Frequency-domain equalization using iterative channel estimation for high-speed transmission with cyclic-prefix MC-DS-CDMA

This paper presents frequency-domain equalization (FDE) using iterative channel estimation for high-speed transmission with cyclic-prefix multicarrier direct sequence spread spectrum CDMA (MC-DS-CDMA). Cyclic-prefix DS-CDMA simplifies many issues arising in receiver due to the high-speed transmission, such as delay-spread of the channel. It also reduces the complexity of the equalizer and enables the equalization in frequency domain. With pilot-aided channel estimation and OFDM-style cyclic prefixes, a frequency-domain MMSE equalizer achieves the suppression of multipath interference. Yet the accuracy of channel estimation restricts the performance of the equalizer. In order to acquire more accurate channel estimation, an iterative algorithm is presented in this paper. Simulation results show, with the employment of this algorithm, the performance of the frequency-domain equalizer has a significant improvement. Compared to the original RAKE receiver with severe interference, after 5 iterations, the SNR of despread signals is enhanced by about 13 dB. This higher SNR can satisfy the requirement of demodulator and decoder, and support the full usage of Walsh codes and high order modulation as well.