arXiv subjects

Zhiguo Ding

Publications and source records attributed to Zhiguo Ding.

At least 19 recordsLinked to original sources

arXiv2026

Trajectory Design and User Scheduling for Pinching-Antenna Systems

Finite antenna movement speed introduces repositioning delays that can limit the performance gains of pinching-antenna systems. In this paper, a trajectory based scheme is proposed for a time division multiple access (TDMA) based pinching-antenna system, allowing transmission during both movement and stationary operation. A discrete-time model is developed to characterize periodic antenna trajectories and antenna-user service association under practical movement constraints. For a single-waveguide scenario, the expected average achievable rate is derived. The rate loss relative to instantaneous positioning and the rate improvement over a fixed antenna are further analyzed, with an upper bound on the former and a lower bound on the latter established. To improve fairness among users, a minimum average rate maximization problem is formulated through joint trajectory design and user scheduling. To address the coupling between these variables, an alternating optimization (AO) framework is adopted. Specifically, a successive convex approximation (SCA) based algorithm is developed using concave rate lower bounds, while a game based scheduling algorithm employs an ordered user-rate vector as the common utility. The convergence of the SCA objective value and the finite termination and stability of the scheduling algorithm are established. Simulation results demonstrate the gains achieved by the joint design and show that the proposed system can approach instantaneous-positioning performance under finite antenna movement speed.

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arXiv2026

Design of DoF-Robust MIMO via Generalized Pinching Antennas

Spatial degrees of freedom (DoF) are fundamental to the performance of multiple-input multiple-output (MIMO) systems. However, the use of conventional fixed-location antennas introduces disparities in the users' distances to a common base station, which makes the multi-user channel matrix more susceptible to rank deficiency and, consequently, a loss of spatial DoF. This paper shows that generalized pinching antennas can be used to design a new form of MIMO robust to the loss of spatial DoF. In particular, by deploying pinching antennas in close proximity to the users, the resulting multi-user channel Gram matrix can have a well-conditioned, almost diagonal structure, which reduces its sensitivity to the users' spatial deployment as well as the risk of rank deficiency. Two performance metrics, namely the rank-deficiency probability and the outage probability, are used to evaluate the performance of pinching-antenna-assisted MIMO transmission. The presented analytical and simulation results demonstrate the capability of pinching antennas to preserve spatial DoF and provide ubiquitous connectivity by effectively supporting users at spatially separated locations.

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arXiv2026

Dynamic Metasurface-Enabled Generalized Pinching-Antenna Systems

This article investigates dynamic metasurfaces as an electronic realization of generalized pinching antennas (GPA). By jointly optimizing the locations and radiation coefficients of activated elements, the dynamic metasurface-enabled GPA (DM-GPA) architecture exploits additional design flexibility to enhance spatial reconfigurability beyond that attainable through antenna placement in the conventional pinching-antenna system (PASS). Based on this architecture, we study weighted sum rate (WSR) maximization for multiuser downlink transmission. 1) For two-user transmission, the sum-rate improvement of DM-GPA over conventional PASS is quantified through a lower bound that reveals when the benefit of channel orthogonalization achieved by adjusting the radiation coefficients outweighs the channel power loss caused by the Lorentzian constraint. Furthermore, when conventional PASS yields a rank-deficient channel, DM-GPA is shown to achieve spatial multiplexing and transmit diversity, with a strict sum-rate advantage at sufficiently high signal-to-noise ratios. 2) For general multiuser transmission, a weighted minimum mean-square error (WMMSE)-based alternating optimization algorithm is developed for joint pinching beamforming and digital precoder design. A sequential element-wise search is developed to optimize the locations of the activated elements, with a closed-form solution for the radiation coefficient at each candidate location. Numerical results are provided to demonstrate that: (i) DM-GPA achieves higher WSR than other PASS architectures and fixed-array benchmarks, (ii) increasing the number of activated elements further improves the WSR of DM-GPA, and (iii) radiation coefficient adjustment is particularly beneficial when candidate activation locations are limited.

