Repetition time-switched transmit diversity as an alternative to Alamouti space-time coding for wireless communication systems

We present a simple transmit diversity technique, called repetition time-switched transmit diversity (R-TSTD), which is a modified version of the well-known time-switched transmit diversity (TSTD) algorithm. Throughout the paper, we focus on the scenario of a transmitter with n_T = 2 antennas. The idea behind R-TSTD is to use only one antenna at a time while still ensuring that all constellation symbols are transmitted via both antennas. Thus, unlike the classical TSTD technique, R-TSTD does provide a transmit diversity effect similar to that achieved with space-time coding (STC) algorithms. The error performance of the proposed R-TSTD system is compared to that of the Alamouti STC scheme via Monte Carlo computer simulations. It is shown that, in the absence of any outer error-correcting code, Alamouti STC slightly outperforms R-TSTD. However, when a near-capacity channel code is employed as an outer code, the error performance achieved using R-TSTD is significantly better than that obtained with Alamouti STC, provided that the desired spectral efficiency is sufficiently low.