Architecture, RF analysis and build of the wireless canopy over the One Spark downtown festival footprint: forty-two Xirrus high-density access points mounted on traffic engineering poles across downtown Jacksonville, carrying all data transport for the event.
Built on the traffic signal plant
The signals downtown are controlled over fiber, so there is already fiber at every intersection, in cabinets that already have power, on poles that already have height and placement exactly where crowds gather. The canopy was built on that. Access points went up on the traffic engineering poles, landed on layer-2 switches inside the signal cabinets, and backhauled over the traffic engineering fiber plant. The path from that network back to the datacenter was redesigned to carry it, and a firewall was configured as the enforcement point for the separation described below.
Almost nothing had to be built. One piece of municipal infrastructure supplied the mounting, the power, the cabinet, and the backbone — which is the difference between a festival network that is worth doing and one that is not.
The fallback is the part worth dwelling on. Each intersection could also reach its neighbors over a Ubiquiti wireless mesh, standing by in case the fiber failed. That is path diversity, but not the usual kind: the backup path is a different medium, not a second fiber on a different route. A downtown fiber failure is usually mechanical — a backhoe, a pulled duct, a damaged splice — and a second fiber inherits most of that risk because it shares the same trenches, the same poles and the same contractors. A radio path between intersections shares none of it. The failure that takes the primary out has no purchase on the backup.
Three networks, not one
The canopy carried three separated networks off the same physical plant:
- Administrative — festival operations and staff.
- Public — attendee access across the footprint.
- Secure — the point-of-sale kiosks.
That third one is why this is an architecture problem rather than a coverage problem. The kiosks took payments. Card transactions were crossing a temporary outdoor radio network, in a crowd, on poles in the street — and they had to be segregated from the public network sharing the same air and the same access points. Segmentation is the ordinary answer in a building with a wiring closet. Doing it on street furniture, standing it up for a few days and taking it down again, is the same requirement without any of the usual comforts.
Sized for the week, not the year
Internet capacity for the festival was provisioned at 500 Mb for the seven days, against a standing baseline of 50 Mb. A tenfold burst, bought for a week and given back.
That ratio is the honest measure of what an event network is. Everything about it — the arrays, the mesh, the firewall rules, the bandwidth — exists at festival scale for a few days a year and at nothing like that scale the rest of the time. The design question is never “what does this need to carry”, it is “what does this need to carry on the worst afternoon, and what does it cost to keep the rest of the year”.
What the network was carrying
One Spark ran in downtown Jacksonville from 2013, promoted as the world’s largest crowdfunding festival. Creators exhibited across the urban core and the public voted on which of them received money. By published accounts the first festival drew about 130,000 people to roughly 900 creators and 406 projects across 59 downtown venues. The second drew 260,000. The third, in April 2015, drew more than 320,000 and remains the largest the event ever held.
That growth is the number that matters to whoever owns the radio design. The same downtown footprint had to absorb a crowd two and a half times larger across three consecutive Aprils, on a network struck and rebuilt each year rather than left standing to be tuned.
And voting and donating ran through a mobile app and the kiosks, so the wireless was not an amenity laid on for visitors’ convenience — it was the path the festival’s central mechanism ran over. A venue network that degrades under load is an irritation. A festival network that degrades under load stops people voting and stops the kiosks taking money, at the moment the crowd is densest, which is exactly when it is least forgivable.
Why outdoor high-density inverts the problem
Indoors, walls are the obstacle and also the gift: they attenuate, which separates cells and lets channels be reused. In the open there is nothing to contain a cell. Every access point hears every other one, co-channel interference rises with the density that was meant to solve the capacity problem, and the client population is almost entirely handheld — low transmit power, held at chest height, inside a body-absorbing crowd that was not there on the day of the survey.
So the design goal inverts. Coverage is trivial in open air; the work is capacity and containment — antenna patterns chosen to cut a cell down rather than throw it far, pole geometry that puts the crowd inside a controlled pattern instead of at the ragged edge of a wide one, and a channel plan across forty-two radios that still holds when the site fills. The mesh has to be planned inside that same spectrum budget, because a fallback that only works when the network is quiet is not a fallback.
Outcome
A festival network assembled almost entirely from infrastructure the city already owned — the poles, the cabinets, the power and the fiber that runs the traffic signals.