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arXiv2026

Leaky Coaxial Cable based Generalized Pinching-Antenna Systems with Dual-Port Feeding

By leveraging the distributed leakage radiation of leaky coaxial cables (LCXs), the concept of pinching antennas can be generalized from the conventional high-frequency waveguide based architectures to cable based structures in lower-frequency scenarios. This paper investigates an LCX based generalized pinching-antenna system with dual-port feeding. By enabling bidirectional excitation along each cable, the proposed design significantly enhances spatial degrees of freedom. A comprehensive channel model is developed to characterize intra-cable attenuation, bidirectional phase progression, slot based radiation, and wireless propagation. Based on this model, both analog and hybrid beamforming frameworks are studied with the objective of maximizing the minimum achievable data rate. For analog transmission, slot activation, port selection, and power allocation are jointly optimized using matching theory, coalitional games, and bisection based power control. For hybrid transmission, zero-forcing (ZF) digital precoding is incorporated to eliminate inter-user interference, thereby simplifying slot activation and enabling closed-form optimal power allocation. Simulation results demonstrate that dual-port feeding provides notable performance gains over single-port LCX systems and fixed-antenna benchmarks, validating the effectiveness of the proposed beamforming and resource allocation designs under various transmit power levels and cable parameters.

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arXiv2026

Waveguide Deployment Optimization for Pinching-Antenna Systems

Most existing studies on pinching-antenna systems optimize the antenna positions or activation states under a prescribed waveguide deployment, where mutually parallel waveguides are commonly adopted. However, it remains unclear whether, and under what conditions, such a deployment is optimal from a communication-performance perspective. To fill this gap, this paper investigates long-term waveguide deployment optimization for pinching-antenna systems over a rectangular service region. We first consider the fundamental two-waveguide case and derive a closed-form sufficient condition, jointly determined by the waveguide height and the service-region aspect ratio, under which a deployment parallel to the longer side of the service region is globally optimal. We then consider the general multi-waveguide case, where the orientation and offset of each waveguide are jointly optimized without prescribing any deployment pattern, and develop an adaptive exchange algorithm for the resulting nonconvex optimization problem. We further show that, within the parallel class, the waveguides should be aligned with the longer side of the service region, while in the large-height regime, the globally optimal unrestricted deployment asymptotically concentrates all waveguides on the centerline along the longer side. Numerical results validate the proposed algorithm and reveal how the preferred deployment geometry depends on the waveguide height and service-region shape. In particular, nonparallel deployments can provide noticeable gains in intermediate-height regimes, whereas parallel or center-concentrated deployments become favorable in other regimes.

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arXiv2026

Age-of-Information Aware Federated Learning with Finite Speed Pinching Antenna

This paper investigates age-of-information (AoI) aware federated learning over wireless networks with finite speed pinching antennas. In contrast to existing studies that assume an infinitely high antenna moving speed, a practical round based training procedure is considered, where the pinching antenna is repositioned during the local training phase and its feasible movement range depends on the selected devices. This creates a new coupling among device selection, antenna placement, local training time, model uploading time, and AoI evolution. To characterize the impact of antenna moving speed, the rate gain over the fixed antenna and the gap to the infinite speed benchmark are analyzed. Subsequently, an overall AoI minimization problem is formulated under a round latency deadline by jointly optimizing the selected device set and the pinching antenna position. A coalitional game based device selection algorithm is proposed, where finite speed antenna placement is incorporated into the coalition utility evaluation. For antenna placement, the optimal search region is derived by exploiting the mobility constraint and device location span, based on which a branch-and-bound (BnB) algorithm is developed to obtain the global optimum. Simulation results show that the proposed scheme can accelerate learning convergence, reduce the sum AoI, and improve device participation compared with baseline schemes, demonstrating the potential of pinching antennas for enhancing federated learning through flexible spatial reconfiguration.

