5G New Radio in SATCOM: An Overview of Physical and Medium Access Layer Issues

The 3GPP standardization body is actively investigating the requirements and specifying the radio access interface of 5G new radio (NR) systems to support satellite communications. However, the 5G NR was originally designed as a terrestrial system, therefore, there are a few open questions and technological challenges that need to be assessed so as to properly support such non-terrestrial communication systems. In that regard, several related problems and potential solutions have been proposed and evaluated not only within 3GPP working groups, but also by the scientific community including academia and industry. In this contribution, we first overview the recent developments in the random access and physical layer procedures to support satellite communication in 5G networks, identify their limitations and then propose viable solutions. Note that such solutions do not necessarily require to change the standard, but eventually to reparametrize the 5G NR signal based on vendors knowledge of specific deployment scenarios. For instance, we observed that the proper use of reference symbols is required to cope with nonlinear effects due to satellite amplifiers. Our results also show that high reference symbol density is required, while still just fairly low modulation orders can be used.