Fast Kalman Equalization for Time-Frequency Asynchronous Cooperative Relay Networks With Distributed Space-Time Codes

Cooperative relay networks are inherently time and frequency asynchronous due to their distributed nature. In this correspondence, we propose a transceiver scheme to combat both time and frequency offsets for cooperative relay networks with multiple relay nodes. At the relay nodes, a distributed linear convolutive space-time coding is adopted, which has the following advantages: 1) Full cooperative diversity can be achieved using a minimum mean square error (MMSE) or MMSE decision feedback equalizer (MMSE-DFE) detector, instead of a maximum-likelihood receiver when only time asynchronism exists. 2) The resultant equivalent channel possesses some special structure, which can be exploited to reduce the equalization complexity at the destination node. By taking full advantage of such a special structure, fast Kalman equalizations based on linear MMSE and MMSE-DFE are proposed for the receiver, where the estimation of the state vector (information symbols) can be recursively taken and become very computationally efficient, compared with direct equalization. The proposed scheme can achieve considerable diversity gain with both time and frequency offsets and applies to frequency-selective fading channels.