More Dark Fiber to Backhaul Traffic From Small Cells?

There is going to be massive confusion in some quarters as some mobile operators, cable TV providers and others start to think about monetizing their high-capacity local access networks for small cell backhaul. The reason is that "dark fiber networks" traditionally have been built to serve wholesale customers.

It is unlikely that Verizon or AT&T, for example, have strong--if any--motivation to do so. Instead, they will be looking to build their own optical backhaul facilities. Many will call this a dark fiber strategy. That might not be the best term.

Small cell backhaul is just mobile backhaul. As dense as those networks will be, it will make sense to build and own the facilities, rather than pay to use another carrier's assets.

Verizon Communications, for example, has announced it is going to install much more dark fiber  to support existing 4G LTE services, but more importantly to serve as the backhaul network for 5G small cell networks.

Those actions partially will be supported by Verizon’s acquisition of XO Communications. That deal also includes the right to lease  XO’s Local Multipoint Distribution Service wireless spectrum, with an option to buy them in 2018. XO has a portfolio of 102 LMDS licenses in the 28 GHz and 39 GHz bands.

Verizon, in particular, has been looking at backhaul fiber options for several years anticipating that it will be building dense new small cell backhaul facilities to support its 5G network. What remains unclear is whether those “dark fiber” assets will be “lit” to support Verizon’s internal requirements, or might also be sold commercially to other customers.

Such a move would largely be out of character, so one likely can assume the primary use for the new dark fiber to to light it to support backhaul from dense new small cell networks. Just how dense is easy to illustrate.

If, as expected, millimeter wave small cells have a transmission radius of about 50 meters (165 feet) to 200 meters (perhaps a tenth of a mile), Verizon and others will have build backhaul networks far denser than they are used to in the mobile business, but less dense than they routinely deploy in some parts of the high speed access business.

In the past, mobile operators have only required backhaul to macrocells to towers spaced many miles apart. All that changes with new small cell networks built using millimeter wave spectrum (either for 5G mobile or fixed use, or for ISP fixed access).

Right now, a useful analogy is to think about the problem as “fiber to the light pole.”

Keep in mind that street lights are spaced at distances from 100 feet (30.5 meters) to 400 feet (122 meters) on local roads.

As a rough approximation, think of a small cell, in a dense deployment area, spaced at roughly every other street light, up to small cells spaced at about every fourth light pole.

That suggests the sort of dense backhaul network that also will be required. You can argue that a new “fiber to the light pole” network must be built. You can argue that a new mesh backhaul network must be built. You can argue that some other leased backhaul (cable TV network) could be feasible.

In all cases, there are potential business model costs in the backhaul and small cell transmission network that exceed anything engineers have had to design, yet. That is why ots of people now are asking very-practical questions about millimeter wave spectrum and its potential impact on access network business models.

People want to know how far signals will reach, how much rain or snow will affect signal levels, how signals will bend or otherwise get around line of sight issues and how backhaul will be provided.

Impact on the business model for existing and new Internet service providers lies at the heart of those questions. And those are important questions.

Monetizing a new dense small cell network also is among the reasons one hears so much talk about 5G to support fixed Internet access. Adding those new customers is a logical way to add direct incremental revenue for a small cell network that will be fairly capital intensive.
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