Abstract
A cognitive radio (CR) device likely consists of a low-cost low noise amplifier (LNA) due to the mass-production reason. Nevertheless, the operation of a low-cost LNA becomes highly nonlinear causing intermodulation (IM) interference. The most important task of CR devices is to sense the wideband spectrum to increase opportunistic throughput. In noncooperative secondary networks, the IM interference usually can be ignored for the narrowband spectrum sensing, while the IM interference needs to be taken into account along with interference from other CR devices in the wideband case. Our contribution is to study the effects of a nonlinear LNA for the second case in environments modeled by Poisson field of interferers reflecting more realistic scenario. As shown in the simulation results, the performance of the receiver is degraded in all the cases due to the nonlinearity of LNA. The adaptive threshold setting based on the multivariate Gaussian mixture model is proposed to improve the receiver performance.
Highlights
The number of wireless devices is growing constantly
If we reduce the power of IM distortion (IMD) term to 2 dB, we obtain the receiver operating characteristic (ROC) curve as shown in Figure 4; the improvement in ROC curve is seen
We show the result at dPU = 500 m that shows that the results have the same trend when dPU varied
Summary
The number of wireless devices is growing constantly. One common reason is the increasing mobile penetration; that is, the costs of access and devices, for example, smart phones and tablets, are coming down. In [10] authors studied the effect of intranetwork interference in noncooperative environment assuming that the interfering signals are colocated spectrally which is good but it does not cover the situation where the interfering signal may be located on separate frequency bands It does not consider the effect of strong in-band interfering signal on the sensing node due to the nonlinearity of LNA in DCR. We model the interference in a wideband spectrum sensing at a particular subband by the IMD terms and due to the interfering signals from other CRs. The model presented provides more realistic viewpoint for studying the performance of detector in a noncooperative network that has not yet been studied in the literature.
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