A Survey on Nongeostationary Satellite Systems: The Communication Perspective

The next phase of satellite technology is being characterized by a new\nevolution in non-geostationary orbit (NGSO) satellites, which conveys exciting\nnew communication capabilities to provide non-terrestrial connectivity\nsolutions and to support a wide range of digital technologies from various\nindustries. NGSO communication systems are known for a number of key features\nsuch as lower propagation delay, smaller size, and lower signal losses in\ncomparison to the conventional geostationary orbit (GSO) satellites, which can\npotentially enable latency-critical applications to be provided through\nsatellites. NGSO promises a substantial boost in communication speed and energy\nefficiency, and thus, tackling the main inhibiting factors of commercializing\nGSO satellites for broader utilization. The promised improvements of NGSO\nsystems have motivated this paper to provide a comprehensive survey of the\nstate-of-the-art NGSO research focusing on the communication prospects,\nincluding physical layer and radio access technologies along with the\nnetworking aspects and the overall system features and architectures. Beyond\nthis, there are still many NGSO deployment challenges to be addressed to ensure\nseamless integration not only with GSO systems but also with terrestrial\nnetworks. These unprecedented challenges are also discussed in this paper,\nincluding coexistence with GSO systems in terms of spectrum access and\nregulatory issues, satellite constellation and architecture designs, resource\nmanagement problems, and user equipment requirements. Finally, we outline a set\nof innovative research directions and new opportunities for future NGSO\nresearch.\n