Power allocation for uplink non-orthogonal multiple access in 5G

Interleave division multiple access (IDMA) is a nonorthogonal multiple access (NOMA) scheme for the uplink that allows several users with different interleavers to transmit in the same channel. In this paper the issue of power allocation in IDMA is analyzed and an algorithm for optimal power allocation is introduced. The advantage of this algorithm is that it determines the optimal power allocation from information theory point of view with low computational cost. Furthermore, based on the optimal power allocation the maximum number of users that can use the same channel is determined. In the end, some numerical evaluations are presented to show the performance of IDMA with optimal power allocation in various circumstances. Throughout the paper, the turbo code scheme that is used in LTE is considered as the error correction code of IDMA. It is shown that with power optimization, IDMA can accommodate more users in the same channel while retaining a minimum required SNR for all users, thus increase the capacity and channel utilization.