Enhancement of Equal Gain Combiner for Detection of Spectrum Hole in a Cognitive Radio System

Ojo S I,Ojo F K,Adeyemo Z K,Adedeji A A,Semire F A

doi:10.13189/ujeee.2020.070503

Abstract

Cognitive Radio System (CRS) is of paramount importance in wireless communication for spectrum management. However, channel impairment affects accurate Spectrum Hole Detection (SHD) in CRS resulting in harmful interference to a licensed user. Conventional Equal Gain Combiner (EGC) which is one of the techniques being used to solve the problem suffers from hardware complexity resulting in high Sensing Time (ST). Hence, in this paper, an Enhanced EGC (EEGC) for SHD in a CRS is proposed to reduce the hardware complexity of conventional EGC. Ten thousand (10,000) bits are randomly generated, modulated using Binary Phase Shift Keying (BPSK) scheme and propagated over Rayleigh fading channel. The received signals through three antennas are scanned by three Selection Combiners (SCs) to select the branch with highest Signal to Noise Ratio (SNR). The outputs of the three SCs are then combined using conventional EGC. The output of conventional EGC is used as input to single Energy Detector (ED) to determine the energy of the combined signal. A mathematical expression for Probability of False Alarm (PFA) for the proposed technique is derived using X2 distribution to set thresholds at 0.01 and 0.02. The proposed technique is simulated using MATLAB software and evaluated using Probability of Detection (PD), ST and Probability of Missing (PM). The results obtained show that EEGC gives better performance with lower ST, higher PD and lower PM.

Highlights

Wireless Communication (WC) is the exchange of information between two or among many points through an unbounded environment
The results obtained reveal that, the proposed Enhanced EGC (EEGC) has a better performance with lower Probability of Missing (PM) value than the conventional Equal Gain Combiner (EGC) due to Selection Combiners (SCs) that is first applied to select signal with highest Signal to Noise Ratio (SNR) before applying EGC
Results obtained reveal that, PM values reduce as SNRs increase for the two techniques and this is due to performance of Energy Detector (ED) that reduces as SNR increases

Summary

Introduction

Wireless Communication (WC) is the exchange of information between two or among many points through an unbounded environment. In 1999, Mitola proposed a technique known as Cognitive Radio Networks (CRNs) that overcome spectrum scarcity [1, 2]. Cognitive Radio (CR) is a WC technique in which a transceiver intelligently senses the spectral environment over a wide frequency band to detect unused spectrum and provide wireless links through the unused spectrum [3, 4]. LUs are authorized users who have the precedence to use the assigned spectrum, while ULUs are unauthorized users who are allowed to make use of assigned spectrum only when LU is not present [5, 6, 7, 8]

Methods

Results

Conclusion