Repeated FACCH/SACCH

[Ghost78]

Hi;

I'm going to activate Repeated FACCH/SACCH feature in B11 ALU for test, my question is how to choose cells where the feature will be activated in order to see the impact of this feature on the network, if anybody has the response of this question, I'll be very grateful, Please it is very urgent, I need the reply very quickly.

B.R

[djordjebeg]

NO visible improvement BUT we have seen some problems with feature itself. If BTS is high loaded you may face TCH blocking if feature is activated. That is why we have disabled feature in the network.
maybe if you have only TGT and MCPA TRXs you will not face issue but with old HW ( G4) it is nightmare.
Solution is introduced in B12.

regards,

[Ghost78]

1st of all thx for the reply,
your are not the firt one how faced this problem, i don't know why this feature didn't bring any improvement because i don't tested yet, that's why i'm trying to post to avoid such problem.
I heard that it is preferable to activate it on cells with low AMR codec rate, is that true ?
PLZ correct me if i'am wrong : my chosen zone must
1. contains MS wthis xACCH capable (retreived from NPO (MS_repeated_ACCH_capable))
2. has high AMR_call_drop_radio (for RSACCH)
3. has high AMR_call drop HO and low Out HO effeciency rate (for RFACCH)
PLZ i need your response as soon as possible.

[djordjebeg]

Hello,

you are righta bout all tree conditions. also please don't forget to increase a bit your AMR Radio link TO because you will have more robust SACCH and you need to compensate repetitions.
In fact when you have lower amr codecs probably you have bad c/I --> probability to fulfill conditions for repetitions is high --> gain from ACCH is higher.

I am very interested to see you results. I expected much from from this feature. anyhow 15% drop gain you should be able to achieve...

regards,

[electron]

Based on feature concept you have to see improvement in HO success rate specially in lost HO failure shall see improvement as well as TCH Drop ratio. Based on my personal experience after activation there was very good improvement in TCH Drop rate in BSC level.

Hope it helps you

[Ghost78]

Hi experts,

In fact, i choose 3 areas wich cells meet the following criteria:
area 1 : all cells having high radio drop rate precisely high AMR_call_drop_radio_NoRSACCH_rate, to activate RSACCH (UL+DL)
area 1 : all cells having low HO_Out_efficiency_rate to activate RFACCH (DL)
area 3 : cells suffering from bad radio conditions (low HSR and high CDR) to activate both RSACCH and RFACCH simultaneously
actully, i'm not really sur about HO_Out_efficiency_rate, is it a good criteria in wich we base to activate RFACCH?
PS: thx djordjbeg for your suggestion to increase RLTO, i'll take it in consideration.

PLZ your comments
BR

[Ghost78]

PLZ your comment

[Ghost78]

Hi ,
Upon activation of RxACCH, the following occurs :

RSACCH : decrease call drop_rate (radio_call_drop)
RDFACCH : increase call drop_rate (radio_call_drop) and decrease Handover success rate, without any impact on OUT_HO_efficiency_rate

I can't understand the results, PLZ your help
BR

[Ghost78]

Hi experts,
After deep investigation about this feature, i conclude the following :
For Repeated FACCH,
- Legacy MS (older than Rel6) have problems to manage repeated FACCH message different from I-frame (So, i'll prevent the repetition of those frame for such MS type, or disable repeated FACCH for of Legacy MS)
- In ALU doc, its mentioned that 40 ms will added automatically to T200 timer (for HR and FR) when repeated Facch is activated, to avoid timer expery before the repetition of any frame, but when i tested this feature (RDFACCH), Call_drop is considerably incresed (incrrese of call_drop_other_causes, which is triggered if there is any LAPDm PB, which means timer expiry), for this reason, i think that the 40 ms was not added to T200 timer, so as a 2nd solution, i'll add this 40 ms to that timer to confirm my suggestion

Any comment, suggestion, or question on this topic, will be helpful
BR