Spatial multiplexing by spatiotemporal spreading of multiple symbol streams

The use of multiple transmitter and receiver antennas allows multiple signal streams to be transmitted in parallel and hence communication capacity to be increased. To distribute the multiple signal streams over the MIMO channel, linear space-time codes have been shown to be a convenient way to reach high capacity gains with a reasonable complexity. We propose an approach based on spatial spreading and delay diversity, hence spatiotemporal spreading, for channels with delay spread (frequential fading). The approach allows full symbol rate transmission (and hence full capacity) and permits full spatiotemporal diversity. The spatial spreading codes are optimized for minimum pairwise error probability (maximum coding gain). Some optimal and suboptimal receiver schemes are also discussed.