Cochise is the fourth largest county in Arizona, spanning 6200 sq miles and including a land border with Mexico. The Border Alliance Group (BAG) is among the US Governmental agencies that need a reliable radio communications network to prevent international drug trafficking between the USA and Mexico
Cochise had two primary goals to achieve when upgrading its existing analog simulcast system to a digital network: to provide wide area saturated coverage and to prevent conversations being intercepted.
The County features a number of hills and adjacent basins meaning received signal quality can be poor and coverage limited. Coverage and clarity of radios are extremely important for the emergency services as many calls can be highly critical. In particular, BAG is a multi-agency task force responsible for seeking out and monitoring narcotics smuggling corridors. These passages often are in remote or less uninhabited areas.
The group has become vulnerable to people using scanners to intercept their radio conversations or have previously had to use radios with analog encryption, meaning poorer coverage over longer distances in comparison to digital radios. Finally, a number of organizations use various competitor portables and mobiles on the analog network. Cochise wanted to ensure these products would work on any future solution, avoiding the financial burden of upgrading the entire fleet of subscriber units immediately.
When Cochise moved to a narrowband system in 2002, Durham Communications recommended migrating from a competitor's single-site system to a TaitNet 5-site, 5-channel QS2 simulcast system.
For the digital upgrade Cochise turned again to Tait partner Durham Communications, who suggested a three-site Tait APCO P25 VHF Simulcast digital solution. Each of the three sites consisted of a TB9100, Cisco network switch and router, while the Sheriff's Dispatch Center contained a TB9100 gateway. Tait digital simulcast delivers spectral efficiency by reusing the limited frequency available in Cochise. This enables the County to avoid spending money on purchasing multiple frequencies.
By utilizing the same frequency on different sites, coverage is overlapped resulting in improved saturation throughout the County. The radio users who gained the initial benefits of the simulcast system were those upgrading from analog portables and mobiles to Tait P25 subscriber units, which feature superior voice clarity. Importantly, these radios were equipped with DES encryption to prevent messages from being intercepted from those outside the network.
Within hours of the solution being installed, the BAG was using Tait radios on the network to execute a search warrant. The encrypted digital radios mean the Group can use the radios for operations without being concerned they may be intercepted.
BAG can switch between simplex and repeater channels, but also can use the analog channel for ease of inter-agency collaboration. Since installation, several other organizations are using Tait subscriber units on the system.
Overall, the Tait P25 simulcast network has improved coverage by 40 per cent in the southern area of Cochise County.
Other case studies
Tait provided a P25 digital radio solution for the City of San Luis Obispo for use by police, fire and utility departments achieving 98.5% city-wideRead client story
A Sheriff’s radio must have good coverage, deliver clear and reliable audio as well as appropriate call services and privacy settings. This paper describes P25 communications technology and its relevance for Sheriff’s Agencies. P25 is also compared to other open digital radio standards—DMR and dPMR.