For communications between fixed and mobile stations, radio links are used. The ongoing development of communications increases the demand for those communications between fixed and mobile stations at any point, even in tunnels.
In tunnels however, the propagation properties of electromagnetic waves used for mobile communication are very unsatisfactory. Transmission in tunnels by means of antennas is often difficult, this is why a major interest in devices such as radiating cables exists.
There is a wide variety of needs for underground radio communications, for instance:
- Mobile communication (GSM, PCN/PCS, DECT...) in building, tunnel or subway.
- Communications in underground areas, like car parks, large buildings, mine tunnels, etc.
- Retransmission of FM-Radio (88-108MHz) in road tunnels
- Relaying radio communications of emergency services in road tunnels -Relaying of radiotelephony in road tunnels
- Communications in underground railways or in railway tunnels
The development of new mobile radio systems requires new radiating elements allowing the retransmission of the 900 MHz band with an acceptable attenuation.
Mobile radio communications today show the following trends:
- towards higher frequencies: applications shift from 50-150 MHz to 450-900 MHz and 1800-2200 MHz, 2400-6000 MHz
- MiMo transmission for high data rate communication
- towards higher quality links: digital transmissions, high bit rates, ...
- towards a denser integration in urban zones and confined areas: tunnels, half-buried motor ways, underground parking lots, etc
- more wireless communication for automation in production areas, high-bay warhouses, logistics etc