Following the success and wide adoption of the European Digital Video Broadcasting for Terrestrial (DVB-T) standard for digital terrestrial television, numerous coordinated research efforts on digital broadcast technology resulted in the recent standardization of Digital Video Broadcasting for Handeld Devices (DVB-H). The new specification aims at defining the physical and link-layer level of a digital broadcast network for Internet protocol (IP) datacasting services. At its core, DVB-H is based on DVB-T but it is more oriented in mobile and stationary reception by handheld devices. This article attempts a brief though thorough overview of the new technology, its technical aspects, and its new application perspectives.
TopBackground
During the mid-1990s, the MPEG-2 Transport Stream (TS) (International Organization for Standardization [ISO], 1996) was accepted worldwide as baseband format for digital television networks. Its structure allows the transmission of encoded digital video and audio streams, along with IP data, organized in a statistical Time Division Multiplex (TDM). The need for an efficient physical layer arose, which would deliver the MPEG-2 TS to the end-user terminals via the “difficult” terrestrial channel.
Several research efforts have been conducted around the world to optimize the physical layer for terrestrial digital television (DTV). North America adopted the ATSC A/53 system, developed by the Advanced Television Systems Committee (ATSC) in 1995, based on 8-VSB modulation. In Japan, the Association of Radio Industries and Businesses developed in 1998 the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) specification for the same purpose.
In Europe, DVB-T was standardized by the European Telecommunications Standards Institute (ETSI) in 1997 as a transmission system designed and optimized for terrestrial DTV configurations. Although it was initially designed for stationary use, DVB-T also presented an outstanding performance in mobile reception (Stare, 1998), where it outclassed ATSC (Wu, Pliszka, et al., 2000). To further support the perspective of mobile DTV, ETSI introduced in 2004 the DVB-H specification (Digital Video Broadcasting (DVB); Transmission System for Handheld terminals (DVB-H), 2004). DVB-H substantially comprises of a set of extensions to DVB-T which are oriented to handheld use. DVB-H inherits all the benefits of its predecessor and adds new, mobile-oriented features, focusing on IP datacasting and including better mobility and handover support, adaptive per-service error protection and power saving capabilities. At present, DVB-H is the dominant open standard in its field, and compliant systems are being deployed around the world, including Europe, the United States, and China. A strong competitor of DVB-H is Terrestrial Digital Multimedia Broadcasting (T-DMB), a standard developed in Korea and Japan, based on the European Digital Audio Broadcasting (DAB). A third player in the field of handheld DTV is Media Forward Link Only (MediaFLO), a U.S. proprietary technology developed by Qualcomm, which is gaining ground in North America.
The ETSI specification defines DVB-H as a “broadcast transmission system for datagrams.” Like DVB-T, it specifies the physical and link layers, along with the service information. A DVB-H-compliant broadcast platform consists substantially of a DVB-T chain, including all the enhancements introduced by the new specification (Figure 1). Since a broadcast platform has no native support for interactivity, an IP-based cellular infrastructure (like WLAN, 2G/3G) can be employed complementarily to enable for fully interactive applications.
Figure 1. Block diagram of a DVB-H system
It must be clarified that most of the innovative features of DVB-H, as explained in the next section, are implemented on the link layer and do not affect the DVB-T physical layer. This allows the new technology to inherit all the benefits of its predecessor, including flexible transmission schemes providing from 5 up to 32Mbps of capacity, excellent multi-path performance, due to the use of OFDM (Orthogonal Frequency Division Multiplexing), use of TV bands UHF using 8 MHz channels, and SFN-based operation.