Chapter 6. Interactive Television

Reference: B. Furht, et al., "Design Issues for Interactive Television Systems", IEEE Computer, Vol. 28, No. 5, pp. 25-39, 1995
Reference: "The trial and Travails of INTERACTIVE TV", IEEE Spectrum, pp. 22-28, April 1996.

Basics of Interactive TV
Some Competing Solutions
Set-top Box

6.1. Basics of Interactive TV

Beside the normal services provided by the current telephone and cable services, Interactive TV will provide a variety of new services to homes, such as:

• video-on-demand
• home shopping, banking
• interactive single/multiple player games
• interactive entertainment
• digital multimedia libraries
• electronic newspapers, magazines, yellow pages, etc.

Telephone Network:

+: High availability, security. Good support for interactive/two way traffic
-: Low band width

Cable Network:

• Analog video down the wire

  +: High band width
  -: Little infrastructure for long-distance, low security, harder for two way traffic

6.2. Some Competing Solutions

Telephone Company Solutions

1. The ADSL (Asymmetric Digital Subscriber Line) by Bell Atlantic:
2. Wireless Cable
   
   • Remotely, signals transmitted via satellites at 4 GHz. Regionally, from mountain-top towers at 2.1-2.7 GHz microwave band, with a total of 33 analog 6 MHz channels.
   • Itself addresses the bandwidth problem, not interactive

3. FTTC (Fiber To The Curb)
   
   • Optical fiber to each residential neighborhood, terminating in ONU (Optical Network Unit).
   • Each ONU supports up to 16 copper local loops that can run full-duplex T1 or T2 for MPEG-1 and MPEG-2 respectively.

4. FTTH (Fiber To The Home)
   
   • BERLU (Broadband Enhanced Remote Line Unit) -- SONET-based VOD developed by GTE in Cerritos, California
     
   • High capacity broadband switches -- multiple of 51.84 Mbps

Cable Company Solutions

• HFC (Hybrid fiber coax)
  
  • Analog signal. Digital transmission is via QAM (quadrature amplitude modulation)
  • Backbone is digital network (SONET with ATM)
  • forward path: 50-750 MHz, reverse path: 5-30 MHz

• Cable Modem
  
  • capable of providing 10-100 Mbps,
    e.g., Motorola CyberSURFR -- 10 Mbps per user downstream and 768 kbps return upstream

• "500-Channel" Scenario:
  
  • 70 broadcast analog and digital HDTV channels (each 6 MHz, total ~450 MHz), and
  • 430-plus Switched Digital Video channels (compressed MPEG-2 movies)
    [transmitted through 50 analog 6-MHz channels, each channel is capable of sending eight to ten 3.35 Mbps MPEG-2 movies via QAM.]

6.3. Set-top Box

Functions: (a) Decodes the information, (b) provides interactiveness

A figure on the STB (Set-top Box) from Furht, et al.