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arXiv2026

Performance Analysis of Pinching Antenna Systems Enabled NOMA Communications

Pinching antenna systems (PASS) have the advantages in the perspective of flexible antenna reconfiguration, line-of-sight (LoS) creation, and scalability features. To highlight the ascendancy of PASS, we survey the integration of PASS into non-orthogonal multiple access (NOMA) networks. The locations of nodes are randomly distributed within a circular coverage region. The influencing factors of LoS and none-line-of-sight (NLoS) propagation links from PASS to non-orthogonal nodes are taken into consideration. To characterize performance of PASS-NOMA, we deduce the outage probability and ergodic data rates expressions of two nodes over LoS/NLoS fading channels. In light of these theoretical results, the formally unbounded diversity gains are also characterized with node n under ideal successive interference cancellation (ISIC) and node f over LoS links, when the SNR exceeds a finite threshold. The slopes of ergodic data rate for node n with ISIC equals to one and that of node f presents a zero slope. In addition, the PASS-NOMA system throughput are evaluated in different transmission modes. It is shown from the numerical results that: 1) The outage behaviors of PASS-NOMA networks under LoS/NLoS conditions outperform that of PASS aided orthogonal multiple access (OMA) networks and that of conventional antenna systems (CASS) aided OMA/NOMA networks; 2) The employment of PASS enables the larger ergodic data rates relative to PASS-OMA and CASS-OMA/NOMA networks; and 3) As the quantity of communication radius and PASS' height rises, the performance of PASS-NOMA networks are declined at a certain extent.

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arXiv2026

Pinching Antennas for Next-Generation Wireless Communications: A Network Perspective

Pinching antennas enable radiation points to be created and reconfigured along extended waveguides, making the physical locations of wireless transmission and reception controllable after infrastructure deployment. This capability introduces a spatial degree of freedom beyond conventional beamforming and resource allocation, with implications that extend from individual links to network-wide operation. This tutorial develops a network-oriented perspective on pinching-antenna systems. We first review their system architecture, channel characteristics, and fundamental design opportunities. We then examine how radiation-location reconfigurability can support environment-division multiple access by strengthening desired links and suppressing cross-links, and discuss its roles in multi-cell transmission, traffic offloading, and inter-cell cooperation. Moving from instantaneous users to entire service regions, we introduce traffic-aware and geometry-aware designs under a cell-free-inspired multi-waveguide architecture. Representative system models, optimization problems, analytical illustrations, and numerical results are provided to explain the main design tradeoffs and network-level insights. We further discuss generalized physical realizations and representative deployment modes, including standalone, conventional base-station-integrated, and distributed deployments, together with their main implementation considerations. Finally, we identify future research directions involving mobility management, programmable and virtualized radio access, environment knowledge acquisition, AI-native control, low-altitude networks, space-air-ground integration, and integrated sensing and communication. Overall, this tutorial presents radiation locations as configurable network resources and provides a framework for understanding how pinching antennas may reshape future wireless network.

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arXiv2026

Multi-Mode Pinching-Antenna Systems: An Inter-Mode-Interference-Free Perspective

The physical model of multi-mode pinching-antenna systems (PASS) is proposed based on the coupled-mode theory. Within the considered model, multiple guided modes are simultaneously excited in a single waveguide and exploited as independent signal-bearing channels, thus providing additional modal degrees of freedom for signal transmission. Under the local electromagnetic perturbations introduced by PAs, the undesired guided-modes coupling is explicitly investigated, and the resulting inter-mode interference (IMI) issue is revealed. The sufficient hardware-design condition for achieving the IMI-free regime is further established, for which the practical feasibility is validated through full-wave electromagnetic simulations. Then, a tractable signal model is derived for multi-mode PASS operating over the IMI-free regime. To demonstrate the benefits of the proposed multi-mode PASS model, the integrated sensing and communications (ISAC) is studied as a representative application scenario, where the base station simultaneously communicates with a communication user and senses a target by using two guided modes. A joint baseband and pinching beamforming optimization problem is formulated for the minimization of the Cramer-Rao bound for target localization, subject to the minimum communication rate requirement, under both continuous and discrete PAs activation cases. An alternating optimization-based algorithm is developed to address the formulated non-convex problem. For the baseband beamforming, a penalty-based successive convex approximation method is invoked. For the pinching beamforming, a particle swarm optimization algorithm and a two-sided matching algorithm are proposed for the continuous and discrete PAs activation cases, respectively. Numerical results obtained in the ISAC application scenario demonstrate the superiority of the proposed multi-mode PASS model over the single-mode PASS.

