Design And Implementation Of Physical Layer Network Coding Scheme In Wireless Multi-hop Networks

Network coding brings throughput improvement for wireless relay networks, through encoding data packets at the relay. Physical layer network coding (PNC) extends this idea by moving the encoding operation to the physical layer. When exchanging packets with PNC, the source nodes transmit the packets simultaneously. The signals carrying the packets superpose in space, and the relay extracts the coded packet from the superposed signal. When using PNC, the throughput of the network can be further increased.This thesis focuses on developing a PNC scheme in wireless multi-hop networks. More explicitly, it focuses on developing a medium access control (MAC) protocol which supports PNC, a rate adaptation scheme for PNC and their combinations.Due to the difficulties of scheduling simultaneous transmissions, most existing works on PNC are based on MAC protocols, which are not applicable to general multi-hop wireless networks. In this thesis, a distributed MAC protocol (named PNC-MAC), that supports PNC in multi-hop wireless networks, is proposed. The proposed MAC protocol is based on the carrier sense multiple access (CSMA) strategy and can be regarded as an extension to the IEEE802.11MAC protocol. While supporting PNC, PNC-MAC is also compatible with conventional network coding and conventional relaying schemes. Simulation results show that PNC-MAC is advantageous in various scenarios of wireless applications.In order to obtain the best performance under different channel conditions, a rate adaptation scheme for PNC (both the amplify-and-forward scheme and the denoise-and-forward scheme) is proposed in this thesis. To further improve the performance, the proposed scheme adjusts both the data rates and the transmission powers of the nodes. Simulation results show that the proposed rate adaptation scheme is advantageous in various scenarios where using PNC is appropriate.Finally, the proposed rate adaptation scheme is combined with the proposed PNC-MAC, in order to make it applicable in practical wireless communication systems.