Background
Information on Digital Sound Broadcasting Digital
Sound Broadcasting is a general term covering a wide range of systems
and technologies, including Eureka 147 and ISDB-T, which are designed
to replace Frequency Modulation (FM) broadcasting, Digital Radio Mondiale
(DRM), a possible successor to Amplitude Modulation (AM), as well as IBOC,
which is intended to complement the existing AM and FM services. However,
these technologies have one common point, i.e., they cannot be received
with the existing radios.
Eureka
147
Proposed by the European Broadcasting Union, Eureka 147 is widely applied
in Europe, Canada and part of Asia. The technology operates in the new
L-band or VHF Band III. Its 1.5 MHz bandwidth can accommodate a maximum
of about 1.2 Mbps of data. Eureka 147 employs both 48KHz and 16bit sampling
rates for audio playback. The signal is then compressed with MPEG1-Layer
2 technology. The system allows a flexible range of frequencies between
64 -- 192 Kbps for mono channels. Generally speaking, a 1.5 MHz channel
can carry up to six 256 Kbps stereo channels plus a few Program Associated
Data.
For details,
please refer to the official web site: http://www.worlddab.org
ISDB-T
ISDB is a new technology developed by the Science and Technical Research
Laboratories, NHK. The standard, which was designed as a fully-digitised
television broadcasting system in 1994, is only used in Japan. Indeed,
the technology is capable of transmitting multiple television channels,
multimedia service and tele-text data at the same time. Radio broadcast
is one of the functions that can be supported by ISDB.
The use
of MPEG-2 AAC compression and multiplex technologies makes it possible
to transmit signals through satellite, terrestrial and mobile means. As
a unique feature, ISDB permits user to receive a low-resolution edition
in favour of better mobile reception. In an interference-free environment,
viewers may choose to receive a high-resolution edition for better picture
and sound quality.
For details,
please refer to the official web site: http://www.dibeg.org
IBOC
The IBOC technology, as proposed by the US-based iBiquity Digital Corporation,
is also known as HD Radio. It is designed to operate in the existing AM
and FM bands by attaching digital data to the ��sideband�� of analogue
signals. The attached segment can either be a separate radio channel or
other data. Limited by available bandwidth, the maximum size of the signal
is about 200 Kbps. While the technology aims to better utilise existing
spectrum, it is technologically complicated. A new version of the system
is said to be in the pipeline.
For details, please refer to
official website: http://www.ibiquity.com
DRM
DRM Consortium was formed in 1998 by broadcasters
in Europe. The system has taken a relatively short development track.
A number of broadcasters, notably BBC, Deutsche Welle, Radio Netherlands,
Voice of America and Radio Canada International, have begun transmission
in DRM mode in June this year.
DRM is
a technology aims to improve sound quality of AM transmission below 30
MHz and to reduce interference common in medium wave environment. New
compression technologies known as MPEG4 Advanced Audio Coding (AAC) and
Spectral Band Replication (SBR) are employed to offer sound quality comparable
to that of FM transmission.
For details,
please refer to the official web site: http://www.drm.org/indexdeuz.htm
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