Protocols and Signalling for Adaptive Fade Mitigation Techniques (FMT) in DVB-RCS Multi-Beam Systems: Audens ACT

Objectives

The project is aimed at the identification, analysis and optimisation of adaptive Fading Mitigation Techniques (FMT) together with the corresponding protocols, signalling information and formats in order to significantly increase the efficiency of future broadband DVB-RCS based satellite systems as compared to current systems.

As a consequence, this activity is intended to study and propose appropriate FM techniques including physical layer, signalling, MAC protocols and resource allocation (RA) algorithms for the different link types of a transparent as well as regenerative satellite system scenario. This includes the different services with different Quality of Service (Q.o.S.) requirements in order to demonstrate the achievable system efficiency under realistic conditions.

The demonstration/assessment needs to take into account physical layer impairments, such as channel estimation errors, synchronisation performance, impact of non-linearity, interference, limitations concerning the order of modulation and FEC coding type and rate, as well as traffic, required signalling overhead, imperfections of the resource allocation or induced latency. The performance of the FMT solutions for the various reference scenarios will be demonstrated/assessed through detailed simulations.

Challenges

Key issues being addressed in the study:


  • Modelling of Ka-band propagation impairments,

  • Optimisation of adaptive Fade Mitigation Techniques for DVB-RCS based transparent and regenerative multi-beam satellite systems,

  • Definition of appropriate MAC protocols and RA algorithms well adapted to the envisaged FMT,

  • Definition of signalling and framing.

Benefits

With optimised adaptive Fading Mitigation Techniques DVB-based satellite systems will gain a higher spectral efficiency compared to systems applying current standards. This will lead to improved satellite system capacity and throughput at satellite as well at the users' terminal side. Moreover, applying advanced FMT may increase the system's availability.

Features

The analysis and optimisation of candidate Fade Mitigation Techniques is based on two different satellite system scenarios, the reference system scenarios:


  • A system with a transparent/bent-pipe satellite, multi-beam coverage and a high speed forward and a low data rate bursty return link. A multistar network configuration is assumed, i.e., each Gateway supports the users in a certain number of beams, any link between users needs a double hop through the satellite (no inter-beam connectivity).


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  • A satellite system characterised by a regenerative multi-beam satellite. The on-board regeneration permits high flexibility in user connectivity and permits apparently physical layer format changes between up and down link.


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Furthermore, for both system scenarios three physical layer assumptions, reflecting different degrees of adaptive FMT employment, are considered:

  • Benchmark System: The physical layer corresponds to the current DVB-S/RCS standards, i.e. QPSK modulation and concatenated, turbo coding, respectively, with fixed coding rate. The resulting system represents the "benchmark" against which the other systems applying more enhanced FM techniques are compared. It needs to be noted that, because the current standard foresees already the employment of a specific adaptive FMT, i.e., uplink power control, the application of this technique is assumed the benchmark system as well.

  • Adaptive System A: In addition to power control, FEC coding with adaptable, variable coding rate is applied, the modulation is QPSK.

Plan

The project activities are grouped in four major tasks and subsequently addressed in the noted order:




  • Reference scenarios and performance requirements definition and review of Ka-band characteristics,

  • FMT high-level analysis and trade-off,

  • Protocols and signalling definition,

  • FMT detailed performance assessment.





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    Current status

    The project is completed and the main results outlined below:

    It turned out that the application of flexible Adaptive Coding and Modulation (ACM) leads to a significant increase in the efficiency and capacity of the system when compared to a system with a fixed physical layer. It has been shown that the proposed physical layer adaptation strategy leads to a system efficiency loss of only about 5% considering the transparent forward link for the transparent return link. The analysis results indicate an acceptable loss of about 20% can be achieved.

    Furthermore, it has been demonstrated that the application of FMT to DVB-S forward and future RCS return link is supported by today's signalling. However, a versatile encapsulation of IP datagrams over the Generic Stream (GS) interface would offer a better exploitation of the improved physical layer capacity.

    Contacts

    Status date

    Friday, October 19, 2007 - 11:15