Pilot based adaptive channel estimation and tracking in uplink MC-CD MA using Kalman filter

The paper presents pilot symbol aided adaptive channel estimation for uplink multicarrier code division multiple access (MC-CDMA) systems operating in fast fading channels. Channel impulse responses of active users are estimated periodically taking the assistance of pilot blocks. Time variations of channel coefficients between two successive pilot blocks are tracked using Kalman filtering method. Implementation of the Kalman filter in uplink requires the prior knowledge of channel statistics of different multipath channels corresponding to the different active users. In practice, true channel statistics are unknown at receiver, therefore, appropriate assumptions are made regarding the channel statistics in order to determine Kalman parameters. We examine the performance of an uplink MC-CDMA system employing minimum mean-square error (MMSE) and parallel interference canceller - MMSE (PIC-MMSE) MUDs using adaptive channel estimation. It has been found that the proposed method can efficiently track the channel variation up to high fade rates.