Quasi-Orthogonal STBC With Minimum Decoding Complexity

TL;DR

This paper introduces a quasi-orthogonal space-time block code with minimal decoding complexity, providing systematic construction, optimal constellation rotation, and demonstrating advantages over existing codes in power distribution and scalability.

Contribution

It proposes a new MDC-QO-STBC with simplified decoding, optimal constellation rotation, and improved scalability and power distribution over prior orthogonal designs.

Findings

Maximum likelihood decoding requires joint detection of only two real symbols.

Achieves full diversity and optimal coding gain with proper constellation rotation.

Offers higher code rate and better scalability compared to existing codes.

Abstract

In this paper, we consider a quasi-orthogonal (QO) space-time block code (STBC) with minimum decoding complexity (MDC-QO-STBC). We formulate its algebraic structure and propose a systematic method for its construction. We show that a maximum-likelihood (ML) decoder for this MDC-QOSTBC, for any number of transmit antennas, only requires the joint detection of two real symbols. Assuming the use of a square or rectangular quadratic-amplitude modulation (QAM) or multiple phase-shift keying (MPSK) modulation for this MDC-QOSTBC, we also obtain the optimum constellation rotation angle, in order to achieve full diversity and optimum coding gain. We show that the maximum achievable code rate of these MDC-QOSTBC is 1 for three and four antennas and 3/4 for five to eight antennas. We also show that the proposed MDC-QOSTBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes. For the case of an odd number of transmit antennas, MDC-QO-STBC also has better decoding performance than CIOD.