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29th July 2008 at 07:50 #53288OptimGuest
I have 3 BSC (2 Alcatel and 1 Ericsson) connected to the MSC via an Ericsson MGW. Cells connected to these BSC are having high SD congestion. These problem appears when the traffic increase on these BSC but the MGW is using max 35% load of processor and we are under the threshold (80%). What can be the problem? Please help!!30th July 2008 at 06:04 #53289peyoGuest
i don’t understand wher’s the problem. sd congestion is at cell level. MGW can have A 10,20..80% load there’s no difference. increase the number of SDs on congested cells that’s what we use to do if sdcch congestion is really due to traffic increase30th July 2008 at 16:04 #53290OptimGuest
We have enough SD on each cell to support the SD traffic. So normaly we should not have SD block. But all the cells connected to these BSCs which are connected to the MGW are having high SD congestion. We have another MGW which are connected to the MSC but don’t have this problem. The problem appears when the MGW accessibility get low (Under the threshold 99.7%). There is not alarm showing equipment problem on the MGW.30th July 2008 at 19:00 #53291pixGuest
could you check out the SDCCH average duration ? do you notice an increase here as well ?
if it is the case, then you could simply perform a drivetest in a cell with this problem, and see where is the delay : during authentication ? ciphering ? tmi reallocation ?
a sdcch phase which is too long will lead to more ocupancy –> higher congestion.
you confirm that the sdcch erlang has increased above the sdcch capacity of the cell, right ?31st July 2008 at 07:18 #53292BlitzGuest
What do u mean SDCCH average duration may cause congestion? Could give me example. Thanks.31st July 2008 at 09:40 #53293pixGuest
if you have 1000 sdcch req. and each sdcch usage lasts 3.6 seconds –> 1 erlang
if you have the same 1000sdcch requests, but due to delay in the authentication or ciphering phases (or tmsi reallo), each sdcch lasts 7.2 seconds –> 2 erlangs
the duration of the sdcch affects the occupancy of the channels.
got it ? or you need an analogy ? at the supermarket, whether each client stays 30 seconds at the cashier or 10 minutes, that will highly impact the “congestion”. The queue of clients will greatly increase if each stays 10 minutes. I can relate to that :)) i always choose the wrong queue at the supermarket.
pix31st July 2008 at 11:23 #53294OptimGuest
We have a bouncing SD traffic following the low availability of MGW.
By SD average duration, do you mean SD mean holding time? This counter also increase when we have congestion.
For example Cell_x: SD traf 17Erl, Avail SD 24, SD block 55%, MHT 9s
And the next day we could get Cell_x: SD traf 6Erl, SD Avail 24, SD block 0%, MHT 3s.
BR.28th March 2009 at 13:22 #53295StagGuest
Check the number of SCCP. We experienced the same thing last time. The SCCP was not dimensioned to the network traffic.28th March 2009 at 13:39 #53296PixGuest
yes, that’s the same.
The increase of MHT leads to an increase of traffic, because traffic = MHT * (number of requests).
And MHT increases because … the MGW is not responding asap to the MS, therefore the SDCCH channel is busy longer, awaiting for a MGW response.
I’m a noob with NSS…
With a media gateway, i assume there is a call center, connected by IP to the BSCs ? Therefore, the number of SCCP (or COC) is probably unlimited… since it’s over IP. am I correct ?