Analog and Digital Television Transmission Systems

Posted on Nov 30, 2024 in Electronics

Analog Television Process

  • Capture
  • Registration
  • Production
  • Transportation (Tx)
  • Reception (Rx)

Digital Television Process

  • Recording
  • Production
  • Transportation (Tx)
  • Reception (Rx)

Digital Transmission Mediums

  • Satellite
  • Cable
  • Web
  • Terrestrial Transmission

Advantages of Digital Transmission

  1. Efficient Bandwidth Administration
  2. Increased Noise Immunity (Tx)
  3. Component Video Transmission
  4. Increased Horizontal Resolution (Double Resolution)
  5. Progressive Scan Capability
  6. Increased Vertical Color Resolution
  7. HDTV Possibility
  8. Data and Other Services Transmission
  9. Support for Various Aspect Ratios (e.g., 16:9)
  10. Digital Audio
  11. Multi-channel Audio

Drawbacks of Digital Transmission

  1. Noise Measurement
  2. Compression Artifacts

Digital Reception Diagram

Antenna → RF Channel → Decoder → Video (Analog) → Display; Audio (Analog) → Speakers

Digital TV Services Worldwide

  1. ATSC (Advanced Television Systems Committee)
  2. DVB-T (Digital Video Broadcasting – Terrestrial)
  3. ISDB (Integrated Services Digital Broadcasting)

ATSC Standard Technical Characteristics

  1. 6 MHz Channel
  2. Modulation Subsystems:
    • 8 VSB (Over-the-Air Transmission)
    • 16 VSB (Cable Transmission)
  3. Service Versatility (19.3 Mbps)
  4. Audio & Video Services, Data Transmission

ATSC Video System Features

  1. MPEG-2 Compression
  2. Sampling: 4:2:0
  3. 8-bit Resolution
  4. Frame Types: I, P, B
  5. MP@ML (Main Profile at Main Level) for SD
  6. MP@HL (Main Profile at High Level) for HD
  7. Choice of SD and HD Formats
  8. All Receivers Must Decode All Standard Formats

Aspect Ratio

  • Screen Size
  • 16:9, 4:3

ATSC Audio Features

  1. Word Size: 16 to 24 bits
  2. Sampling Frequency: 48 kHz
  3. Bit Rate: 32 to 640 Kbps per Elementary Plot

8 VSB Modulation Subsystem Characteristics

  1. Single Carrier within a 6 MHz Channel
  2. Video, Audio, and Data Encoded in 8 Amplitude Levels, Modulating the Carrier in Vestigial Sideband
  3. Redundancy at Packet Level
  4. Reed-Solomon (207, 187, t=10)
  5. Inner-Code Redundancy
  6. Trellis 2/3
  7. Transmission Frame Mapped into 8 Levels, 1 Level per Symbol, 3 Bits per Symbol
  8. DC Level Added to Form a Pilot Signal for Carrier Acquisition

DVB-T Modes

  1. 2k Mode: 1705 Carriers (Suitable for Single Transmitter Operation with Small SFN Networks)
  2. 8k Mode: 6817 Carriers (Suitable for Single Transmitter and Large SFN Networks)

MPEG-2 MP@ML Compression Features

  1. Sampling: 4:2:0
  2. 8-bit Resolution
  3. Frame Types: I, P, B
  4. Variety of Resolutions

DVB-T Audio Compression

  • MUSICAM MPEG Layer 2
  • Dolby AC-3

COFDM Modulation Types

  • QPSK
  • 16 QAM
  • 64 QAM

ISDB

Designed for 6 MHz channels, supports 7 and 8 MHz.

ISDB-T Basic Models

  1. 2k Mode: 1405 Carriers (Suitable for Single Transmitter Operation with Small SFN Networks)
  2. 8k Mode: 2809 Carriers (Suitable for Transmitting Services to Mobile and Stationary Receivers)
  3. 4k Mode: 5617 Carriers (Suitable for Single Transmitter and Large SFN Networks)

Reed-Solomon Redundancy (221, 188, t=8)

Error correction system increasing redundancy bytes in a packet from 188 to 204-207 bytes (DVB, ISDB, ATSC) for error detection.

Bandwidth Division in a 6 MHz Digital Transmission System

Example: 19.3 Mbps Transfer Rate

  1. 1 HDTV Channel (18 Mbps)
  2. 1 HDTV Channel and 1 SDTV Channel (14 Mbps + 4 Mbps = 18 Mbps)
  3. 6 SDTV Channels (6 * 3 Mbps = 18 Mbps)

Technical Aspects for System Evaluation

  • Sensitivity
  • Carrier-to-Noise Ratio
  • Scope and Coverage
  • Fixed and Mobile Reception
  • Performance Against Ghosts and Multipath
  • Impulse Noise Immunity
  • Adjacent Channel Interference
  • Co-channel Interference
  • Transmitter Power
  • Margins and Spectrum Planning
  • Useful Bit Rate
  • High-Definition Video
  • Multichannel Audio
  • Bit Rate vs. Robustness
  • Multipath Immunity

Co-channel Interference Types

  1. Analog on Digital
  2. Digital on Analog
  3. Digital on Digital

Bit Rate – Robustness Relationship

Inverse relationship: Higher robustness means lower bit rate and vice versa.

Transmitter Power Determination

Factors:

  1. Scope or Coverage Area
  2. Reception Room to Absorb Propagation Variations
  3. Overcoming Co-channel and Adjacent Channel Interference
  4. Average Power to Peak Power Ratio

Multichannel Audio

  1. Analog
  2. Digital