Resource Allocation For OFDMA Relay Networks

With the development of communication technology constantly, people are more concerned about the quality of service and data transmission rate of communication system. The next-generation wireless communication needs not only increasing the system coverage to provide high ubiquitous coverage of radio channels for people, but also improving system architecture and efficient resource operating technique to provide high data-rate communication for people. Introducing the relay nodes into traditional cellular network, it can use relay technology to achieve higher data-rate requirements. High data rate and high capacity rely on frequency spectrum is always really rare in mobile telecommunication system. How to improve the spectrum efficiency to satisfy different users with different QoS requirements becomes an important issue for researches. OFDMA is the evolution of OFDM, it can eliminate inter-symbol interference and improve the spectrum utilization. Combining relay with OFDMA can exploit both advantages of them. The rate and reliability of the communication will be dramatically improved together.Certainly, the combination of relay and OFDMA can form new structure for the characteristics of the system, increasing the freedom and complexity of the resource allocation. To solve a joint optimization problem for relay selection, subcarrier assignment and power allocation, basic mathematical model is formulated. In chapter 3, in order to solve the problem that how to prolong the battery life, maximize the survival time of the whole relay system and reduce the rate of loss, a detailed analysis and discussion are given. By formulating a problem model, giving a new weighting factor that reflects the residual capacity of different relay, putting forward a new optimization problem and solving it, and using simulation method to analyze the problem; it verifies the correctness of the algorithm and can be implemented. Throughout the analysis process, the complex issues can be simplified and the abstract theories can be concrete. Finally the solution to the master problem is found and the research that how to use relay resources rationally, as well as improve the service life of system is got.In chapter 4, how to improve the fairness among users has been discussed. Under the premise that guarantees the minimum rate of each user, how to narrow the gap as far as possible between the actual rate among users and the predetermined rate and guarantee user satisfactions for multi-service transmission, this paper puts forward three kinds of solutions. The simulation results show that the proposed three schemes can improve the fairness of users in varying degree. But the system throughput reduces some time than before. Scheme three get the best effect of fairness, but its rate of loss is the biggest, it requires a good compromise between the fairness of different users and the system throughput.