Recently, a versatile user cooperation method called coded cooperation diversity has been introduced, in which the codewords of each mobile are partitioned and transmitted through independent fading channels instead of simple repetition relay, to achieve remarkable gains over a conventional (non-cooperation) system, while maintaining the same information rate and transmission power. In this paper we present an adaptive space-time (AST) coded cooperation scheme based on the decoding operation on the first partition of the codeword at the base station and enables practical adaptive arrangement of resources to adopt the channel condition. Performance analysis and simulation results have proved that the proposed scheme greatly improves error rate performance and system throughput, compared with the previous framework.

Despite the appealing advantages of reconfigurable intelligent surfaces (RIS) aided mmWave communications, there remain practical issues that need to be addressed before the large-scale deployment of RISs in future wireless networks. In this study, we jointly consider the non-neglectable practical issues in a multi-RIS-aided mmWave system, which can significantly affect the secrecy performance, including the high computational complexity, imperfect channel state information (CSI), and finite resolution of phase shifters. To solve this non-convex challenging stochastic optimization problem, we propose a robust and low-complexity algorithm to maximize the achievable secrete rate. Specially, by combining the benefits of fractional programming and the stochastic successive convex approximation techniques, we transform the joint optimization problem into some convex ones and solve them sub-optimally. The theoretical analysis and simulation results demonstrate that the proposed algorithms could mitigate the joint negative effects of practical issues and yielded a tradeoff between secure performance and complexity/overhead outperforming non-robust benchmarks, which increases the robustness and flexibility of multiple RIS deployments in future wireless networks.