Study On Channel Equalization For Wireless Communication Systems

In the wireless communication systems, the channel varies due to time, which effects the communication quality. The inter-symbol interference (ISI) because of multi-path fading is one of the important factors that lead to a high bit error rate. And the higher the data transmission speed is, the more severe ISI will be. The channel equalizers are often used in receivers to reduce the ISI. With the development of communication technology and higher quality demand, channel equalization is currently a hot and difficult research.The wireless communication systems contain single-carrier systems and multi-carrier systems. This paper researches the equalizer both in single-carrier systems and multi-carrier systems.This paper firstly discusses the background and meaning of the project, introduces the basic concepts and principles of the equalizer. In the single-carrier system equalization, the algorithms including LMS, NLMS, VLMS, DLMS and RLS are researched, and a novel variable step-size LMS algorithms based on decorrelation and a variable step-size NLMS algorithms based on decorrelation are proposed. The simulation results demonstrate that the algorithms proposed can achieve a faster convergence rate and a smaller mean square error (MSE), especially in the case of highly correlated input. RLS is faster than LMS, has better MSE and ability to track varying channel as is compared with LMS. Then, the principles and characteristics of OFDM are analyzed, and the algorithms for OFDM frequency domain equalization are researched, including LS and MMSE algorithms. The simulation results show that MMSE algorithm performs better than LS algorithm, but its computational complexity increases.