Distributed space-time block coding for cooperative diversity

Cooperative diversity is a scheme which allows a cluster of wireless terminals to collaborate by relaying signals for one another, and thus improve the link with an access point for all of them. Several such schemes have been proposed over the past few years, and have shown in theory that they could result in a remarkable improvement in performance. However there has been little work on the practical problems likely to be encountered in implementing such a scheme, such as synchronisation of the transmissions from the nodes and, not least, how the relaying will actually be implemented. This project will investigate practical implementation using a scheme based on space-time block codes, which are a very simple and effective way of implementing diversity transmission over multiple transmitting antennas. It will first investigate the effect of synchronisation and channel estimation errors on such a system, and then investigate practical ways to overcome these problems, using, for example, iterative decoding and estimation techniques. In a cooperative diversity system the diversity is provided by exploiting multiple routes through a network of single-antenna terminals, rather than multiple antennas on a single terminal. The programme will also investigate a more general model of this approach, based on the concepts of network coding, which could provide more efficient cooperative diversity schemes in the future.