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arXiv2026

Environment-Aware Network-Level Design of Pinching-Antenna Systems--Part I: Traffic-Aware Case

Existing studies on pinching-antenna systems have primarily focused on link-level design, where system parameters are optimized for a given user set according to user-specific communication metrics. Such designs provide an effective means of exploiting the spatial reconfigurability of pinching antennas for short-term user-centric transmission. Complementing this perspective, this two-part paper develops an environment-aware network-level design framework, where pinching-antenna configurations are optimized according to long-term spatial information and evaluated through network-level performance metrics. Part I focuses on the traffic-aware case, where user presence is modeled statistically by a spatial traffic map and performance is optimized and evaluated in a traffic-aware sense; Part II addresses the geometry-aware case in obstacle-rich environments by explicitly modeling line-of-sight blocking and optimizing region-wide robustness objectives. In Part~I, we introduce traffic-weighted average SNR metrics and formulate two traffic-aware deployment problems: (i) maximizing the traffic-weighted network average SNR, and (ii) a fairness-oriented traffic-restricted max--min average-SNR design over traffic-dominant grids. To solve these nonconvex problems with low complexity, we reveal and exploit their separable structures. For the network-average objective, we establish unimodality properties of the hotspot-induced components and develop a candidate-based low-complexity method that only needs to evaluate the objective at a small set of candidate antenna positions. For the traffic-restricted max--min objective, we develop a block coordinate descent framework where each coordinate update reduces to a one-dimensional subproblem via an epigraph reformulation and bisection. Simulations show that the proposed design outperm.

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arXiv2026

Environment-Aware Network-Level Design of Pinching-Antenna Systems--Part II: Geometry-Aware Case

This two-part paper aims to develop an environment-aware network-level design framework for generalized pinching-antenna systems to overcome the limitations of conventional link-level optimization, which is tightly coupled to instantaneous user geometry and thus sensitive to user mobility and localization errors. Part I investigates the traffic-aware case, where user presence is characterized statistically by a spatial traffic map and deployments are optimized using traffic-aware network-level metrics. Part II complements Part I by developing geometry-aware, blockage-aware network optimization for pinching-antenna systems in obstacle-rich environments. We introduce a grid-level average SNR model with a deterministic LoS visibility indicator and a discrete activation architecture, where the geometry-dependent terms are computed offline in advance. Building on this model, we formulate two network-level activation problems: (i) average-SNR-threshold coverage maximization and (ii) fairness-oriented worst-grid average-SNR maximization. On the algorithmic side, we prove the coverage problem is NP-hard and derive an equivalent mix-integer linear programming reformulation through binary coverage variables and linear SNR linking constraints. To achieve scalability, we further develop a structure-exploiting coordinate-ascent method that updates one waveguide at a time using precomputed per-candidate SNR contributions. For the worst-grid objective, we adopt an epigraph reformulation and leverage the resulting monotone feasibility in the target SNR, enabling an efficient bisection-based solver with low-complexity feasibility checks over the discrete candidate set. Simulations results validate the proposed designs and quantify their gains under different environments and system parameters.

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arXiv2026

Characterizing Multi-Cell Pinching-Antenna Transmission: Revealing the Other Side of the Coin

Using pinching antennas to enhance a user's connection to its own base station (BS) is intuitive and has been well investigated in the literature. This letter focuses on a less intuitive advantage of pinching antennas from the interference-suppression perspective. In particular, using pinching antennas ensures that all BSs serve their users with low transmit power, i.e., BSs can ``whisper", rather than ``shout", to their users. As a result, by experiencing less interference, a user's data rate can still be improved with pinching antennas, even if its link quality to its own BS remains unchanged. A stochastic geometric study is carried out in the letter, where BSs employ fractional power control. Analytical and numerical results are presented to reveal the significant impact of this interference-suppression capability offered by pinching antennas.

