6.2.5 Telecommunications in mobile networks

Mobile radio communications services are characterised in that the terminal equipment is not connected by means of cables but via radio to the telecommunications network and that it is possible to make mobile use of terminals. Services of this kind make it possible to reach subscribers at mobile user terminals ("mobiles") in the most diverse settings. For the transmission of speech and data between the user terminal and the telecommunications network different frequency ranges are used, depending on the mobile communications systems.

6.2.5.1 Private mobile radio communications systems

PMR (Professional Mobile Radio) systems use radio links to allow closed user groups to use mobile communications. Such PMR networks are typically operated by the users themselves (private trunked radio communications networks), for example, taxi companies or authorities.

Simple analogue FM voice radio systems are increasingly being replaced by digital trunked radio systems (e.g. TETRA). The modern systems make better use of the frequency resources and offer additional features. In particular, both speech and data can be transmitted.

In addition to the professional radio systems, there are cordless systems, such as the digital system DECT, which is designed for use at home or at the office. It uses defined frequency bands that are not assigned to any specific operator. In the case of DECT, the radio resources are managed by intelligent DECT terminals that will always select the best channel. In such systems, the radio connection is between the base station, which is plugged into the telephone outlet of the fixed network, and the mobile - cordless - telephone.