dPMR and DMR are two new digital technologies for PMR voice/data radios. Both technologies have been standardised by ETSI. The DMR system is a two-slot TDMA system offering a range of features and applications (ETSI Standards TS 102 361 and EN 300 113). dPMR® is a FDMA system offering the lowest cost digital voice solution and a similar set of repeater and trunking options to DMR (ETSI Standards TS 102 490, TS 102 658 & EN 301 166).
Both standards use 4-FSK modulation variants, DMR using 9600 bps in 12.5 kHz channels and dPMR 4800 bps in 6.25 kHz channels. Both use voice digitally coded with error correction at 3.6 kbit/s.
Now,we will contrast DMR and dPMR.
Read more on http://blog.retevis.com/dmr/
Read more on http://blog.retevis.com/dpmr/
To reduce the congestion present in today’s crowded radio spectrum, radio channels must be used more efficiently.
The basic idea is to divide existing radio channels in half, thus doubling the number of channels available.
The term “frequency” which most people are aware of, is actually only a spot centre frequency in the middle of a small band of radio spectrum (a channel).
DMR – Digital Mobile Radio – Uses TDMA (Time Division) digital technology in which a 12.5 Khz channel is actually divided into a series of time slots (known as time slot 1 and 2) that are equally spaced in the 12.5 khz spacing. [NOTE: It is argued that this achieves 6.25 khz channel spacing even though using 12.5 khz because a time slot uses 6.25 of the 12.5 spacing].
dPMR – Digital Private Mobile Radio) – Uses FDMA (Freq Division) digital technology in which this can breakdown a 12.5 Khz channel spacing into two 6.25 Khz channel spacing. It does NOT use time slots like TDMA as the frequency is just sliced into equal paths within a 12.5 Khz channel.
Ease of migration from existing analog systems
The obvious difference is the ease of migration from analog systems. With DMR, because the TDMA slots are operating on the same frequency, the resulting infrastructure is much the same as for a narrowband FM system, effectively reducing the cost of system infrastructure. In effect, you only need one repeater, one antenna and a simple duplexer.
Contrast this with infrastructure for an FDMA dPMR system. As both 6.25kHz sub-channels must operate simultaneously, two repeaters (one for each 6.25kHz sub-channel) are required, plus expensive combining equipment for multiple frequencies to share the single base station/repeater antenna.
FDMA infrastructure costs are considerably higher than for 2-slot TDMA DMR. In addition, the losses of the extra combiners may require additional RF Power Amplifiers to maintain the transmitted power level and therefore coverage.
To summarize, 2-slot TDMA DMR makes efficient use of expensive infrastructure and simplifies migration. Compared to FDMA, 2-slot TDMA allows you to achieve 6.25kHz efficiency while reducing investment in repeaters and combining equipment. Much of the combining equipment used in the previous analog FM system can be re-used by a new DMR network.
DMR and dPMR ,which one do u prefer ? Maybe u can tell us your idea and we will Summed up your thoughts to share with other amateurs,
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