- This topic has 14 replies, 1 voice, and was last updated 8 years, 7 months ago by pix.
19th December 2008 at 16:21 #55082ATTOGuest
I have one cell which in my network which face high SD Mean holding time = 10 seconds ; she’s a boundary cell. I don’t know what to do to overcome congestion: i can’t reduce coverage because of one network ; i define 3 SDCCH but it is not necessary even when traffic is about 8 Erlang ( erlang B : 24 SDCCH/4 ; blocking rate = 0,5% -> traffic = 14,20);
Help please!!!!20th December 2008 at 17:52 #55083PixGuest
Mean holding time and congestion are two different things.
What is the SDCCH congestion at busy hour, for this cell ?
what is the SDCCH Erlang at busy hour ? (8 erlangs?)
If there is no congestion, then don’t worry about the mean holding time : it just means the MS’s are taking a long time to complete the location update procedure. It’s probably because of a slow response from core network (MSC, HLR, AuC, EIR ?)
If there is congestion, then it’s not normal : 8 erl. of traffic / 14.2 of capacity. Check that all your SDCCH timeslots are working and available, check SDCCH erlang and mean holding time per TRX (assuming each SDCCH is located on a different TRX)22nd December 2008 at 10:42 #55084ATTOGuest
Here are stats for this cell:
SD Congestion = 10.33%
SD Mean Holding Time= 8.79
SD Traffic = 10 Erl
Define SD =3 SDCCH/8.
I have another boundary cell which have got 89% of SD congestion yesterday and SD Mean holding t = 8.74.
What do u think??22nd December 2008 at 15:49 #55085PixGuest
What about: SDCCH availability (all SDCCH are working ?) 10% congestion with 10 erlangs only, it looks like only 2 SDCCH/8 are working.
If they are all working, then you could assume that there is a peak of sdcch traffic during 30 minutes in the cell. Since you see the traffic erlang during one hour, it doesn’t look that high. But actually, you have most of the SDCCH traffic in 30 minutes (–> 20% congestion) and less traffic in the next 30 minutes. In average, it gives a congestion of 10%.
It can happen in case of “bursty” traffic, such as when many MS are crossing the boundary at the same time (a train, end of working day, traffic jam, …)
Perhaps you could increase the periodicity of your QoS reports, to verify this assumption ?22nd December 2008 at 17:12 #55086ATTOGuest
I check with PM viewer and see that i have some peaks of SD requests (probably due to bus/train crossing the locating area).This is why i’ve got 10% of congestion.
What really bothered me is the high Mean holding time? Any idea what can i do to reduce it? I assume that it comes from the NSS side but i don’t know which parameter to tune.18th February 2009 at 06:46 #55087habibGuest
What is mean Holding time ?18th February 2009 at 06:52 #55088habibGuest
Defination and Mathematical relation for Mean Holding Time (MHT) in telecom traffics23rd February 2009 at 12:54 #55089bailloGuest
how to solve too many drop of SD due to low ss strengh?23rd February 2009 at 14:00 #55090moustoGuest
DL or UL ss?18th June 2009 at 10:55 #55091Wesley KiruiGuest
I have 3 ALCATEL BSCs, 3 E/// BSC and the core is E///. I need to know if LU TIMER T3212 really affects CSSR. If Yes what value should you recommend for a network ok only 500 sites and less than a million Subscribers?18th June 2009 at 16:36 #55092PixGuest
you can use a value of 4 hours, it’s quite standard. Since you have a low amount of subscribers, I doubt you’re looking to offload your MSC/VLR.
To increase your cssr… mmm. it depends if you take the paging success rate into account.. probably not.. but for sake of argumentation : if yes, then you could try to reduce the T3212 a bit, see if it changes anything, but you must also reduce the implicit detach timer in NSS :
Some (most ?) mobiles do not send an IMSI DETACH when their battery runs off. The Periodic LU will force the MS to send a LU every T3212. If the MS doesn’t do it, then the NSS will perfom an implicit DETACH, based on a certain NSS timer (t-something).
Pix28th February 2011 at 13:36 #55093brianGuest
In Erricson network what normaly causes sudden SD congestion which affect cells randomly due to sudden increase in the number of call attemps(which cannot be accounted for)?18th September 2011 at 07:42 #55094maryGuest
I want to know which factors affected the SD mean holding time in cell?12th March 2012 at 10:30 #55095Khursheed AlamGuest
How is SDCCH mean holding time is affected by the hunting method for a BSC route? If one BSC is connected to two MGWs with two corresponding routes and one route has more number of devices than the other, how will it affect the SDCCH mean holding time in that BSC? Is there any method to quantify its impact on SDCCH mean holding time?13th March 2012 at 08:56 #55096pixGuest
I don’t think the MGW would impact much the SDCCH MHT. Indeed, the SDCCH is used to transfer informations between the MS and the Call Server, not the MGW.
I’m not an expert on this topic, so there is perhaps more to it than that.