Robust detectors for cognitive radio system

Tõnu Trump,Imtiyaz Khan

doi:10.1186/s13638-015-0487-y

Abstract

Increasing demand for wireless technology overburdens the existing frequency spectrum due to the licensed spectrum management. On the other hand, field studies indicate that the spectrum is often underutilized. This leads to a need to reallocate the spectrum dynamically so that the unlicensed users could access the spectrum not required by the primary users. Dynamic spectrum access can be achieved by cognitive radio technology which in turn requires detection of primary user signals at the secondary user locations. In this paper, we investigate the detection of primary user signals in the environment with impulsive noise. We propose proper robust detectors to replace several popular detection schemes that have been developed for the Gaussian noise case. The basis of our development is modelling the noise as consisting of two components, one of them being Gaussian, which has proven itself as a good model for thermal noise, and the other being uniform, which appears with certain probability and models the impulsive noise. In this paper, several detectors arising from this model are proposed and analysed.

Highlights

Spectrum usage is regulated in every part of the world so that essential services can be provided and be protected from interference
The key enabler to this technology is reliable detection of spectral holes which could be used by the secondary users
Computing its maximum and minimum eigenvalues λmax and λmin, it is decided that the signal is present if T(x) = λmax/λmin > γ, where γ is the threshold of the test. It is demonstrated in [24] that based upon the theory of random matrices [25], one can obtain approximate expressions for the probability of false alarm and probability of detection of this detector if the noise is Gaussian

Summary

Introduction

Spectrum usage is regulated in every part of the world so that essential services can be provided and be protected from interference. If the impulsive noise is not present, we have only the Gaussian component and the max operator holds again For this result to hold, we have assumed that b − a is much larger than σ and much larger than any possible signal component in the received waveform. If we assume that the waveform is obtained via an analogue-to-digital converter operating in the range a < x(n) < b, we see that the Gaussian component gets limited, too Another interpretation of changing the summation with picking the one with the largest absolute value would be that if impulses are present, they replace the original samples as it would be in the case of A/D converter failures. We shall investigate these options closer in the sequel of the paper

Energy detector

Simulation results

Conclusions