Challenge Internet via satellite

]History of satellite Internet

Following the launch of the first satellite, Sputnik 1, by the Soviet Union in October, 1957, the US successfully launched the Explorer 1satellite in 1958. The first commercial communications satellite was Telstar 1, built by Bell Labs and launched in July, 1962. The idea of a geostationary satellite — one that could orbit the Earth above the equator and remain fixed by following the Earth’s rotation — was first proposed by science fiction writer Arthur C. Clarke in 1945. The first satellite to successfully reach geostationary orbit wasSyncom3, built by Hughes Aircraft for NASA and launched Aug. 19, 1963. Many improvements and modifications followed, and after the invention of the Internet and the World Wide Web, geostationary satellites were looked at as an alternate means of providing Internet service. Part of the story involves the opening up of the K_a band for satellites. In December, 1993, Hughes Aircraft filed with the Federal Communications Commission for a license to launch the first K_a-band satellite, Spaceway. In 1995, the FCC issued a call for more K_a-band satellite applications, and 15 companies filed applications. Among those were EchoStar, Lockheed Martin, GE-Americom,Motorola and KaStar Satellite, which later became WildBlue.

 ^[4WildBlue satellite Internet dish on the side of a house

In the midst of all this came Teledesic, an extremely ambitious and ultimately failed project funded in part by Microsoft that ended up costing more than $9 billion. The idea was to create a broadband satellite constellation of hundreds of satellites in the K_a-band frequency, providing cheap Internet with download speeds up to 100 Mbit/s. The project was abandoned in 2003. While unsuccessful, Teledesic likely stalled satellite Internet development by other companies, and it wasn’t until the 2000s that the first commercial K_a-band Internet satellites were
launched.

The first Internet ready satellite for consumers was launched Sept. 27, 2003 by Eutelsat. ^[1]

Other services followed, including offerings from WildBlue in 2000 and HughesNet, both of which remain the two dominant players in the market today. WildBlue was acquired by ViaSat in 2009^[2]; HughesNet was acquired by EchoStar in 2011. ^[3]

A new generation of equipment has significantly increased the speed offerings of satellite Internet providers, starting with ViaSat’s ViaSat-1 satellite in 2011 and HughesNet’s Jupiter in 2012. The new satellites have bumped the download speeds of their service from the 1-3 Mbit/s up to 12-15Mbit/s and beyond. The improved service has been a boon to rural residents who’d previously only had access to slower service via dial-up, DSL or the original satellites.

]Challenges & limitations

]Signal latency

Latency is the delay between requesting data and the receipt of a response, or in the case of one-way communication, between the actual moment of a signal's broadcast and the time it is received at its destination.

Geostationary unsuitable for low-latency applications

A geostationary orbit (or geostationary Earth orbit/GEO) is a geosynchronous orbit directly above the Earth's equator (0° latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers. Communications satellites and weather satellites are often given geostationary orbits, so that the satellite antennas that communicate with them do not have to move to track them, but can be pointed permanently at the position in the sky where they stay. Due to the constant 0° latitude and circularity of geostationary orbits, satellites in GEO differ in location by longitude only.

Compared to ground-based communication, all geostationary satellite communications experience high latency due to the signal having to travel 35,786 km (22,236 mi) to a satellite in geostationary orbit and back to Earth again. Even at the speed of light (about 300,000 km/s or 186,000 miles per second), this delay can be significant. If all other signaling delays could be eliminated, it still takes a radio signal about 250 milliseconds (ms), or about a quarter of a second, to travel to the satellite and back to the ground.^[5] The absolute minimum total amount of delay is variable, due to the satellite staying in one place in the sky, while ground based users can be directly below with a roundtrip latency of 239.6 ms, or far to the side of the planet near the horizon with a roundtrip latency of 279.0 ms.^[6]

