Research Of MIMO Channel Prediction And Pre-processing Technology In The High-speed Railway Mobile Environment

With the growing demand for mobile communications business from society, mobile communications is one of the fastest growing disciplines currently. Multiple input multiple output (MIMO) is a key technology in the new generation mobile communication, which is also a currently hot research field of mobile communications. Compared with the single antenna system, MIMO systems can significantly improve the information rate, the quality of information transmission, and the communication capacity. Currently, MIMO technology has been widely used in broadband wireless access, such as long-term evolution (LTE) wireless communication system.The performance of MIMO systems greatly dependents on the transmission characteristics of MIMO wireless channel. Accurate channel state information (CSI) plays a vital role improving the system capacity. Communication system uses the channel state information to achieve space-time coding, precoding, adaptive modulation, power control and so on.In the mobile communication system, the CSI is obtained from channel reciprocity and feedback. The CSI in the present moment is no longer suitable for the system to send downlink data in the future, ie, the time varying characteristic lead to the channel state information out of date. It is difficult to obtain the channel state information in the context of fast fading channel. The next generation wireless communications need to support ultra-high mobile speed up to500km/h. Therefore, it is necessary for the system to obtain accurate channel state information in the future, or directly reduce or even overcome the channel state information, in order to significantly improve system performance.The channel prediction technique can effectively modify the inaccurate channel state information, and is one of the popular techniques in recent years. The system estimate the channel state information of the current moment by using reference symbols and use the channel state information to predict or modify the channel state information in the future.With the continuous development of high-speed railway, the mobile communication environment is worsening, the applicability of some traditional communication technologies is constantly being challenged. Different from the traditional space-time coding techniques, the unitary space-time coding techniques, can be applied in a very bad channel with unknown channel state information, in order to overcome the system can not normally obtain CSI.First, the MIMO channel prediction techniques in researched. Several common channel prediction algorithms are investigated, including MMSE and adaptive filter. The performance of precoding by channel prediction is studied as further verification.. The MMSE prediction algorithm is based on channel global statistical properties. The adaptive filter algorithm is based on partial stability of data, according to the structure, adaptive filter can be divided into these three methods:NLMS, RLS and Kalman. Finally, with the combination of local stability and global statistical properties, new prediction strategy is proposed.Then, the unitary space-time modulation techniques are studied, including traditional unitary space-time coding techniques and differential unitary space-time coding techniques. Further, various simulations in different constellations, Doppler expansion, demodulation method and time varying channel is analyzed. Finally, a new differential demodulation method is proposed base on channel prediction. Compared to conventional demodulation method, the demodulation performance is increased.