACH success rate, so I don’t know if this feature could help regarding this specific indicator
4/ Yes. How ? By slowing down the repetition of the Channel Request, hence giving a higher probability that at the second or third attempt, the SDCCH channel is free.Hi pix,
thanks .so by enabling immediate assignment reject we can improve the sd congestion but buddy still not clear if my max retransmission is 4 then after 1 rach if there is no sdcch available then bts will send immediate assign reject and by this way we can reduce sd congestion because here it is not countes as sd assignment failure is it ok?
but from ms side my first rach is fail after receiving the messege immediate assignment reject from bts side then it will be counted as rach failure?
Krish,
The BTS sends Immediate Assign Reject when the Channel Request cannot be followed by a SDCCH allocation. (so far, we agree)
In this message, the BTS tells the MS to re-send a 2nd Channel Request only after xxx seconds (timers names are WI_OC, WI_EC, WI_xx)
From MS point of view : instead of sending the 2nd Ch. Req immmediately, it will wait accordingly to the WI_xx timer.
The 2nd Ch. Req has more chance to be succesful because after WI_xx seconds, one SDCCH is perhaps available. Indeed, the SDCCH usage is kind of bursty, and waiting xxx seconds is better than re-attempting immediately.
It is up to you to interpret this mechanism, and its impact on the indicators. I don’t know your RACH failure formula…
Hi pix,
as per our discussion if i enable immediate assignment reject then it will help me to reduce sd congestion. is it right?
i agree but in this case we can save the sd congestion but here it will consider has rach is not sucessful ?
and u are telling abt timer then in normal case (i ean without enabling immediate assignment reject) ms will wait according to that timer and after that it will send second rach. is it right?
Krish,
i feel like I am repeating the same thing over and over….
If you disable the Reject, then the MS will repeat the Channel Request almost immediately.
The goal of the Reject is to force the MS to wait a little before resending the Channel Request.About your KPIs, I will not answer anymore. Read below 🙂
hi pix,
ok thanks
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