Digital TV Standard

1
Digital TV Standard

• NOV,26,2002
• ???

2
Analog v.s. Digital TV
3
Introduction to Digital TV (1/3)

• What is Digital TV ?
• Access and display the TV programs with
  digital signals.
• Advantages
• Higher resolution than the conventional analog
  TV.
• Why?

4
Introduction to Digital TV (2/3)

• ATSC??????18?????
• ???????( HDTV High definition television )
• ????????( EDTV Enhanced definition television )
• ????????( SDTV Standard definition television )

5
Introduction to Digital TV (3/3)

• Advantages
• Better performance in audio quality.
• How?
• More efficient in bandwidth utilization.
• Additional services with data broadcasting.
• Special program coding.
• Video on demand.
• EPG ( electronic program guide ).
• The advantages of digital TV broadcasting system
  come from the channel coding and digital
  modulation!

6
Digital Terrestrial Television Broadcasting

• Digital TV programs can be transmitted by cable
  ,satellite ,terrestrial ,and wireless cable.
• Three terrestrial standard
• ATSC ( Advanced TV system committee )
• 1996,USA
• DVB-T ( Digital Video Broadcasting Terrestrial )
• 1997,European
• Adopted in Australia,New Zealand,Latin
  America,Singapore,
• Taiwan ( 2001,6 )
• ISDBT-T( Integrated Service Digital Broadcasting
  Terrestrial)
• 1999,Japan

7
DVB system scheme

8
Channel coding (1/3)

• Randomizer
• To avoid the unexpected results in the time
  recovery process of the receiver.
• Outer coder
• Reed-Solomon code
• With the error correcting capability to random
  noise.
• Outer Interleaver
• When burst error occurr.RS code becomes invalid
  in correcting.
• Interleaver divided the data in the same MPEG2
  packet into different packets.

9
Channel coding (2/3)

• Inner Coder
• To protect the data from serious noise and
  disturbance transmitting media.

10
Channel coding (3/3)

• Inner Interleaver
• ?????????????????(non-hierarchical)
  ???????(hierarchical) ??
• ??????????????????(bit interleaver)????(symbol)???
  ????????(symbol interleaver)
• ???????????QPSK (Quadrature Phase Shift
  Keying)?16-QAM (Quadrature Amplitude
  Modulation)?64-QAM??????
• ???????????????(mapping) OFDM?????????(sub-carrier
  )?

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MODULATION---OFDM

• Multi-Carrier Modulation
• Orthogonal sub-carriers with lower bit rate

12
MODULATION---OFDM

• OFDM?????????,?2k???1705?,?8k???6817??????,???????
  ????????????6MHz?7MHz?8MHz??????????????
• 1. ?????????????????(2?4?6?)
• 2.??????(TPS)?????????????????
• 3.????????????????????????????????,?????????
• (a)????8k???177?,2k???45?
• (b)????8k???524?,2k???131??

13
MODULATION---OFDM (continue)
14
ATSC v.s. DVB-T
15
ATSC v.s. DVB-T

• Frequency efficiency
• OFDM ---multi carrier modulation has more
  frequency efficiency than the single carrier
  modulation , VSB.
• For 6 MHZ channel
• DVB-T effective bandwidth5.7MHZ(5.7/695)
• ATSC effective bandwidth5.38MHZ(5.38/690)
• But the OFDM transmission system finally becomes
  the worse case in the frequency utilization.
• WHY?

16
ATSC v.s. DVB-T

• Multi-path interference
• ATSC receiver contains an adaptive equalizer to
  reduced the effects of multipath interference.
• DVB-T receiver contains a channel estimator which
  helps it reject interference such as multipath.
• The pilot signals and the time interval
  preserved are the main concern of the DVB-T,it
  makes the DVB-T system has advantages than the
  ATSC 8-VSB system in the multipath interference.

17
Conclusion

• DTV????????????????????
• ??????????????????????,??????????,??,???????????
• ???????????????,???????,?????,??????????????,???DV
  B-T??????????ATSC???,??????? DVB-T ??????????

18
References

• ????????? 2002,8
• http//www.dvb.com.tw
• http//www.wmr.com/html/Fact_about_DVB-T.htm
• ATSC Implementation Subcommittee Informational
  Document.
• Measurement guidelines for DVB system,ETSI TR 101
  290 v1.2.1(2001,5)