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BER-FER-RxQual

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  • #56411 Reply
    RF_Man
    Guest

    Dear All
    I confuse these parameters (FER, BER, RxQual)

    Someone can explain in a simple way mentioned par.?

    1. I know RxQual is quality is received signal. But what is relationship between BER & RxQual????

    2. FER= Frame Erasure Rate???

    I mean all of them in TEMS.

    Thanks:….

    #56412 Reply
    Pix
    Guest

    RXQual and BER are related. The RXQual is just a certain scale, and each RxQual correponds to a certain amount of BER.

    FER is when a speech frame is erased by the TRX, because it couldn’t be decoded properly.
    Usually, at low BER, the FER is good, but if BER degrades, then FER suddenly becomes bad.
    It’s because the TRX could re-build radio blocks into a proper frame even when there is a bit of BER. This is thanks to convolutional coding.
    But that works up to a certain BER.

    Regards,
    Pix

    #56413 Reply
    TNS
    Guest

    Hi,all

    The BER (RxQual) is function of the radio freq propagation in specific space conditions ( in all aspects )

    The FER is function of the BER value and the speech codec used.

    BR,

    #56414 Reply
    venu byna
    Guest

    what is solution for Rxqual,Rxlel,SQI are bad
    and FER,BER,C/I,C/A,interference problems
    tell me solution of this problems in drive test and optimization

    #56415 Reply
    Somesh Nandi
    Guest

    Why We use rx level full in idle mode and rx qual sub in ded mode????

    #56416 Reply
    Rocel
    Guest

    Because:

    RxLev Full – when DTX is not used

    RxLev Sub – when DTX is used if no voice is not transmitted in this direction.

    This feature should be enabled in the cell if we want to use DTX. DTX is used for reduce interference, to save phone battery.

    #56417 Reply
    Paola
    Guest

    Hi,
    How is it possible to measure RxQual?
    I know RxQual is linked to BER, maybe I have to measure BER, isn’t it?

    #56418 Reply
    blert
    Guest

    You can only really measure the RXQUAL through a drive test (thats the most normal way at least).

    As said before there are two lots of RXQUAL to measure. If you’re in dedicated mode and your network uses DTX then all measurements should be RXQUALS. (RXQUALF will still give a measurement but will almost always show a poorer result so should be ignored). The same applies to RXLEV measurements.

    Normal measurements for RXQUAL are 0-5 are good call quality, 6-7 is poor quality, and should trigger handover selection if possible, if not the speech becomes unintelligible and dropped calls may occur.

    Also as mentioned, the BER is the method for the measurements. The RXQUAL is just a scale given to ranges of the BER to simplify measurements.

    FER is a a measurement of how the codec is decoding the frames. As the radio conditions worsen, more errors are introduced and the ability of the TRX to rebuild the frame obviously reduces. Hence the FER rises. Normally, unlike the BER/RXQUAL the FER tends to shift quite quickly.

    All 3 should be looked at in conjunction with RXLEV to make a reasonable assumption about the conditions of the call at the time.

    #56419 Reply
    2112
    Guest

    You need to have good Idea of SACCH Multiframe and speech coding to understand fully these concpets of BER, RXQUAL, FER, DTX and SUB and FULL values.
    SACCH Multiframe consists of 4 26 frames containf 24 speech/data bursts and 1 SACCH and 1 Idle timeslots.

    so there are total 96 timeslots for speech, 4 timeslots for each SACCH and IDLE.

    Full measurements are made over the complete SACCH Multiframe while SUB Measurements are made over the mandatory timeslots that is SACCH and SID (Silence Discriptor).
    When DL DTX is being used no need to worry about Full values and just check the SUB values for FER and RXQUAL.

    each 20msec speech is coded into 240bits and is divided into three categories accordint to their importance
    Calss 1a = 50bits (Most impotant)
    Class 1b=132 bits (Less important)
    and class2=78bits (no impotance and are not used in BER Calculation)
    3 CRC bits are attached with Class 1a 50 bits and then these 53 bits along with 132 bits of class 1b and 4 tail bits a total of 189 are 1/2 convolutionally coded.
    This coding doubles the number of bits to 378 and these 378 bits are used for BER calculation out of total 456 bits excluding class 2 bits 78 bits.

    #56420 Reply
    2112
    Guest

    Complete Frame is discarded when CRC check fails over Class 1a 50 bits.So this is FER while BER is calculated over complete 378 bits of speech block as each 26 multifram contain 6 speech blocks and there are 4 26 multiframes ao there are total of 4*6*378 bits being tranmitted over 1 complete SACCH Multifram and these are used for BER calcualtion and BER is simply rate of erroneous bits out of these total 4*6*378 bits.

    So hopefully this explains the BER and FER and their corelation.

    #56421 Reply
    pix
    Guest

    2112,
    Excellent info, i didn’t know that, thank you !

    Blert,
    Excellent too, thanks 🙂

    #56422 Reply
    R-chie
    Guest

    Guys,

    High FER and Bad Quality. There are times also that Rxlev is affected if bad quality occur.

    Is there a way to solve this? What could be causing it.

    We have notice that the site and its neighbors bts power increase too not like before.

    could it be over-shooting??

    #56423 Reply
    Mak
    Guest

    Why the Value to ARLT is more than RLT in the network

    #56424 Reply
    BHT
    Guest

    I was confused over RXqual,BER,FER for a long time.
    I would like to thank blert & 2112 for clearing things up.

    #56425 Reply
    NIKHIL CHANDERI
    Guest

    Hi, i wanna know why RxQual value for best quality is 0 and for poor is 7?

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