ISDN      

• Integrated Services Digital Network
•  supports a wide range of voice and non voice applications ( telephony, data, text, image) in the same network.

 ISDN STANDARDS: I Series (1988)

 ISDN SERVICES

1. Bearer Services - provides means to convey information ( speech, data) between users in real time and without alteration of the content
2. Teleservices - combine transportation function with the information processing function( example telephony,teletex,videotex) .It employs bearer services to transport data and provide set for high level functions ( OSI 4 to 7)
3. Supplementary Services-one that can be used with conjunction with one or more bearer or teleservices. Examples include multiparty, reverse charging ,call forwarding)

TRANSMISSION CHANNELS

      Basic Access = 2B + D (192 Kbps)

      Primary Access = 23B + D (1.544 Mbps) ( USA, Japan)

                              = 30B + D (2.048 Mbps) (Europe)

 USER TO NETWORK INTERFACE

NT1 (Network Termination 1) 

• includes functions that may be regarded as belonging to OSI layer 1

NT2(Network Termination 2)

• an intelligent device that may include up to OSI layer 3

TE1(Terminal Equipment 1)

• refers to devices that support standard ISDN interface
• example ( digital telephone, digital fax)

TE2 (Terminal Equipment 2)

• encompasses existing non ISDN equipment
• terminals with a physical interface such as RS-232 or host computer with X.25
• such terminals need TA

TA (Terminal  Adapters)

• allows non ISDN devices to connect to ISDN

LINE ENCODING

  For Basic and Primary User to Network Interface:

1. B8ZS (for North America basic line and 1.544 Mbps
2. HDB3 (for European and Japanese basic line and 2.048 Mbps primary line)

          Both are improved versions of BPRZ-AMI.

   For U Interface (ISDN to local loop interface):

     1.   2B1Q 

• 2 binary 1 quaternary
• 160 kbps
• more efficient use of bandwidth
• 4 voltage levels

DATA LINK CONTROL

   LAP-D ( Line Access Protocol- D Channel)

SS7 (Signaling System Number 7)

• set of specifications of services and protocols for use in the internal control of intelligence in a digital network
• common channel signaling
• specifically designed for ISDN

B-ISDN

 -Broadband Integrated Digital Network

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