The broadcast nature of wireless communications makes transmission susceptible to eavesdropping. Recently, physical-layer security has been extensively studied to secure the wireless transmissions, but the security is severely compromised when the eavesdropper has the superiority in the channel quality. Toward this issue, we in this paper propose a joint ARQ and network coding method exploiting the characteristics of both the physical layer and the link layer. Specifically, we relate the message to be transmitted in the current slot with the successfully decoded messages in previous slots, where the ARQ is employed at the legitimate side to guarantee the successful transmission and decoding. Once one or more received messages fail to be decoded at the eavesdropper, it further prevents the eavesdropper from decoding the transmissions in later slots and thus the message transmitted currently and later is secured at the legitimate side. Moreover, for the more disadvantageous case that the eavesdropper is geographically closer to the transmitter, we further propose a destination-aided network coding scheme, which secures private information no matter where the eavesdropper is. The closed-form expressions of intercept probability and loss probability of the private information are analytically presented. The simulation results are provided to confirm our theoretical findings.
The broadcast nature of wireless communications makes transmission susceptible to eavesdropping. Recently, physical-layer security has been extensively studied to secure the wireless transmissions, but the security is severely compromised when the eavesdropper has the superiority in the channel quality. Toward this issue, we in this paper propose a joint ARQ and network coding method exploiting the characteristics of both the physical layer and the link layer. Specifically, we relate the message to be transmitted in the current slot with the successfully decoded messages in previous slots, where the ARQ is employed at the legitimate side to guarantee the successful transmission and decoding. Once one or more received messages fail to be decoded at the eavesdropper, it further prevents the eavesdropper from decoding the transmissions in later slots and thus the message transmitted currently and later is secured at the legitimate side. Moreover, for the more disadvantageous case that the eavesdropper is geographically closer to the transmitter, we further propose a destination-aided network coding scheme, which secures private information no matter where the eavesdropper is. The closed-form expressions of intercept probability and loss probability of the private information are analytically presented. The simulation results are provided to confirm our theoretical findings.
In this paper, we investigate physical layer network coding (PNC) and destination assisted cooperative jamming (DACJ) for physical layer security in wireless sensor networks, in which there is one source, one destination, a cluster of intermediate nodes, and multiple eavesdroppers. Under the PNC protocol, the considered two-hop wireless sensor network implements a complete transmission process in two phases. In the first phase, through sending a jamming signal from the destination and exploiting the PNC at the relay, the relay decodes the exclusive-OR (XOR) performed form of the source and the jamming message. Therefore, the jamming signal can degrade the wire-tap channels without hampering the legitimate channel. In the second phase, the relay transmits the re-encoded message to the destination while eavesdroppers are out of work as they cannot extract information from the signal. Thus, the proposed design can significantly improve the performance of secure wireless communications. Meanwhile, the proposed schemes select one optimal node from the intermediate nodes and give an optimal solution of power allocation to maximize secrecy capacity. Numerical simulation results show that the proposed schemes have a better and more stable secrecy performance than the conventional schemes at the same power consumption.
Secure the cooperative transmission is studied for an automatic repeat request (ARQ)-based wireless network against a jamming-aided eavesdropper. The eavesdropper utilizes the jamming attack to assist its eavesdropping by forcing the legitimate transmitter to retransmit its confidential messages under poor wiretap channel quality. Then, utilizing these retransmission opportunities, the eavesdropper will eavesdrop the confidential message under good wiretap channel quality. To address the threat from the jamming-aided eavesdropper in the ARQ-based wireless network, we propose an adaptive cooperative relaying and jamming secure transmission scheme to protect the confidential messages. In the proposed scheme, the legitimate receiver adopts the energy detection method to detect the jamming-aided eavesdropper's action and a cooperative node will aid the secure transmission through cooperative relaying under jamming attack or cooperative jamming under eavesdropping attack. By taking into account of the detection errors, we investigate the transmission outage probability and the secrecy outage probability, and derive their closed-form expressions for both one retransmission and multiple retransmissions scenarios. Numerical results are presented to verify the derived analytical results and demonstrate the performance superiority of the proposed scheme in terms of the secrecy outage probability.
