Optimal Resource Allocation for D2D Multicast Communications for XL-MIMO Systems

To improve spectral efficiency of Device-to-Device multicast (D2DM) communication, we study the joint optimization of subcarrier and power allocation in D2DM communications underlaying cellular system with extremel large-scale multi-input-multi-output (XL-MIMO) in this paper. Specifically, we aim to maximize the aggregate multicast data rate of all D2D groups (DGs) while guaranteeing the data rate requirements of CUs, where each subcarrier can be allocated to multiple DGs and each DG can reuse multiple subcarriers. This formulated problem leads to mixed integer non-linear programming (MINLP), which is usually NP-hard and computationally intractable. Therefore, we decompose it into two sub-problems, i.e., subcarrier assignment and power allocation. we design a heuristic subcarrier assignment scheme for allocating subcarriers to CUs and DGs by equally distributing the transmit power of CUs and DGs over all subcarriers. After that, we design an effective power allocation algorithm by adopting the "difference of two concave functions" (D.C.) programming to transform the nonconcave functions into concave ones. Extensive simulations and numerical results demonstrate that our joint resource allocation algorithms outperform the other baseline methods.