15-03-2011, 03:37 PM
presented by:
ABHIRUCHI KUMARI
[attachment=10217]
ABSTRACT
Digital radio broadcasting is a technique which gives listeners
interference free reception of high quality sound, easy to use radio, and the potential for wider listening choice through many additional station and services. Current analogue FM radio broadcasting systems in VHF band cannot satisfy demands of future ,such as excellent sound quality, large number of stations and small portable receivers and no quality impairment due to multipath propagation. Digital audio technology has set technical quality standards, which are far beyond those available to radio broadcasting transmitted over the analog FM system. One of its lucrative features is improved mobile radio reception.
INTRODUCTION
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 3GHz 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 For 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.
In short
1992 — 1995 — field trial period.
1996 — 1997 — introduction period
98 onwards — terrestrial services in full swing
For DAB via satellite 1996 — 2001 is planned as experimental stage 2002 —2003 introduction period.
DIGITAL AUDIO DATA
The conversion of analog audio data to the digital domain begins by sampling the audio input in regular, discrete intervals of time and quantizing the sampled values into a discrete number of evenly spaced levels. The digital audio data consists of a sequence of binary values representing the number of quantizer levels for each audio sample This method of representing each sample with an independent code word is called pulse code modulation (PCM
The digital representation of audio data offers many advantages.
• High noise immunity
• Stability
• Reproducibility
Allows the efficient implementation of many audio processing functions (i.e.mixing, filtering, equalization) though the digital computer. According to the Shannon’s theory, a time sampled signal can faith represent signal up to half the sampling rate. The max audible frequency for humans is 20 KHz. Therefore the typical sampling rate is 48 KHz. (i.e. more than twice the signal frequency).
ABHIRUCHI KUMARI
[attachment=10217]
ABSTRACT
Digital radio broadcasting is a technique which gives listeners
interference free reception of high quality sound, easy to use radio, and the potential for wider listening choice through many additional station and services. Current analogue FM radio broadcasting systems in VHF band cannot satisfy demands of future ,such as excellent sound quality, large number of stations and small portable receivers and no quality impairment due to multipath propagation. Digital audio technology has set technical quality standards, which are far beyond those available to radio broadcasting transmitted over the analog FM system. One of its lucrative features is improved mobile radio reception.
INTRODUCTION
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 3GHz 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 For 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.
In short
1992 — 1995 — field trial period.
1996 — 1997 — introduction period
98 onwards — terrestrial services in full swing
For DAB via satellite 1996 — 2001 is planned as experimental stage 2002 —2003 introduction period.
DIGITAL AUDIO DATA
The conversion of analog audio data to the digital domain begins by sampling the audio input in regular, discrete intervals of time and quantizing the sampled values into a discrete number of evenly spaced levels. The digital audio data consists of a sequence of binary values representing the number of quantizer levels for each audio sample This method of representing each sample with an independent code word is called pulse code modulation (PCM
The digital representation of audio data offers many advantages.
• High noise immunity
• Stability
• Reproducibility
Allows the efficient implementation of many audio processing functions (i.e.mixing, filtering, equalization) though the digital computer. According to the Shannon’s theory, a time sampled signal can faith represent signal up to half the sampling rate. The max audible frequency for humans is 20 KHz. Therefore the typical sampling rate is 48 KHz. (i.e. more than twice the signal frequency).
