HDTV
and Internet Bandwidth Needs Served with Satellite Spot Beams
It was
about a hundred years ago that Marconi invented radio communications
(1902). By 1930, many homes in the
United States and Europe had an AM radio receiver. High Definition Television (HDTV), which needs a much larger
bandwidth for transmission, coupled with the current demand for hundreds of
television channels and the growth in Internet communications, is resulting in
a communications bandwidth shortage.
One tool being used to address this problem is Satellite SpotBeams. By 2010, 60% of TV receivers will use a
Satellite signal, up from 15% in 2002.
Until
recently, communication satellites transmitted with a very broad signal. The same signal that was received in the
California was from the same source as the signal that was received in New
York. Satellites that are not "SpotBeams" send out a signal over very
large areas, transmitting data across the USA.
SpotBeams
are different. It is similar to a
searchlight focused on one area of the country. A typical SpotBeams has a
radius of only 50-100 miles. Depending
on where you are in the country, you won't detect the beam unless you are in
the focus. With this tool, the same
frequency spectrum can be used with different source material, in different
regions. In addition, the system is
flexible enough to increase power on specific transmissions when needed to
compensate for local weather conditions.
SpotBeam technology is ideal for the transmission of video requiring
ultra high bit rates such as HDTV.
DirecTV
and DISH Network were one of the first to use SpotBeams. The transmission of local TV channels is
ideal since a signal focused on an area was a perfect fit for the
application. The SpotBeam technology is
being applied on newer satellites using the Ka Band (Ka band is 19-30
GHz). There are several Ka band
satellites in use that do not use SpotBeams: Advanced Communication Technology
System (NASA USA), Superbird and N-STAR (Japan), HOT BIRD 6 (Eutelsat, France),
DFS Kopernikus (Germany), and Italsat (Italy), but the newer, more advanced
satellites are using SpotBeam technology.
HDTV
SpotBeams used by DirecTV and DISH Network (Ka-band) are often narrower in
focus than the Ku band SpotBeams used for Standard Definition TV. If you live more than 50 miles from the
signal center in a populated region, it is possible that you will not be able
to receive the HDTV SpotBeams. DirecTV
and DISH Network have the technical capability of transmitting a broad SpotBeam
signal, especially since the newer Satellites can operate at a higher
power. It makes good business sense for
them to maximize coverage, but there are tradeoffs.
In
a rural state like New Mexico, it makes sense to have the SpotBeams cover a
200-mile radius, because that enables more subscribers which results into more
revenue. In New England it sometimes makes sense to focus the signal more
narrowly, since the SpotBeams are more densely packed together. However, since
different frequencies are used for adjacent SpotBeams, overlap usually can be managed.
According
to Northern Sky Research, there are 15 million U.S. households without access
to broadband Internet service. SpotBeam
satellites operated by WildBlue and Telesat have already reached over 300,000
Internet subscribers since their launch in 2005.
One
advantage of Ka band is that it requires a smaller dish to offer very good
performance. Ka band using SpotBeams is more efficient than a traditional C or
Ku band satellites (the technology used by the other communication satellite
systems). The service is able to
deliver significant improvements in performance. A Ka band satellite can provide as much as an 8X increase in
capacity over Ku band satellites. The
technology can provide upload speeds as fast as 16 Mbps and download speed as
fast as 30 Mbps. Three Ka band
satellites with SpotBeam technology are already in service in North America:
Telesat Canada's Anik F2, WildBlue Communications Wildblue 1, and Hughes
Network Systems SPACEWAY 3.
A
fourth North American satellite, ViaSat-1 (another Telesat Canada satellite) is
planned for launch in 2011. This system
is a very advanced Ka-band broadband satellite ordered by ViaSat. The amount of bandwidth enabled by ViaSat-1,
equipped with ViaSat's "SurfBeam" networking system, is unparalleled.
Total throughput is designed to be over 100 Gigabits per second, which is more
capacity than the current North American fleet of two-way Ka, C and Ku band
combined capacity. In 2010, Ka-Sat will launch a satellite to provide similar
service in Europe.
HDTV
signals require 4-5 times as much bandwidth for transmission as standard
definition signals, even with sophisticated MPEG-4 encoding. In addition, our Internet communications
bandwidth requirements continue to grow at about 50% annually. Keeping up with
the demand will require a smorgasbord of options, and Satellite SpotBeams (Ka
band), will be very important in the mix.
About
the Author:
Brian Bradshaw is a Certified Technical Specialist (InfoComm CTS). Areas of expertise include Video, HDTV, Audio, Computation, Satellite Systems, and Communications. More information can be found at his Website: http://bradshaw-vacuum-technology.com/