This paper presents an artificial noise strategy to increase physical-layer security in Cognitive Wireless Sensor Networks (CWSN). Spectrum sensing, information sharing and collaborative cognitive features are used to avoid eavesdropping attacks. Artificial noise generation is proposed to conceal the secret message to be transmitted. One important design parameter, the ratio of power allocated to the information bearing signal versus the artificial noise Φ is defined. A simulation framework has been used to simulate different scenarios. The simulations results show that there is a near-optimal Φ value, from 0.8 until 0.96 depending on the number of collaborator nodes, increasing with the number of relay nodes in the network. Also, the simulations show that the more nodes used for the collaboration strategy the less noise per signal is needed for the same Secrecy Outage Probability. As a result, the artificial noise strategy is seen to be highly effective for increasing the secrecy in CWSN.
This paper presents an artificial noise strategy to increase physical-layer security in Cognitive Wireless Sensor Networks (CWSN). Spectrum sensing, information sharing and collaborative cognitive features are used to avoid eavesdropping attacks. Artificial noise generation is proposed to conceal the secret message to be transmitted. One important design parameter, the ratio of power allocated to the information bearing signal versus the artificial noise Φ is defined. A simulation framework has been used to simulate different scenarios. The simulations results show that there is a near-optimal Φ value, from 0.8 until 0.96 depending on the number of collaborator nodes, increasing with the number of relay nodes in the network. Also, the simulations show that the more nodes used for the collaboration strategy the less noise per signal is needed for the same Secrecy Outage Probability. As a result, the artificial noise strategy is seen to be highly effective for increasing the secrecy in CWSN.
A simple scheme to guarantee zero secrecy outage in an overlay cognitive radio network is proposed with the aid of Artificial Noise (AN). The secrecy outage probability and the condition on the secrecy rates to achieve zero secrecy outage will be determined. Our scheme shows that the transmission between the transceivers will be secured toward the eavesdropper with zero outages. This means that the message can always be secured by a simple strategy of transmission with the aid of AN. The optimum power allocation to information obtained to achieve the maximum zero-outage secrecy throughput will be highlighted. Importantly, the resulting maximum secrecy throughput increases with increasing transmit power, which overcomes the limit of traditional secret transmissions.
The applications of Wireless Sensor Networks (WSNs) are widespread in areas such as environmental monitoring, industrial automation, healthcare and smart infrastructures, where secure and reliable wireless communication is essential. The nature of a wireless channel, however, lends itself to the problem of eavesdropper-directed wireless sensor networking, interception and unauthorized access. This paper presents a secure physical layer communication system featuring the combination of channel estimator, physical layer key generator, artificial noise generator and adaptive power allocator to increase the confidentiality of physical layer communications and simultaneously achieve energy efficiency. A hybrid security mechanism is used, which takes advantage of the channel characteristics to create secret keys and to make the eavesdropper's signal reception worse by introducing controlled artificial noise. Key performance parameters considered for simulation-based evaluation are secrecy capacity, BER, PDR, Throughput, Energy consumption and Network lifetime. Results show that the secrecy capacity is 6.3 bps/Hz, the packet delivery ratio is 98.7%, the bit error rate is 10⁻⁶, and the network lifetime is 1675 rounds. The proposed framework is much more effective in terms of both communication security and energy efficiency than the traditional WSNs security schemes.
Motivated by recent developments in wireless communication, this thesis aims to characterize the secrecy performance in several types of typical wireless networks. Advanced techniques are designed and evaluated to enhance physical layer security in these networks with realistic assumptions, such as signal propagation loss, random node distribution and non-instantaneous channel state information (CSI). The first part of the thesis investigates secret communication through relay-assisted cognitive interference channel. The primary and secondary base stations (PBS and SBS) communicate with the primary and secondary receivers (PR and SR) respectively in the presence of multiple eavesdroppers. The SBS is allowed to transmit simultaneously with the PBS over the same spectrum instead of waiting for an idle channel. To improve security, cognitive relays transmit cooperative jamming (CJ) signals to create additional interferences in the direction of the eavesdroppers. Two CJ schemes are proposed to improve the secrecy rate of cognitive interference channels depending on the structure of cooperative relays. In the scheme where the multiple-antenna relay transmits weighted jamming signals, the combined approach of CJ and beamforming is investigated. In the scheme with multiple relays transmitting weighted jamming signals, the combined approach of CJ and relay selection is analyzed. Numerical results show that both these two schemes are effective in improving physical layer security of cognitive interference channel. In the second part, the focus is shifted to physical layer security in a random wireless network where both legitimate and eavesdropping nodes are randomly distributed. Three scenarios are analyzed to investigate the impact of various factors on security. In scenario one, the basic scheme is studied without a protected zone and interference. The probability distribution function (PDF) of channel gain with both fading and path loss has been derived and further applied to derive secrecy connectivity and ergodic secrecy capacity. In the second scenario, we studied using a protected zone surrounding the source node to enhance security where interference is