Copyright © 2006 – STM Norway AS
Publication no. 101557, Rev. T, November 3
th
, 2006
Page 56
14. STM SatLink and DVB-S2
The DVB-S standard is currently the most widely used transmission standard within the satellite
communications field. When it was introduced in 1994 it represented state-of-the-art with respect to
bandwidth and power efficiency. The key elements in the DVB-S standard were the use of QPSK
modulation and concatenated Reed-Solomon / Viterbi coding for FEC protection of user data.
Recent advances in the field of digital coding and modulation techniques have made possible a
technology upgrade of the DVB-S standard – known as the DVB-S2 standard. In the DVB-S2 standard
there are primarily 3 features that directly translate to improved performance:
•
Modulation – support both QPSK and 8-PSK
•
Coding – LDPC-BCH with performance close to Shannon bound
•
Reduced carrier roll-off
There are several ways the benefits of DVB-S2 can be realised. This will vary from system to system and
is dependent on several factors such as satellite performance, link characteristics, RF equipment etc.
For a power limited transponder, DVB-S2 offers the possibility to push 30 % more user bits through the
channel while maintaining the same link quality and transmit power.
For a bandwidth limited transponder the potential to save bandwidth is even bigger, as transmit power can
be increased allowing higher FEC rates and/or moving from QPSK to 8-PSK modulation. In such
scenarios bandwidth savings can approach 50 %.
But there are other ways to gain from DVB-S2 as well. With the improved coding performance of DVB-
S2 the satellite coverage area may be greatly expanded. As an example, consider the satellite coverage
map below. With DVB-S2 one can tolerate 2 dB lower transmit EIRP from the satellite, which translates
into a very significant expansion of territory covered by the service. This enables new markets and
customers to be addressed without the need for setting up additional teleports or having to use multiple
satellites to obtain the desired coverage area.
Figure 3: Sample satellite coverage area
