Satellite Phones Abstract— This document gives overview of Satellite Phones technology in terms of its evolution, parameters, advantage over other technology. This paper also briefs different service providers of satellite phones and their features also its scope in india. I. INTRODUCTION A satellite phone or sat phone is a mobile phone that sends and receives calls using satellites rather than landlines or cellular broadcasting towers Sat phones are divided into 3 types: Installed, Laptop and Hand Held All sat phones allow communication to the standard telephone network i.
e. irect dial voice, fax and data communications Satellites used for sat phones are basically II. Geosynchronous satellites Geostationary satellites, orbit around the equator in the same direction as the Earth rotates. They are positioned at a height above the Earth such that the same time for the satellite to complete its orbit is the same as the time it takes for the Earth to rotate once about its axis i. e. 24 hours [pic] Polar satellites Polar satellites travel around the Earth in an orbit that travels around the Earth over the poles.
The Earth rotates on its axis as the satellite goes around the Earth.
Thus over a period of many orbits it looks down on every part of the Earth [pic] III. Data Transmission Most satellite services permit data as well as voice to be sent and received. However, all such services have very slow data bandwidths, typically in the realm of about 2400 baud (ten to twenty times slower than a regular dialup modem, and 50+ times slower than broadband). Add the slow data transfer rate to the reasonably high cost per minute of airtime, and you won’t want to use your satellite phone to access the internet for casual web surfing. Most of the satellite services allow for fax transmission. IV.
Signal Coverage Satellite phone signals are very weak, and there needs to be an unobstructed line of sight between your phone’s antenna and the satellite it is communicating with. This means satellite phones will generally not work indoors, unless you are by a window and the window – by good chance – happens to be looking out to that part of the sky where an Iridium satellite currently is the Iridium satellites are moving all the time, there is no rule of thumb (such as ‘you need to have a view of the southeast sky’) as might have been the case with fixed satellites in terms of where to look for satellites.
Satellites may be anywhere – north, south, east or west, and because they move across the sky quite quickly, if you start off a call with a clear view to a satellite, if the satellite then moves behind something that blocks your view to the satellite, and if there are no other satellites in clear view, your call may be dropped. V. SATELLITE PHONE SERVICES The four main satellite networks at present are Iridium, Globalstar, Thuraya and Inmarsat 1. Inmarsat It started operations in 1979 as a non profit organization. It was launched to provide safety at sea.
Later the Inmarsat began to be used for commercial purposes. Coverage is very good, being provided from a network of geosynchronous satellites, but doesn’t extend all the way to the north or south poles It is probably too bulky for people seeking a convenient portable solution 2. Thuraya Started operating in 2001 Thuraya covers parts of India, Asia, Africa, the entire Middle East and Europe It uses geosynchronous satellites They cost about half the price of an Iridium phone FEATURES: SMS capability 9. 6 kbits/s of data & fax service 60 kbit/s downlink and 15 kbit/s uplink 44 kbit/s high-speed data transfer GPS is supported by all handsets A number of value-added services, such as news, call back, call waiting, missed calls, voicemail, WAP, etc. 3. Globalstar This service rolled out in late 1999 Globalstar covers about 80% of the earth’s landmasses, excluding northern and southern polar regions With over 315,000 subscribers (as of June 2008), Globalstar is the world’s largest provider of mobile satellite voice and data services. Globalstar offers these services to commercial and recreational users in more than 120 countries around the world.
It uses LEO satellites Offers data as well as voice service Most Globalstar providers have roaming agreements with local cellular operators, enabling the use of a cellular SIM card with a Globalstar handset and vice versa. 4. Iridium The concept that was to become Iridium was first mooted in the mid 1980s and the concept formalized in 1987, then developed during the 1990s Bankruptcy in 1999 It is the only current satellite network that provides coverage over the entire earth, including the oceans The current satellites are projected to remain operational at least through 2014
FEATURES: The four inter-satellite cross links on each satellite operate at 10 Mbit/s Iridium is currently engaged in studies to build and launch a second generation of satellites, consisting of 66 satellites and six spares. Each satellite can support up to 1100 concurrent phone calls and weighs about 1,500 pounds (700 kg). Because it uses the high-altitude geosynchronous satellites, conversations have the annoying satellite delay in them VI. Which is the Best Satellite Phone Service Inmarsat has little appeal, due to its bulky expensive equipment and geosynchronous satellites.
Thuraya has the most limited service area, and isn’t really intended as a global phone. Globalstar was quite possibly your best choice if you simply want a phone that will work everywhere in the US. But recent (2007) deterioration in Globalstar service makes it no longer satisfactorily reliable and no longer a viable option for most people. If you’re seeking truly global coverage – a phone you can take anywhere and know it will always work – and want the most disaster proof service that you know you can rely on in an any type of emergency, then Iridium is the best choice. VII.
ADVANTAGES The advantage of a satellite phone is that it can complete calls from anywhere A satellite phone can operate in the middle of the Sahara desert, at the top of Mount Everest, or from a clearing deep within a South African jungle Satellite phones can provide the ultimate in global coverage It can provide backup communication in disasters when cellular towers or landlines might not be functionalSmaller and more portable than HF radios No installation required SMS/data capable Dual-mode functionalities in some handsets – there are now GSM/Sat phones and CDMA/Sat phones
VIII. DISADVANTAGES A satellite phone only requires a clear line of sight to the sky They usually don’t work inside buildings or anywhere that has an obscured view of the sky Satellite phones are also considerably more expensive to purchase, and their airtime rates are also higher There is a noticeable delay in conversations. The signal must first travel to the satellite, then to an earthbound gateway before being routed to the receiver. The receiver’s response will follow the same path in reverse, taking equally long to reach the caller IX. SCOPE IN INDIA
The Indian Space Research Organization is working on a new device to drastically reduce the cost of satellite phone usage and enable access to remote areas of the country The design of GSAT-6 experimental satellite that will carry the device to connect mobile handsets through a satellite link is being finalized Similar to the exponential growth of mobile subscriber base in the sub-continent after the advent of the cellular technology in the GSM and CDMA space a revolution is expected to take place when satellite phones become affordable by better and efficient use of space technology and applications
The GSAT-6 will be deployed in the geo-stationary orbit at 36,000km from earth by 2010 X. CONCLUSION Satellite phones are not an alternative to regular cell phones But are intended as an alternate communication system for when and where cell phones don’t work You can happily live your life without always having a working phone beside you But if you go traveling or adventuring into out of the way places, you might appreciate the safety benefits of always being able to call for help if something should go wrong, and in turn, always being reachable by friends and family should that be necessary too
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Satellite Phones. (2018, Jun 11). Retrieved from https://graduateway.com/satellite-phones-essay/