5G: Connecting All the Things

28 May 2020 • 8 minute read

Over the last few weeks, each Thursday has been Telecom Thursday (like Taco Tuesday but with guacamobile). Well, except for last week since Cadence had a surprise 4-day holiday weekend announced at the last minute.

Now we come to 5G. In the long run, the world will move to 5G. But in the short run, it just sounds as if it will. In fact, the numbers from the Consumer Electronics Association (who run CES) is that in the US just 20M handsets are forecast to be 5G this year, out of total forecast shipments of 166M. But the forecast for 2021 triples, to 60M out of 167M, as you can see from the chart below. By the way, this chart looks like it is showing the fractions of 100% that go to 5G and 4G, but actually it is a bar graph showing total shipments. The total market in the US is mature and is a replacement market, and it is essentially flat from 2018 to 2023.

Despite all the hype, it is 2021 not 2020 that will really be the era of 5G. My expectation is that by the end of 2021, we will see 5G in major cities and perhaps along the busiest interstate highways. But in rural areas, it will still be 4G and LTE (although AT&T will call this 5G anyway). In a lot of the world, 2G and 3G will continue to be the dominant technologies: they ain't broke so don't fix 'em.

5G is a number of technologies rolled up under one umbrella name.

Frequencies

First, there are three bands of spectrum, known as "low band", "medium band", and "mmWave" (sometimes called "high band"). The low and medium spectrum is often grouped as "sub-6GHz" since those are the radio frequencies used. I don't like "high band" and always say "mmWave" because that band is not the next band up from medium. Medium can go as high as 6GHz, but mmWave starts at 25GHz. There is an enormous gap, and the radio technologies and characteristics of the two lots of spectrum are very different. The precise frequencies actually available vary by country. In particular, the US has a lot of government, military, and satellite spectrum already allocated in what should be the medium band. The FCC is trying to clear some of this, but it is progressing only slowly.

The big differences between sub-6GHz and mmWave are two-fold. First, sub-6GHz can do something that we are used to with our phones, they work indoors even though the basestations are outdoors. The mmWave band is such high frequency that it cannot go through walls and windows, or even a lot of air, where its range is limited to about 300m. There is no mobile phone spectrum in-between sub-6GHz and mmWave. On the other hand, there are almost unlimited amounts of bandwidth with mmWave since there is a lot of spectrum. The thing to avoid doing is expecting to get all the advantages of mmWave (fast speeds, lots of spectrum) in the sub-GHz bands (good building and air penetration). Expect the mobile operators to do their best to confuse you about this in their marketing.

Access Protocols

Prepare for a salad of acronyms. There are four major use cases for 5G: fixed wireless access (FWA), enhanced mobile broadband (eMBB), massive machine-type communications (MTC), and ultra-reliable low-latency communication (URLLC).

Fixed Wireless Access (FWA)

There is an expectation that a major use case for 5G will be to provide internet access to homes in competition with cable TV, DSL, and satellite. This would use mmWave. Other spectrum is too valuable and has too little bandwidth. Since mmWave won't penetrate buildings and will only go about 300m, this would require some sort of fixed tower, with line-of-sight connectivity to an antenna on the outside of each house. Verizon started trials of fixed wireless as long ago as 2018 in 11 markets.

Enhanced Mobile Broadband (eMBB)

This is just better smartphones. You might get higher bandwidth under perfect circumstances, but I think the most likely difference that you will notice from 4G is that there is more network capacity and so you are more likely to be able to get a good data connection even when there are a large number of phones around such as at a major technology trade-show. You are unlikely to notice much difference in transmission speeds on your phone since you typically don't download large files. The largest files are videos, and you simply watch them. If you tether your laptop to your phone, and then start copying large files around, you should see a difference (again, assuming ideal connectivity conditions). One thing that 5G can do, if the network is lightly loaded, is to combine multiple channels that would otherwise be used by two separate phones. It seems that there are big differences between a lightly loaded network with line of sight to a basestation, compared to a heavily loaded network with obstacles around.

