What is TETRA?
- Terrestrial Trunked Radio (TETRA) is the modern digital private mobile radio (PMR) technology.
- It can be infrastructure like GSM network of infrastructureless like mobile ad hoc network.
- TETRA offers services addressing mainly to public safety and security services.
- This technology is used by the police, fire, ambulance, transport, security, and other emergency services.
Application
- Provides usual cellular services (One-to-One)
- Professional radio services (group communication)
- Instantaneous communication, both between individuals and within a group of an unlimited size.
- Priority calls can be made.
- Field workforce management services (Graphical Dispatcher Workstation)
- Limited data services.
- Maximum security.
- Services cost less than other communications.
The Technology
- TETRA can be infrastructured like GSM network.
- TETRA base stations (TBS) and
- Mobile stations (MS)
- The MS can act as mobile phones, with a full-duplex direct connection to other TETRA users or the PSTN.
- It can be infrastructure less like MANET.
- MS can act as a walkie talkie and communicate directly with each other
- Emergency buttons allow to transmit emergency signals
Figure: Combination of infrastructured and infrastructureless TETRA
Modes of operation
- Trunk mode operation (TMO): MSs communicate using the trunked infrastructure
- Direct mode operation (DMO): MSs act as walkie talkie and communicate directly with each other. DMO only supports half duplex communication and it can use TETRA terminals as relays for signals.
TETRA can combine two modes, TMO and DMO, into single terminal equipment
Modes of Communication
- Individual Communication Mode
- Call is initiated with a push to talk button
- Connection is established in less than half a second.
- Group Communication mode:
- A group may have ten to hundred members
- Can be predefined or dynamically created.
- The call is initiated by pressing the push to talk button and all users of the same group can hear the communication.
Pros and Cons
- Self-configuring network of mobile nodes connected by wireless links
- Nodes move randomly free
- Topology changes rapidly and unpredictably
- Standalone or connected to the larger Internet
- Suitable for emergency situations like natural or human-induced disasters, military conflicts, emergency medical situations, etc.
- Comparatively expensive handsets (500 EUR)
- Relatively slow data transfer rate
