By BUILDER Magazine Staff. One of the great challenges builders face on any new project is how to set up data communications at a site where none exist. For its 444-unit Scripps Ranch project last year, the San Diego division of Shea Homes built a wireless backbone featuring an 18-foot communications tower that delivered data connectivity to 23 field workers in a sales office and two remote trailers.
Mark Hartley, information systems supervisor for Shea's San Diego office, says the wireless network costs slightly under $14,000 to set up but saved Shea $37,500 in telecom gear and communications costs over the 18 months of the project.
"The wireless backbone lets field workers use their laptops and PCs as if they were working off the corporate network in the main office,'' says Hartley, who adds that the wireless backbone delivers 10-megabits-per-second connectivity to the desktop, the standard bandwidth for a corporate Ethernet network.
Shea built the wireless backbone with four Aironet bridges from Cisco Systems. One bridge was set up in the main office, a second was placed in a sales office trailer, and the final two bridges were hooked up outdoors to the communications tower, roughly two miles away from the sales trailer.
Here's how the sites communicate: The main office broadcasts a signal via a 21-inch DBI (decibels per isotropic unit) dish on top of the building pointed to the 18-foot tower. Two 21-inch DBI dishes on top of the tower receive and send the signal. The signal is fed into the two Aironet bridges, which act as repeaters that receive and send the signals. The bridges broadcast the signals to the sales office trailer, which picks up the signal from another 21-inch DBI dish placed on top of the sales office. Shea also set up an Omni directional antenna at the sales office, which broadcasts to two remote construction trailers, each of which has a 12-inch DBI dish. Other gear at the communications tower included a solar panel to create DC power, two standard 70-amp batteries, and a power inverter to change the DC power to AC.
The configuration let Shea establish connectivity to the sales office and two remote trailers without having to pay for any higher speed T1 connections. In the past, the company would have had to run separate T1s to all three sites, which would have meant three extra routers and three set-up fees. Hartley says three routers would cost $6,000, the installations would total $4,500 and annual costs for three T1s would have been $18,000. Hartley says Shea plans to use a variation of this configuration on at least two other projects this year.