How to offload CS Traffic in WCDMA in direction GSM?

[etdoja]

Hi guys,

I've a very interesting task for all optimisation guys, that are familar with E******* equipment.

Due to the huge load of PS traffic due to the smartfone boom, I faced with a massiv RRC admisson denied issue on a dense urban NodeB.
The station build up as GSM 900/1800/WCDMA structure, where the WCDMA RBS is in admission denied state most of the busy hour time, while the GSM RBS could take some of the CS traffic (mean 60-70% loaded during busy hour time).

The aim should be to minimize the number of RRC admsiion denied, hold the PS traffic in WCDMA and as much as possible CS traffic in GSM.

To enforce this in my opinion there are three possiblities, they are in fight to each other

1. Directed Retry of CS traffic
2. Optimal parameter settings for cell reselection from GSM to WCDMA
3. Optimal parameter settings for IRAT HO

All these possiblities can be used to offload the WCDMA RBS, whereby 1.) and 3.) must already have an active RAB, which not really helps in case of RRC admission denied

So at the moment I only see the possibility to find the correct parameter setting in such kind of situation OR an therefore I'm posting this thread you guys have other additional ideas to face this problem.

Let me know.
Rgds

[ninjafine]

Hi! I would first check what is the reason of huge RRC Request. Is the cell in LAC border, are there a lot of IRAT reselctions? The second step is to check the cause of RRC Admission Rejects. Is it due power, codes, hw?
Thanks and reps are appreciated.

[elmorabet]

if the network has second carrier

[etdoja]

Yes the network has a second WCDMA carrier and as far as I could analyse the performance of the second carrier is more worse than the first carrier. Additional to that the inter frequency load sharing is activated between both carriers and in both direction, but I don't know why the IFLS seems only to work from the 2nd to the 1st carrier ???
More than this HSDPA is activated on the 2nd carrier...

[etdoja]

Re: How to offload CS Traffic in WCDMA in direction GSM?

Hi! I would first check what is the reason of huge RRC Request. Is the cell in LAC border, are there a lot of IRAT reselctions? The second step is to check the cause of RRC Admission Rejects. Is it due power, codes, hw?
Thanks and reps are appreciated.



The reason for huge RRC requests are a lot of RRC-requests with cause "pmTotRrcConnectReqPs" (90.000Atts), whereby there are IRAT reselection atts only 20.000 in average. The cell is in the middle of a LAC, so unfortunately/fortunately no LAC borders. The cell (with cell I mean not the whole NodeB) has in average 10.000 rejections by admission control, most of them due to dl-power.

[ninjafine]

Hi. You can decrease number of RRC Request PS by introducing URA_PCH. Since there are rejects due power and second carrier activated you may not have enough power in Radio Unit. What type are you using 20W, 40W, is it remote RU? You may also play with PCPICH power in order to have 10% from available power for this sector.
If you are familiar with GPEH you can send it to me and i'll analyse it for you.
Thanks and reps are appreciated.

[etdoja]

Hi. You can decrease number of RRC Request PS by introducing URA_PCH. Since there are rejects due power and second carrier activated you may not have enough power in Radio Unit. What type are you using 20W, 40W, is it remote RU? You may also play with PCPICH power in order to have 10% from available power for this sector.
If you are familiar with GPEH you can send it to me and i'll analyse it for you.
Thanks and reps are appreciated.

Thx for your ideas.

As far as I know URA_PCH is a feature by E*******, that has to be licensed, right? If it's like that, may be the reason why the operator I'm working for, isn't using.The remote unit is using 40W (20W for each carrier), the PCPICH power is already increased to it's maximum value :-(

I know the tool GPEH, but never used before. How this tool can support me in this prob?

Thanks in forward

[ninjafine]

Right, feature has to be licensed. Do you have equal load between carriers in terms of RRC requests and traffic distribution? If IFLS works from the 2nd to the 1st carrier nevertheless performance on 2nd carrier is worse you may have different coverage or wrong neighbors defined between carriers. Is blind camping strategy used? Maximum value for PCPICH isn't a good decision since you have problem. Check also ping-pong effect between WCDMA-GSM since you have so much IRAT reselections.
Regarding to GPEH - all this questions wouldn't be needed if you have GPEH (send me a PM if you are interested in).
Thanks and reps are appreciated.

[etdoja]

Right, feature has to be licensed. Do you have equal load between carriers in terms of RRC requests and traffic distribution? If IFLS works from the 2nd to the 1st carrier nevertheless performance on 2nd carrier is worse you may have different coverage or wrong neighbors defined between carriers. Is blind camping strategy used? Maximum value for PCPICH isn't a good decision since you have problem. Check also ping-pong effect between WCDMA-GSM since you have so much IRAT reselections.
Regarding to GPEH - all this questions wouldn't be needed if you have GPEH (send me a PM if you are interested in).
Thanks and reps are appreciated.

The comparison between 1st and 2nd carrier in terms of RRC requests is 90:10! , this due to a parameter setting qoffset2n -50 and +50 for the 1st carrier. Neverless then this the 2nd carrier makes a lot of IFLS to the 1st carrier, while the 1st carriers has 0 IFLS atts.

Sorry, what do you mean with blind camping strategy and what do you mean with PM?

Why do you think, that max value for PCPICH isn't good decision? I don't think, thaat the cell has a prob, more I'm interested in finding a way to offload the 1st carrier in direction GSM (CS traffic) or to the 2nd carrier (PS traffic).

Thx in forward

[kais]

1.DRD
2.LBHOA
3.SBHO