A multi-user PA-enabled EDMA framework that accounts for probabilistic line-of-sight blockages, random non-LoS (NLoS) scattering, and practical inwaveguide attenuation is investigated, which yields significant performance gains over both PA-enabled and conventional time division multiple access designs.
Abstract
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.
Environment division multiple access (EDMA) provides a propagation-centric multiple-access framework for pinching-antenna systems (PASS) by using segmented waveguides and line-of-sight (LoS) blockage to partition the service area and reduce inter-region interference. Recent PASS–movable-signal (MS) studies further suggest that carrier-domain actuation can reshape delay-dependent channel responses. Motivated by these developments, this paper studies segmented PASS–MS–EDMA under explicit LoS+NLoS propagation. Unlike earlier PASS–MS works that optimize a generic user-channel matrix for fairness, reliability, beamforming, or sensing, the present work focuses on the EDMA-specific region-to-region coupling matrix induced by one segment, one feed/RF chain, one active pinching point, and one scheduled user per region. We adopt a guided-delay plus radiated LoS/NLoS delay-superposition channel model and show that each diagonal and off-diagonal coupling entry becomes a finite trigonometric polynomial of the common carrier. This yields a soft-partition interpretation of NLoS EDMA: PASS shapes a diagonally favored coupling structure, while MS searches the carrier domain for operating points that reduce cross-region leakage more than they perturb desired in-region links. We identify the delay-visibility boundary under which MS is ineffective, characterize the diagonal/off-diagonal carrier-sensitivity asymmetry, and derive leakage valleys and critical carriers from off-diagonal delay differences. Building on these insights, we develop a two-timescale solver with an inner scalar-link power update and an outer PASS–MS update using adaptive soft-partition certification, critical-carrier refinement, and segment-wise proximal geometry ascent. Numerical results validate the proposed theory under both favorable and weak-asymmetry regimes and show consistent weighted-sum-rate gains over LoS-only EDMA, fixed-carrier NLoS EDMA, and grid-based carrier-search baselines.
Huanxi Cui, Meng Xiao, Jia-Wei Wang et al.· IEEE Transactions on Wireles...· 0 citations
Multiple access (MA) design is investigated to facilitate pinching-antenna systems (PASS)-based multi-user communications. By exploiting the newly introduced waveguide domain and existing frequency domain, two MA schemes are explored, namely pure waveguide division multiple access (WDMA) and hybrid WDMA. For each MA scheme, the corresponding resource allocation problem is formulated to maximize the rate fairness via the joint optimization of pinching beamforming and power allocation. For both schemes, a majorization-minimization (MM)-based alternating optimization (AO) algorithm is proposed that alternately optimizes pinching beamforming and transmit power. A low-complexity framework is further developed, including a two-stage pinching beamforming design and successive convex approximation (SCA)-based power allocation. Numerical results demonstrate that: 1) PASS significantly improve communication rate performance over conventional antenna systems; 2) The proposed MM-based AO algorithm provides higher performance at the cost of increased complexity, while the low-complexity framework achieves comparable performance with lower computational complexity; and 3) Pure WDMA achieves better performance compared to hybrid WDMA, efficiently supporting multi-user communications enabled by pinching beamforming.
Qiao Ren, Xi-Dong Mu, Siyu Lin et al.· IEEE Transactions on Wireles...· 0 citations
In this paper, we investigate the downlink performance of multi-cell RSMA-enabled ISAC networks in which base stations (BSs), communication users, and sensing targets are spatially distributed according to independent Poisson point processes (PPPs). Each BS simultaneously serves multiple users using RSMA while exploiting the common stream as a dual-functional communication and sensing waveform. The users are equipped with FAS that selects the best antenna port to maximize the received signal quality. Closed-form analytical expressions are derived for the ergodic sum-rates by combining stochastic geometry, order statistics, and Laplace-transform-based interference analysis. Furthermore, a tractable approximation for the average radar SINR is developed by characterizing the statistical properties of the common precoder. Leveraging the derived analytical expressions, a low-complexity analytical resource allocation framework is proposed to jointly optimize the RSMA power allocation, the communication-sensing beam tradeoff, and the number of scheduled users while sat- isfying the sensing quality-of-service constraint. Compared with conventional iterative optimization approaches, the proposed analytical design significantly reduces computational complexity while achieving nearly identical communication performance. Simulation results verify the accuracy of the developed analytical expressions and demonstrate substantial improvements in both RSMA sum-rate and sensing performance over conventional transmission schemes.
