Cooperative Transmission for Wireless Relay Networks Using Limited Feedback

TL;DR

This paper introduces a low-feedback cooperative transmission scheme for wireless relay networks that achieves high diversity and robustness with low complexity, leveraging channel statistics and extended coding techniques.

Contribution

It proposes a simple, low-rate feedback approach for maximum diversity, incorporating power loading and an extended Alamouti code for robustness and no-CSI scenarios.

Findings

Achieves near-optimal error probability with low complexity

Enhances robustness against feedback errors

Generalizes to differential transmission without CSI

Abstract

To achieve the available performance gains in half-duplex wireless relay networks, several cooperative schemes have been earlier proposed using either distributed space-time coding or distributed beamforming for the transmitter without and with channel state information (CSI), respectively. However, these schemes typically have rather high implementation and/or decoding complexities, especially when the number of relays is high. In this paper, we propose a simple low-rate feedback-based approach to achieve maximum diversity with a low decoding and implementation complexity. To further improve the performance of the proposed scheme, the knowledge of the second-order channel statistics is exploited to design long-term power loading through maximizing the receiver signal-to-noise ratio (SNR) with appropriate constraints. This maximization problem is approximated by a convex feasibility problem whose solution is shown to be close to the optimal one in terms of the error probability. Subsequently, to provide robustness against feedback errors and further decrease the feedback rate, an extended version of the distributed Alamouti code is proposed. It is also shown that our scheme can be generalized to the differential transmission case, where it can be applied to wireless relay networks with no CSI available at the receiver.