The prospect of the Internet as the fastest growing satellite communication application coupled with satellite-based multimedia networks has generated a high level of interest in the performance of TCP over satellite systems

This article presents the network architecture for supporting TCP/IP based services over satellite.

It discusses the key factors that influence TCP performance over satellite links, and compares the advantages and disadvantages of low earth orbit and geostationary satellites.

It is having the feasibility of using Low Earth Orbit satellites to support and expand the Internet.

This topic gives us brief idea about the TCP behaviour over a Geostationary satellite system and LEO satellite constellation based on computer simulations, where two typical Internet applications are taken into consideration : FTP file transfer and Web browsing

DESIGN OF THE ENTIRE SYSTEM

With its ability to cover large area including geographically isolated regions, the satellite based links have a bright future.

A number of commercial satellite systems have been proposed which target multimedia services, as illustrated . These systems are based on both geostationary earth orbit (GEO) and low earth orbit (LEO) satellite networks.

With a shortage of broadband terrestrial connections in many areas of the world, particularly in remote or rural areas where physical lines are costly to install and operate, satellites can be used to complement terrestrial networks, extending them with flexible and immediate wide coverage.

Low earth orbit(LEO) and Geostationary orbit satellites (GEO) are used to provide the satellite links.

LOW EARTH ORBIT SATELLITE :-

A low Earth orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 160 - 2,000 km (100 - 1,240 miles) above the Earth's surface

LOW EARTH ORBIT

(Leo)

Geostationary Satellite :-

A geosynchronous satellite is a satellite whose orbital track on the Earth repeats regularly over points on the Earth over time. If such a satellite's orbit lies over the equator and the orbit is circular, it is called a geostationary satellite.

The orbits of the satellites are known as the geosynchronous orbit and geostationary orbit. Another type of geosynchronous orbit is the Tundra Elliptical Orbit.

Geostationary orbit satellites

Having lower altitude, LEO satellites can be used to provide a satellite network with much lower time delays and propagation losses.

It is also possible to achieve truly global coverage with a network based on LEO satellites with polar orbits.

The use of LEO satellite constellations enables designers to minimize power in both satellites and user terminals, minimize satellite antenna size, minimize the time delay or latency for a two-way signal , and maximize the angle of elevation.

Disadvantages of LEO :-

The orbital period is very short (around 100 minutes) and a given satellite is in view for only a few minutes before hand-off of a call to another satellite

Coverage area and no of satellites :-

In order to provide continuous and global coverage, a large number of satellites are required as the coverage area for a single satellite is very less compared to GEO.

Examples of such LEO constellations are Teledesic and Iridium with 288 and 66 operational satellites, respectively. The satellites have to be maintained in constant position in the constellation for providing constant connectivity which is a major challenge.

Handoff :-

When one satellite moves out of sight, other has to be switched to provide services.

Handoff techniques are provided for this purpose.

Inter satellite link:-

Inter satellite links (ISLs) are often implemented within LEO constellation.

These ISLs allow users from different satellite footprints to communicate with each other.

They also allow the system to provide large geo-graphical coverage without having to deploy large numbers of gateway stations.

THANQ