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.