Space and Ground Data Routing via Non-ISL LEO Satellites for Near Real-Time Remote IoT Connectivity

Global Internet of Things (IoT) connectivity is challenged by limited terrestrial coverage, which can be solved by direct-to-satellite Low Earth Orbit (LEO) architectures. However, IoT-oriented LEO connectivity lacks inter-satellite links (ISLs), causing long delays. This paper presents a novel approach for enabling near real-time non-ISL satellite communications for IoT nodes in remote areas. Our method introduces a new data routing architecture that relays critical IoT messages between satellites and ground nodes until reaching a ground station (GS). We formulate the problem as a matrix of visibility waiting times and periods based on satellite orbits and IoT node locations. We then apply three matrix reductions that avoid unnecessary paths, followed by a Dijkstra-based algorithm for optimal message routing. The numerical results show that our proposed algorithm reduces computational complexity by 98% compared to brute-force while achieving the same accuracy in finding the lowest-delay path to GS.