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. The world changed quite a bit in the 20th century. Courier 1B, (Philco), the first active communication satellite, was launched in 1960. We now faces new communication challenges. 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 communication 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.
What are Satellite SpotBeams?
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 SpotBeam 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.
Anik F2 (built by Boeing, and operated by Telesat) was launched on July 17, 2004, and began service on October 1. It is currently the world's largest communication satellite at 157 feet long and 27 feet wide. Anik F2 provides Internet service, distance learning, and telemedicine to the United States and Canada. Anik F2 has 45 transponders delivering broadband signals using Spotbeams. A third of the Spotbeams provide broadband services to Canada. The rest are used to provide Internet service to the U.S.
HDTV SpotBeams
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 SpotBeam. 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 SpotBeam 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.
SpotBeam Satellites and Two-Way Communications
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.
ViaSat-1 and Ka-Sat: Satellite Communications on Steroids
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, Audio, Computation, HDTV, Satellite Systems, and Communications. He has a communications technology business in Plano, Texas (Dallas). More information can be found at his Website: http://bradshaw-vacuum-technology.com
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