absent. Both the cases that eavesdroppers are aware and unaware of the protected zone boundary are investigated. Based on the above scenarios, further deployment of the protected zones at legitimate receivers is designed to convert detrimental interference into a beneficial factor. Numerical results are investigated to check the reliability of the PDF for reciprocal of channel gain and to analyze the impact of protected zones on secrecy performance. In the third part, physical layer security in the downlink transmission of cellular network is studied. To model the repulsive property of the cellular network planning, we assume that the base stations (BSs) follow the Mat´ern hard-core point process (HCPP), while the eavesdroppers are deployed as an independent Poisson point process (PPP). The distribution function of the distances from a typical point to the nodes of the HCPP is derived. The noise-limited and interference-limited cellular networks are investigated by applying the fractional frequency reuse (FFR) in the system. For the noise-limited network, we derive the secrecy outage probability with two different strategies, i.e. the best BS serve and the nearest BS serve, by analyzing the statistics of channel gains. For the interference-limited network with the nearest BS serve, two transmission schemes are analyzed, i.e., transmission with and without the FFR. Numerical results reveal that both the schemes of transmitting with the best BS and the application of the FFR are beneficial for physical layer security in the downlink cellular networks, while the improvement due
The authors study the secure transmission design in random cognitive radio networks where the primary users, the secondary users and the eavesdroppers are randomly distributed according to Poisson point processes. Centring on this scenario, the authors propose a simple and decentralised secure transmission scheme by jointly incorporating the secrecy guard zone and artificial noise. In particular, this transmission scheme helps to enhance secrecy performance via differentiating between secondary transmitters in accordance with the eavesdropping environment. They then analyse the connection outage and secrecy outage performance of the secondary network, based on which they obtain the closed‐form expression of the secrecy throughput. They further determine the optimal transmission power of the secondary transmitters and the optimal power allocation between the information‐bearing signal and artificial noise to maximise the secrecy throughput of the secondary network under primary and secondary outage constraints. The authors’ analysis highlights that introducing secrecy guard zone provides better security performance, and artificial noise performs as additional interference to insert a control between the reliability and security. Numerical results show how the system parameters affect the achievable maximum secrecy throughput, the optimal transmission power and the optimal power allocation between the information‐bearing signal and the artificial noise.
Abstract Ensuring network security is of utmost importance, especially in wireless sensor networks (WSNs), where the confidentiality of data is at risk due to eavesdropping. This paper introduces an artificial‐noise‐aided secure communication scheme for WSNs. This scheme comprises numerous sensor nodes, the sink, a friendly jammer, and an eavesdropper. The primary aim is to enhance the secrecy rate of the network by optimizing the jamming power. The friendly jammer plays a crucial role in degrading the wiretap channel between the sensor nodes and the eavesdropper. The optimization process revolves around maximizing the secrecy rate, while carefully managing the jamming power to prevent any negative impact on the main transmission link between the sink node and the sensor nodes. Due to the nonconvexity of the secrecy rate problem, the convex approximation‐based algorithm is recommened to get a safe convex approximation of the original solution. To address this optimization problem, an iterative algorithm based on quadratic transformation is proposed. Afterwards, the optimum jamming power to achieve high security is obtained. The simulation outcomes underscore the dual impact of the jammer in WSNs. The jammer diminishes the eavesdropper channel. Unfortunately, it introduces interference that consequently affects the security enhancement. In response, we concentrate on the optimization of jamming power. The proposed scheme consistently elevates secrecy rates across a spectrum of eavesdropper positions, adeptly addressing worst‐case scenarios. Notably, the algorithm showcases resilience across diverse node distributions.
We present secrecy performance of a two-way communication (TWC) with a number of amplify and forward (AF) relays in a cognitive radio network (CRN) as well as TWC with the help of DF relays. A TWC with multiple untrusted half-duplex AF relays is set up in an underlay CRN where two sources are not directly connected due to shadowing and path loss. In this cognitive network, two sources share their information to each other over two phases via an intermediate relay selected among multiple AF relays. A power-splitting scheme based energy harvesting from radio frequency signal is considered at the relay. Further, the AF relays are untrusted and eavesdrops the message also. Due to the CRN, the transmit power of the transmitting nodes are controlled under the cognitive constraints such as outage probability threshold of the primary network. Further, the TWC is analyzed with DF relays where an external eavesdropper eavesdrops the message from both the sources but not simultaneously. We have evaluated the physical layer security (PLS) through a metric known as secrecy outage probability (SOP). We have derived SOP in closed-form expression and presented in for both the scenarios of investigations. The analytical results, based on the closed-form expression, are justified by the MATLAB-based simulation results. We observe that PLS increases with an increase in the number of relays, primary network transmit power, and transmit power of the cognitive device. In TWC with DF relays, an optimal value of transmit power of a source and fraction of supply power to the relay are obtained at which secrecy performance is maximized.