Space-time focusing transmission in ultra-wideband cooperative relay networks

Space-time focusing transmission is a generalized form of beamforming in ultra-wideband (UWB) systems by exploiting the unique feature of UWB signals. It can obtain energy gain and can reduce interference to coexisting users, thus can extend the distance and increase the capacity of UWB communications. Cooperative relay can further extend the coverage of UWB systems. In this paper, we first propose ZF and MMSE prefiltering algorithms for space-time focusing transmission, and then propose a space-time focusing based cooperative relay scheme. The throughputs of broadcast mode and multiple access mode in the relay networks are derived, while their dependency on various system parameters is obtained. Numerical results show how many cooperative nodes are necessary to maximize the network throughput, and when the proposed prefiltering algorithms perform well.