Transport and time-slicing mechanisms in multistandards for mobile broadcasting

Abstract

In a multimedia broadcasting system, the transport mechanism performs all the necessary adaptation and multiplexing functions in order to adapt the IP or the raw, non-IP multimedia streams to the final baseband format that will be sent to the modulator. In this sense, it can be actually considered as a separate layer in the broadcasting system layer stack (Fig. 9.1). However, we avoid calling it as the "transport layer" in order not to confuse it with the transport layer of the OSI (Open Systems Interconnection) model, which has a slightly different hierarchical position. Some fundamental functions that the transport mechanism includes are: • Packetization of contiguous non-IP multimedia streams • Encapsulation and framing of IP data • Separation of the entire TDM (Time Division Multiplex) into "logical channels" so as to convey discrete services • Time-slicing organization and signalling, for energy conservation at the receiver • Transport-Level FEC (Forward Error Correction), for extra per-service FEC protection in addition to the coding inserted at the modulator The following sections provide an overview of the transport mechanisms which are used by the main contemporary multimedia broadcasting systems. The rest of this chapter is organized into as follows. Section 9.2 is devoted to the MPEG-2 Transport Stream (TS) employed in most broadcasting standards including DVB-H (Digital Video Broadcasting for Handheld mainly developed in Europe), T-DMB (Korean's Terrestrial Digital Multimedia Broadcasting), A-VSB (Advanced Vestigial Sideband, developed in the USA), DMB-T/H (Digital Terrestrial Multimedia Broadcast, being implemented in China), ISDB-T (Japanese Integrated Services Digital Broadcasting) and CDMB (China's Digital Multimedia Broadcasting). In Sects.9.3 and 9.4, the transport mechanisms in DAB-IP (Digital Audio Broadcasting - IP System) and Media FLO (Media Forward-Link-Only system developed by Qualcomm, Inc) are presented. Some conclusions and further discussion are included in the last section. © 2009 Springer Science+Business Media, LLC.