Abdelhamid Salem, Hana Shamata, Salma M. Elkawafi et al.· 0 citations
Hybrid automatic repeat request with chase combining (HARQ-CC) improves the reliability of slow fluid antenna multiple access (sFAMA) through multi-round combining. However, existing analysis has not fully utilized the structure of densely spaced and highly correlated fluid antenna system (FAS) ports to derive tractable per-round characterizations, thereby maintaining a computationally intensive process. This paper re-investigates downlink HARQ-CC-aided sFAMA with densely-spaced and highly-correlated FAS configuration. Under a spatial block correlation model, we first formulate two validity-corrected high-correlation approximations for the per-round selected-port signal-to-interference ratio (SIR) distribution and its Laplace--Stieltjes transform (LST): a Marcum-Q-kernel route and a lower-complexity step-threshold route. Closed-form expressions are also obtained for block-representative antenna selection (BR-AS) and fixed-position antenna (FPA). Then, the per-round characteristics are used to evaluate the multi-round accumulated-SIR distribution through SIR-domain Stieltjes convolution and numerical LST inversion, yielding the outage probability, average number of transmissions, and payload throughput. Numerical results show close agreement between the two evaluation methods. The analytical FAS results are conservative relative to simulation but preserve the performance trends and receiver ordering. The FAS receiver consistently outperforms the benchmarks, while the payload-throughput gain from increasing the HARQ transmission limit becomes marginal under severe multiuser interference.
Pinching-antenna systems have emerged as a novel promising technology for sixth-generation networks, capable of enhancing spectral efficiency by dynamically creating radiation points and line-of-sight links along a dielectric waveguide. However, the power consumption of such reconfigurable systems remains a critical challenge. This paper investigates a novel flexible hybrid non-orthogonal multiple access (NOMA) strategy for a downlink pinching-antenna system, where the simple two-user scenario is considered for the preliminary analysis of the hybrid NOMA scheme. With the primary objective of minimizing the total transmit power consumption, we formulate the optimization problem that jointly evaluates users’ power allocations and the time-variant locations of the single pinching antenna. To address the coupling between the spatial and power domains, we first derive closed-form power allocation expressions for various channel gain conditions and rigorously establish the feasibility criteria for the hybrid NOMA transmission. Building on this theoretical analysis, a closed-form-assisted reduced-complexity searching algorithm is proposed to determine the optimal antenna locations during different time slots. Numerical results validate the accuracy of the derived closed-form expressions and demonstrate the feasibility of the proposed hybrid NOMA scheme, as well as its ability to achieve superior power-consumption performance compared with conventional benchmarks. Moreover, the results provide valuable analytical insights into the time-varying pinching-antenna positioning, and establish potential applications and a foundational benchmark for hybrid NOMA assisted pinching-antenna systems.
Wen-Qi Huang, Yu-Shen Lin, K. C. Teh et al.· IEEE Transactions on Communi...· 0 citations
This letter investigates the covert performance of a pinching-antenna system (PASS) assisted non-orthogonal multiple access (NOMA) network in a heterogeneous propagation environment. In the considered setup, a pinching antenna is deployed along a dielectric waveguide to flexibly control the radiation position and enhance spatial diversity. Two non-colluding user-specific wardens located in different regions attempt to detect the covert transmission of the legitimate NOMA users. Closed-form expressions for the false alarm probability and missed detection probability for an individual warden are derived by exploiting the statistical properties of the PASS geometry and the Gaussian–Chebyshev quadrature method, based on which the corresponding detection error probability (DEP) is obtained. Numerical results demonstrate that PASS-assisted NOMA significantly improves covert communication performance and increases the warden’s detection uncertainty compared with conventional antenna systems (CASS) assisted NOMA and PASS-assisted orthogonal multiple access (OMA). Furthermore, the impact of imperfect channel state information (CSI) at the wardens on the covert detection performance is also analyzed.
