Joint Spectrum Sensing and Resource Allocation for OFDM-based Transmission with a Cognitive Relay

TL;DR

This paper presents joint spectrum sensing and resource allocation strategies for OFDM-based cognitive radio systems with a decode-and-forward relay, improving throughput and reducing interference despite sensing imperfections.

Contribution

It introduces a novel joint optimization framework for spectrum sensing and resource allocation in cognitive radio with relay, including optimal and sub-optimal schemes.

Findings

Proposed schemes outperform existing methods in throughput.

Relay-based cognitive radio achieves higher reliability and diversity.

Optimized power and subcarrier assignment reduce interference.

Abstract

In this paper, we investigate the joint spectrum sensing and resource allocation problem to maximize throughput capacity of an OFDM-based cognitive radio link with a cognitive relay. By applying a cognitive relay that uses decode and forward (D&F), we achieve more reliable communications, generating less interference (by needing less transmit power) and more diversity gain. In order to account for imperfections in spectrum sensing, the proposed schemes jointly modify energy detector thresholds and allocates transmit powers to all cognitive radio (CR) subcarriers, while simultaneously assigning subcarrier pairs for secondary users (SU) and the cognitive relay. This problem is cast as a constrained optimization problem with constraints on (1) interference introduced by the SU and the cognitive relay to the PUs; (2) miss-detection and false alarm probabilities and (3) subcarrier pairing for transmission on the SU transmitter and the cognitive relay and (4) minimum Quality of Service (QoS) for each CR subcarrier. We propose one optimal and two sub-optimal schemes all of which are compared to other schemes in the literature. Simulation results show that the proposed schemes achieve significantly higher throughput than other schemes in the literature for different relay situations.