22-09-2008, 10:37 AM
Definition
Digital audio broadcasting, DAB, is the most fundamental advancement in radio technology since that introduction of FM stereo radio. It gives listeners interference - free reception of CD quality sound, easy to use radios, and the potential for wider listening choice through many additional stations and services.
DAB is a reliable multi service digital broadcasting system for reception by mobile, portable and fixed receivers with a simple, non-directional antenna. It can be operated at any frequency from 30 MHz to 36Hz for mobile reception (higher for fixed reception) and may be used on terrestrial, satellite, hybrid (satellite with complementary terrestrial) and cable broadcast networks.
DAB system is a rugged, high spectrum and power efficient sound and data broadcasting system. It uses advanced digital audio compression techniques (MPEG 1 Audio layer II and MPEG 2 Audio Layer II) to achieve a spectrum efficiency equivalent to or higher than that of conventional FM radio.
The efficiency of use of spectrum is increased by a special feature called Single. Frequency Network (SFN). A broadcast network can be extended virtually without limit a operating all transmitters on the same radio frequency.
EVOLUTION OF DAB
DAB has been under development since 1981 of the Institute Fur Rundfunktechnik (IRT) and since 1987 as part of a European Research Project (EUREKA-147).
" In 1987 the Eureka-147 consoritium was founded. It's aim was to develop and define the digital broadcast system, which later became known as DAB.
" In 1988 the first equipment was assembled for mobile demonstration at the Geneva WARC conference.
" By 1990, a small number of test receivers was manufactured. They has a size of 120 dm3
" In 1992, the frequencies of the L and S - band were allocated to DAB on a world wide basis.
" From mid 1993 the third generation receivers, widely used for test purposes had a size of about 25 dm3, were developed.
" The fourth generation JESSI DAB based test receivers had a size of about 3 dm3.
1995 the first consumer - type DAB receivers, developed for use in pilot projects, were presented at the IFA in Berlin.
