2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 21481-21496· 0 citations· 43 references
Computer Science
Abstract
Different from existing works that mostly considered multiple access in either the far-field or near-field, we consider in this paper a new and practical scenario, and propose the concept of location division-assisted non-orthogonal multiple access (LD-NOMA) in mixed-field (near-field and far-field) communications to suppress multi-user interference and further enhance system spectrum efficiency. Specifically, we formulate an optimization problem to maximize the spectrum efficiency for all users under a total transmit power constraint by optimizing user clustering, hybrid precoding design, and power allocation. To gain useful insights, we first consider a two-user mixed-field NOMA system, deriving a closed-form solution for spectrum efficiency and analyzing the impact of channel correlation on it, while establishing the criteria for applying mixed-field LD-NOMA. Interestingly, we find that the coverage area of NOMA clusters is significantly expanded compared to that in previous near-field NOMA systems, due to the energy-spread effect in mixed-field scenarios. Furthermore, we extend the two-user mixed-field LD-NOMA to a multi-user scenario, develop a location/correlation-based user clustering algorithm, and present an overall framework for the deployment of LD-NOMA in multi-user mixed-field communications. Finally, simulation results validate the effectiveness of the proposed LD-NOMA in mixed-field communications.
This paper examines the power consumption (PC) efficiency of a mixed near- and far-field (MF) simultaneous wireless information and power transfer (SWIPT) system underpinned by a hybrid beamforming (HB)-based modular extra-large multiple-input-multiple output (XL-MIMO) array. Multiple information decoding (ID) and energy harvesting (EH) users are served by multiple constituent subarrays in both the near-field (NF) and far-field (FF) region of the transmit array. A novel decision method is proposed for accurate classification of different field users using Frobenius norm-based frequency correlation of the least square (LS) channel estimates. The NF spatial non-stationarities (SnS) effects entail distinct electromagnetic (EM) visibility regions (VRs), which can be customized to employ strategic activation of the constituent XL-MIMO subarrays. We formulate a two-tier joint optimization problem to minimize the overall PC, considering the power allocation (PA) for both ID and EH users in addition to the subarray activation (SA). This challenging mixed-integer problem is transformed into computationally tractable formulations, accompanied by the development of well-optimized algorithms. Our simulation results demonstrate an overall PC reduction for our proposed PA-SA-HB scheme by up to 93% against the equal PA with full array (FA) and up to 18% with respect to the PA-FA-HB case.
Muhammad Zeeshan Mumtaz, M. Mohammadi, H. Ngo et al.· IEEE Transactions on Communi...· 0 citations
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.
Weihao Mao, Yang Lu, Yanqing Xu et al.· 0 citations
This paper investigates asymmetric spatial modulation (ASM) for multi-user multiple-input multiple-output (MIMO) systems operating in the near-field (NF) region. Considering spherical-wave propagation, closed-form expressions for the average bit error probability (BEP) of both users are derived under maximum likelihood (ML) detection. The analytical framework is validated through Monte Carlo simulations using five million transmitted symbols. Numerical results compare the near-field (NF) and far-field (FF) channel models. When users are located in the NF region, for example at a distance of 0.2 m from the array, the NF model achieves lower BER across the entire signal-to-noise ratio range. At an SNR of 20 dB, the BER gap between NF and FF increases from approximately 1.65e-3 for 16 transmit antennas to about $\mathbf{5. 0 1 e}-\mathbf{3}$ for 32 transmit antennas. The proposed ASM scheme also provides comparable BEP performance for the two users while enabling simultaneous transmission within the same MIMO resource block. These results show that near-field spatial characteristics can be effectively exploited for multi-user transmission in large-scale and high-frequency MIMO systems.
Quynh Nhu Nguyen, Do Hoang Anh, Thai-Hoc Vu et al.· IEEE International Conferenc...· 0 citations
This paper investigates a near-field (NF) multiple-input multiple-output (MIMO) communication system equipped with dual uniform planar arrays (UPAs). We first develop a generalized geometric model to calculate the 3D distance between arbitrary antenna elements across the transmitter and receiver panels. Leveraging the distance analysis, we derive a closed-form near-field to far-field (NF-FF) boundary for dual-UPA configurations. By exploiting the geometric structure of the UPAs, we further decompose the near-field channel matrix into a Kronecker-product of two lower-dimensional matrices. This decomposition enables a low-complexity NF beamforming design for achievable-rate maximization. Numerical results validate the analysis and demonstrate that the conventional Rayleigh distance is a special case of the generalized model. Furthermore, the proposed beamforming design achieves near-optimal rate performance while significantly reducing the computational complexity compared to state-of-the-art NF beamforming methods.
Lingeng Zheng, Xing Hao, Ziru Chen et al.· 0 citations
A more superior hybrid M/T-NOMA cognitive communication scheme is proposed, in which the system will adaptively select the one with higher system throughput between M-NOMA and T-NOMA as the final transmission scheme.
Yafang Zhang, Ye Tian, Haixia Li et al.· Scientific Reports· 0 citations
To address the dual demands of high data transmission and energy supply in sixth-generation (6G) networks, this paper investigates near-field wideband simultaneous wireless information and power transfer (SWIPT) with power splitting for multiple mobile stations. To mitigate the beam splitting effect, we introduce fully- and sub-connected delay-phase precoding (DPP) architectures. Under energy harvesting constraints, we formulate a sum spectral efficiency maximization problem by jointly optimizing phase shifter (PS)- and true-time-delay (TTD)-based analog precoders, digital precoders, power allocation, and power splitting factors. We reveal controllable beam splitting and beam focusing phenomena in near-field wideband DPP, which can be flexibly adjusted through TTD and PS tuning. For the fully-connected DPP, we propose an efficient beam training scheme via frequency-domain angle search and time-domain distance search. Moreover, for the sub-connected DPP, we develop a structured precoding approximation matching (SPAM) mechanism. Based on beam training results, we design information decoding-oriented and energy harvesting-oriented digital precoders to balance the spectral efficiency-energy harvesting trade-off. Finally, we propose an alternating optimization framework and a low-complexity sequential quadratic programming method to solve the joint power allocation and splitting optimization. Simulation results demonstrate that the proposed schemes achieve superior spectral and energy efficiency in near-field wideband SWIPT systems.
Junjie Li, Jie Zhang, Liang Yang et al.· IEEE Transactions on Communi...· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
