5G Networks and Neighborhoods

With all of the talk about the coming 5G technology revolution I thought it might be worth taking a little time to talk about what a 5G network means for the aesthetics of neighborhoods. Just what might a street getting 5G see in new construction that is not there today?

I live in Asheville, NC and our town is hilly and has a lot of trees. Trees are a major fixture in lots of towns in America, and people plant shade trees along streets and in yards even in states where there are not many trees outside of towns.

5G is being touted as a fiber replacement, capable of delivering speeds up to a gigabit to homes and businesses. This kind of 5G (which is different than 5G cellular) is going to use the millimeter wave spectrum bands. There are a few characteristics of that spectrum that defines how a 5G network must be deployed. This spectrum has extremely short wavelengths, and that means two things. First, the signal isn’t going to travel very far before the signal dissipates and grows too weak to deliver fast data. Second, these short wavelengths don’t penetrate anything. They won’t go through leaves, walls, or even through a person walking past the transmitter – so these frequencies require a true unimpeded line-of-sight connection.

These requirements are going to be problematic on the typical residential street. Go outside your own house and see if there is a perfect line-of-sight from any one pole to your home as well as to three or four of your neighbors. The required unimpeded path means there can be no tree, shrub or other impediment between the transmitter on a pole and each home getting this service. This may not be an issue in places with few trees like Phoenix, but it sure doesn’t look very feasible on my street. On my street the only way to make this work would be by imposing a severe tree trimming regime – something that I know most people in Asheville would resist. I would never buy this service if it meant butchering my old ornamental crepe myrtle. And tree trimming must then be maintained into the future to keep new growth from blocking signal paths.

Even where this can work, this is going to mean putting up some kind of small dish on each customer location in a place that has line-of-sight to the pole transmitter. This dish can’t go just anywhere on a house in the way that satellite TV dishes can often be put in places that aren’t very noticeable. While these dishes will be small, they must go where the transmitter can always see them. That’s going to create all sorts of problems if this is not the place in the home where the existing wiring comes into the home. In my home the wiring comes into the basement in the back of the house while the best line-of-sight options are in the front – and that is going to mean some costly new wiring by an ISP, which might negate the cost advantage of the 5G.

The next consideration is back-haul – how to get the broadband signals into and out of the neighborhood. Ideally this would be done with fiber. But I can’t see somebody spending the money to string fiber in a town like Asheville, or in most residential neighborhoods just to support wireless. The high cost of stringing fiber is the primary impediment today for getting a newer network into cities.

One of the primary alternatives to stringing fiber is to feed neighborhood 5G nodes with point-to-point microwave radio shots. In a neighborhood like mine these won’t be any more practical that the 5G signal paths. The solution I see being used for this kind of back-haul is to erect tall poles of 100’ to 120’ to provide a signal path over the tops of trees. I don’t think many neighborhoods are going to want to see a network of tall poles built around them. And tall poles still suffer the same line-of-sight issues. They still have to somehow beam the signal down to the 5G transmitters – and that means a lot more tree trimming.

All of this sounds dreadful enough, but to top it off the network I’ve described would be needed for a single wireless provider. If more than one company wants to provide wireless broadband then the number of devices multiply accordingly. The whole promise of 5G is that it will allow for multiple new competitors, and that implies a town filled with multiple wireless devices on poles.

And with all of these physical deployment issues there is still the cost issue. I haven’t seen any numbers for the cost of the needed neighborhood transmitters that makes a compelling business case for 5G.

I’m the first one to say that I’ll never declare that something can’t work because over time engineers might find solutions for some of these issues. But where the technology sits today this technology is not going to work on the typical residential street that is full of shade trees and relatively short poles. And that means that much of the talk about gigabit 5G is hype – nobody is going to be building a 5G network in my neighborhood, for the same sorts of reasons they aren’t building fiber here.

Li-Fi

Light bulbThere is another new technology that you might be hearing about soon. It’s called Li-Fi and also goes by the name of Visible Light Communications (VLC) or Optical WLAN. This technology uses light as a source of data transmission, mostly within a room, and will compete with WiFi and other short-distance transmission technologies.

Early research into the technology used fluorescent lamps and achieved data speeds of only a few Kbps. The trials got more speed after the introduction of LED lighting, but the technology didn’t really take off until professor Harold Haas of the University of Edinburgh created a device in 2011 that could transmit at 10 Mbps. Haas calculated the theoretical maximum speed of the technology at the time at 500 Mbps, but recent research suggests that the maximum speeds might be as fast someday as 1.5 Gbps.

There are some obvious advantages of the technology

  • Visible light is totally safe to people and eliminates any radiation issues involved in competitors like 802.11ad.
  • It’s incredibly difficult to intercept and eavesdrop on Li-Fi transmissions that stay within a room between the transmitter and receiver.
  • It’s low power, meaning it won’t drain batteries, and uses relatively simple electronics.

But there are drawbacks as well:

  • The speed of the transmission is going to be limited to the data pipe that feeds it. Since it’s unlikely that there will ever be fiber built to lightbulbs, then Li-Fi is likely to be fed by broadband over powerline, which currently has a maximum theoretical speed of something less than 1 Gbps and a practical speed a lot less.
  • At any reasonable speed Li-Fi needs a direct line-of-sight. Even within a room, if anything comes between the transmitter and the receiver the transmission stops. Literally waving a hand into the light bean will stop transmission. This makes it awkward to use it for almost any mobile devices or something like a virtual reality headset.

There are a few specific uses considered for the Li-Fi technology.

  • This possibly has more uses in an industrial setting where data could be shared between computers, machines, and robots in such a way as to insure that the light path doesn’t get broken.
  • The primary contemplated use of the technology is to send large amounts of data between computers and data devices. For example, Li-Fi could be used to transmit a downloaded movie from your computer to a settop box. This could be a convenient, interference-free way to move data between computers, phones, game consoles, and smart TVs.
  • It can be used at places like public libraries to download books, videos, or other large files to users without having them log onto low-security WiFi networks. It would also be great as a way to hand out eCatalogs and other data files in convention centers and other places where wireless technologies often get bogged down due to user density.
  • Another use is being called CamCom. It would be possible to build Li-Fi into every advertising display at a store and let the nearest light bulb transmit information about the product to shoppers along with specials and coupons. This could be done through an app much more quickly than using QR codes.

The biggest hindrance to the technology today is the state of LEDs. But Haas has been leading researchers from the Universities of ­Cambridge, Oxford, St. Andrews, and Strathclyde in work to improve LEDs specifically for the purposes of Li-Fi. They have created a better LED that provides almost 4 Gbps operating on just 5 milliwatts of optical output power. These kinds of speeds can only go a very short distance (inches), but they hope that through the use of lenses that they will be able to transmit 1.1 Gbps for up to 10 meters.

They are also investigating the use of avalanche photodiodes to create better receivers. An avalanche photodiode works by creating a cascade of electrons whenever it’s hit with a photon. This makes it much easier to detect transmitted data and to cut down on packet loss.

It’s likely at some point within the next few years that we’ll see some market use of the Li-Fi technology. The biggest market hurdle for this and every other short-range transmission technology to overcome is to convince device makers like cellphone companies to build the technology into their devices. This is one of those chicken and egg situations that we often see with new technologies in that it can’t be sold to those who would deploy it, like a store or a library, until the devices that can use it are on the market. Unfortunately for the makers of Li-Fi equipment, the real estate on cellphone chips and other similar devices is already very tightly packed and it is going to take a heck of a sales job to convince cellphone makers that the technology is needed.