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pix.
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4th August 2011 at 20:04 #66887
Sumair Azam
GuestHi all,
I am working on ALU equipment and i would like to know if having the value of BTS queue length as 8 instead of 6 or 10 which are the default values depending on number of trxs(6 for trx number > 2 and less than 5, 10 for trx number in cell > 4). What good can we achieve by tunning it to 8 in a low traffic network. What are the cons of using 8 instead of 6 for cell having 3 or 4 trxs).
Also if we put BTS_queue_Length as 8 for 2 trx cells instead of default value of 4 will it have any impact on CDR or any other significant KPI in a NOT congested cell. I can visualize the impact in case of a congested cell owing to impact on HOs(inc and out) and hence degrading CDR as a result but for low traffic not congested cell will it make any impact.
@ pix: i am counting on you heavily to help me out here ๐
6th August 2011 at 05:36 #66888pix
Guesthi sumair,
it is a good idea to increase this number. Here are some extra info:
1/ a MS which is requesting a TCH will get a TCH, if one is free.
2/ if no TCH is available, then the MS is put in the queue if there is less than BTS Q LENGTH ms already waiting in the queue. Else, the call is rejected.
3/ while MS is in the queue, the BSC will attempt to do directed retry (DR and FDR), will attempt Fast Traffic HO and wait for a TCH to get released in the serving cell. If any of those does happen, then the MS gets a TCH.
4/ If nothing happens after “T11” seconds, then the call is rejected.In other words : if the cell is not congested, then the queue is empty. It is useless.
The parameters bts q length and T11 are useless.Maximizing BTS Q LENGTH will not have any negative effect on subscribers, nor on QoS.
Increasing T11 : the subscribers will “stay” in the queue longer. So they might wonder what is happening. 10s is the limit… after that, they wonder what’s happening and hang up by themselves – > by the way, if they do that, then that’s not counted as congestion… ๐You will see some Qos indicators which show how “long” is the queue (hiow many MS in the queue), and what happens to MS in the queue : are they rejected, or do they find a TCH after all, etc.
Thos indicators are located under the family “Forced Directed Retry”, or “TCH Queuing”, I forgot. Just search for “queue / queuing” in the list of indicators…
Regards
pix7th August 2011 at 17:43 #66889Sumair Azam
GuestThanks a lot for your insightful analysis, its much clearer now, i already had an idea but just wanted to make sure ๐
P.S i would also like to cite an observation regarding increase in BTS queue length before Christmas and new year night , for congestion relief it helped but it impact the global indicator for CDR .
I believe the degradation was owing to less inc HO on congested cells which in turn when taken into the formula for glocal CDR degraded the KPI , a trial reversal for one BSC resulted in instant improvement on the that BSC wrt CDR.
Correct me if i am wrong here.
Thanks again
๐
8th August 2011 at 03:38 #66890pix
Guesthi,
it really depends on what is your formula for CDR. Did the actual number of call drops improved when you increased the queue length ?
I would expect to see an increase of SDCCH Drops, since the SDCCH is seized for a longer time (the MS in a queue is using a SDCCH channel during its whole queuing duration)
But an increase of CDR… that’s strange. The explanation about HO is not satisfying : whether there are 6 ppl in queue or 8 ppl in queue doesn’t change the fact that most cells are congested and cannot accept incoming HO.
(Handovers are not put in a queue, except for the external one (BSC to BSC) )Whcih type of BSC are you using ? G2 or Mx ?
regards
pix -
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