SNR Threshold-Based Relay Association and Random Phase Rotation for Cooperative Communication

Abstract

In this study, a cooperative communication system that employs multiple decode-and-forward relay nodes (RNs), in which the associated/active RNs perform phase rotation of the regenerated signals before retransmitting them to a destination node (DN), is examined. In the first phase, i.e., communication from a source node to RNs, a received signal-to-noise ratio (SNR) threshold-based RN association method is proposed. The optimal SNR thresholds are designed to maximize the bit-error-rate (BER) performance at the DN under various communication environments, such as modulation types and channel code rates. Furthermore, the number of phase rotations (PRs) in a frame is examined. Intensive numerical results show that more PRs in a frame provide better BER performance at the DN, irrespective of the communication environments. This study provides a valuable guideline for designing practical cooperative networks with multiple decode-and-forward RNs with PRs.INDEX TERMS Cooperative communications, decode-and-forward relays, phase rotation, frame structure design.

Frequency Diversity Using Random Time Delay in Amplify-And-Forward Relay

“…The paper proposes a method for obtaining diversity gain in the AF method. In addition to the conventional method of gaining diversity by rotating the phase of the carrier [11][12][13][14], the paper introduces a new method for obtaining frequency diversity gain by applying a random time delay to the transmitted signal. The performance of the two methods when communicating in the orthogonal frequency division multiplexing (OFDM) method in a wideband is compared through simulation, and the results showed that the diversity gains due to time delay and the diversity gain due to phase rotation are similar.…”