Reconfigurable intelligent surface (RIS) has emerged as a promising technology for achieving high spectrum and energy efficiency in future wireless communication networks. In this paper, we investigate an RIS-aided single-cell multi-user mobile edge computing (MEC) system where an RIS is deployed to support the communication between a base station (BS) equipped with MEC servers and multiple single-antenna users. To utilize the scarce frequency resource efficiently, we assume that users communicate with BS based on a non-orthogonal multiple access (NOMA) protocol. Each user has a computation task which can be computed locally or partially/fully offloaded to the BS. We aim to minimize the sum energy consumption of all users by jointly optimizing the passive phase shifters, the size of transmission data, transmission rate, power control, transmission time and the decoding order. Since the resulting problem is non-convex, we use the block coordinate descent method to alternately optimize two separated subproblems. More specifically, we use the dual method to tackle a subproblem with given phase shift and obtain the closed-form solution; and then we utilize penalty method to solve another subproblem for given power control. Moreover, in order to demonstrate the effectiveness of our proposed algorithm, we propose three benchmark schemes: the time-division multiple access (TDMA)-MEC scheme, the full local computing scheme and the full offloading scheme. We use an alternating 1-D search method and the dual method that can solve the TDMA-based transmission problem well. Numerical results demonstrate that the proposed scheme can increase the energy efficiency and achieve significant performance gains over the three benchmark schemes.

中文翻译：

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使用 NOMA 的节能可重构智能表面移动边缘计算网络

可重构智能表面（RIS）已成为在未来无线通信网络中实现高频谱和能源效率的有前途的技术。在本文中，我们研究了 RIS 辅助的单小区多用户移动边缘计算 (MEC) 系统，其中部署了 RIS 以支持配备 MEC 服务器的基站 (BS) 与多个单天线用户之间的通信。为了有效地利用稀缺的频率资源，我们假设用户基于非正交多址 (NOMA) 协议与 BS 通信。每个用户都有一个计算任务，可以在本地计算或部分/完全卸载到 BS。我们旨在通过联合优化无源移相器、传输数据大小、传输速率、功率控制、传输时间和解码顺序。由于产生的问题是非凸的，我们使用块坐标下降法来交替优化两个分离的子问题。更具体地说，我们使用对偶方法来解决具有给定相移的子问题并获得封闭形式的解决方案；然后我们利用惩罚方法解决给定功率控制的另一个子问题。此外，为了证明我们提出的算法的有效性，我们提出了三种基准方案：时分多址（TDMA）-MEC方案、全本地计算方案和全卸载方案。我们使用交替的一维搜索方法和对偶方法可以很好地解决基于 TDMA 的传输问题。