Battle of the Bandwidths

4.9 GHz is a clean, clutter-free spectrum that can support mission-critical public safety applications.

Terrorists are spotted building a weapon of mass destruction in an abandoned airport hangar. SWAT arrives on the scene. Utilizing a 4.9-gigahertz (GHz) broadband WiFi network, video is streamed to the commander from cameras deployed around the incident. From the command post, using a 360-degree view of the scene, he develops a strategy to enter the hangar, diffuse the weapon and nab the terrorists. One of the fleeing suspects commandeers a fuel truck and rams it into an airliner, setting it on fire and injuring the passengers and crew. Police, fire and EMS teams respond, coordinating their activities using interoperable broadband WiFi networks and applications.

This was the scenario at a Department of Homeland Security (DHS) Training and Evaluation Exercise in April 2006 at the Long Beach (California) Airport. Twenty-eight police, fire, EMS, military and government agencies responded to the hypothetical threat, which demonstrated the need for advanced, WiFi-based, interoperable communications systems.

September 11, 2001, Hurricane Katrina and the bombings in London, England, demonstrated what happens when communications systems fail - coordination among responding agencies becomes difficult or impossible. When radios fail, first responders reach for their cell phones. When cell phones fail, first responders' lives are placed at risk, and protecting the public becomes a daunting task.

Dealing with terrorist threats, gangs or natural disasters - as well as day-to-day law enforcement activities - demands new communications solutions and is fueling the development of broadband wireless networks. These networks enable law enforcement to better protect the public and themselves.

Broadband communication dramatically improves the efficiency of public safety organizations - and can result in actual cost savings. Long Beach highlighted how incident commanders can utilize video from multiple perspectives to gain a 360-degree view of an incident, from one location. Resources can be deployed using mapping and white boarding applications to provide clear, concise instructions. Video also can provide virtual back-up to officers on patrol - providing the watch commander with a view of a traffic stop or police activity in the field.

What is a broadband WiFi network?
WiFi networks connect a device (or node) to the network (represented by an access point) using radios. Some WiFi networks also enable client-to-client connectivity in one hop. Broadband wireless networks support higher bandwidth applications, beyond voice and simple data capabilities provided by standard radios or cell phones. With broadband, commanders can share large multimedia files, such as video and GPS mapping in addition to voice.

Broadband WiFi networks come in many forms, but share common characteristics:

  • They're based on Internet Protocol technology for digital (versus analog) communication;
  • Most require an access point to provide Internet connectivity and backhaul;
  • Most utilize meshing technology, creating a self-forming multi-faceted network; and
  • Most utilize unlicensed radio frequency spectrum to carry information.

It's this last point that presents a challenge for law enforcement. Spectrum refers to the frequency and bandwidth allocated to various forms of communications - including television, AM radio, microwave, radar and WiFi. In the United States, IEEE 802.11-standard based networks (commonly called WiFi) operate in the 2.4-GHz and 5.0-GHz bands. [Hereafter references to the 2.4-, 5.0- and 4.9-GHz bands will not include the "GHz."]

The spectrum differences
The 2.4 spectrum is the world's default frequency for WiFi communications. It's used by a variety of devices for a variety of purposes. When connecting to a "hotspot" at Starbucks, talking on a cordless phone, turning on the microwave oven or connecting to the office WiFi network, you're likely using 2.4. The advantage of 2.4 is that it's free, unlicensed and unmanaged spectrum... anyone can use it. The disadvantage is that it's free, unlicensed and unmanaged, and just about everyone uses it. Use a laptop to search for WiFi networks, and depending on location, you may "discover" 10 or 20 WiFi networks, all generating "noise" that clutters the spectrum.

As a result, 2.4 is a very crowded spectrum and, while it's fine for sending e-mail from Starbucks, it doesn't work well for mission- critical public safety applications. In a critical situation when an officer tries to connect to a 2.4 network, the result may be a complete failure due to range, coverage, interference and bandwidth limitations.

The 5.0 spectrum isn't much different. Like 2.4, it's free, unlicensed and unmanaged spectrum. While it's not presently as widely used as 2.4, it will soon face the same challenges.

Most 2.4 and 5.0 networks can provide up to 54 megabits-per-second (Mbps) maximum throughput.

The best choice for law enforcement
Fortunately, in America there is a better solution. The Federal Communications Commission (FCC) realized that 2.4 and 5.0 don't provide a viable option for public safety. In 2003, the FCC took action to solve this problem by dedicating 50 MHz of bandwidth in the 4.9 slice of the spectrum pie to public safety.

4.9 is licensed, controlled spectrum that is available exclusively for public safety use. As a result, it is clean, clutter-free spectrum that can support mission-critical public safety applications. In addition, 4.9, which also can provide up to 54 Mbps throughput, can be used at a higher power level, further improving its range and capabilities.

