Power allocation in NOMA

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  • #12582
    Hasyimah
    Participant

    Good day,

    I would like to know, where can I find coding in the NOMA scenario which shows the power allocation to each UE in the simulation?

    #12586
    Bashar Tahir
    Participant

    Hello,

    The power allocation follows the LTE Rel. 14 specs: http://www.3gpp.org/ftp//Specs/archive/36_series/36.211/36211-eb0.zip
    On page 147 “7 Generic functions”. For each QAM mapping of the cell-center user, three power ratios are defined. Each is controlled by the two parameters ‘c’ and ‘d’. The superposition is defined as follows:

    x = exp(j*phi0*pi)*c*(I-d) + exp(j*(phi1+0.5)*pi)*c*(Q-d), where

    – phi0 is the inphase component of the QPSK symbol of the cell-edge user,
    – phi1 is the quadrature component of the QPSK symbol of the cell-edge user,
    – I is the inphase component of the M-QAM symbol of the cell-center user,
    – Q is the quadrature component of the M-QAM symbol of the cell-center user.

    The resultant composite constellation is Gray-coded.

    Based on that, we can deduce that the power allocation to the cell-center user is c^2; it follows that the cell-edge user has a power allocation of 1-c^2. This is assuming that the total power is 1.

    In the simulator, you find those parameters in +Modulation\SignalConstellation.m @ line 37, and @ line 97 you see how they are applied. If you want to change which power ratio is chosen during the simulation, you can do so in +Elements/Link.m @ line 261.

    Best regards,
    Bashar

    • This reply was modified 1 year, 9 months ago by Bashar Tahir.
    #14807
    Hasyimah
    Participant

    Since NOMA is pairing a cell-center with a cell-edge user. Which c value is in consideration of the power ratio calculation let say we are considering MUSTIdx = 2. Is it QPSK or QAM? And if it is QAM, which QAM order come first if I consider scStr.modulation.cqiTable = 0 ?

    Another question. What UE values considering for type of modulation: QPSK, M-QAM? Is it based on the pair or is it based on the PL values being set or any other?

    #14814
    Bashar Tahir
    Participant

    Hi,

    The cell-edge user is restricted to 4-QAM (QPSK), while the cell-center user can be 4-QAM, 16-QAM, or 64-QAM.

    The choice of c and d depends the modulation combination (4-QAM with 4-QAM, 4-QAM with 16-QAM, etc) and the MUSTIdx. Those can be found in the standardization link I posted above (on page 147 “7 Generic functions”). For each combination, you can find a table that specifies the values for c and d.

    Best,
    Bashar

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