Tag Archives: millimeter wave radios

5G Needs Fiber

I am finally starting to see an acknowledgement by the cellular industry that 5G implementation is going to require fiber – a lot of fiber. For the last year or so the industry press – prompted by misleading press releases from the wireless companies – made it sound like wireless was our future and that there would soon not be any need for building more wires.

As always, when there is talk about 5G there is a need to make sure which 5G we are talking about, because there are two distinct 5G technologies on the horizon. One is high-speed wireless loops send directly to homes and businesses as a replacement for a wired broadband connection. The other is 5G cellular providing bandwidth to our cellphones.

It’s interesting to see the term 5G being used for a wireless microwave connection to a home or business. For the past twenty years this same technology has been referred to as wireless local loop, but in the broadband world the term 5G has marketing cachet. Interestingly, a lot of these high-speed data connections won’t even be using the 5G standards and could just as easily be transmitting the signals using Ethernet or some other transmission protocol. But the marketing folks have declared that everything that uses the millimeter wave spectrum will be deemed 5G, and so it shall be.

These fixed broadband connections are going to require a lot of fiber close-by to customers. The current millimeter radios are capable of deliver speeds up to a gigabit on a point-to-point microwave basis. And this means that every 5G millimeter wave transmitter needs to be fiber fed if there is any desire to offer gigabit-like speeds at the customer end. You can’t use a 1-gigabit wireless backhaul to feed multiple gigabit transmitters, and thus fiber is the only way to get the desired speeds to the end locations.

The amount of fiber needed for this application is going to depend upon the specific way the network is being deployed. Right now the predominant early use for this technology is to use the millimeter wave radios to serve an entire apartment building. That means putting one receiver on the apartment roof and somehow distributing the signal through the building. This kind of configuration requires fiber only to those tall towers or rooftops used to beam a signal to nearby apartment buildings. Most urban areas already have the fiber to tall structures to support this kind of network.

But for the millimeter technology to bring gigabit speeds everywhere it is going to mean bringing fiber much closer to the customer. For example, the original Starry business plan in Boston had customers receiving the wireless signal through a window, and that means having numerous transmitters around a neighborhood so that a given apartment or business can see one of them. This kind of network configuration will require more fiber than the rooftop-only network.

But Google, AT&T and Verizon are all talking about using millimeter wave radios to bring broadband directly into homes. That kind of network is going to require even more fiber since a transmitter is going to need a clear shot near to street-level to see a given home. I look around my own downtown neighborhood and can see that one or two transmitters would only reach a fraction of homes and that it would take a pole-mounted transmitter in front of homes to do what these companies are promising. And those transmitters on poles are going to need to be fiber-fed if they want to deliver gigabit broadband.

Verizon seems to understand this and they have recently talked about needing a ‘fiber-rich’ environment to deploy 5G. The company has committed to building a lot of fiber to support this coming business plan.

But, as always, there is a flip side to this. These companies are only going to deploy these fast wireless loops in neighborhoods that already have fiber or in places where it makes economic sense to build it. And this is going to mean cherry-picking – the same as the big ISPs do today. They are not going to build the fiber in neighborhoods where they don’t foresee enough demand for the wireless broadband. They won’t build in neighborhoods where the fiber construction costs are too high. One only has to look at the hodgepodge Verizon FiOS fiber network to see what this is going to look like. There will be homes and businesses offered the new fast wireless loops while a block or two away there will be no use of the technology. Verizon has already created fiber haves and have-nots due to the way they built FiOS and 5G wireless loops are going to follow the same pattern.

I think the big ISPs have convinced politicians that they will be solving all future broadband problems with 5G, just as they made similar promises in the past with other broadband technologies. But let’s face it – money talks and these ISPs are only going to deploy 5G / fiber networks where they can make their desired returns.

And that means no 5G in poorer neighborhoods. It might mean little or limited 5G in neighborhoods with terrain or other similar issues. And it certainly means no 5G in rural America because the cost to build a 5G network is basically the same as building a landline fiber network – it’s not going to happen, at least not by the big ISPs.

Wireless Networks Need Fiber

As I examine each of the upcoming wireless technologies it looks like future wireless technology is still going to rely heavily on an underlying fiber network. While the amount of needed fiber will be less than building fiber to every customer premise, supporting robust wireless networks is still going to require significant construction of new fiber.

This is already true today for the traditional cellular network and most existing towers are fiber-fed, although some have microwave backhaul. The amount of bandwidth needed at traditional cell sites is already outstripping the 1 or 2 GB capacity of wireless backhaul technologies. Urban cell sites today are fed with as much as 5 – 10 GB pipes and most rural ones have (or would like to have) a gigabyte feed. I’ve seen recent contractual negotiations for rural cell sites asking for as much as 5 GB of backhaul within the next 5 – 10 years.

Looking at the specification for future 5G cellular sites means that fiber will soon be the only backhaul solution for cell sites. The specifications require that a single cell site be capable of as much as 20 GB download and 10 GB upload. The cellular world is currently exploring mini-cell sites (although that effort has slowed down) to some degree due to the issues with placing these devices closer to customers. To be practical these small cell sites must be placed on poles (existing or newly built), on rooftops and on other locations found near to areas with high usage demand. The majority of these small sites will require new fiber construction. Today these sites can probably use millimeter wave radio backhaul, but as bandwidth needs increase, this is going to mean bringing fiber to poles and rooftops.

Millimeter wave radios are also being touted as a way to bring gigabit speeds to consumers. But delivering fast speeds means getting the radios close to customers. These radios use extremely high frequencies, and as such travel for short distances. As a hot spot a millimeter wave radio is only good for a little over 100 feet. But even if formed into a tight microwave beam it’s a little over a mile – and also requires true line-of-sight. These radios will be vying for the same transmitter locations as mini-cell sites.

Because of the short distances that can be delivered by the millimeter wave radios, this technology is going to initially be of most interest in the densest urban areas. Perhaps as the radios get cheaper there will be more of a model for suburban areas. But the challenge of deploying wireless in urban areas is that is where fiber is the most expensive to build. It’s not unusual to see new fiber construction costs of $150,000 and $200,000 per mile in downtown areas. The urban wireless deployment faces the challenge of getting both fiber and power to poles, rooftops and sides of buildings. This is the issue that has already stymied the deployment of mini-cell sites, and it’s going to become more of an issue as numerous companies want to build competing wireless networks in our cities. I’m picturing having the four major cellular companies and half a dozen wireless ISPs all wanting access to the same prime transmitter sites. All of these companies will have to deal with the availability of fiber, or will need to build expensive fiber to support their networks.

Even rural wireless deployments needs a lot of fiber. A quality wireless point-to-point wireless network today needs fiber at each small tower. When that is available then the current technologies can deploy speeds between 20 Mbps and 100 Mbps. But using wireless backhaul instead of fiber drastically cuts the performance of these networks and there are scads of rural WISPs delivering bandwidth products of 5 Mbps or less. As the big telcos tear down their remaining rural copper, the need for rural fiber is going to intensify. But the business case is often difficult to justify to build fiber to supply bandwidth to only a small number of potential wireless or wireline customers.

All of the big companies that are telling Wall Street about their shift to wireless technologies are conveniently not talking about this need for lots of fiber. But when they go to deploy these technologies on any scale they are going to run smack into the current lack of fiber. And until the fiber issue is solved, these wireless technologies are not going to deliver the kinds of speeds and won’t be quickly available everywhere as is implied by the many press releases and articles talking about our wireless future. I have no doubt that there will eventually be a lot of customers using wireless last mile – but only after somebody first makes the investment in the fiber networks needed to support the wireless networks.