Resource allocation for NOMA based D2D underlaid cellular networks

This paper puts forward a user clustering and power allocation algorithm for non-orthogonal multiple access (NOMA) based device-to-device (D2D) cellular system. Firstly, an optimization problem aimed at maximizing the sum-rate of the system is constructed. Since the optimization problem is a mixed-integer non-convex optimization, it is decomposed into two subproblems, namely user clustering and power allocation subproblem. In the subproblem of user clustering, the clustering algorithms of cellular user and D2D pair are proposed respectively. In the power allocation subproblem, the gradient assisted binary search (GABS) algorithm and logarithmic approximation in successive convex approximation (SCA) are used to optimize the power of subchannel (SC) and D2D transmitted power respectively. Finally, an efficient joint iterative algorithm is proposed for the original mixed inter non-convex non-deterministic polynomial (NP)-hard problem. The simulation results show that the proposed algorithm can effectively improve the total system rate and the larger the ratio of cellular users (CUs) to total users, the larger the total system rate.