- This topic has 76 replies, 1 voice, and was last updated 8 years, 5 months ago by IAN.
22nd March 2010 at 21:21 #59873lilyGuest
Good evening Pix, Sergio and 2112!
Let me join the discussion about using DTX and AMR features simultaneously 🙂
In a new version of so called *common parameters* we are recommended (=must) to use both flags:
DTX_FR_INDICATOR_AMR = Enable
DTX_HR_INDICATOR_AMR = Enable
As I see from this discussion it can be a real danger not only for KPI, but – the most important issue – for subscriber perception, i.e. for real speech quality .
To be true, I don’t understand properly what is the cause of incompatibility for these two features.. Do we have problem both with FR and HR + DTX? In 3GPP TS26.103 we found the only mention about incompatibility between ERF (12,2) and DTX, but I’m afraid we’re mistaken..
Dear Pix, could you be so kind, please, to give some more explanation about this situation (or forward us to certain document) ?
Thanks a million!
Lily23rd March 2010 at 10:28 #59874PixGuest
Please contact your TAC… It’s really difficult for me to “discuss” about problems like this with an operator.
I must emphasize that the issue is not due to ALU equipment, but due to a mistake in the standards. Probably.
The problem itself *might* lie in ETSI DTX VAD2 algorithm, which is not compatible with AMR, as far as i know.
Let us know as soon as the TAC have any news 🙂
pix23rd March 2010 at 13:42 #598752112Guest
Hello PIX, Lily and Sergio,
just want to share our results regarding this Parameter W_Qual_HO,
We tried it for few cells with settings,
A_QUAL_HO = 6
W_QUAL_HO = 2
and result was increase in Interefrence and Quality HOs.
Explanation given to us by vendor was that averaging window becomes variable and is more reactive to transitional degradations in DL RX Quality resulting in increased Quality HOs.
I have to say that this weightage concept was really strange as we were thinking that size of averaging window will remain same and just DTX = 0 measuremnts will get twice the weightage of DTX = 1 measurements and averaging will be over 6 measurements regardless of how many were DTX or Non DTX and denominator of averaging could be modified accordingly.
Needless to say that we have reverted back to orignal settings and we are still having very high DL Interfernce HOs(around 5%) for all of our BSCs where AMR and DTX for AMR HR and FR is enabled.23rd March 2010 at 16:38 #59876pixGuest
why don’t you deactivate the DTX for AMR calls ?23rd March 2010 at 21:01 #59877lilyGuest
Hello, Pix and 2112!
oh, I’m sorry, I really didn’t want to embarrass you.
Next week we’ll implement recommended settings for 3 BSCs (some sort of experiment) and than we’ll make a drive-test in that area, focusing on MOS measurement. I’m looking forward to do it and see the results 🙂 …. :(((
I think it would be better to contact TAC having as much info (DT results and PM statistic at least) as we can collect, in order to have a “meaningful conversation” :)))).
Of course I’ll share results of our investigation 🙂
Thank you very much for sharing your experience, now we know for what we should be ready (changing those parameters)
And just one more question: Did you fix speech quality degradation after AMR_DTX activation (from drive-tests or subscriber’s complaints)?
Thank you in advance 🙂
Good night, 2112 and Pix!
Lily24th March 2010 at 06:09 #59878PixGuest
(dobre … something.. 🙂 )
If I were you I would contacct the TAC right now. You know it is a problem known by them, you know it is due to VAD2 algorithm… just ask them when they plan to have a corrective action about this.
or perhaps you just enjoy drive-tests so much that any excuse is good enough to start the engine 🙂
you know what, i’ll try to contact some friends in the TAC to learn more about this… I can’t stand not knowing for sure !
pix24th March 2010 at 09:05 #59879lilyGuest
Dobroe utro 🙂
I’ll follow your wise advice. Unfortunately now we have no possibility to contact ALU TAC directly, only through our HQ operational department – it will be a little bit longer, but we have enough persistence 🙂 As soon as we get information from them I’ll share it here 🙂
Nevertheless we need practical results as an argument in order to be able to dispute the main (Moscow) HQ if they decide to activate AMR + DTX on the whole network… their motivation will be, of course, “for improving speech quality and subscriber’s perception ”…
It would be much better just to remove all flags related to AMR + DTX from OMC-R so nobody has temptation to “optimize” voice quality with them :)))))) at last until the problem will be solved …. Please..:)
…oh, I would like to spend some hours outside drive-testing, but these days I’m spending much more time in office, analyzing other people’s logs..
