High-throughput Satellite Communication

DVB-S2X Technology

Satellite communication is a multi-billion market, with dozens of satellites being launched each year, providing terabytes of capacity worldwide. Despite the growth of alternative and competing terrestrial and wireless solutions, satellite continues being a must-have for areas not or just barely connected and shows its full economic potential in supporting one-to-many connectivity.

DVB-S2 is the de-facto standard being used in direct-to-home (DTH) satellite TV distribution. DVB-S2 is also widely adopted in satellite broadband (»satellite internet«) for the user downlink and in many interactive or professional peer-to-peer networks. Compared to DVB-S2 developed and specified in the early 2000s, DVB-S2X is a state-of-the-art, backwards-compatible extension and superset, providing higher spectral efficiencies and new features to enable or promote new applications.

Fraunhofer IIS was actively involved in the development, specification and validation of DVB-S2X. The subsequent section provides further insight into

  • how DVB-S2X differs from and extends DVB-S2;
  • key additional features in DVB-S2X and their implication on performance and for new applications; and
  • DVB-S2X technology and IP available at Fraunhofer IIS for specific markets.

Why satellite communication? Why DVB-S2X?

Satellite communication can be anything from a tiny communication link into the middle of nowhere to the backbone technology of direct-to-home (DTH) TV broadcast. Compared to competing technology, satellite communication has a unique advantage in several domains:

  • Alternative infrastructure is technically not feasible
    This includes applications like in-flight entertainment, in-flight internet connectivity or maritime services: It just isn’t an option using cable, fiber or backhaul connected wireless technology in or over the middle of an ocean.
  • Alternative infrastructure is not deployed
    This includes scenarios where connectivity is urgently needed but conventional infrastructure has not yet reached the area – or where the connectivity need is temporal and too short to upgrade alternatives. This is specific for »on the move« scenarios, including, but not limited to the military domain (MILCOM). This also includes time-limited backhauling for mobile phone networks spreading out into rural areas or news and data gathering applications with instantaneous demand.
  • Satellite having the superior total cost of ownership
    Application examples include remote sites connectivity using dedicated satellite links and satellite broadband – providing internet access to end-user premises in rural or remote areas. In this case satellite per se may not be the cheapest or best technical option, but any alternative infrastructure is eliminated by prohibitive investment cost for each individual site.
  • One-to-many connectivity
    A single TV or radio broadcast satellite may easily provide content and data to 100 millions of users. Compared to competitive technologies that physically or wirelessly connect each individual user, satellite broadcast allows an unlimited number of users being reached with no per-user infrastructure cost penalty.

In brief, the improvements in DVB-S2X address the above opportunities as follows:

  • Improved performance and spectral efficiency, squeezing more sellable capacity out of the same amount of spectrum, or, vice versa, providing lower cost per bit
  • Additional features, allowing more robust communication and enabling new applications and use cases

In this context, DVB-S2X should be seen as a tool-box, with certain tools addressing certain challenges and opportunities and where each implementer is free to pick the subset that is believed to be best suited for an application or market, but also to differentiate a DVB-S2X product from the competition.

Implementation details

DVB-S2X is an extension of the DVB-S2 specification. Any DVB-S2X receiver is backwards compatible with DVB-S2, but legacy DVB-S2 receivers are not required being forward compatible. Thus legacy DVB-S2 receivers will not decode transmissions using new DVB-S2X features.

Some features are transparent to DVB-S2 receivers, thus DTH transmissions may be constructed to be usable for both DVB-S2 and DVB-S2X receivers, with only the latter making use of the additional capabilities. On the long run, once DVB-S2X DTH receivers have reached sufficient market penetration, broadcasters are expected to pool attractive content in DVB-S2X-only channels, cutting down the legacy DVB-S2 offer – similar to the transformation from DVB-S to DVB-S2 at the beginning of the high-definition TV era.

A plurality of the technical improvements in DVB-S2X is focused on improving performance and spectral efficiency, both in the physical layer (PHY) and on system level:

 

IMPROVEMENTS BENEFITS AND APPLICATIONS
Increased granularity in modulation and coding (MODCODs) Reduces unnecessary margins in DTH and broadband applications
Pulse shaping with sharper roll-off filters Resulting in capacity gains for most applications from better utilizing the available spectrum
Higher modulation schemes up to 256APSK Extended range is beneficial for broadband applications on modern high-throughput satellites (HTS) and for professional equipment using high gain ground antennas
MODCODs optimized for linear transponder, operated in multi-carrier mode with appropriate back-off Typical use case for the return link in broadband or for remote site or backhaul connectivity on bandwidth-lease transponders
Support for ultra-wideband carrier Feature is predominately designed for DTH and broadband applications – use cases with enough throughput filling entire transponders
Channel bonding A system-level feature beneficial for DTH on fragmented transponder
Co-channel interference mitigation Applicable in DTH receivers and on HTS satellites used for broadband
Improved multiplexing gain Reduces the overhead reserved for temporal peak capacity demands on wideband carrier and on channel bonded transponders

Besides performance improvements, DVB-S2X also adds a number of physical layer and system level features for new use cases or for improving the robustness in existing applications, including very low signal-to-noise ratio (VL-SNR) operation and introduction of a low-overhead super-frame structure. Super-framing allows for new transmission techniques like precoding and beam hopping.

Deciding on the supported feature set

Implementing the DVB-S2X standard may be complicated by the variety of different target applications and services and the richness in features – normative, optional or not applicable, depending on target application and service. Implementing DVB-S2X is further complicated by the wide throughput range a receiver may have to cover – less than 100 Mbps on a traditional satellite using 36 MHz transponder to in excess of 2000 Mbps on a 500 MHz transponder operated under high SNR conditions. Moreover the required receiver resources grow more than linear with carrier bandwidth and throughput.

Therefore, a receiver manufacturer not only has to decide on the supported feature set to be implemented and tested, but also on the trade-off between throughput, complexity and price of the silicon and implementation loss, e.g. resulting from efficient but limited accurate symbol demapping or from limiting the number of iterations in the LDPC decoding process. Clearly there is no one-size-fits-all solution, and a highly cost sensitive DTH receiver will be quite different from a professional high-end and high-throughput MODEM.

DVB-S2X: Be smart, get it right and get it done

Thorough understanding of DVB-S2X technology, the market needs and the constraints of the target application is vital for the right selection of the features and for building a unique and successful product. Thus, as an equipment or chipset manufacturer, benefit from Fraunhofer IIS’ background and know-how when evaluating DVB-S2X as an extension to your product portfolio and when drafting the product’s DVB-S2X features and capabilities in detail.

Implementing DVB-S2X easily consumes person-years of effort, not even counting functional validation and fine tuning the decoder performance. Adoption of a validated and field tested implementation minimizes technical and schedule risks. Contact us for an evaluation of a field tested FPGA receiver implementation and to discuss customizations and porting to alternative platforms and technologies.

Time-to-market is essential staying ahead of competition and for timely return of investment. Fraunhofer IIS offers a readily available DVB-S2X receiver implementation using Annex E, format 4 (super-framing) that can be quickly tailored for different products and throughput ranges. Different licensing options are available on request.