New Paradigm for Secure Full-Duplex Transmission: Movable Antenna-Aided Multi-User Systems

In this paper, we investigate physical layer security (PLS) for full-duplex (FD) multi-user systems. To simultaneously protect uplink (UL) and downlink (DL) transmissions and ensure efficient use of time-frequency resources, we consider a base station (BS) that operates in FD mode and enables to emit the artificial noise (AN). Conventional fixed-position antennas (FPAs) at the BS struggle to fully exploit spatial degrees of freedom (DoFs). Therefore, we propose a new paradigm for secure FD multi-user systems, where multiple transmit and receive movable antennas (MAs) are deployed at the BS to serve UL and DL users and effectively counter the cooperative interception by multiple eavesdroppers (Eves). Specifically, the MA positions, the transmit, receive, and AN beamformers at the BS, and the UL powers are jointly optimized to maximize the sum of secrecy rates (SSR). To solve the challenging non-convex optimization problem with highly coupled variables, we propose an alternating optimization (AO) algorithm. This algorithm decomposes the original problem into three sub-problems, which are iteratively solved by the proposed multi-velocity particle swarm optimization (MVPSO) and successive convex approximation (SCA). Simulation results demonstrate that the proposed scheme for MA-aided secure FD multi-user systems can significantly enhance security performance compared to conventional FPA systems.

Secure Full-Duplex Communication via Movable Antennas

This paper investigates physical layer security (PLS) for a movable antenna (MA)-assisted full-duplex (FD) system. In this system, an FD base station (BS) with multiple MAs for transmission and reception provides services for an uplink (UL) user and a downlink (DL) user. Each user operates in half-duplex (HD) mode and is equipped with a single fixed-position antenna (FPA), in the presence of a single-FPA eavesdropper (Eve). To ensure secure communication, artificial noise (AN) is transmitted to obstruct the interception of Eve. The objective of this paper is to maximize the sum secrecy rate (SSR) of the UL and DL users by jointly optimizing the beamformers of the BS and the positions of MAs. This paper also proposes an alternating optimization (AO) method to address the non-convex problem, which decomposes the optimization problem into three subproblems and solves them iteratively. Simulation results demonstrate a significant performance gain in the SSR achieved by the proposed scheme compared to the benchmark schemes.

Movable Antenna-Enabled Co-Frequency Co-Time Full-Duplex Wireless Communication

Movable antenna (MA) provides an innovative way to arrange antennas that can contribute to improved signal quality and more effective interference management. This method is especially beneficial for co-frequency co-time full-duplex (CCFD) wireless communication, which struggles with self-interference (SI) that usually overpowers the desired incoming signals. By dynamically repositioning transmit/receive antennas, we can mitigate the SI and enhance the reception of incoming signals. Thus, this paper proposes a novel MA-enabled point-to-point CCFD system and formulates the minimum achievable rate of two CCFD terminals. To maximize the minimum achievable rate and determine the near-optimal positions of the MAs, we introduce a solution based on projected particle swarm optimization (PPSO), which can circumvent common suboptimal positioning issues. Moreover, numerical results reveal that the PPSO method leads to a better performance compared to the conventional alternating position optimization (APO). The results also demonstrate that an MA-enabled CCFD system outperforms the one using fixed-position antennas (FPAs).