We investigate the spectrum sharing possibility as an incentive to enhance the physical layer security. The concept behind is that a legitimate source-destination pair, communicating in the presence of a passive eavesdropper, stimulates the help of another source-destination nodes looking for transmission opportunities, referred to as secondary network (SN). We thus propose a cooperative scheme, whereby the secondary transmitter (ST) will act as a friendly jammer to confound the eavesdropper and be granted to share the spectrum of the legitimate pair, referred to as primary network (PN), as a reward. Meanwhile, the ST has to secure its own secrecy communication and thus exploit the impact of the induced interference by the PN. To evaluate the performance of our cooperative scheme, we derive the closed-form expressions of the secrecy outage probability (SOP) for both cooperative networks. However, to assess its usefulness, we introduce the mutual outage probability (MOP) and we carry out analysis to derive its expression. We show that a satisfactory SOP is a necessary condition for triggering the cooperation, whereas a satisfactory MOP is a sufficient condition to guarantee that the PN-SN collaboration leads to a win-win situation. Furthermore, an asymptotic analysis is also carried out to derive the generalized secrecy diversity for the scheme under investigation, where it has been shown that the primary system achieves its full secrecy diversity order, equal to the number of antenna at the primary transmitter. Such results present useful insights for practical design and setups.
We investigate the spectrum sharing possibility as an incentive to enhance the physical layer security. The concept behind is that a legitimate source-destination pair, communicating in the presence of a passive eavesdropper, stimulates the help of another source-destination nodes looking for transmission opportunities, referred to as secondary network (SN). We thus propose a cooperative scheme, whereby the secondary transmitter (ST) will act as a friendly jammer to confound the eavesdropper and be granted to share the spectrum of the legitimate pair, referred to as primary network (PN), as a reward. Meanwhile, the ST has to secure its own secrecy communication and thus exploit the impact of the induced interference by the PN. To evaluate the performance of our cooperative scheme, we derive the closed-form expressions of the secrecy outage probability (SOP) for both cooperative networks. However, to assess its usefulness, we introduce the mutual outage probability (MOP) and we carry out analysis to derive its expression. We show that a satisfactory SOP is a necessary condition for triggering the cooperation, whereas a satisfactory MOP is a sufficient condition to guarantee that the PN-SN collaboration leads to a win-win situation. Furthermore, an asymptotic analysis is also carried out to derive the generalized secrecy diversity for the scheme under investigation, where it has been shown that the primary system achieves its full secrecy diversity order, equal to the number of antenna at the primary transmitter. Such results present useful insights for practical design and setups.
We investigate the spectrum sharing possibility as an incentive to enhancing the physical layer security. The concept behind this is that a legitimate source-destination pair, communicating in the presence of a passive eavesdropper, stimulates the help of another source-destination node looking for transmission opportunities, referred to as secondary network (SN). We thus propose a cooperative scheme, whereby the secondary transmitter will act as a friendly jammer to confound the eavesdropper and be granted to share the spectrum of the legitimate pair, referred to as primary network (PN), as a reward. To evaluate the performance of our cooperative scheme, we derive the closed-form expression of the secrecy outage probability (SOP). However, to assess its usefulness, we introduce the mutual outage probability (MOP) and we carry out analysis to derive its expression. We show that a satisfactory SOP is a necessary condition for triggering the cooperation, whereas a satisfactory MOP is a sufficient condition to guarantee that the PN-SN collaboration leads to a win-win situation. Results have been presented considering outdated channel state information, thus giving more insights for practical setups.
ABSTRACT In this paper, we propose a 6‐node system consisting of two transmitter‐receiver pairs sharing the same spectrum, an eavesdropper, and a relay, all operating in a half‐duplex. The eavesdropper is mainly interested in communication between one of the transmitter‐receiver pairs, which we call the primary. Communication along with the second pair called the secondary, is performed in two hops/time slots with the aid of the relay. The main idea of our study is to investigate the secrecy performance of the primary pair when jamming is performed by the secondary relay‐assisted path. In particular, in the first time slot, the secondary destination acts as a jammer relative to the eavesdropper by injecting artificial noise known to the primary pair. During the second time slot, the secondary transmitter acts as a jammer while the relay forwards data to the secondary destination. In effect, this allows for cooperation among the nodes both in transmitting primary and secondary data while reducing the eavesdropper's ability to listen in on the primary link communication. For the proposed protocol, we derive closed‐form expressions of the intercept probability. We also obtain a closed‐form expression of the outage probability along with the secondary communication link. Moreover, we study the effect of transmit power allocation on intercept and outage probabilities along with the different links. Theoretical and simulation results are given to prove that the proposed protocol can provide better security for the primary link and acquire acceptable secondary outage probability.
