Research On The Performance Of Physical-layer Network Coding In The Cooperative Communication Systems With Multiple Relays

Along with the rapid development of wireless network, people put forward a higher request on the wireless communication technology, for example, faster speed of data transmission and lager amount of data. But problems like serious fading and small coverage still exist in wireless straightforward data transmission. More often than not, data transmission may will fail without the help of relay node. In 2000, Ahlswede first put forward the concept of Network Coding (NC):which uses a relay node to process data before forwarding. In 2006, Zhang and others applied the concept of NC in physical-layer, named it as Physical-layer Network Coding (PNC), which makes full use of electromagnetic signal’s additivity, and meanwhile by taking advantage of the interference signal, throughput of PNC achieves a 100% increase compared with traditional transmission way. This thesis is aimed to probe in depth into PNC technology and its performance on bidirectional multiple relays’ cooperative communications system.In the actual wireless cellular system, there are multiple relay nodes between source node and destination node, this thesis sets up multiple-relay PNC communication simulation platform, and selects SC-PNC criteria in numerous relay selection schemes. Then the simulation results are showed under Rayleigh and Nakagami channels in Monte-Carlo method.This thesis mainly studies joint relay selection and water power allocation strategy. Firstly, performance of the system based on the MPSK modulation is simulated. Secondly, this thesis studies two Relay Selection and Power Allocation (RS-PA) strategies:Maximize Min Rate (MMR)-based RS-PA strategy and Maximize Sum Rate (MSR)-based RS-PA strategy. In order to increase the total-rate of the system, an improved RS-PA strategy for MSR is proposed. For simplify, this thesis proposes an iterative solution algorithm for OPA, which is applied in the multiple relays’ PNC system based on symmetric and asymmetric modulation. Finally, this thesis analyzes comparatively simulation results of three RS-PA strategies. Results show that the improved strategy of MSR-based RS-PA effectively increases the total rate of system.