Overlapped Alamouti Codes

In most of the existing space-time code designs, achieving full diversity is based on maximum-likelihood (ML) decoding at the receiver that is usually computationally expensive and may not have soft outputs. In this paper, we propose a novel family of space-time block codes (STBC) that achieves full diversity with a linear receiver, specifically, zero-forcing (ZF) or minimum mean square error (MMSE) receiver. Our newly proposed STBC are constructed by overlapping the 2times2 Alamouti code and hence named overlapped Alamouti codes. The new codes are close to orthogonal while their symbol rates can approach 1 for any number of transmit antennas. Simulation results show that overlapped Alamouti codes outperform orthogonal STBC (OSTBC) when the number of transmit antennas is above 4.