The main objective of the DVB-S2 Satellite Experiment project is to perform an in-depth verification and optimisation by satellite of the many new features present in the DVB-S2 standard, such as high order modulations, enhanced coding and ACM, through extensive test campaigns consisting of field trials and measurements.
The project consortium, led by the satellite manufacturer Astrium Satellites, includes the participation of operators (Eutelsat and Telesat) and other partners involved in satellite telecommunications (DLR, Fraunhofer IIS and Nera).
Three platforms corresponding to the main profiles of the DVB-S2 standard - broadcast, interactive and professional - are set up to achieve the following objectives:
- Demonstrate that the new features of the DVB-S2 standard are functionally working by satellite for a large number of configurations and applications.
- Perform a campaign of satellite experiments with C-band, Ku-band and Ka-band transponders, focussed on the performance aspects, to assess in particular the gain of efficiency and availability brought by the new standard with advanced modulation schemes, LDPC/BCH coding and ACM adaptation.
- Measure the performance of commercial DVB-S2 broadcast equipment combined with SD/HDTV programmes and advanced video compression techniques like MPEG-4 H.264 / AVC.
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| ||Illustration: Performance comparison of DVB-S2 modulations with respect to DVB-S and DVB-DSNG (required C/N versus spectrum efficiency). Source: ?DVB-S2 - ready for lift off?, EBU Technical Review October 2004 article from Alberto Morello and Vittoria Mignone. |
The detailed list of experiments has been defined to get the most consistent and valuable feedback for the verification of the new features of the DVB-S2 standard. Taking into account outcomes from previous analysis, simulations and studies, as well as operators experience feedback and perspectives on DVB-S2, the main test areas are:
- Audio / video encoding techniques for broadcast services (SDTV/HDTV, MPEG-2/MPEG-4, etc.),
- Performance of applications with DVB-S2+ACM, ACM loop performance, comparison between CCM, VCM and ACM,
- Impact of satellite non-linearities (with / without pre-compensation) and transponder and spectrum settings to maximise the useful bit rate transmitted,
- Tests with interferer sources,
- Demodulator performance (acquisition, QEF, BER/FER vs. SNIR, etc.),
- Impact of phase noise sources with / without pilot symbols (high order modulation, low SNR, etc.),
- Impact of frame size and frequency offset.
The three test platforms are based on the DVB-S2 end-to-end communication chains that include gateway hubs and user equipment (receivers, set-top boxes), and the operator's space and ground segments. Loop-back configurations allow switching to the lab environment with channel simulators. Test conduction, monitoring and control is automated, results are computed by post-processing tools.
The project is organised in two phases:
- Phase 1 activities are focused on the definition of the experiments on the three profiles. The space and ground segment and other test equipment are specified in detail together with the link budgets.
- Phase 2 is dedicated to the platforms' development, integration in labs and with the space segment in the operators? premises. Each test campaign by satellite lasts for 3 months. Results are reported and published in several dissemination documents, including a feedback to the standardisation group and an article for a conference.
The experiments assess and provide results on the critical aspects of the operation of DVB-S2 by satellite in terms of functional behaviour and performance. The key topics are:
- Performance of DVB-S2 with HDTV channels in broadcast mode, compared to equivalent DVB-S applications,
- Performance of high order modulations (16-APSK and 32-APSK) and new LDPC coding rates (1/4 to 9/10) in satellite conditions,
- Gain obtained with ACM together with Ku-band and Ka-band fading (both emulated and real attenuation), compared to CCM and VCM modes,
- Acquisition threshold and performance of set-top boxes and professional equipment,
- Performance when satellite transponder is closed to saturation point, without and with pre-distortion techniques.
The results to be published will provide a valuable feedback of DVB-S2 satellite operations in a large number of configurations (C/Ku/Ka-bands, mono/multi-beam, linear/non-linear transponders, several phase noise and interference conditions) and with a large panel of equipment (prototypes, professional equipment and set-top boxes).
The outcome of the experiments will concern primarily the operators wishing to move to DVB-S2 for their applications (HDTV, interactive and professional services, etc.), and looking for operational results with the new standard. The experiment's feedback should also be interesting for standardisation groups, space agencies and institutions, academics and equipment manufacturers working on the DVB-S2 subject.
The following theoretical performance gains are expected to be obtained in real satellite operation:
- DVB-S2 compared to DVB-S: a gain of approximately 30% of bandwidth,
- ACM efficiency: 50 to 200% gain compared to CCM depending on the test conditions.
Phase 1 has been completed successfully, with the detailed definition of the experiments, the test-bed equipment and space and ground segments.
In phase 2, the development, procurement and integration of the test-bed platforms are mostly completed. The project now concentrates on the test campaigns in lab and by satellite:
- Broadcast profile: most of the broadcast profile DVB-S2 tests using a satellite simulator and over the Anik satellite have been completed. The focus of current efforts is use of non linear pre-compensation tests of high-order modulation at 16APSK and 32APSK operation at near transponder saturation levels.
- Interactive profile: the first part of the test campaign, completed in the first quarter of 2008, assessed the performance of prototype equipment supporting DVB-S2 + ACM features using Anik F2 Ka-band satellite. The second and final part of test campaign will use commercial grade equipment with advanced Quality of Service traffic shaping device controlled by the network management system upgraded for ACM operation. Integration is on-going on this second phase.
- Professional profile: after a successful test-bed acceptance review at Eutelsat teleport in Rambouillet, the test campaign has been performed on Atlantic Bird 3 satellite. Test results are being analysed and reported.
Last Update: 06 Feb 2013