Everything so far, antennas, beams, spectrum, lives in the RAN, the storefront where your device does business with the network. Behind it sits the core: headquarters. When your phone connects, the core checks who you are (authentication), what you're entitled to (your plan and policies), sets up your session, and routes you to the internet (i.e., it routes traffic to whatever target data network you are trying to reach). You never see it, exactly like you never see a store chain's HQ, but nothing works without it.

Modern cores are pure software built as a Service-Based Architecture (SBA): dozens of small services (one verifies identity, one manages sessions, one, the NWDAF from Module 7, does analytics) that call each other over standard interfaces.

NWDAF, as you may remember, is the Network Data Analytics Function. It is like the smart "brain" of a 5G or 6G cellular core network that constantly collects data on how the network is performing. It uses this data to predict future traffic spikes or slowdowns, helping the network automatically fix issues and run much more smoothly.

LEGO bricks, not a welded appliance. The 6G core discussion is about going further: fewer, simpler bricks, cloud-native from birth, and AI woven.

Physics has one non-negotiable rule: light takes time to travel. A round trip to a data center 1,500 km away burns ~15 milliseconds on travel alone, Module 3's XR budget, gone before any work happens. The fix is Multi-access Edge Computing (MEC): placing computing at or near tower sites and local hubs, so time-critical work happens around the corner.

The analogy: a restaurant chain with one national kitchen makes cold food; opening neighborhood kitchens means hot plates in minutes. Edge kitchens serve XR rendering (Module 3), digital-twin control loops (Module 4), and AI inference (Module 7: remember, train centrally, infer locally). MEC is the quiet enabler stitched through every 6G use case.

Radio sites used to be one-vendor appliances: sealed boxes, one brand top to bottom. If Ericsson was the manufacturing vendor, then we would have all Ericsson gear; no mix and matching with Nokia or Samsung.

O-RAN is the industry movement to standardize the internal interfaces of the radio network, so an operator (like AT&T, T-Mobile, or Verizon) can mix vendors. Open sockets instead of proprietary plugs. It's also where the RIC (Module 7's radio 'brain room') comes from. (Remember, RIC is the RAN Intelligent Controller, the 'brain room' where AI apps observe the radio network and issue optimization instructions.

Alongside openness came a functional split of the radio site's brain: the RU (Radio Unit) handles the antenna-side radio itself; the DU (Distributed Unit) does the microsecond-deadline processing and must stay close; the CU (Central Unit) handles less time-critical functions and can sit farther away, pooled in an edge data center, conveniently, often the same building as MEC.

Let me unpack what I mean by: “an edge data center, conveniently, often the same building as MEC.” MEC (Multi-access Edge Computing) is essentially a mini data center placed close to users so apps, like online games, can load almost instantly without data traveling far away. The sentence means that the network's brain unit (the CU) and this mini data center are often placed in the same physical building to save space and make communication between them even faster.

For 6G, expect this cloud-native, disaggregated style to be the default assumption, not the innovation.

Roughly 10% of the planet's land has cell coverage worth bragging about; oceans, deserts, mountains, and disaster zones have little or none. 6G's answer is the Non-Terrestrial Network (NTN): satellites (and high-altitude platforms) as a coverage layer designed into the system. 3GPP added NTN support in Rel-17 and has expanded it since, including direct-to-phone satellite messaging that ordinary smartphones already use today via partnerships between carriers and satellite constellations.

Orbit matters. LEO (Low Earth Orbit) satellites fly a few hundred km up, close enough for phone-friendly delays, but each covers a small, fast-moving footprint, so you need swarms of them (constellations). GEO (Geostationary Orbit) parks ~35,786 km up, one satellite sees a third of Earth, but the round trip adds noticeable lag. GEO satellites match the Earth's rotation, making them appear completely still relative to the ground; unlike LEO satellites, which race across the sky at around 27,359 km/h or 17,000 mph relative to the Earth to stay in orbit.

The 6G vision is a 3D network: ground towers, aerial platforms, and satellite layers presented to your phone as one seamless service, hiking off-grid, your phone drifts from tower to satellite and back without you noticing. Add sidelink (D2D) - devices talking directly to each other when infrastructure is absent - and 'no signal' starts becoming a historical phrase. While traditional cellular communication follows an Uplink (Device Base Station) and Downlink (Base Station Device) model, Sidelink creates a direct link (Device Device).