Have a nice day!
Best regards, Lily24th March 2010 at 16:07 #598802112Guest
We have already tried DTX deactivation for AMR and it really improves DL Interfernce HOs but problem is disabling DTX had a very clear impact on Handover Success Rate and significant degrdation was observed in Drop Call Rate due to increase in Handover Failure Rate,So we decided to keep the DTX enabled.
We havn’t observed any degradation in DTs or from customer complaints infact cluster level DL Quality Samples Distribution is showing no degradation and improvement of DL Interference HOs with disabling DTX does prove the “inaccurate measurement by MS” Theory a little more logical.26th March 2010 at 20:24 #59881lilyGuest
Thank you very much for information.
Next week I can share our results.
Lily27th April 2010 at 19:39 #59882JuniorGuest
Have you got any results?
J.24th June 2010 at 18:15 #59883ALUGuest
I am new to this Forum and googled “DTX with AMR” and landed up over here :P…Very Informative Discussion, i must say.
In my Network(Vendor Alcatel-B10), DTX(DL/UL)is totally disabled for AMR.I had heard earlier that its not advisable to implement DTX with AMR.Currently we are under a lot of pressure from customer and concentrating on improving the Call Drop Rate.So,keeping all the discussion into consideration, do u prefer enabling DTX with AMR(for CDR improvement) or should i avoid that for the risk of degradation of End user Perception + increase in Quality/Interference HO’s?
Thank you for you expert opinion.24th June 2010 at 18:42 #59884PixGuest
I take it you work within ALU ?
If I were in your position, I would try to activate AMR + DL DTX on few cells only, then AMR + UL DTX on few cells, and then AMR + DL DTX + UL DTX. The problem might be already fixed in your release ?
For each trial, wait only 2 or 3 hours. If there is a degradation, you should quickly see it in NPO : high HO QUAL and high HO INTERFERENCE.
To decrease the Call Drop w/ AMR, have you tried tuning the RadioLink TimeOut AMR and radiolinktimeout AMR_BS ? Also, you can change the thresholds for AMR codec change and channel change, along with the averaging window.
pix25th June 2010 at 16:27 #59885ALUGuest
Yeah i work for ALU(wasn’t too hard 2 guess, right :P).
Thanx for your suggestions.We have already set RadioLink TimeOut AMR and radiolinktimeout AMR_BS to max(32) as initially when we implemented AMR, it caused increase in Call Drop which got fine after changing RLT for AMR.I will try to enable it one by one as suggested by you.I have heard that its not advisable to enable DTX on HR??whats your take on that? As you know that in Alcatel we have separate set of parameters for enabling DTX for HR/FR so,if that is the case i can only enable it for FR?
Also bringing improvement in DCR by codec mode adaptation, you suggest to tune parameters in such a way as to use more robust codecs for HR/FR?25th June 2010 at 18:05 #59886PixGuest
There used to be a problem in the past between DTX and HR. But this is long gone. So yeah, you could also try it. I doubt you’ll see any damage in the voice quality.
Once again I repeat : when you enable DTX, you will probably see better KPI. But beware of the voice quality ! That can only be assessed with your ears or some VQ tools.
Regarding AMR codec tuning, here again, I can’t tell you how to tune them… Test and learn… (I never tried myself). As you understood, the robust AMR Codecs are not so useful because the drop will happen anyway. Therefore it is really difficult to imagine how changing the codec thresholds would impact the KPIs.
pix12th July 2010 at 20:36 #59887ALUGuest
Hey pix..sorry for the late reply.actually i was on leave so couldn’t reply earlier.I just want to share some interesting findings with you.I enabled DTX with AMR(DL-FR/DL-HR/UL-FR) in my network and quite surprisingly , no degradation observed in Quality Handovers whatsoever!!! The AMR Interference handovers are disabled so ofcourse no degradation for them either 😛
Infact Quality handovers have reduced sightly.This leads me to the conclusion that maybe in the new Versions of the Software, there is no problem of increase in Quality/Interference Handovers when using AMR +DTX + ALU 😉
I remember even the B-10 Migration Expert telling us not to enable both DTX and AMR at the same time as it causes degradation in terms of Quality/Interference HOs 🙂
P.S: I tried ur email id but got Delivery Notification Failure 😛