Under the Sea

Wireless gets much better down where it's wetter.

by / March 2, 2006
The San Francisco Bay Area has garnered a reputation as a premier locale for high-tech innovation. Residents can count on being connected virtually anywhere they go -- thanks to the gee-whiz gadgetry of nearby Silicon Valley.

The Bay Area consists of three major cities -- San Francisco, San Jose and Oakland -- and their many orbital suburbs. The community is connected in another vital way as well. From the coastal cities of Richmond, Oakland and San Francisco to inland cities such as Fremont, Concord and Pleasanton, the Bay Area's public transportation system is considered by many to be a lifeline for residents and visitors alike.

Bay Area Rapid Transit (BART) has been a mainstay since the first passengers boarded in 1972. Since then, BART has grown with its passengers and expanded to meet their needs. Still, the blistering pace of technological advancements requires BART to adapt faster than ever before.

Making Connections
Much of the Bay Area boasts wireless connectivity. Powerful cellular signals beam voice and data access to thousands, and almost every coffee shop, office building and shopping center sports a Wi-Fi hotspot. Even BART passengers can use their mobile devices to wirelessly access e-mail, the Internet or other applications ... unless they're in a tunnel.

There are more than 30 miles of subterranean track in BART's rail system. The longest tunnel is also the most vital: The Transbay Tube, which stretches 135 feet below the icy waters of the bay, connects Oakland and San Francisco via 3.6 miles of track, tunnel and darkness. For commuters, wireless access on BART ends as soon as the train plunges below the ocean depths -- cellular signals simply cannot penetrate the sea and soil to reach passengers.

Chuck Rae has been with BART since opening day and currently serves as telecommunications revenue manager. As the technology became available, Rae said BART began considering how to provide wireless access underground.

"Above ground, your wireless providers pretty much cover transit systems just by virtue of the cell sites being in close proximity," Rae said. "[The difficulty begins] when they hit the underground tunnels."

The solution was a distributed antenna technology known as Radiax. BART has used Radiax cables for years to maintain internal communications on train radio. Adapting the Radiax technology to handle subterranean cellular communications puts BART at the forefront of underground wireless connectivity.

Rae explained how the first four BART stations were connected -- and eventually how the entire Transbay Tube will be.

"Think of Radiax as coaxial cable with leaky holes in it," Rae said. "It's a fat co-ax with a lot of windows in it. We call that a distributed antenna. Instead of antenna every 6 inches, you use this cable and that's the distributed antenna. The RF [radio frequency] leaks out and comes [into the train]. It's a simple system really."

To prove to a skeptical board of directors that the need existed, Rae and his staff surveyed BART passengers in early 2001.

"We did an actual passenger survey and it came back favorably that the majority of people would like to see it," he said. "[BART] did a phone survey and actually did one by interviewing people in the stations. So it was a good sampling of the patrons.

"Then when 9/11 hit, I think it magnified it in the sense that it would be nice to have communications in case something did happen."

In 2002, BART sent out an RFP requesting that a telecommunications company finance and develop an underground wireless system for BART tunnels. At the time, BART employed a third-party developer, the Andrew Corp., makers of Radiax, as part of the RFP, which resulted in telecommunications companies balking at the opportunity. No one committed to the project.

"The carriers said, 'Why do we have to go through a third party and pay them to do what we can do?'" Rae recalled.

Tired of delays, Rae went to the board of directors seeking to amend BART's master license agreement (MLA). At the time, the MLA stipulated that all area cellular carriers had equal access to providing wireless access along BART routes. The trouble was that it only pertained to above-ground cellular towers.

"I went to the board, and I put together a plan. I developed a rate structure," Rae said. "I devised a program that said to the carriers, 'We can amend the master license agreement above ground that lets you go below ground.' But here's the program. There are 16 below-ground stations and all the connecting tunnels -- the lucrative part of our system is Civic Center to Oakland, that's where all the trains go and that's the heavy traffic. For the carriers to build in the Transbay Tube and the Berkeley Hills Tunnel, [they] have to agree to occupy and build in the 16 underground stations. And they said OK."

The Bay Area cellular carriers -- Nextel (now Sprint Nextel) Verizon, Cingular and T-Mobile -- met with Rae to discuss who would lead the project development. Cingular initially stepped up to fund major development costs but later moved aside to allow Nextel, which had more available development dollars, to take the lead.

"Chuck realized that the carriers were going to have to drive this," said Steve Dutto, Nextel project manager. "So he got us all together, and at the time, Nextel just kind of had the budget for this type of project. We discussed it, and the terms with Chuck were that if we built it, it had to be technology-agnostic -- you had to treat all the carriers the same and everyone had to be allowed into the system."

