- This topic has 8 replies, 1 voice, and was last updated 9 years, 7 months ago by pix.
28th July 2011 at 08:41 #66856SmartGuest
How can I perform a AMR codec measurement and optimization?
What AMR speech codec are you using for AMR-FR and AMR-HR?
Regards29th July 2011 at 09:21 #66857HauiuGuest
We use 12.2, 10.2, 7.95 and 5.90Kbps for both AMR-FR and AMR-HR. AMR defines the proper bit rate according to the radio environment (interference), FR-HR is related to resources at BTS.29th July 2011 at 09:25 #66858HauiuGuest
AMR_12.20 12.20 FR
AMR_10.20 10.20 FR
AMR_7.95 7.95 FR/HR
AMR_7.40 7.40 FR/HR
AMR_6.70 6.70 FR/HR
AMR_5.90 5.90 FR/HR
AMR_5.15 5.15 FR/HR
AMR_4.75 4.75 FR/HR
AMR_SID 1.80 FR/HR
I was wrong at the first sentence.
12.20 and 10.20 bit rates are used in FR only.29th July 2011 at 11:59 #66859SmartGuest
How you decided on what to use. or you are using default parameters?29th July 2011 at 12:45 #66860HauiuGuest
If your vendor equipment support all of them, it is OK. If not, you will have to choose according to your radio environment. Higher interference-Lower bit rate.4th August 2011 at 16:36 #66861DellGuest
when we use 4.75 codec for both FR and HR there’s more bad frames in percentage than the case with 5.90. Is that mean that 5.90 is better? As I know 4.75 is more robust codec. And why such a high number of bad frames in 4.75? Is that meaning that frames are bad because of 4.75 or 4.75 is used because of low C/I and many bad frames?
Anyone explain please!
Dell5th August 2011 at 13:35 #66862HauiuGuest
In case there are errors in the frame, then these errors are fixed by using error correction bits. If the decoder fails to correct these errors, then you have a bad frame. In order to lower the number of bad frames (lower the Frame Error Ratio), we increase the error correction bits, and this lowers the bit rate.
So using 4.75 bit rate you should have less bad frames then in 5.90 bit rate.7th August 2011 at 20:39 #66863DellGuest
thanks for the answer.
In our network in most of cells 4.75 has almost 50-50 bad-good frames. 5.90 and higher codecs have little bad frames. Is that mean that is something wrong with the system? We are using ALU B10. I know the solution is to disable 4.75 but wanted to know what can cause this.
Thanks again and best regards,
Dell8th August 2011 at 03:33 #66864pixGuest
you should try to disable 4.75
then you might see that it is now the next codec (5.9) which has lots of bad frames.
if that’s the case, it means that either your C/I thresholds are wrong.
or it measn that there are some severly interefered zones in which even the most robust codec can’t fight.
keep in mind that the most robust codec is the one used in the WORST areas of your network, so you would expect to see the worst radio quality. Therefore, conduct a drive test in the worst cells, find out where the worst C/I are localised, and do an voice quality (in UL and in DL) to ensure the codec is unable to keep up with the interference. Try modifying the codecs to see the impact, etc.
If the experiment shows that 5.9 is showing less bad frames than 4.75, then it might mean there is an issue with 4.75. But it can also mean something else 🙂