By Stuart Overby, Senior Director, Global Spectrum Strategy, Motorola, Inc.; and Member of the IACP Communications and Technology Committee
ublic safety agencies in the law enforcement arena know the value of reliable communications. Agencies often view radios to be as essential as firearms in the mission to protect their officers and the public they serve. Traditionally, such communications have been focused on voice operations. New frequencies in the radio spectrum and new technologies offer the law enforcement community additional tools that supplement voice operations with data, imaging, and video. Combined, all of these tools enhance communications to help prevent and fight criminal and terrorist activities, which have become much more sophisticated over the last 10 years. The IACP has been a key influence in the initiatives for new public safety frequencies in the radio spectrum, the foundation for the development of these new communications tools. This article focuses on the new applications, radio spectrum allocations, and technology for law enforcement agencies.
New Communications Applications
As criminals have become more sophisticated and terrorism more prevalent, law enforcement agencies have come to rely on new and innovative databases and associated software programs to help prevent or respond to crime and terrorist events. The National Crime Information Center (NCIC) database and programs that contain information on wanted and missing persons and stolen property along with other valuable information are a few examples. However, for many agencies the availability of this information has been “station bound” and not available in the field, where immediate access could provide much greater benefit. But that has begun to change.
Although some databases can already be accessed over current public safety bands, essential voice operations increasingly fill that range of the radio spectrum, particularly in and around major urban areas. New radio spectrum bands and technologies are supplementing existing mission-critical voice communications with immediate field access to the availability of data, images, and video. In addition to accessing information like the NCIC and hazardous-materials databases, officers can upload incident reports from their patrol cars or handheld devices rather than driving back to the station to do so.
Video operations also are beginning to be used in the field to help monitor criminal activity and document evidence. For example, the Los Angeles Police Department (LAPD), in partnership with the U.S. Department of Justice and the Department of Housing and Urban Development, spearheaded deployment of a municipal wireless network and video surveillance system in the Jordan Downs public housing complex in March 2007. An intelligence officer can monitor the video feeds from the 10 deployed cameras and can instantly send video to the closest police cruiser or to multiple responders if required. Officers on the street can use on-board laptops to access video from cameras in the network and can zoom in and out on suspected criminal activity, increasing safety and effectiveness.
Chiefs, police on the beat, special weapons and tactics (SWAT) teams, and investigators can all take advantage of data and video information that will become increasingly available in the field. Routine deployment of these new tools would not be possible without the availability of new spectrum allocations for public safety, an area in which the IACP has taken leadership.
Additional Spectrum and Technology Availability
Two significant public safety spectrum allocations in the United States are primary enablers of these new communications solutions. These allocations are the 700-megahertz (MHz) band and the 4.9-gigahertz (GHz) band. Both of these spectrum allocations provide capacity for high-speed data and video transmissions previously unavailable in the existing public safety voice spectrum.
Because of its location lower in the spectrum, the 700-MHz band is appropriate to support wide-area mobile communications, that is, throughout a jurisdiction, state, or region, and potentially nationwide, all requiring multiple transmitter sites. The mobile coverage radius at 700 MHz for a typical public safety voice system will extend 12 to 18 miles from each transmitter site, depending on terrain, power levels, and the type of environment. Mobile coverage per site will be similar for wideband data systems at rates of approximately 100 kilobits per second (kbps). Broadband systems with faster data rates of 500 kbps or more, which use off-the-shelf broadband portable devices, would typically result in a coverage radius of approximately three to five miles per site.
The 700-MHz spectrum range was initially allocated to public safety in 1997 as a result of congressional action influenced by the IACP, other members of public safety leadership, and the telecommunications industry. However, this spectrum must be cleared of television to be usable everywhere in the United States. Current law establishes a certain deadline of February 2009 for the spectrum to be cleared. More information on the 700-MHz range is provided in the article “A Nationwide Public Safety Wireless Broadband Network.”
The 4.9-GHz band is much higher in the spectrum, where coverage radius per site is less but data transmission rates are significantly greater. A 4.9-GHz system would generally require 20 to 30 sites to cover a square mile. This makes the 4.9-GHz range ideal for providing public safety wireless data and video coverage of an incident scene, sporting event, or other localized area on a more permanent basis, such as for the Jordan Downs system mentioned above.
The 4.9-GHz band spectrum availability and rules were finalized in November 2004. Over 1,100 agencies have now obtained licenses for the band. Innovative broadband equipment that provides a very broad wireless communications “pipe” of 5 to 20 megabytes per second (MBps) per channel is available from multiple manufacturers. Some companies offer “mesh” equipment, which also allows multiple vehicles to create a self-forming ad hoc network at an incident scene. For example, police, fire, and emergency medical personnel could share information as required at the scene of a disaster or major traffic incident.
Departments that wish to take advantage of these new spectrum bands should first consider how they anticipate using the new tools this spectrum supports now and for the foreseeable future. This includes some assessment of whether the need is localized or wide-area, whether the coverage required is on the street or also in buildings, the ratio of video transmission to other types of data, and the expected level of use. With any system, of course, reliability over the specified service area is a critical factor. Current public safety voice systems are normally specified at 95 percent or greater reliability. For data systems, the degree of reliability should also be specified at the promised data speed because data rates, coverage, and reliability are all interdependent and based on system design.
Experience shows that public safety entities often find beneficial ways to use new communications tools that were not originally envisioned. Therefore, it is wise to build in some room for growth in capacity when assessing these needs. If a jurisdiction is likely to expand, it is also appropriate to consider possible coverage expansions as well. Once an agency has assessed its requirements, it should rank the various available options against these requirements. Fortunately, new spectrum and technology developments provide agencies with a range of options to consider.■
|Stuart Overby has 33 years of experience in spectrum management and communications. In addition to his membership on the IACP Communications and Technology Committee, he currently serves as vice chair, Spectrum Management Committee of the National Public Safety Telecommunications Council (NPSTC); chair, 700 MHz Advocacy Working Group, NPSTC; chair, In-Building Communications Working Group, NPSTC; chair, Public Safety Working Group, In-Building Wireless Alliance (IBWA); and vice chair, Wireless Communications Association (WCA) 700 MHz Committee. Prior to joining Motorola, he was with the U.S. Federal Communications Commission for 12 years. |