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Speech Quality

Viewing 15 posts - 1 through 15 (of 27 total)
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  • 28th February 2008 at 04:29 #51221
    MKT
    Guest

    Hi,

    It is often said that HR decreases the speech quality. So, do the same principal of speech quality 0-7 hold good for HR also. I mean do we have a
    different scale for HR w.r.t. speech quality.

    Regards

    28th February 2008 at 05:10 #51222
    Bilal
    Guest

    RXQUAL(0-7) is not the measure of “speech quality” instead it is the measure of Received Signal Quality and it is calculated from BER(Bit Error Rate). Speech quality is measured differently by different systems e.g. TEMS SQI, MOS, SQI in stats and it is calculated from FER(frame erasure rate) and several other factors. RXQUAL doesn’t depend on the speech codec used. But SQI definitely depends on the codec. You can say HR gives worse speech quality than FR and EFR at same RXQUAL. So, there is no point of having different RXQUAL scale for different speech codecs.

    28th February 2008 at 07:19 #51223
    MKT
    Guest

    So,

    SQI depends on FER
    and
    RXQUAL depends on BER.

    Is there any equation between SQI and RXQUAL?
    If No, then should a poor RXQUAL be a cause of worry.
    If yes, then what can be done to improve RXQUAL to finally improve SQI.Or what can be the causes of poor BER(thus poor RXQUAL).

    Also, What is the scale or range for SQI from worst to good?

    Regards

    28th February 2008 at 07:46 #51224
    Pix
    Guest

    There is a correlation between FER and BER, which is empirical. It is noted that :

    with No Hopping, an acceptable voice quality (FER) occurs when RXQUAL is below 4 (BER).

    With Hopping, acceptable VQ occurs when RXQUAL below 5.

    The SQI is between 0 and 30, or something like this. It is well explained in the TEMS user guide.

    30 is very good, and 0 is really poor 🙂

    2nd March 2008 at 17:47 #51225
    akefa
    Guest

    Is there any equation between SQI and RXQUAL?
    – Rxqual affects SQI but the opposite is wrong

    If No, then should a poor RXQUAL be a cause of worry.
    -yes if the coding doesnt not coevr this poorness.

    If yes, then what can be done to improve RXQUAL to finally improve SQI.Or what can be the causes of poor BER(thus poor RXQUAL)
    -interference

    3rd March 2008 at 09:19 #51226
    lvin
    Guest

    hi every body…
    who can help me for this problem?
    -whats the reason of handover revision?

    3rd March 2008 at 15:53 #51227
    pix
    Guest

    i’ve never heard about handover revision in GSM, nor UMTS.

    3rd March 2008 at 19:59 #51228
    akefa
    Guest

    handover revision, I think he means the case in which the mobile fails to handover to another cell and thus stays in the current serving one.

    4th March 2008 at 09:32 #51229
    lvin
    Guest

    hi pix..
    we have five type of handover in our system GSM:
    1.handover success.
    2.handover failure.
    3.handover attempt.
    4.handover ping-pong.
    5.handover revision.
    the great problem is handover revision.i think this occure if we have long distance between two cells.

    4th March 2008 at 12:23 #51230
    Bilal
    Guest

    I think he means to say “handover reversion” i.e. reversion to old channel after failed HO attempt. The question can be re-phrased as: What are the reasons of poor HSR? 🙂

    4th March 2008 at 13:50 #51231
    pix
    Guest

    hhaaa.. i’m so blur.

    HO Reversion to Old Channel, aka “ROC”

    R.O.C. is not a bad thing really : it just means that your HO was attempted towards the target cell, but for some reason it was failed (poor radio in target cell or hardware problem, probably).
    Then the MS manages to roll back to the previous serving cell and get back to its old TCH channel.

    Beware : congestion in target cell will not lead to ROC : the HO is not yet attempted. The failure occurs before the attempt.

    As a conclusion, I would say that your HO are triggered too early, and towards bad target cells (poor radio condition).

    4th March 2008 at 15:53 #51232
    Bilal
    Guest

    Although Reversion to old channel doesn’t lead to very bad subscriber perception like a call drop but still it is a handover failure. Handover is mostly triggered when there is urgency condition in source cell or target cell is better than source cell. And if the MS fails to complete the handover, this is not a good sign for the network.

    7th March 2008 at 12:36 #51233
    Amkam
    Guest

    SQI Vs. RxQUAL.

    SQI: estimates the speech quality in cellualr networks as pereceived by human listener , the SQI includes :
    1-BER
    2-FER
    3- HO data events
    4- the distribution of BER over time
    5- the speech codes been used

    RxQual: is obtianed by transfering the BER into scale value ( 0-7 ).( only take the average BER

    drawback :
    1- doesn’t include the distribution of BER over time
    2- NO mention Of FER
    3- frames lost during HO
    4- the choise of speech codec

    7th March 2008 at 14:43 #51234
    pix
    Guest

    thanks amkam
    SQI is definitely a better estimation of the voice quality than the RxQual, but it clearly doesn’t replace a subjective test (yet).

    12th March 2008 at 04:18 #51235
    Prima
    Guest

    hi guys, pls help me…
    -i found good RxQual (less than 1)but worse SQI=speech quality index (less than 21), how can that be?

    -is that connected with speech codec?

    -what is the differences and advantages of AMR, EFR, Half rate and Full rate for GSM Network

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