Since satellite phones are purpose-built for one particular network and cannot be switched to other networks, the price of handsets varies with network performance. If a satellite phone provider encounters trouble with its network, handset prices will ll, then increase once new satellites are launched. Similarly, handset prices will increase when calling rates are reduced.
Their signals will usually bypass local telecoms systems, hindering ship and wiretapping attempts. These countries tend to score low on the Democracy index, with the exception of India, so a ban can be the result of the states desire for mass surveillance or that it lacks the technology to intercept satellite phone traffic.
Satphones on displayWhile it is possible to obtain used handsets for the Thuraya, Iridium, and Globalstar networks for approximately , the newest handsets are quite expensive. The Iridium 9505A, released in 2001, sold in March 2010 for over $1,000 USD new.
utilizes LEO (low ) . The advantages include providing worldwide wireless coverage with no gaps. LEO satellites orbit the earth in high speed, low altitude orbits with an orbital time of 70100 minutes, an altitude of 640 to 1120 kilometers (400 to 700 miles), and provide coverage cells of about (at a 100-minute orbital period) 2800km in radius (about 1740mi). Since the satellites are not geosynchronous, they must fly complete orbits. At least one satellite must have line-of-sight to every coverage area at all times to guarantee coverage. Depending on the positions of both the satellite and terminal, a usable pass of an individual LEO satellite will typically last 415 minutes on average;
Among the most expensive satellite phones are BGAN terminals, often costing several thousand US dollars.
Another disadvantage of geostationary satellite systems is that in many areaseven where a large amount of open sky is presentthe line-of-sight between the phone and the satellite is broken by obstacles such as steep hills and forest. The user will need to find an area with line-of-sight before using the phone. This is not the case with LEO services: even if the signal is blocked by an obstacle, one can wait a few minutes until another satellite passes overhead, but a moving LEO may drop a call when line of sight is lost.
Inmarsat: The oldest satellite phone operator, founded in 1979. It originally provided large fixed installations for ships, but has recently entered the market of hand-held phones in a joint venture with ACeS. The company operates eleven satellites. Coverage is available on most of the Earth, except polar regions.
University of Surrey pages with information on some satellite systems, including currently planned, and defunct proposals such as Teledesic. (non-commercial)
Satellite phones are legal in most countries and are not disvoured by many governments. In Australia, residents of remote areas may apply for a government subsidy for a satellite phone.
Reporters and journalists have also been using satellite phones to communicate and report on events in war zones such as Iraq.
MSAT / SkyTerra: An American satellite phone company that uses equipment similar to Inmarsat,Available Online For Free Study Material For Cbse Students. but plans to launch a service using hand-held devices in the Americas similar to Thurayas.
ACeS: This small regional operator provides voice and data services in East Asia using a single satellite.
However, this method can be inaccurate by tens of kilometers. On some Iridium hardware the coordinates can be extracted using AT commands, while recent Globalstar handsets will display them on the screen.
See also: Global Mobile Satellite Systemand International Networks (country code)Satellite phones are usually issued with numbers in a special country calling code.
Low earth orbit systems including some of the defunct ones have been allocated number ranges in the International Telecommunications Unions Global Mobile Satellite System virtual country code +881. Iridium satellite phones are issued with codes +881 6 and +881 7. Globalstar, although allocated +881 8 and +881 9 use U.S. telephone numbers except for service resellers located in Brazil which use the +881 range.
Geostationary satellites have a limitation of use in latitude,college education. generally 70 degrees north of the equator to 70 degrees south of the equator. This is a result of look angles being so low on the horizon increasing the chances of terrestrial and other interference from sources in the same frequency bands.
Globalstar provides a one-way data uplink service, typically used for asset tracking.
thus, a constellation of satellites is required to maintain coverage (as is done with Iridium, Globalstar, GPS, and others).
The cost of voice calls from a satellite phone varies from around $0.15 to $2 per minute, while calling them from landlines and regular mobile phones is more expensive. Costs for data transmissions (particularly broadband data) can be much higher. Rates from landlines and mobile phones range from $3 to $14 per minute with Iridium, Thuraya
Most satellite phone networks have pre-paid plans, with vouchers ranging from $100 to $5,000.
Satellite phone (Inmarsat)A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites. They provide similar functionality to terrestrial mobile telephones; voice, short messaging service and low-bandwidth internet access are supported through most systems.
Calls from satellite phones to landlines are usually around $0.80 to $1.50 per minute unless special offers are used. Such promotions are usually bound to a particular geographic area where traffic is low.
Globalstar: A network covering most of the worlds landmass using 44 active satellites; however many areas are left without coverage since a satellite must be in range of an earth station. Satellites fly in an inclined orbit of 52 degrees, so polar regions cannot be covered. The network went into limited commercial service at the end of 1999 .
Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions.
These phones provide broadband Internet and voice communications. Satellite phones are sometimes subsidised by the provider if one signs a post-paid contract but subsidies are usually only a few hundred US dollars or less.
See also: Cascading ilureMost mobile telephone networks operate close to capacity during normal times, and large spikes in call volumes caused by widespread emergencies often overload the systems when they are needed most. Examples reported in the media where this has occurred include the September 11 attacks, the 2006 Hawaii earthquake, the 2003 Northeast blackouts, Hurricane Katrina,
Inmarsat satellite phones are issued with codes +870. In the past additional country codes have been allocated to different satellites but the codes +871 to +874 have been phased out at the end of 2008 leaving Inmarsat users with the same country code regardless of which satellite their terminal is registered with.
Text is available under the ; additional terms may apply. See Terms of Usatellite phonese for details.
and INMARSAT being some of the most expeSatellite phone satellite phonensive networks to call. The receiver of the call pays nothing, unless he is being called via a special reverse-charge service.
A fixed installation, such as one used aboard a ship, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites. Smaller installations using VoIP over a two-way satellite broadband service such as BGAN or VSAT bring the costs within the reach of leisure vessel owners. Internet service satellite phones have notoriously poor reception indoors, though it may be possible to get a consistent signal near a window or in the top floor of a building if the roof is sufficiently thin. The phones have connectors for external antennas that can be installed in vehicles and buildings. The systems also allow for the use of repeaters, much like terrestrial mobile phone systems.
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Thuraya: Established in 1997, Thurayas powerful satellites enable two-thirds of the globes population to communicate in areas unserved by terrestrial networks. Thuraya is the only organization which has sold in excess of 600,000 satellite handheld phones. Thuraya delivers communications solutions across Europe, Africa, the Middle East, Asia and Australia.
Some satellite phones use satellites in geostationary orbit, 2013-1-25 下午11:31:36 which are meant to remain in a fixed position in the sky. These systems can maintain near-continuous global coverage with only three or four satellites, reducing the launch costs. The satellites used for these systems are very heavy (approx. 5000kg) and expensive to build and launch. The satellites sit at an altitude of about 35,000 kilometres (22,000mi); a noticeable delay is present while a phone call or using data services due to the large distance from users. The amount of bandwidth available on these systems is substantially higher than that of the Low Earth Orbit (LEO) systems; all three active systems provide portable satellite Internet using laptop-sized terminals with speeds ranging from 60 to 512kbit per second (kbps).
Two such systems, both based in the United States started in the late 1990s but soon went into bankruptcy after iling to gain enough subscribers to fund launch costs. They are now operated by new owners who bought the assets for a fraction of their original cost, and are now both planning to launch replacement constellations supporting higher bandwidth. Data speeds for current networks are between 2200 bit/s and 9600 bit/s using a satellite handset.
Terrestrial cell antennas and networks can be damaged by natural disasters. Satellite telephony can avoid this problem and be useful during natural disasters. Satellite phone networks themselves are prone to congestion as satellites and spot beams cover a large area with relatively few voice channels.
In 2001, service was re-established by Iridium Satellite LLC. Radio cross-links are used between satellites to relay data to the nearest satellite with a connection to an earth station.
LEO systems have the ability to track a mobile units location using doppler shift calculations from the satellite.
ICO Global Communications: A satellite phone company which has launched a single geosynchronous satellite which is not yet active.
Iridium operates a one-way pager service as well as the call alert feature.
Iridium: A network operating 66 satellites in a polar orbit that claims coverage everywhere on Earth. Commercial service started in November 1998 and fell into Chapter 11 bankruptcy in August 1999.
. Journal of Information Technology Management (Association of Management) XVI (2). ISSN1042-1319.
Smaller regional satellite phone networks are allocated numbers in the +882 code designated for international networks which is not used exclusively for satellite phone networks.
Since most satellite phones are built under license or the manucturing of handsets is contracted out to OEMs, operators have a large influence over the selling price. Satellite networks operate under proprietary closed standards, it difficult for manucturers to independently make handsets.
Satphones are popular on expeditions into remote areas where terrestrial cellular service is unavailable.
Making calls between different satellite phone networks is often similarly expensive, with calling rates of up to $15 per minute.
Some satellite phone networks provide a one-way paging channel to alert users in poor coverage areas of an incoming call. When the alert is received on the satellite phone it must be taken to an area with better coverage before the call can be accepted.
The mobile equipment, also known as a terminal, varies widely. Early satellite phone handsets had a size and weight comparable to that of a late-1980s or early-1990s mobile phone, aduedu926.typepad.com but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while some prototype satellite phones have no distinguishable difference from an ordinary smartphone.
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