Spectrum Monitoring Using Energy Ratio Algorithm For OFDM-Based Cognitive Radio Networks

TL;DR

This paper introduces an energy ratio algorithm for OFDM-based cognitive radios that quickly detects primary user reappearance by monitoring changes in signal strength, reducing sensing frequency and detection delay.

Contribution

The paper proposes a novel energy ratio algorithm that enhances primary user detection speed and accuracy in OFDM cognitive radios, accounting for OFDM impairments and channel effects.

Findings

Effective detection of primary user reappearance demonstrated through analysis and simulation.

High immunity to frequency-selective fading channels achieved.

Algorithm complexity is approximately twice that of conventional energy detectors.

Abstract

This paper presents a spectrum monitoring algorithm for Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radios by which the primary user reappearance can be detected during the secondary user transmission. The proposed technique reduces the frequency with which spectrum sensing must be performed and greatly decreases the elapsed time between the start of a primary transmission and its detection by the secondary network. This is done by sensing the change in signal strength over a number of reserved OFDM sub-carriers so that the reappearance of the primary user is quickly detected. Moreover, the OFDM impairments such as power leakage, Narrow Band Interference (NBI), and Inter-Carrier Interference (ICI) are investigated and their impact on the proposed technique is studied. Both analysis and simulation show that the \emph{energy ratio} algorithm can effectively and accurately detect the appearance of the primary user. Furthermore, our method achieves high immunity to frequency-selective fading channels for both single and multiple receive antenna systems, with a complexity that is approximately twice that of a conventional energy detector.