5G networks are upon us and this next-generation of wireless communication is being powered by a new technology known as millimeter wave (mmWave). U.S. carriers are particularly keen on the technology, and it will likely be used across the world to varying degrees. However, not every 5G network will necessarily use mmWave technology, at least not all of the time.
As with every new technology, there are inevitable teething problems and hurdles to overcome before it goes mainstream. Millimeter wave technology has had its fair share of doubters in the past few years, with questions arising about its suitability over long distances, how well it can go through walls, and even if rain or a user’s hand might block the signal.
These issues aren’t unfounded, but most of them have been worked out in recent years. MmWave technology is just about ready to make its public debut, so let’s examine the current state of these concerns. First, let’s quickly recap what millimeter wave is all about.
A quick primer on mmWave
MmWave and 5G are used almost synonymously, but there are key differences between the two. The mmWave technology is just one part of what future 5G networks will use. You may also have heard about “low band” frequencies and “sub-6GHz,” both of which will also be part of the standard, and when combined will offer up much faster data speeds to customers, among other benefits.
The term mmWave refers to a specific part of the radio frequency spectrum between 24GHz and 100GHz, which have a very short wavelength. This section of the spectrum is pretty much unused, so mmWave technology aims to greatly increase the amount of bandwidth available. Lower frequencies are more heavily congested with TV and radio signals, as well as current 4G LTE networks, which typically sit between 800 and 3,000MHz. Another upside of this short wavelength is that it can transfer data even faster, though its transfer distance is shorter.
In a nutshell, lower frequency bands cover much greater distances but offer slower data speeds, while high-frequency bands cover much smaller areas but can carry much more data. MmWave is just part of the 5G picture, but carriers are particularly fond of talking about it because it allows for extremely high bandwidth and shows off the most impressive data speed figures.
The objective with mmWave is to increase the data bandwidth available over smaller, densely populated areas. It will be a key part of 5G in many cities, powering data in sports stadiums, malls, and convention centers, as well as basically anywhere data congestion might be a problem. Out in rural towns and villages, sub-6GHz and low bands below 2GHz will probably play a more crucial role in ensuring consistent coverage.
Myth buster: mmWave fact and fiction
mmWave doesn’t penetrate walls
This is perhaps the most common issue cited with upcoming 5G networks and it’s true to some extent. Most building materials, such as cement and brick, attenuate and reflect very high-frequency signals with a big enough loss you’re unlikely to receive a very useful signal moving from inside to outside. Even the air produces signal loss, which limits frequencies above 28GHz to about a kilometer anyway. Wood and glass attenuate high-frequency signals to a smaller degree, so you’ll likely still be able to use 5G mmWave next to a window.
This reflective property works both ways — you don’t need line-of-sight with a 5G antenna to receive the signals. 5G networks will use beamforming to direct waves off and around obstacles to your phone. This works in part because 5G equipment uses multiple antennas to send and receive signals, combining the data from multiple streams to strengthen the overall signal and increase the bandwidth. This works both outdoors, by reflecting signals off buildings, as well as indoors by reflecting signals off walls. Carriers could definitely install beamforming transmitters inside stadiums or large malls.
In summary, very high-frequency 5G signals don’t travel very far and don’t transition very well from indoors to outdoors. However, massive MIMO and beamforming ensure that strict line-of-sight isn’t a requirement to make use of millimeter wave. A mmWave signal may not be able to penetrate buildings, but it will bounce around them to ensure a decent signal. Indoors, people will just have to rely more on rely on sub-6GHz and LTE signals.
It can’t get through your hand either
This is also partially true, for similar reasons mentioned above. Human bodies are reasonably good at blocking high-frequency radio — we’re part water and reasonably dense. That’s partly why Bluetooth headphones don’t always work if your phone is blocked by your body.
While your hand probably isn’t enough to block the entire signal, it could certainly get in the way enough to to make an already mediocre or poor signal worse, useless even. At the very least it could slow down your speeds or cause interrupt the flow of data.
