Study On The Cooperative Communication Based On Network Coding

The multipath fading in wireless channel has affected system performanceseriously. Multi-input Multi-output (MIMO) can use spatial diversity to overcomechannel fading, which obtains good system performance. However, the MIMOtechnology can’t be used on small terminal because of its high demanding requirementof the antennas’ physical location. So the researchers need to find another way to solvethis question. Then, the cooperative communication was proposed. The cooperativecommunication can use multiple nodes’ resource to build virtual MIMO and hasrealized to overcome fading effectively. Network Coding (NC) further compresses thenetwork information flow through using the node processing capability, which improvesthe system transmission efficiency. Although combining these two technologies can takemuch improvement, there are still some questions in cooperative network codingsystem.The cooperative nodes can make a decision about when to cooperate and how tocooperate through feedback mechanism, and then improve energy utilization. Theoptimal power allocation plays an important role to increase system outage capacity. So,in order to solve the related questions and further optimize the system communicationperformance, the thesis studies the cooperative communication based on networkcoding from two aspects which are feedback mechanism and optimal power allocation.The main work is as follows:①The thesis introduces two basic forwarding tactics. One is Amplify and Forward(AF) and the other is Decode and Forward (DF). The thesis writes signal expressionrespectively and makes simulation of bit error performance with different forwardingstatics. Simulation results show that these two statics can obtain similar bit errorperformance compared with theoretical performance in Rayleigh channel of two orderdiversity. And the thesis sets a big Monte Carlo value when making simulation.②Research on the cooperative communication based on network coding in finitefield. In the chapter three, the paper proposes a feedback mechanism to decrease theredundant messages sending. The base station sends a little feedback information to theusers at the end of first slot, which realizes opportunistic network coding. In the study,the analysis shows that the feedback mechanism saves system users’ power in thesituation of two users’ cooperative communication based on network coding. And the feedback mechanism won’t increase the system outage probability. The thesis makes asimulation of energy consumption and outage probability in network coding cooperativesystem based on binary and GF(4) field. Then the thesis considers the situation that theamount of users is bigger than two. When there are many users in the system, theinformation sending between cooperative users will be hard and the feedbackmechanism will affect the system outage probability. With the amount of usersbecoming larger and larger, the system will get worse performance. So the thesis adoptsa grouping method. When the system contains many users then the users will be dividedinto many groups and each group contains two users.③The user nodes send messages using equal power will produce low resourceutilization in the network coding cooperative system. In order to solve this question, thethesis proposes a convex optimal energy allocation and applies it into direct networkcoding and physical network coding cooperative communication system with two-wayrelay. Comparing with equal power allocation, the convex optimal energy allocation canobtain larger capacity and won’t increase system outage probability. The thesissimulates the influence of relay position to system capacity applied convex optimalenergy allocation.