The cellular network coexisting with device-to-device (D2D) communications has been studied extensively. Reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) are promising technologies for the evolution of 5G, 6G and beyond. Besides, sparse code multiple access (SCMA) is considered suitable for next-generation wireless network in code-domain NOMA. In this paper, we consider the RIS-aided uplink SCMA cellular network simultaneously with D2D users. We formulate the optimization problem which aims to maximize the cellular sum-rate by jointly designing D2D users resource block (RB) association, the transmitted power for both cellular users and D2D users, and the phase shifts at the RIS. The power limitation and users communication requirements are considered. The problem is non-convex, and it is challenging to solve it directly. To handle this optimization problem, we propose an efficient iterative algorithm based on block coordinate descent (BCD) method. The original problem is decoupled into three subproblems to solve separately. Simulation results demonstrate that the proposed scheme can significantly improve the sum-rate performance over various schemes.

翻译：蜂窝网络与设备到设备（D2D）通信共存的问题已被广泛研究。可重构智能表面（RIS）和非正交多址接入（NOMA）是5G、6G及未来通信演进中的关键技术。此外，稀疏码多址接入（SCMA）被认为是码域NOMA中适用于下一代无线网络的方案。本文研究了RIS辅助的上行SCMA蜂窝网络与D2D用户共存场景。我们构建了一个优化问题，旨在通过联合设计D2D用户的资源块（RB）关联、蜂窝用户和D2D用户的发射功率以及RIS处的相位偏移，最大化蜂窝系统总速率。同时考虑了功率限制和用户通信需求。该问题是非凸的，直接求解具有挑战性。为处理此优化问题，我们提出了一种基于块坐标下降（BCD）方法的高效迭代算法。原问题被分解为三个子问题分别求解。仿真结果表明，所提方案相较于多种对比方案能显著提升总速率性能。