Enhancing the physical layer of 6G non-terrestrial networks: position-independent synchronization

In fifth-generation (5G) wireless systems, support for non-terrestrial networks (NTN) was added. Physical layer challenges in the deployment of 5G NTN systems include the dependence of synchronization on the position of the user equipment (UE) that is derived using a global navigation satellite system (GNSS) and on the position of the satellite. In this paper, a solution is presented for position-independent synchronization of sixth-generation (6G) NTN systems. By using a combination of open-loop and closed-loop uplink corrections, the timing and frequency errors can be minimized at the receiver side, without the need for GNSS-based pre-compensation. By means of simulations, lab emulations, and over-satellite testing, we prove that synchronization can be achieved without GNSS and without any signal-to-noise ratio degradation, and with mobility of the satellite and UE.