55 research outputs found
Countering Eavesdropping Using Cognitive Radio - A New Perspective on Spectrum Sharing
No full textUnderutilized spectrum is wasteful.
Eavesdropping compromises the secrecy of data. We propose
single solution for the two problems - an eavesdropping-proof
spectrum sharing model. Cognitive radio (CR) is introduced to
share channel access with the primary user (PU). When PU is
sensed to be idle, CR utilizes the unoccupied channel for its data
transmission. When PU begins transmission, CR fends off
potential eavesdropper by sending a jamming signal. A concern
is CR’s energy efficiency, the ratio of its throughput to energy
consumption. Countering the intuition of high sampling rate
being better, we reveal that a low sampling rate (e.g. 1 MHz)
could be equally energy efficient
Sensing Criteria of TV White Space Devices under Nakagami-Rice Fading
No full textUnderutilized TV bands that constitute “TV
white space (TVWS)” are now open for utilization by other
telecommunication services. Spectrum regulator requires the
new white space device (WSD) not interfering with the existing
digital TV (DTV) service. This paper determines the
conditions necessary for harmonious coexistence between the
two. The main concern is the sensing WSD (SWSD) that
utilizes only spectrum sensing to determine the presence of
DTV service. Accuracy of sensing becomes very critical. Here
we represent the sensing accuracy by the probability of
detection PrD, whereas the probabilities of miss detection PrM
and false alarm PrF are indicators of sensing inaccuracy. We
investigate PrD, PrM, and PrF of an energy detector, a simple
spectrum sensor. Key sensing criteria are the required signalto-noise power ratio (γ) and the number of energy samples (N).
Our objective is to evaluate the effect of Nakagami-Rice fading
on γ and N for the Integrated Services Digital Broadcasting -
Terrestrial (ISDB-T) service. Under a typical fading scenario,
the required N is found to be nearly 20 times larger than when
fading is absent
Handover Management In Mobile Satellite Systems
No full textTwo handover management strategies have been proposed to efficiently manage the channel resource of a cell in a mobile satellite system (MSS) and to improve its service quality by reducing the handover failure rate and drop call rate caused by insufficient number of communication channels
Interference analysis of cognitive radio networks
No full textIn spite of spectrum sensing, aggregate interference from cognitive radios (CRs) remains as a deterring factor to the realization of spectrum sharing. We provide a systematic approach of evaluating the aggregate interference (Iaggr) experienced at a victim primary receiver. In our approach, we model the received power versus propagation distance relations between a primary transmitter, primary receiver, and CRs. Our analytical framework differs from the previous works in that we have formulated the relationship between Iaggr and the sensing inaccuracy of CRs. Energy detector is assumed for the purpose of spectrum sensing. Iaggr is expressed explicitly as a function of the number of energy samples collected (N) and the threshold signal-to-noise ratio level used for comparison (SNRε). The theoretical analysis is then applied to a practical scenario of spectrum sharing between digital TV broadcast and the IEEE 802.22 wireless regional area network systems. The impact on digital TV reception is evaluated in terms of signal-to-interference ratio. The proposed method allows us to determine the appropriate wireless regional area network operating conditions that fulfill the signal-to-interference ratio requirement imposed by regulator. Copyright © 2016 John Wiley & Sons, Ltd
Energy Efficiency of Cooperative Relay in a Spectrum Sharing Network
No full textAs underutilization of spectrum causes wastage, sharing spectrum between primary and secondary users is a possible solution. On the other hand, as hostile jamming corrupts data reception, having the secondary user to relay primary data introduces diversity, increasing the likelihood of receiving uncorrupted data. This paper proposes such spectrum sharing model that deploys physical layer security measure against jamming. A primary transmitter (PT) sends data to a primary receiver (PR). A cognitive radio transmitter (CT) relays PT's data to PR in return for spectrum access, i.e. CT uses the channel unoccupied by PT to send its own data. CT is capable of sensing the channel occupancy. Relaying data benefits PT, but to what extent it benefits CT? The main concern is CT's energy efficiency. In this paper, we find that there are optimal CT's transmission power and sensing duration that will result in optimal energy efficiency of CT, μ*. This work is novel in formulating an optimization method that finds μ* of a friendly relay (CT) that is part of a spectrum sharing network. We contribute the formula of finding the optimums under various scenarios: strong cognitive radio, sensing, jamming, and forwarding channels, and a powerful jammer. We find that (1) strong cognitive radio and sensing channels contribute positively towards μ*. (2) Although strong jamming channel, powerful jamming, and weak forwarding channel do not affect the energy efficiency of CT, they nevertheless deteriorate the capacity of the CT -PR forwarding channel under jamming
A spectrum sharing model that counters eavesdropping
No full textCybersecurity has become a major concern in the modern world. A serious threat to wireless networks is eavesdropping. On the other hand, usable spectrum is diminishing due to the presence of various wireless services. To address the problem, highly spectral efficient methods have been introduced e.g. spectrum sharing. Cognitive radio networks could sense unused spectrum and make use of it. In this paper, the cognitive radio is to perform a second task, i.e. jamming the eavesdropper. This paper is significant in revealing the cognitive radio’s energy efficiency in this setting, where a cognitive transmitter (CT) can transmit its own data when it senses the absence of primary transmitter (PT). If PT is present, CT is to jam an eavesdropper (EA) by transmitting artificial noise. Our main contribution is finding the CT’s optimal energy efficiency. Through the proposed formulas, we have determined the fractions of time and power required by CT to achieve the optimal energy efficiency, subject to constraints like minimum required secrecy rate Rs, etc. Our major findings are: (1) only a small portion of a time frame (66 μs in our setting) is required for sensing. CT can utilize the remaining time for sending its data or jamming EA. (2) To achieve a target energy efficiency of 0.5 bps/Hz/J, PT should not be actively transmitting more than 35% of the time, and Rs should not be larger than 1.2 bps/Hz
Wireless power transferable from unmanned aerial vehicle
No full textUnmanned aerial vehicle (UAV) could wirelessly transfer power to the devices on ground, thus recharging their batteries conveniently. Nevertheless, the efficiency of this wireless power transfer from UAV to ground remains unclear. This paper aims to answer this question from the theoretical perspective. We need two models for this purpose: an energy harnessing model and a UAV-to-ground wireless channel model. In the literature, a model of harnessing radio frequency (RF) energy and turning it into DC power is available. Our goal is to quantify the theoretical efficiency of RF-to-DC power conversion, and the amount of DC power gained as a result. Following this nonlinear energy harvesting circuit model, the signal level fluctuations caused by channel fading actually enhance the power conversion. To model the wireless channel gain from the UAV to the ground, we use the modified Loo’s channel model. Connecting it to the RF-to-DC power conversion model, we can determine the theoretical amount of DC power attainable from UAV’s transmission, in addition to its power conversion efficiency. Our finding shows that a heavy shadowing condition can enhance the RF-to-DC power conversion of a nonlinear energy harvesting circuit. For example, certain heavy shadowing condition may yield a conversion efficiency that is 7 dB higher than when shadowing is absent. This concurs with the previous finding that signal attenuation and fluctuation actually made the energy easier to be captured and harnessed by the nonlinear rectenna circuitry. Our finding confirms that high RF-to-DC conversion efficiency is attainable even under shadowing conditions
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