5G NR over Satellite Links: Evaluation of Synchronization and Random Access Processes

Integration of 5G new radio (NR) access interface with satellite technology is an ongoing task in the standardization bodies. Since 5G NR was originally designed as a terrestrial system, its direct suitability to satellite communications has yet to be carefully evaluated. In that regard, the initial synchronization and random access processes are among the topics of particular interest. This paper overviews these key processes by first identifying problematic points and then proposing feasible solutions. It is shown that initial synchronization and related data demodulation of the 5G NR synchronization block is possible using dedicated large frequency shift aware receivers. In addition, it is shown that timing advance value, which is a part of the random access process, has to be extended to cover satellite delays. A few ways to do this are discussed in the paper, as well as ways to reduce capacity loss due to required large guard interval of the 5G NR random access signal.