Terrestrial Trunked Radio - Advantages of TETRA

Advantages of TETRA

The main advantages of TETRA over other technologies (such as GSM) are:

• The much lower frequency used gives longer range, which in turn permits very high levels of geographic coverage with a smaller number of transmitters, thus cutting infrastructure costs.
• During a voice call, the communications are not interrupted when moving to another network site. This is a unique feature which dPMR and DMR do not offer.
• High spectral efficiency - 4 channels in 25 kHz and no guard bands, compared to GSM with 8 channels in 200 kHz and guard bands.
• Very fast call set-up - a one to many group call is generally set-up within 0.5 seconds (typical less than 250 msec for a single node call) compared with the many seconds (typically 7 to 10s) that are required for a GSM network.
• Works at high relative speeds >400 km/h. TETRA was used during the French TGV train speed record on 3 April 2007 at 574.8 km/h.
• The system contains several mechanisms, designed into the protocols and radio parameters, to ensure communication success even during overload situations (e.g., during major public events or disaster situations), thus calls will always get through unlike in cellular systems. The system also supports a range of emergency calling modes.
• TETRA infrastructure is usually separate from (but connected to) that of the public (mobile) phone networks, resulting in (normally) no call charges for the system owners, substantially more diverse and resilient communications and it is easy to customise and integrate with data applications (vehicle location, GIS databases, dispatch systems, etc.).
• Unlike most cellular technologies, TETRA networks typically provide a number of fall-back modes such as the ability for a base station to process local calls. So called 'mission critical' networks can be built with TETRA where all aspects are fail-safe/multiple-redundant.
• In the absence of a network mobiles/portables can use 'direct mode' whereby they share channels directly (walkie-talkie mode).
• Gateway mode - where a single mobile with connection to the network can act as a relay for other nearby mobiles that are out of range of the infrastructure.
• TETRA also provides a point-to-point function that traditional analogue emergency services radio systems did not provide. This enables users to have a one-to-one trunked 'radio' link between sets without the need for the direct involvement of a control room operator/dispatcher.
• Unlike cellular technologies, which connect one subscriber to one other subscriber (one-to-one), TETRA is built to do one-to-one, one-to-many and many-to-many. These operational modes are directly relevant to the public safety and professional users.
• TETRA supports both air-interface encryption and end-to-end encryption
• Rapid deployment (transportable) network solutions are available for disaster relief and temporary capacity provision.
• Equipment is available from many suppliers around the world, thus providing the benefits of interoperable competition.
• Network solutions are available in both the older circuit-switched (telephone like) architectures and flat, IP architectures with soft (software) switches.

Further information is available from the TETRA Association (formerly TETRA MoU) and the standards can be downloaded for free from ETSI.