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I am experiencing high SDCCH Traffic (20 Erlang) in Location Area Borders, this is causing a 50% congestion SDCCH and a high drop in SDCCH as well… This is an Ericsson network. Any help will be appreciated…
hello esamoraglo,
it probably comes from LA update…
you should add some SDCCHs, or do nothing 🙂
maybe you shoud check parameter settings, something like cellResellectHysteresis and so on…tch,
I have checked the cell hysteresis and it is at 10dB in both cells, so this cannot be a problem. I am thinking it a BSC problem because the same thing happens in every border of the LA. Adding SDCCHs is not a solution, I have tried it before and it only increments the traffic. Any ideas?In a nokia BTS there is a parameter called PERIODIC LOCATION UPDATE. Its a timer based on which the the LU are done periodically.
May be you check for such a parameter, if the value is too low say 15 0r 30 mins you may be facing a heavy SD congestion.
Normally the value can be set at 3 or 4 hours.
well study for your LA border route.
You have to modify it it term of averting high traffic area spicialy crossing high way street ,real way & crouded market.So optimise your LAs by shifting border, adding/removing cells & so on.The periodic LU is set o 4 hours, so that doesnt seem to be the problem. The Location area is not crossing any high traffic area, so we can discard this option. I am running out of ideas… To add more information, all the equipment is Ericsson… More ideas pleaaase!
Can this problem have anything to do with the cells having Underlay/Overlay???
hello esamoraglo,
do you know what kind of SDCCH drop is it ?
system drop ?
maybe you should check some traffic management board on your BSCs…Hi,
Do you have longer SDCCH MHT?
We have some phones in our network but still cannot find them because in the ass message for LU there is no info. These phones loose network when crossing LA and continuously try to do a LU – one phone is ~ 1200 attempts per hour. We discover that this is true for a pairs of sectors lets say. Because after 4 unsuccesful attempts the mobile performs forced cell reselection and again 4 att and back…
We have great difference between succsesful seizures of SDCCH with reason LU and succesful assignment of SDCCH with reason LU. SDCCh is released after a timer expires and this is counted as traffic although noone is connected.
Also check routing area update.first of all You ought to check the reason byond SDCCH congestion if it h/w problem or not.
AND check the following limitation:
# air interface(limmited SDCCH resources)
#A interface (limited # 7 signaling resourse).
# BSC (limited prossesor capacity)
# MSC (limited HLR capacity).
FURTHER MORE:
Ericsson have (adaptive configuration for SDCCH and Direct assignment on TCH) so they may help according to your needs.The reason of the congestion is the amount of SDCCH traffic we have in this cell. It is excesive compared to other cells, this is why I thought it was a Location Update sort of problem… It is not an option to increase the SDCCH channels because although you increase them they are still with congestion (the SDCCH traffic increases until it is saturated). What is SDCCH MHT? How do I know if this traffic is due to Location Udates or something else? Thanks in advance…
Do you have some drive test in this area?
The high volume of sdcch drops is let say “normal” for rural areas. This is because location updates are performed on cell edge.Did you try to run CTR for that cell?
In our network we have some problems with failty phones and we found them by CTR.how many cell having such problem & are they border cells or not.??
And what is your sdcch dimention on those cells (are they according traffic mix model or to real statistic).??
And what is your statistics values.
But all this investigation on you r account.MHT=mean holding time=(time the SDCCH is busy in the hour)/(Successful SDCCH seizures).
Assignment is when the BTS allocate the SDCCH and seizure is when the BTS receives the SABM message which the phone sends when it goes to the SDCCH channel.
If the BTS does not receive the message it holds certain time before releasing the channel. And durring this time SDCCH is counted as busy, which means traffic (time the SDCCH is busy in the hour).
You shoud have a separate counter for MOC sms/calls, MTC calls, MTC SMS, and location update.Do you have trains crossing the LU there?
Hi there,
first you need to look upon other SDCCH Statistc. SDCCH MHT normal values should be around 3-3.5 sec.
if they are normal ones and it is Ericsson system as you state, than go to the OSS and shcedule a CTR recording(PMR and afterward choose recording ot channel level). Maximum time is 1h. After the measurements are finished see in the report menu the statistic gathered for selection types. this will help you identify the reason for SDCCH attempts, and see if something abnormal(The selection types you can find in the ALEX/Channel administration feature).If everything is OK, chek your feeder system. Schedule MRR in the RNO to see the path balance,UL/DL quality ets. Afterwards if TCH trafic is low chek the CHAP setting, and if it is 0 change it to 1.
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