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