Many moving parts

Nov 1, 2007 12:00 PM, By Rick Burke & Jim Dombrouski

Perhaps the most misunderstood aspect of the 800 MHz reconfiguration process is the sheer operational complexity of public-safety radio networks across the country. Although these networks have evolved greatly over the last 10 years from a technology perspective, they typically are challenging to operate on a daily basis — let alone to fully retune base station infrastructure and mobile and portable radios.

Many of these networks serve not only multiple public-safety and public-service agencies within a jurisdiction, but they also support interoperable radio communications across the surrounding region. The requirement to maintain operational continuity inside and outside the jurisdiction is a major reconfiguration challenge.

Additionally, the reliability and operational quality of public-safety radio networks are critical communication requirements — literally a matter of life or death for all first responders. Direct access to the radio network and all radios throughout the rebanding program will be essential. The reconfiguration must consider myriad fundamental implementation requirements, including when the radio technicians and installers can have access to the radios for reprogramming, retuning and replacement of the subscribers' radio inventory. Public-safety radios are used on a daily basis by many agencies, and in the case of police cruisers are in operation around the clock. Consequently, ensuring uninterrupted operations during rebanding is extremely challenging.

Milwaukee County, Wis., certainly is one of the more complex 800 MHz radio networks to be reconfigured. The county uses a Motorola SmartNet II 800 MHz trunked simulcast radio system, which consists of nine base station sites with 14 analog frequencies each. First responders and public-service professionals in 17 of the 19 municipalities in the county use this system for both mission-critical and day-to-day communications. The network supports about 5400 active subscriber units and 69 user agencies. In addition, various regional, state and federal agencies also have equipment configured to use this system.

Milwaukee County currently has two levels of mutual aid to offer multiple-agency interoperable communications. There are four ICALL/ITAC repeaters distributed around the county, which also offers five talk groups configured on all subscriber units. These five talk groups, consisting of one hailing and four regular use groups, are used primarily for interagency events and offer an easy path to interoperability among regional agencies. In addition, the neighboring county of Waukesha has its subscriber units configured with these five talk groups.

The Milwaukee County Transit System (MCTS) is a primary user of the radio system. The MCTS currently operates an intelligent transportation system (ITS) and computer-aided dispatch (CAD) and automatic vehicle location (AVL) systems. These systems were designed around Motorola's Spectra two-way FM radio, a wideband, frequency-synthesized fixed-tuned mobile radio designed to operate in the 851-869 MHz band.

In addition to the ITS/CAD/AVL capability, the rebanding program affects two other in-vehicle components: the intelligent vehicle logic unit (IVLU) and the transit control head (TCH). The IVLU receives input from a global positioning system (GPS) antenna mounted on the roof of the bus to constantly monitor the bus's location and compare this information to previously downloaded route schedule information. The IVLU is programmed to automatically notify the dispatcher, via the radio system, of any anomalies should the driver be off route or off schedule. An additional feature tracks the bus's operating patterns, locating the vehicle in the event of an emergency.

“Milwaukee County, like many licensees throughout the country, has been diligent in its efforts to comply with the FCC's requirements,” said Steve Mokrohisky, senior program manager for the county's department of administrative services, information management services division.