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Erlang Formula

Viewing 15 posts - 151 through 165 (of 181 total)
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  • #33012

    Hi Telecom,

    Can e n one tell me Why 1 Hz frequency tranmit one bit only without error ???

    waiting 4 yr reply plz reply ASAP.


    is there a web page or standard with the earlang of pabx


    Hi osprey,
    I see you still have doubts about RxQual Sub vs Full and RxQual vs SQI.

    Sub vs Full values (this applies not only to RxQual, but to RxLev and FER):

    GSM can use discontinuous transmission (DTX) – when there is no sound to transmit, the phone and/or the BTS may not transmit all frames on the timeslot. This means that when you have DTX the RF signal is not present on the whole timeslot. So, when DTX is active and was used (it may be enabled, but not used in specific instants if you “speak too much ;-)) the RxLev and RxQual measured across the whole timeslot period will be meaningless. For this situation, there are measurements of RxLev and RxQual which are taken only on the obligatory frames (not on the actual tranmitted frames, which would complicate matters). These are the “Sub” values.

    So “Sub” values are always valid, but may not be as precise as Full values, whereas Full values are more precise, but may be wrong when you have DTX. The network and the phone “know” when to consider the Sub or the Full values for handover decisions because there’s a “DTX was used” flag transmitted.

    SQI vs RxQual:

    RxQual is part of the GSM standard (05.08), and it is used basically for handover/power control. It is directly related to Bit Error Rate (there is a table on the standard). For each BER range, am RxQual value from 0 to 7 is used.

    SQI, as Erik has pointed out, is more true to the actual user experience in terms of voice quality. RxQual alone is not a direct estimative of voice quality because:
    – it does not take into account FER and CRC (you may have bad bits spread on different frames, which are corrected by the redundancy protection with no impact on the voice, or all on the same frame, which will cause the frame to be discarded, impacting the voice quality)
    – it does not take into account the vocoder in use (even with RxQual and BER = 0, a half rate vocoder won’t give you the voice quality of an enhanced full rate vocoder, and for AMR it will depend on the percentage of bit rate used for each instant)
    – it does not take into account the handovers (if you have lots of handovers, voice quality will drop even if RxQual is good – Ok, generally with good RxQual, there will be no handovers, but…)

    SQI takes all these factors into account and also their statistical distribution (isolated FER occurences may have little or no impact on voice, for example), and has a very high correlation with actual human scoring of voice quality (better than 90%).

    Summarizing, RxQual is more an RF quality paramenter, and SQI is a voice quality parameter.

    Check this:
    from question 12 to 25. It has good information about SQI.


    Joao S Veiga


    sorry, your question was RxQual vs RxQual %, not Full vs Sub…

    The RxQual defined on the GSM standard 05.08 is not in %. It is a value from 0 to 7, corresponding to BER ranges.

    I suppose the RxQual %, since it is not a standard-defined parameter, may or not have different definitions on different measurement systems, but for Ericsson TEMS Investigation, it means the bit error rate corresponding to the RxQual (number) reported. For this system, the % values range from 0 to 26%, and the (number) values from 0 to 7, and their relationship is as defined on GS 05.08.


    Joao S Veiga


    Hi Joao,

    Did you have experience with very low SQI, when using half rate codec with DTX in DL




    I have a question regarding the quality of a received signal in GSM. Do you have any idea what is prefered min level signal for a quality GSM data transfer? Is any recommandation to RxQal (1 – 7)? We have problems on the installed GSM devices. Thanks,



    i am looking for a way to calculate the number of circuits given the blocking probability with erlang b formula,could anyone help me please!!!
    my mail

    Saptarshi Ghatak

    What is earlang? How to measure Telephone call?

    Bijaya Kumar Mishra

    What do you mean by “MS Power vs Timing advance” analysis ?
    What message it conveys?

    Thanks for your answer.


    BKM, you mention “MS Power vs Timing advance analysis”. I think you must refer to some correlation between the power emitted by the mobile (when Power Control is activated) and the distance between the mobile and the antenna (which is measured by Timing Advance, each unit of TA being more or less 500 meters).
    In overall, you should find more or less the same as the formula used for calculating link balance… MSP – PL(d) + AG(a) = R
    MSP = minimum MS Power required
    PL = Path Loss (in absolute value)
    AG = Antenna Gain
    R = minimum Reception level accepted by your BTS
    a = angle of emission of the shortest signal beam reaching the mobile

    I’m not sure what you mean by asking the messages conveyed. TA is just a measure of distance. It is useful for synchronisation (which I think, but not 100% sure, should be only on the side of the MS)


    I would like to know details about location update in cell and what is LAC?

    Balamurali Ekambaram

    How to Calculate the Link load of a Signalling link? Also how many voice circuits does one Signalling link support?


    Carolyn, if you just “google” what you are looking for, you can find it. For example:

    In short, LAC (Location Area Code) is an identifier for a geographic area. Location updates are performed to let the network know where the mobile stations are in case of a MTC. If someone tries to call you, the network will send a “paging request” on the whole LAC where your mobile has last been registered, to try to contact you. Your mobile will then contact the network using a RACH to make the connection complete between the person calling you, the network, and yourself.

    I hope this helps…


    What we do in RF survey & Microwave survey, plz Differensiate


    I understand FER is a voice element more than RF element. Can high FER rate cause high call drops when RxQual andRxLev are good

Viewing 15 posts - 151 through 165 (of 181 total)
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