Listen-and-Talk: Protocol Design and Analysis for Full-duplex Cognitive Radio Networks

TL;DR

This paper introduces a novel full-duplex based listen-and-talk protocol for cognitive radio networks, enabling simultaneous spectrum sensing and access, which improves spectrum utilization and throughput while addressing sensing accuracy issues.

Contribution

It proposes a new full-duplex listen-and-talk protocol that allows concurrent sensing and transmission, with analytical performance analysis and optimal power control strategies.

Findings

The protocol achieves better spectrum utilization compared to traditional methods.

A closed-form expression for spectrum waste and collision ratios is derived.

An optimal transmit power balancing throughput and sensing accuracy is identified.

Abstract

In traditional cognitive radio networks, secondary users (SUs) typically access the spectrum of primary users (PUs) by a two-stage "listen-before-talk" (LBT) protocol, i.e., SUs sense the spectrum holes in the first stage before transmitting in the second. However, there exist two major problems: 1) transmission time reduction due to sensing, and 2) sensing accuracy impairment due to data transmission. In this paper, we propose a "listen-and-talk" (LAT) protocol with the help of full-duplex (FD) technique that allows SUs to simultaneously sense and access the vacant spectrum. Spectrum utilization performance is carefully analyzed, with the closed-form spectrum waste ratio and collision ratio with the PU provided. Also, regarding the secondary throughput, we report the existence of a tradeoff between the secondary transmit power and throughput. Based on the power-throughput tradeoff, we derive the analytical local optimal transmit power for SUs to achieve both high throughput and satisfying sensing accuracy. Numerical results are given to verify the proposed protocol and the theoretical results.