Research Of Channel Simulation And Channel Estimation In OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique. Currently, because of nice ability against multipath interference and high bandwidth efficiency, OFDM is concerned by the field of communication, being regarded as an important component in the fourth generation mobile communication technique. The channel property of frequency selective fading and Doppler frequency shift are the biggest challenge to the broadband mobile communication service. So it is significant to set up a sophisticated channel model for simulation of mobile communication system. If want to improve system performance by using OFDM, some concerned key-techniques must be studied. Channel estimation technique is one of such techniques. Only estimate channel first, signal detecting would be completed so that achieve communications.Firstly, we analysis the basic structure of OFDM and its advantages. Secondly, we study the modeling methods of multipath fading channel, and then set up a simulation model of Rayleigh multipath fading channel. Thirdly, we analysis some important channel estimation algorithms, such as LS (Least Square), LMMSE (Linear Minimum Mean Square Error) and simplified LMMSE algorithm.A simulation platform of OFDM system with Rayleigh multipath fading channel is also designed in this thesis. Based on this platform, we gain mach valuable simulation information. By comparison of theory equation, we find that the channel model we set up can reflect the real circumstance of wireless communication. We analysis the impact of the channel, based on typical city six path model, on OFDM system, and provide some information for further improvement. In addition, we analysis the performance of different channel estimation algorithms, and give some methods to reduce the negative impacts on the whole system cased by Rayleigh channel.