The DMR Association and manufacturers often claim that DMR has superior coverage performance to analogue FM. After overhead, forward error correction, and splitting into two channels, there is 2,450 b/s left for a single voice channel using DMR, compared to 4,400 b/s using P25 and 64,000 b/s with traditional telephone circuits. The modulation is 4-state FSK, which creates four possible symbols over the air at a rate of 4,800 symbols/s, corresponding to 9,600 b/s. The DMR standard operates within the existing 12.5 kHz channel spacing used in land mobile frequency bands globally, but achieves two voice channels through two-slot TDMA technology built around a 30 ms structure. TS 102 361-2: Voice and generis services and facilities The DMR interface is defined by the following ETSI standards: In practice, many brands have not adhered to this open standard and have introduced proprietary features that make their product offerings non-interoperable. The primary goal of the standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers are not locked into a proprietary solution. DMR tiers I and II (conventional) were first published in 2005, and DMR III (trunked) was published in 2012, with manufacturers producing products within a few years of each publication. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discreet 6.25 kHz channels using frequency division.ДMR was designed with three tiers. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. Digital mobile radio (DMR) is an open digital mobile radio standard defined in the European Telecommunications Standards Institute (ETSI) Standard TS 102 361 parts 1вЂ“4 and used in commercial products around the world.

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