Research On Channel Estimation Techniques Of OFDM System

Wireless communication techniques are the hotspot at present in telecommunication area. The convenience and the reducing cost of the services stimulate the fast growth of mobile communications. Compared to the traditional mobile communications, the global researches and applications on broadband wireless access and transmission are becoming flourishing. The trend of communication may be that the band of mobile communication system is becoming broader, while the broadband communication system is becoming mobile system. The two systems above will be combined and integrated at last. As the growth of the wireless applications and the increasing need for middle and high speed packet services, the allocation of wireless frequency resources becomes a problem. So techniques with high spectral efficiency have been the hotspot in research. One of these techniques is OFDM.Channel estimation is the key technique to guarantee the transmission reliability of OFDM system. It has three processes as follows: design of the pilot pattern, channel estimation of pilot subchannels and the data subchannels. This dissertation illustrates the processes of channel estimation, analyzes the problem exists in the present communication systems which employs the fixed pilot patterns. Based on the analysis above, a new scheme of adaptive pilot pattern has been advanced. The scheme which adjusts the pilot pattern as the channel environment changes can improve the BER performance or transmission efficiency of OFDM system. In the dissertation, it also analyzes the problem of Gaussian interpolation algorithms. Then it introduces a new interpolation algorithm named balanced interpolation algorithm with four values. In general, the innovations of the dissertation are: 1. A new adaptive adjusting scheme of pilot pattern has been introduced. 2. A new interpolation algorithm has been put forward. The performance of the new scheme and algorithm above can be simulated by computer. And the simulation results show that the new scheme and algorithm both can improve the performances of the OFDM system.