Ups & Downs
Just after 2 p.m. on May 18, 2005, Long Beach, Calif., police officers were dispatched to check into the activities of three men who were spotted at the city’s water treatment facility. Upon arrival, they found the men attempting to attach a device to a water pump. As soon as the officers pulled up, the men panicked, jumped in their car and attempted to escape. The officers pursued and chased the men through the city’s streets.
By this time, a police helicopter hovered overhead, capturing the action on video and transmitting it to the city’s emergency communications operations center. While this was occurring, video footage also was being captured and transmitted by ground-based, in-vehicle systems and cameras mounted on the helmets of SWAT personnel.
Eventually, the suspects crashed their car, causing a fire. While police officers, backed by the city’s SWAT team, approached the suspects, the Long Beach Fire Department was dispatched to the car fire. Though ordinary as far as car fires go, the vehicle had crashed into a tanker truck, and there was concern that fuel inside the tanker could ignite if the car blaze wasn’t extinguished quickly. By the time the firefighters arrived, a second helicopter was on the scene, also capturing the activity on video and transmitting it to the operations center. Soon, the suspects were in custody, the fire was under control and the tanker truck was out of danger.
While that day seemed like so many others before it for the first responders dispatched to the scene and for their incident commanders in the city’s state-of-the art emergency communications center, it was anything but routine. The scenario described wasn’t real, but it was significant as it provided the first glimpse of whether airborne and ground-based 4.9 GHz systems could work together.
The tactical exercise took months to organize. In fact, it took five months just to get an experimental license from the FCC to put a 4.9 GHz camera system in a helicopter, according to event organizer Mike Doble, public-safety communications marketing manager for Proxim Wireless, a manufacturer of Wi-Fi and wireless broadband networks. The license was the second of its kind issued by the commission; the first was issued to the Democratic National Committee to provide airborne video surveillance for its 2004 national convention in Boston.
“They had a whole lot more clout than I did, but they only got theirs for one week — I got mine for six months,” Doble joked.
The FCC allocated the 4.9 GHz band for public-safety wireless broadband communications in February 2002. The order was significant because it theoretically cleared the path for advanced applications that would make first responders more effective and keep them safer, such as video surveillance of an incident or the exchange of mug shots and other large data files that typically would choke existing systems.
However, a few challenges immediately surfaced. One is that the band can be used by all public-safety agencies in an area, which creates the potential for interference issues if those agencies don’t cooperate to develop a workable band plan. This is particularly true in heavily populated areas such as Southern California, which accounts for more than 60% of the state’s residents. There also was considerable debate concerning the emissions mask to be used for 4.9 GHz equipment. Motorola proposed a tighter mask, citing interference concerns. Public safety wanted a looser mask to create a more open architecture that would encourage more vendors to get involved, which would in turn lower equipment costs. The FCC eventually sided with public safety and allowed the looser mask.
A third challenge was created when the FCC declined to establish spectrum dedicated specifically for airborne operations. “That would have been nice,” Doble said. “I know that several agencies — including the L.A. County Sheriff’s Department — requested additional spectrum during the comment period. But spectrum is at such a premium, we have to take what we can get and figure out a way to work together.”
Before that could be accomplished, public safety and 4.9 GHz technology vendors needed a better understanding of their challenges. To gain that knowledge, more than a dozen equipment vendors (see table) met in Long Beach to create the elaborate two-day event held in May and attended by about 200 government and public-safety officials. The event consisted of the tactical exercise (see figure) on the first day and interference tests conducted on the second day. Several public-safety agencies in the area provided support — most notably, the Long Beach police and fire departments, which provided facilities, equipment and personnel.
An 802.11g personal area network was deployed, 4.9 GHz radios were installed in police, fire and command vehicles, and a 2.4 GHz video system was used to facilitate helmet cameras used by SWAT team members. In addition, 4.9 GHz video systems were installed in police cars and in the helicopters. One of the airborne systems used a point-to-point steerable antenna, while the other used an omnidirectional antenna.
The inclusion of the two antenna types was by design. Omnidirectional antennas often are preferred by many public-safety agencies — despite the fact their signals are unfocused and thus weaker compared with directional antennas, which have greater range — because they are less expensive to deploy, according to Don Miller, wireless telecommunications frequency supervisor for the City of Long Beach. “Omnidirectional would be the one you’d want to use, if you could,” Miller said.
Omnidirectional antennas also are often more effective than directional antennas when trying to transmit data to personnel at an incident from a helicopter hovering overhead because of the downward direction of the signal, said Jesse Loera, communications engineer with the Los Angeles County Sheriff’s Department. A similar system using a directional antenna would need to first send the signal back to the command center, which is useful for keeping incident commanders informed about unfolding events but inefficient for sharing the feed with personnel at the scene.
“It would be hard for us to get the feed to them unless we had a directional antenna [at the command center] pointed right at them,” Loera said.
But airborne omnidirectional 4.9 GHz systems aren’t as effective when their signals collide with those of ground-based systems. While the 4.9 GHz directional airborne system didn’t interfere with ground-based 4.9 GHz systems during the demonstration, the omnidirectional system disabled the ground-based systems “one hundred percent of the time in close proximity,” said Doble, who defined close proximity as being “directly overhead to a couple of hundred feet away.” Even when the helicopter moved a quarter mile away from the ground-based systems, the omnidirectional airborne system “was still disabling, just not as much,” Doble said.
