Research On Adaptive Resource Allocation Algorithms In OFDM System

Along with the development of wireless communication, the request to the quality of wireless service has being increased rapidly, which contradicts with the limitted wireless resources. Many efforts have been done to solve this incresing contradiction. In the physical layer, OFDM is the suitable technology to wideband wireless system; in the linking layer, the frequency spectrum efficiency can be improved by resource allocation and dispatch algorithm, which has been focused in the last ten years.The main idea of OFDM is making good use of channel allocation and the serial parallel conversion. At first, it makes the wireless channel to some sub-channels which are orthogonal each other. Then, the serial data is converted to parallel and allocated to these sub-channels to transmit. The transmission rates of these sub-channels are slow. OFDM has many advantages in wireless data transmission such as higher transmission rate, better anti-multipath interference, spectrum efficiency and utilization. Meanwhile, the adaptive allocation technology of bit and power could be used in the OFDM, which is based on the characteristic of every sub-channel, signal faint and multipath delay. The relavent knowledge about modern communication technologies is firstly discribed in this paper, including history, present situation, development tendency, the wireless channel characteristics, OFDM basic principle, advantages and drawbacks, the key technologies; adaptive technology, e.t. At the same time, analysis and simulation are made for OFDM system.Then, two situations of OFDM system adaptive technologies are discussed comprehensively.①adaptive resource allocation for single user OFDM system: a power and bit allocation for OFDM system based on Genetic algorithm (GA) is proposed according to the Margin Adaptive(MA) resources allocation criteria;②adaptive resource allocation of multi-user OFDM system: a resource allocation based on Artificial Intervals algorithm(AIA) is presented by the Rate Adaptive(RA) resources allocation criteria. The performances of these algorithms are simulated by Matlab and the results are analyzed. The conclusion is made that the performances of Genetic and Artificial Intervals algorithm are better than other algorithms available.Finally, summary and conclusion are made and prospectivs for further research is put forward.