Satellite+Internet_Wong+Yen+Ping&Tan+Su+Ning

Satellite Internet
//Authors: Wong Yen Ping, Tan Su Ning// Satellite internet is a form of internet access where by people use satellite to access the internet and stay connected to the world even they are in a rural area where DSL and cable connections are not available. In other words, a satellite internet connection is an arrangement in which the upstream (outgoing) and the downstream (incoming) data are sent from, and arrive at the user’s computer through a satellite, which is irrelevant of the place the user is situated. Each user’s hardware includes a satellite dish antenna and a transceiver (transmitter/receiver) that operates in the microwave portion of the radio spectrum.
 * __ INTRODUCTION __ **

There are three types of satellite internet namely two-way satellite-only communication; one-way receive, with terrestrial transmit; and one-way multicast, receive only. Communications satellites were originally designed for commercial purposes for sending telephone, radio, TV, and other signals across the country and around the world for re-transmission to businesses and homes by local telephone companies, TV stations, or cable companies. In the early 1990’s four large cable companies launched a Direct Broadcast Satellite, or DBS system called Primestar using an existing medium power Ku-band satellite and a 36″ dish. In 1994, the GM Hughes DIRECTV system was launched using a newly designed high power Ku-band satellite and an 18″ dish. These systems provided great pictures and stereo sound on 150-200 video and audio channels, and the small dish era began in a serious way.

__**IMPLEMENTATION **__ High speed satellite internet is the 21st century technology that brings internet access to virtually any home and small business in small cities and rural areas nationwide. An always-on high speed internet via satellite connection offers value-added features with no phone line or dial in. In order to access satellite high speed internet services, he or she will need to have a computer that meets the minimum system requirements of the provider. However, this service is only provided in limited areas. In America, people who are fed up with the slow dial up connection speed may want to use it. It is becoming a popular choice in United States.

To begin with, one must check the minimum system requirements of the provider. However, computers nowadays usually will meet the minimum system requirements. A small and effective satellite dish can be mounted on a pole, wall or roof, or fixed in the ground. The satellite dish at each location must be carefully positioned to avoid interference with other satellites. Once a professional installs your system which will take 2 to 3 hours, one is ready to surf the internet at lightning fast speeds. This type of broadband connection makes use of satellite technology to deliver instant connection to the internet for everyone, everywhere in the United States. So, by choosing a high speed internet via satellite, one can get excellent service at affordable price tag.

Companies that offered the satellite internet services are StarBand, Pegasus Express, Teledesic and Tachyon. Tachyon service is available today in the United States, Western Europe and Mexico. Pegasus Express is the two-way version of DirecPC. Two-way satellite Internet consists of: • Approximately a two-foot by three-foot dish • Two modems (uplink and downlink) • Coaxial cables between dish and modem

The key installation planning requirement is a clear view to the south, since the orbiting satellites are over the equator area. And, like satellite TV, trees and heavy rains can affect reception of the internet signals.

Two-way satellite internet uses IP (Internet Protocol) multicasting technology, which means up to 5,000 channels of communication, can simultaneously be served by a single satellite. IP multicasting sends data from one point to many points (at the same time) by sending data in compressed format. Compression reduces the size of the data and the bandwidth. Usual dial-up land-based terrestrial systems have bandwidth limitations that prevent multicasting of this magnitude.

**StarBand’s internet connection system ** Some satellite-internet service still requires you to have a dial-up or cable modem connection for the data you send to the internet. The satellite data downlink is just like the usual terrestrial link, except the satellite transmits the data to user’s computer via the same dish that would allow you to receive a Pay-Per-View television program.

The satellite internet basically comes in three types and they are all using the connectivity enhanced via the local satellite service. The connectivity has supported the businessman on the move and those users who regretted the lack of connectivity, due to geographic limitation.

**Connectivity via special hardware components: ** The internet connectivity via satellite can be tapped through interface presence, like the telephone network that is ‘public-switched’ as in the case of the squawk box applications. In this case, a physical and separate internet ‘connection’ is not required. The system operates with the support of a server-to-queue-data connectivity and includes an FTP (File Transfer Protocol). In the case of connectivity via system hardware components, the transmitting station or the teleport is supported by two important components.

The internet connection is made possible when the ISP routers are connected to the designed proxy servers. This connectivity enforces the band-width limits of the QOS or ‘quality of service’, thus enabling user traffic. This connectivity is furthered to the DVB encapsulator and then, the S modem. The DVB-S modem then transmits an RF (radio frequency) to the outdoor unit, through the up converter connected via a feed line. The system components also include a block up converter, an optional low noise block converter, an optional orthomode transducer, a feed horn and a waveguide. This connectivity is routed to an Earth station, which is a setup that consists of an outdoor and indoor unit.

