SATELL_ITE BROADBAND

11/2/2002

Satellite Broadband is a technology that allows high bandwidth digital communications via Earth satellites. Bandwidths advertised are comparable to those of DSL, wireless, and cable technologies -- 200-400Kbits per second downlink, about 10% of that uplink. Users report that the advertised rates are rarely achieved. Like cable, data rates may vary with the number of other users competing for bandwidth. Equipment costs range upward from several hundred US Dollars. Monthly costs are somewhat higher than competitive broadband options in the North America, but not outrageously so.

Satellite broadband uses Ku band signals in the frequency ranges used for satellite TV broadcasting. The same satellites are used, the hardware is compatible and some packages include TV service. North America has two satellite broadband services. Europe has nearly a dozen.

Satellite broadband requires an unobstructed view of the satellites that lie in synchronous orbits about 40,000km above the equator. They also require adequate signal strength from the satellites which have rather complex directional antennae designed to provide adequate signals to areas of perhaps half a continent. Isolated areas like Bermuda or Pitcairn Island are unlikely to be in the service pattern of the satellite antennae. The receiving antennae are similar to the "18 inch disk" often used for satellite TV. In many cases they are somewhat larger. They will require somewhat more precision in aiming. If a radio uplink is used to the satellite, "Professional" installation by a licensed technician will be required in many countries.

Older Satellite services required a separate telephone link for uplink. As of 2002, the two primary satellite TV providers in North America use over the air uplinking and do not need a phone link. Service is said to be generally reliable although it may have problems during periods of fog, snow, or heavy rain. Buildup of snow/ice on the antenna or amplifier unit can also cause difficulty. Some users also report occasional short unexplained outages.

Satellite broadband has two unique technical issues -- both related to the 250ms round trip delay for round trip communications with the satellite. 250ms is a minimum. Users report delays as long as 750ms. The first issue is that there is no way for users -- who can not monitor each other's transmissions -- to coordinate uplink signals amongst themselves. They must transmit uplink information blind hoping to avoid conflict with other users by chance. The second issue is that protocols that require a response from the receiver run extremely slowly via satellites. Benchmarks that depend on "instantaneous" turnaround (most broadband benchmarks apparently) do not work well with satellites. Voice over IP and interactive games are said to have problems with satellite links because of the time delay.

To get around the roundtrip delays that would otherwise slow TCP to a crawl, Satellite providers use "accelerator" technologies that break downloads into multiple streams. Unfortunately, these accelerated streams use proprietary protocols that are not compatible with the routers used for cable/dsl. To get reasonable data rates, it may be necessary to use the communication terminal technology and software provided by the vendor. The two current North American vendors support only Windows based solutions. DirecPC does not seem to support networked users. Starband does, but with restrictions that are not entirely clear. It is possible that non-proprietary accelerator technologies such as Aria (Linux) or Flashget (Windows) may work and may allow non-proprietary interfacing.

Although there are only two satellite vendors in North America, both sell services through a maze of resellers who package the services differently offering a variety of packages. As a general rule, the basic packages sold by the vendors are directed at home users, and business users will need to get service through a reseller. Since there are often modest inaccuracies in the reseller marketing materials and support information, it is not all that easy to identify exactly what is allowed/supported by any given package.

Starband filed for Chapter 11 bankruptcy in June 2002 although their service is still in operation and orders for new service are still being taken as of August 2002. The major issue in Starband bankruptcy is transponder access and that seems to be resolved. It is anticipated that reorganization might be completed in early 2003. A third (or maybe second by then) major North American satellite service is scheduled to come on line in 2003. (Update: in late 2002 DirecPC stated that their satellite service is losing money and that they are in overall financial difficulty. They have not, however, indicated any plans to discontinue service).

http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/Sat-HOWTO.pdf

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