A gem of a system upgrade
On March 9, 2008, a heavily armed 27-year-old man allegedly robbed a jewelry store in the Mission Viejo Mall, smashing jewelry cases and brandishing weapons. Orange County (Calif.) Sheriff’s Department deputies responded to the call and within minutes were pursuing the perpetrator. The chase culminated in a gun battle and a shooting of the robber by officers. Fortunately no officers, mall employees or visitors were hurt.
The response was aided greatly by a distributed antenna system (DAS), supported by bidirectional amplifiers and a backup battery system, which enabled officers using the county’s 800 MHz radio system to receive signals well within the mall — something that previously had been a major problem.
The 800 MHz Countywide Coordinated Communications System (CCCS) is used by all local public-safety agencies (law enforcement officers, firefighters, paramedics and lifeguards) and by government agencies on a 24-hour basis. The system is managed by the Sheriff-Coroner Communications Division (SCCD) — under the direction of Robert Stoffel — which oversees system design and engineering and frequency management, as well as the installation, maintenance, and programming of communications and electronic equipment (including microwave equipment; 911 dispatch equipment; mobile and portable radios; and surveillance, alarm, sound, video and control systems).
The SCCD consists of 91 personnel organized in three areas that specialize in specific technical applications, including the Technical Services Unit, the Engineering Section and the Emergency Communications Section. Each group maintains a staff of engineers, technicians and support staff to provide a high level of technical expertise to various public-safety functions, including city and county law enforcement, emergency services, lifeguard operations, park rangers, public-works agencies, courts, jails and probation facilities.
Within the Engineering Section is the Radio and Microwave Unit (RMU), which maintains the CCCS backbone that consists of 21 remote sites, six trunked simulcast cells and several intellirepeaters that provide 15 dB or greater coverage countywide. The highly fault-tolerant system initially cost $84 million to field in 1999.
The CCCS is Orange County’s state-of-the-art, analog/digital trunked, public-safety interoperable radio communications system. More than 19,000 subscribers use the system, resulting in approximately 20 million transmissions per year.
The county’s Dispatch Systems Unit (DSU) provides 24-hour service for more than 45 emergency and public-safety dispatch centers and supports Emergency Operations Center activations. The DSU maintains and repairs 911, law enforcement, fire and hospital consoles; city primary dispatch systems; fire mobile data systems; public-works and marine-safety dispatch centers; 900 MHz paging encoders and transmitters; and paramedic base stations.
Additionally, the DSU manages the performance of more than 45 in-building coverage systems. Although the countywide 800 MHz system is very robust and most areas and many buildings are naturally covered, some facilities have building losses or underground structures that severely diminish, or eliminate, radio wave propagation.
Such was the case for the Mission Viejo Mall, which was built in a very low spot and is shielded from the remote sites that provide public-safety radio coverage for the mall and South Orange County.
Responding to requests to assist with coverage in the mall, Orange County Sheriff Communications worked with the mall owner, Simon Co., and its radio site lease subcontractor, American Towers Corp., for more than two years to engineer an innovative in-building solution that improved coverage to 95%, both in South Orange County (previously 50%) and countywide (previously 70%) cells.
This was good news for the Orange County Sheriff’s Department (OCSD) and the Orange County Fire Authority, which have had to deal with poor coverage when responding to calls inside the mall. Now, almost all public areas inside the mall receive and transmit calls with relative ease.
The mall’s in-building coverage system was designed in a public/private partnership. The bidirectional amplifier and backup battery system was purchased from TX RX Systems with Department of Homeland Security funding. The amplifier was installed by the sheriff department’s Communications Dispatch Systems Unit and interfaced to American Towers’ privately owned Andrew/BriteCell fiber optic distributed antenna system (DAS) — a system of RF-to-fiber conversion amplifiers, switches, coax and internal disguised antennas.
Ray Grimes, communications engineering manager for the OCSD, negotiated a no-cost lease for the county, which shares the DAS with Sprint Nextel and Cingular. The DSU used extensive engineering and installation strategies based on empirical data and sound radio frequency engineering principles, resulting in the county and Sprint Nextel co-channel users existing on the same DAS with optimum signal strength for all users. Additionally, the in-building system greatly enhanced coverage in the shops at Mission Viejo with virtually no cost to the mall, the county or the CCCS partners.
During the jewelry robbery and in the aftermath of the shooting, an enormous number of law enforcement officers, paramedics, crime scene investigators and coroner personnel were dispatched to the mall. After the incident, Sgt. Douglas Bertoglio praised the recent installation of the booster antennas.
“We on the outside could clearly hear those on the inside and vice versa. A big part of the credit for this must go to the recent installation of the booster antennas,” Bertoglio said. “Without them, personnel who were inside of the mall would have had to tie up one hand holding the radio away from their body in order to hear incoming transmissions.”
Their only other choice, he added, would have been to keep the handheld radio on their belt and settle for spotty reception.
“The improved reception made for an all around smoother and safer operation. The antenna installation was money well spent.”
Howard W. Newton III, P.E., is the supervisor of the Orange County Sheriff’s Department Dispatch System Unit.
