Recently, the use of artificial noise has attracted considerable attention in enhancing the physical-layer security of wireless systems. However, the interaction between artificially generated noise and the inherent network interference can significantly affect the level of secrecy. In this paper, we consider the additional secrecy enhancement with artificial noise and secrecy protected zone in the presence of eavesdroppers and interferers with unknown locations. Specifically, we derive the secrecy transmission rate and investigate the relationship between artificial noise and various system parameters like secrecy protected zone radius and intensity of interferers and eavesdroppers on the secrecy transmission rate. In interference-limited networks, we derive the optimal power allocation between the information-bearing signal and artificial noise to maximize the achievable secrecy transmission rate subject to connection and secrecy outage probabilities. Numerical results show that artificial noise is still beneficial in the presence of inherent network interference to improve secrecy transmission rate and provide rules of thumb to quantify when optimal power allocation is useful.
Recently, the use of artificial noise has attracted considerable attention in enhancing the physical-layer security of wireless systems. However, the interaction between artificially generated noise and the inherent network interference can significantly affect the level of secrecy. In this paper, we consider the additional secrecy enhancement with artificial noise and secrecy protected zone in the presence of eavesdroppers and interferers with unknown locations. Specifically, we derive the secrecy transmission rate and investigate the relationship between artificial noise and various system parameters like secrecy protected zone radius and intensity of interferers and eavesdroppers on the secrecy transmission rate. In interference-limited networks, we derive the optimal power allocation between the information-bearing signal and artificial noise to maximize the achievable secrecy transmission rate subject to connection and secrecy outage probabilities. Numerical results show that artificial noise is still beneficial in the presence of inherent network interference to improve secrecy transmission rate and provide rules of thumb to quantify when optimal power allocation is useful.
Network interference disturbs the legitimate receiver as well as eavesdroppers. Artificial noise transmission is able to indirectly control these negative and positive effects of interfering signals on secrecy communication, and thus improves the secrecy transmission rate. Contrary to the previous results presuming some prior information on eavesdroppers, this letter studies secrecy enhancement via the optimal use of an artificial noise without the knowledge related to eavesdroppers. We derive the optimal use of artificial noise with constraints for reliability and secrecy level and the corresponding secrecy transmission rate in the presence of network interference for the worst scenario.
Exploiting the randomness embedded in wireless channels, the physical-layer security techniques can provide additional security robustness against malicious eavesdropping at the physical layer of communication systems. To further this line of study, this thesis focuses on developing advanced multi-antenna transmission strategies for enhancing the secrecy performance of wireless communication systems. Assuming perfect channel feedback from the desired receiver and none from the eavesdropper, we consider beamforming with smartly injected artificial noise, aiming to confuse the eavesdropper whilst leaving the desired receiver unaffected. The system parameters are either chosen to be fixed for all transmissions, or adaptively adjusted based on the channel feedback from the desired receiver. For both cases, we provide novel and explicit design solutions for achieving the maximum throughput subject to a secrecy outage constraint. We then derive accurate approximations for the maximum throughput, and give new insights into the additional power cost for achieving a higher security level and the throughput gain of adaptive transmission over non-adaptive transmission. Having investigated the perfect feedback scenario, we then relax the feedback assumption and consider practical effects imposed by limited feedback constraints on the channel from the desired receiver to the transmitter. To deal with quantization error due to limited feedback whilst also accounting for unknown channel of the eavesdropper, we specify a connection outage constraint to guarantee the reliability of desired communication and a secrecy outage constraint to guard against malicious eavesdropping. Under dual outage constraints, we derive a novel optimized rate-adaptive transmission design to maximize the average secrecy throughput. New insights regarding the optimal power/feedback allocation and the number of feedback bits required for efficient quantization are obtained through our analysis. Our preceding study focused on isolated point-to-point transmission without any interference. However, the performance of contemporary wireless networks is often limited by interference from concurrent transmissions. To characterize the impact of interference on secure communication, we consider an interference-limited large-scale network. To confuse the malicious eavesdroppers, in addition to information-bearing signals, the transmitters are designed to generate artificial noise through either beamforming or antenna sectoring in a distributed manner. For both cases, using tools from stochastic geometry, we provide a statistical characterization of the reliability performance of desired communication and the secrecy performance against eavesdropping. We then investigate the networkwide secrecy throughput performance and optimize the transmit power allocation. Our analysis reveals interesting differences between the beamforming and sectoring approaches in terms of the optimal power allocation and the maximum networkwide secrecy throughput.
