- This topic has 28 replies, 1 voice, and was last updated 3 years, 2 months ago by Jammie.
7th January 2008 at 10:34 #50302ralaGuest
If you found the high SDCCH MHT, what should be the cause of the problem? Thx in advance. 🙂7th January 2008 at 16:18 #50303PixGuest
What is the value measured ??8th January 2008 at 03:00 #50304ralaGuest
Thank you very much for your reply.
The normal of SDCCH MHT about 4 seconds but we found some BSC has about 4.5-5 seconds.
Regards,8th January 2008 at 05:10 #50305PixGuest
The average BSC value is 4.5 to 5s. It means that within this BSC, some cell might actually have up to 8 or 9 seconds SDCCH MHT. Can you confirm ?
If that’s the case, you should check the split of SDCCH causes : do you see a lot of SMS ? SMS requires more time to be transmitted than a call setup.
Do you measure a lot of SDCCH drop ? When the radiolink between MS and BTS is broken, the time to detect a SDCCH drop is about 9 seconds.
During these 9 seconds, the SDCCH is still active. Therefore, if you see a lot of drops, it can also cause a long MHT.
Typical cell value ranges from 3 seconds to 5 seconds (and more if there are a lot of SMS’s)
Pix8th January 2008 at 07:03 #50306ralaGuest
Thank you for your answer. 🙂
For more question related to this article, if we have split the BIG Location area to make the Location area smaller, can it make the SDCCH MHT decreased?8th January 2008 at 07:17 #50307PixGuest
No i don’t think so… reducing the LA size will decrease the Paging load, and increase the amount of location updates. But the LU duration is about 3 or 4 seconds (AFAIK), and that’s already your average. Mathematically, it doesn’t make sense 🙂
Location Area should be as big as your Paging capacity allows.
Really, have a look cell per cell (what’s max MHT per cell ?) and split the sdcch cause. The location area is probably not the problem, that’s why I didn’t include it in my previous post.8th January 2008 at 07:42 #50308ralaGuest
I agree with you Pix.
But one thing that I can see after the LAC split(in the very large LAC and has huge paging load)is the SDCCH MHT decreasing(At the BSC level, daily statistic) about 0.5 seconds.
Is it possible that before we split the LAC the huge paging load make the SDCCH load so the SDCCH MHT is a bit high? Am I correct?
Warmest regards,8th January 2008 at 10:11 #50309pixGuest
PCH load and SDCCH load… it’s not related, theoretically. Those are two distinct physical channels, carrying data from different processes (Paging : broadcasted DL “ping” of a subscriber, SDCCH : dedicated channel for call setup, LU, SMS, etc.).
I can imagine that if the BTS has an overloaded CPU, because it’s trying to manage too many pagings, it might delay all processes including the SDCCH phase.
any other idea why ??9th January 2008 at 03:00 #50310ralaGuest
Thank you so much Pix.
Your answer is very useful for me. : )9th January 2008 at 04:38 #50311ralaGuest
One more thing that I see after split the LAC is the Location update in the cell that have the SDCCH MHT decreased is very high.
How long time the location update use the SDCCH channel when compare to the others(MOC, MTC)? Is it shorter?
(If it is shorter it might be the cause of the SDCCH MHT decreasing.)
Regards,9th January 2008 at 05:55 #50312PixGuest
yes, it’s shorter. as i said, it’s about 3 seconds…9th January 2008 at 07:21 #50313ralaGuest
In your point of view,
if the LU requires SDCCH = 3 s.,
how about the call set up?
I try to find out these time from TEMS, the time from “Immediate Assignment request” to “Immediate Assignment complete” of call set up and LU is about 2 s..
Regards,9th January 2008 at 14:39 #50314WaterGuest
Hi guys, please help me.
some three weeks ago, we started experiencing an increase in sdcch traffic, meanholding time, sdcch drop,sdcch congestion in almost every cell in our network.
I checked whether sms trends have changed some how, but there hasn’t been any changes.
What could be the cause of such an increase in sdcch measurements.
thanks9th January 2008 at 16:27 #50315pixGuest
This is not SDCCH DURATION !!
SDCCH duration starts at IMMEDIATE ASGNMENT COMMAND and finishes when the SDCCH is released (switch to TCH, end of location update request, end of SMS, drop, etc…)9th January 2008 at 16:29 #50316pixGuest
2nd part of the post :
typical duration of sdcch :
LU is short
TC is short
OC is long
SMS is long