Due to the openness of wireless multiuser networks, the private information transmitted in uplink or downlink is vulnerable to eavesdropping. Especially, when the downlink transmissions use nonorthogonal multiple access (NOMA) techniques, the system further encounters interior eavesdropping. In order to address these security problems, we study the secret communication in multiuser networks with both uplink and downlink transmissions. Specifically, in uplink transmissions, the private messages transmitted in each slot are correlated, so any loss of the private information at the eavesdropper will prevent the eavesdropper from decoding the private information in later time slots. In downlink transmissions, the messages are correlated to the uplink information. In this way, any unexpected users who lose the expected user's uplink information cannot decode its downlink information. The intercept probability is used to measure security performance and we analyze it in theory. Finally, simulation results are provided to corroborate our theoretical analysis.
Wireless communication networks are widely deployed today and the networks are used in many applications which require that the data transmitted be secure. Due to the open nature of wireless systems, it is important to have a fundamental understanding of coding schemes that allow for simultaneously secure and reliable transmission. The information theoretic approach is able to give us this fundamental insight into the nature of the coding schemes required for security. The security issue is approached by focusing on the confidentiality of message transmission and reception at the physical layer. The goal is to design coding and signal processing schemes that provide security, in the information theoretic sense. In so doing, we are able to prove the simultaneously secure and reliable transmission rates for different network building blocks. The multi-receiver broadcast channel is an important network building block, where the rate region for the channel without security constraints is still unknown. In the thesis this channel is investigated with security constraints, and the secure and reliable rates are derived for the proposed coding scheme using a random coding argument. Cooperative relaying is next applied to the wiretap channel, the fundamental physical layer model for the communication security problem, and signal processing techniques are used to show that the secure rate can be improved in situations where the secure rate was small due to the eavesdropper enjoying a more favorable channel condition compared to the legitimate receiver. Finally, structured lattice codes are used in the wiretap channel instead of unstructured random codes, used in the vast majority of the work so far. We show that lattice coding and decoding can achieve the secrecy rate of the Gaussian wiretap channel; this is an important step towards realizing practical, explicit codes for the wiretap channel.
Due to the broadcast nature of wireless device-to-device networks, the transmission of private information is threatened by the exterior eavesdropping. Targeting at this problem, we jointly exploit the Wyner's code and the linear network coding, in this paper, to improve the security. The function of the Wyner's code requires the legitimate channel better than the eavesdropper's channel, so we propose a novel relay selection scheme to achieve this objective. Specifically, two groups of relays have been selected. Relays in one of the groups are selected to forward the private information, and relays in the other group are selected to transmit artificial noise. In this way, we make sure that the signal-to-noise ratio (SNR) at the legitimate receiver is larger than a target value but the SNR at the eavesdropper has a certain probability less than the target value so that the security can be enhanced. Moreover, focusing on the problem that the Wyner's code cannot achieve security if the SNR at the eavesdropper is larger than the target value, we propose a network coding method. In this method, the message to be transmitted is divided into multiple parts, and then these parts are correlated with each other by using network coding. Thus, the eavesdropper also cannot decode the private information even its SNR larger than the target value. We analyze the secrecy outage probability in theory, and the simulation results are provided to confirm our analysis.
Security is a critical concern in wireless network. Physical layer security exploits the physical characteristics of wireless channel for secure transmission. The physical layer security approach is a competitive alternative to achieve information-theoretic secrecy. In the area of physical layer security which guarantees confidentiality by using Automatic Repeat Request technique, ARQ is described in a general way that includes its use over a wide range of underlying physical medium. Physical layer security focuses on exploiting the physical layer properties of the wireless channels to protect the confidential information transmission against eavesdropping. It describes the electric or optical signals used for communicating between two computers. Here a physical layer security technique is adopted for secret key distribution. In this improving physical layer based security for wireless network using jamming technique in automatic repeat request has been implemented. The automatic repeat request (ARQ) mechanism is a well-known technique to handle transmission errors, when data is transmitted over noisy channels. This service describes sending and receiving information with possible confirmation. The result obtained gives the performance of the increased signal to noise ratio and the decreased bit error rate and the mean square error.