2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 19692-19708· 0 citations· 57 references
Computer Science
Abstract
The evolution of sixth-generation (6G) networks increasingly demands seamless and reliable connectivity across heterogeneous and geographically dispersed environments, with maritime regions remaining a major challenge due to vast coverage areas, limited terrestrial infrastructure, and complex propagation conditions. In this paper, we investigate the capacity characteristics of space-air-ground-sea integrated networks (SAGSINs) for maritime communications. Specifically, we consider a SAGSIN system comprising a terrestrial base station (BS), a geostationary satellite, a decode-and-forward (DF) relay, and maritime users randomly distributed according to a Poisson point process (PPP). The relay, implemented by either an uncrewed aerial vehicle (UAV) or a large ship, serves multiple maritime users, providing a unified framework for comparing heterogeneous relay platforms and backhaul options. Based on this model, the system performance is analyzed under two representative fading regimes: 1) quasi-static fading, where analytical expressions and tight upper bounds are derived for the outage probability and corresponding outage capacity; and 2) block fading, where closed-form ergodic capacity formulations are obtained to evaluate the long-term average throughput. Extensive Monte Carlo simulations validate the theoretical analysis and quantify the effects of key system parameters. Our results offer insights into the design and optimization of high-reliability maritime communication links, providing guidelines for practical implementation and future 6G SAGSINs development.
The evolution of sixth-generation (6G) networks increasingly necessitates seamless and on-demand coverage across heterogeneous environments, particularly maritime regions where traditional terrestrial infrastructure is limited. In this paper, we aim to enhance the quality of service (QoS) for maritime users in the 6G space-air-sea integrated networks (SASINs). To shed light on the design of SASIN, we consider a communication model consisting of a single satellite, a single decode-and-forward (DF) uncrewed aerial vehicle (UAV) relay, and multiple maritime users. A novel on-demand coverage performance metric, service efficiency, is proposed to evaluate the QoS of maritime users. Particularly, in order to explore the boundary performance of the proposed architecture, both uplink and downlink communications are analyzed under the assumption of perfect channel state information (CSI). Furthermore, we formulate optimization problems to maximize the service efficiency for both uplink and downlink transmissions, subject to the user scheduling and decoding order, beamforming design, and placement of the relay UAV, respectively. To address the uplink optimization problems, we propose an alternating optimization (AO) algorithm that integrates a greedy randomized adaptive search procedure (GRASP)-based user scheduling algorithm with a successive convex approximation (SCA)-based UAV placement strategy to obtain a high-quality suboptimal solution. Analogously, for the downlink optimization problem, we develop an AO algorithm that combines a low-complexity greedy user scheduling scheme based on an initial beamforming design with the joint optimization of UAV placement and beamforming, effectively balancing performance and computational efficiency. Finally, extensive numerical results demonstrate that the proposed schemes achieve near-optimal performance with significantly reduced complexity, offering a strong solution for high-efficiency SASIN in future 6G maritime communications.
Yingqi He, Jinpeng Xu, Lin Zhou et al.· IEEE Transactions on Wireles...· 0 citations
Simulation results demonstrate that the proposed adaptive scheme demonstrates notable improvements over classical loss-based and delay-based baselines in reducing queuing delays at UAV relay nodes, enhances the transmission efficiency of multi-hop terminals, and effectively maintains end-to-end goodput stability in high-latency environments.
L. Zong, Yun Cheng, Yi Yao· Italian National Conference...· 0 citations
Due to the sparse node distribution and the harsh propagation environment in Maritime Internet of Things (MIoT), traditional local mobile self-organizing networks relying on direct Device-to-device (D2D) communications face limited coverage and frequent link outages. To address these issues, this letter investigates the unmanned aerial vehicle (UAV)-assisted MIoT, where UAVs serve as aerial base stations to provide enhanced coverage. Using stochastic geometry, we develop a system model that consists of the D2D tier and the UAV tier, respectively employing the Fluctuating Two-Ray (FTR) model and Nakagami- $m$ model. Then, analytical expressions of coverage probability and achievable rate, along with their tight upper and lower bounds, are derived. Simulation results validate the theoretical analysis, confirming both the coverage improvement from UAV deployment and the effectiveness of the FTR model. It is further shown that by optimizing the UAV deployment with appropriate density, altitude, and antenna array size, the inter-layer interference can be effectively mitigated thus improving the coverage probability and achievable rate.
