A wireless communication aided with Cooperative Jamming in order to enhance Physical Layer security is modeled with Game Theory, using Secrecy Capacity as payment function. To completely take in account the inherent randomness of the wireless channel, a Second Order Cone Programming deterministic equivalent is derived from the game resulting probabilistic optimization problem. Results show how upper and lower bounds of the secrecy capacity, associated to the game values, can be used to characterize the system. Suggested mixed strategies are implemented and compared with pure strategies, and it's shown that performance of mixed strategies, in terms of outage probability, lays exactly between the performances of pure strategies.
A wireless communication aided with Cooperative Jamming in order to enhance Physical Layer security is modeled with Game Theory, using Secrecy Capacity as payment function. To completely take in account the inherent randomness of the wireless channel, a Second Order Cone Programming deterministic equivalent is derived from the game resulting probabilistic optimization problem. Results show how upper and lower bounds of the secrecy capacity, associated to the game values, can be used to characterize the system. Suggested mixed strategies are implemented and compared with pure strategies, and it's shown that performance of mixed strategies, in terms of outage probability, lays exactly between the performances of pure strategies.
A wireless communication aided with CooperativeJamming in order to enhance Physical Layer security is modeledwith Game Theory, using Secrecy Capacity as payment function.To completely take in account the inherent randomness of thewireless channel, a Second Order Cone Programmingdeterministic equivalent is derived from the game resultingprobabilistic optimization problem. Results show how upper andlower bounds of the secrecy capacity, associated to the gamevalues, can be used to characterize the system. Suggested mixedstrategies are implemented and compared with pure strategies,and it’s shown that performance of mixed strategies, in terms ofoutage probability, lays exactly between the performances of purestrategies.
Physical layer (PHY) security (PLS) leverages the inherent randomness of wireless fading channels to provide enhanced secrecy capacity. In this work, we consider a four-node, dual hop, eavesdropper-aware cooperative PHY-security model. Considering probabilistic relay selection and relaying in the presence of hybrid fading channels, we develop an insightful analysis for the probability of PHY-secrecy capacity outage (PSCO) and PHY-secrecy efficiency outage (PSEO). Specifically, we derive closed form expressions for these performance measures and evaluate them numerically to obtain valuable qualitative insights. We also develop an insightful comparative study to show that the cooperative PLS relay model having a destination node equipped with multiple antennas and performing selection combining delivers superior PHY-secrecy outage performance. We extend the analysis to the reconfigurable intelligent surface (RIS)-assisted cooperative PLS system. Specifically, we address the design problem of N, the number of reflecting elements in RIS. We develop insightful criteria based on secrecy capacity to derive a closed form lower bound on N. This insightful result provides the values of N that could achieve superior PHY-secrecy capacity than the relay-assisted cooperative PLS system. Our analysis of the former cooperative PLS model and its extension to RIS design is useful for next generation cooperative PLS relay and RIS-assisted wireless systems and networks.
The growth of wireless networks has been considerable over the last decades. Due to the broadcast nature of these networks, security issues have taken a critical role in today’s communications. A promising direction towards achieving secure communications is information theoretic secrecy, which is an approach exploiting the randomness of the channels to ensure secrecy. Based on this approach, there has been a recent surge of interest in a potential cooperation between users to enhance the secrecy of communications. In this thesis we investigate the interaction between cooperation and secrecy. In particular the contributions of the thesis can be divided into two parts. In the first part, we study cooperative strategies for secrecy for wireless channels. Our goal is to evaluate the effect of fading and limited CSI on the eavesdropper’s channels. In that purpose we consider a scenario where a helper aims at increasing the secrecy of the communication between a source and destination in the presence of an eavesdropper. Several strategies are discussed for the helper, namely decode-and-forward, amplify-and-forward, and cooperative jamming. We introduce the secrecy outage probability, the conditional secrecy outage probability and the secure throughput as secrecy measures. For each measure, we investigate and compare the secrecy performance of cooperation. We furthermore elaborate a system optimization in terms of strategy selection, node positioning, power allocation and rate design. In the second part, we consider cooperation in the 4-node scenario against a more sophisticated adversary: an active eavesdropper, which can either passively eavesdrop, or jam the transmission. A game-theoretic perspective is a natural way to analyze the competitive interaction between the helper and the eavesdropper. Therefore we define several secrecy games, for which we find the Nash and Stackelberg equilibria as well as the corresponding secrecy rate outcomes. Another important consideration in this scenario is the interaction between the source and the helper, which we model and solve as a Stackelberg game, and we illustrate its impact on the achievable secrecy rates.
The open nature of the wireless networks makes them vulnerable to the eavesdropper attacks. Cooperative relay transmission is a popular method to prevent the attacks of the illegal nodes. This research proposes a cooperative jamming protocol to enhance the physical layer in wireless cooperative networks, where the destination sends a jamming signal to the eavesdropper node to degrade its channel capacity. Simulations of the secrecy performance metrics in terms of the secrecy capacity and secrecy outage probability are presented and discussed to measure the security level of the proposed jamming protocol. In this paper, different channels namely Rician fading, Rayleigh fading, and Additive White Gaussian Noise (AWGN) channels are investigated in the half-duplex two-way relaying system to obtain the maximum secrecy performance. Based on the results, the highest secrecy capacity is achieved by using the Rician fading channel for transmission from the source to the destination and using the Rayleigh channel as the jamming link to degrade the eavesdropper capacity.
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 open nature of the wireless networks makes them vulnerable to the eavesdropper attacks. Cooperative relay transmission is a popular method to prevent the attacks of the illegal nodes. This research proposes a cooperative jamming protocol to enhance the physical layer in wireless cooperative networks, where the destination sends a jamming signal to the eavesdropper node to degrade its channel capacity. Simulations of the secrecy performance metrics in terms of the secrecy capacity and secrecy outage probability are presented and discussed to measure the security level of the proposed jamming protocol. In this paper, different channels namely Rician fading, Rayleigh fading, and Additive White Gaussian Noise (AWGN) channels are investigated in the half-duplex two-way relaying system to obtain the maximum secrecy performance. Based on the results, the highest secrecy capacity is achieved by using the Rician fading channel for transmission from the source to the destination and using the Rayleigh channel as the jamming link to degrade the eavesdropper capacity.