A 5G network cannot assume that all users already have a 5G smartphone, and it will be several years before that is even close to true. So 4G services (and perhaps older) also need to be provided from the same basestation, what I suppose we might call "unenhanced mobile broadband".

eMBB is likely to be the main focus of 5G as it starts to roll out over the next few years. Even though 5G is about connecting "things" more than people, the initial focus is likely to be plain mobile broadband, since that's where the business models and demand are well-understood. By the way, "plain mobile broadband" is not actually an official phrase, as far as I know. But Plain Old Telephone Service, or POTS, is the industry name for normal wireline phone service, with no digital stuff like DSL involved. In fact, when DSL was first proposed, it was expected that houses would have a "POTS splitter" that separated the digital broadband from normal phone calls. In the end, it was simpler just to put filters on all the POTS phones so that the digital data didn't interfere with the audio.

Massive Machine-Type Communications (mMTC)

This is the migration path for NB-IoT and LTE-M. NB-IoT is "narrowband internet-of-things". LTE-M is the version of LTE aimed at machines (M apparently stands for "Machine Type Communication" which is a lot of words for one initial). Both of these approaches are intended to support a huge number (think millions) of devices that don't transfer much data at all. These could range from devices spread through a farmer's fields to detect moisture and temperature, to smart security cameras that keep quiet except when they detect something where the alarm has to be raised, or perhaps city garbage cans that signal when they need emptying. All three of these use cases are things that really exist already. These protocols are the opposite of watching a video on mobile, a few kilobits of data occasionally is all that is needed. But there are likely to be many more of these "things" than there are mobile phones (and there are already billions of them).

Ultra-Reliable Low-Latency Communication (URLLC)

This is what it sounds like, mission-critical network services for IoT.

I'm not entirely convinced that all the things that pundits expect this to be used for are realistic. For example, RCR Wireless News says:

URLLC will cater to multiple advanced services for latency-sensitive connected devices, such as factory automation, autonomous driving, the industrial internet, and smart grid or robotic surgeries.

Well, maybe. I just think that it is unlikely that anyone is going to be connecting up their factory automation using a 5G network, as opposed to hard-wired (or even optical), or some sort of privately owned network more akin to your WiFi router at home. Of course, it all depends on how reliable...but the idea that my surgeon has me opened up and then loses 5G connectivity is not something I want to go near.

Network Slicing

The challenge for a 5G network operator is to support all of these technologies on the same network. They have different requirements in terms of bandwidth requirements, latency requirements, and reliability requirements. This necessitates dividing up the network resources in a way that each connection gets appropriate service guarantees and isolation from other services.

mmWave has a whole set of its own challenges, some technical, some regulatory, and some political. The fact that it only goes a limited distance in air means that it only makes sense in areas where a high density of small basestations can be deployed, such as in urban areas with a basestation on every street light or telephone pole. Unlike existing large basestation towers, the cellular carriers have no rights to street lights, so getting those rights will not be instantaneous. Some jurisdictions are likely to introduce similar rules to those when cable-TV was first deployed, forcing the existing owners of poles to share them. Nobody wanted another set of poles in every neighborhood.

But there is a lot of emotional opposition to basestations. I read an interesting article that I forgot to note down about one of the cellular operators having to constantly go to neighborhood meetings where person after person would complain that they never had a headache before in their life and now they are in constant pain, and it is all due to the cell tower. Then, after everyone had had their say, he would point out that they hadn't turned the basestation on yet, they just put up the tower. When, after a couple of months, they did turn on the tower, nobody would notice. One other point he made, which is a bit of an LOL, is that if you are concerned about cellular radiation and schools, then absolutely the best place to put a basestation is on the school roof. There is actually a sort of radio shadow underneath the tower since the antennas face out. Of course, the cellphone reception in the school would be poor...but kids aren't meant to be on their cellphones all the time anyway.

Learn More

A little bit of revision. Learn these terms if you have anything to do with 5G — you will see them a lot:

eMBB (enhanced Mobile Broadband)
URLLC (Ultra Reliable Low Latency Communications)
mMTC (massive Machine Type Communications)

And if what you have to do with 5G is designing electronics, then Cadence has various tools and IP specifically 5G. See 5G Systems and Subsystems on the Cadence website.

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