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reduce the inference in GSM network

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  • #47121 Reply
    laye
    Guest

    Hello,
    I am a new engineer telecom.
    Could you tell me what are all the actions to be taken to reduce inference in GSM network?

    #47122 Reply
    belal- Adeed Company
    Guest

    Sources of Interference
    Re-use of (own) frequencies
    Multipath components (long echoes)
    External interferences

    Interference Reduction Methods
    1- Power control
    2- Discontinuous tx (DTX)
    3- Frequency hopping*
    4- Adaptive antennas
    5- Dynamic Channel Allocation
    6- Good frequency plan
    7- Antennas:
    (down-)tilting
    Beam width reduction orientation

    #47123 Reply
    pix
    Guest

    nazmul, posting your problem only once is usually good enough.

    #47124 Reply
    akefa
    Guest

    Belal,

    DTX means the transmission of bits stops during silence. As I know, the TCH is always emitted by the tower wether there are calls or not.

    Accounting DTX as one of the features that reduces the interference is same saying:
    The amount of interference in the air interface depends on the number of bits transmitted (number of calls). Is it??!

    If the answer is NO, then DTX has no hand in reducing the interference.

    #47125 Reply
    Pix
    Guest

    YES, less timeslots used in the iar means less probability of two timeslots from different MS’s or BTS’s using the same frequencies at the same time.

    The TCH is NOT ALWAYS EMITTED by the tower. It is always transmitted for the first TRX only (the BCCH TRX), ok. For other TRX’s, downlink DTX can be activated –> the timeslots will not be transmitted if there is no data to transmit.

    Pix

    #47126 Reply
    Vivek Kesharwani
    Guest

    Hello Dear….
    with reference to interference
    i would like to know
    1.Adaptive antennas
    2.Dynamic channel allocation and how it is different from Frequency hopping plz clear my concept

    #47127 Reply
    MKT
    Guest

    Then for what purpose the DUMMY BURST is there in GSM

    #47128 Reply
    pix
    Guest

    hello,

    there might be many usages for dummy bursts.. i don’t know all of them, so i’ll just give you what i can remember of :

    in GSM : during DTX, dummy bursts are sent in order to be able to measure the radio link and generate comfort noise.

    in GPRS : for R4 onwards mobiles, during the delayed UL TBF release extended phase, the MS will send dummy UL packets.

    in Location Services : in some positionning methods, the MS might have to send dummy bursts.

    #47129 Reply
    MKT
    Guest

    I have one one doubt regarding DTX.
    DTX means decreasing the power of the transmitter when there is no voice activity OR sending dummy burst for having comfort noise.

    Second thing is it sure that dummy burst is the only mean for generating comfort noise.

    Third how a PSTN number able to hear the comfort noise.

    #47130 Reply
    pix
    Guest

    hi mkt,

    1.
    if you activate DTX DL, the BTS stops sending normal burst on the assigned timeslot if there is no voice to transmit.
    if you activate DTX UL, the MS doesn’t send a normal burst on the assigned timeslot if there is no voice to send.
    Instead of sending a normal burst, a dummy burst will be sent (i don’t know how often i will be sent, i think it is less frequent than a normal burst… = not on every timeslot)

    2 & 3 : the exact solution shall be found in 3GPP… I don’t have time to look for it now though, but i’ll keep it in mind.

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