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How Does Satellite Internet Work

How Does Satellite Internet Work

For remote or suburb areas and mobile locations like sea-faring vessels and vehicles, which do not have an access to terrestrial internet (DSL), satellite internet is perhaps the best option. This article is for those, who want to know how satellite internet works?
Rajib Singha
Satellite Dish for Telecommunication
Satellite Internet technology, as the name suggests, uses satellites for its working. High speed Internet is provided with an 'always-connected' feature, without using telephone or cable lines. The satellite dish provides a two-way data communication for both transmission and reception of data. The system provides a download speed of about 500Kbps (kilobytes per second) and the upload speed is around one-tenth the download, which is 50Kbps. The satellite connection is ten times faster than normal dial-up modems.

Working of Satellite Internet

Satellites orbiting the Earth are located over the equatorial region, so the satellite dish (1.2m diameter or two-foot by three-foot dish) at the user's location must be pointed precisely towards the south to avoid interference with other satellites. The satellite modem converts digital signals into analog form. For two-way data communication (upload and download), the system requires two satellite modems and coaxial cables (cables having common axis) to connect the dish to the modem.

The dish at the user's end sends radio frequency waves or data (received from the transceiver that connects to the computer) to the transponder (satellite). At the other end, the transponder sends the relay frequencies to a hub teleport at a ground station. The teleport then forwards the data through the terrestrial Internet. For receiving the requested information, the same process is followed in a reverse order to direct the data back to the user's dish, and the installed modem delivers the desired webpage to the computer.

The two-way technology uses Internet Protocol (IP) multi-casting feature. This feature allows a communication of around 5000 channels, through one single satellite. This is achieved by transmitting compressed data with a smaller bandwidth. This is not in case of terrestrial Internet systems, as their bandwidth optimization is limited.

There are, however, some limitations to the working of satellite Internet. The entire process of sending and receiving data should ideally take about half a second, however due to latency the process gets delayed. Latency is defined as the sum of time taken by the requested data to get from one point to another and the round-trip time (RTT) in getting the response. The latency in satellite Internet access is higher than normal land-based terrestrial Internet, due to the location of the geostationary satellites. The data or the frequency has to cover a total distance of 35,000 km, from the Earth's surface to the satellite and then back to the Earth again.

Satellite Internet is not suitable for applications requiring real-time response. Online games, real time flight tracking or any other live programs cannot be accessed using this technology because they require very low latency (500 to 900 ms). However, the latency can be countered by the TCP acceleration process which manages to decrease the RTT (round-trip time). The communication is also affected by weather, such as rain or moisture in the air, that can affect the transmission. This signal interference can be avoided or limited by use of a satellite dish with a larger surface area, so as to increase the downlink (download) signal and strengthen the uplink (upload) signal.

Satellite Internet, though a bit costlier than DSL and cable systems, promises reliable service. Web surfing can be achieved at a higher speed and unlike dial-up Internet services, there is no wastage of time of the Internet user. This Internet technology allows the user to surf the Internet even during peak usage times. And, the 'always-connected' feature, keeps your computer connected to the Internet, no matter in which corner of the world you are!