Practical Considerations on Channel Estimation for Up-Link MC-CDMA Systems

Channel parameters, which are usually estimated at the receiver, are required in signal detection in multi-carrier (MC) code division multiplex access (CDMA). The accuracy of channel estimation directly affects the performance of the overall system. In this paper, we present some practical techniques to improve channel estimation in up-link MC-CDMA systems. For most of multipath channels, there are only a few significant taps in time domain that determine the frequency response. Based on this characteristic, we detect and keep these significant taps and discard the trivial ones, which are usually very noisy or contain only noise components. After channel parameters are estimated at the pilot blocks, channels at the data blocks can be obtained by interpolation. To improve the performance of simple linear interpolation, we apply optimal interpolation, which takes channel estimation error and channel correlation into consideration. We then investigate the impact of channel estimation error on minimum mean-square-error (MMSE) successive interference cancellation (SIC) detector and find that more accurate channel is required to further improve the performance of the MMSE SIC detector. Therefore, we develop soft-decision-directed (SDD) channel estimation, which exploits the information at the data blocks to improve channel estimation.