User:Santoshverma05/sandbox

Satellite Communication Overview:

1. Introduction to Satellite 

The word satellite originated from the Latin word “Satellit”- meaning an attendant, one who is constantly hovering around & attending to a “master”. For our own purposes however a satellite is simply any body that moves around another (usually much larger) one in a mathematically predictable path  called an orbit. A communication satellite is a microwave repeater staion in space that is used for tele communcation, radio and television signals. The first man made satellite with radio transmitter was in 1957. There are about 750 satellite in the space, most of them are used for communication.

Satellites offers a number of features not readily available with other means of communications.Because every large area of the earth are visible from a satellite,the satellite can for the star point of a communications net linking togather many users simultaneously, users who may be widely separated geographically.

A feature of any satellite system is that the cost is distance insensitive, meaning that it costs about the same to provide a satellite communications link over a short distance as it does over a large distance.Thus a satellite communications system is economical only where the system is in continuous use and the costs can be resonably spread over a large number of users.

2. Frequncy Allocations for Satellite Services

Allocating frequncies to satellite services is a complicated process which requires international coordinations and planning. This is carried out under the auspices of the International Telecommunication Union (ITU).To facilitate frequncy planning, the world is divided into three regions.


 * Region 1 : Europe,Africa,Soviet Union and Mongolia.


 * Region 2 : North and South America and Greenland.


 * Region 3 : Asia ,Australia and the south west Pacific.

Within these regions, frequency bands are allocated to various satellite services.

Some of the services provided by satellites are :


 * Fixed Satellite Service (FSS)


 * Broadcasting Satellite Services (BSS)


 * Mobile Satellite Service (MSS).


 * Navigational Satellite Service (NSS).


 * Metrological Satellite Service (MSS).

FSS provides links for existing telephone networks as well as for transmitting television signals to cable companies for distribution over cable systems.

BSSs are intended mainly for direct broadcast to home i.e., DBS -Direct Broadcast satellite services, in Europe it's popularily known as DTH (Direct to Home) service.

MSS include land mobile, maritime mobile and aeronautical mobile.

NSS include global positioning systems.

MSS often provide a search and rescue services.

INTELSAT


 * INTELSAT stands for International Telecommunications Satellite. created in 1964 and currently has over 140 member countries and more than 40 investing entities (see http://www.intelsat.com/ for more details).


 * In July 2001 INTELSAT became a private company and in May 2002 Starting with the Early Bird satellite in 1965, a succession of satellites has been launched at intervals of a few years.


 * For international traffic, INTELSAT covers three main regions—the Atlantic Ocean Region (AOR), the Indian Ocean Region (IOR), and the Pacific Ocean Region (POR) and what is termed Intelsat America’s Region.


 * For the ocean regions the satellites are positioned in geostationary orbit above the particular ocean, where they provide a transoceanic telecommunications route.


 * The INTELSAT VII-VII/A series was launched over a period from October 1993 to June 1996. The construction is similar to that for the V and VA/VB series in that the VII series has solar sails rather than a cylindrical body.


 * The VII series was planned for service in the POR and also for some of the less demanding services in the AOR.


 * The lifetime of these satellites ranges from 10 to 15 years depending on the launch vehicle. Recent figures from the INTELSAT Web site give the capacity for the INTELSAT VII as 18,000 two-way telephone circuits and three TV channels; up to 90,000 two-way telephone circuits can be achieved with the use of “digital circuit multiplication.”


 * The INTELSAT VII/A has a capacity of 22,500 two-way telephone circuits and three TV channels; up to 112,500 two-way telephone circuits can be achieved with the use of digital circuit multiplication.


 * As of May 1999, four satellites were in service over the AOR, one in the IOR, and two in the POR.


 * The INTELSAT VIII-VII/A series of satellites was launched over the period February 1997 to June 1998. Satellites in this series have similar capacity as the VII/A series, and the lifetime is 14 to 17 years.


 * It is standard practice to have a spare satellite in orbit on high reliability routes (which can carry preemptible traffic) and to have a ground spare in case of launch failure.


 * Thus the cost for large international schemes can be high; for example, series IX, described later, represents a total investment of approximately $1 billion.


 * Latest satellites provide a much wider range of services than those available previously, including such services as Internet, DTH TV, tele-medicine, tele-education, and interactive video and multimedia.


 * It may be noted that one 36 MHz transponder is capable of carrying about 9000 voice channels, or two analog TV channels, or about eight digital TV channels.


 * In addition to providing transoceanic routes, the INTELSAT satellites are also used for domestic services within any given country and regional services between countries. Two such services are Vista for telephone and Intelnet for data exchange.

U.S. Domsats

* high power, * medium power * low power (Reinhart, 1990).
 * Domsat is an abbreviation for domestic satellite. Domestic satellites are used to provide various telecommunications services, such as voice, data, and video transmissions, within a country.
 * They make available a wide selection of TV channels for the home entertainment market, in addition to carrying a large amount of commercial telecommunications traffic.
 * U.S. Domsats, which provide a DTH television service, can be classified broadly as

Prepared by : Santosh Kumar Verma BITS ID : 2014HZ97005