Fast Kalman Equalization for Cooperative Relay Networks with Both Time and Frequency Offsets

Cooperative relay networks are inherently time- and frequency- asynchronous due to their distributed nature. The existence of multiple time and frequency offsets results in a time-varying and frequency-selective equivalent channel between relay nodes and destination node. In this paper, we propose a transceiver scheme to combat both time and frequency offsets for cooperative relay networks. At the relay nodes, the distributed linear convolutive space-time coding is adopted to achieve the time-asynchronous full cooperative diversity. This transmission scheme leads to an equivalent channel with special structure at the destination node. By taking full advantage of this special structure, fast Kalman equalizations based on linear minimum mean square error (LMMSE) and MMSE decision feedback equalizers (MMSE-DFE) are proposed for the receiver, where the estimation of the state vector (information symbols) can be operated recursively and computational efficiently. The proposed scheme can achieve considerable diversity gain with both time and frequency offsets, and also applies to frequency-selective fading channels.