European Space Agency

DSL in the Sky


Thales Alenia Space started developing its DVB-RCS satcom solution in 1999. The first generation of product featured a DVB-S forward link and RCS return link. It has been deployed commercially since 2003. This development was supported by ESA through the DOMINO 2 and Dionisos 2 programmes. The evolution of the DVB-RCS, making way to the new DVB-S2 standard early understanding and implementation, started under the DOMINO 2 umbrella. This new waveform resulted in a drastic improvement of satellite communication spectrum efficiency.

The objective of the DSL in the Sky project has been to develop the new generation of Satcom solution, implementing the fully updated DVB-RCS / DVB-S2 standard, including advanced features such as Adaptative Coding & Modulation (ACM), Dynamic Rate Adjustment (DRA), or Satlabs QoS. The target development approach focused on high integration and flexibility.

Another ambition of DSL in the Sky was to build a truly interoperable solution. To this purpose, the DSL in the Sky programme, complemented by national validation initiative, was built to work with terminals from different suppliers.

Yet, in order to make sure of the availability of a terminal implementing all advanced features such as ACM, the programme included a full terminal development activity. ACM allows to increase drastically the system capacity, taking into account the specific situation and transmission conditions of each user.

This second major release (hence R2) of the A9780 (DSL in the Sky product number), bringing drastically better spectrum efficiency, targeted a fairly ambitious market position. Commercial targets initially included a wide range of segment: professional, as well as prosumer and consumer markets. The focus is now more on professional and high end areas, including defence and governmental systems and solutions.


Technical issues: A major challenge was to build a forward link matching the complexity of the new DVB-S2 standard: flexibility in coding, modulation, rates, all processing being done fast enough, on high performance but reasonable cost machines.

The development of the terminal faced the use of the first 2 ways ACM capable chipset (ST 900). More globally, the development of a new satcom solution, reaching the market in time, with high flexibility and modularity, capable to release early product delivery, has been an industrial and organisational challenge. The Satcom R2 solution is a software intensive product, with high versatility potential.


DSL in the Sky has resulted in the development of the Satcom product line portfolio, adding a world class level range of solution. They are specially well fitted to high added value (“vertical” ) markets such as:

  • SME
  • Corporate sector
  • Public Sector / governmental networks,
  • Security& Defence
  • Communication with mobile vehicles “DSL on the Move”
  • Backhauling

DSL in the Sky can be deployed economically in a very scalable mode, starting with networks in the range of #100, up to several thousands. Its versatile range of terminal can match a variety of prices and features configuration. 

DSL in the Sky (R2) is deployed commercially. Major defence programmes have selected the DSL Thales Alenia Space product for their ground infrastructure (Yahsat, Syracuse). The solution is well matched to fit into the Prosumer market, and shows a potential for Consumer market as well.


The DSL in the Sky architecture features a broadband two ways transmission solution over satellite. It uses a star topology, over transparent space segments. It is composed of a Hub, the central component of the system, connected to terrestrial networks, which handles the traffic with user terminals. It provides efficient satellite resource management.

Terminals logged on to the hub network provide interfaces for users to connect their equipment.

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Overall description of the system:

  • A single infrastructure with multi-service provider support, shared network, up to 2 beams and forward links,
  • Optimized bandwidth (all the power of DVB-RCS/DVB-S2 advanced features),
  • Optimized traffic management: high throughput, large range of data rates, QoS features,
  • Scalability: starting at a few hundreds (mini-hub), scalable to large networks,
  • Low operation costs.

Features (Standard Hub):

  • Forward link
    • DVB-S2 (QPSK, 8PSK): 2 to 45 Mbps
    • DVB-S (QPSK): 1 to 45 Mbps
    • MPE encapsulation
  • Return Link
    • DVB-RCS standard (BPSK, QPSK)
    • Distributed preamble to reach negative Es/No
    • Encapsulation: 1, 2 or 4 ATM Cell per traffic burst
    • Bandwidth; up to 102 MHz
    • Throughput: 128 kbps to 48 Mbps
    • Carrier bit rates 144 to 4096 kbps
    • Fast and slow frequency hopping
    • Automatic uplink power control, DRA
  • QoS: per application, per subscriber/application
  • Management:
    • Configuration Wizard, Import / Export capabilities
    • Remote management client
    • Terminal Software download

The terminals for DSL in the Sky include several model, each focusing on a specific market range:

  • Low cost entry version (typically SOHO):
    • Delivering 4Mbps total throughput, with limited network functions,
  • Small enterprise / Public sector version:
    • Can reach a 12Mbps total throughput ( 2Mbps upstream), supports higher level network features (simultaneous voice and data support),
  • High end for vertical markets (Security & Defence, Transport, Backhauling):
    • Features full DVB-S2 implementation (CCM and ACM), Extended QoS (Diffserv, Satlabs), 44Mbps total throughput ( 4Mbps upstream), Standard IP stacks, easy introduction of additional network features.


The DSL in the Sky “R2” project plan has been set-up by Thales Alenia Space with the following rationale:

  • Built upon the background experience and lessons learned from the first release deployed “R1” of DSL in the Sky, (in particular: management sub-system, QoS, operational requirements,…),
  • Taking the opportunity of a technical gap (DVB-S2) to introduce a more integrated product, based on an homogeneous hardware architecture (servers) and plug-in modules approach, resulting in a cost effective and flexible product line,
  • Leveraging on the Burst Mode Demodulator development project run by TAS Belgium, allowing to develop a full return link subsystem with leading edge performances, including high performance real-time encapsulation and resources management algorithms,
  • Addressing development of both hub and terminal, aiming from the start at a very ambitious feature set (full ACM included).

From these starting lines, TAS has gathered the following development team.

On the Hub side:

  • Alcatel-Lucent developed the Forward link Transmitter, a card to be plugged in the FLSS server,
  • TAS Belgium supplied BMD boards, and contributed to the development of the access control sub-system,
  • TAS France handled all the system design and the major part of the developments, as well as the whole subsystem and system integration, validation and certification.

On the terminal side:

  • Spacebridge lead FPGA based preliminary bread boarding of an ACM card,
  • Amesys was in charge of the terminal Modem, to be plugged into the SNT,
  • The server (Sat-IP Box) hosting all the management and network functions of the terminal a well as the modem board, was developed by TAS France,
  • TAS lead the whole terminal development, and ensured the whole integration, up to CE certification of the product.

Current status

The project started in 2004, and is now completed.

The pictures below show equipment resulting from the DSL in the Sky programme. It includes compact mini-hub (left), standard hub (easily scalable to large size networks), and samples of operating screens. Several types of terminal (3 suppliers) matching the DVB-RCS standard have been validated over the system.

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The gateway development was completed in 2008, while the SNT terminal development was completed in 2009. 60 hubs and 5000 terminals (of which 150 SNTs) were deployed as of 2010.


The product line was augmented, in parallel with the DSL project, with a capacitive return link solution (HDR, for High Data Rate), allowing to combine the RCS product architecture with 2-ways links, up to 40Mb/s.

Status date

Thursday, December 2, 2010 - 16:14