DVB-S2 is a second generation modulation and coding standard for Digital
Video Broadcast over satellite. Standard number EN 302 307 was released in
2004 and is the first new satellite transmission standard since the DVB-S
universal framework for transmission of MPEG-2-based digital television
services was adopted in 1994.
How does DVB-S2 differ from DVB-S?
The DVB-S2 standard enables delivery of significantly higher throughput in a
given satellite transponder bandwidth than DVB-S. It also supports a much
wider variety of input data formats, including multiple transport streams,
generic data formats and more.
Why was DVB-S2 created?
Using traditional standards, even premium subscription fees cannot support
the satellite costs associated with HDTV’s bandwidth requirements. A new
standard was needed to maximize bandwidth usage efficiency and ensure
operator profitability.
What benefits does DVB-S2 offer for network
operators and broadcasters?
Much higher rates of channel efficiency than past standards are enabled
by new channel coding schemes. Together with higher order modulation, this
increases satellite transponder throughput by about 30% at a given
transponder bandwidth and transmitted EIRP relative to DVB-S/DVB-DSNG.
Differential error protection and modulation for service components or
transport streams (e.g. SDTV, HDTV, audio, multimedia) are made possible
by Variable Coding and Modulation (VCM). This further enhances bandwidth
efficiency while maintaining desired quality.
Satellite capacity for interactive and point-to-point applications may be
increased by 100%-200% by combining VCM functionality with the use of a
return channels to achieve closed-loop Adaptive Coding and Modulation
(ACM). ACM improves channel protection and dynamic link adaptation
capabilities and may potentially reduce service provisioning costs
substantially.
In areas with variable receiving capabilities or conditions, DVB-S2 can
improve transmission quality substantially. Adaptive Coding and
Modulation (ACM) varies the level of channel protection and modulation on an
individual transport stream level, with dynamic adjustment to environmental
conditions.
A wide range of formats may be simultaneously transmitted on the same
transport medium. Supported input data formats include continuous bit-
streams, single or multiple MPEG transport streams and IP as well as ATM
packets. This represents a substantial improvement over DVB-S and DVB-
DSNG, which support only MPEG transport streams. To a great extent, this
future-proofs DVB-S2.
Will DVB-S2 lower our bandwidth costs?
Yes! With DVB-S2 30% more content can be transported using the same
bandwidth, for the same cost. Or the same content can be transmitted using
30% less bandwidth, for cost savings of 30%. Either way, network operators
and broadcasters benefit.
DVB-S2’s higher power efficiency results in additional savings. DVB-S2
signals require an average of 2.5 dB less link margin than a DVB-S signal
with the same error protection overhead. This means smaller antennas, less
unlink power and/or cheaper satellites.
Will DVB-S2 enable transmission of higher
quality video?
Broadcasters may choose to utilize the bandwidth capacity freed by the
switch from DVB-S to DVB-S2 to increase the forward error correction (FEC)
rate for improved quality. DVB-S2 enables the broadcaster to choose among
a wide range of alternative transmission modes that combine bandwidth
saving and improvement in picture quality.
Are proprietary coding solutions necessary to
get the most out of DVB-S2?
Not at all! DVB-S2 is an open standard, so superior performance does not
depend on proprietary coding solutions.
What input formats can DVB-S2 transmit?
MPEG-2, MPEG-4 and HDTV transport streams, as well as data streams
comprised of IP packets and ATM cells.
What modulation schemes are supported by
DVB-S2?
DVB-S2 supports a wide range of modulation schemes, including QPSK (2
bits/symbol), 8PSK (3 bits/symbol), 16APSK (4 bits/symbol) and 32APSK (5
bits/symbol). These APSK modulation schemes provide superior
compensation for transponder non-linearities than QAM.
What network equipment is necessary to
broadcasting with the DVB-S2 standard?
At the transmission site, a DVB-S2 modulator – either standalone or
integrated in an encoder - is needed to modulate the content. Terrestrial and
cable headends must be equipped with DVB-S2 receivers, while DVB-S2 set-
top boxes are required for DBS subscribers.
Is gradual migration to DVB-S2 possible or must
the transition take place all at once?
DVB-S2 provides both backward-compatible and non-backward compatible
modes. The backward-compatible mode allows legacy DVB-S receivers to
decode a portion of the transmitted bouquet and new DVB-S2 receivers to
decode the entire bouquet. It provides somewhat lower bandwidth savings
than the non-backward-compatible mode, but enables DTH operators to
distribute the capital and labor expense associated with replacement of the
installed base of set-top-boxes over a longer period.
Direct transition to non-backward-compatible mode is most suitable for
contribution solutions and distribution to terrestrial, cable and satellite
Headends.
A number of video network equipment providers have developed
encoder/modulators and receivers that simultaneously support DVB-S and
DVB-S2. These devices are ideal for systems that are in the process of
migrating to DVB-S2.
Is DVB-S2 suitable for DSNG applications?
DSNG applications benefit from the lower bandwidth requirements of DVB-S2
as well as from its superior link resilience. DVB-S2 advantages that are
particularly critical for DSNG include narrower frequency slots for identical
service bit rates or higher bit rates for the same frequency allocation; point-to-
point or point-to-multipoint transmission; increased availability; and reduced
uplink power requirements.
What is the difference between DVB-S2’s DSNG
professional mode and its broadcast mode?
The broadcast services mode of DVB-S2 is most suitable for Direct-to-Home
(DTH) services, collective antenna systems and cable television headends. It
supports only QPSK and 8PSK modulations and does not make use of very
low FEC rates that are targeted to extremely difficult professional reception
conditions. It supports constant coding and modulation (CCM) for
transmission. Variable coding and modulation (VCM) may be applied to
multiple transport streams requiring differentiated error protection for different
services.
The digital satellite news gathering (DSNG) mode of DVB-S2 is optimized for
point-to-point and point-to-multipoint applications. It is targeted for low symbol
rate, narrow band signals of usually less than 5 MHz. In order to transmit high
quality video content with relative high bit rates in a low symbol rate, 16APSK
and 32APSK modulations may be used together with synchronization pilots.
16K short FEC blocks, in addition to the 64K normal FEC blocks in the
broadcast profile, may be used for low latency in the channel. In order to
maintain reliable signal reception even in bad weather conditions and using
small up-link dishes mounted on a DSNG truck, very low FEC rates may be
used.