Worst case scenario, grabbing your phone could be the difference between one and zero bars of signal. That’s clearly no good.
There’s a solution to this problem through — placing multiple millimeter wave antennas around the phone. After all, you’ll very rarely cover both sides and the top of your phone at once.
Qualcomm’s reference design suggests three antenna modules should be used in a smartphone to ensure robust signal coverage. Four if you’re moving up to a 5G hotspot that can handle the extra power draw. Speaking of which, these three antenna modules don’t have to all be on at once. Smartphones will switch these modules on and off depending on which ones are receiving the best coverage to reduce the power draw.
5G won’t work when it rains
This sounds pretty damning. It’s not like 5G doesn’t work in the rain at all, but there is some truth to this.
Much like the two previous points, rain in the air adds an extra level of density and therefore attenuation to signals as they travel. Humidity can cause the same problem. This isn’t a new phenomenon for 5G though. “Rain fade” is an issue for modern GPS and other high-frequency satellite communication systems. Granted, those operate all the way out in space, and 5G will potentially suffer issues over just hundreds of meters.
Millimeter-wave signal strength will degrade somewhat when it rains, which will first result in slightly slower speeds and then potentially connection problems. How much it degrades will depend on just how hard it’s raining, and other factors like the distances from the cell tower. Rain will cause the most problems when connecting at the edge of a mmWave base station’s range.
mmWave harms your health
We’ve covered that here, and I won’t dignify the conspiracy theories with anything more than this — no it won’t. Of course, I’ll always welcome new thorough research that helps us understand any risks better, but currently there is credible indication of health risks.
mmWave doesn’t go far enough for good coverage
MmWave is definitely the shortest-range technology being used for next-generation networks, but it’s not so short as to be useless. Base stations will likely offer up to a kilometer of directed coverage, although 500 meters (~1,500 feet) is probably a safer bet, after taking into account obstacles and foliage.
That’s obviously not a huge area. Many more base stations will need to be packed closer together to cover the same areas 4G networks cover now. This is why we’re unlikely to see mmWave deployed out in the countryside or small towns. It will probably only be used in urban centers, where it covers the maximum number of consumers in a small space.
Remember, mmWave is just a small part of the bigger 5G spectrum. the Wi-Fi-like sub-6GHz and low band spectrum should have you covered when high-frequency signals can’t reach you, providing a backbone that still offers fast data speeds.
5G isn’t any faster than gigabit LTE, so what’s the point?
We’ve already seen our first gigabit LTE networks switch on, offering speeds faster than we can really use, so what’s the point in expensive new 5G technologies?
Speed, and to a lesser extent latency, are the two big selling points for consumers, and 5G simply makes this easier to achieve. While 4G LTE can hit gigabit and higher speeds in ideal situations, in many countries there simply isn’t the spectrum or capacity to offer these speeds to every consumer on current LTE networks. 5G is all about increasing the amount of available bandwidth by using a broader range of spectrum, making gigabit and higher speeds easier to achieve.
Furthermore, lots of back-end changes will come with the eventual rollout of the 5G Standalone specification in the coming years. This will result in some more meaningful changes to the types of use cases 5G can power, mass internet-of-things, and smart cities, among others.
5G and mmWave: The next big thing?
MmWave technology is a cornerstone of upcoming 5G networks, allowing for faster data speeds and much higher bandwidth than ever before. The technology has limits, mostly in terms of area and susceptibility to obstruction, but it works. Carriers and equipment vendors like Samsung and Qualcomm claim it works really well. Though carriers love to puff up their fancy new technology, mmWave isn’t the only area of spectrum that will help build next-generation networks.
I’m still on the fence about how meaningful a difference 5G will make to the way we use our smartphones. I’m still waiting for that must-have application, as it were. 5G’s promise of faster data speeds could replace the need for wired fiber, lower latency AR and VR applications, and improve connections on the move, which all sound pretty good to me. MmWave is a key part of building those next-gen applications.
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