Commonly referred to as TETRA.
TETRA is a set of open standards developed by
ETSI for digital trunked radio systems. It is the first truly open international standard for the digital professional mobile radio environment. TETRA is meant to replace old analogue
PMR systems.
The standard has similarities to public cellular networks (such as
GSM in europe), but has several improvements to suit professional needs.
Benefits and key features include:
- Better channel efficiency compared to analogue systems
- 4 channels per one frequency pair, 25kHz carrier
- Advanced data services
- Offers data transfer services
- Allows combined use of voice and data
- Security
- End-to-end encryption for speech data
- Encryption for signalling on the radio path
- Multivendor environment
- Standards for radio interface and network elements interface
- Allow usage of radio units, portables and network elements from different vendors (much like GSM)
- Better voice quality
- Digital media reduces signal degradation
- Efficient group communication
- Possible to organize subscribers into groups (dynamically) and allow them to communicate with each other as a group
- Several levels of call priviliges
- For example an emergency call always get's network resources, a less significant call is dropped if necessary
- Direct mode operation and fast call setup
- PTT (push-to-talk), call is connected instantaneously when the caller pushes the PTT
(as opposed to several seconds in public cellular networks)
http://www.etsi.org/tetra/