1) Direct-broadcast satellite (DBS) transmits satellite television signals for home reception and involves programming sources, broadcast centers, satellites, satellite dishes, and receivers. 2) Error correction in DBS uses interleaving and de-interleaving to improve burst error correction by distributing errors across codewords. 3) MPEG standards including MPEG-1, MPEG-2, and MPEG-4 are used for audio and video compression and transmission, with MPEG-2 widely used for digital television broadcast by satellite, cable, and terrestrial television systems.

1. Submitted by
Arpit shukla
1312231039
Srmcem lucknow

2. • Direct-broadcast satellite (DBS) is a type of artificial satellite which
usually sends satellite television signals for home reception.
• All in all we can say that it is a method of receiving satellite television
by means of signals transmitted from direct-broadcast satellites.
Introduction

3. Overview of working
Mainly five components are there –
the programming source
the broadcast center
the satellite
the satellite dish
the receiver.

4. The working bands of DSB : the c and ku band
•C-Band
• DIRECTV (Ku-Band + Ka-Band)
• DISH (Ku-Band)
•Globe Cast World TV (Ku-Band)
At present time, there are 4 commercially available satellite television
technologies

5. DIGITAL DSB TV (receiver)

6. ERROR CONTROL IN DSB
Interleaving and de-interleaving -
Interleaving is frequently used in digital communication and storage
systems to improve the performance of forward error correcting codes.
13-17 Error correction
23-27 For digital data

7. interleaving is widely used for burst error-correction.
Transmission without interleaving
Error-free message: aaaabbbbccccddddeeeeffffgggg
Transmission with a burst error: aaaabbbbccc____deeeeffffgggg

8. With interleaving:
Error-free code words: aaaabbbbccccddddeeeeffffgggg
Interleaved: abcdefgabcdefgabcdefgabcdefg
Transmission with a burst error: abcdefgabcd____bcdefgabcdefg
Received code words after deinterleaving: aa_abbbbccccdddde_eef_ffg_gg
In each of the codewords aaaa, eeee, ffff, gggg, only one bit is altered,
so one-bit error-correcting code will decode everything correctly
Disadvantages of interleaving
Use of interleaving techniques increases total delay. This is because the
entire interleaved block must be received before the packets can be
decoded.

9. The Moving Picture Experts Group (MPEG) is a working
group of authorities that was formed by ISO and IEC to set
standards for audio and video compression and transmission
MPEG has standardized the following compression formats
and ancillary standards:
•MPEG 1
•MPEG 2
•MPEG 3
•MPEG 4
MPEG

10. MPEG 2
MPEG-2 is widely used as the format of digital television signals that are
broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite
TV systems. It also specifies the format of movies and other programs that
are distributed on DVD and similar discs
. MPEG-2 removes both the temporal redundancy and spatial redundancy which are
present in motion video.
Temporal redundancy arises when successive frames of video display images of
the same scene. It is common for the content of the scene to remain fixed or to
change only slightly between successive frames.
Spatial redundancy occurs because pats of the picture (called pels) are often
replicated (with minor changes) within a single frame of video.

12. BASIC OPERATION OF ENCODER
MPEG-2 includes a wide range of compression mechanisms. An encoder must
therefore which compression mechanisms are best suited to a particular scene /
sequence of scenes. In general, the more sophisticated the encoder, the better it is
at selecting the most appropriate compression mechanism, and therefore the
higher the picture quality for a given transmission bit rate. MPEG-2 decoders also
come in various types and have varying capabilities (including ability to handle
high quality video, ability to cope with errors) and connection options.

13. Encoder and decoder of mpeg

14. Motion vectors are parsed from the data stream and fed to the motion compensator.
Quantized DCT coefficients are fed to the inverse quantizer and then to an IDCT
circuit that transforms them back to the spatial domain. For P and B pictures, motion
vector data is translated to a memory address by the motion compensator to read a
particular macroblock (predicted macroblock) out of a previously stored reference
picture. The adder adds this prediction to the residual to form reconstructed picture
data. For I pictures, there are no motion vectors and no reference picture, so the
prediction is forced to zero. For I and P pictures, the adder output it is fed back to be
stored as a reference picture for future predictions.

15. ADVNTAGES
•allows storage and transmission of movies using currently
available storage media and transmission bandwidth
•better coding quality at higher data rates in comparison with
MPEG 1
•often used to create movies to be distributed over the internet
•offers resolutions of 720x480 and 1280x720 at 60 fps, full CD-
quality audio
•significant requirements for computer encoding
DISADVANTAGE
The error correcting procedure is long
Video compression is not highly efficient for high definition

16. The trends

17. Conclusion
•DBS seems most appealing to persons who either are
disenchanted with cable television or who live in areas
that are not served by cable.
•DBS-TV systems operate with small antennas and low
cost receiving systems, and offer a very large number of
video and audio channels, making them attractive to
customers.
•Delivery of bit stream through a direct broadcast
satellite can be adapted to serve Internet users who
require the download of large blocks of data.

18. THANK YOU