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GSM 200 kHZ bandwidth

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  • #56487 Reply
    RFOptimizer
    Guest

    Hey All, my question is: why is the bandwidth for a single GSM channel equal to 200 kHz? Why couldnt it have been more or less? What are the factors that govern this?

    Thanks/

    #56488 Reply
    Pix
    Guest

    Hello,

    One channel is separated by 200kHz from its adjacent channel. The carrier itself has a very precise frequency. I don’t really like the term “bandwidth” in GSM, when talking about frequency, but that’s just me.

    200kHz was chosen in order to provide enough room between channels to avoid interference – without the need of expensive filters in the TRX.

    #56489 Reply
    MKT
    Guest

    Interesting …….

    Why?

    We don’t know what was given to “them”.

    Whether 200KHz BW was given and “rest” are to be calculated?

    OR

    Whether the “rest” was GIVEN and MINIMUM BW needed is to be ANSWERED??

    Regards

    MKT

    “rest”= Selection of Speech codecs, Bit Rate at Air interface etc..

    “Them”= ETSI

    #56490 Reply
    sabah
    Guest

    silent call

    we have silent call in some sites please we need to now the real reason for it

    #56491 Reply
    Ds
    Guest

    Hi Pix,

    thanks for the ans.
    in my opinion,requirement of expensive filters would have come later.
    initially y 200khz was choosen, must have some other ans/technical calculation.

    #56492 Reply
    paraHO
    Guest

    The question about TDMA surely as GSM adopted it.

    TDMA uses 200 kHz per radio channel in comparison to analogue cellular allocations btw 12.5 kHz – 30 kHz. TDMA reduces the allocation each traffic channel to 200 kHz / 8 = 25 kHz, roughly equal to typical analogue system. This perhaps tell us TMDA lloked to some quality and features over simply increased capacity. I suppose to put use the same approach for use for analogue systems would require significant increase bandwidth for analogue systems making it inefficient to operate maybe?

    GSM as I seem to remember want ‘efficency’ as spec’d at the outset to prove digital communications introduced an enhanced pan-european digital service over localised and diverse analogue systems.

    Quality those has its price. TDMA structure gives more capacity (when compare with analogue). MS burst every 4.615ms has underlying freq 216.6 Hz (1/4615ms) which is an audible range and frequency can be heard on radio/music system speakers etc – so risks and nuisances need to be designed out but costs to do that.

    BR

    #56493 Reply
    prashant gaur
    Guest

    How we calculate the erlang?

    #56494 Reply
    KIRAN
    Guest

    GSM system uses 200 KHz BW for each carrier. The target SNR at cell
    edge is 5 dB (for voice delivery). Find the cell radius for the case when BS
    transmitter power Pt = 10 watts for LOS and non-LOS cases, respectively.
    Assume ht = 10m and hr = 1:5m, fc = 800MHz.

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