DVB-H is a technical specification for the transmission of digital TV to handheld receivers such as mobile telephones and PDAs. Published as a formal standard (EN 203 204) by ETSI in November 2004, it is a physical layer specification designed to enable the efficient delivery of IP-encapsulated data over terrestrial networks. The creation of DVB-H, which is closely related to DVB-T, also entailed modifications of some other DVB standards dealing with data broadcasting, Service Information, etc. It can be used as a bearer in conjunction with the DVB-IPDC systems layer specifications or alternatively with the OMA BCAST specifications. A non-proprietary open standard, DVB-H has broad support across the industry and services are now on air in more than ten countries.
DVB-H is an extension of DVB-T with some backwards compatibility, i.e., it can share the same multiplex with DVB-T. It uses a mechanism called multi-protocol encapsulation (MPE), making it possible to transport data network protocols on top of MPEG-2 transport streams. A forward error correction (FEC) scheme is used in conjunction with this to improve the robustness and thus mobility of the signal. In addition to the 2k and 8k modes available in DVB-T, a 4k mode is added to DVB-H giving increased flexibility for network design. A short “in-depth” interleaver was introduced for 2k and 4k modes that leads to better tolerance against impulsive noise (helping to achieve a similar level of robustness to the 8k mode).
Another essential element of DVB-H is Time Slicing, the main technique used to achieve the required power savings. Each individual TV service in a DVB-H signal is transmitted in bursts allowing the receiver to go into sleep mode, only waking up when the service to which it is “tuned” is transmitted. For handheld devices this can add up to very significant power savings in the front-end. For battery life and thermal balance this is a key functionality. Statistical multiplexing is also possible in DVB-H, ensuring optimum use of bandwidth to deliver services. DVB-H is designed for use in Bands III, IV and V as well as L-band.