非正交多址接入下高可靠性协作多播技术研究

Non-orthogonal multiple access (NOMA) technique, which realizes multiple access in power domain by transmitting multiple data streams with different power levels at the same time/frequency/code domain wireless resource, is a new frontier of wireless communications. To overcome the low reliability drawback of wireless multicast, this project exploits the inherent features of NOMA technique to study NOMA cooperative multicast in following three aspects: 1. Opportunistic NOMA cooperative multicast. Considering opportunistic non-orthogonal access between a unicast user and multicast users, this project proposes a cooperation strategy where the best unicast user is selected to forward information to multicast users, in order to maximally improve the diversity gain of multicast service. 2. Non-opportunistic NOMA cooperative multicast. Considering that a number of unicast users and multicast users access the same wireless resource by NOMA, this project designs a cooperation strategy where both the order of decode-and-forward of unicast users and superposition of forwarding signals are determined in an optimal fashion, to enhance the reliability of unicast and multicast simultaneously 3. Low-overhead implementation of NOMA cooperative multicast. Through the acquisition of local channel information at each user and limited signaling exchange among users, this project presents the low-overhead distributed implementation schemes for opportunistic/non-opportunistic NOMA multicast, where the overall system overhead is not higher than square level and the overhead at base-station/user is just linear level. Aforementioned research issues in this project provide a basis to realize low-overhead reliable NOMA cooperative multicast.

非正交多址接入(NOMA)技术以不同功率将多个信息流在时域/频域/码域重叠的无线资源上传输，实现了功率域多址接入，是无线通信的新方向。本项目利用NOMA技术中用户非正交接入的特点，针对多播业务可靠性问题，从三方面展开NOMA协作多播研究：1.机会式NOMA协作多播。研究机会式单播/多播用户非正交接入的协作转发策略，由最佳单播用户向多播用户转发信息，最大限度提高多播业务分集增益。2.非机会式NOMA协作多播。研究多个单播用户与多播用户非正交接入的协作转发策略，通过最优地调度各单播用户解码、转发顺序和构造混合转发信号，同时提高单播/多播业务可靠性。3.NOMA协作多播的低开销实现。通过各用户获取局部信道信息和用户间少量信令交互，分布式实现机会式/非机会式NOMA协作多播，将系统总开销控制在平方级、基站/用户开销控制在一次方级。本项目的研究对实现低开销、高可靠性的NOMA协作多播有支撑意义。

非正交多址接入（NOMA）技术利用功率域多址原理，将多个信息流在时域/频域/码域重叠的无线资源上发送，可提高无线传输吞吐量，改善用户接入公平性。本项目利用NOMA技术的多用户非正交接入特性，针对无线多播业务的可靠性问题，完成了如下三方面研究工作：1. 机会式NOMA协作多播。针对混合型和分层型两种NOMA多播场景，设计了多种高可靠性机会式NOMA协作多播传输策略，并提出了相应的最佳协作转发用户调度准则；2. 非机会式NOMA协作多播。针对分层型NOMA多播场景，提出了非机会式NOMA协作多播策略，通过部分用户的协同转发，提升分层型NOMA多播的可靠性；3. NOMA协作多播的低开销实现。为降低通信开销，设计了上述NOMA协作多播策略的低开销实现方案，通过用户间少量的信令交互，将系统总通信开销控制在平方级、基站/用户端开销控制在了一次方级。本项目的研究成果对于实现低开销、高可靠的NOMA协作多播具有指导意义。