Transmission Design for Doppler- Varying Channels

Iterative receivers can provide excellent coding gain which allows performance close to channel capacity limits. Recent extensions of the basic iterative decoding strategy have enabled "front-end" receiver synchronisation tasks to be included in the iterative loop. However in channels with rapid phase and frequency variations, the lower signal to noise ratios of iterative systems may still pose significant synchronisation difficulties. This paper addresses a channel where Doppler offsets create specific challenges in a serial concatenated convolutional code (SCCC) system. New signal constellations and sub-block decoding techniques are proposed which overcome these problems.