Reaserch Of Adaptive Modulation And Coding In Wireless Relay System Based On Network Coding

The next generation wideband cellular mobile communication system (IMT-Advanced) will use the wireless relay technology to extend coverage, improve the transmission rate and the system’s spectrum efficiency. Network coding theory requires the nodes on the transmission link not only to forward the received information, but also needs to process the corresponding signal immediately and then forwards the coded-signal to the multi-users. In this way, it can effectively reduce resource overhead, and improve the spectrum utilization and throughput of the system. When adaptive modulation and coding (AMC) techniques applied to wireless relay system based on network coding, there will be many difficulties and changes need to be resolved. This paper studies the adaptive modulation and coding in wireless relay system based on network coding.Firstly, we study the adaptive modulation and coding in network coded multiple access relay channel (NC-MARC). Because the source nodes have two kinds of channel state information fed back from the relay and the destination respectively. So jointly choosing a proper modulation and coding scheme (MCS) for the two sources and the relay becomes a challenge to be solved. In this paper, we investigate the MCS selection for two sources and the relay jointly. We are analyzed the frame error rate and average throughput from the system perspective, and then proposed a low-complexity MCS selection scheme for NC-MARC. The proposed MCS selection scheme is less complicated compared with exhaustive method, so that it has better scalability for practical networks.Secondly, we study the joint adaptive modulation and coding and power allocation based on analog network coded two-way relay channel system (ANC-TWRC). We described the system model and applied Lagrange multiplier method to solve the power allocation scheme without AMC. Then we employed the branch method of integer linear programming to solve the problem of power allocation after the introduction of AMC. In another way, we proposed a simpler algorithm which can be called rapid water injection. The method compares the remaining power and power difference of two classes, then elevates the order or reduces the order to increase throughput or reduce the power consumption. Finally, simulation results show that our proposed algorithm is better than the performance of the Lagrange multiplier method, not only can improve the throughput of the system, but also can reduce the actual power consumption. At the same time computational complexity is lower than the branch method.Finally, on the basis of the first two chapters’theory, we study the implementation and verification of fractional frequency reuse, adaptive modulation and coding and network coding technology over the platform of LTE-A relay which is based on OPNET simulation. We introduce the basic functions of the simulation platform, including the definition of the physical layer frame structure. We then design the communication functional modules, including simulation parameters initialization module, the wireless link initialization module, system synchronization timing module. Based on simulation platform, we implement and verify the technology of fractional frequency reuse, adaptive modulation and coding and network coding over broadcast channel.