Satellite Internet access
Succeeding generations of communications satellites featuring larger capacities and improved performance characteristics were adopted for use in television delivery, military applications and telecommunications purposes.
Among prominent aspirants in the early-stage satellite Internet sector was Teledesic, an ambitious and ultimately failed project funded in part by Microsoft that ended up costing more than $9 billion.
The term "bent-pipe" is used to describe the shape of the data path between sending and receiving antennas, with the satellite positioned at the point of the bend.
[26] Along with dramatic advances in satellite technology over the past decade, ground equipment has similarly evolved, benefiting from higher levels of integration and increasing processing power, expanding both capacity and performance boundaries.
In short, the gateway receives radio wave signals from the satellite on the last leg of the return or upstream payload, carrying the request originating from the end-user's site.
For the customer-provided equipment (i.e. PC and router) to access the broadband satellite network, the customer must have additional physical components installed: At the far end of the outdoor unit is typically a small (2–3-foot, 60 to 90 cm diameter), reflective dish-type radio antenna.
These parameters are generally set at the time the equipment is installed, along with a beam assignment (Ka-band only); these steps must all be taken prior to the actual activation of service.
It provides two types of connectivity: Consumer grade satellite modems typically employ either the DOCSIS or WiMAX telecommunication standard to communicate with the assigned gateway.
[34] 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 apparent round trip time (RTT) per packet by splitting ("spoofing") the feedback loop between the sender and the receiver.
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.
[43][44] A proposed alternative to relay satellites is a special-purpose high altitude platform stations 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.
[citation needed] Onboard batteries would charge during daylight hours through solar panels covering the wings and would provide power to the plane during night.
[46] Satellite communications on the Ka band (19/29 GHz) can use special techniques such as large rain margins, adaptive uplink power control and reduced bit rates during precipitation.
Rain margins are the extra communication link requirements needed to account for signal degradations due to moisture and precipitation, and are of acute importance on all systems operating at frequencies over 10 GHz.
Modern consumer-grade dish antennas tend to be fairly small, which reduces the rain margin or increases the required satellite downlink power and cost.
Large commercial dishes of 3.7 m to 13 m diameter can be used to achieve increased rain margins and also to reduce the cost per bit by allowing for more efficient modulation codes.
As the radio frequency decreases, to below 900 MHz, penetration through vegetation increases, but most satellite communications operate above 2 GHz making them sensitive to even minor obstructions such as tree foliage.
There are several types of two-way satellite Internet services, including time-division multiple access (TDMA) and single channel per carrier (SCPC).
These types of system are generally unsuitable for use on moving vehicles, although some dishes may be fitted to an automatic pan and tilt mechanism to continuously re-align the dish—but these are more expensive.
Consumer satellite Internet customers range from individual home users with one PC to large remote business sites with several hundred PCs.
Home users tend to use shared satellite capacity to reduce the cost, while still allowing high peak bit rates when congestion is absent.
In 2006, the European Commission sponsored the UNIC Project which aimed to develop an end-to-end scientific test bed for the distribution of new broadband interactive TV-centric services delivered over low-cost two-way satellite to actual end-users in the home.
Due to the low bandwidths involved it is extremely slow to browse the web with such a connection, but useful for sending email, Secure Shell data and using other low-bandwidth protocols.
The ISP's routers connect to proxy servers which can enforce quality of service (QoS) bandwidth limits and guarantees for each customer's traffic.
However, Internet content such as web pages can still be distributed over a one-way system by "pushing" them out to local storage at end user sites, though full interactivity is not possible.
Similar to one-way terrestrial return, satellite Internet access may include interfaces to the public switched telephone network for squawk box applications.
Emerging commercial services in this area include: In its report released in February, 2013, the Federal Communications Commission noted significant advances in satellite Internet performance.
[59][60][61] The EchoStar XVII satellite was launched July 5, 2012 by Arianespace and was placed in its permanent geosynchronous orbital slot of 107.1° West longitude, servicing HughesNet.
Since 2013, the O3b satellite constellation (in Medium Earth Orbit at an altitude of 8,063 km) claims an end-to-end round-trip latency of 140 ms for data services.
Since 2024, the next generation O3b mPOWER constellation has been operating alongside in MEO, offering tens of Mbps to multiple Gbps per service with a latency of about 150 ms[66] As of September 2024[update], 6,426 Starlink satellites are orbiting Earth.
