Abstract
We apply the concept of artificial and controlled interference in a two-hop relay network with an untrusted relay, aiming at enhancing the wireless communication secrecy between the source and the destination node. In order to shield the square quadrature amplitude-modulated (QAM) signals transmitted from the source node to the relay, the destination node designs and transmits artificial noise (AN) symbols to jam the relay reception. The objective of our considered AN design is to degrade the error probability performance at the untrusted relay, for different types of channel state information (CSI) at the destination. By considering perfect knowledge of the instantaneous CSI of the source-to-relay and relay-to-destination links, we first present an analytical expression for the symbol error rate (SER) performance at the relay. Based on the assumption of an average power constraint at the destination node, we then derive the optimal phase and power distribution of the AN that maximizes the SER at the relay. Furthermore, we obtain the optimal AN design for the case where only statistical CSI is available at the destination node. For both cases, our study reveals that the Gaussian distribution is generally not optimal to generate AN symbols. The presented AN design takes into account practical parameters for the communication links, such as QAM signaling and maximum likelihood decoding.
Highlights
Securing data communications relies heavily on modern cryptography
We have investigated physical layer secrecy for a two-hop single-antenna relay channel, where one source aims to transmit to one destination assisted by one untrusted relay
The objective was to design artificial noise (AN) symbols generated by the destination node that degrades the error probability performance at the untrusted relay by maximizing its achieved symbol error rate (SER) performance
Summary
Securing data communications relies heavily on modern cryptography. Since Diffie and Hellman [1]. To shield the messages from the untrusted relay and enhance the secrecy of the wireless communication between the source and destination, one popular scheme at the physical layer is to introduce controlled artificial noise (AN) to efficiently jam the signal reception at the relay This technique has recently been studied from an information-theoretic perspective, such as secrecy rate and secrecy outage probability, see e.g., [22,28,29,30,31,32]. It has been shown that a positive secrecy rate can be achievable in this AN-assisted untrusted relay network [41] For this setup and with the knowledge of instantaneous CSI as assumed, we first investigate the problem of how to optimally design the AN to maximize the SER of QAM signals at the relay. |b| and b∗ represent absolute value and complex conjugate of b, respectively
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