Abstract
A hybrid or coexisting orthogonal frequency-division multiple access (OFDMA) and nonorthogonal multiple access (NOMA) scheme is a promising approach to greatly enhance network capacity and reduce the interference in machine-to-machine (M2M) communication networks. In this article, we study the power allocation and access mode selection problem of machine-type communication devices (MTCDs), which are allowed to transmit their data packets to the base station (BS) in direct transmission mode (DTM) or cluster head forwarding mode (CHFM). Considering the transmit power optimization and data rate maximization of the MTCDs, we formulate the power allocation and access mode selection problem as a sum-rate maximization problem. Since the original maximization problem is a nonlinear fractional problem that cannot be solved conveniently, we transform the optimization problem into two subproblems, i.e., power allocation subproblem and access mode selection subproblem. The power allocation subproblem is solved for both OFDMA and NOMA schemes by applying the Lagrange dual method. To solve the access mode selection subproblem, we further divide the subproblem into DTM subproblem and CHFM subproblem and solve these subproblems successively. In particular, for the solution of the CHFM subproblem, we first propose a greedy method-based algorithm, and then, to tackle the issue of high computational complexity, we present a low complexity heuristic algorithm. In the end, we present simulation results to demonstrate the effectiveness of the proposed algorithms.
Published Version
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