An Iterative Receiver for Fast Fading Channels Using Two Kalman Filters

There is a demand for high data rate wireless communications over channels which are subject to both time selective and frequency selective fading. To obtain low error rate communications over these channels with the previously proposed channel estimation methods requires a large proportion of the transmitted signal to be dedicated to pilots and/or extensive computations in the radio receivers. This paper proposes a joint channel estimation and data detection system based on two Kalman filters. One Kalman filter is used to estimate the channel state while the second Kalman filter is used for signal equalization. An iterative procedure is used to allow for accurate data detection without requiring a high proportion of pilots. In each iteration of the receiver, the detected symbol sequence from the previous iteration is used as a virtual pilot signal to improve the accuracy of channel estimation. This paper demonstrates that this iterative receiver with two Kalman filters achieves an E_b/N₀ versus BER performance within 1 dB of radio receivers operating with ideal channel gain information in the presence of channel fading rates as high as 1% of the symbol rate. The computational cost of the proposed receiver algorithm is of the same order of magnitude as currently deployed receiver algorithms, making this algorithm feasible for implementation.