The 2017 Mobile World Congress trade show kicks off next week, and in addition to the plethora of new smartphones, 5G network news is expected to show up in a big way. But what exactly is 5G? Is that the same as gigabit networks? LTE Advanced? Is the whole thing just a marketing trick, like when AT&T and T-Mobile renamed HSPA+ as “4G” data to cover for their lack of LTE support?

What is 5G?

In the simplest possible definition, 5G is the fifth generation of cellular networking. It’s the next step in mobile technology, what the phones and tablets of the future will use for data, and it should make our current LTE networks feel as slow and irrelevant as 3G data seems now.

To recap, the first generation of mobile networks (retroactively referred to as 1G) came out in around 1982. It was a fully analog system until the launch of 2G (second generation networks), which made the jump to digital when it launched in 1991. 2G also added cellular data in the forms of GPRS and EDGE technologies. Roughly 10 years later, 3G networks launched, offering an even faster data rate than 2G. Around 10 years after that, our current LTE networks — what we call 4G, although there’s some contention on what that really means — is the fourth generation of networking. Historically, that works out to a new generation of networking technology every decade or so. 5G networks will presumably offer a similar leap forward when it comes to things like data speed.

When is 5G coming?

Working off that model, in the best case scenario, we could see commercial 5G phones in the early 2020s, assuming the same “every 10 years” pattern as previous generations holds through. LTE began to roll out (at least in the United States) in around 2010–2011, so some simple math shows that we should expect to see 5G in 2021, which is coming up quick. Chances are, we’ll see some earlier deployments even sooner than that, if the network providers, modem manufacturers, and wireless carriers are able to live up to their early projected roadmaps. Qualcomm plans to make its early 5G products available to the public as soon as the 2018 Winter Olympics in South Korea. Like the jump from 3G to LTE, you will need a compatible phone to take advantage of 5G when it does roll around, but you’ve still got a few years to figure that out — obviously, we’re not expecting to see any 5G phones launching at MWC this year.

How is 5G different from 4G?

The most important thing to know about 5G is that there is no official “5G” yet. No matter what we hear at MWC this year, no matter how fast the speed test demos, or how different the networking technologies that companies use are, 5G is still a glimmer of an idea in the distance.

A 5G network will have specifications beyond those for 4G, but it hasn’t even been been agreed upon yet what those technical goalposts should even be (there is, however, a logo.) As former FCC chairman Tom Wheeler noted last summer, “If anyone tells you they know the details of what 5G will deliver, walk the other way." Expectations for commercial 5G range from internet speeds in the gigabit or even tens of gigabits range and vague goals of lower latency, but at this point in time we simply don’t know what 5G will truly look like.

That said, there are some ideas of what we can expect. Companies like Verizon, AT&T, Intel, and Qualcomm are already spinning up tests for 5G technology, and it’s these early experiments that will likely shape what the formal international standard for 5G becomes. One of the commonly cited features for 5G is the use of millimeter wave (mmWave) band transmission, which could be the key to unlocking the blazing-fast internet speeds that 5G promises.

What is mmWave technology? Why is it better?

Cellular technology transmits data over radio waves, which depending on the type of electromagnetic signal is measured as a different frequency. The higher the frequency, the smaller the wavelength, so millimeter wave technology refers to signals with a wavelength that’s measured in millimeters, and is generally defined as between 30 GHz and 300 GHz. For 5G, the FCC has already made available swaths of the spectrum in the millimeter wave range for both licensed and unlicensed use as of last summer for companies to begin exploring 5G options (specifically, licensed use in the 28 GHz, 37 GHz, and 39 GHz bands, unlicensed use in the 64-71 GHz band, and shared access in the 37-37.6 GHz band).

Why do we care? Because millimeter wave technology promises higher data capacity than we currently have now. A simplified rule of thumb to go by is the higher the frequency, the more data it can transmit. So, FM radio, which transmits just audio, typically broadcasts at between 87.5 to 108.0 MHz, but LTE — which is responsible for far larger data — streams between 700 MHz to 2,100 MHz (i.e., 2.1 GHz). Millimeter wave technology would offer the bandwidth for orders of magnitude of improvement over LTE. We’ve already even seen commercial use of millimeter wave technology in things like the Starry Beam. (This trend continues up the electromagnetic spectrum into visible light, which has a frequency between 430–770 THz — that’s up to 770,000 GHz — which is one of the reasons why fiber optic technology is so fast.)

