26-05-2012, 04:58 PM
Integrated Services Digital Network (ISDN)
Integrated Services Digital Network.pdf (Size: 81.2 KB / Downloads: 256)
Evolution of ISDN (1)
• Integration
– Before WWII, integration of telegraph/telex
and voice
– More recently, integration of fax and voice
– ISDN objective: integrate digital voice, 64-
kbps data, telex, fax, slow-scan video
– Broadband ISDN (BISDN): all of the above
plus video, multimedia, …
Evolution of ISDN (2)
• Channel
– Analog public switched telecommunications
network based on the 4-kHz voice channel
– Present digital network based on PCM: 64-
kbps voice channel
– In-channel signaling and framing corrupted
the 64-kbps channel, so integration of data
required a drop-back to 56-kbps
– ISDN : local interface to a “digital pipe”
enables higher data rates
Principles of ISDN (1)
• Support of voice and non-voice applications in
the same network
– interfaces and data transmission facilities
standardized by ITU-T
• Switched and non-switched connections
– packet & circuit switching, leased lines
• 64-kbps channel
– chosen because at the time was the standard
rate for digitized voice
Principles of ISDN (2)
• Layered protocol structure
– mapped into OSI model (advantages in
utilizing existing standards as well as in
developing new ones)
• Variety of configurations
– according to specific national situations &
state of technology
Lecture Summary
• ISDN supports a wide range of voice and non-voice
applications in the same network. It provides a range of
services using a limited set of connection types and
multi-purpose user-network interface arrangements.
(From Recommendation I.120 - 1988)
• ADSL transforms ordinary phone lines into high-speed
digital lines for fast Internet access, interactive
multimedia applications, telecommuting, video on
demand, etc. (From ADSL Forum)