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arXiv2026

A Survey of Pinching-Antenna Systems (PASS)

The pinching-antenna system (PASS), recently proposed as a flexible-antenna technology, has been regarded as a promising solution for several challenges in next-generation wireless networks. It provides large-scale antenna reconfiguration, establishes stable line-of-sight links, mitigates signal blockage, and exploits near-field advantages through its distinctive architecture. This article aims to present a comprehensive overview of the state of the art in PASS. The fundamental principles of PASS are first discussed, including its hardware architecture, circuit and physical models, and signal models. Several emerging PASS designs, such as segmented waveguide-enabled PASS (SWAN), center-fed PASS (C-PASS), and multi-mode PASS (M-PASS), are subsequently introduced, and their design features are discussed. In addition, the properties and promising applications of PASS for wireless sensing are reviewed. On this basis, recent progress in the performance analysis of PASS for both communications and sensing is surveyed, and the performance gains achieved by PASS are highlighted. Existing research contributions in optimization and machine learning are also summarized, with the practical challenges of beamforming and resource allocation being identified in relation to the unique transmission structure and propagation characteristics of PASS. Finally, several variants of PASS are presented, and key implementation challenges that remain open for future study are discussed.

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arXiv2026

Frequency-Selective Pinching-Antenna Systems

An uplink pinching-antenna system (PASS) is considered, where a segmented dielectric waveguide is employed to serve multiple users and one pinching antenna (PA) is activated on each segment. Extensive waveguide deployment reduces user-to-PA path loss but also creates differential propagation delays among the PA-assisted paths spanning the large waveguide aperture. These delays are retained, and a Toeplitz block model is derived to characterize the resulting frequency-selective (FS) channel. For infinite-blocklength transmission, the achievable single-user rate and the multiuser sum-rates under joint and parallel decoding are characterized. For carrier-phase-aligned single-user PA placement, the frequency-flat (FF) model is shown to overestimate the exact FS rate. The difference between the rates computed under the FF channel model and the exact FS channel model is referred to as the FF rate overestimation, and its dependence on the waveguide-aperture-induced delay spread is characterized. For small delay spreads, the FF rate overestimation is shown to increase approximately quadratically with the delay spread, whereas a derived lower bound reveals that the overestimation grows at least double logarithmically with the waveguide aperture, or equivalently with the delay spread, in the large-aperture regime. For finite-blocklength transmission, achievable rates are derived under a practical cyclic-prefix single-carrier frequency-domain equalization framework. An element-wise algorithm is developed to optimize FS-aware PA placement in both transmission regimes. The analytical findings demonstrate that differential delays across the extensively deployed waveguide can cause significant frequency selectivity and that the proposed FS-aware PA placement method substantially improves the achievable rate over placement based on the FF approximation, especially for large bandwidths and apertures.

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arXiv2026

Pinching-Antenna Systems: From Antenna Placement to Antenna Roaming

This paper investigates pinching-antenna systems with finite antenna movement speed, under which conventional antenna placement is subject to non-negligible repositioning delay, resulting in a fundamental tradeoff between channel quality and effective transmission time. In this context, antenna roaming is proposed as a novel operation mode, in which the antenna moves continuously along the waveguide while simultaneously serving users. By incorporating communication and antenna movement into the same transmission cycle, a unified cycle-duration framework is established to facilitate a fair comparison between antenna placement and antenna roaming. The sum-rate difference is then analytically derived, indicating that antenna roaming avoids dedicated positioning overhead with a loss in channel quality due to spatial averaging. The corresponding sum rate maximization problems are formulated for the two operation modes. The continuous optimization problems are transformed into finite-state sequential decision problems and solved via dynamic programming (DP) based algorithms. For antenna roaming, the optimal unconstrained service-interval partition is analytically characterized, with each antenna position assigned to the user achieving the highest instantaneous rate. Simulation results validate the theoretical analysis, demonstrate the performance advantage of antenna roaming over antenna placement, especially when positioning overhead is significant, and confirm the effectiveness of the DP based solutions in improving the achievable sum rate.