The result was expected, according to William De Camp, chairman of Region 6-700 MHz/4.9 GHz Planning Committee. “I wasn’t surprised,” he said. “The closer the proximity [of the omnidirectional antenna] to the ground system, the greater the impact.”
Another limitation of omnidirectional antennas in a 4.9 GHz airborne application is that they don’t allow frequency re-use, a big concern in mega-population centers such as the Los Angeles basin. “You’d be surprised at how many cities have helicopters, and we don’t have enough frequencies to have 10 helicopters flying at once” if each uses omnidirectional antennas, said Miller, who added he was neither surprised nor disappointed by the result.
“This was a fact-finding mission, not just a demo,” he said. “We wanted to determine whether some of the things that in the lab we thought would work would also work in the field. The goal was to stress the system. If you don’t break it, you didn’t stress it enough.”
Confirming their suspicions was the easy part. The more difficult task for public safety is determining how to ensure that 4.9 GHz airborne systems won’t interfere with ground-based systems regardless of the type of antenna used. It’s an important goal because public safety currently uses broadcast spectrum to transmit video. Because broadcasters are the licensees, they have the right to tell public safety to vacate the band, Doble said.
“I’ve heard stories where public safety has a helicopter in the air covering an event, and then a news helicopter shows up. The broadcaster then tells the public-safety agency to turn their system down because they’re interfering with the [news chopper],” he said. “The issue is how to get public safety off the airwaves used by broadcasters.”
The problem would go away overnight if the FCC reconsidered and carved out a swath that could be dedicated to airborne systems. However, everyone interviewed for this story conceded that’s not going to happen, so the task now is to determine how best to use the 50 MHz in the 4.9 GHz band that the FCC gave public safety.
The approach that seems to be gaining momentum, at least in California, calls for the 4.9 GHz airwaves to be divided into 10 channels of 5 MHz. Airborne operations would be confined to the lowest one or two channels in the band. Another option is to divide the band into five 10 MHz-wide channels; similarly, airborne systems would be confined to the lowest channel. “That would reduce co-channel interference,” De Camp said.
The problem is that such a solution would require a reduction in the width of the video stream transmitted by an airborne system — or suitable compression — so it could be transmitted through the narrower pipe without jitter or latency, which are taboo in the world of mission-critical communications. However, Doble said at least one vendor that participated in the Long Beach event — Massachusetts-headquartered Microwave Radio Communications — already is developing such technology and predicted others will follow.
“When that takes hold, others will embrace it,” Doble said. “We’ll see it get down to the necessary width.”
But that only matters if spectral-usage plans are followed, said De Camp, who said recommendations of the various planning committees across the country are merely advisory.
“We wanted the FCC to mandate compliance with the regional plans to prevent chaos,” he said. “But they didn’t. So we can urge compliance, but we can’t force it.”
Long Beach vendor participants
Alvarion
Broadband Network Services
CelPlan Technologies
Consolidated Spectrum Services
Global Microwave Systems
IBM
InsightVideoNet
Microwave Radio Communications
Motorola
Padcom
Proxim Wireless Networks
Syracuse Research Corp.
Western Technical Services
Source: Public Safety 4.9 GHz Resource Center
Have we got a deal for you
In an era when many communities find themselves cash-strapped, public-safety agencies might be wondering where they’re going to find the money to deploy 4.9 GHz communications systems. Two companies eager to cash in on first responders’ interest in advanced broadband wireless systems believe they have a solution that will make it easier and cheaper than public safety thinks.
Information Network Services and Broadband Network Systems have created a model they say replicates the approach used by commercial wireline and wireless voice and data service providers. Rather than purchasing and deploying equipment and then operating and maintaining the system, all public safety would have to do to get into the 4.9 GHz game would be to lease broadband networked connectivity from the joint venture formed by INS and BNS.
“We’re taking all the risk for the venture. We’re going to get the sites, and we’re going to build and manage the system. If it doesn’t work, the subscriber has no risk,” said Michael Cutler, principal partner at BNS.
The companies are looking for long-term commitments from public-safety agencies ranging from three to five years. The longer the commitment, the more public safety can expect from the relationship, Cutler said. “When you go to a cellular company, they’ll give you the super-duper phone if you give them a four-year commitment. We’ll do the same thing,” he said.
William Guerra, director of INS’s commercial business division, said public-safety agencies could expect the same level of commitment in return. “We’re not interested in a one-and-done proposition. We’re not looking to put a bunch of boxes on light poles and then walk away,” he said.
But getting public safety to buy into a leasing premise for something as critical as a broadband wireless network probably will be a tough sell. Much would depend on the service provider’s business model, said Harlin McEwen, chairman of the International Association of Chiefs of Police communications and technology committee. “How can they make money and not charge a lot to public safety?” he asked.
Larger agencies probably would have little interest because they want to control their destiny and avoid being at the mercy of the service provider, according to Robert Uribe, wireless telecommunications frequency coordinator for the City of Long Beach, Calif., which has a population of 461,000-plus, making it the fifth-largest municipality in the state. “When you have a 24-hour staff, you can react fast and have an outage fixed within a couple of hours, he said. “When you contract for services, you’re on a priority list with every other agency.”
But the idea might be appealing to smaller agencies that typically wouldn’t have the resources to deploy a 4.9 GHz system, said Don Miller, Long Beach’s wireless telecommunications frequency supervisor. “We currently lease out a portion of our infrastructure to other agencies,” he said. “So we’ve been on both sides.”
— Glenn Bischoff
