While Satellite communication has been there for a while and matured over the years, incorporating non-terrestrial networks into the 5G ecosystem has made 5G Non-Terrestrial Networks quite interesting. Simply put, it enables 5G user terminals to connect to non-terrestrial networks. The network side components may reside on satellites (as relay node OR complete or partial gNB onboard the satellite) or other airborne platforms (HIBS, UAV, air-to-ground, etc.).
There are various satellite-based connectivity scenarios where satellites are at different altitudes (LEO, MEO, GEO), resulting in different coverage areas. Extending the system to cover [HAPS], [UAVs] etc., will bring even broader coverage and more business cases; for example, UAVs being used for customer deliveries can benefit from the common communication network. It also allows for the introduction of future technologies such as Integrated Sensing and Communication (ISAC).
While LEO/MEO systems for consumer/enterprise communication are at least a quarter century old, they have been plagued by a lack of standardization and, consequently, extremely high-cost structures. While Hughes [GMR-1] was an early attempt to standardize the air interface at least, there has been no grand agreement on this between ISPs, network deployers and handset manufacturers. Consequently, even today, a company attempting to launch a new satellite system will end up designing, engineering, and deploying practically every part of the system, including the user handset, the space segment, the ground station’s core network, etc.
3GPP Release 17 has initiated 5G NTN technology in an attempt to change the entire approach. Keeping with 3GPP’s approach, the first release attempts to standardize the architecture and architectural options. It also tries to maintain a uniform air-interface from the handset’s perspective. This is a commercially sound but engineering-wise extremely complex objective. It means that the existing 5G air interface, designed for terrestrial operation with slow-moving pedestrians or vehicular traffic, will have to be able to work with high-speed satellites (moving at multiple kilometres per second), low-flying UAVs and other extremely novel environments without any significant change on the user handset.