Data Broadcasting

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Data Broadcasting

• Ken McCann

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Application Example - Internet via satellite
Delivery of web pages at up to 38 Mbit/s
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DVB Return Channel

• Return channel used for interactive services
  depends on the physical network, e.g.
• Telecom modem via PSTN ISDN for terrestrial or
  satellite TV
• DVB/DAVIC modem for cable TV

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DVB Data Broadcasting

• DVB Data Broadcasting standard, EN 301 192,
  provides a set of network-independent protocols
  optimised to different applications
• data piping
• data streaming
• multiprotocol encapsulation
• data carousel
• object carousel

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DVB Data Piping
0 1 0 0 1 1 0 0 1 0
1 0 1 1 0 0 1 0 1 1
0 1 0 0 1 1 0 0 1 0

• DVB Data Piping uses MPEG Transport Stream (TS)
  packets without any intermediate layer
• provides non-synchronised end-to-end delivery of
  data through DVB networks
• 188 byte packets with 184 byte payload
• DVB descriptor to identify data pipe
• Any other mechanism relies on the application

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DVB Data Streaming
Audio
Data
Video

• Based on the MPEG Packetised Elementary Stream
  (PES) construct that is used for video and audio
• Asynchronous data streams carry no timing
  information (e.g. RS232)
• Synchronous data streams allow clock and data to
  be regenerated (e.g. E1, T1)
• Synchronised data streams allow playback in sync.
  with video and audio

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Multiprotocol Encapsulation

• Based on the MPEG section construct that is used
  for MPEG PSI and DVB SI
• optimised for Internet Protocol (IP) but can be
  used for any other network protocol
• datagrams can be fragmented into multiple
  sections if they exceed maximum payload of a
  single section (4080 bytes)

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Data Carousel

• Based on the MPEG Digital Storage Media Command
  and Control (DSMCC) data carousel
• supports cyclic transmission of data modules to
  receivers
• analogous to traditional Teletext
• data is structured into Modules, Groups and
  SuperGroups
• could be used for software download to receivers

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Object Carousel

• Based on the MPEG DSMCC object carousel
• supports cyclic transmission of structured groups
  of objects from broadcast server to client
  (receiver)
• can download application, data files, data
  streams and trigger events
• typically used to provide interactive services

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Conclusions

• DVB data broadcasting specification provides a
  comprehensive set of network-independent
  protocols
• capacity for data broadcasting can be traded
  against capacity for video and audio in a totally
  flexible manner