QoS-Aware End-to-End Transmission Scheduling for Space--Air--Ground Integrated Networks

Abstract

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.