US Government As Represented by the Secretary of the Army

Fikadu T Dagefu

Brian M Sadler

Justin S Kong

Jihun Choi

Kamal Sarabandi

Systems and methods for wireless communications comprising a plurality of agents, which together as the group, are configured to: (i) wirelessly broadcast an interference signal by forming a radiation pattern having null vectored substantially toward a client; (ii) wirelessly transmit a communication signal to the client by forming a radiation beam carrying the communication signal vectored substantially toward the client; and (iii) wirelessly broadcast a combined communication signal and interference signal to the client using phases of processes (i) and (ii). In some embodiments, the agents together as a group may be further configured to: allocate and adjust power for performing processes (i) and (ii) at substantially the same time.

Simultaneous beamforming and nullforming for secure wireless communications

We disclose a novel methodology for wireless networks that optimizes the transmission probability, transmit power at an agent, and the reflection matrix of an IRS for covert RF communications. Key features include: (1) An exact closed-form expression for the expected detection error probability (DEP) at an adversary is provided considering the transmission probability at the agent; and (2) a novel method to optimize the transmission probability, transmit power at the agent and the reflection matrix of the IRS with the goal of maximizing the achievable rate at a client while ensuring a covertness constraint is developed. More specifically, the method may require only one-dimensional line search schemes, achieves near-optimal performance, and exhibits enhanced achievable data rate when compared to the conventional technique without the transmission probability optimization.

Covert communication technique for intelligent reflecting surface assisted wireless networks

A system and method for distributed wireless communications comprising a first group of agents selected and configured to wirelessly transmit a communication signal to a client, wherein the first group of agents is capable of forming a radiation beam carrying the communication signal vectored substantially toward the client, and a second group of agents selected and configured to wirelessly broadcast communication signal interference, wherein the second group of agents is capable of forming a radiation beam not vectored substantially toward the client. Consequently, the first group of agents securely communicates with the client and the second group of agents suppresses the ability of an unauthorized, eavesdropping receiver from intercepting the communications signal.

Distributed adaptive beamforming and nullforming for secure wireless communications

An active matching network for impedance matching to a miniature antenna, comprising a cross-coupled transistor pair, where each transistor has an emitter, base and collector, the emitter of a first transistor forms an input terminal, the emitter of a second transistor forms on output terminal, the collector of the first transistor coupled to the base of the second transistor, the collector of the second transistor coupled to the base of the first transistor, and a matching circuit coupled between the collectors of the first and second transistors. The matching network is configured to match an impendence near resonance of the high Q miniature antenna to an input impedance using a complex negative impedance comprising resistance, inductance and capacitance.

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Silver Spring, MD, United States of America

Fikadu T Dagefu