- This topic has 9 replies, 1 voice, and was last updated 12 years, 9 months ago by pix.
8th July 2008 at 15:06 #53016MikeGuest
Any idea why there is a difference in % dropp rate of AMR and non AMR ?8th July 2008 at 21:01 #53017hmGuest
In general AMR codecs can operate at lower C/I values and allow an improved utilization of the frequency spectrum. The voice quality may not be the limiting factor anymore in AMR calls, but the performance of the signaling channels. To allow a higher utilization of the frequency spectrum 3GPP (Was it in Release7?) has adapted the idea of Repeated FAACH / SAACH. These are than also (optional) features for mobil stations.9th July 2008 at 07:51 #53018rf fanGuest
could you write more information about FACCH/SACCH repetition ?
Thkanks !9th July 2008 at 09:31 #53019MikeGuest
But % drop rate is on radio link loss on signalling on SACCH which is not changed by AMR so why the difference ??9th July 2008 at 20:21 #53020rf fanGuest
Because users don’t interput the call by himself – they have good voice quality in bad radio conditions ….15th July 2008 at 05:35 #53021GTNF5Guest
Anyone know which are the key indicators for traffic statistic to show before and after effects of AMR?
Which are the indicators we use for graph presentation on AMR and bit rates?18th July 2008 at 07:32 #53022MikeGuest
Let me put this way, SACCH is not modified by AMR, so if the radio link is good/bad radio link time out on SACCH would be same as it was before. I can understand it gives an improved speech performance with AMR, but why is the Drop Call rate different than Non AMR circuits.
Mikee18th July 2008 at 08:33 #53023pixGuest
RF Fan gave you the answer : the “AMR” subscriber does not disconnect the call while in bad radio conditions. The radio is bad, but the voice is good –> the subscriber is happy and keeps talking. Unfortunately the SACCH are lost, and the call drop will eventually occur anyway.
With non AMR, the subscriber will hang up the call before the BSS could detect a call drop.
Therefore, non-AMR CDR < AMR CDR.18th July 2008 at 14:03 #53024MikeGuest
Thanks for your clarifications. But…
a) Normal DISCs are not part of CDR.
b) Lets say at a distance from the BTS, SACCH will fail at regardless of whether AMR/NonAMR codec. (Though I know the user will have better voice quaility with AMR codec).
c) So the user drops it due to radio problems on SACCH anyhow and so the CDR (regardless of whatever speech codec he was on).
Theoretically CDR should be same.
I appreciate everyone’s patience so far.18th July 2008 at 18:19 #53025pixGuest
in a cell, let’s assume :
one week without AMR : “X” call drops, “Y” disconnections
next week with AMR : “X+d” call drops, “Y-d” disconnections
people prefers to disconnect a call as soon as there is no more voice (case of non AMR calls under poor radio conditions)
when you activate AMR, the ppl will feel the voice is fine, but the BSS feels otherwise, because the SACCH are lost.
if you still don’t understand, i’m not sure i can do anything more 🙂 Read few more times…