PacketHop, a provider of mobile-mesh broadband WiFi solutions supporting the 4.9 spectrum, has done range and performance tests that demonstrate the superior capabilities of 4.9.

In theory, 2.4 spectrum has a range in the thousands of feet between devices. However, in practice, the useful range of commercial 2.4 or 5.0 networks is much less - typically between only 50 and 500 feet - due to the interference resulting from the widespread use and limits on transmission power.

By comparison, PacketHop, located in Redwood City, California, has tested 4.9 networks with high-bandwidth applications to work beyond 3,400 feet - that's more than half a mile or 10 typical city blocks. For responding to a catastrophe, or just for everyday use, this 6x or better performance improvement could make the difference in successfully resolving an incident.

Municipal WiFi networks
Many cities are deploying or planning a WiFi network, often to provide the public with free or low-cost access to broadband Internet to bridge the digital divide. Improving the delivery of public services and public safety are frequently secondary motivations - when taken into account at all.

Most municipal WiFi networks are composed of a grid of access points (often mounted on light poles) to provide coverage. These access points are typically located within 500 to 1,000 feet of one another to create many interlinked WiFi hotspots. Most municipal WiFi networks use 2.4, and there may be dozens or even hundreds of people using a particular access point, creating a lot of WiFi traffic. This limits the bandwidth and connectivity available, making it unsuitable for law enforcement.

Some municipalities are planning ahead and incorporating 4.9 into their WiFi network plans so that public safety has the communications capabilities it needs. However, the onus may be on law enforcement to take the lead and address the issue with government officials - typically the IT director - to support 4.9.

How many agencies are using 4.9?
Interest in using 4.9 for public safety applications is growing. In the second half of 2006, more than 400 licenses were filed to use 4.9. However, based on a recent PacketHop survey of public safety/law enforcement done in conjunction with, only a small percentage of the eligible public safety agencies have applied for a license. Of 418 people that participated in the survey:

  • Only 7.7 percent currently have a 4.9 license;
  • 6.7 percent plan to apply for a license within the next year; and
  • 5.7 percent plan to apply for a license a year or more from now.

If 4.9 is the "promised land" for public safety communications, why aren't more agencies using it? Again, referencing the PacketHop survey results:

  • 36.5 percent weren't even aware that there was a 4.9 public safety spectrum;
  • 29.6 percent don't think they can afford a 4.9 solution; and
  • 18.2 percent believe their current narrow-band spectrum is adequate for their needs.

While these results are based on a random survey with a reasonable margin for error, they do illustrate a few points.

First, the FCC isn't in the business of promoting 4.9. As news of successful 4.9 deployments spreads, awareness should increase.

The cost to deploy a 4.9 network doesn't have to be prohibitive. In fact, cost can be quite reasonable and there are often grants available. 4.9 radio cards (for PCs) and antennas are available today from multiple vendors and more will hit the market this year, further driving down equipment prices. Because 2.4 radios are bundling into most laptops and some other mobile devices today, people don't associate a cost with using 2.4. But making the investment in 4.9 shouldn't be considered a frill as it may make the difference when a critical incident occurs.

For those that believe 2.4 or current radio systems are adequate to meet their needs, numerous field tests have shown that questions remain regarding interoperability and mission-critical communications requirements. Relying on proprietary land-mobile radios limits communications between agencies in mutual-aid situations to voice and low-speed data, and provides no support for high-bandwidth applications - if the radios interoperate at all. Before relying on existing systems or 2.4-based solutions, departments should field test them to ensure they meet performance and capability needs.

Securing a license
Obtaining a 4.9 license is relatively easy and no cost is involved in filing an application. Go to and use forms 601 and Schedule I. These forms are similar to forms filed for police radio use, and getting a license typically takes less than two weeks.

Next, find a solution vendor that can assess your specific requirements and propose a system tailored to your needs, based on the community, existing communications infrastructure and budget. This vendor should also determine if a fixed or fixed/mobile solution is best. (See "Fixed and mobile networks" on Page 99.) A trial deployment can help in planning for a full-scale roll out by identifying coverage and mobility requirements. Some police forces find it useful to assign an officer to coordinate the project and evangelize its use.

It's also a good idea to contact neighboring agencies to assess their plans for 4.9 as interoperability between agencies can be a key benefit when responding to large-scale incidents.

Measuring the benefits
Beyond the benefits of improving public and officer safety, having access to visual information, and creating interoperable communications across agencies, there are quantifiable cost-saving benefits. At a recent event, the Lakewood (New Jersey) Police Department equipped its patrol cars with video cameras and streamed video across the network to headquarters, providing enhanced security and eliminating the need to send backup for routine operations. The result: thousands of dollars in tangible cost savings by reducing staffing and overtime pay.

With dedicated spectrum, broadband communications can dramatically improve the efficiency and interoperability of public safety communications.