Novel ground components prototype beyond DVB-S2 for broadband satellite networks

Title: NOVEL - Novel ground components prototype beyond DVB-S2 for broadband satellite networks
Funding source: ESA - European Space Agency
Partners: VTT Technical Research Centre of Finland (Prime), Bittium Wireless
Principal investigator: Dr. Bhavani Shankar
Researchers:  Dr. Nicolò Mazzali

The DVB-S2 standard [1] developed by the DVB Project in 2003 and ratified by ETSI in 2005 has been the cornerstone of satellite communication standards forming the basis of digital satellite television transmission across the globe. Based on a number of refinements and innovations over the DVB-S2, the extended standard (which includes sharper roll-offs, MODCOD upgrades, very-low signal-to-noise ratio (SNR) paradigm, and super-framing structure) has been formalized in [2] under the name of DVB-S2X. This standard represents the state-of-the-art of broadband satellite waveforms and the starting point of this project. The original target of the ESA projectNovel Ground Components Prototype beyond DVB-S2 for Broadband Satellite Networks(NOVEL) was to improve the S2X waveform by resorting to new advanced techniques.

However, DVB-S2X performance had already been optimized in a number of previous activities, and the gain stemming from the possible study of new techniques was limited. Nevertheless, new applications and scenarios were identified where such techniques could be beneficial. In particular, it is proposed that the DVB-S2X can be a common technology enabler not only for VSAT but also for land mobile (LMSS), maritime mobile (MMSS) and aeronautical mobile satellite services (AMSS). From technical point of view, a special attention is given to signal predistortion and to develop, implement and verify a robust synchronization at very low signal-to-noise ratio.

The NOVEL project is divided into 2 Phases:

• Phase 1 aims at defining new potential use cases and to studying new techniques in various scenarios. The work comprises a “state-of-the-art review” type of work in order to identify the relevant techniques and select only the most promising ones, as well as computer simulations aiming at evaluating the performance of the selected techniques. Based on the simulation results, conclusions are made and the algorithms and the techniques to be implemented in a hardware test-bed are selected.
• Phase 2 carries out the detailed design, implementation, and integration of the selected techniques, as well as a hardware test-bed development. Phase 2 ends with an extensive measurement campaign, in which the selected techniques are emulated in a real radio channel and hardware in laboratory environment.

Objectives

The objective of this project is to design a hardware demonstrator providing a reference design based on the DVB-S2X standard suitable for emerging markets. To this purpose, relevant fixed and mobile scenarios (i.e., fixed VSAT, land mobile, maritime, and aeronautical services) have been identified. Also, advanced physical layer techniques have been investigated in order to deal with the peculiarities of the chosen scenarios and guarantee reliable communications even in very low signal-to-noise ratio (SNR) regime. In particular, the superframing structure provided by the DVB-S2X standard was adopted (namely, superframing format 3), and used as key element for the following designs:

• a hardware-friendly signal predistortion algorithm was designed based on look-up tables in order to compensate for the nonlinear distortion introduced by the satellite amplifier;
• a self-synchronizing channel interleaver was tailored to cope with the challenging fading affecting the mobile environments;
• a robust hardware-friendly synchronization chain was designed and finely tuned to allow reliable communications at very low SNRs (e.g., -5 dB) and in presence of Doppler effects induced by mobility.

The final demonstrator design also includes all the realistic impairments affecting commercial equipment and the corresponding compensation algorithms, and was verified by means of software simulations and hardware measurements.  

Outcomes

In general, NOVEL project proposes that the DVB-S2X can be a common technology enabler for different mobile scenarios like land-mobile, aero and maritime in addition to VSAT. Highlighting the applicability to emerging scenarios, PHY layer techniques were investigated, and it was shown that the SPD could provide a gain up to 1.5 dB. A special attention was given to develop, implement, and verify a robust synchronization at low SNR, and experimental measurements show that at least timing drift of 100 ppm can be tolerated. A HW testbed incorporating selected PHY techniques with DVB-S2X framing was devised and the functionality of HW testbed has been validated by comparing the measured performance with the SW simulations. The potential of the DVB-S2X waveform for maritime communications was shown with HW measurements and SW results indicate a significant interleaver gain for mobile scenarios.

In detail, one of the target of the project was to demonstrate the DVB-S2X waveform down to -5 dB SNR.  The super-frame format #3 using short FEC frames was selected to carry the task. Format #3 has a constant length, and the extra pilots provided by the super-framing can be exploited to improve the synchronization. Both the SW simulation and the HW testing campaigns prove that communication at low SNR is feasible with this approach.

The other important goal in the project was to test DVB-S2X waveform in mobile satellite systems. The constant length of the super-frame #3 helps maintaining the synchronization over deep fading and shadowing, characteristic of some mobile scenarios. A long convolutional interleaver is needed to help FEC to recover data from deep fades. SW simulations show that the convolutional interleaver prevents FER curves from saturation in the LMSS cases. Additional MMSS cases were also run with the HW test bed, and the results show it can be assumed that the convolutional interleaver would also help the performance in maritime satellite environment.

Project Partners : SnT, University of Luxembourg, Luxembourg, VTT, Finland, Bittium Wireless, Finland 

Funding Source : European Space Agency (ARTES 5.1)

Project Duration: 05/2014 to 03/2017

Project Team:

Project Manager: Dr. Bhavani Shankar,

Research Team:  Dr. Nicolò Mazzali

Contact: 

Dr. Bhavani Shankar 

Research Scientist

Interdisciplinary Centre for Security, Reliability and Trust (SnT)

29, avenue J.F.Kennedy

L-1855, Luxembourg

Website: 

Website