Distributed Space-Time Coding Based on Adjustable Code Matrices for Cooperative MIMO Relaying Systems

TL;DR

This paper introduces an adaptive distributed space-time coding scheme for cooperative MIMO networks that uses adjustable code matrices and feedback to improve performance, with algorithms that reduce complexity and eliminate feedback.

Contribution

It proposes a novel adaptive DSTC scheme with adjustable code matrices and develops algorithms for distributed implementation without feedback.

Findings

Significant performance improvements over existing DSTC schemes.

Effective algorithms with reduced computational complexity.

Validation through simulations demonstrating enhanced error performance.

Abstract

An adaptive distributed space-time coding (DSTC) scheme is proposed for two-hop cooperative MIMO networks. Linear minimum mean square error (MMSE) receive filters and adjustable code matrices are considered subject to a power constraint with an amplify-and-forward (AF) cooperation strategy. In the proposed adaptive DSTC scheme, an adjustable code matrix obtained by a feedback channel is employed to transform the space-time coded matrix at the relay node. The effects of the limited feedback and the feedback errors are assessed. Linear MMSE expressions are devised to compute the parameters of the adjustable code matrix and the linear receive filters. Stochastic gradient (SG) and least-squares (LS) algorithms are also developed with reduced computational complexity. An upper bound on the pairwise error probability analysis is derived and indicates the advantage of employing the adjustable code matrices at the relay nodes. An alternative optimization algorithm for the adaptive DSTC scheme is also derived in order to eliminate the need for the feedback. The algorithm provides a fully distributed scheme for the adaptive DSTC at the relay node based on the minimization of the error probability. Simulation results show that the proposed algorithms obtain significant performance gains as compared to existing DSTC schemes.