Case Study: Texas State Fair
But if you are one of the people charged with looking out for the kind of criminal activities that inevitably take place when you draw a crowd of thousands together in one place, size becomes a problem.
Keeping tabs on the crowds at the fair, which takes place every September at the 126-year-old Fair Park near downtown Dallas, is an enormous undertaking. The park houses museums, 37,000 square feet of exhibit space, and acres of grassland, and also hosts events year-round at the Cotton Bowl stadium and outdoor amphitheaters.
What's more, the park has been declared a national historic landmark, so it is not the kind of place you can dig up willy-nilly just to lay some cable.
The Dallas Police Department had already been using mesh equipment from Firetide Inc. for video surveillance. So when the State Fair was looking for a suitable system in August 2004, the police recommended a system from AgileMesh, based on its own video servers and software, the fair’s video cameras, and a HotPort wireless mesh network from Firetide to carry the data from the cameras to the park's command center.
The cameras connect by short Ethernet cables to nearby Firetide HotPort outdoor mesh nodes, which provide wireless connectivity for the cameras, video servers, and monitoring stations. Cameras can also receive power via these Ethernet ports, eliminating the need for additional cabling.
The nodes don't work like traditional 802.11 access points, which all need to be connected to a wired LAN via an Ethernet cable. Instead, the nodes "talk" to each other, forming an instant radio network that requires far fewer connections back to the wired world.
The state fair started its network in 2004 with four HotPoint nodes supporting six cameras -- four along the midway and two cameras on top of the Cotton Bowl. The network has since expanded.
"I've got six cameras on the midway right now," says Rusty Fitzgerald, director of operations for the state fair. "Four more in the parking lot...
"We'll probably be adding more cameras," he adds, noting that at the moment the network covers approximately half the site.
Fitzgerald says that it took about a day to set up the equipment and a week to tweak it so that everything worked right. There were, however, some teething troubles with the Firetide gear.
"We started out with one of their new systems, and it didn't work very good," notes Fitzgerald. "So they sent us some experimental units, and then replaced them with new production units... The support was great."
Cheaper than cable
The Firetide outdoor units use a casing that is designed to stand up to the elements. So far, they've stood up to rainstorms and high winds, says Fitzgerald.
"If we have some lightning storms, then there may be some problems... but its just a simple reset." Costs for the network vary according to location. For instance, in the fairground's vast parking lot, cameras are mounted on tall poles that only get power when the lights are switched on at night. These had to be fitted with a special battery pack that charges at night so they can operate throughout the day.
Overall, Fitzgerald estimates that it would cost between $20,000 and $25,000 to install a system supporting six cameras. Which makes the AgileMesh system cheaper than running cable, according to Fitzgerald -- not that this was an option for him in some areas that are paved with six-inch-thick concrete.
Obviously, the viewing range covered by these installations depends on the cameras used. "I can get pretty close to a mile if I've got clear line of sight," says Fitzgerald. He estimates that he could store up to two weeks of footage from six cameras on his 100-Gbyte hard drive.
"Right now, I'm real happy with it," he declares. "I can zoom in and move around with no delay or pauses." — Dan Jones, Site Editor, Unstrung