What is DVB-S2?
DVB-S2 (EN 302 307) is a digital satellite transmission system developed by the DVB Project. It makes use of the latest
modulation and coding techniques to deliver performance that approaches the theoretical limit for such systems. Satellite
transmission was the first area addressed by the DVB Project in 1993 and DVB standards form the basis of most satellite
DTV services around the world today, and therefore of most digital TV in general. DVB-S2 will not replace DVB-S in the
short or even the medium term, but makes possible the delivery of services that could never have been delivered using
DVB-S, and does so with a performance level that ensures that we won’t see a “DVB-S3” for a very long time, if ever!
The world’s first digital satellite TV services were launched in Thailand and South Africa at the end of 1994 and both used
the newly released DVB-S system. Over time it has become the most popular system for the delivery of digital satellite
television, with more than 100 million receivers now deployed around the world. Nonetheless, with the system being more
than ten years old, it is not surprising that the industry eventually decided the time was right to update. Thus DVB-S2
was developed, with the DVB Technical Module sub-group responsible for the work being chaired by Dr. Alberto Morello
of RAI. The work would take advantage of advanced techniques for channel coding, modulation and error correction to
create a system that would make a range of new services commercially viable for the first time, e.g., when combined with
the latest video compression technology, DVB-S2 would enable the widespread commercial launch of HDTV services.
How does it work?
The original DVB-S system, on which DVB-S2 is based, specifies the use of QPSK modulation along with various tools
for channel coding and error correction. Further additions were made with the emergence of DVB-DSNG (Digital Satellite
News Gathering), for example allowing the use of 8PSK and 16QAM modulation. DVB-S2 benefits from more recent
developments and has the following key technical characteristics:
• There are four modulation modes available, with QPSK and 8PSK intended for broadcast applications in nonlinear
satellite transponders driven close to saturation. 16APSK and 32APSK, requiring a higher level of C/N, are
mainly targeted at professional applications such as news gathering and interactive services.
• DVB-S2 uses a very powerful Forward Error Correction scheme (FEC), a key factor in allowing the achievement
of excellent performance in the presence of high levels of noise and interference. The FEC system is based on
concatenation of BCH (Bose-Chaudhuri-Hcquengham) with LDPC (Low Density Parity Check) inner coding.
• Adaptive Coding and Modulation (ACM) allows the transmission parameters to be changed on a frame by frame
basis depending on the particular conditions of the delivery path for each individual user. It is mainly targeted to
unicasting interactive services and to point-to-point professional applications.
• DVB-S2 offers optional backwards compatible modes that use hierarchical modulation to allow legacy DVB-S
receivers to continue to operate, whilst providing additional capacity and services to newer receivers.
How does it work? (continued)
DVB-S2 delivers excellent performance, coming close to the Shannon limit, the theoretical maximum information transfer
rate in a channel for a given noise level. It can operate at carrier-to-noise ratios from -2dB (i.e., below the noise floor)
with QPSK, through to +16dB using 32APSK. The table overleaf (Figure 1) shows the improvements in efficiency that
DVB-S2 delivers when compared to DVB-S with typical TV broadcast parameters, with gains in the useful bitrate of more
than 30% in each case.
Having been formally published as an ETSI standard in March 2005, DVB-S2 was quickly adopted by the industry for the
delivery of new services. In Europe and the USA a number of major satellite broadcasters use DVB-S2, in conjunction
with MPEG-4 advanced video coding, for the delivery of HDTV services (e.g., BSkyB in the UK and Ireland, Premiere in
Germany, Sky in Italy, DirecTV in the USA). DVB-S2 has also been deployed by DTH operators elsewhere in the Americas,
in Asia, the Middle East and Africa.
DVB-S2 has also been adopted for professional applications. The EBU’s Eurovision network, one of the world’s largest
contribution networks, has been fully upgraded from DVB-S to DVB-S2. Testing of the new systems in spring 2005
revealed a 20% increase in throughput, a result which encouraged the EBU to upgrade the network in time to distribute,
for example, the 2006 FIFA World Cup over DVB-S2.
Two significant factors will ensure that deployments of DVB-S2 will grow steadily in the coming years. Firstly, in August of
2006 the ITU’s (International Telecommunications Union) study group on satellite delivery issued a recommendation that
DVB-S2 alone be adapted as the preferred option for a “Digital Satellite Broadcasting System with Flexible Configuration
(Television, Sound and Data)” (ITU recommendation number BO.1784).
Secondly, late in 2006, an announcement from the holders of key DVB-S2 intellectual property rights indicated that
licensing costs for manufacturers of DVB-S2 equipment will not exceed $1.00 per consumer device, or $0.50 for quantities
exceeding 500,000. The certainty granted by this announcement is expected to foster the rapid adoption of DVB-S2 by
the global satellite broadcasting and telecommunications industries.