The main objective is to in-depth analyze possible techniques for adapting DVB-S2 / DVB-RCS standards to mobile systems operating at Ku- or Ka-bands whilst retaining, as much as possible, backward compatibility with current version of the standards. Both Line-Of-Sight (LOS) and non-LOS application scenarios will be covered by the investigation. In particular, major emphasis will be on application in the aeronautical, maritime and railway domains.
A key objective of the study is to also provide inputs to the standardization fora as well as to generate a technological roadmap for system evolution.
A satellite based broadband mobile system consists of a network of mobile terminals interconnected to a gateway /Hub by transparent satellite DVB-RCS or SATMODE return and forward links. The mobile will traverse the coverage area beams that are in general served by a multiple of gateways and satellites. The gateways are backhauled to terrestrial network access points and to Network Control and Network operations facilities by either a terrestrial ground network or other satellite networks. A typical network architecture is shown in the figure below.
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Key adaptations required to successfully extending DVB-S2 /DVB-RCS to the mobile environment include seamless beam, gateway, and satellite handover, synchronization maintenance, Doppler frequency compensation, antenna pointing, initial signal acquisition and subsequent tracking.
For non-LOS mobile propagation channels (e.g. trains), countermeasures against momentary loss of signal and possibly associated burst errors will also be needed. This may include optimization at the physical layer (e.g. fast reacquisition techniques or diversity exploitation) and at the upper layers (e.g. exploitation of upper layer FEC or random access to complement DAMA) as well as the integration with terrestrial networks (either integral gap-filler or external mobile networks).
The project plan is divided into three tasks:
- Definition of Reference Scenarios for aeronautical, maritime and land-mobile applications, including technical characteristics and regulatory aspects
- Consolidated list of issues that need attention in system design and standardisation, and initial identification of techniques to overcome them
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- Detailed analysis of proposed modification to the current standards in terms of achievable system performances and impact on back-compatibility
- Contribution to standardization fora
- Elaboration of a technological roadmap for system evolution
Key issues to be addressed in the study are:
- DVB-S2 /RCS physical layer adaptation to mobility, including countermeasures against link interruptions
- Adaptation of System Synchronisation strategies to the mobile environment
- Impact of mobility on the MAC layer and investigation of the merits and potential of random access to complement DAMA on the reverse link
- Impact of mobility on resource management, including demand-assignment
- Mobility management (Handover strategies)
- Network issues, including inter-working with terrestrial gap-fillers
The present work is expected to provide significant contributions to the extension of the DVB-S2 /RCS standards to the mobile environment. This will allow to expand the satellite communication presence in the aeronautical and maritime market by improving the service offer through the provision of broadband capacity to the user at a lower cost per bit. Furthermore it will allow the satellite to effectively compete with terrestrial system in the provision of broadband services in selected land mobile scenarios like the railways one.
Task 1: reference scenarios for the assessment of proposed techniques have been finalized.
Task 2: potential solutions have been provided which are suitable to overcome critical issues for the adaptation of the DVB-RCS standard to a mobile environment, addressing especially the physical, link and network layers.
The study has been supporting the DVB-RCS working group for the specification and the guidelines.
The study has provided a business case assessment and a technological roadmap as a conclusion.
Last Update: 30 Jul 2008