On Signal Latency: Ultralight atmospheric aircraft as satellites
Signal latency is the delay between requesting data and the recipient 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. 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. A geostationary orbit, or “Geostationary Earth Orbit’ (“GEO”), is a circular orbit 35,786 km (22,236 mi) above the Earth’s equator and following the direction of the Earth’s rotation.
Even at the speed of light in vacuum (about 300,000 km/s or 186,000 miles per second), usually denoted by “c,” a universal physical constant important in many areas of physics, 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. 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 Internet access (often shortened to “cable Internet” or simply “cable”), which in telecommunications, is a form of broadband Internet access that uses the cable television infrastructure; or very-high-bitrate digital subscriber line (“VDSL” or “VHDSL”), a digital subscriber line (DSL) technology providing faster data transmission over a single flat untwisted or twisted pair of copper wires (up to 52 Mbit/s downstream and 16 Mbit/s upstream), and on coaxial cable (up to 85 Mbit/s down- and -upstream) using the frequency band from 25 kHz to 12 MHz.
A proposed alternative to geostationary relay satellites is a special purpose solar-powered ultralight aircraft, a lightweight, 1- or 2-person fixed wing aircraft (also called “microlight aircraft” in the United Kingdom, India and New Zealand), powered by solar energy, the radiant light and heat from the sun using a range of ever-evolving technologies. It would fly along a circular path above a fixed ground location, operating under autonomous computer control at a height of approximately 20,000 meters.
Onboard batteries would be charged during daylight hours by solar panels covering the wings, and would provide power to the plane during the 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.
See: Australian Satellite Internet