BART's MLA states a provision of equal access for all carriers that want to participate. Furthermore, the cost to each carrier that wants to build infrastructure and participate is the same multilaterally. As such, Rae assembled a very unlikely committee consisting of local executives for all the carriers.

The newly amended MLA called for a carrier license agreement allowing the four companies to build and operate a network underground. Each carrier pays BART for the right to use the tunnels to expand its network -- in essence paying rent on the tunnel.

"Let's just say T-Mobile and Cingular are in there and Verizon is not," Rae hypothesized. "Customers will say, 'Why should I go to Verizon then? I want to be able to use my BlackBerry.' So it's about maintaining market share. That was great for BART because all we did was take advantage of that. We have the real estate. That's all we bring to the program. So it really was a win-win for the carrier, BART and the people riding."

In addition, the carriers consented to a maintenance and warranty agreement. Coincidentally the vendor of choice for this agreement ended up being Andrew Corp.

Phase One
The first phase of the project began in 2003. It was agreed that the carriers would build the initial underground network segment in the four busiest BART stations -- Civic Center, Powell Street, Montgomery Street and Embarcadero -- after which BART trains make their dive under the bay.

The trick to the whole project was how to get a wireless signal to passengers more than 100 feet underground. This was where Andrew Corp., a voice and data technologies provider, came in.

"Andrew's had extensive experience performing tunnel builds in other countries, such as Germany and Southeast Asia," said the company's project director Peter Street. "Andrew actually has a specific project group that deals with these types of applications. So we bring to bear a large force of practical application and we also do apply some theoretical technology."

Between the four stations, there's a main -- or head-end -- room where all the carriers place their equipment. Here, the carriers' cellular RF signal is sent to a modulating device where it's transformed into light and sent onto fiber optics that traverse from station to station. At each station, the light signal is taken off the fiber and remodulated into an RF signal, and distributed along the Radiax cable.

Built into the Radiax are many small "windows" spaced inches apart along the length of the cable. The cellular signal leaks out of these windows so wireless devices can receive it.

Building phase one took some time, however. A number of factors made the build a unique one.

"Every bracket, every connection, every box in the project was basically invented for the project because we had to meet certain standards that regular equipment doesn't meet," Dutto said. "So we actually designed and developed everything for this project in the last year and a half."

In addition, crews only had a few hours in which they could avoid being run down by trains. They also had to bring in special trains with flat cars just to access the tunnels and provide a place for the crews to work.

"Building in BART, you've only got 2.5 hours a night to do anything. On the weekends, it rolls out to maybe four or five hours," said Rae. "You've got to go in there now, you've got to put this cable up with brackets every 5 feet, you have to drill holes into the concrete. It has to be installed so it meets all the stringent requirements, the train doesn't hit it, and it doesn't fall down for 50 years."

Pipe Dreams
The idea, of course, is to one day bring wireless connectivity to all of BART. Like phase one, however, it will all happen in due time.

"The plan is to eventually connect all the underground so it's seamless, no matter where you are," said Rae. "This initial build between Civic Center and the Transbay Tube was a sizable bite for the carriers. They need to see some revenue coming in so they can feel comfortable, develop a business plan and spend more money."

Each carrier now has vested interest in seeing this project through to completion. Just as expanding above-ground capabilities helps each carrier maintain and grow its market share, building underground on BART does the same.

For Andrew Corp., the project is a chance to expand its portfolio of wireless undertakings.

"I know that Andrew is very excited to have the opportunity to proceed with working with BART on providing coverage to the Transbay Tube but also to the other outlying areas," said Street. "The Transbay Tube is just another opportunity for us."

As for Rae, the experience has been one of the highlights of his long career at BART.

"It's been a remarkable experience to aggregate all the carriers -- we've had them sitting around this table many times -- and they all agreed to do it," he said. "The crafting of agreements where they're all comfortable with it, that's hard to do."

But like any government project, the goal is to provide improved service to citizens. Rae has never lost perspective of that.

"To make it successful, people need the ability to use it while they're traveling or going from point to point without having to re-enter their ID or reinitialize," he said. "The people riding have the ability to transact business while they're going to work and going home. Think [about] what that means to people. You get to your office, boot up your computer and all these e-mails appear -- but if you get to work and a lot of them or all of them are done, it makes a big difference."
Chad Vander Veen

Chad Vander Veen is the former editor of FutureStructure.