On The Performance Of Full-duplex Multi-relay Networks Towards 5G

With the fast growth of the number of mobile users and rapid development of data services, the next generation of mobile communication networks(5G) puts forward higher requirements for improving spectrum efficiency, energy efficiency and reducing transmission delay. Unallocated millimeter wave band opens a new direction to improve the spectrum efficiency. But as millimeter wave depends on the line-of-sight transmission, when the signal is blocked, information needs to be forwarded by multi-hop transmission. Cooperative relaying technique is recognized as one of key technologies to effectively expand the coverage of wireless communication networks and improve the communication quality and robustness of the systems. In addition, in order to adapt to the development of smart city, wireless sensor networks and ad hoc networks are used more widely, and their typical environment of short range, high density, low power and multi-hop transmission, provides a wider space for the application of cooperative relaying technologies.Conventional communication devices typically operate in half-duplex mode, which greatly limits the spectral efficiency of the networks. Full-duplex techniques that communication devices can transmit and receive signals simultaneously in the same frequency band, can nearly double the spectral efficiency. Full-duplex technique can be directly applied to existing relaying system architecture, and has good portability and a wide range of application scenarios.Therefore, it is recognized as one of key technologies towards 5G. Started with conventional half-duplex relaying networks, this paper mainly studies important performance metrics of full-duplex relaying networks, such as outage probability and diversity order.This paper first studies a class of equivalent full-duplex two-relay networks, in which two half-duplex relays in turn help the source to forward information to the destination, which achieves equivalent full-duplex relaying with shorter delay and lower network complexity. We use Markov model to analyze the signal reception performance at relays and the destination, and then easily obtain closed-form outage probability of the system. Analytical and simulation results show that the proposed system can achieve significant performance improvement at low and modest signal-to-noise(SNR) ranges.In order to obtain diversity gains of multi-relay systems while achieving spectral efficiency improvement, this paper then further investigates a class of equivalent full-duplex multi-relay neworks. Similarly, we first analyze the decoding performance of the relays and deduce outage probability of the system and asymptotic performance at high SNR range, namely, diversity order and error floor. By comparison with the existing half-duplex relaying networks, the prposed system has a better performance in low rate scenario, achieving a close-to-full diversity order. In high rate scenario, the system is an interference-limited system. Even so, at low and modest SNR ranges, the proposed system can achieve significant performance improvement.For the sake of taking advantage of full-duplex technologies to improve spectrum efficiency, this paper further studies full-duplex multi-relay networks. Simulation results display that with the enhancement of self-interference elimination ability at relays and the increasing number of relays, the proposed system can achieve spectrum efficiency of full-duplex networks, while obtaining higher diversity gains.The system design and performance analysis of(equivalent) full-duplex relaying networks in this thesis provide important theoretical basises and design principles for the next generation of mobile communication networks to promote spectrum efficiency, reduce network delay and enhance network robustness.