Another advantage to the shorter wavelengths found in millimeter wave technology is that antennas used to transmit and receive the signals can be made comparably smaller. That means that phones that use millimeter wave technology could take advantage of multiple antennas for different millimeter wave bands in a single device, which could result in a more efficient use of the available spectrum and faster internet when multiple users are connected.

Millimeter wave technology comes with its own challenges, however. With higher frequencies comes shorter transmission ranges, and shorter wavelengths tend to experience greater issues when there’s no direct line of sight, along with interference from walls, buildings, window panes, and even raindrops. Whereas older radio and cellular technology were able to rely on a comparatively smaller amount of larger antenna towers, millimeter wave would need lots of smaller antennas peppered around cities and countries to function well. It’s technological issues like these that the early 5G tests will be looking to explore and solve.

Gigabit LTE / LTE Advanced / LTE Advanced Pro (or, I want it now!)

Usable 5G technology is still years away, though (again, there isn’t even a defined specification yet). And while LTE doesn’t deliver gigabit speeds, it’s possible that LTE Advanced and the recently finalized LTE Advanced Pro might serve as a stopgap. LTE Advanced is already available on a variety of phones, and carriers like Verizon, AT&T, and Sprint are beginning to support it on their networks. LTE Advanced Pro is the next evolution of LTE that might make practical gigabit mobile internet a reality, as well as begin to lay the groundwork for technologies that for 5G, including things like MIMO (multiple antennas) technology and use of unused spectrum in the 5 GHz LTE-U band. LTE Advanced Pro is also being set up to be a more widespread alternative build on existing technology to offer potentially gigabit level speeds for when 5G rolls out, to ensure a similar networking experience when outside of the fledging 5G areas (similar to how HSPA+ 3G networks helped bolster connectivity while LTE was rolling out).

LTE Advanced is also taking advantage of a technology called carrier aggregation as a stopgap for existing LTE to reach higher speeds. It works by allowing a device to use multiple LTE bands simultaneously to allow for increased bandwidth, and therefore, increased speed. LTE is theoretically capable of aggregating up to five channels for the best speed rates, but the most we’ve seen on the market yet is three-channel aggregation, which Sprint recently rolled out.

The 4G problem, or tempering expectations

It’s also worth remembering to temper expectations. While on paper, LTE Advanced could offer gigabit speeds, and LTE Advanced Pro is specced for up to 3 gigabits per second, that almost certainly won’t translate directly to the real world. In fact, what you (and cellular network marketing departments) think of as “4G” or LTE isn’t really 4G according to the agreed upon standards from the International Telecommunication Union (the ITU) and the 3GPP. Per those standards, a 4G network (among other things) would provide a 100 megabit/s data rate when moving and a 1 gigabit/s while stationary, something that our current networks certainly aren’t capable of yet (LTE Advanced and Advanced Pro are hoping to succeed as the true candidates for a “real” fourth-generation mobile network.) So it’s possible that the dreams of gigabit LTE and 5G may not quite pan out as promised, or if they do, that the timetable could be longer than expected.

Where do we stand now?

Well, going into MWC, expect to hear a lot of news about ongoing 5G developments as both network and hardware companies work to have the technology in place (whether it turns out to be millimeter wave or something else entirely) to build a true fifth-generation network. We’re already starting to see news in that vein this week — Verizon announced plans for 5G testing with millimeter wave hardware in multiple cities across the US, AT&T is planning to test its own more unspecified “5G Evolution” network later this year, and Intel, Qualcomm, and Samsung all announced new chipsets that can support gigabit LTE speeds.

So while the exact details of future cellular networks — whether LTE, 5G, or beyond — may still be a little hazy, there’s one thing we can say for certain: the future will be fast.

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