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
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:
Telephone Company Solutions
- The ADSL (Asymmetric Digital Subscriber Line) by Bell Atlantic:
- 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
- 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.
- 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.]
Functions: (a) Decodes the information, (b) provides interactiveness
A figure on the STB (Set-top Box) from Furht, et al.
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