When we say “5G” almost everyone thinks of their phone downloading videos faster. It is true, but it is only part of the story. The fifth generation of mobile networks was designed from scratch with three big families of services in mind, and to understand it you have to look not only at speed, but at spectrum, antennas and a network architecture that no longer resembles that of the old phones.
More than speed: the three big use cases
The 5G standard, defined by the 3GPP (the body that coordinates the evolution of mobile networks), organizes its goals into three blocks called eMBB, URLLC and mMTC. The nomenclature sounds like engineering jargon, but each acronym answers a different problem.
eMBB (Enhanced Mobile Broadband) is the one we know: more download speed and more capacity to transmit data, designed for high-resolution video and augmented reality. URLLC (Ultra-Reliable Low-Latency Communications) targets communications with ultra-low latency and very high reliability: the domain of the autonomous car, remote surgery or industrial automation, where a delay of milliseconds can make the difference. And mMTC (massive Machine Type Communications) is the least flashy but the most numerous part: connecting millions of low-power sensors and devices, the heart of the internet of things.
A single network that has to serve at the same time an 8K television, a surgical robot and a fleet of smart meters. That forced every layer to be redesigned.
The spectrum: from low bands to millimeter waves
Everything transmitted through the air travels in radio waves, and each service has a portion of the electromagnetic spectrum assigned to it. The big novelty of 5G is that it can work in a much wider range than 4G, and depending on the frequency it uses, the network behaves very differently.
In the low bands (below 1 GHz) coverage is enormous and the waves go through walls without a problem, but capacity is limited. In the mid bands (around 3.5 GHz, those used by most urban deployments) there is a reasonable balance between coverage and speed. And in the millimeter waves or mmWave (above 24 GHz) the capacity is brutal, but the waves barely get through obstacles: a pane of glass or even rain can degrade the signal. That is why a real 5G network usually combines several bands and lets the device choose the most suitable one at each moment.
OFDM: dividing up the spectrum
To make the most of the spectrum, 5G uses a technique called OFDM (Orthogonal Frequency Division Multiplexing). It is simpler than it sounds: instead of sending the data in a single burst, the available spectrum is divided into thousands of very thin subcarriers and the data is spread across all of them at once, in parallel.
That “orthogonality” (the subcarriers are mathematically designed not to interfere with each other) allows packing a huge amount of information into the same slice of spectrum. In addition, the network can assign more subcarriers to the users who need them most at each instant, and do so in fractions of a millisecond.
Massive MIMO and beamforming: antennas that “aim”
Another of the big differences is in the antenna. 4G used a few antennas per sector; 5G uses massive MIMO (Multiple-Input Multiple-Output), arrays with dozens or hundreds of radiating elements working together. By combining so many signals, the base station can send multiple data streams to the same device at the same time, multiplying the speed.
In addition, beamforming is applied to that array: instead of emitting the signal in all directions like a plain light bulb, the station calculates, with the information it receives from each device, where to point a beam of concentrated energy. It is like going from a light bulb to a laser pointer: the signal travels further and with more quality, and since each beam can be directed at a different user, the same physical space serves many more people.
The architecture: NSA, SA and the next-generation core
5G is not just about radio. The transport network also changed. The first deployments used the NSA mode (Non-Standalone), where the new 5G radio relies on the 4G core network so as not to have to build the whole infrastructure at once. The next step is the SA mode (Standalone), with its own 5G core, necessary to exploit all the promises of latency and slicing.
That core, called 5GC (5G Core), largely abandons dedicated physical equipment and is built on virtualized software functions, separated into blocks that can scale independently. Control signaling is separated from user data, and management decisions are made in a distributed way. All that software usually runs in data centers, not on each antenna tower.
Network slicing: cutting the network into tailor-made slices
One of 5G’s most distinctive capabilities is network slicing. The idea is that a single physical infrastructure is divided into multiple logical “slices”, each with its own latency, bandwidth or reliability guarantees.
The operator can reserve a slice with ultra-low latency for the autonomous car, another of high capacity for streaming and another of minimal consumption for sensors, all over the same physical network. It is the same principle as virtual machines, applied to the network: each service sees its own “custom” network without having to build a separate one.
And security?
A network that connects half of the planet’s objects needs to take care of authentication. 5G keeps the SIM card system as the identity base, but introduces a mechanism called SUCI (Subscription Concealed Identifier): instead of sending the device’s permanent identifier over the air in clear, an encrypted version is sent that the operator decrypts in the network core. Thus, a device listening on the radio cannot track a user simply by capturing their subscription identity.
The future that is already here
5G is being deployed in parallel with edge computing, which brings servers closer to where data is generated to cut latency. That combination of new frequencies, antennas that aim, software that virtualizes and a network that is cut into slices is what really sets this generation apart from the previous ones. Speed caught the attention; the architecture is what will change how the internet works in the coming years.
