RIS-Assisted Robust Hybrid Beamforming AgainstSimultaneous Jamming and Eavesdropping Attacks

in IEEE Transactions on Wireless Communications (2022), 21(11), 9212-9231

Wireless communications are increasingly vulnera-ble to simultaneous jamming and eavesdropping attacks due tothe inherent broadcast nature of wireless channels. With thisfocus, due to the potential of ... [more ▼]

Wireless communications are increasingly vulnera-ble to simultaneous jamming and eavesdropping attacks due tothe inherent broadcast nature of wireless channels. With thisfocus, due to the potential of reconfigurable intelligent surface(RIS) in substantially saving power consumption and boostinginformation security, this paper is the first work to investigate theeffect of the RIS-assisted wireless transmitter in improving boththe spectrum efficiency and the security of multi-user cellularnetwork. Specifically, with the imperfect angular channel stateinformation (CSI), we aim to address the worst-case sum ratemaximization problem by jointly designing the receive decoder atthe users, both the digital precoder and the artificial noise (AN)at the base station (BS), and the analog precoder at the RIS, whilemeeting the minimum achievable rate constraint, the maximumwiretap rate requirement, and the maximum power constraint.To address the non-convexity of the formulated problem, we firstpropose an alternative optimization (AO) method to obtain anefficient solution. In particular, a heuristic scheme is proposedto convert the imperfect angular CSI into a robust one andfacilitate the developing a closed-form solution to the receivedecoder. Then, after reformulating the original problem into atractable one by exploiting the majorization-minimization (MM)method, the digital precoder and AN can be addressed by thequadratically constrained quadratic programming (QCQP), andthe RIS-aided analog precoder is solved by the proposed pricemechanism-based Riemannian manifold optimization (RMO).To further reduce the computational complexity of the pro-posed AO method and gain more insights, we develop a low-complexity monotonic optimization algorithm combined with thedual method (MO-dual) to identify the closed-form solution.Numerical simulations using realistic RIS and communicationmodels demonstrate the superiority and validity of our proposedschemes over the existing benchmark schemes. [less ▲]

1 Energy-Efficient Hybrid Beamforming for Multi-Layer RIS-Assisted Secure Integrated Terrestrial-Aerial Network

in IEEE Transactions on Communications (2022), 70(6), 4189-4210

The integration of aerial platforms to provide ubiq- uitous coverage and connectivity for densely deployed terrestrial networks is expected to be a reality in emerging sixth-generation networks. Energy ... [more ▼]

The integration of aerial platforms to provide ubiq- uitous coverage and connectivity for densely deployed terrestrial networks is expected to be a reality in emerging sixth-generation networks. Energy-effificient design and secure transmission are two crucial issues for integrated terrestrial-aerial networks. With this focus, due to the potential of RIS in substantially saving power consumption and boosting the security of private information by enabling a smart radio environment, this paper investigates the energy-efficient hybrid beamforming for multi- layer reconfigurable intelligent surface (RIS)-assisted secure in- tegrated terrestrial-aerial network for defending against simul- taneous jamming and eavesdropping attacks. Specifically, with the available of angular information based imperfect channel state information (CSI), we propose a framework for the joint optimization of user’s received precoder, terrestrial BS’s and HAP’s digital precoder, and multi-layer RIS analog precoder to maximize the system energy efficiency (EE) performance. For the design of received precoder, a heuristic beamforming scheme is proposed to convert the worst-case problem into a min-max one such that a closed-form solution is derived. For the design of digital precoder, we propose an iterative sequential convex approximation approach via capitalizing the auxiliary variables and first-order Taylor series expansion. Finally, a monotonic vertex-update algorithm with penalty convex concave procedure is proposed to obtain analog precoder with low computational complexity. Numerical results show the superiority and effective- ness of proposed optimization framework and architecture [less ▲]

Detection of Pilot Contamination Attack Using Random Training and Massive MIMO

in IEEE Personal Indoor, Mobile and Radio Conference (PIMRC) 2013 (2013, September 09)

Channel estimation attacks can degrade the performance of the legitimate system and facilitate eavesdropping. It is known that pilot contamination can alter the legitimate transmit precoder design and ... [more ▼]

Channel estimation attacks can degrade the performance of the legitimate system and facilitate eavesdropping. It is known that pilot contamination can alter the legitimate transmit precoder design and strengthen the quality of the received signal at the eavesdropper, without being detected. In this paper, we devise a technique which employs random pilots chosen from a known set of phase-shift keying (PSK) symbols to detect pilot contamination. The scheme only requires two training periods without any prior channel knowledge. Our analysis demonstrates that using the proposed technique in a massive MIMO system, the detection probability of pilot contamination attacks can be made arbitrarily close to 1. Simulation results reveal that the proposed technique can significantly increase the detection probability and is robust to noise power as well as the eavesdropper’s power. [less ▲]

Distributed Multicell Beamforming Design Approaching Pareto Boundary with Max-Min Fairness

in IEEE Transactions on Wireless Communications (2012), 11(8), 2921-2933

This paper addresses coordinated downlink beamforming optimization in multicell time division duplex (TDD) systems where a small number of parameters are exchanged between cells but with no data sharing ... [more ▼]

This paper addresses coordinated downlink beamforming optimization in multicell time division duplex (TDD) systems where a small number of parameters are exchanged between cells but with no data sharing. With the goal to reach the point on the Pareto boundary with max-min rate fairness, we first develop a two-step centralized optimization algorithm to design the joint beamforming vectors. This algorithm can achieve a further sum-rate improvement over the max-min optimal performance, and is shown to guarantee max-min Pareto optimality for scenarios with two base stations (BSs) each serving a single user. To realize a distributed solution with limited intercell communication, we then propose an iterative algorithm by exploiting an approximate uplink-downlink duality, in which only a small number of positive scalars are shared between cells in each iteration. Simulation results show that the proposed distributed solution achieves a fairness rate performance close to the centralized algorithm while it has a better sum-rate performance, and demonstrates a better tradeoff between sum-rate and fairness than the Nash Bargaining solution especially at high signal-to-noise ratio. [less ▲]

Robust Collaborative-Relay Beamforming

in IEEE Transactions on Signal Processing (2009), 57(8), 3130-3143

Relay communications is a promising technique to extend the range of wireless communications by forwarding the message from the sender to the intended destination. While fixed or variable-power relays ... [more ▼]

Relay communications is a promising technique to extend the range of wireless communications by forwarding the message from the sender to the intended destination. While fixed or variable-power relays have been previously investigated, this paper addresses the collaborative use of variable-phase variable-power amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Our main contribution is that we prove, under a condition on the quality of the estimated CSI, the robust-optimal collaborative-relay beamforming (CRBF) can be obtained by S-procedure and rank relaxation techniques. In addition, a distributed algorithm is developed by examining the structure of the optimal CRBF solution. Results demonstrate a significant gain of CRBF over non-robust approaches. [less ▲]