Research On Channel Estimation For OFDM Communication System Under S-Band Satellite Channel

OFDM technology had received widespread attention in academia and industry because of its unique advantages such as high spectrum efficiency and strong anti-interference ability. What's more, OFDM technology is widely used in today's land mobile/wireless communication system. At the same time, satellite communication has developed rapidly in recent years because some of its characteristics are better than other forms of communication. To develop the personal communication, the integration with land communication is an inevitable trend for the future development of satellite communication. On the other hand, due to the randomness of wireless channel, the signal will be interfered when pass the channel, the ability to get detailed channel information to demodulate the transmitted signal correctly is an important norm to measure the performance of a wireless communication system. Therefore, research on channel estimation is a significant work. So in this thesis, a mobile satellite communication system based on OFDM technique under the given parameters of the S-band satellite channel is designed and then a research on its channel estimation methods is did.Firstly the basic principles of OFDM technique and the common methods of channel estimation is introduced in this thesis, and some features of wireless channel is analyzed at the same time; Secondly the channel model is established based on the certain scenario and the characteristics and parameters of S-band satellite channel; Thirdly the physical layer parameters are designed and the number of sub-carriers is found out based on the influence of peak to average power ratio and adjacent channel interference as well as many other factors. Then the OFDM symbols, the frame structure and the system are designed.In the end a research on the channel estimation method is did for the completed system. Block pilot is selected after comparing the advantages and disadvantages of comb pilot and block pilot, then the classical least square algorithm and linear minimum mean square error algorithm is analyzed. However, the least square algorithm ignores the influence of noise, so the estimates is inaccurate, the computational complexity of linear minimum mean square error algorithm is high because it involves matrix inversion, so a suitable method is needed. The system in this thesis has narrow bandwidth and less sub-carriers and will be effected by noise strongly, so try to eliminate the influence of noise, a least square channel estimation algorithm after low-pass filter is given, the computational complexity of the algorithm is low and its bit error rate performance is good. In addition, the algorithm owns a good ability to compensate the residual frequency offset.