Space-time code design for unknown frequency-selective channels

The design of space-time codes has so far mostly focused on one-tap channel models while in this paper code design for multi-tap (frequency-selective) channels is discussed when joint channel estimation and data detection is used at the receiver. A transmission model using multiple transmitter and receiver antennas for multi-path propagation through unknown channels is presented and shown to be closely linked to a single-antenna model which has been investigated earlier. Using a randomized search strategy, codes of arbitrary rates for combined channel estimation and error protection over these channels can be designed. Simulations demonstrate the performance of codes designed with the proposed scheme. An example code outperforms an approach based on an extension of the Alamouti scheme.