Research On Combining Schemes Of MIMO And Network Coding In Wireless Relay Networks

The traditional forwarding scheme of a node is replicating and forwarding in the content forwarding networks with many nodes. Throughput can be significantly enhanced by using network coding. Furthermore, for wireless communications, throughput can be increased more by adopting physical-layer network coding thanks to the broadcasting nature of wireless channel.Fading is a difficulty hard to cope with in wireless propagating environment. Facts have proved that MIMO can effectively take advantage of wireless channel to overcome the fading and can improve the validity and reliability.Network coding and MIMO are both methods to improve the throughput. There are similarities between NC and MIMO in nature and many scholars are studying on combining them into one system. The common scene is the Two-way relay channel. But after our research, we find some limitations of TWRC. The two source nodes have to store the packets they have sent and whenever one node wants to exchange messages, the other one must have one to be exchanged.This paper proposes a new model called TWRC by a new node D. By using complex field network coding, we never assume the nodes have to store the packets and the messages between the two nodes are unnecessary asymmetrical. Node D can decode all information only by receiving one CFNC coded packets and the throughput is higher. Based on this system, our scheme aims at symmetrical modulation and asymmetrical modulation. We optimize the shaping of constellation by finding the best coding coefficients and maximize the minimum Euclidean Distance of the constellation, which in turn improves the BER performance. We also study the relationship between the minimum Euclidean Distance and BER performance. Simulations verify the theory analysis. Our optimal shaping constellation outperforms the theory constellation.