Towards the Revision of DVB-S2/RCS Standard for the Full Support of Mobility

Satellite communications developed to a tremendous global success in the field of analogue and then digital audio/TV broadcasting by exploiting the inherent widearea coverage for the distribution of content. It appeared a "natural" consequence to extend the satellite services for point-to-point multimedia applications, by taking advantage of the ability of satellite to efficiently distribute multimedia information over very large geographical areas and of the existing / potential large available bandwidth in the Ku / Ka band. Particularly in Europe, due to the successful introduction of DVB-S [1], a promising technical fundament has been laid for the development of satellite communications into these new market opportunities using the second generation of DVB-S [2], as well as DVB-RCS [3] standards. Thus, for satellite systems currently under development and being designed to support mainly multimedia services, the application of the DVB-S2, for the high-capacity gateway-to-user (forward) links and of DVB-RCS for the user-to-gateway (return) links is generally accepted. In addition to satellite multimedia services to fixed terminals, people are getting more and more eager to have broadband communications on the move. Mobile telephones subscriptions have exceeded fixed line subscription in many countries. Higher data rates for mobile devices are provided by new standards such as UMTS, HSDPA, 1xEV-DO. New standards for mobile broadcasting are also appearing, such as DVB-H [5]. At present, broadband access (e.g. to the Internet) and dedicated point-to-point links (for professional services) are rimarily supplied by terrestrial networks. Broadband satcoms services are still a niche market, especially for mobile users. In this context, many transport operators announce the provision of TV services in ships, trains, busses and aircraft. Furthermore, Internet access is offered to passengers. With IP connectivity, also radio interfaces for GSM can be implemented for such mobile platforms by using satellite connectivity for backhauling. Thus, DVB-S2/RCS appears an ideal candidate to be investigated for mobile usage, as it can ideally combine digital TV broadcast reception in mobile environments (AirTV, luxury yachts, trains, etc…) and IP multimedia services. Although an annex of RCS implementation guidelines [4] analyses the limitation under which the aforementioned standards could be used within mobile environments, it has to be kept in mind that they have not been designed for mobile use. Collective terminals instaled in a mobile platform, such as train, ship or aircraft, are exposed to a challenging environment that will impact the system performance considering the current standard in absence of any specific provision. Mobile terminals will have to cope in general with stringent frequency regulations (especially in Ku-band), Doppler effect, frequent handovers, and impairments in synchronization acquisition and maintenance.