[Gerald Thomas]

i have a site with low traffic during busy hour but we are having SDCCH congestion from our KPIs. we had changed TRXs, checked for swap feeders and BSC configuration but the problem is still the same.
our TA=63 for all sectors and for all the sites.
please can anyone help me, i don’t what to do now.

[Bijoy Banerjee]

Hi Gerald
What is the formula for SDCCH Blocking u r using

[Gerald Thomas]

hi Bijoy,

Accessibility to SDCCH = (Number of Successful SDCCH Assignment)/(Total Number of SDCCH Attempts)

[Bijoy]

Hi Gerald.
Tell me when is ur Successful SDCCH Asssignment pegged?
Is it after Immediate Assignment command sent or after the Establish Indication sent from BTS to BSC?

[Gerald Thomas]

hi Bijoy,

There is SDCCH Assignment Successful and SDCCH Allocation Successful. Assignment Successful is after Immediate Assignment and Allocation Successful is after Establishment Indication sent from BTS to BSC.

[Bijoy]

Ok Gerald.I could have given u the exact solution,but for that i would require some more inputs,So U can Try any of these or all of these solutions one by one
1.U can Try to reduce the RACH Min. Access Threshold & RACH Busy Threshold to overcome this problem.
2.Please check if There is More LOC Update request in that cell.If there is many LOC update,u can increase the SDCCH.
3.Try remove additional SDCCH’s if any and try to put Only One SDCCH/TRX.
4.Make the BCCH TRX Lapd of 32kbps.
5.Check for Co-BSIC-BCCH,if any nearby.
7.Also check if there is Channel Activation Nack for this cell.

[Pix]

Gerald,

few more things:
what are the values of those KPIs (failure rate and number of requests, attempts and success ?)

what is your brand of equipment ?

cheers,
pix

[KRISH]

hI BIJOY,

IF I HAVE SD BLOCKING 2% AND IF I INCREASE THE LAPD FROM 16 TO 32 THEN IS IT REDUCE MY SD BLOCKING?

IF I HAVE SD BLOCKING DUE TO LAC UPDATE THEN I THINK NO MEANING TO REDUCE MAX RETRANSMISSION IS IT OK?

AND CAN U EXPLAIN THISAlso check if there is Channel Activation Nack for this cell.?

[Bijoy]

Hi Krish
Only if u have high Half rate traffic,changing Lapd to 32 kbps for BCCH TRX will help.
Yes,for loc,it will not help much.Also ur immediate assignment will affect
for “Channel Activation Nack”,may i know which system r u using?

[krish]

Hi bijoy,

i want to know not only bcch trx but if i will change my non hopping trx(tch trx) signalling from 16 to 64 then will it help to reduce sd blocking because my max sdcch are on tch trx?

[Bijoy]

Hi Krish
This will help only if u have high HR Traffic volume in that cell.
Also,I think there will be a limit on how many SDCCH’s can be defined on a particular TRX

[Gerald Thomas]

hi Pix,

SDCCH failure rate is in percentage

SDCCH attempts and success are figures

Our equipment brand is ZTE

[krish]

Hi bijoy,

i am not getting why u are relating half rate traffic to sdcch blocking and 64 signalling if any valid reason plz explain me?

and here i am taking example.

in our system we can define 4 sdcch per trx now suppose if i have (1) 4 trx in one cell

(2)and 16 sdcch in that cell which is max and still there is 5% sd blocking and signalling is 32k

(3)so now in this case if i will increase lapd signalling from 16 to 32 then will i get improvement in sd blocking?

plz let me know….because i want to try it and if anybody has tried it plz share………

[Bijoy]

Hi Krish
Let me explain
High HR traffic puts a high load on SDCCH Traffic bcoz it is through this SDCCH all the signalling takes place. Also as u know more HR increases the system GOS,the signalling GOS also increases.

As per your example,first put only the required no. of SDCCH which can be calculated from the MAx. SDCCH Traffic with desired GOS(i’e 0.5%) and remove all unnecessary SDCCH.It is not an intelligent practice to go on increasing the SDCCH’s in a cell to reduce SDCCH Blocking .U can also implement dynamic configurations of SDCCH

Better check the reasons for such high SDCCH Usage.If it is due to LOC update,changing Lapd from 10K to 32K will not help.

Hope u understand the point

[krish]

Hi bijoy,

i think still u are not getting my point here in this case i have max sdcch and alrady we have enabled dynamic sdcch allocation.

So point is that here my sd blocking is due to lac update so will lapd from 32 to 64 will help me for reducing sd blocking?hope now u get the point.

[Author]

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