**Connectivity via software components: ** In the case of remote sites, most satellite internet connections or one-way multicast applications need custom programming. This requires the dedicated software to be able to effectively filter, store and offer access to a selection interface and data. The transmitting station also needs to incorporate special software to handle access control and queuing-sending-encapsulating of the data on a priority basis. The remote sites require a programming back up to be able to provide authentication and take care of the proxy server settings essential to the operation. The filtering operation is provided by the DVB card driver, while the non-standard IP stacks address asymmetry and latency issues. The data is encrypted to be accessible to any satellite receiver.

The IP-over-satellite units usually incorporate proxy servers that are paired at the end-points and VPNs or virtual private network implementations. This is to ensure that communication between the clients and servers need not accept the inherent latency. The virtual private network implementations are designed for satellite links to handle long packet travel time. In connectivity via software components, the upload speeds are limited by the user's modem, and latency is high. The download speeds in such connectivity can be much faster than that in the case of dial-up.

**Connectivity via one-way terrestrial return: ** The satellite internet connectivity via one-way terrestrial return uses the traditional dial up access. The system has out-bound data traveling through a telephone-based modem. However, downloads are handled by satellite. While a license is required for the uplink station, there is no such requirement for users. Another type of the same system incorporates the use of the General Packet Radio Service. This system enhances the back-channel by using a standard GPRS connection. The upload volume in this system is low and the service is charged by volume uploaded. This enables the users to surf and download at broadband speeds! The GPRS enables a mobility that transmits in the field of 50 to 53 dBW. The mobile or satellite internet connectivity that is broadband enhanced can be accessed with the help of the recommended satellite dish width, a note-book and GPRS-GSM telephone.

__**<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">COMMON WAN IMPLEMENTATION ISSUES: LATENCY **__<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;"> Latency is one of the key measures of high performance. It refers to the delay between requesting data and getting a response which is the time between the arrival of the first bit and the time enough data has been received to begin processing, or in the case of one-way communication, between the actual moment of broadcast and the time actually received at the destination. Compared to ground-based communications, satellite communications experience high latency and it is generally not very high bandwidth because the signals have to travel through a long distance (about 35,000 km) to the satellite in space and then back to Earth again. <span style="font-size: 120%; font-family: Arial, Helvetica, sans-serif;"><span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">The signal can be delayed as much as 500 milliseconds to 900 milliseconds. This long delay makes satellite service are unusable for applications requiring real-time user input, such as online games or remote surgery. This delay can also be very unpleasant with interactive applications, such as VoIP, video conferencing, or other person to person communication. The functionality of live interactive access to a distant computer can also be subject to the problems caused by high latency. But, these problems are more tolerable for just basic email access and web browsing and in most cases are barely noticeable. <span style="font-size: 120%; font-family: Arial, Helvetica, sans-serif;"><span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">There is quite difficult to get around this problem. The delay is primarily due to the speed of life being 299,792.458 km/second (186,282.397 miles per second) in a vacuum. Even if all other signaling delays could be eliminated it still takes the electromagnetic wave 466 milliseconds to travel from ground to the satellite and back to the ground, a total of around 70,811.136 km to travel from the source to the destination and about 141,622.272 km for a round trip (user to ISP, and then back to user). Factoring in normal delays from other network sources gives a typical connection latency of 500–700ms. This is far worse latency than even most dial-up modem users' experience, at typically only 150–200ms total latency. <span style="font-size: 120%; font-family: Arial, Helvetica, sans-serif;"><span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">A proposed alternative to the geostationary relay is a special solar-powered ultralight airplane, 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. Onboard batteries would charge from solar panels covering the wings during the daylight hours, and would provide power to the plane during the night. Ground-based satellite dishes would relay signals off the plane, resulting in a greatly reduced roundtrip signal latency of only 0.12 milliseconds.

__**<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">CONCLUSION **__<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;"> The satellite internet service was launched to provide users access the internet via satellite although they are in rural area. It offers some value-added features without any phone line or dial up. The hardware needed includes a satellite dish antenna and a transceiver (transmitter/receiver) that operates in the microwave portion of the radio spectrum. There are three types of satellite internet which are known as two-way satellite-only communication; one-way receive, with terrestrial transmit; and one-way multicast, receive only. However, this internet service is only provided in limited area. The latency is also one of the problems for the user to access the internet with this service. The delay occurs due to the distance between satellite and the antenna on the Earth make this services unpleasant to the users.

__**<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">REFERENCES: **__<span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;"> 1. www.wikipedia.com 2. www.howstuffworks.com 3. www.drdish.net 4. www.lyngsat.com 5. <span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;">http://www.elitesat.com/ <span style="font-size: 110%; font-family: Arial, Helvetica, sans-serif;"> 6. Dennis Roddy, 1996, International Edition, Satellite Communications. Singapore: McGraw-Hill 7. Tri T. Ha, 1990, Second Edition, Digital Satellite Communications. Malaysia: McGraw-Hill