Towards robust space-time coding

Summary form only given. In this paper, we investigate the robustness of space-time codes in line of sight and correlated Rayleigh fading channels. We develop the design criteria that govern the performance of space-time codes in these environments. Our analysis demonstrates that full diversity space-time codes are essential to achieving satisfactory performance in line of sight channels. We further show that a simple phase randomization approach achieves significant performance gains in the line of sight case without affecting the performance in Rayleigh fading channels. In the correlated fading environments, we characterize the achievable diversity order based on the number of diversity degrees of freedom in the channel. This characterization supports the recent experimental observations which suggest that the quasi-static model is not a worst case scenario, and establishes the necessary tradeoff between the transmission rate and performance robustness. Finally, we consider the design of space-time codes using some prior knowledge about the channel spatio-temporal correlation function.