- This topic has 15 replies, 1 voice, and was last updated 12 years, 12 months ago by Bijoy.
30th November 2009 at 14:21 #59818prideyGuest
we r facing very abnormal nature in nokia network regarding SDCCH blocking.
Avg %SDCCH blk during N/w BH never goes below 1% without TRX sof reset everyday before BH.
Around 10/15 cells giving a tot of 4 lacks sdblocks out of 1 cr sd attempts, each cell around 1 lacs sdblk sometimes. But the fact is , those bad cells never repeat next day, but some other 10/15 cells do the same. hence the typical nature “who is when” is not predictable , not even before start of busy hour.
Due to inconsistancy of the bad performing cells , we cant guess any s/w or h/w issue.
Although , enough sdcch augmentation done after weekly sd dimensioning, sdcch is in excess in the n/w. So lack of sd is not an issue.
What could be the issue/how to handle it, just running out of ideas.
keenly looking for suggestions.1st December 2009 at 05:58 #59819BijoyGuest
1.Are you guys using 16 KBPS LAPD links?
2.Is there Signalling overload in BSC’s?
Bijoy1st December 2009 at 07:00 #59820prideyGuest
Thanks for your reply.
1.yes. But now a days we r upgrading to 32 kbps LAPD for BCCH TRX only and for entire n/w.
2. By Signalling overload in BSC’s, do u mean Abis TRXSIG load ? If not, then pls explain once more.
If we change MAXRET from 4 to 2 and also reduce DMAX, will it help?
what are the parameters are directly related to sdblock?1st December 2009 at 08:20 #59821BijoyGuest
1.16 KBPS LAPD Links can support upto 12 SDCCH channels & a maximum of 18 channels at any time.So,if in a particular TRX if you are using 2 SDCCH & rest are TCHD,there is every possibility of TCH/SDCCH blocking & drop.
In non-BCCH TRX also,take care of this fact & keep only 1 SDCCH & at max 3 TCHD.
2.Check with the command “ZOLT;” in BSC,if TX/RX Erlang >0.2 in BH,need to add SL(if < 16 SL) or augment(64 KBPS to 128 KBPS). Yes,reducing MAXRET will help. Reducing DMAX is a cynical way of reducing SDCCH Blocking Br\\ Bijoy2nd December 2009 at 08:22 #59822prideyGuest
Thanks a lot.
In nonBCCH TRX if we keep 1 sdcch & 3 TCHD, then what will be rest 4 timeslots? provided LAPD is 16 kbps.2nd December 2009 at 10:37 #59823ramanGuest
Hi Bijoy Sir ,
you are saying that “in BSC,if TX/RX Erlang >0.2 in BH,need to add SL(if < 16 SL) or augment(64 KBPS to 128 KBPS)." ...... But our switch team is saying that on LSL if on any SL greater than 0.7 eRL. than only they can go for C7 augmentation is there any doc ...for support for that or calculation in support for that ..... plz tell3rd December 2009 at 11:14 #59824BijoyGuest
Remaining RTSL will be TCHF
This is a NOKIA system recommendation for 64 KBPS SL with 25 merl/sub.Refer NED for details.
Bijoy3rd December 2009 at 17:56 #59825ramanGuest
I am in Eric/// system agreed concept would be same in that system also plz give any doc regarding E./// …
plz give NED doc any help would be highly helpful for network ….plz mail to
email@example.com December 2009 at 04:52 #59826BijoyGuest
In ericsson,its a bit complex
Let me know if you are talking about TCAP load or TRH Load?
Can you provide me the sample data.4th December 2009 at 05:57 #59827BijoyGuest
In Ericsson too
The maximum traffic load per 64 kbit/s link is:
0.3 Erlang under normal conditions
0.6 Erlang under failure situations
and for a 56 kbit/s link or HSL the maximum traffic load is:
0.4 Erlang under normal conditions
0.8 Erlang under failure situations
Please go through “BSC/TRC Dimensioning” chapter in Alex for details.
Bijoy4th December 2009 at 09:46 #59828ramanGuest
i am not able to find plz can you give specifically exact where it is written ……thank a lot ///15th December 2009 at 17:42 #59829prideyGuest
Hi Bijay, thanks a lott.
We hv 1800 cabex also, so “1 sdcch per 3 tchd max” rule should count 1800 trx aslongwith 900 trx or applicable for 900 only.
point 2 is: what are the parameters to ‘fetch’ calls from HR to FR.
what % of total call should be HR out of total voice traffic, to reduce sd blocking at minimum.
and , does “total HR traffic” = “Non AMR HR + “AMR HR”16th December 2009 at 04:32 #59830BijoyGuest
If you are using Common BCCH with 1800 as non-BCCH band,you are not defining SDCCH on 1800 TRX,do you??
In that case all RTSL’s can be configured as TCHD.
Well,if you are using Dual band N/w(BCCH in both 1800 & 900),the same rule of 900 applies for 1800 too.
FRL & FRU is the most primitive one to do so.
Lastly,your HR% should be 20-30% ideally.
Bijoy16th December 2009 at 04:35 #59831BijoyGuest
“Total HR traffic” = “Non AMR HR” + “AMR HR”
In alex,there is a chapter called”BSC/TRC domensioning”,you can find it there.
Bijoy16th December 2009 at 07:18 #59832prideyGuest
Thanks you very much. Its really works for me.
Just want to clarify the following.
we hv common bcch for 900 & 1800
“In that case all RTSL’s can be configured as TCHD.
“. So it means all 1800 rtsl are tchd.
An expl: In a segment w, say both 900& 1800 exist, with common BCCH in 900. Also 900 has 3 TRX & 1800 has 2 TRX in the same segment under common BCCH.
All TRX lapd are 16 kbps.
TRX 1 in 900: MBCCH, SDCCB, TCHD,TCHD,TCHD,TCHF,TCHF,TCHF.
TRX 2in 900: SDCCH,TCHD,TCHD,TCHD,TCHF,TCHF,TCHF,TCHF.
TRX 3 in 900: SDCCH,TCHD,TCHD,TCHD,TCHF,TCHF,TCHF,TCHF.
TRX 4 in 1800: all TCHD
TRX 5 in 1800: all TCHD
Does such a config do well with % sdcch blocking? (I hv kept “1 sdcch per 3 tchd max” rule valid)
OR all the 1800 RTSL should be TCHF?
Is there any other parameter other than FRU,FRL?
What are the parameters values to set for minimum % SDCCH Blocking?
MAXRET to 02 from 04? any other?
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