Secure Multiuser Communications in Wireless Sensor Networks with TAS and Cooperative Jamming

In this paper, we investigate the secure transmission in wireless sensor networks (WSNs) consisting of one multiple-antenna base station (BS), multiple single-antenna legitimate users, one single-antenna eavesdropper and one multiple-antenna cooperative jammer. In an effort to reduce the scheduling complexity and extend the battery lifetime of the sensor nodes, the switch-and-stay combining (SSC) scheduling scheme is exploited over the sensor nodes. Meanwhile, transmit antenna selection (TAS) is employed at the BS and cooperative jamming (CJ) is adopted at the jammer node, aiming at achieving a satisfactory secrecy performance. Moreover, depending on whether the jammer node has the global channel state information (CSI) of both the legitimate channel and the eavesdropper's channel, it explores a zero-forcing beamforming (ZFB) scheme or a null-space artificial noise (NAN) scheme to confound the eavesdropper while avoiding the interference to the legitimate user. Building on this, we propose two novel hybrid secure transmission schemes, termed TAS-SSC-ZFB and TAS-SSC-NAN, for WSNs. We then derive the exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput of both schemes to characterize the secrecy performance. Using these closed-form expressions, we further determine the optimal switching threshold and obtain the optimal power allocation factor between the BS and jammer node for both schemes to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for both schemes. Numerical results are provided to verify the theoretical analysis and illustrate the impact of key system parameters on the secrecy performance.This work was supported by the National Science Foundation of China (No. 61501507), and the Jiangsu Provincial Natural Science Foundation of China (No. BK20150719). The work of Nan Yang is supported by the Australian Research Council Discovery Project (DP150103905)

Secrecy Enhancement of Multiuser MISO Networks Using OSTBC and Artificial Noise

In this paper, we propose a novel physical layer strategy to improve the secrecy performance of multiuser multiple-input single-output networks. In this strategy, orthogonal space-time block code (OSTBC) is employed at an AAantenna base station (BS) and artificial noise (AN) is employed at an AJ-antenna cooperative relay to enhance the security level of the network. Moreover, two opportunistic scheduling schemes, namely, selection combining (SC) and scan-and-wait combining (SWC), are leveraged to select one legitimate user for data transmission. To evaluate the secrecy performance of the proposed OSTBC-SC-AN and OSTBC-SWC-AN schemes, we derive new exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput. Using numerical results, we show that the OSTBC-SWC-AN scheme outperforms the OSTBC-SC-AN scheme when the switching threshold is carefully chosen. We also show that increasing AA brings down the secrecy performance in the presence of a high switching threshold.ARC Discovery Projects Grant DP150103905

Experimental investigation on dynamic behaviour of heavy-haul railway track induced by heavy axle load

The damage to the track structure and the influence to the line deformation have greatly deteriorated with the increase of the axle load compared with that of the ordinary trains. However, there is a paucity of experimental research on the dynamic influence of the heavier haul freight trains on the railway tracks. The objective of this study is to investigate the dynamic behaviour of heavy-haul railway track induced by heavy axle load by field experimental tests. The wheel–rail dynamic force, the track structure dynamic deformation and the track vibration behaviour are measured and analysed when the train operates in the speed range from 10 to 75 km/h and the axle load of vehicles varies from 21 to 30 t. Comparisons between the results for the axle conditions of 25 and 30 t are made in this paper to reveal the axle load effects. It is demonstrated that part of the indicators reflecting the dynamic behaviour of the railway track increases approximately linearly with the train running speed and axle load, while others are influenced negligibly

Performance analysis of dual-hop satellite relay networks with hardware impairments and co-channel interference

Abstract In this paper, we investigate the impact of hardware impairments on the outage performance and the instantaneous capacity of dual-hop decode-and-forward (DF) satellite relay networks in the presence of co-channel interference. Specifically, the exact closed-form expression for the outage probability and the analytical expression for the instantaneous capacity of the system are derived over a shadowed-Rician fading channel, which provides a fast means to evaluate the impact of hardware impairments on the system performance. Our results demonstrate that the outage floor occurs and the capacity upper bound appears when the hardware impairments exist. In addition, simulation results were provided to verify the correctness of the analytical results

On the Performance of Cognitive Satellite-Terrestrial Relay Networks with Channel Estimation Error and Hardware Impairments

This paper investigates the joint impact of channel estimation errors (CEEs) and hardware impairments (HIs) on the performance of a cognitive satellite-terrestrial relay network (CSTRN), where the terrestrial and satellite links are considered following Rayleigh fading and shadowed Rician (SR) fading distributions, respectively. Besides, the terrestrial relay is working in half-duplex decode-and-forward (DF) mode. By employing a general and practical model to account for both the CEEs and HIs at each link, the end-to-end signal-to-noise-plus-distortion-and-error ratio (SNDER) is first obtained for the CSTRN. Then, closed-form expressions for the outage probability (OP) and throughput of the CSTRN are obtained, which allows us to demonstrate the aggregate impact of CEEs and HIs. In order to gain insightful findings, we further elaborate on the asymptotic OP and throughput at the high signal-to-noise-ratio (SNR) condition and quantitatively determine the fundamental performance ceiling. Finally, Monte Carlo (MC) computer simulations are provided to verify the correctness of the analytical results. Besides, with representative numerical analysis’s help, interesting findings are presented

Secure Multiuser Scheduling in Downlink Dual-Hop Regenerative Relay Networks Over Nakagami- mm Fading Channels

In this paper, we investigate the secrecy performance of multiuser dual-hop relay networks where a base station (BS) communicates with multiple legitimate users via the assistance of a trustful regenerative relay in the presence of multiple eavesdroppers. Particularly, the maximal ratio transmission (MRT) scheme is exploited at the BS and a threshold-based multiuser scheduling scheme is employed over the legitimate users, while concerning the imperfect decoding at the regenerative relay. To evaluate the secrecy performance of the considered system, two practical situations are addressed based on the availability of eavesdropper’s channel state information (CSI), i.e., Scenario I, where the eavesdropper’s CSI is not available at the relay, and Scenario II, where the eavesdropper’s CSI is available at the relay. For both scenarios, we further consider two eavesdropping modes, i.e., colluding eavesdropping and non-colluding eavesdropping. For Scenario I, new exact and asymptotic closed-form expressions of the secrecy outage probability (SOP) are derived. For Scenario II, we derive new exact and asymptotic closedform expressions of ergodic secrecy rate (ESR). The asymptotic SOPs demonstrate that the secrecy diversity order is independent of the number of legitimate users NB and eavesdroppers NE, the number of antennas equipped at eavesdroppers AE as well as fading factor of the wiretap channel mE. Furthermore, we also determine the secrecy multiplexing gain and the power cost to explicitly quantify the impact of the legitimate channel and wiretap channel on ergodic secrecy rate. Our findings demonstrate that increasing the switching threshold, the number of antennas at the BS, and the number of legitimate users have a positive impact on secrecy performance