Abstract:In order to achieve full-time and all-area "ubiquitous connectivity", global coverage, anytime access, and on-demand services in the sky and the earth Integrated network is the future development direction of wireless communication systems. Building an integrated air, space, and ground network requires a deep integration of space-based networks, space-based networks, and ground-based networks to exert their functions in different spatial dimensions, constantly break through the boundary restrictions of the network system, and then achieve full coverage of wide areas and wireless networks of interconnection. This article mainly discusses the development process of the air, space and ground integrated network from the aspects of scientific research project implementation, technical research and standard promotion. At the same time, the application of new technologies in air, space and ground integrated networks is prospected, and the future development direction of air, space and ground integrated networks is discussed.
Keywords:Space, space and ground integrated network; cooperative transmission technology; cognitive radio; non-orthogonal multiple access technology; content Distribution network
1 Introduction
In order to solve the problem of seamless information access at any location, various network services such as space-based, air-based, sea-based, and ground-based are constantly emerging. After five generations of development, the terrestrial wireless communication system is now relatively mature, but there is still the problem of insufficient coverage. In order to achieve the requirements of low latency, high bandwidth, and global coverage, low-orbit (LEO) satellite constellations have gradually become a research hotspot. The development of commercial LEO constellation projects represented by Starlink and OneWeb has made it possible to achieve wireless access to high-speed Internet anywhere in the world. Together with the mature high-orbit (GEO) satellite constellation and the medium-orbit (MEO) satellite constellation, it forms the infrastructure of the space-based network. Compared with terrestrial wireless communication systems, the main feature of satellite communications is that the signal transmission distance is relatively long, so it relies heavily on line-of-sight transmission. If the transmission signal is blocked or fades, the line-of-sight transmission link will become unreliable. For example, users located in densely populated areas in urban centers that are blocked by various high-rise buildings, users in sparsely populated jungle areas blocked by bushes and woods, users indoors, and users at the edge of the beam. At the same time, satellite networks face problems such as complex topology, large transmission delays, and high deployment costs. It can be seen that only