AFC - Project 39 - History

Note for updated information on this issue, go to www.800mhz.org

APCO Project 39 - History

Interference to 800 MHz

In April 2000, APCO attended a meeting hosted by the FCC in Washington, D.C. regarding the public safety 800 MHz system interference issue. Along with APCO, Nextel and Motorola attended. Nextel had been identified specifically as a party involved in many of the interference issues. Motorola attended as manufacturer of the equipment Nextel uses.

This meeting was intended to bring the representatives of the affected parties together in an attempt to identify the scope of the problem. Each party attending provided an overview of the problem from its perspective. The FCC requested the attendees create a task force to further address this issue. The FCC specifically asked the task force to operate independently of the FCC but did assign an FCC liaison to monitor the progress. The mission of the task force was to fully identify the scope of the problem, the actual parties and mechanisms behind the interference, and ultimately provide a workable solution to dealing with the interference.

More than one specific technical mechanism was identified as the cause behind the interference from preliminary data provided during the meeting. However, virtually all modes of interference could be tracked to the different design modes of commercial systems and public safety systems. Briefly, public safety systems are designed to maximize coverage from a centrally located base station using the maximum technical capabilities of equipment. This is defined as "noise limited" design. Mobiles operate close to their practical design threshold; in this case, close to their maximum receive sensitivity in the extremes of their coverage area. On the other hand, commercial systems are designed to hand-off mobiles well before they approach a threshold signal level. And system designers purposefully place base station transmitters in relative close proximity of strong signal overlap to ensure continuous coverage for a moving mobile. This is called "interference limited" inasmuch as the mobile travels until it encounters a stronger signal as the mobile enters a stronger signal of an adjoining site. This also allows for the installation of many small transmitter sites or cells. Economically, the commercial provider can increase the frequency reuse providing greatly increased capacity for areas of high access demand by the public.

A typical public safety base is located strategically to maximize its range but may not be near an area that is critical for mobile contact. Usually such areas receive a signal level well within normally acceptable design criteria. If a commercial provider places a station in these areas of low, but usable signal, very often the addition of the commercial transmitter to the overall radio frequency environment is just enough to mask the intended public safety signal.

The industry trend for commercial radio providers is to increase capacity and coverage by placing more and more transmitters in areas that coincide with high concentrations of general population. Quite often these are the very same locations that are becoming critical for public safety to provide reliable coverage. The conflict is evident and the trend will not alter in the foreseeable future.

The problem is not limited to Nextel operations. Many other commercial wireless operations can also interfere in this same general manner. This includes other cell phone operations as well as dispatch-type operations. It happens that Nextel's choice of technology is a digital modulation technique that can be more harmful than older analog technologies, but even older technologies are not immune from causing these problems.

Later, APCO, represented by Glen Nash, first vice president elect; and Ron Haraseth , director of AFC, visited with CTIA (Commercial Telecommunications Industry Association) representatives in Washington , D.C. , to further discuss the direction of efforts. Concurrently, Motorola and APCO have developed information-gathering tools in the form surveys to better identify the agencies receiving interference and determine the exact interference mechanism for each.

APCO created an online reporting form located on the APCO Web site. Response was good, but we are sure many more affected agencies have not reported. Many agencies may be experiencing intermittent interference from commercial sources and may be unaware of the cause. APCO will be compiling this information internally to use in an information campaign that will assist agencies experiencing problems in determining how to identify this type of interference. Motorola has also created an Excel spreadsheet that can be used to quantify the interference in greater detail, which will help pinpoint the exact cause and potential solutions. APCO has made this spreadsheet available on its Web site as well.

Identifying the scope and severity of the problem is only the first step in our efforts. This does not prevent nor assuage the problem. Means of reporting the problem must follow once the symptoms and mechanism are identified. Progressing further requires a system to collect, monitor and track each specific instance of interference. At some point in this process, the parties involved in the interference will be brought together, and both will be required to report progress on solutions.

Frankly, there is little chance of a permanent long-term solution to this type of interference. Even when a "fix" is applied, it may only mean the problem moved to some other site (moving a specific commercial frequency to another site). Also, the commercial mobile radio industry is growing and continually adding new locations to their networks. This includes changing frequency mixes at other sites creating a dynamic problem. The information and contacts made through a monitoring process may assist the commercial providers in designing systems that will not interfere as often. It will most certainly assist public safety agencies to quickly identify the problem and obtain faster resolutions. If we cannot entirely eliminate the problem, at least we should be able to help provide a quicker resolution when interference is encountered.

The task force formed in April of 2000 worked for several months with the resulting document the "Best Practices Guide".  This document was compiled by a working group of subject matter experts from the following organizations: the Association of Public-Safety Communications Officials-International, Inc., the Cellular Telecommunications & Internet Association, Motorola, Inc., Nextel Communications, Inc., and the Public Safety Wireless Network.

The "Best Practices Guide" was only a start.  The Guide, in itself, does not provide any long-term relief, but instead provides enough information to help system owners to identify potential problems with some possible avenues of temporary relief.  The Guide also begins the path towards avoiding problems by addressing basic system design.  

In order to arrange for a long-term solution APCO President Lyle Gallagher created Project 39 and appointed RoxAnn Brown of the Oregon chapter to chair the committee. Brown convened a steering committee and a technical committee at the committee's initial meeting, which included commercial industry members.  

The mission is to provide multiple, reality-based and (where possible) tested short-, mid- and long-term solutions for the 800 MHz interference issues involving wireless/cellular providers and public safety, solutions that can be applied to eliminate life-safety communications interference within the United States.  

The committee's six-month goal is to have all current public safety 800 MHz interference issues catalogued, including how the problem manifests, who the contact parties are for the affected public safety agencies, what is providing the interference, how long it has been occurring and what, if anything, has been or is being done to resolve it.  

Within 12 months, the committee's goal is to have all potential short-term interference solutions identified, tested and applied, where applicable.  

The committee's 18-month goal is to have all mid- and long-term solutions identified and, where possible, tested. These solutions should be applied to at least two identified organizations with interference issues, to make sure they are doable.  

The projects Steering Committee includes several key anchor public safety organizations, including APCO, the International Association of Chiefs of Police (IACP), the International Association of Fire Chiefs (IAFC), the Public Safety Wireless Network (PSWN), the National Association of Counties, the National Governors Association and the National League of Cities.  

Industry participants included both commercial system operators and equipment manufacturers. Industry partners include M/A-Comm, EF Johnson, Motorola, Nextel, the Personal Communications Industry Association (PCIA), the Cellular Telecommunications Industry Association (CTIA), and AT&T Wireless. Other commercial system operators have been invited to participate.  

The Project 39 team will continue to work as a partnership with industry and the FCC until 800 MHz interference to Public Safety is no longer a problem.