- This topic has 7 replies, 1 voice, and was last updated 15 years, 9 months ago by NK.
7th February 2008 at 09:12 #50754DuxGuest
We saw a huge increase in SDCCH congestion in a 15 min period at 1am. Yesterday no congestion in sites but today we saw SDCCH requests jump to 37000-50000 on different cells in different towns.
After one 15 min period everything returned to normal but throws statistics through the roof for whole day.
Question, Does anyone know what would have caused such an increase in SDCCH requests, there were no traffic channels requested and no SMS traffic?7th February 2008 at 10:15 #50755AbdelGuest
Can you check whether the LAI of the neighbouring cells are the same if not then it will generate a lot of location update, plus authentication, and IMEI checking this is a great deal of signalling flow generated by the Subscribers who entered that cells with the different LAI. There can be other reasons.8th February 2008 at 03:59 #50756NKGuest
Check also BTS is up after down for a certain period or not. Generally, MS performs LU if BTS is up after down for a certain period.
NK8th February 2008 at 08:42 #50757PixGuest
As NK said, it certainly has to do with a massive amount of location updates (you can see perhaps that the SDCCH were allocated for LU ?)
The main possibility is that at 1am one of your competitor operator had several BTS down, de to BSC outage, or Abis outage probably. At that point, all the subscribers of this operator will search for another network and probably select your cells. Once the BTS were up again, subscribers would gradually reselect automatically their home BTS (timer defined in MS).
Another possibility is that your own subscribers performed a location update all at the same time. This can be due to (as NK said) some problem with the BTS (but i don’t really see how…) or at NSS level : the MSC asked many MS to perform a location update at the same time. Were there any MSC action last night ?
Pix8th February 2008 at 19:48 #50758DuxGuest
No, no MSC activities but Pix you was right. It’s because of other operator. They lost BTSs at the same time
in several different areas.
Tnanks9th February 2008 at 21:10 #50759TNSGuest
In this case you have a national roaming, yes?
“… This can be due to (as NK said) some problem with the BTS (but i don’t really see how…) …”.
If in dense urban area we have one BTS down than nothing happen – all MSs will reselect the BTS following the reselection criterea.
If we have some BTSs down ( or one in rural area ), so we have a MSs without coverage.
In the moment of BTSs up there will be a large number of network registration procedures with all attended events…
TNS11th February 2008 at 11:32 #50760DuxGuest
Yes TNS12th February 2008 at 04:15 #50761NKGuest
During Traffic analysis, I found that SDCCH congestions were extremely high but voice traffic were low. When I checked radio command, the sites were down. This had happened in urban areas where we had a lot of cells. Even one cell was down, the neighbor cells used to serve that area without latching in external network.
I do not understand why MS performs LU. But my MSC’s colleague told me that once site was down , MS performed LU when the BTS was UP again.
We are using Siemens network.
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