Joint channel-physical layer network coding in multi-way wireless relay systems

Abstract

During the last two decades or so, physical layer network coding (PNC) has received a considerable attention as it provides superior spectral e ciency over conventional relaying, in wireless relay systems. However, error performance of the network coded relay systems is inferior to that of conventional relaying under poor quality channel conditions. On the other hand, channel coding provides improved error performance over noisy and fading channels. In channel and PNC coded wireless relay systems, a better performance can be achieved by performing channel decoding and network coding at the relay jointly compared to separately. However, the existing joint channel decoding and network coding algorithms cannot achieve a good trade-o between error performance and spectral e ciency when applied in a multi-way wireless relay system. This is mainly due to the fact that the existing algorithms operate the constituent sub-decoders independently. With the advancement of new trends such as Internet of Things (IoT), multi-way wireless relay system has been a popular network topology, hence joint channel decoding and network coding algorithms having very good spectral e ciency-error performance trade-o s are highly desired. This thesis presents, as the key technical contribution to the existing body of knowl- edge, a joint channel-physical layer network coding (JCPNC) algorithm for multi-way wireless relay systems, which achieves an improved trade-o between error performance and spectral e ciency. This improved performance is a result of harnessing additionaldiversity combining schemes are proposed and they are compared with each other. The thesis also presents an improved symbol value selection algorithm for the conventional non-binary symbol- ipping low density parity check decoder which is adopted to pro- duce a low-complexity JCPNC algorithm. Moreover, a novel JCPNC algorithm which can be employed in asymmetric multi-way wireless relay systems, is developed. Finally, the convergence behaviour of the proposed JCPNC algorithm is analyzed using extrinsic information transfer (EXIT) characteristics of the constituent sub-decoders. The error performance of the proposed algorithms is extensively investigated using computer simulations. The simulation results demonstrate that the proposed JCPNC algorithm and its variants achieve superior spectral e ciency-error performance trade- o s than the existing counterpart JCPNC algorithms. time diversity by exchanging information between constituent sub-decoders. Several