As 5G networks launch across the world, a word that was previously unknown to consumers — “spectrum” — has become critically important to next-generation wireless devices. Wireless spectrum is invisible, but you can visualize it as a highway divided up into narrow lanes so vehicles can safely travel in parallel between destinations. In the late 1800s and early 1900s, the earliest radio signals were free to travel wherever they could, but subsequent wireless devices such as televisions, radars, satellites, and cellular phones required governments to allocate specific wireless frequencies (spectrum) for individual purposes, creating unseen multi-lane data highways in the air.
Let’s instead picture wireless spectrum as a lake with boats representing different types of data. If the lake has only a few sailboats floating around, collisions would be nearly impossible, even if there weren’t any rules for using the water. But once Jet Skis, motorboats, and yachts show up, rules become necessary to prevent collisions, and eventually, the lake could become so packed with boats that lanes must be established to keep everyone moving.
That’s what’s happened in the wireless communications world. Picture a motorboat stuck navigating a straight but narrow “motorboats only” path, next to physically divided “Jet Ski only” and “yacht only” lanes that can’t be crossed. Even if the motorboat has a powerful engine, it needs to slow down to avoid hitting other boats and the edges of the lane, as well as not creating a wake (interference) that splashes adjacent vehicles.
As we enter the 5G era, engineers have sought new lanes for 5G devices, as well as ways to make already established wireless lanes more efficient by sharing them. If some or all of the vessels could communicate with each other, the “motorboats only” lane could become wider to accommodate two or three different types of vehicles sharing the space, enabling each to stop focusing on not bumping the edges, and go faster whenever other boats aren’t in its way. You might even need those wider lanes to let big new boats into the water.
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That’s effectively the concept behind spectrum sharing. If 4G’s a motorboat, 5G is a hovercraft that benefits substantially from wider lanes. But the hovercraft can’t just expect everything else to clear out of the way when it shows up; it needs to find ways to share the water.
Cellular carriers and regulators have spent roughly two years setting aside 5G-specific spectrum — hovercraft-only lanes. They’ve done this by making use of “millimeter wave” spectrum that wasn’t used by past cellular devices, enabling carriers to purchase super-wide lanes solely for 5G use. Unfortunately, these lanes are expensive to build — perhaps prohibitively expensive — and create other challenges that aren’t easy to quickly overcome. Engineers anticipated these issues, and developed ways for 5G to share older, non-5G spectrum as well.
One of those arrangements is known as dynamic spectrum sharing (DSS), and it lets 5G signals share 4G lanes. DSS effectively enables carriers to prepare existing waterways for a hovercraft future without displacing motorboats or turning one existing 4G lane into two smaller 4G- or 5G-only lanes. The lane lets 4G and 5G traffic through and, as 4G becomes less common, can be dynamically converted largely or fully to 5G use.
Some carriers and devices will support a related 5G technology known as dual connectivity, or EN-DC. In March, SK Telecom used Samsung’s Galaxy S10 5G to simultaneously commandeer 5G and 4G lanes for one huge data pipe, such that 1.5Gbps of 5G lane bandwidth would combine with 1.15Gbps of 4G lane bandwidth to deliver 2.65Gbps total data speeds. Think of it as a hovercraft and motorboat linked together in two lanes — a trick that nearly doubles the S10 5G’s peak performance.
Another sharing opportunity for 5G: wireless lanes used by Wi-Fi routers. Previously, governments have set aside spectrum specifically for Wi-Fi communications, but 5G devices could share the same frequencies when they’re available. Here, the key challenge is respectfully coordinating the Wi-Fi and 5G devices’ use of the spectrum in a way that not only prevents the boats from crashing into each other, but lets them both operate at optimal speeds.
Cellular device makers and carriers clearly want 5G to make better use of existing Wi-Fi spectrum, as well as future adjacent spectrum that governments are in the process of releasing for “unlicensed” (open to multiple users) purposes. The process is ongoing and slow, but appears to be moving forward on both the technology and regulatory sides, particularly as 5G may soon begin to offload some Wi-Fi and wired internet traffic, making cellular connections even more important than before.
In a recent blog post, Qualcomm pointed out that 5G NR-U — a technology that lets 5G signals work on unlicensed spectrum — currently shares Wi-Fi spectrum by manually looking out for other boats and moving only when the waterway is free, a system known as “listen before talking.” That’s better than not sharing spectrum at all. But that process slows 5G down and forces it to wait on Wi-Fi; the goal is to evolve the next 5G and Wi-Fi standards so their signals can be synchronized and work better together. Even if we don’t see that in Wi-Fi 6 routers and devices, it will likely be on the agenda for Wi-Fi 7.
The wireless sector is going to change dramatically over the next decade, as the quantity of data flying through the air is only going to increase — just as it did after radio, television, satellite, cellular, and Wi-Fi signals debuted in past generations. Even though you won’t be able to see the wireless signals themselves, you can be sure that as time goes on, 5G devices will be sharing spectrum with 4G and Wi-Fi devices in ways that will tangibly evolve the ways we work, play, and travel. And as that sharing improves, they’ll continue to get faster, to everyone’s benefit.
