Toward Mobile Satellite Internet:The Fundamental Limitation of Wireless Transmission and Enabling Technologies

It has been almost 60 years since the launch of Intelsat-I, the world’s first commercial satellite communications system. Over the past few decades, the development of satellite communications has been driven by both technological advancements and growing application demands, which have given rise to three primary services: broadcast, fixed satellite, and mobile satellite services [1]. Broadcast services, such as those provided by DirecTV and Dish Network, enable the one-way transmission of information to multiple receivers across vast areas. Satellites such as Thaicom-4 and Viasat-3 deliver fixed satellite services, offering broadband access through portable terminals and small ground stations to regions that lack wired or wireless broadband infrastructure. Mobile satellite services, exemplified by providers such as Inmarsat and Iridium, leverage the wide-area coverage of satellites for voice and low-speed data services on handheld terminals, ensuring communication in areas beyond the reach of cellular networks.
Currently, fifth-generation (5G) base stations (BSs) have been widely deployed for cellular mobile communication systems, marking the transition beyond the 5G era. Nevertheless, cellular networks cover less than 40% of the terrestrial surface [2], with only a small fraction of these areas having broadband Internet access for handheld devices through 5G BSs. Consequently, satellite mobile communication is anticipated to play a key role in the evolution of sixth-generation (6G) networks by complementing terrestrial networks (TNs) to provide wireless connectivity with seamless global coverage. To achieve this vision, mobile satellite Internet aims to offer broadband access via portable and ideally handheld devices, further enabling terminal-level integration between TNs and non-terrestrial networks (NTNs). This 6G vision also drives the deployment of cellular radio access networks on satellite regenerative payloads, paving the way for a unified protocol framework. Under this unified framework, the advanced technologies developed for cellular mobile communication systems can be leveraged to satisfy the performance requirements of mobile satellite Internet, while existing cellular infrastructure and economies of scale can be reused to significantly reduce industry costs. However, since cellular protocol frameworks were originally designed for TNs, their applicability to NTNs remains an active area of research, with ongoing efforts underway to develop corresponding technical solutions.
Along with the integration of TNs and NTNs, the selection of appropriate satellite types plays a critical role in enabling ubiquitous connectivity. Low-Earth-orbit (LEO) satellites have emerged as a promising candidate for mobile satellite Internet, owing to the low launch cost, transmission latency, and path loss enabled by their low orbital altitude. However, while the low orbital altitude of LEO satellites offers these advantages, it also limits the coverage area of individual satellites and shortens the visibility duration over given locations, thereby necessitating the deployment of ultra-dense constellations to achieve seamless global coverage. In recent years, advancements in LEO satellite manufacturing and reusable launch vehicle technologies have stimulated the emergence of LEO mega-constellations, driving significant engineering efforts and commercial innovations in mobile satellite Internet [3]. A prominent example is SpaceX’s Starlink, which aims to deploy over 42 000 LEO satellites on several different orbit altitudes to provide global broadband Internet services [1]. In December 2024, SpaceX completed Starlink’s first direct-to-cell (DTC) LEO constellation, enabling unmodified fourth-generation (4G) long term evolution (LTE) handheld terminals to achieve Internet connectivity in remote areas [4].
In addition to being driven by demand and technology, the engineering and commercialization of satellite communication systems are constrained by manufacturing capabilities and costs due to the inherent characteristics of satellite communication, which include long-distance radio propagation and limited onboard power. When discussing the engineering development of satellite communications, starting from the mathematical essence of satellite-to-ground wireless transmission provides valuable insights into the fundamental limitations and potential avenues for transmission capability improvement. By assessing the tradeoffs between the performance gains provided by technologies and their engineering feasibility, alongside commercial costs, it is possible to critically evaluate existing advancements and conceptualize enabling technologies for mobile satellite Internet.