With ever increasing demand on the radio spectrum and the limited number of frequencies available, the need for efficient technologies that maximise the utility of those frequencies has never been greater.
With ever increasing demand on the radio spectrum and the limited number of frequencies available, the need for efficient technologies that maximise the utility of those frequencies has never been greater.
Without getting too technical, the basic difference between FDMA (Frequency Divided Multiple Access) and TDMA (Time Divided Multiple Access) is the definition of a channel and how it is used (accessed). In FDMA, a particular bandwidth (E.g. 6.25kHz) at a particular frequency (E.g. 150.000MHz) is used to define a channel in essentially the same way channels have been allocated for decades. In TDMA, the same principle applies regarding bandwidth and frequency but the signal is divided into time slots that allow the channel to have 'extra' capacity in the same bandwidth E.g. Two 6.25kHz 'equivalent' channels in a 12.5kHz channel. See the diagram below for a graphical explanation.
Until now, TDMA was more spectrum efficient at wider channel spacing like 25kHz as, for example, two or three users could access the same bandwidth as one FDMA channel user. However, in the case of the newly developed narrowband 6.25kHz FDMA technology like dPMR, both this and 2-slot 12.5kHz TDMA technology achieve the same result as far as spectrum efficiency is concerned.
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The dPMR Association was established in 2007 and provides a forum for interested parties to contribute their expertise.
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