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variable or fix power change (AMR)

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  • #66688 Reply

    Hi all,

    Any idea on using variable or fix power change step size in case of a network with AMR feature activated?

    I am trying to understand if the usage of variable power control is improving AMR usage compared to normal power control! Please advice.

    How is the network affected in both cases?

    thanks in advance


    #66689 Reply

    Any suggestion?

    #66690 Reply


    I don’t think PC would have a different effect between AMR or legacy codecs. The step sizes and factors should be the same… The thresholds are different.

    Now, you could take into acocunt that AMR is more resistant, so you don’t need to have the PC tuned as reactive as when used with Legacy codecs. This is where you have to do trials… though I doubt you’d find much improvements.


    #66691 Reply

    Dear Pix,

    For the moment we are using fix power change step size, but in which cases is recommended to use variable step size? Is it true that the power control can happen only in intervals of 480 ms, in both cases?


    #66692 Reply

    yes, the power commands are sent at the SACCH interval, every 480ms.

    the variable or fix step size refer to the amount of power that cn be increased or reduced.
    If UL RXLEV is very high, then the BSC will tell the MS to reduce its TX Power:
    – if fixed step : power is reduced at a rate of “n” dB every 480ms. Usually, n = 2dB. so it takes 5 seconds to decrease power by 10 dB.

    – if variable step : power is reduced by “k” * (rxlev_target – rxlev_measured)
    k is usually between 0.6 and 1.
    So it takes usually 1 or 2 SACCH to reach the desired power.


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