On The Capacity-enhanced Technique Based On Cooperative Relaying System And Non-orthogonal Multiple Access

Driven by the rapid development of Internet services and the emergence of the concepts of Internet of Things(IoT)as well as vehicle networking,the next generation wireless communication systems have to solve serious challenges owing to the increasing demands of the data traffic explosion.Due to the limitation of spectrum resources,reaserch on techniques achieving higher spectral efficiency has become a hot topic.Cooperative relaying system(CRS)has been recognized as an effective way to acheive spatial diversity gain,but it may limit the spectral efficiency owing to the duplicate transmission.The idea of non-orthogonal multiple access(NOMA),different from the underlying physical connection as orthogonal multiple access(OMA)in current network,can further improve the capacity and spectral efficiency performances and has been considered as a promising candidate for the fifth generation(5G)wireless communication.NOMA-CRS can not only achieve diversity gain but also enhance the capacity of system.In this thesis,we first introduce a typical NOMA system and then study the NOMA-CRS,after that a novel receiver design to improve the system performance is proposed.Finally,time slots involved are extended,and performances are also investigated.For CRS-NOMA,the source simultaneously transmits two symbols by employing the superposition code,and the relay decodes and forwards the symbol with lower allocated power by employing the successive interference cancellation(SIC).Different from the existing one,our proposal allows the destination to jointly decode both symbols transmitted by the source by adopting maximum ratio combination(MRC)and SIC.Furthermore,the ergodic sum rate and the outage probability of the system are investigated.A suboptimal power allocation strategy is also designed.Both analysis and simulations reveal the advantages of the proposed scheme.Besides,NOMA-CRS with three time slots involved outperforms over the usual NOMA-CRS with two time slots involved.