For an internet packet, that delay is doubled before a reply is received. That is the theoretical minimum. Factoring in other normal delays from network sources gives a typical one-way connection latency of 500–700 ms from the user to the ISP, or about 1,000–1,400 ms latency for the total round-trip time (RTT) back to the user. This is much more than most dial-up users^]

experience at typically 150–200 ms total latency, and two orders of magnitude higher than the typical 15-40 ms latency experienced by users of other high-speed internet services, such as cable or VDSL.^[7]

For geostationary satellites, there is no way to eliminate latency, but the problem can be somewhat mitigated in Internet communications with TCP acceleration features that shorten the round trip time (RTT) per packet by splitting the feedback loop between the sender and the receiver. Such acceleration features are usually present in recent technology developments embedded in new satellite Internet services.

Latency also impacts the initiation of secure Internet connections such as SSL which require the exchange of numerous pieces of data between web server and web client. Although these pieces of data are small, the multiple round trips involved in the handshake produce long delays compared to other forms of Internet connectivity, as documented by Stephen T. Cobb in a 2011 report published by the Rural Mobile and Broadband Alliance.^[8] This annoyance extends to entering and editing data using some Software as a Service orSaaS applications as well as other forms of online work.

The functionality of live interactive access to a distant computer—such as virtual private networks—is working much better with the new generation of satellite Internet service than in the past.

Acceptable latencies, but lower speeds, of lower orbits

Medium Earth orbit (MEO) and low Earth orbit (LEO) satellites do not have such great delays. For example:

·                    The current LEO constellations of Globalstar and Iridium satellites have delays of less than 40 ms round trip, but their throughput is less than broadband at 64 kbit/s per channel. The Globalstar constellation orbits 1,420 km above the earth and Iridium orbits at 670 km altitude.

·                    The proposed O3b Networks MEO constellation scheduled for deployment in 2010 would orbit at 8,062 km, with RTT latency of approximately 125 ms. The proposed new network is also designed for much higher throughput with links well in excess of 1 Gbit/s (Gigabits per second).

·                    The planned COMMStellation™, scheduled for launch in 2015, will orbit the earth at 1,000 km with a latency of approximately 7 ms. This polar orbiting constellation of 78 microsatellites will provide global backhaul with throughput in excess of 1.2 Gbit/s.

Unlike geostationary satellites, low and medium Earth orbit satellites do not stay in a fixed position in the sky. Consequently, ground based antennas cannot be easily locked into communication with any one specific satellite. Communications may involve more diffuse or completely omnidirectional ground antennas capable of communicating with one or more satellites visible in the sky at the same time, but at significantly higher transmit power than fixed geostationary dish antennas, and with much poorer signal to noise ratios for receiving the signal. Tracking a single low earth orbit satellite with a high-gain narrow beam is possible, but requires a motorized antenna mount and complex software that can predict the path of each satellite in the constellation. As with GPS, the small orbits may cause a low Earth orbit satellite to only be in the sky for an hour or less before it goes over the horizon and out of range, so a complex relaying and passing-off needs to be done to hand over the fixed-position terrestrial signal to other satellites passing overhead.

Ultralight atmospheric aircraft as satellites

A proposed alternative to geostationary relay satellites is a special-purpose solar-powered ultralight aircraft, which would fly along a circular path above a fixed ground location, operating under autonomous computer control at a height of approximately 20,000 meters.

One example of this is the United States Defense Advanced Research Projects Agency Vulture project, an ultralight aircraft capable of station-keeping over a fixed area for a period of up to five years, able to provide both continuous surveillance to ground assets as well as to provide extremely low latency communications networks.^[9]

Onboard batteries would be charged during daylight hours by solar panels covering the wings, and would provide power to the plane during night. Ground-based satellite dishes would relay signals to and from the aircraft, resulting in a greatly reduced round-trip signal latency of only 0.25 milliseconds. The planes could potentially run for long periods without refueling. Several such schemes involving various types of aircraft have been proposed in the past.

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