This paper investigates the physical layer secrecy performance for an underlay wiretap spectrum sharing network with optimal relay and antenna selection (ORAS). It jointly selects a transmit antenna at a secondary source, a receive antenna at its destination, and a relay between them to maximize the secrecy rate at the destination under a passive eavesdropping scenario. We derive novel, exact expressions for secrecy outage probability (SOP) and secrecy throughput (ST) in a single integral-form. We also provide their accurate approximations in closed-form. Considering three distinct scenarios depending on whether the main link is stronger than the wiretap link and the nature of the primary interference constraint, we obtain different useful system design insights. Under a proportional interference constraint, secrecy diversity gain is achieved only when the main link is stronger than the wiretap link, otherwise the diversity gain is lost and leads to an SOP floor. Under a fixed interference constraint, the SOP floor is further increased. Through numerical results, we show the impact of different signal combining strategies by the eavesdropper on the SOP and ST. We also illustrate the efficacy of the ORAS scheme as compared to other relay and antenna selection schemes.
In this paper, we examine the physical-layer security for a spectrum sharing system consisting of multiple source-destination pairs, which dynamically access their shared spectrum for data transmissions in the presence of an eavesdropper. We propose a source cooperation (SC) aided opportunistic jamming framework for protecting the transmission confidentiality of the spectrum sharing system against eavesdropping. Specifically, when a source node is allowed to access the shared spectrum for data transmissions, another source is opportunistically selected in the spectrum sharing system to transmit an artificial noise for disrupting the eavesdropper without affecting the legitimate transmissions. We present two specific SC aided opportunistic jamming schemes, namely the SC aided random jammer selection (RJS) and optimal jammer selection (OJS), which are referred to as the SC-RJS and SC-OJS, respectively. We also consider the conventional non-cooperation as a baseline. We derive closed-form intercept probability expressions for the non-cooperation, SC-RJS and SC-OJS schemes, based on which their secrecy diversity gains are determined through an asymptotic intercept probability analysis in the high signal-to-noise ratio (SNR) region. It is proved that the conventional non-cooperation exhibits a secrecy diversity of zero, whereas the proposed SC-RJS and SC-OJS achieve a higher secrecy diversity of one. This also surprisingly means that no additional secrecy diversity gain is achieved by the optimal jammer selection compared to the random selection strategy. In addition, numerical results show that the intercept probability performance of the SC-OJS is always better than that of the SC-RJS and non-cooperation, even when the legitimate channel is worse than the eavesdropping channel.
We study the physical-layer security of multiple source-destination (SD) pairs communicating within a wireless network in the face of an eavesdropper attacking the SD pairs. In order to protect the wireless transmission against eavesdropping, we propose a cooperation framework relying on two stages. Specifically, an SD pair is selected to access the total allocated spectrum using an appropriately designed scheme at the beginning of the first stage. The other source nodes (SNs) simultaneously transmit their data to the SN of the above-mentioned SD pair relying on orthogonal resources during the first stage. Then, the SN of the chosen SD pair transmits the data packets containing its own messages and the other SNs' messages to its dedicated destination node (DN) in the second stage. Finally, this dedicated DN will forward all the other DNs' data to the application center via the core network. We conceive a specific SD pair selection scheme, termed as the transmit antenna selection aided source-destination pair selection (TAS-SDPS). We continue by deriving the secrecy outage probability (SOP) expressions of both the TAS-SDPS conceived, as well as of the conventional round-robin source-destination pair selection (RSDPS) and of the conventional non-cooperative (Non-coop) schemes for comparison. Furthermore, we carry out the secrecy diversity gain analysis in the high main-to-eavesdropper ratio (MER) region, showing that the TAS-SDPS scheme is capable of achieving the maximum attainable secrecy diversity order. Additionally, we show that increasing the number of transmitting pairs will reduce the SOP, whilst increasing the secrecy diversity order of the TAS-SDPS scheme. It is demonstrated that the SOP of the TAS-SDPS scheme is better than that of the RSDPS and of the conventional Non-coop schemes. We also demonstrate that the secrecy diversity gain of the proposed TAS-SDPS scheme is M times that of the RSDPS scheme in the high-MER region, where M is the number of the SD pairs.
In this paper, the physical layer security of a dual-hop underlay uplink cognitive radio network is investigated over Nakagami-m fading channels. Specifically, multiple secondary sources (Si)1≤2≤Nare taking turns in accessing the licensed spectrum of the primary users and communicating with a multi-antenna secondary base station (D) through the aid of a multi-antenna relay R in the presence of M eavesdroppers (Ek)1≤k≤Mthat are also equipped with multiple antennas. Among the remaining nodes, one jammer is randomly selected to transmit an artificial noise to disrupt all the eavesdroppers that are attempting to intercept the communication of the legitimate links, i.e., Si-R and R-D. The received signals at each node are combined using maximum-ratio combining. Secrecy analysis is provided by deriving closed-form and asymptotic expressions for the secrecy outage probability. The impact of several key parameters on the system's secrecy, e.g., transmit power of the sources, number of eavesdroppers, maximum tolerated interference power, and the number of diversity branches is investigated. Importantly, by considering two scenarios, namely (i) absence and (ii) presence of a friendly jammer, new insights are obtained for the considered communication system. Especially, we tend to answer to the following question: Can better secrecy be achieved without jamming by considering a single antenna at eavesdroppers and multiple-ones at the legitimate users (i.e., relay and end-user) rather than sending permanently an artificial noise and considering that both the relay and the destination are equipped with a single antenna, while multiple antennas are used by the eavesdroppers? The obtained results are corroborated through Monte Carlo simulation and show that the system's security can be enhanced by adjusting the aforementioned parameters.