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Optical Fiber
Optical Fiber
Fiber-To-The-Home Internet is based on optical fiber cables carrying signals with light, typically in clear glass strands roughly the size of a hair. The technology is non-conducting and not subject to powerline or other electrical or electromagnetic interference. Optical fiber, via light, is capable of carrying signals at orders of magnitude higher data rates than radio signals or copper cables. Optical fiber can also carry high speed signals many miles further than copper cable. It can fit many individual connections in a much smaller cable than copper phone line, and is able to deliver individual fiber connections to subscribers instead of the shared connections with shared bandwidth of cable company service. Fiber-optic cable can be run on poles, or buried, but it can also be run on the ground.
ADSL (e.g. Consolidated)
ADSL (e.g. Consolidated)
Asynchronous Digital Subscriber Link is based on telephone cable copper pairs carrying data by high frequency electrical signals superimposed on the voice signals. There are different kinds of DSL signaling, with different inherent maximum data rates, but all of them are subject to severe distance limitations. In Somerville those are effectively ADSL and ADSL 2+. The further from the DSL Access Modules (DSLAM), or the longer the copper cable pair that connects the subscriber, the slower their maximum data rate. ADSL is asymmetrical, meaning that the download speed and upload speed are not the same, with upload speed typically 1/10th of the download speed. At 2 road miles from a DSLAM, service speed may only be 7Mbps/0.7 or slower, and 4Mbps/0.4 at 2.5 miles.
Geostationary Satellites (e.g. Hughes or Viasat)
Geostationary Satellites (e.g. Hughes or Viasat)
A satellite that orbits the earth directly above the equator at a distance and speed such that it completes an orbit in the same time as the earth rotates once, staying directly above the same place on the equator, thus never changing longitude. Geostationary satellites orbit at an elevation of 22,236 miles. Because of Maine's position in northern latitudes, we have to aim a satellite dish not overhead, but relatively low and mainly southward, and somewhat west typically, depending on the longitude of the best available satellite. Aiming low on the horizon makes the signals between your dish antenna and the satellite pass through a lot of miles of our atmosphere, being particularly susceptible to interference by weather. Up to a geostationary satellite and back down to earth adds roughly 228 milliseconds to the packet latency from its other internet travels, due to the more than 22 thousand mile distance each way. [very high latency]
Low Earth Orbit and Very Low Earth Orbit Satellites (e.g. Starlink)
Low Earth Orbit and Very Low Earth Orbit Satellites (e.g. Starlink)
A constellation of satellites that follow much lower orbits than geostationary or geosynchronous, but must complete an orbit many more times per day to keep from crashing to earth. This enables communication with satellites that are closer and through much less atmosphere. But it also means that the satellite you communicate with comes into view and leaves your dish's view, requiring a hand-off of communication and picking up a new satellite, over and over again. That makes the service dependent on a wide enough view of the sky to pick up a new satellite before losing contact with the current one. How wide that view must be is dependent upon how many satellites are up in which orbits that are visible from your location. Starlink satellites range from roughly 300 km to 500 km altitude, completing an orbit in roughly 90 to 95 minutes. The closeness also means there is far less latency (the time to send a packet to a satellite and for that to come back to earth elsewhere and be connected onto the internet and reach its destination. Up to the satellite and down adds roughly 2 (VLEO) to 6.6 milliseconds (LEO) to the packet latency from its other internet travels. [low latency] Starlink uses multiple radio bands (LEO satellites (500 km elevation) will transmit in the Ku (12- to 18-gigahertz) and Ka (26.5- to 40-GHz) bands, VLEO satellites (300 km elevation), will use frequencies up in the V band, between 40 and 75 GHz), some of which are absorbed by heavy rain or ice, but because of the fairly direct path through less atmosphere, this is much less of a problem than for geostationary satellite communications, however Starlink's statement on the subject includes this: "Heavy rain or wind can also affect your satellite internet connection, potentially leading to slower speeds or a rare outage." See starlink.com/faq for their complete statement and other things you should know as you consider starlink.
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