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TCH Drop related with TX Power

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  • #67985 Reply
    eorenmh
    Guest

    Dear fellow telco engineers,

    kindly need your advice on my Siemens network that currently having high TCH Drop Call Rate.
    I have suspect on interference issue related with TX Power.
    What can i do with this to adjust any parameters related?

    thank you in advance

    #67986 Reply
    pix
    Guest

    hello,

    to reduce intereferences caused by an excessive tx power, you should activate the Power Control in UL and in DL.
    If both directions are already activated, then you should fine-tune the thresholds, averaging windows and power step sizes in order to make it more “aggressive” (= more “efficient”).

    Best Regards,
    Pix

    #67987 Reply
    eorenmh
    Guest

    dear pix,

    thank you much for your reply

    i wonder what is the relation between power and interference?
    perhaps if power is full, then the interference would be bad? or the opposite?

    and what is difference between UL power and DL power?
    if im not mistaken, DL is from BTS into MS, and UL is from MS to BTS, is that correct?

    thank you again in advance 🙂

    #67988 Reply
    pix
    Guest

    power => the device transmits more power. As a result, this signal is stronger and will interfer with the signals which are sent by other devices.

    in UL : transmitter = MS, receiver = BTS
    in DL : transmitter = BTS, receiver = MS

    UL power is power used by the MS to send a signal to the BTS.
    DL power is the power used by the BTS to send a signal to the MS.

    I one MS sends a strong signal, then it might interfer with other mobiles located in other cells which are using the same frequencies.

    regards
    pix

    #67989 Reply
    VanG
    Guest

    Hi Pix,
    please advise me how to tune my parameters to make more agressive power control to improve the DL quality? What are the optimal value for PC thresholds, averaging windows and power step sizes ?
    Thank you in advance,
    Best regards.

    #67990 Reply
    Vim
    Guest

    Hi Pix,

    Can you please explore the the term “TCH Drop due to Radio Fail” and “TCH Drop due to Abis Fail”.
    In My Network Many sites are having high abis fail but i found and checked that there is no issue with the Transmission end.

    What we need to do to rectify this issue and improve the DCR KPI.

    Thx

    Vimal

    #67991 Reply
    Dell
    Guest

    Hi,
    Is the param bs_txpwr_min important in power control?
    Regards,
    Dell

    #67992 Reply
    pix
    Guest

    dell,

    not really, as long as it is greater than 10dB. The most useful power backoff is in the 1st dBs. Reducing the power by 3dB goes a long way for the network. When PC is reducing power by 10dB, then it means the cell is not interfering with anyone anymore, for sure.
    Going beyond that is required when you have tight frequency planning, or to further improve “noise”. That’s especially useful for EGPRS transfers.

    a typical BS PWR MIN is around 14dB.

    Going too low might slow down HO detection, and might make the radio link very sensitive to any little change.

    #67993 Reply
    Dell
    Guest

    Thanks Pix,
    in some cells (dcs1800, not multiband) bs_txpwr_attenuation is 2 dB, but, bs_txpwr_min is -10 dB. In gsm900 cells that difference between max power and min power is 10 dB (if attenuation is 2 dB, bs_txpwr_min is -12 dB in gsm900). Should we decrease bs_txpwr_min to -12 dB as well in dcs1800 for txpwr_attenuation of 2 dB? Vendor is ALU release B11.
    Regards,
    Dell

    #67994 Reply
    pix
    Guest

    hi,

    what you should ask is “what is the purpose of “bts pwr min”…?”

    – this is the maximum attenuation that can be applied to the signal with power control.

    there is no correlation with the bts pwr attenuation, which is the “minimum attenuation” (which allows to compute the max power) on the cell. When pwr reaches this value, it means the cell is transmitting at max power. Max power is used at call setup, just after a HO, or when rxlev/rxqual are poor and PC will push the power to the max to save the call.
    Also, this max power is used by EGPRS transfers.

    regards
    pix

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