Direct Broadcast Satellite (DBS) Television

Direct Broadcast Satellite (DBS) Television

• DBS provides broadcast transmissions to a large area of the earth using antenna footprints
• DBS services include audio, television, and Internet services
• Direct broadcast television is digital TV, which is the subject of this chapter

History of DBS

• The concept of using satellites for direct transmissions into the home has been around for many years
• A comprehensive overview of DBS in Europe, the United States, and other countries can be found in Prichard and Ogata (1990)

Orbital Spacing

• The orbital spacing for high-power satellites is 9°, which eliminates adjacent satellite interference
• The DBS orbital positions and transponder allocations for the United States are shown in Fig. 16.1

DBS Orbital Positions

• Clusters of satellites occupy the nominal orbital positions
• Examples of satellites located at 119°W longitude include EchoStar VI, EchoStar IV, EchoStar II, and EchoStar I

Signal Processing

• Data signals and audio broadcast material are converted to a uniform digital format, compressed, and time division multiplexed
• The program guide and conditional access are added to the multiplexed stream
• FEC is added to the bit stream, which is then used to QPSK modulate the carrier for a given transponder

Uplink Facilities

• Uplink facilities are concentrated at single locations specific to each broadcast company
• The uplink facilities for Echostar's DISH network are shown in Fig. 16.9
• The four uplink facilities in operation as of 1996 are shown in Table 16.3

High Definition Television (HDTV)

• The 18 advanced television systems committee (ATSC) formats for digital television include HDTV
• Analog TV transmissions in the U.S. are scheduled to shut down by January 1, 2009
• Set-top boxes can convert HDTV signals to a format suitable for analog sets, but the high resolution and other advantages of digital TV will be lost in this process