Why is it that the focus of 5G discussions is a space that’s relatively unimportant? Why are we largely ignoring the most promising piece of 5G? I’ve been talking to enterprises, operators, and vendors on 5G for months, and over the last month I’ve focused on this underrated piece—millimeter wave. Here’s what I found, and why this particular technology option should be front-and-center for anyone looking for a 5G revolution.
I got interested in enterprises and millimeter wave when I was doing a quick survey of enterprise attitudes on private 5G, something I blogged about last week. The problem I found was that enterprises were getting a technology-centric vision of private 5G, not a goal-centric vision. Given that they needed business cases to adopt something, this was leaving them without a realistic path forward. I started talking about the enterprise potential of millimeter wave, and found that most had never been pitched on it, but most could in fact see a realistic mission set that could drive its deployment.
There’s also a real mission for millimeter wave in public 5G applications. I’ve run the numbers with many operators, and they’ve told me that there is real potential for “significant” deployment of millimeter wave. In some areas of the world, the potential is described as “compelling”, and yet even combining this with enterprise interest doesn’t seem to be promoting millimeter wave as a concept. That’s why I propose to look at it in more detail here.
There are two broad flavors of 5G technology. The one most people have heard of, and some are even using, is the mobile version. This is designed to support smartphones and other mobile devices, and is a logical evolution from earlier cellular mobile standards, notably 4G/LTE. The other one is millimeter-wave. Unlike mobile 5G, millimeter wave is really aimed at replacing fixed wireline broadband, particularly the relatively low-speed DSL. It’s an alternative to fiber to the home (FTTH) and a competitor to cable. However, you can in fact support mobile users with millimeter wave, as we’ll see.
Millimeter wave is called that because the wavelength of the spectrum used is very short—millimeters. For those who care, a millimeter is 0.03937 inches. Most people are more accustomed to seeing frequency measurements in Hertz, or in the mega- or giga-Hertz variant, so millimeter wave is generally considered to be between 30 and 300 GHz, where traditional mobile 5G would typically be using spectrum below 5GHz.
The disadvantage of millimeter wave is that as radio frequencies get higher, they tend to act like radar, bouncing off stuff instead of going through it to the customer. Millimeter wave doesn’t go through buildings or even heavy foliage as well, and so it’s generally considered to be a shorter-range technology, good for up to perhaps five miles depending on things like antenna heights and large obstructions. It’s also limited in its ability to support direct-to-user connections within a building.
There are three advantages that can more than offset these issues, for at least some missions. The first is that the information-carrying capacity of spectrum is directly related to its frequency, so millimeter-wave stuff could carry more bandwidth per spectrum unit. The second is that more bandwidth per allocated channel is available, further multiplying capacity, and the final is that there’s more available spectrum in that range than in the cellular ranges.
Some operators have cited another potential benefit, which is that 5G mm-wave isn’t necessarily “5G” in an implementation sense. It’s in a kind of interesting transitional zone, between multipoint microwave and cellular networking. This can give operators interesting options, and create a truly compelling business case for private millimeter-wave 5G.
I’ve noted in some earlier blogs that the business case for mm-wave 5G isn’t hard to find. Wireline replacement is all about finding a way to approach the baseline bandwidth choice of consumers (around 200 Mbps) with a lower “pass cost” (the cost to get broadband to an area so that it can be sold and connected) and per-customer connection cost. Legacy CATV cable achieves a pass cost of perhaps $180, and for new installations it’s on the order of $220. FTTH pass costs are averaging almost $600, and none of these technologies can be self-installed. The 5G/FTTN hybrid’s pass costs are highly variable depending on the topography and household density of the target service area, but they can range from as low as $150 to as high as $350.
Some operators say that you can self-install the 5G/FTTN hybrid, by attaching the antenna to a window facing the right direction, which does seem to be a bit of coordination to identify the right direction for the antenna to face. Only the operator knows the location of the FTTN node relative to the home and windows. This is very much like the installation of an over-the-air TV antenna. Once the antenna termination is inside, it’s hooked up to a “modem” that provides in-home WiFi connectivity (or, with suitable equipment, Ethernet direct connection).
It’s this easy setup of what could be a multi-hundred-megabit broadband connection that makes this approach appealing for private 5G. Companies that have a campus, or even that have multiple sites located relatively close to each other, could feed broadband to one and use the 5G mm-wave hybrid to cover others, either through point-to-point or using the primary feed as the “node”. This application could be called “5GINO” (5G in name only) because the only thing it really needs from “5G” is the spectrum and radio technology.
For both public or private applications, mm-wave could be revolutionary. It’s likely that the public 5G/FTTN mission will work out the details and provide an early market for antennas, radio elements, and so forth. This would facilitate broader adoption by lowering costs. Even the FTTN nodes could become almost commodity items, and broad private millimeter-wave adoption could drive costs down even more.
There are a few different requirements for private millimeter-wave installations, the most notable being the ability to frequency-hop to respond to interference in unlicensed spectrum. This same problem occurs with WiFi (particularly in dense residential areas) so it’s not rocket science to address it.
Millimeter wave doesn’t need to be limited to wireline replacement, either. Remember that a normal mm-wave installation would feed a local WiFi router. Any smartphone with WiFi calling would then be able to take advantage of the wider spread of broadband across a campus or large facility, and still have traditional cellular service available.
Would it be possible for an enterprise to deploy a mobile 5G service using unlicensed spectrum? The emerging approach for this involves two technologies. The first is “LAA” for “License-Assisted Access”, and the second is NR-U, for “New Radio-Unlicensed”. LAA emerged with 4G and Evolved Packet Core, and NR-U is a pure 5G option. You can run “standard” 5G on unlicensed spectrum with NR-U, or run it with a cellular “anchor” using LAA. Among enterprises I’ve chatted with, there is virtually zero knowledge of either LAA or NR-U, which shows that if there’s any real presentation of private 5G going on, it’s not exactly insightful. The reason may be that enterprises see any network capability that’s a conglomerate of standards an invitation to integration hassles and finger-pointing when something goes wrong.
That doesn’t disqualify millimeter wave as a technology useful to enterprises, though. In fact, it would be easier to use 5G mm-wave and WiFi to support calling from within a facility, than to adopt either NR-U or LAA, providing of course that your primary cellular carrier(s) supported WiFi calling. There’s no question that a pure 5G approach could offer more features, but given the fact that WiFi calling works fine for millions today, it’s not clear whether the additional pure-5G capabilities are needed.
What about IoT, though? Well, obviously WiFi 6 could support all the WiFi IoT applications we have today, and many more besides. You can use Basic Service Set Coloring to balance QoS over multiple WiFi zones, and it supports both high-capacity devices and low-power-and-bandwidth devices. Again, I don’t dispute that there are applications it won’t work for (mobile IoT) and that there are more that pure 5G could do better, but how much “better” will most IoT need?
My point is simple. You can make a good business case for millimeter-wave 5G, in both public and private 5G applications. It does everything we can do now, but better and cheaper, and it hybridizes nicely with WiFi 6. That’s important because WiFi calling and WiFi IoT are proven solutions to provable opportunities—we have them now and it’s working. Even without any attempt to co-utilize mm-wave 5G for mobile devices, it’s the form of 5G that has the cleanest business case for deployment. Add in the mobile dimension and it could be a killer step toward not only public but private 5G as well.
A little respect, please?