Satellite TV

Satellite TV broadcasting is above the equator by setting a geosynchronous satellite, first receive ground television through the TV signal satellite ground stations launch, and then forward it to the earth in the designated area, by ground equipment for television watching receiving. Use this way realization of TV broadcast called satellite TV broadcasting.

Satellite TV is introduced

Digital satellite television is developed rapidly in recent years, use geostationary satellites will digital coding compression TV signal transmission to the client a radio and TV form. There are two major kinds of ways. One kind is digital TV signals to the cable television front, again by cable television converted into analog television transmitted to users at home. This form has to popularize and apply in the countries all over the world for years. Another way is to digital television signal transmitted directly to the users Home namely: Direct DTH) way to Home (. U.S. Direct TV company is the first application of this technology satellite TV operation company. Compared with the first way, DTH way satellite launch big power, usable smaller antenna, average household can use. Meanwhile, can directly provide user authorization and encryption management, conduct digital television, for pay-per-view TV (PPV), HDTV, and other types of advanced TV service, do not suffer intermediate link restrictions. Besides DTH ways also can carry out many TV service other than digital information service, such as the INTERNET high-speed download, interactive television, etc. DTH standards?

Satellite TV features

(1) in its coverage area, and can have a lot of line, direct, and each ground contacts and transmit information;

(2) it with various sites communications from distance limit, its technical performance and operation cost nor the distance influence;

(3) satellite and sites of contact, can provide line according to the actual needs, because satellite itself has many lines can be connected to any two sites.

In international DTH are two big standards, European standards dvb-s and American standards DigiCipher. But in the global DVB standard gradually widely, the U.S. lodging a DTH company also used the phrase DVB standards.

DTH system

A typical DTH system consists of six parts:

1) front-end system (Headend)

Front-end system mainly consists of video audio compression encoders, multiplex etc. A front-end system of main task will be to TV signal digital coding compression, using statistical multiplexing technique, in limited satellite transponders band to send more programs. DTH press mpeg-2, standard for video audio signal compression with dynamic statistical multiplexing technique, in a 27MHz, send up the transponders 10 sets of TV program.

2) transmission and Uplink systems (Uplink)

Transmission and uplink systems ranging from front to uplink stood communications equipment and uplink devices. Transmission ways mainly have the intermediate frequency transmission and digital frequency-hand mode two kinds.

3) Satellite (Satellite)

DTH systems with high-power live satellite or communications satellite. Due to technical and cause such as cost, some DTH system USES high-powered communications satellite, American and Canadian DTH company adopted is more appropriate for the special high-power live satellite (DBS).

4) user management system (SMS)

User management system is the heart of DTH system, mainly complete the following functions: a. the registration and management of user data.

B. buy and packaging program. Satellite TV receiving devices (9 zhang)

C. record fee standards and formulate program charge users.

D. market forecast and marketing.

User management system mainly by the user information and program information database management system and answer user problems, and provides various customer service Call Center constitutes.

5) conditional access system (CA)

Conditional access system has two main functions:

A. to program data encryption.

B. authorized users and for the program.

The international DTH system used by the conditional Access system mainly has: the United States, France, Israel Irdeto NDS Via Access, Switzerland

Nagra Vision, etc.

The United States and using Direct TV company Direct TV technology companies use Choice of Canada's Star NDS conditional access system; The United States a phrase Echostar) company and use (Bell ExpressVu Echostar technology of Canadian companies use is Nagra Vission conditional access system.

6) user access system (IRD)

DTH users by the receiving system with a small satellite receiving antenna (saucer-shaped phrase) and comprehensive receiving decoder (IRD) and Smart Card (Smart) of hello.

IRD responsible for four major functions:

A. decoding program data flow, and the output to television.

B. the Key (Key specific using smart CARDS) decryption.

C. receiving and dealing with various kinds of user commands.

D. to download and run all kinds of application software.

The IRD DTH system already is not a simple hardware device, it also includes operating system and a number of software applications. At present more successful IRD operating system is Open TV. The United States has started a company phrase for the IRD user escalating TV Open system.