Designing for Growth

I live in Asheville, North Carolina, where a lot of the neighborhoods like mine have been here for a long time. In fact, most of the houses in my neighborhood were built one hundred years ago – and there are plenty of neighborhoods that are older.

I also live in a city that has been booming over the last decade or two. There have been a lot of new houses built at the fringe of the City and a lot of infill construction where somebody has built a house on almost every vacant lot in the City. Folks are even starting to build houses in what used to be their backyard. I also know of a half dozen multi-dwelling buildings and complexes being built.

This kind of growth means that there is a lot of stress on the existing utilities. Both the electric grid and water system were built for a smaller city, yet each has been expected to somehow accommodate the outward and infill expansion. As you might expect, the over-taxed utilities are showing the strain. There seem to be electrical outages almost every time we have serious rain. We have a few major problems every year with the water system.

Our telecom networks are not immune from growth problems. The Charter cable network clearly has occasional problems. The company never explains problems, but it’s not hard to imagine that there are neighborhoods where the cable network is overloaded due to growth. I also imagine that the Charter network is a hodge-podge of different neighborhoods built over time – it is not one big ubiquitous network but rather a patchwork of smaller networks built in different decades that are all grafted together. That means different generations of coaxial cable, different sizes of cable nodes, and different schemes and designs of taps and amplifiers.

The growth story in Asheville is mild compared to some of the places I’ve lived in my life. In the early 80s, I lived a block outside of the Dallas city limits in Richardson, Texas. At that time, there wasn’t a whole lot in Richardson, which was the outer northern fringe of the suburbs. North of Richardson were places like Plano, which I remember as having a few bars and a rodeo, but which was mostly open country. Today, the Dallas suburbs spread far north of where I used to live forty years ago.

My latest electrical outage made me think about designing fiber networks for growth. There will surely be some fiber networks built with grant funding in rural areas that, over the next fifty years, will be overrun by urban expansion. How easy will it be to expand fiber networks in areas with fast growth?

Passive PON networks are the best at handling growth. The good analogy for thinking of a PON network is to envision one of the many board games that are based upon hexagons. PON technology can handle growth by adding new hexagons as long as the ISP can get enough bandwidth to feed the new neighborhood. A PON network can theoretically handle nearly unlimited growth. If an existing hexagon adds a lot of new homes, it’s just as easy to add new PON core OLTs.

This is not to say that PON networks can’t get into trouble with fast growth. If there had been a PON network in Richardson in the 1980s, there would be a good chance that expansion happened so quickly that there would not have been enough extra fibers in the network to fully handle growth. It’s almost certain that if PON had been in Richardson in the 1980s, there would have been several upgrades to the backbone fiber feeding the neighborhoods to get enough broadband to satisfy customer demand.

Active Ethernet networks have a harder time handling runaway growth. Since there is a last-mile fiber for every customer, it’s not hard to envision adding more homes than existing fiber can handle. There is no real issue expanding active Ethernet into new greenfield neighborhoods, but fast infill growth might mean building new neighborhood fiber at some point.

Not all fiber networks are alike. I know some ISPs today that are building what I consider to be slim fiber networks, meaning a network with a minimum of extra fibers. The chances are that in most rural places this will be okay – but it means a lot of future investment in areas where growth shows up unexpectedly. And that means that it’s going to be important to be served by an ISP that is ready and willing to invest in keeping up with growth. We’ve seen copper and coaxial networks deteriorate when the network owner wouldn’t spend the needed capital.

I am positive that the city planner in Richardson in 1980 did not foresee that Richardson would become a densely populated inner suburb today – or if they did, nobody believed them. Fifty years is a long time, and I’m positive that some of the folks building rural fiber networks will be equally surprised by the growth. But they can make growth easier with some early planning during the original design.

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