2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 21355-21370· 0 citations· 34 references
Abstract
In this paper, we consider a backscatter communication (BackCom)-assisted uplink pinching-antenna system in Internet of Things (IoT), where a non-energy-constrained IoT device provides radio frequency signals to support multiple energy-constrained IoT devices, with multiple pinching antennas deployed on a waveguide. We formulate a joint optimization problem to select a energy-constrained device and simultaneously design its power reflection coefficient and pinching antenna locations. The objective is to maximize the achievable rate of the selected device, subject to the quality of service requirements of the non-energy-constrained device, minimum energy harvesting at energy-constrained devices, and collision-free constraints imposed on the pinching antennas. The problem is non-convex and analytically intricate, due to the strong interdependence among device selection, power reflection coefficients, and antenna positions. To overcome these challenges, we propose a block coordinate descent-based successive convex approximation algorithm that iteratively transforms the original non-convex problem into a series of convex subproblems that can be solved efficiently. Additionally, we analyze a special case with a single pinching antenna, deriving the optimal antenna location along with an approximate outage probability expression and the corresponding diversity order. Simulation results demonstrate that the proposed system achieves higher achievable rates, lower outage probability, and improved diversity gain compared to conventional uplink fixed-antenna systems.
This letter investigates transmit-power minimization for multiuser pinching-antenna system (PAS) from a coupled-mode-theory (CMT)-aware perspective. Existing CMT-based pinching antenna (PA) studies reveal coupling-induced power exchange and radiation behavior, but these effects have not been fully embedded into system-level multi-PA channel modeling and beamforming design. We therefore develop a directional and loss-aware channel model that captures coupling-length-dependent power extraction and the downstream guided-power reduction caused by in-waveguide attenuation and upstream extraction. The model shows that PA design should account for both directional radiation and guided-power evolution, rather than only propagation distance or maximum coupling considered in most existing works. Based on this channel model, we formulate a quality-of-service (QoS)-constrained power minimization problem for continuous PA positioning and finite-codebook activation. For each candidate coupling length, the element-wise positioning and BPSO-based activation use a closed-form zero-forcing (ZF) power metric for low-complexity configuration ranking, thereby avoiding repeated beamforming optimization while excluding rank-deficient candidates and ordering the remaining ones. The selected configuration for each coupling length is then evaluated by optimal fixed-configuration QoS beamforming. Simulation results demonstrate that CMT-aware modeling fundamentally reshapes the preferred PA configuration, maximum coupling is not always power-efficient due to suppressed downstream PA contributions, and finite-codebook activation combined with ZF-based ranking provides a balance between transmit-power performance and deployment complexity.
Chuang Luo, Gui Zhou, V. Papanikolaou et al.· 0 citations
High-altitude platform station (HAPS) serves as a promising enabler for wide-area connectivity of low-power wireless devices, particularly in remote and underserved regions. However, the strong line-of-sight characteristics of HAPS links increase the risk of eavesdropping, while the limited energy budget of ground devices remains a major operational constraint. In this work, we propose a secure wireless information and energy harvesting framework for HAPS-based networks in the presence of spatially distributed eavesdroppers. The proposed system integrates friendly jamming and power transfer nodes equipped with null-steering capability antennas, such that they not only degrade the reception quality at eavesdroppers but also act as additional radio-frequency energy sources for legitimate users. A time-switching wireless information and power transfer architecture is adopted at the user side. Under this framework, we derive tractable expressions for the joint rate-energy coverage and the average secrecy rate using stochastic geometry tools. Numerical and Monte Carlo results validate the developed analysis and reveal key design trade-offs among the time allocation factor, null-steering-zone radius around each user, and jammer transmit power. In particular, the results show that properly coordinated null-steering jamming can simultaneously support secure communication and adequate wireless power transfer, while an appropriate choice of system parameters, such as time allocation factor and jamming power, is required to balance harvested energy, communication reliability, and secrecy performance.
Khaled M. Humadi, Günes Karabulut-Kurt, W. Ajib et al.· IEEE Journal of Radio Freque...· 0 citations
Reconfigurable intelligent surface (RIS)-assisted wireless-powered communication networks (WPCNs) introduce a new degree of freedom: the same passive beamforming array can concentrate the downlink energy toward harvesting devices and simultaneously shape the uplink interference environment. In this paper, we study a system where the base station (BS) waveform serves the dual role of wireless energy transfer (WET) and passive target sensing. Using the position error bound (PEB) derived from the equivalent Fisher information matrix (EFIM) as the sensing quality metric, we formulate a joint resource allocation problem that maximizes weighted uplink sum-rate subject to a PEB constraint, energy-causality, block-time sharing, and unit-modulus RIS phase constraints. Focusing on the practically important WET-only sensing case, we show that the problem separates into four tractable subproblems and propose a block coordinate descent (BCD) algorithm: (i) closed-form water-filling for WIT time-power allocation, (ii) semidefinite relaxation (SDR) with Dinkelbach iterations for per-slot WIT-RIS beamforming, (iii) golden-section search for the optimal WET duration, and (iv) a convex SDP for WET-RIS optimization under a PEB constraint. The BCD iterates converge monotonically. Simulations confirm a fundamental rate–sensing tradeoff and demonstrate significant gains from joint RIS-assisted optimization.
