Research On Key Technology Of MIMO-OFDM In The Next Generation Broad Band Wireless Communication System

The next generation broad band wireless communication system achieves to provide more communication business, higher communication rate and better communication quality under a condition of limited spectrum resources. In the context of this demand, communication industry is facing a new challenge. Multiple Input Multiple Output (MIMO) system improves the data transfer rate without frequency resources loss and transmit power resources loss by a large margin, while the outstanding advantage of orthogonal frequency division multiplexing (OFDM) is the elimination of ISI by using cycling prefix and reducing the data rate in sub-carriers. Therefore, MIMO-OFDM transmission system which combines MIMO system with OFDM technology will become the core technology of4G communication system.Despite the MIMO system, OFDM system or MIMO-OFDM technology, there are their main problems and key technologies. For example, there are Channel modeling, channel capacity, Space-Time Block Coding, channel estimation,2D-RAEK receiving, space-time multi-user detection and so on in MIMO system; Peak-to-Average Power Ratio, synchronization, channel estimation, frequency estimation, interwoven and encoding technology in OFDM system; while in MIMO-OFDM system, there are not only the above key technology, but also the technologies brought by MIMO system and OFDM technology, such as Peak-to-Average Power Ratio and so on. Therefore, the research of MIMO system, OFDM system and MIMO-OFDM system has become hot spots in communication area. As MIMO-OFDM system will become the core of4G communication technology, research achievements in this area are very meaningful to theoretical researches and engineering applications.In this paper, we lucubrate the Space-Time Blocking Coding, channel modeling and channel estimation in MIMO system, synchronization, frequency estimation in OFDM system, and the Peak-to-Average Power Ratio in MIMO-OFDM system, certain research achievements is proposed. The content is as follows:1. Here, we analyzed the performance of STBC in flat low fading channel,flat time-variant fading channel and frequency selective fading channel, then we emulated the three channel models respectively. This part of the research offsets the insufficient of the research on the performance of space-time block coding under time-varying fading channel and frequency selective fading channel, and get some reference value results to the research.2. Research on channel estimation algorithm and correlation channel model in MIMO system. Firstly, comprehensively considerating comprehensively of the decline characteristics and the related characteristics of MIMO channel, and selecting spatial variable rationally, we established a reasonable and relatively simple MIMO space-time related channel model based on the conclusion of the existing methods and models.3. Analysis of synchronization technology in OFDM system. Two methods is proposed in this paper aiming at improving synchronization in OFDM system, one is an improved OFDM joint timing and frequency synchronization algorithm based on Schmidl algorithm aiming at the synchronization problem of OFDM. This algorithm boradened the range of frequency estimation,and the plateau in Schmidl algorithm is eliminated. The other is a new joint symbol timing and frequency synchronization algorithm aiming at the synchronization problem of OFDM, which has special phase rotation relationship in the frequency domain. New frequency offset estimation algorithm is characteristic of large estimation range and high accuracy.4. Analysis to Peak-to-Average Power Ratio algorithm in MIMO-OFDM system. Firstly, by combining the characteristics of SFBC and IFFT, we put forward Twice Partial Transmit Sequence (T-PTS) algorithm used for SFBC MIMO-OFDM system, which can use the linear and cycling shifting and conjugate characteristics of IFFT. Then we propos RT-PTS algorithm, it can simplifies the process of searching weights, reduces the maximum extent the computing complexity. Simulation results show that the proposed algorithm can obtain better performance in the lower complexity.Then, by combining the characteristics of SFBC and IFFT, and improvied CFPI algorithom, we put forward multiphase rotating exchange PIP algorithm used for SFBC MIMO-OFDM system. It can use the linear and cycling shifting and conjugate characteristics of IFFT. The algorithm reduced the complexity of calculation when obtaining better PAPR reduction. Simulation results show the feasibility and efficiency of the algorithm.