Fast Channel Estimation For OFDM-CDMA Systems

OFDM-CDMA is a technology that combines OFDM and CDMA. It inherits the anti-multipath fading ability of OFDM technology as well as the high user capacity of CDMA. However, the OFDM-CDMA system is vulnerable to channel estimation errors in fast varying channels. Hence, this paper focuses on fast channel estimation algorithms for OFDM-CDMA receivers. We use comb pilots to estimate the channel response, and propose a low-complexity discrete Fourier transform based MMSE channel estimator. After the system has been synchronized, we first use the Least Square method to make channel estimation, then separate the channel response information from the channel noises by DFT. A weighting function based on the Minimum Mean Square Error (MMSE) criteria can be applied to the time domain channel impulse response. Analysis and simulation results show that this algorithm has much lower complexity and is able to track the fast time varying channels in time. With such two advantages, this algorithm can efficiently adopt wireless fast varying channels and successfully achieve the fast channel estimation for OFDM-CDMA systems.