When Does Relay Transmission Give a More Secure Connection in Wireless Ad Hoc Networks?

Relay transmission can enhance coverage and throughput, while it can be vulnerable to eavesdropping attacks due to the additional transmission of the source message at the relay. Thus, whether or not one should use relay transmission for secure communication is an interesting and important problem. In this paper, we consider the transmission of a confidential message from a source to a destination in a decentralized wireless network in the presence of randomly distributed eavesdroppers. The source-destination pair can be potentially assisted by randomly distributed relays. For an arbitrary relay, we derive exact expressions of secure connection probability for both colluding and non-colluding eavesdroppers. We further obtain lower bound expressions on the secure connection probability, which are accurate when the eavesdropper density is small. By utilizing these lower bound expressions, we propose a relay selection strategy to improve the secure connection probability. By analytically comparing the secure connection probability for direct transmission and relay transmission, we address the important problem of whether or not to relay and discuss the condition for relay transmission in terms of the relay density and source-destination distance. These analytical results are accurate in the small eavesdropper density regime.Comment: Accepted for publication in IEEE Transactions On Information Forensics and Securit

Secure Transmission Design With Feedback Compression for the Internet of Things

ARC Discovery Projects Grant DP150103905

A New Secure Transmission Scheme With Outdated Antenna Selection

We propose a new secure transmission scheme in the multi-input multi-output multi-eavesdropper wiretap channel. In this channel, the NA-antenna transmitter adopts transmit antenna selection (TAS) to choose the antenna that maximizes the instantaneous signal-to-noise ratio (SNR) at the receiver to transmit, while the NB-antenna receiver and the NE-antenna eavesdropper adopt maximal-ratio combining (MRC) to combine the received signals. We focus on the practical scenario where the channel state information (CSI) during the TAS process is outdated. In this scenario, we propose a new transmission scheme to prevent the detrimental effect of the outdated CSI on the wiretap codes design at the transmitter. To thoroughly assess the secrecy performance achieved by the proposed scheme, we derive new closed-form expressions for the exact secrecy outage probability and the probability of non-zero secrecy capacity for arbitrary SNRs. We also derive new compact expressions for the asymptotic secrecy outage probability at high SNRs. Notably, in the analysis we take spatial correlation at the receiver into consideration. Apart from the advantage of our scheme over the conventional TAS/MRC scheme, we demonstrate that the outdated TAS reduces the secrecy diversity order from NANB to NB. We also demonstrate that antenna correlation improves the secrecy performance at low SNR but deteriorates the secrecy performance at medium and high SNRs, by affecting the secrecy array gain only.ARC Discovery Projects Grant DP150103905

Artificial-Noise-Aided Secure Transmission Scheme With Limited Training and Feedback Overhead

We design a novel artificial-noise-aided secure onoff transmission scheme in a wiretap channel. We consider a practical scenario where the multi-antenna transmitter only obtains partial channel knowledge from the single-antenna receiver through limited training and feedback but has no channel knowledge about the single-antenna eavesdropper. In the design, we first propose a three-period block transmission protocol to capture the practical training and quantization features. We then characterize the statistics of the received signal-to-noise ratios (SNRs) at the receiver and the eavesdropper. Under the secrecy outage constraint, we exploit the on-off scheme to perform secure transmission and derive a closed-form expression for the secrecy throughput. Moreover, we investigate the optimization problem of maximizing the secrecy throughput by proposing an iterative algorithm to determine the optimal power allocation between the information signal and artificial noise, as well as the optimal codeword transmission rate. Furthermore, we define the net secrecy throughput (NST) which takes the signaling overhead into account and address the problem of optimally allocating the block resource to the training and feedback overhead. Numerical results clearly demonstrate how the optimal signaling overhead changes with the number of transmit antennas, and there exists an optimal number of antennas that maximizes the NST.ARC Discovery Projects Grant DP15010390

On–Off-Based Secure Transmission Design With Outdated Channel State Information

We design new secure on-off transmission schemes in wiretap channels with outdated channel state information (CSI). In our design we consider not only the outdated CSI from the legitimate receiver but two distinct scenarios, depending on whether or not the outdated CSI from the eavesdropper is known at the transmitter. Under this consideration our schemes exploit the useful knowledge contained in the available outdated CSI, based on which the transmitter decides whether to transmit or not. We derive new closed-form expressions for the transmission probability, the connection outage probability, the secrecy outage probability, and the reliable and secure transmission probability to characterize the achievable performance. Based on these results, we present the optimal solutions that maximize the secrecy throughput under dual connection and secrecy outage constraints. Our analytical and numerical results offer detailed insights into the design of the wiretap coding parameters and the imposed outage constraints. We further show that allowing more freedom on the codeword transmission rate enables a larger feasible region of the dual outage constraints by exploiting the trade-off between reliability and security.ARC Discovery Projects Grant DP15010390