More than a little talk… and deep thinking… is ongoing about 5G NTN, especially where direct-to-device comes into play. Operators are working out their strategies, including the pack leaders who are defining the network architectures that will match their still-developing business plans.
Eutelsat, for example, just announced it is buying 340 additional satellites for its OneWeb LEO constellation. It’s well known that Eutelsat and the IRIS2 program plan to support 5G with these and future satellites. And while a major announcement last week from Blue Origin about its TeraWave constellation didn’t specifically mention 5G, it’s not a stretch to assume it’s at least a factor in their calculations.
One of the biggest questions in 5G NTN architectures for space is where to put the gNodeB. The gNodeB (Next Generation Node B) is the cornerstone radio base station that provides New Radio (NR) connectivity to user devices. In a terrestrial network it lives on the ground (of course), usually at the cell tower.
But what happens in a space network? Now you have two choices: on the ground or in space on the satellite. There are good arguments on both sides depending upon your satellite architecture, orbit, services and more. And depending upon your service areas, partners and customers, you might want a combination of both. The way LEO satellites interact with ground systems, for example, is fundamentally different from GEO.
So, you have to give the 3GPP folks due credit for designing a flexible standard that would support both industry-level interoperability and network-level flexibility.
Take a look at Starlink, for example, which just spent $17 billion to buy spectrum from Echostar. That spectrum that has no value without 5G NTN because it is intended to support unmodified phones.
Starlink’s core service, according to research firm Analysys Mason in a recent white paper, “does not adhere to interoperable networking standards.” According to the report’s authors, the constellation does use a modified form of the 4G core network protocol that achieves certain features, however “these have been adapted slightly for their needs and integrated with in-house software for an overall proprietary solution.”
Starlink will have to move to standard 5G NTN at least for its direct-to-device satellites that will connect to existing LTE-capable devices, using terrestrial spectrum from telco partners such as T-Mobile. The good news is that the 5G NTN standard is specifically designed to ensure interoperability between vendor systems and satellite operator networks. All that’s lagging is the technology implementation of the 5G NTN systems. That’s no small thing, of course, but it is catching up, and operators will have the flexibility to architect networks that will support and evolve with their respective missions, including how they choose to design and manage a cell tower in space.
