Phase-Aligned Space-Time Coding for a Single Stream MIMO system

TL;DR

This paper introduces a phase-aligned space-time coding scheme for 3 and 4 transmit antennas that reduces performance penalties and achieves full diversity with minimal feedback, outperforming traditional open-loop coding.

Contribution

The paper proposes a novel phase-aligned coding scheme that extends Alamouti code to more antennas with minimal feedback, maintaining simple receiver architecture and improving performance.

Findings

Reduces performance penalty of orthogonal coding by up to 2 dB.

Achieves full diversity order of N_t with transparent receiver architecture.

Outperforms open-loop space-time coding by more than 3 dB for 3 and 4 antennas.

Abstract

We present a phase-aligned space-time coding scheme that expands the original Alamouti codeword to three or four transmit antennas ($N_t = 3$ or 4) with phase alignment. With $1 \sim 2$ bits feedback for the phase information, the fundamental performance penalty of $10log_{10}(N_t)$ dB of orthogonal space-time coding compared to the optimum beamforming is reduced by 1 dB (for $N_t=3$) or 2 dB (for $N_t = 4$) on average. With the proposed scheme, the full diversity order of $N_t$ is achievable, whereas the receiver architecture remains the same as the legacy Alamouti decoding with codeword size of two, since the spatial expansion is transparent to the receiver. Our results show the proposed scheme outperforms open-loop space-time coding for three or four transmit antennas by more than 3 dB.