Throughput Maximization for Instantly Decodable Network Coded NOMA in Broadcast Communication Systems

Non-orthogonal multiple access (NOMA) is a promising transmission scheme employed at the physical layer to improve the spectral efficiency. In this paper, we develop a novel cross-layer approach by employing NOMA at the physical layer and instantly decodable network coding (IDNC) at the network layer in downlink cellular networks. Following this approach, two IDNC packets are selected for each transmission, with one designed for all receivers and the other designed only for the strong receivers which can employ successive interference cancellation (SIC). The IDNC packets selection, transmission rates adaption for the two IDNC packets, and NOMA power allocation are jointly considered to improve the throughput of the network. Given the intractability of the problem, we decouple it into two separate subproblems, the IDNC scheduling which jointly selects the IDNC packets and the transmission rates with the given NOMA power allocation, and the NOMA power allocation with the given IDNC scheduling. The IDNC scheduling can be reduced to a maximum weight clique problem, and two heuristic algorithms named as maximum weight vertex (MWV) search and maximum weight path based maximum weight vertex (MWP-MWV) search are developed to solve the first subproblem. An iterative function evaluation (IFE) approach is proposed to solve the second subproblem. Simulation results are presented to demonstrates the throughput gain of the proposed approach over the existing solutions.