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arXiv2026

Unlocking Directional Radiation in Pinching-Antenna Systems: Geometry-Aware Design and Experimental Verification

Pinching-antenna systems (PASS) have recently attracted growing interest as a flexible architecture for creating "last-meter" line-of-sight wireless links through dielectric waveguides and reconfigurable radiation points. While modeling pinching antennas (PAs) as isotropic point radiators has enabled tractable analyses and demonstrated the performance gains of PASS, their practical radiation characteristics remain underexplored. This article investigates PASS from the perspective of PA geometry. Starting from the physical coupling principle, we explain why PA shape affects the induced polarization current and incorporate directional gain into the channel model. The full-wave simulations are conducted to show how different PA geometries and orientations reshape the internal field distribution and far-field radiation pattern. A 60 GHz prototype video transmission experiment is further presented to demonstrate the link-level impact of changing PA states. Finally, promising applications enabled by geometry-aware directional PASS are highlighted.

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arXiv2026

Generalized Pinching-Antenna Systems: A Leaky-Coaxial-Cable Perspective

The evolution toward the sixth-generation (6G) wireless networks has flexible reconfigurable antenna architectures capable of adapting their radiation characteristics to the surrounding environment. At the center stage, while waveguide based pinching antennas have been shown to beneficially ameliorate wireless propagation environments, their applications have remained confined to high-frequency scenarios. As a remedy, we propose a downlink generalized pinching-antenna system that adapts this compelling concept to low-frequency operation through a leaky-coaxial-cable (LCX) implementation. By endowing LCX structures with controllable radiation slots, the system inherits the key capabilities of waveguide based pinching antennas. Explicitly, these include reconfigurable line-of-sight (LoS) links, reduced path loss, and flexible deployment, while supporting a practical implementation of the pinching-antenna concept at low frequencies. A twin-stage propagation model is developed for characterizing both the guided transmission and wireless radiation encountered over LoS and non-line-of-sight (NLoS) paths. Analytical results reveal strong local gain, complemented by rapid distance-dependent decay. Hence, we conceive a matching joint optimization framework, which maximizes throughput by harnessing game theoretic association and convex power allocation. Simulation results demonstrate substantial performance gains over conventional fixed-antenna benchmarks.

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arXiv2026

Outage-Constrained Environment Division Multiple Access (EDMA) for Pinching-Antenna Systems

Environment division multiple access (EDMA) has emerged as a promising multiple access paradigm, which mitigates inter-user interference by dynamically adjusting pinching antenna (PA) positions to the underlying propagation environment. This paper investigates a multi-user PA-enabled EDMA framework that accounts for probabilistic line-of-sight (LoS) blockages, random non-LoS (NLoS) scattering, and practical inwaveguide attenuation. With the aim of maximizing the total information rate, we formulate a joint PA deployment and power allocation problem subject to statistical rate outage constraints, the transmit power budget, and the feasible deployment region of PAs. We first consider a canonical two-user two-PA scenario and derive closed-form expressions for the outage probabilities, followed by a low-complexity projected gradient descent (PGD)-based algorithm to address the reformulated problem. Then, we extend our design to the general multi-user multi-PA scenario and derive tractable approximations for the outage probabilities by assuming interfering links to be NLoS and applying the Chernoff bounding technique, where a successive convex approximation (SCA)-based algorithm is proposed to handle the resulting nonconvex problem. Simulations validate the superiority of the proposed PA-enabled EDMA design and the effectiveness of the proposed algorithms. Specifically, both the PGD-based algorithm and the SCA-based algorithm achieve near-optimal performance in comparison with the exhaustive search. Furthermore, the PA-enabled EDMA design yields significant performance gains over both PA-enabled and conventional time division multiple access designs.

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