Blind Equalization Research for the QOTDM System Based on HAPs Fading Channels
Lei Xie · Jisuanji fangzhen · 2009
A blind equalization algorithm for the Quasi-Orthogonal Time Division Multiplexed (QOTDM) system based on high altitude stratospheric platforms (HAPs) fading channel was proposed.At the transmitter,the transmitted signal with white frequency spectrum could be obtained based on the theory of QOTDM,and the receiver could get the sample sequences by filtering the received signal with a comb filter.The sample sequences were firstly equalized blindly by the modified constant modulus algorithm (MCMA),and the output of the primary equalizer was equalized by MCMA-FSE-DFE methods with very short length of weights.After the equalization,the inter symbol interference (ISI) could be cancelled.It is shown by Monte Carlo simulation that the new scheme can cancel the SER limit of QOTDM system in the HAPs fading channel.Under the same bit rate,and the same channel condition,when the Rice fading factor is 10dB,and SER is 10-3,the signalto-noise ratio of QOTDM is about 3.5dB lower compared with OFDM system,which is based on the DFT channel estimation arithmetic.