Research On Channel Estimation Algorithm In Transform Domain For Optical OFDM System

OFDM technology as a high spectrum efficiency can be effective against frequency selective fading and time dispersion, etc. And this technology can provide high-speed and high-quality communication services. So we pay more and more attention to this technology. At the same time, a large number of studies show that OFDM has a high tolerance to chromatic. Combined OFDM with optical communication technology, we can construct a kind of high rate, low cost and long distance optical transmission network, it is considered as a promising enabling technology in the further. The channel estimation technology is one of the key technologies of optical OFDM, and accurate channel estimation is crucial to ensure the transmission quality of O-OFDM. This paper research on channel estimation algorithm in transform domain for optical OFDM.This paper introduces the basic principles of OFDM system, the key technology and its advantages and disadvantages, also introduces DDO-OFDM system, CO-OFDM system and OFDM-RoF system. We get ready for researching on the channel estimation algorithm by building simulation models of CO-OFDM and OFDM-RoF.(1) LS algorithm based on block pilot when the impact of the neglect of the noise, making estimation difficult to obtain good estimation performance. To solve this problem, we propose a wavelet de-noising algorithm. Wavelet de-noising technique is applied to the LS channel estimation algorithm to solve the flaw of the neglect of the noise. And it analyses the impact on channel estimation algorithm in different decomposition and wavelet. Simulation results demonstrate the effectiveness of the proposed algorithm.(2) The conventional DFT algorithm will be effected by additional high frequency component generated by IDFT. The improved algorithm can eliminate additional high frequency component, also selects the useful paths by calculating the changing rate of the energy to make the algorithm better. Combine wavelet de-noising and improved DFT algorithm, it can eliminate the noise in the useful paths and make the performance of the algorithem better. Simulation in DDO-OFDM and OFDM-RoF system results demonstrate the effectiveness of the proposed algorithm.