2026· IEEE Transactions on Wireless Communications· Vol 25, pp. 21717-21734· 0 citations· 59 references
Abstract
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.
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.
Jinpeng Xu, Yingqi He, Lin Zhou et al.· IEEE Transactions on Wireles...· 0 citations
6G targets ultra-wide coverage together with ultra-low-latency and ultra-reliable services. To this end, Space-Air-Ground Integrated Networks (SAGINs), which integrate non-terrestrial networks (NTNs) with terrestrial networks (TNs), have emerged as a key candidate architecture. However, legacy resource management methods designed for terrestrial systems are difficult to apply directly due to high mobility and long propagation delays (and Doppler effects) of satellite/aerial platforms, dynamic topologies, and constrained onboard resources. In addition, under short-packet transmission (finite blocklength) regimes, QoS analysis must go beyond average-rate metrics and explicitly ensure latency and reliability simultaneously. This paper surveys resource management for SAGIN/TN-NTN integration through a three-axis taxonomy: (i) resource allocation/scheduling, (ii) mobility/dynamics, and (iii) statistical multi-QoS (latency-reliability) modeling. We compare representative works spanning optimization, graph deep reinforcement learning (Graph DRL), and finite-blocklength-based analyses. We also summarize virtualization/slicing and security/robustness as cross-cutting constraints, and highlight open research challenges.
Minjae Go, Woongsoo Na· International Conference on...· 0 citations
As the telecommunications industry advances towards the realisation of 6G, ubiquitous global coverage has emerged as a key objective. This has driven significant interest in the integration of terrestrial and non-terrestrial networks (ITNTNs), where satellite systems complement terrestrial infrastructure to enable seamless connectivity. However, the global operational scale of satellite systems necessitates cooperation between Low Earth Orbit satellite operators (LEOPs) and local mobile network operators (MNOs), introducing new economic and operational challenges. At the same time, emerging applications are expected to impose strict quality-of-service (QoS) requirements that must be guaranteed across both domains. This paper proposes a QoS-aware tiered pricing framework for supporting users with diverse QoS requirements in an ITNTN. Users are classified into service classes based on empirical traffic characterisation, with each class assigned a dedicated network slice and a target load level linked to QoS guarantees through a queueing-based latency model. The MNO determines class-specific prices that regulate aggregate demand to match these target loads. Numerical results demonstrate that the proposed framework enforces QoS requirements, preserves the desired load hierarchy, and aligns pricing with QoS differentiation, while remaining analytically tractable under heterogeneous user populations.
Simbarashe Tanyanyiwa, O. Falowo· International Conference on...· 0 citations
Non-terrestrial networks (NTNs) have emerged as a promising technology for providing ubiquitous connectivity in remote, underserved, and disaster-stricken regions. In particular, high-altitude platforms (HAPs) can offer wide-area coverage; however, their performance is often limited by severe path loss, multi-user interference, and spectrum-sharing constraints. To address these challenges, this paper investigates a multi-antenna HAP-based underlay aerial-to-ground communication network employing rate-splitting multiple access (RSMA) and assisted by a terrestrial beyond-diagonal reconfigurable intelligent surface (BD-RIS). The objective is to maximize the system sum rate while satisfying user rate requirements, HAP transmit-power constraints, and interference-temperature constraints imposed to protect the primary network. The design further accounts for imperfect channel state information (CSI) through a worst-case robust optimization framework. The resulting problem is highly non-convex due to the coupled optimization of RSMA precoding and BD-RIS beamforming. To address this challenge, the transmit precoding design is reformulated as a convex semidefinite program and solved using successive convex approximation and the MOSEK solver, while the BD-RIS scattering matrix is optimized over the unitary manifold using Riemannian manifold optimization. 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
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
Space–air–ground integrated networks (SAGINs) break through the coverage and capacity limitations of terrestrial networks, providing seamless, high-bandwidth, and highly reliable communication services in remote areas. For end-to-end transmission in the Internet of Things (IoT), the store-and-forward architecture transmits data packets in a best-effort way, resulting in unpredictable latency. The exclusive occupation of links by flows leads to a significant drop in resource utilization. To satisfy deterministic end-to-end communication, this article proposes a quality-of-service (QoS)-aware end-to-end transmission architecture for SAGINs. It comprises two core types of links: access links assisted by high-altitude platforms (HAPs) and backhaul links built around the low-Earth orbit (LEO) satellite. End-to-end flows will be allocated time slots and transmitted hop-by-hop within a single frame to meet deterministic QoS requirements. In this architecture, an optimization problem is designed to maximize the number of successfully scheduled flows with different QoS requirements. To solve the non-deterministic polynomial hard (NP-hard) mixed-integer nonlinear program in dynamic scheduling scenarios, a joint access and transmission heuristic algorithm is proposed. Specifically, to ensure efficient transmission and improve resource utilization, concurrent end-to-end flows are first processed with conflict filtering, followed by hop-by-hop scheduling with the priority based on the least number of required time slots. The simulation results show that, compared to other baseline schemes, the proposed scheme achieves a significant improvement in scheduling performance.
Chen-Yan Lei, Yong Niu, Zhu Han et al.· IEEE Internet of Things Jour...· 0 citations