02-03 - TELE-satellite International Magazine

FEATURE
ABS-S: a competition
for DVB-S/S2?
Jacek Pawlowski
The launch of
ZhongXing-9
(ChinaSat-9)
Photo: Xinhua
ZX 9 (Chinasat 9)
Photo: Thales Alenia Space
New Digital Standard
When we were reading a press release about the launch
of ZhongXing-9 (ChinaSat-9), it looked like something
quite routine. It was nothing out of ordinary that China
had another DTH satellite in service. It was the coding
and modulation this satellite was supposed to use that
surprised us. It was neither DVB-S nor DVB-S2. It was
something brand new: ABS-S (Advanced Broadcast
System-Satellite).
We all know that the standardization
is a very useful practice. However, it
happens really rarely that one thing is
accepted all over the world. For example
analog TV had always a few standards in
different regions of the world (PAL, NTCS,
SECAM, D2-MAC). Digital TV is no exception.
Of course, our readers are very
familiar with DVB-S and DVB-S2 standards
but these are not the only ones in
use. There is also the DSS (DirectTV) in
18 TELE-satellite & Broadband — 02-03/2009 — www.TELE-satellite.com
North and South Americas and ISDB-S
in Japan. They are similar to DVB but not
identical. A receiver capable of receiving
one standard is useless for the other.
And now, China decided to establish the
forth standard: ABS-S.
Why create yet another standard? One
obvious reason is evading the expensive
license fees. For example, every
receiver manufacturer has to pay a royalty
to MPEG organization for every unit
sold. Taking into account the population
of China, the amount of money involved
is huge. We are speaking of 400 million
households! China administration started
a program called “Every Village” aimed
at making digital satellite TV available
to a large percentage of country population.
This means that a receivers must
be really cheap.
It all started back in June 2002 when
the Chinese AVS standard has been
published. AVS stands for Audio Video
coding Standard. AVS compared to
MPEG has some advantages. It has twice
or three times the coding efficiency of
the traditional MPEG-2 - so it is closer
to H.264 (popularly called MPEG-4).
However, the complexity of algorithms
is lower than that of H.264. Thanks to
that AVS requires less memory and
occupies lower bandwidth. While H.264
is the video encoding standard only, the
AVS deals with video, audio and media
right management altogether. So it is a
complete industry system for coding the
source data.
ABS-S goes one step further. Similarly
to DVB-S2 which is based on H.264
and MPEG-2, the ABS-S is based on AVS
standard. ABS-S has bandwidth efficiency
similar to that of DVB-S2 (ca. 30%
more data can be sent compared with
DVB-S in the same transmission channel).
DVB-S2 efficiency is already close
to the theoretical limit (Shannon limit)
and apparently so is ABS-S. At the same
time ABS-S is regarded as simpler from
the technical point of view. This gives a
better chance that a higher number of
IC manufacturers can master this technology
in relatively short time. DVB-S2
and H.264 are rather complex and not
too many IC manufacturers offer compatible
chips.
For example, ABS-S does not use BCH
code, it can seamlessly combine fixedrate
modulation (CCM), variable bit-rate
modulation (VCM) and adaptive coding
modulation (ACM). It uses forward error
coding where it is difficult to implement
LDPC (low density parity check) and
depending on application one can use
different rate in 4 modulation modes:
QPSK, 8PSK, 16APSK, 32APSK. There
are more differences between ABS-S and
DVB-S2 but they are all understandable
only for the high-tech professionals.
At the moment, we do not have a
credible independent assessment of the
new standard. Will it be really almost as
good as DVB-S2 while being cheaper and
simpler to use and as Chinese sources
claim? When we have such opportunity,
we will perform such a test for you.
It can be interesting to watch what the
world IC maker will do. Will they ignore
the new standard and let the Chinese
manufacturers monopolize the China
market, or they will fight to offer their
own implementation of ABS-S/AVS compatible
chips? Will it be possible to create
a universal chip suitable for both standards:
DVB-S2 and ABS-S?