Research On Physical Network Coding In Wireless Communications

The concept of network coding, which was used to improve the end-to-end throughput performance in wireline packet networks, was proposed in 2000. Recently, a lot of research work focus on how to apply network coding in wireless networks. The broadcast nature of wireless environment makes it convenient to apply network coding technique in wireless networks to improve the efficiency of wireless transmission.Bi-directional wireless relaying scenario is one of the building blocks of wireless multi-hop communications. Because of the two-way data flows, wireless network coding could be applied at the relay node. Comparing to the traditional relaying techniques, better throughput performance can be obtained. Many researches are developed in two-way wireless relaying systems, and many transmisstion schemes and strategies are proposed. With the development of the research on wireless network coding, the efficiency of the transmission is improved continuously. Accordingly, the cost brought by the increasing of system complexity and the decreasing of transmission reliability is increased. How to balance the efficiency and reliability of the transmission in the wireless communications in which network coding technique is used, is what is focused on in the thesis.In the thesis, based on the thought of network coding, the researches focus on the modifying design of physical network coding techniques. The main works and contributions of the thesis include as follows:First, based on the introduction of the concept of network coding, the principle, character, design method, etc. is represented, the sense of necessity and importance of further modifications for physical network coding technique are indicated, and the related research results in the field, are summarized comprehensively.Second, the impact on the selection of physical network coding schemes made by the variation of rician K-factor in the Nakagami-Rice fading channels was discussed. It is indicated that the sum of the probability of selecting 5-ary denoise mapping schemes and the one of selecting 4-ary denoise mapping schemes equals 1. Furthermore, with the increasing of rician K-factor, the probability of selecting 5-ary denoise mapping schemes is decreasing. When the values of rician K-factor keep constant, the probability of selecting 5-ary denoise mapping schemes at the relay node is a fixed value. The simulation curve is demonstrated.Third, the modifying design of the physical network coding technique based on denoise-and-forward (DNF) method in Nakagami-Rice fading channels, in the two-way wireless relaying communication scenarios, is deeply researched. The physical network coding and source coding are jointly considered. A novel joint design scheme is proposed, which not only reduce the complexity of the tranceivers of all the nodes, but also improve the reliability of the transmission. The essence of joint design scheme proposed by us, is to use computing to get better performance in return, and the cost is acceptable.