| Recent years, with the rapid development of mobile wireless communication technology and the increment of communication service demanding, people have higher requirements on mobile wireless communication system. Now widely used existing mobile communication system is the third generation mobile communication system, whose core technology is CDMA(Code Division Multiple Access). 3G system can not satisfy the requirement of high data rate. The next generation mobile communication system(Super 3G,Beyond 3G or 4G) has become the research focus. This new kind of mobile communication system's core technologies are Orthogonal Frequency Division Multiplexing(OFDM) and Multi-Input Multi-Output(MIMO). OFDM is a mobile communication technology and it has the ability to divide a frequency selective fading channel into a number of parallel fading channels. While MIMO is a kind of technology which has multiple antennas. Combing OFDM and MIMO will produce a new technology named as MIMO-OFDM. This method can greatly enhance the capacity of the communication system and will be the key technology in 4G.The performance of mobile wireless communication system is mainly affected by the wireless channel restriction. Because of the obstacles such as buildings or mountains, between transmitter and receiver, the propagation path is very complicated with great randomness. Therefore, the key to improve the performance of communication system is whether the reasonable channel frequency response can be properly evaluated or not. This paper focuses on the channel estimation in mobile communication channel and has detail researches on channel estimation algorithms based on training sequences. Moreover, interference cancellation based on divergence minimization for MIMO-OFDM has been studied.In this paper, at the beginning, mobile wireless communication channels including three kinds of losses and four kinds of efforts have been introduced. Based on those, the broadband fading channel model has been described. Around MIMO system, OFDM system and MIMO-OFDM system, some basic knowledge and key technologies have been studied. Channel estimation is very important in mobile wireless communication and many research have been done about it. Then the channel estimation methods based on training sequences have been studied. The traditional channel estimation method like least square(LS) and minimum mean square error(MMSE) have been analyzed. According to the simulation result, the MMSE algorithm has quite well BER performance. At last, much attention has been put on an iterative channel estimation method based on minimizing Kullback- Leiblersfor divergence in MIMO-OFDM system. The theoretical formulas have been derived and simulation has been made. Simulation result shows that this iterative algorithm's BER performance is better than the one only use MMSE channel estimation method. |
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