Efficiency Improvement for Alamouti Codes

In this paper, an approach to improve the code efficiency of Alamouti codes is proposed for high data rate communications over multiple-antenna channels. Unlike most of the existing methods which are designed to achieve full-rate and/or full-diversity, we aim at increasing the spectral efficiency. The proposed scheme carries more information bits in each transmission block than the Alamouti code does and still allows maximum likelihood decoding for sub-streams to be decoupled at the receiver. Simulation results also indicate that the full transmit diversity is retained with the improvement of code efficiency. Although the case of two transmit antennas is the main focus of this paper, the same idea can be directly applied to Alamouti codes with more than two transmit antennas.