Xinyu Du, Xian Zhang, Jiu Xie et al.· IEEE Wireless Communications...· 0 citations
5G New Radio (NR) Non-Terrestrial Networks (NTNs) extend cellular connectivity through Low Earth Orbit (LEO) and Medium Earth Orbit (MEO) satellite constellations while enabling the reuse of downlink NR Positioning Reference Signals (PRS) to provide Positioning, Navigation, and Timing (PNT) services alongside broadband communications. However, the large inter-satellite differential propagation delays inherent to NTN geometry may cause PRS transmissions from non-serving satellites to overlap with the serving-satellite data stream. This paper analyzes this coexistence by deriving a statistical model for the slant-range distribution over the visible spherical cap and extending it to dual-shell constellations through a mixture formulation, yielding a closed-form cumulative distribution function (CDF) of the differential delay. The model is validated using a 10-day orbit simulation representative of a dual-shell European NTN constellation. Detection limits of non-serving satellite PRS under interference from the serving-satellite data stream are characterized in terms of the effective carrier-to-noise density ratio. The impact of periodic PRS transmissions on the uncoded bit error rate (BER) is also evaluated for standardized NR Frequency Range 1 (FR1) and Frequency Range 2 (FR2) configurations. Monte Carlo simulations show that the probability of simultaneous multi-PRS overlap remains below a few percent, depending on PRS duration and repetition period, while PRS detection remains feasible despite data interference. When the PRS is received about 25 dB below the data signal, its impact on uncoded BER is negligible over a wide range of repetition periods, whereas BER degradation increases with PRS duty cycle. These results demonstrate that NR-PRS-based PNT can coexist with broadband downlink in NTN under appropriate PRS periodicity design.
Alejandro González-Garrido, Ottavio M.Picchi, F. Menzione· 1 citation· ⚡1
Simulation results demonstrate the effectiveness of the proposed framework and show that the BD-RIS-assisted system achieves up to a 45.2% sum-rate improvement compared with conventional single-connected RIS (SC-RIS) architectures while maintaining robustness against CSI uncertainty and satisfying all system constraints.
Zain Ali, Muhammad Asif, S. Althunibat et al.· IEEE Access· 0 citations
The rapid emergence of sixth-generation (6G) networks and the low-altitude economy has accelerated the evolution of wireless infrastructures toward air-ground integrated coverage networks (AGICNs), which seamlessly fuse terrestrial and aerial communication resources. However, existing AGICN studies primarily focus on coverage enhancement, while ignoring sustainability. Pursuing sustainable AGICNs introduces new challenges due to the multidimensional resource coupling across heterogeneous air-ground segments. In view of this, this paper presents a comprehensive survey and tutorial on sustainable AGICNs, aiming to balance coverage capacity with carbon efficiency in low-altitude economies. An integrated sensing, communication, and computation (ISCC)-driven architecture, which enables dynamic resource orchestration through closed-loop control, is proposed. We thus introduce a multi-dimensional sustainability metric system, which covers operational efficiency, task-oriented performance, and full lifecycle carbon emissions, to quantify energy and carbon footprints. We review enabling technologies, including artificial intelligence, hybrid precoding, integrated sensing and communication, and simultaneous wireless information and power transfer, and discuss their integration into the ISCC framework to minimize energy consumption while maintaining robust coverage. Experimental results on a real-world testbed demonstrate a 20% reduction in power consumption while achieving over 90% coverage probability, highlighting the feasibility of sustainable AGICNs for future green networks.