PLEASE NOTE: All articles are copyright but you can link to this page by copying and pasting the html code EXACTLY as shown. Thank you. <a href="http://www.1st-4-cheap-mobile-phones.co.uk/articles/art13.shtml" > <b>Mobile Phone and Cell Phone Articles</b></a> A Brief Introduction to Satellite Phones by Michael Furniss www.greatbritishsim.com Over the last few years the use of satellite phones has been on the increase, they are now cheaper and more available than ever, however, this has not made it any easier for the consumer. With the choice of products on offer, how do you know which is the right one for you? Why satellite phones have been developed It seems like it is getting harder and harder to pass the day without being subjected to the unrelenting cacophony of mobile communication. Whether it be the 'A-Team theme tune' on the train, Vivaldi's 'Four Seasons' in the cinema or just the 'beep beep' of a received text message in the classroom. Cellular phones have developed into an intrinsic, and let's face it, sometimes inane part of modern life. They now have their own slang, snobbery and criminal subculture. In fact, the only place where you can escape the constant hum of mobile life is far from cellular network coverage, in the 'remote and wild corners' of the world. And here is the paradox; due to their remoteness, these are the very places where cellular phones would have merit, earn their crust, realise their raison d'etre. As developments in business, travel and technology have led to the increased human exploration of such 'remote and wild corners', the demand for a system of communication, beyond that of cellular phones, has arisen. It is for this reason that satellite technology has been developed. Popular satellite systems Three satellite systems that have gained wide spread popularity are Inmarsat, Iridium and Globalstar. Although they are all attempting to meet the same demand, they each go about this in different ways. What follows is a basic overview of some of their strengths and weaknesses. Inmarsat Inmarsat, the first mobile satellite system to be conceived, is a great example of how the technology has emerged from a niche market and been made available to all. Originally designed for the maritime industry, they now have over 100,000 registered Mini-M satellite phone terminals that are used across a broad range of industries. The Inmarsat network consists of four geo-stationary satellites 35,600km above the Earth. The satellites are positioned at equatorial points over the Indian Ocean, the Pacific Ocean and the Eastern and Western sides of the Atlantic. The 'footprint' created by this configuration is able to provide almost total global communication coverage with the exception of the Poles. The first advantage that this gives Inmarsat is, once a signal is sent to a satellite, its individual 'footprint' is often large enough to deliver that signal to its destination without having to transfer via another satellite first. This minimizes the risk of the signal being lost. The main argument that has been levelled against Inmarsat terminals regards their size; they are comparable to modern laptop computers. Inmarsat rivals, Iridium and Globalstar, use handsets that are far more akin to cellular phones, which it is claimed, weigh less and are easier to use. This is not an entirely unfair point; it is true that Inmarsat equipment is larger than that of its contemporaries. Where they can out perform Iridium and Globalstar is in their ability to transfer data and faxes. This lends Inmarsat much more effectively to the setting up of semi-permanent offices where, along side voice facilities, more capable fax and data services are required. When used in this capacity Inmarsat's size ceases to become such an issue. Inmarsat are planning to expand this service with their next generation satellites, due to go live in 2005. These will support B-GAN (Broadband Global Area Network). B-GAN, it is claimed, will be 100 times more powerful than the current generation of satellites and, will have 10 times the capacity. With this increase Inmarsat are aiming to supply superior Internet, Intranet and video services as well as voice, fax and data. Iridium Iridium is probably the most famous, or rather notorious, of the satellite systems on the market. They very publicly went bankrupt in 1999; one year after the service was launched. However, Motorola Inc. stepped in and settled their debts. Iridium was re-launched in 2001 and has been operating ever since. Iridium's mission was to create a satellite service that would provide truly global coverage, a service that Inmarsat and Globalstar have not yet realised. To achieve this the Iridium network uses 66 satellites, 450 miles high, orbiting the globe on 6 different planes. Travelling at 16,832 miles per hour, each satellite is able to circle the globe every 100 minutes. This configuration ensures that an Iridium handset will be able to send and receive calls from any location on the planet (the only exceptions to this being countries who have declined to support the service for political reasons). As long as the handset has a clear line of site to the sky it will maintain communication with at least two satellites at any one time. The main criticism that has been levelled at Iridium is the fact that they are limited in their data and fax capabilities. The service is available but not to the standards that Inmarsat and Globalstar can provide. Also, as mentioned briefly in regards to Inmarsat's service, Iridium run a higher risk of loosing a signal once it has been sent. This happens because they rely on the passing of signals via a number of satellites before routing them to their final destinations. The more links in the chain, the greater the chance of the signal being lost. Globalstar The Globalstar network was developed specifically with the business traveller in mind. They envisioned their customers as people who were working on the fringes of cellular networks, crossing in and out of coverage areas. Therefore they designed a compact tri-band handset that would work on both the cellular AMPS and CDMA networks and, the Globalstar network of 48 Low Earth Orbiting satellites. These satellites orbit the Earth at an altitude of 875 miles. The phones are designed to switch seamlessly between the cellular networks and the satellite network, even during a call. The phone will always use the cellular networks if available. Only when these are not available will they link to the satellite network. By using this method the idea was to offer the best cost effective service, you would only use the more expensive satellite service when there was no alternative. The downside of the Globalstar system is its coverage area. By operating on the AMPS and CDMA standards they have limited themselves to the localities where those standards are supported. At the moment this includes the Americas, Russia, and parts of Asia. Likewise their satellite network coverage area is limited compared to those of its rivals. They can only offer service in about 100 countries, their territorial waters and some mid ocean waters. Globalstar, like Inmarsat have developed their data and fax transfer capabilities, using a laptop or PDA (Personal Digital Assistant) email and Internet access are possible, but like their voice service, they can only offer limited coverage. They also share the same problem as Iridium in that there is a higher risk of loosing signals due to the need to send them via a number of satellites before connecting them with their destination. The next step This information is not intended as a definitive guide to satellite phones. Rather, it is meant as a brief introduction to some of what is available. As you can see from the three examples highlighted, there is not one all encompassing system that can out perform its rivals in all areas. Each has certain strengths and certain weaknesses. If you decide that you need to use a satellite phone, you need to decide which satellite network is best for you. You must assess what functions are most valuable to you~. Do you need total global coverage? Do you need the ability to send and receive data? Do you want something that is easy to carry? Once you are clear in your head what you expect from satellite communication then you are able to make your decision from a more informed and confident position. [CaRP] XML error: mismatched tag at line 13 |
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