On Sufficient Condition for Power Allocation Range of BER for M- User NOMA

Recently, the bit-error rate (BER) for non-orthogonal multiple access (NOMA) with M - user has been derived. However, the ranges of the power allocation coefficients, for which the BER expression holds, are provided as a necessary condition. In this letter, the authors derive a sufficient condition for the power allocation ranges for the BER expression. Such ranges are significant, for each user to avoid the severe performance degradation. In result, the user fairness could be established with the power allocation within the derived ranges.