基于固定速率的多用户缓冲协作网络自适应传输模式选择策略研究

For the conventional cooperative communication technique, cooperative nodes transmit or receive messages under a prefixed schedule, which limits the performance of wireless cooperative transmissions. For the past few years, by using buffers, cooperative nodes can adaptively transmit or receive messages according to instantaneous channel quality. This type of adaptive buffer-aided cooperative strategy can significantly enhance efficiency and reliability of cooperative transmissions, which is a frontier topic in the research area of cooperative communication. . Currently, the theoretical study on buffer-aided cooperative networks with only a single user has come to maturity. However, future efforts and works are still needed to further study typical multi-user buffer-aided cooperative networks (MUBCN). Three problems that have not been solved by existing works are illustrated as follows: (1) only few existing works have investigated MUBCN with fixed rates; (2) only relay cooperation has been considered, without considering cooperation between users; (3) user fairness has not received sufficient attention. Therefore, for typical MUBCN with fixed rates, this project focuses on two types of cooperation: relay cooperation and cooperation between users. This project aims to investigate adaptive transmission mode selection (ATMS) strategies, as well as their performances in terms of throughput, delay, and fairness. This project mainly includes the following three works: (1) optimizing ATMS strategies without delay constraints; (2) designing ATMS strategies with delay constraints; (3) utilizing typical fairness criterions to improve user fairness of throughput or delay.

在传统的协作通信技术中，协作节点预设了接收或发送信息的时间表，因而限制了无线协作传输的性能。缓冲器的引入，使得协作节点可以根据瞬时信道质量，自适应地接收或发送信息。这种自适应缓冲协作策略，能够显著地提升协作传输的有效性与可靠性，是当前无线协作通信研究领域的热点之一。. 目前关于单用户缓冲协作网络的研究已趋于成熟，而关于多用户缓冲协作网络（MUBCN）的研究还不够完善：（1）基于固定速率的MUBCN鲜有研究；（2）仅考虑了中继协作，而没有考虑用户间协作；（3）公平性问题还未得到足够的重视。因此，本项目拟针对若干典型的基于固定速率的MUBCN，分别考虑中继协作与用户间协作，致力于研究自适应传输模式选择（ATMS）策略及其吞吐量、时延、公平性等方面性能，主要包括：无时延限制的ATMS策略优化；具有时延限制的ATMS策略设计；利用典型的公平准则，改善用户吞吐量或时延公平性。

针对若干典型的协作网络或多用户传输系统模型，分别在无时延限制与有时延限制时，从有效性、可靠性和安全性等方面对自适应协作传输策略的性能展开研究，为发展协作通信技术以及多用户传输技术的研究奠定理论基础，主要在以下几个方面取得了一系列研究成果。.（1）针对缓冲协作网络，在无或有时延限制时，设计并优化自适应选择或中继选择策略，分析了反映系统有效性或可靠性的吞吐量、中断概率、平均时延等性能指标，阐明了影响缓冲辅助网络性能的关键因素，揭示了缓冲辅助技术得到的性能增益；.（2）针对多用户非正交多址（NOMA）系统，研究了多用户间的公平性、安全性等问题，并且结合协作策略，研究了协作NOMA系统的中继选择方案设计、用户间协作方案设计与关键参数优化等问题，分析了中断概率等性能指标；.（3）将协作传输策略与方法扩展到具有保密约束的无线网络模型，利用物理层安全理论，分析了协作策略对提升保密速率性能的作用机制。