TDMA ADDS CAPACITY
MOTOTRBO is based on time division multiple access (TDMA) technology that allows for two virtual channels within a single 12.5-kHz licensed repeater channel, which gives customers twice the calling capacity for the price of one license. Because there's only one “real” channel, a second call doesn't require a second repeater.
Though known as the “Sand Hills,” Cumberland County's fairly flat terrain doesn't impede radio reception. The department's real challenge is distance. When signal strength drops off with distance, digital error-correction technology delivers audio and digital content with virtually no loss over a far greater area.
Digital systems based on TDMA divide power-intensive transmissions into two independent time slots. That means each transmission only uses half the battery power of an analog system transmitting at the same wattage. Because transmitting is the most energy-intensive operation, digital two-way radios typically function 40% longer between recharges than analog radios.
Digital two-way radio systems based on TDMA can provide additional features beyond two-way voice by using the second time slot for a second call or to dispatch data, as well as enhanced call signaling and control for future enhancements such as emergency pre-emption.TEXT-MESSAGING WORK ORDERS
Text messaging enables text-format communication between radios and dispatch systems, radios and email-addressable devices, and radios and remote PC clients. Motorola's Cizek says more customers are using text messaging to exchange work tickets and work orders.
In Cumberland County, to accommodate text messaging and selective-call capability (the most used enhancements), all maintenance department supervisors and team chiefs received keypad models. The rest of the crew received non-keypad models.
Using a GPS modem and receiver integrated within the radios, the system provides dispatched-based location tracking of people and vehicles. The GPS software enables a computer to display maps and the location of each GPS-enabled radio.
Though the system is GPS-ready, the department hasn't used its asset tracking capability. “Once we had the radios fielded, we discovered that our tower required additional enhancements to use the GPS capability,” says Brunson, who adds that the feature will be engaged once the county's radio tower is further updated.
Meanwhile, a telemetry enhancement is available to allow technicians to command and control remote functions.
“For example, if a vehicle is powered on or a gate is left open, a signal can be sent to one or all radios,” says Cizek. “In a remote location example, the radios can activate a water pump miles away, and once activated, radios can receive a message that the pump is on.”
Motorola is working with more than 40 software application developers to add applications such as enhanced mapping. “Organizations will be able to leverage greater location data using the radio's USB interface,” says Cizek.