- This topic has 17 replies, 1 voice, and was last updated 13 years, 5 months ago by SSK.
15th June 2008 at 09:12 #52725samarGuest
Can any one please explain me what are the reasons for immediate channel assignment failure?15th June 2008 at 11:21 #52726pixGuest
congestion of the sdcch channels
dummy channel requests
hardware/software failure (especially TRX or signalling board at BSC side))
or, more obviously
poor radio coverage
high radio interference15th June 2008 at 13:46 #52727samarGuest
Thanks pix.16th June 2008 at 06:26 #52728peyoGuest
or phantom rach.
in case of causes mentionned by Pix you should see repeated rach. of course its not easy to identify because rach repetition (managed by max_retran in term of number) keeps in some ways the random aspect of Rach. Which bss is it?16th June 2008 at 11:47 #52729pixGuest
dummy channel requests = phantom rach16th June 2008 at 12:32 #52730peyoGuest
ok 🙂19th June 2008 at 11:04 #52731SAMARGuest
Pix, according tour points I have checked the site and I didn’t found any High Interference there and also signal strength is around -45dBm to -50 dBm. Yes according to my BH report SDCCH congestion is 35% there before available SDCCH was 24 now it’s 32 but doesn’t make any difference.
Actually in that site only one sector is having this problem other two is clear. Basically I am RF Engineer. I don’t know much about Hardware or software. I can only say that we are using SIEMENS 240xl BTS there and 120 HC SIEMENS BSC.
Can you please tell me how to check the dummy channel requests??
Please give me some light on this issue.
SAMAR19th June 2008 at 11:21 #52732SAMARGuest
One thing i forgot to mention. We check both HW (replacing combinder and CU) and SW(DB file) but we didn’t find any error.19th June 2008 at 14:28 #52733samarGuest
Waiting for your opinion.19th June 2008 at 18:29 #52734AterGuest
hi SAMAR. Do you have customer claims ( what kind of claims)?
How high is the voice traffic in the cell.
How high is the GPRS traffic in the cell ( do you have dedicated PDCHs on that cell?)20th June 2008 at 08:16 #52735samarGuest
Yes customer claim there is like they are having “No connection error” In there MS.
Voice traffic is not so high. Utilization is around 30%.
We are not using dedicated PDCH and also traffic is very less as it is in a rural area.20th June 2008 at 13:48 #52736AterGuest
If there is no high voice, SMS or GPRS traffic, no interference, if its not a LAC border and the neighbour cells are fine. There is no reason for SDCCH congestion
There are a lot of parameters in siemens that impact on the immediate assigment procedure. But it seems ( this is a hunch) that you are experimenting configuration problems. You should contact your vendor or try a drive test and see what you find in there. Please let me know how you have solved the problem20th June 2008 at 16:15 #52737pixGuest
i would have suspected, as ater said, sdcch congestion due to location updates or phantom rach. Check what is the cause of sdcch traffic : loc upd, imsi detach, sms, call setup ?? you should be able to find this “split” in your indicators.
other thing : what is the sdcch traffic in erlang at the busy hour in your cell ?2nd July 2008 at 09:02 #52738samarGuest
The problem was solved after replacing the hardware (CU)
Thanks to all for helping me.
SAMAR2nd July 2008 at 10:25 #52739pixGuest
glad you fixed the problem. Just one thing, when you said :
“One thing i forgot to mention. We check both HW (replacing combinder and CU) and SW(DB file) but we didn’t find any error.”
you got us working based on wrong information…