In this paper, we investigate physical-layer security in a random wireless network where both legitimate and eavesdropping nodes are randomly deployed. In the first scenario, we study the basic random network without a protected zone around the source node. The probability density functions (pdfs) for the composite channel gain with both fading and path loss is derived and used to calculate the probability of secure connection and ergodic secrecy capacity. In the second scenario, we consider the use of secrecy protected zone around the source node to enhance the security in a noise-limited network. Here, we study the following two cases: 1) The eavesdroppers are aware of the secrecy protected zone, and 2) the eavesdroppers are unaware of the secrecy protected zone. Moreover, the distribution of the distances between the origin and random nodes outside the secrecy protected zone is derived. In the final scenario, the interferer protected zones around the legitimate receivers are used to improve the physical-layer security by restructuring the interference. The derived analytical results are verified by the Monte Carlo simulations. It is shown that the application of secrecy and interferer protected zones lead to significant improvement in security, depending on different system parameters.
In this paper, we investigate physical layer security in a random wireless network where both legitimate and eavesdropping nodes are randomly deployed.In the first scenario, we study the basic random network without a protected zone around the source node.The probability density functions (PDF) for the composite channel gain with both fading and path loss is derived and used to calculate the probability of secure connection and ergodic secrecy capacity.In the second scenario, we consider the use of secrecy protected zone around the source node to enhance the security in a noise limited network.Here we study the two cases (i) the eavesdroppers are aware of the secrecy protected zone; (ii) the eavesdroppers are unaware of the secrecy protected zone.Moreover, the distribution of the distances between the origin and random nodes outside the secrecy protected zone is derived.In the last scenario, the interferer protected zones around the legitimate receivers are used to improve the physical layer security by restructuring the interference.The derived analytical results are verified by the Monte Carlo simulations.It is shown that the application of secrecy and interferer protected zones lead to significant improvement in the security depending on different system parameters.
This paper investigates cooperative security in wireless networks, where a source (Alice) intends to transmit a confidential message to a legitimate destination (Bob), with the help of a cooperative jammer (Charlie), coexisting with multiple passive eavesdroppers (Eves). In particular, by assuming knowledge of Bob's perfect channel state information (CSI) but only Eves’ statistical CSIs, secrecy beamforming with artificial noise (AN) is utilized for secure transmission, and cooperative jamming (CJ) is explored to further enhance secrecy. We first derive an accurate closed-form expression for the secrecy outage probability (SOP), and establish the condition under which positive secrecy rate is achievable. Then, we provide a secure transmit design for maximizing the SOP constrained secrecy rate. Moreover, based on a strict mathematical analysis, we characterize the impact of the main channel quality and the number of Eves on transmit design and secrecy performance. Specifically, optimal power allocation ratio between the information-bearing signal and the AN signal increases as the main channel quality improves, and decreases with the number of Eves. Numerical results confirm that our design achieves performance improvement in terms of both secrecy rate and secure energy efficiency, as compared to the approach without CJ.
In this paper, we combine sectorized transmission with artificial noise to establish secrecy in decentralized wireless networks. The locations of the legitimate nodes and the eavesdroppers are both modeled by homogeneous Poisson point processes. Using sectorized antennas, each legitimate transmitter sends an information signal in the sector which contains its intended receiver, while simultaneously emitting artificial noise in other sectors, in order to provide secrecy against the eavesdroppers. We first separately characterize the reliability performance of the legitimate link and the secrecy performance against malicious eavesdropping. Then, we derive the secrecy transmission capacity to measure the networkwide secrecy throughput. To facilitate the practical system design, we provide a sufficient condition, in terms of the system parameters and constraints, under which a positive secrecy transmission capacity is achievable. The optimal transmit power allocation between the information signal and the artificial noise for achieving the maximal secrecy transmission capacity is also investigated. Our analysis indicates that sectorized transmission provides significant secrecy enhancements in decentralized wireless networks.