Multislot Simultaneous Spectrum Sensing and Energy Harvesting in Cognitive Radio

Xin Liu,Xuemai Gu,Zhenyu Na,Xiaotong Li,Min Jia

doi:10.3390/en9070568

Xin Liu, Xuemai Gu + Show 3 more

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https://doi.org/10.3390/en9070568

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Abstract

In cognitive radio (CR), the spectrum sensing of the primary user (PU) may consume some electrical power from the battery capacity of the secondary user (SU), resulting in a decrease in the transmission power of the SU. In this paper, a multislot simultaneous spectrum sensing and energy harvesting model is proposed, which uses the harvested radio frequency (RF) energy of the PU signal to supply the spectrum sensing. In the proposed model, the sensing duration is divided into multiple sensing slots consisting of one local-sensing subslot and one energy-harvesting subslot. If the PU is detected to be present in the local-sensing subslot, the SU will harvest RF energy of the PU signal in the energy-harvesting slot, otherwise, the SU will continue spectrum sensing. The global decision on the presence of the PU is obtained through combining local sensing results from all the sensing slots by adopting “Or-logic Rule”. A joint optimization problem of sensing time and time splitter factor is proposed to maximize the throughput of the SU under the constraints of probabilities of false alarm and detection and energy harvesting. The simulation results have shown that the proposed model can clearly improve the maximal throughput of the SU compared to the traditional sensing-throughput tradeoff model.

Highlights

To improve the current spectrum utilization, cognitive radio (CR) has been proposed to allow a secondary user (SU) to access the spectrum licensed to the primary user (PU), providing that the PU is not occupying the spectrum [1,2]
It is seen g g g that Pf and Pd have the same monotonicity, which indicates that the spectrum access decreases as Pd g g improves and the maximal throughput can be obtained if Pd acquires its lower limit; Pf decreases as ρ increases, which indicates that the maximal spectrum access can be achieved if ρ acquires its upper limit
R improves as τ increases, because the spectrum sensing performance mainly improves; when τ is large, R decreases as τ increases, because the data transmission time mainly decreases

Summary

Introduction

To improve the current spectrum utilization, cognitive radio (CR) has been proposed to allow a secondary user (SU) to access the spectrum licensed to the primary user (PU), providing that the PU is not occupying the spectrum [1,2]. To avoid causing harmful interference to the PU, the SU should detect whether the PU exists in the frequency band depending on performing spectrum sensing before any available transmissions. If the absence of the PU is detected, can the SU access the PU spectrum for its transmission [3,4]. The spectrum sensing performance is reflected by the probabilities of false alarm and detection. Decreasing false alarm probability improves the spectrum access of the SU, while increasing detection probability reduces the interference to the PU [5]. Increasing sensing time may improve the sensing performance but decrease the transmission time, it is important to develop a Energies 2016, 9, 568; doi:10.3390/en9070568 www.mdpi.com/journal/energies

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