digital short range radio (mobile communications) (DSRR)
Digital Short Range Radio (DSRR) is the generic term for digital short-range radio. This term covers a wide variety of technologies such as SRD technology, DECT, CB radio, walkie-talkie, Freenet, private mobile radio( PMR) and short-range radio (DSRR). All short-range technologies are license-free radio technologies that may be operated in specific frequency ranges and may not exceed a maximum transmission power.
Short-range radio (DSSR) is a license-exempt radio technique with intercom operation that may only be used for short ranges. For this short-range application, the German Federal Network Agency makes various frequencies available in the frequency usage plan, including those formerly used by the B network. The 149 MHzfrequency range is cleared for short-range radio, as are other frequency ranges at 430 MHz for LPD (low power device) radio and between 933 MHz and 935 MHz for single- channel transmissions and between 888 MHz and 890 MHz for dual-channel transmissions.
In the 149 MHz range, the permissible transmission power of the radios is limited to a maximum of 0.5 W, which corresponds to a range of about 3 km. The channel spacing and channel width are 20 kHz, which makes it suitable for operational radio. Communication takes place directly between two mobile voice radios on one of three possible channels. Therefore, there is no network structure. Short-range radio operation is restricted in some regions. Another short-range radio technology is Freenet, which also operates in the 149 MHz range, but with a channel spacing of 12.5 kHz.
As part of a European research project by the European Telecommunications Standards Institute( ETSI), short-range radio is being used in private land mobile communications for digital voice and data communications.