High SD Congestion on Colocated WCDMA Cells

[Muhammad Imran Rafique]

Dear All,
In E******* network (STC Project) we are facing a strange behaviour as

With very low SDCCH traffic, cells are showing high SD Congestion. Kindly suggest what can be the reason and it is very common through out network. How we can overcome it and kindly explain at which particular instant logically this can happen. I am looking forward for quick response.

BR//
Imran
+966 53 420 35 17

[pioneerelex]

Dear All,
In E******* network (STC Project) we are facing a strange behaviour as

With very low SDCCH traffic, cells are showing high SD Congestion. Kindly suggest what can be the reason and it is very common through out network. How we can overcome it and kindly explain at which particular instant logically this can happen. I am looking forward for quick response.

BR//
Imran
+966 53 420 35 17

is this problem happened suddenly or gradually?

Did you check where did the SDCCH traffic com from? (SDCCH traffic split can help you).

Is it come from excessive location update?

[Muhammad Imran Rafique]

As you know in e******* we cannot exactly find number of LAC update as it comes under RACH "OTHER". But we donot see any abnormality in terms of LAC updates.

There is certain cells in network where it happens regularly i.e. very low SD Traffic but high congestion. Kindly share the logical and technical reason behind it.

br//Imran

[narula.pawan@gmail.com]

Dear Imran,
I want to ask following things regarding Same:
1.) Is the SD Congestion high in particular hour in the day? if yes then is this Busy Hour or some other hour in the day?
2.) Is this Congestion high in more than 1 hour or not?
3.) Also Can we have SD Traffic Distribution(MOC+MTC+LU+SMS) during those hours(where SD Congestion high) w.r.t other Normal hours where no SD
Congestion?
4.) If LU is high then what is the Distribution of Location Update(Periodic Update+IMSI Attach & Detach+Normal Update)
5.) Last but important point,as you said that SD Congestion is high for a cell which is co located with WCDMA Cell, then what is the behaviour of Incoming IRAT HO Request from 3G to 2G in that particular hour w.r.t to other hours.

Please let us aware above mention points for further optimization.

Br..
Pawan

[rezapa]

Hi Imran, check if those 3G sites have any sort of instability, go on/off frequently due to HW or transmission problem?
Very traffic and high congestion generally happens when too many subscribers send a request exactly at the same time. This way, overall SD traffic in 1 hour is low, but because too many attempts are made in 1 sec, you'll see congestion. Examples of such behavior are: conference rooms or movie halls (where many people switch phone on/off almost in the same time), cells covering railways (where many people cross the LAC border altogether) OR, in your case, when the 3G cell goes off many mobiles are made to search the network again and login to a GSM cell all at the same time. I had this problem once and it was removed after HW check on 3G site. Hope it's useful.

[rffreeconsult]

Short cut to alleviate SDCCH congestion: Check your Location Update timer, and if your site is in High-traffic area (with low mobility) a.k.a HotSpot, change it to 4 to 6 hours, that way you can reduce at least the automatic LU attempts, continue to monitor it and see if it works...Usually, Vendors tend to set the value low (1 or 2 hours) but operators' investigation have shown that 4 hours can be much more appropriate (Sorry that the operator name can not be communicated here for confidential reasons)...but you can be assured that 4 hours is ok...

[white_Noise]

Hi, Check the Qsearchi parameter in 2G, If it's set to 15 then the MS will prefer to camp on 3G in the Idle mode, in that case, after each call, you will have
LAC and RAC updates after each call, which consumes the SD resources, If that's the case, then you need to add extra SD slots, of modify the reconfiguration settings so to
better utilize the availble resources.

Cheers..