- This topic has 12 replies, 1 voice, and was last updated 10 years, 11 months ago by Mania.
12th February 2010 at 13:57 #61043dannnGuest
Hi guys. Im experiencing some extraordinary SDCCH congestion on one site located at a LAC border. The vendor in that area is Ericsson. For most cells at LAC borders, we are using CRH=6 but this value ain’t working for this two cells.
Would someone kindly assist on this?13th February 2010 at 15:23 #61044safarGuest
u can also put c2 value and will control sd congestion18th February 2010 at 23:12 #61045LouisaGuest
how do I calculate the SDCCH congestion, also the TCH congestion?19th February 2010 at 09:23 #61046pixGuest
for tch congestion, count the number of 48.008 ASSIGMENT FAILURE (cause: “no radio resource available”)
for sdcch congestion, it’s triky :
count the number of times a 48.058 CHANNEL REQUIRED is received by BSC but **not** followed by a 48.058 CHANNEL ACTIVATION (sent from BSC to BTS).
count the number of IMMEDIATE ASSIGN REJECT (available only if the feature is activated)
pix19th February 2010 at 11:37 #61047BijoyGuest
What feature are you talking about??
We dont need any feature to count IMMEDIATE ASSIGN REJECT in OSS.Do we??
Bijoy20th February 2010 at 05:06 #61048PixGuest
No, but there will be Immediate Assign Reject to be counted only if you allow the system to send them.
So you need to activate the feature, otherwise you’ll just count “zero” all the time 🙂
(which is not a problem actually… is that what you mean ?)
pix21st February 2010 at 07:55 #61049BijoyGuest
As far as I know,BSC sends IMMD Assgn Reject to the MS each time for
1.no available channel
2.channel activation failure
3.channel activation timeout
for each type of access reason.I dont know any such feature in any vendor which prohibits this(except ALU).
Also,you are right,we dont need to count this,as we need to count only SDCCH seizure requests & successful SDCCH seizures to account for SDCCH Blocking.
Bijoy22nd February 2010 at 06:19 #61050LvinGuest
hi to all
who can help us about the Erlang?
please we have cells with 20% Tch congestion ,half rate (50% with AMR and 20 without AMR) the Erlangs are 6.
so must the Erlang over 21 because of each cells 4 TRX and TCH availabilities are 100%.
please help us for this problem.
Regards;22nd February 2010 at 18:06 #61051PixGuest
The difference between Request and Success will give you oth congestion rejections and radio failures (or possible hardware failures).
The only way is to count the difference between Channel Request and Channel activation.
This way, the result only shows the rejections dur to congestion.
I didn’t know about the Imm asg Reject feature being so specific to ALU. And the worse thing is that it is disabled by default !
could you check the erlang per TRX, to detect unused TRX, perhaps ?
pix23rd February 2010 at 06:05 #61052BijoyGuest
Channel Activation failure can also happen due to faulty RTSL.Also.Imm assgn reject comes due to Ch,nnel act. timeout.
In all vendors, I think there is an exact counter to account for SDCCCH channel requests rejected due to busy sdcch.
Bijoy23rd February 2010 at 20:23 #61053PixGuest
Yes, there is probably such a counter, that’s true.
channel activation failures are quite rare, but ok, that’s a risk i didn’t mention 🙂
pix21st April 2010 at 03:52 #61054PSRGuest
PSR22nd April 2010 at 06:34 #61055ManiaGuest
I think the best solution would be to drive the area and confirm if the LAC updates are due to pingpong Location updates / genuine updates.
If Pingpong: increase CRH on both cells between by 2dB initially and fine tune.
Other wise you can increase CRH of neighbouring cell towards this cell take it to 8 and then tune.