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Satellite-based telecom systems probably represent the easiest solution to reduce the digital divide in less-favoured areas owing to their wide geographical coverage and the speed and ease of deployment of terminal equipment. However, a satellite system must be efficient, cost-effective and capable of full inter-working with state-of-the-art terrestrial broadband networks. This paper presents the architecture and the main performance results of a two-way broadband satellite-based system that was developed in the framework of the European Commission's FP6 UNIC project (UNIversal satellite home Connection). The aim of UNIC was twofold: on one side, it addressed the urban–rural digital divide by exploiting at best the features of existing advanced two-way satellite technologies; on the other, the project also investigated how to bridge the ‘social divide’ that arises from the lack of computer ownership or computer literacy of certain classes of end-users, by providing interactive services on a standard TV set through an ad-hoc Set-Top-Box. The UNIC system architecture is based on DVB-S2 and DVB-RCS technologies in the forward and the return link, respectively, possibly paired by a local terrestrial wireless network (e.g. Wi-Fi) for the distribution of connectivity to end-users. The UNIC set-top box is fed by the satellite gateway via a standard IP connection either through the local terrestrial network or directly to the satellite network. Management of the satellite bandwidth is optimized by the UNIC platform through the adoption of an adaptive resource allocation technique based on the flexible framing structure of DVB-S2: the key factor in this respect turns out to be the feature of adaptive coding and modulation (ACM), together with a suited quality of service (QoS) policy to control the amount of data that are fed into the network. Copyright © 2010 John Wiley & Sons, Ltd. |
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