The DMR standard is designed to operate within the existing licensed frequency bands with a channel spacing of 12.5 kHz used in land mobile radio communications (portable and mobile radios). The DMR standard provides voice, data, and other value-added services.
The user, having in service a number of analog radios and acquiring new DMR standard can be sure that the new stations work well as in the “digital” standard, and easily interfaced with the old fleet of analog radios. This allows for a gradual transition to digital communications, without changing all radios at once, and as the entire fleet is replaced, the transition to digital high-quality communications can be made immediately.
Quality means not only intelligibility, but also transmission of intonation and individual features of the subscriber's speech. The transmission of speech in digitized form at a channel speed of 1.2 kbps is considered quite sufficient for understanding, but at this speed individual features of speech are not transmitted. In DMR radios, speech information is digitized and transmitted at a channel rate of 3.6 kbps, which has a positive effect on the quality of the transmitted speech.
Conversion of speech information into digital and vice versa is a very complex process. In DMR radios, the AMBE2+ protocol is responsible for speech conversion, which digitizes only the main phonemes of speech. Thus, when digitizing speech, the protocol does not convert the entire incoming speech spectrum, but the necessary number of narrowband parts of the speech spectrum - the basic phonemes. Only information about characteristic speech phonemes of the original speech is transmitted to the communication channel. Thus, the protocol, encoding speech, “cuts out” and does not transmit to the subscriber all extraneous noises that are present in the exchange between correspondents. The sound of a car passing by will not be a phoneme, because a phoneme refers only to human speech. Sound of boiling kettle, working jackhammer, noise of forest, dripping water - all these sounds are not phonemes, are not analyzed by the protocol, because they are not connected with human speech and words and thus are not transmitted to the subscriber. And the subscriber at reception hears quality speech without extraneous noises.
Another great advantage of digital processing is the ability to realize “narrowband transmission”. This ensures that the speech message is transmitted with a minimum amount of transmitted data. Thus, the AMBE2+ protocol only needs a bandwidth of 6.25 kHz. (which is half the band width of standard analog technologies, which is 12.5 kHz), and the methods of processing and error correction contribute to improving speech intelligibility, preserving the quality of speech when transmitting in conditions of strong noise.
The radio station, working on one of the channels for “transmission” actually radiates only half the time, and therefore consumes twice less energy. In practice, the saving of battery charge reaches 25-35% depending on the operating conditions.
Analog and digital radios have the same sensitivity, and with the same output power of DMR radios, thanks to digital signal processing, have a slightly larger coverage area with the same high quality of communication.
Digital signal processing used in DMR digital radios has another advantage - it is the realization of speech encryption without loss of quality. And encryption is not just initialized, but is set by the consumer in the form of entering an individual key. And you can be sure that no outsider will be able to listen to you.
So, to summarize. The advantages of DMR radios include: