Abstract

     Physical layer security (PLS) in Internet-of-Things (IoT) has attracted great attention in recent years. As an important and intrinsic property in an IoT system, node mobility is not fully investigated when designing a PLS scheme. Existing PLS works with mobility are designed with typical random mobile models, which cannot represent a real scenario. Considering this challenge, we propose a friendly jamming handover scheme to protect the downlink transmission from a controller to an actuator, with the help of multiple cooperative jammers to fight against a mobile conscious eavesdropper. In particular, we first introduce a conscious eavesdropping model (CEM) to characterize a real mobile wiretapping scenario. Second, we present a handover scheme to enhance security in a mobile scenario and then define handover efficiency to discuss the handover performance. Finally, numerical results are provided to verify the effectiveness of the proposed handover scheme, which demonstrates that our scheme can efficiently fight against a conscious mobile eavesdropper.

Introduction

     Internet of Things (IoT) is expected as a promising technique to achieve ubiquitous connectivity and intelligent information processing for the intelligent future life [1, 2]. Since the IoT is penetrating our daily life, the security and privacy are of the utmost importance [3–5]. Physical layer security (PLS) techniques have been attracted growing interests for the scenarios with resource-constrained IoT sensors and actuators [6–8]. A PLS scheme taking advantage of the unique properties of wireless channels can guarantee the information-theoretic communication security, regardless of the computing capability of eavesdroppers [9]. Various PLS schemes have been investigated to enhance secrecy in IoT networks, including multi-antenna beamforming and precoding [10, 11], artificial noise (AN) [12], intermittent cooperative jamming [13], and sociability-enabled PLS [8, 14, 15].

Conclusion

     This work investigated secure downlink transmmission in an IoT system with a mobile eavesdropper, and proposed a handover scheme to enhance PLS with the help of multiple cooperative jammers. In order to reflect the real situation, the conscious eavesdropping model was proposed to compare with the typical RWP model. Moreover, we introduced a metric called handover efficiency to reflect the handover performance. The numerical results verified that the handover scheme could efficiently improve the secrecy performance and effectively confront the conscious eavesdropper. The proposed scheme is feasible to provide security enhancement in many real mobile eavesdropping scenarios.

The escalating high data rate requirements have resulted in severe spectrum scarcity problem. Cognitive radio (CR) has emerged as one of the most effective solutions for improving the spectrum efficiency in wireless networks [1]. Among proposals for the implementation of CR, a spectrum-leasing framework whereby the primary users (PUs) lease spectral resources to secondary users (SUs) in exchange for cooperation has been proposed in [2]. In cooperative CR networks, SUs assist to relay the messages of PUs for accessing the same spectrum to send their own information to secondary receivers (SRs), which is a win-win strategy. That is particularly preferred by primary system when the primary system itself can not meet the quality of service (QoS) of the PU. One problem is that even when the SU has good channel quality to help relay the PU but is energy limited, cooperation is still unable to complete. This is a very common situation when the SU is a low-power relay node. Therefore, solving the problem of energy scarcity is very significant, especially for the CR network with energy-limited devices [3]. Simultaneous wireless information and power transfer (SWIPT), which enables the concurrent transmission of information and energy, has attracted much attention as a promising technology to solve the energy scarcity problem [4]. In [5], authors have proved that energy-limited secondary user (SU) with energy harvesting can be strongly stimulated in CR networks. On the other hand, due to the broadcast nature of wireless communications, security is always a major concern in wireless networks. PU also has the requirements of secure communication in CR networks, by reason of the existence of eavesdroppers causing the legitimate user information disclosure. Physical layer security as a promising way has been proposed to prevent eavesdropping [6]. Cooperation techniques for physical layer security, e.g., cooperative forwarding, friendly jamming, and beamforming [7], [8], have been presented to improve the secrecy rate. [9] and [10] have considered the physical layer security combined SWIPT in CR networks. In [9], the authors focus on designing artificial noise (AN)-aided beamforming for secure SU transmission. They assume SU powered by cognitive base station (CBS) can share the same spectrum with PU as long as the interference imposed on PU receiver is tolerable. The scene of [10] is similar to [9], the difference is that the SU harvests energy from PU but not CBS. Notice that in [9], [10], the PU allows the SU to access the licensed spectrum without requiring any benefit. Such altruistic behavior is arguably unrealistic.