Longer battery life and greater power efficiency

One of the biggest challenges with mobile devices has always been battery life. In the past, there have been limited options for increasing the talk time on a single battery charge. Two-slot TDMA, however, offers a good way forward. Since an individual call uses only one of the two timeslots, it requires only half of the transmitter’s capacity. The transmitter is idle half of the time — that is, whenever it’s the unused timeslot’s “turn”. For example, in a typical duty cycle of 5 percent transmit, 5 percent receive, and 90 percent idle, the transmit time accounts for a high proportion of the drain on the radio’s battery.

By cutting the effective transmit time in half, two-slot TDMA can enable up to 40 percent improvement in talk time in comparison with analogue radios. (One manufacturer’s published product literature gives a talk time of 9 hours operation for analogue mode but 13 hours for digital mode on the same radio). With overall battery consumption per call dramatically reduced longer usage time in the field between recharges is enabled. DMR digital devices can also include sleep and power-management technologies that increase battery life even further. Even though many factors affect power consumption in an individual device, comparing published battery life figures for widely marketed DMR and FDMA digital radios shows the benefit of the TDMA approach over FDMA. For each hour of usage the TDMA radios show between 19% and 34% less battery capacity is required than for the FDMA models.

Apart from the environmental reasons for not wasting energy, choosing a technology with lower energy use gives more flexibility in the future because as communications needs grow for users (for example greater data requirements) more battery capacity is needed and it is better to bet on the technology which it is inherently more efficient and therefore has more room to play with. As discussed above, DMR infrastructure is also simpler than that required for FDMA systems. This means that the energy requirements to run a site are lower for TDMA than for FDMA These power efficient features give DMR users a leaner and greener radio network as well as one with the benefit of long battery life on the radios themselves.