Research On Wireless Resource Management In Multiuser MIMO-OFDM System

With the increasing requirements for high-data-rate multimedia services, multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) techniques have been given more and more interest. MIMO systems can increase the channel capacity and enhance the transmission reliability by employing multiple antennas at the transmitter and receiver. OFDM has the ability of transforming the frequency-selective channel into a collection of parallel flat-fading subchannels and therefore can be adopted in MIMO systems to combat multi-path effects. The MIMO-OFDM system is regarded as a potential candidate for 4G mobile systems.If the channel state information (CSI) is known at the transmitter, adaptive modulation techniques, specifically, adaptive bit and power allocation techniques can be applied to optimize the performance of MIMO-OFDM systems, such as transmit power, bit-error-ratio (BER) and so forthIn this paper, a computationally efficient algorithm for transmit power and bit allocations in wireless MIMO-OFDM communication system is proposed, the aim is to minimize total transmit power under the constraints of data rate and max Bit Error Rate(BER). By exploiting the relation between water-filling level and system data rate, the proposed algorithm finds out an iterative method of searching water-filling level with out preset step and initial value, then allocates the final bits and power with a simplified Greedy algorithm in partial subcarriers. The proposed algorithm avoids the problems of the convergency property, the preset initial values and the selecting of optimal step in traditional adaptive water-filling algorithm by combining the water-filling and the Greedy algorithms effectively, and its computationally efficiency is high. Simulation results verity the performance of the proposed algorithm.The forth part of this paper focuses on the adaptive subcarrier allocation in MIMO-OFDM system. 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.