Hannover - In the event of a failure of the distribution link (modulation lines) to digital radio transmitters (DAB+), a stable radio broadcasting provision to the population must be guaranteed. As recent events have shown in the event of a disaster, broadcasting coverage in particular is an essential building block for informing citizens, since mobile phone networks are usually the first to fail. In order to increase the reliability of the broadcast an alternative distribution must be used during standard link failure (land-based lines in the event of flooding or satellite reception in the event of storms).
For this purpose, RFmondial has developed a system that uses the regular air interface for the distribution, the so-called rebroadcasting. Those DAB+ transmitters that are no longer able to receive their standard link receive the program over the air from another DAB+ transmitter, convert it to a different frequency (channel) and transmit it again with a short time delay. This transmitted program is now received by one or more other DAB+ transmitters and broadcast again on a different frequency. This guarantees nationwide broadcasting coverage even in the event of a disaster. In addition, the control of the transmitters can as well be maintained via a data channel hidden in the DAB+ broadcast.
The RFmondial technology was developed and tested in a field test in Hanover. For this purpose, a multiple frequency network (MFN) was operated, with a DAB+ transmitter (channel 5A) serving as the basic network transmitter in Hanover Hemmingen and another DAB+ transmitter (channel 7C) serving as a transmitter in rebroadcasting mode in Hanover Nordstadt. In addition to testing the rebroadcasting technology, the suitability of DAB+ receivers for switching to the now changed transmission frequency (service follow) has been examined. Manufacturers of consumer and automotive receivers took the opportunity to test and, in some cases, improve their receivers with regard to rebroadcasting.
New developments by Plisch GmbH from Viernheim were used as DAB+ transmitter systems, which are equipped with various redundancies and thus ensure trouble-free operation. The complete product portfolio can be found at www.plisch.com.