DVB-T Hierarchical Modulation: An Opportunity for New Services?

Abstract

The European DVB-T standard includes a large number of transmission modes able to adapt the COFDM signal to a wide variety of broadcasting services. Among them, the hierarchical modulation mode separates the RF channel in two virtual channels, each able to carry a transport streams (MPEG-TS) with a dedicated protection. In a first approach, this DVB-T capability has been view as a way to define two distinct coverage areas for a given transmitter. Accordingly, no direct application has been seen for it. Today, broadcaster’s intend to use the DVB-T standard to cover a great variety of Services : • Some countries intend to use DVB-T to broadcast HDTV; accordingly they have a need to simulcast the DVB multiplex in its high and standard definitions, to address the two categories of receivers which will be used during the introduction phase of Digital TV services, • Another great expectation is to use DVB-T to address mobile receivers, in public transport : it will be a great advantage to setup a unique transmitters network to reach simultaneously indoor and outdoor receivers. Due to the lack of frequencies available, the DVB-T’s hierarchical modulation becomes an interesting way to make a single RF channel able to address two categories of receivers and, as a consequence, two market segments. After an tutorial explanation of the hierarchically modulated DVB-T COFDM signal, the author details the technical trade-of the broadcaster has to make to broadcast the DVB-T hierarchical modulation. Is the DVB-T hierarchical modulation an opportunity for new digital terrestrial TV services ? The author intends to bring you his conviction in this presentation.