TETRA Radio Communication

TETRA is a digital trunked radio communication standard consisting of a set of specifications developed by the European Telecommunications Standards Institute (ETSI). The preparation of the standard started in 1994. The TETRA standard was created as a single European digital standard and was called TETRA (Trans-European Trunked Radio) until April 1997. However, its area of operation is not limited to Europe, so it is currently called TETRA (Terrestrial Trunked Radio).

TETRA is an open standard for communication between manufacturers. Access to TETRA features is free for all interested parties who sign up to the TETRA Memorandum of Understanding and Promotion (TEM TETRA). Currently, TETRA is the most promising digital trunking system, because it is the only international standard that actually has the status of an open standard, supported by many government agencies, manufacturers and operators. TETRA equipment is produced by Motorola, Nokia, OTE, Rohde & Schwarz and other world leading manufacturers. TETRA networks are installed in many European countries, as well as in several countries in Asia, Africa and South America. This system has become a guarantee of safety for the consumer in terms of the use of open standards to share certain functions and reduce dependence on a certain supplier.

Brief specifications. The TETRA radio interface assumes operation in a standard frequency network with a step of 25 kHz and a minimum duplex separation of 10 MHz radio channel. Multiple subbands can be used for TETRA systems. In fact, security services in European countries are allocated 380-385 / 390-395 MHz bands, and commercial organizations are allocated 410-430 / 450-470 MHz bands. TETRA systems in Asia (primarily China) use the 806-870 MHz band.

TETRA standard systems use the Time Division Multiple Access (TDMA) method. Up to 4 independent data channels can be organized on one physical frequency. It uses relative phase modulation such as TETRA / 4-DQPSK (Differential Quadrature Phase Shift Keying). The modulation speed is 36 Kbit/s.

To convert speech, the standard uses a codec that uses a CELP (Code Excited Linear Prediction) type conversion algorithm with a speed of 4.8 Kbit / second. Digital data from the output of the codec is subjected to various coding, interleaving and encryption, after which information channels are created. The bandwidth of one data channel is 7.2 Kbit/s, and the digital data transmission speed is 28.8 Kbit/s.

The TETRA standard supports both voice and data transmission. In this case, speech and data can be transmitted simultaneously from one terminal through different information channels. Digital integrated solutions in the TETRA standard allow to combine professional radio communication (operational and group voice communication), data transmission and classic functions of wireless telephone. Therefore, the TETRA standard opens up new possibilities for the integration and optimization of previously isolated subsystems and, in fact, defines the creation of a new class of solutions.