Novel Non-orthogonal Multiple Access Techniques Based On Index Coding And Rate Splitting

The 5th generation mobile communication technique is developing rapidly.In the future mobile network and internet of things,more and more devices is connecting to the network and the demands of users is getting diverse.The wireless system is facing a more complex access scenario,which brings new challenge to the design of multiple access protocol.As a promising candidate to handle these problems,non-orthogonal.multiple access is attracting more and more attention.In this dissertation,we investigate novel non-orthogonal multiple access techniques under the existing technical background.The contents of this dissertation are summarized as follows.Firstly,a novel downlink multiple access framework based on index coding is proposed.Due to the broadcast feature of wireless channel and increasing caching capacity at terminals,there would be some side information at terminals.However,the side information has not been fully exploited in exiting downlink schemes.So,we design a transmission strategy combining superposition coding and index coding.In a randomly deployed cell,The base station constructs side information graph based on the feedback of indexes from users.Then,the base station transmit encoded message based on the side information graph and the channel state of users.And the simulation result shows that this scheme can improve the throughput of the system.Secondly,we proposed a novel uplink non-orthogonal scheme based on rate splitting.In a massive access network,users may not be distinguished by power difference at the access point.However,the existing detection method based on message passing algorithm is of large complexity despite of its good performance.So we design a new scheme based on rate splitting,in which scheme,each user splits its power to transmit two different data flows,each may of different rate.The two parts of data are superposed before sent to the air.And we verify the feasibility of our scheme by adopting practical channel codes in simulation.Finally,spatially coupling is taken use of to improve the detection structure.Due to the instability and openness of wireless network,a more adaptive scheme is needed.So we adopt a rateless access method based on the rate splitting scheme which we study in the former chapter.To further improve the system,we introduce spatially coupling into the framework.Both rate splitting and spatially coupling,we introduce the irregularity into decoding structure artificially to further improve the convergence result.And we take use of sliding window decoding in the receiver to lower the latency.And the simulation result shows that this scheme can recover the erroneous data packer with less time or frequency resources and is more adaptive.