Research On Wireless Resource Management In Multiuser MIMO-OFDM System

MIMO, Multi-Input and Multi-Output, and OFDM, the Orthogonal Frequency Division Multiplexing, combined with adaptive transmission method have been widely considered as the major trend and basis of the development of the next generation mobile communication system. Generally speaking, the adaptive wireless resource allocation can effectively use the limited resources to enhance system capacity. Therefore, the research on adaptive wireless resource allocation algorithm has been one of the hot topics during recent academic researches all over the world.Firstly, this paper proposed one combined adaptive subcarrier and power allocation algorithm for OFDM system. Adaptive subcarrier allocation algorithm in multiuser MIMO-OFDM system means that we can rely on the instantaneous channel conditions of different users located in different positions within the cell to adjust the subcarrier allocation among them. Theoretical researches have shown that comparing to the traditional static allocation method, adaptive allocation algorithm can enhance the system capacity significantly by exploiting multiuser diversity resulting from the random locations of different users. The algorithm here also has a proportional requirement of different users. To meet the practical system design requirement, we can set a reasonable data transmission speed for each user in advance. However, the optimization problem for adaptive subcarrier and power allocation is a very complex, multiple parameters and non-linear problem. It requires large computation effort to find the exact optimized solution. Therefore, all the algorithms in this paper are the suboptimal algorithms based on certain simplifications. But the system throughput can be improved significantly compared to those traditional static allocation algorithms.Secondly, this paper studies the adaptive resource allocation based on genetic algorithm. Genetic Algorithm is a very effective search technique of finding the solution for the complex, multiple parameters and non-linear optimization problem. The adaptive subcarrier allocation algorithm based on genetic algorithm improves system capacity, compared to the greedy algorithm. Investigation to the different stages of genetic algorithm, such as coding, crossover and mutation, has also been done in this paper to design a unique genetic algorithm for the wireless resource allocation in OFDM system. Simulation results show that the performance can be improved. Genetic algorithm can find the global optimum solution while the greedy algorithm can just find the local optimum solution to the problem.The third part of this paper focuses on the adaptive wireless resource allocation in MIMO-OFDM system. The adaptive subcarrier allocation, bit loading algorithm and power allocation using water filling algorithm are considered together to improve system throughput. As we know, multiple antenna systems add another degree of freedom, spatial freedom. Therefore, according to the Frobenius Norm theory, the system performance can be improved by maximizing the singular values of the channel matrix. Then we propose a new dynamic subcarrier and power allocation scheme based on SVD (Singular Value Decomposition) method. From the simulation result, we can see that the proposed scheme outperforms traditional beamforming schemes in the range of high SNR (Signal Noise Ratio). The proposed scheme exploits comprehensively both the spatial diversity resulting from multiple antennas and also the multiuser diversity resulting from the multiuser system.Due to the limitation of time and the personal ability of the author, this paper just completed a superficial research on the wireless resource allocation algorithm. The last part of this paper gives a summary of author's work and several areas which could be studied in the future.