Analysis of phase-sweeping multiantenna systems in slow fading channels

We investigate the effective temporal diversity property of a multiantenna system employing the phase sweeping transmit diversity (PSTD) scheme in a slow fading channel. We analyze how the number of transmit antennas used for phase sweeping and the sweeping frequency spacing affect the normalized time mean-square covariance (NTMSV) value which characterizes the temporal diversity of a channel. It is revealed that, in some situations, given the maximum sweeping frequency, there is an optimal antenna number that maximizes the temporal diversity, and the NTMSV can be used to find the optimal antenna number. Although the temporal diversity provided by PSTD is at the expense of the spatial diversity, we show by analyzing the fundamental tradeoff between the spatial diversity and the temporal diversity that the overall diversity gain can be maintained when applying the PSTD technique. Numerical results show that, with low complexity receivers, the coded PSTD multiple antenna system is a promising candidate to exploit the possible diversity in slow fading channels.