Location-Based Timing Advance Estimation for 5G Integrated LEO Satellite Communications

Integrated satellite-terrestrial communications networks aim to exploit both the satellite and ground mobile communications, thus providing genuine ubiquitous coverage. For 5G integrated low earth orbit (LEO) communication systems, timing advance (TA) is required be estimated in initial random access procedure order facilitate uplink frame alignment among different users. However, due inherent characteristics of LEO e.g., wide beam coverage long propagation delays, existing terrestrial TA scheme not applicable networks. In this paper, we investigate location-based estimation for systems. We obtain time difference arrival (TDOA) frequency (FDOA) measurements downlink synchronization phase, which are made from at instants. propose take these either UE geolocation or ephemeris estimation, calculating value. The then formulated as a quadratic optimization problem whose globally optimal solution can obtained by penalty algorithm. To reduce computational complexity, further an alternative approximation method based on iteratively performing linearization equality constraints. Numerical results show that proposed methods approach constrained Cramér-Rao lower bound (CRLB) assure