Automatic Train Operation (ATO) is a new growing market in the railways sector since 2019. Several railways operators such as SNCF, DB, SBB and so on have launched deep transformation in their infrastructures and rolling stock in order to enter in digital era. One of this game changers is upgrading to autonomous train on existing or new infrastructure. Since autonomous train means the absence of train driver, there is a big need of uplinked information to supervise autonomous trains from the ground. This includes the need of remotely driving the train if it encounters a problem, e.g. a non-recognised obstacle, an infrastructure breakdown. Remote driving will be a new operation mode in the railways sector that will rely on a well-designed radio link provided by 5G. This paper presents preliminary results on test tracks with Long Term Evolution (LTE) and a simulation based comparison between LTE and 5G at physical layer using Non orthogonal Multiple Access