Yongjie Li, Jing Shen, Jizhao Lu et al.· 2026 8th International Confe...· 0 citations
This paper studies a cooperative wireless system in which a single-antenna base station (BS) communicates with a destination user (U) via a half-duplex energy-harvesting amplify-and-forward relay, while the direct BS–U link is unavailable. The destination (U) is equipped with a fluid antenna system (FAS) comprising multiple closely spaced receive ports, enabling spatial reconfigurability through instantaneous port selection. A power-splitting architecture is adopted at the relay to support simultaneous energy harvesting and information forwarding. All wireless links are modeled as flat Rayleigh fading, and the spatial correlation among the FAS ports is explicitly incorporated. To analytically characterize the impact of correlated port selection, a Gaussian copula framework is employed to model the joint distribution of the FAS-channel power gains. Exact integral expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived, from which the outage probability is obtained. For the special case of uncorrelated FAS ports, closed-form expressions are further developed using order statistics and special functions. In addition, asymptotic analysis is carried out to provide further insight into system performance in the high-signal-to-noise-ratio region. Numerical and Monte Carlo simulation results validate the analytical derivations and demonstrate that FAS-based receiver selection yields significant gains in outage performance, even in the presence of strong spatial correlation and energy-harvesting constraints.
A novel two-timescale optimization framework is proposed for pinching-antenna systems (PASS)-enabled secure integrated sensing and communications (ISAC). Specifically, a base station (BS) equipped with pinching antennas (PAs) transmits signals to a legitimate user under the existence of an eavesdropper (Eve), while employing leaky coaxial cables (LCXs) for receiving echo signals to track Eve's mobility states, i.e., locations and velocities. Considering the practical PAs activation overhead, the pinching beamforming and baseband processing are optimized in the large and small timescales, respectively. The multiple-waveguide scenario is first considered, where the BS can transmit the artificial noise together with communication signals for both jamming and sensing purposes. A joint baseband and pinching beamforming design problem is formulated to maximize the average secrecy rate. To address this problem, an alternating optimization algorithm is first invoked for jointly optimizing the pinching and baseband beamforming with predicted Eve's mobility states. With determined PAs positions, the baseband beamforming is updated with refined Eve's states obtained from real-time echo signal processing. The single-waveguide scenario is then considered. Since a single waveguide carries at most one independent data stream, an ISAC framework with separate communication and sensing phases is proposed. The element-wise algorithm proposed for the multiple-waveguide scenario is extended to solve the resultant pinching beamforming problem. Numerical results demonstrate that: 1) Eve's velocities and positions can be accurately tracked with the proposed two-timescale framework in both multiple- and single-waveguide scenarios; and 2) PASS achieves superior secrecy rate compared to conventional multiple-antenna benchmarks.
Haowen Song, Jingjing Zhao, Xidong Mu et al.· 0 citations
Low Earth orbit (LEO) satellite communications face critical challenges in serving blocked users due to severe penetration loss and signal blockage. Conventional active relay solutions incur high energy consumption and hardware costs. This letter introduces a pinching-antenna relay system (PARS) for energy-efficient LEO satellite communication in blockage environments. By using dielectric waveguides with dynamically reconfigurable PAs, PARS provides flexible spatial diversity and beamforming gains with the circuit control and PA actuation power. We formulate an energy-efficiency (EE) maximization problem by jointly optimizing the satellite precoding and PA positions. A Dinkelbach-based block coordinate descent (BCD) algorithm is proposed to solve the non-convex fractional program via iterative weighted minimum mean square error (WMMSE) transformation and projected gradient descent (PGD) updates. Simulations show that the proposed PARS achieves superior EE over direct transmission, fixed-PA, decode-and-forward (DF) and zero-forcing (ZF) baselines. The resulting performance crossover further identifies the PARS-dominant region, providing practical deployment guidance for blockage-affected scenarios.
Ruihong Jiang, Jincong Mo, Hui-Min Hu et al.· IEEE Wireless Communications...· 0 citations
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