Research On Adaptive Allocation Algorithm In MIMO-OFDM System

With the development of mobile communication and wireless Internet, wireless communication has become a key technology for the global information communication. Information and communication technology (ICT) is playing an increasingly important role to improve the world economy and supporting the rapid development of other industries. However, how to make full use of the limited communication resources becomes the focus of the wireless communication’s development. It also means that the optimization problem in wireless communication system becomes more and more important. OFDM technology can effectively solve the problem of signal interference caused by multipath propagation and MIMO technology can effectively improve the system capacity and spectral efficiency. They are the key technologies of wireless communication. The rational allocation of communication resources requires adaptive technology. If we use adaptive technology in wireless communication system, communication resources will obtain the reasonable allocation. This paper will mainly study the adaptive allocation algorithm in MIMO-OFDM.This paper firstly introduces the development of wireless communication and the research status of the adaptive technology, then gives the characteristic of wireless communication channel, and analyzes large scale effect of channel, small scale effect of channel, two kinds of commonly used channel model and the knowledge of channel estimation. Secondly, introduces three technologies:MIMO, OFDM and MIMO-OFDM. Simulates and analysis the capacity of MIMO system from the aspect of different number of antennas, and gave the advantages and disadvantages of MIMO system. Then detailed introduces the principle of OFDM, the roles of cyclic prefix, and gives the advantages and disadvantages of OFDM system. Simple introduces the basic principle of MIMO-OFDM system and the advantages and disadvantages. Finally, the paper introduces the application of adaptive technique in MIMO-OFDM, gives three kinds of typical adaptive algorithms:Fischer algorithm, Hughes-Hartogs algorithm and Chow algorithm, and simulates the three algorithms. Through the contrast analysis:the performance of Hughes-Hartogs algorithm is the best, but its complexity is too high; then aiming at reduce the high complexity of Hughes-Hartogs algorithm, a improved algorithm is proposed, and simulates the improved algorithm and Hughes-Hartogs algorithm from the number of iterations and the power allocation, the results show that, the number iterations of the improved algorithm is obviously less than the greedy algorithm, and the realization is simple, the performance is very close to the Hughes-Hartogs algorithm.In a word, the adaptive algorithm can allocate the limited communication resources optimally in the MIMO-OFDM system.