8 Multiuser channels

8 Multiuser channels

1. 8.1 Multiplexing

   • The access to the transmission media is controlled by a central entry point gathering the information from the different contributors and formatting them in a way that allows transmission of these independently through a shared system
   • 8.1.1 Frame synchronization
     • 1. Search for the sync word in a stream of digital symbols
     • 2. Check that synchronization has not happened to an imitation
     • 3. Indicate that the system is synchronized
     • 4. Check that synchronism is maintained
   • 8.1.2 Information about system status
     • Status information from the systems are very important for keeping the network functioning.
   • 8.1.3 Bit synchronization of multiplex systems
     • Decentralized clock generators
       • The clock signals are produced in different locations.
     • Central clock generator
       • The clock signal is generated in a single location and all equipment follows this clock as “slaves”.

2. 8.2 Time multiplexing - PDH

   • 8.2.1 ITU-T's 1st order time multiplex system
   • 8.2.2 ITU-T's 2nd order time multiplex system

3. 8.3 Time multiplexing - SDH

4. 8.4 Multiple access principles

   • FDMA (Frequency Division Multiple Access)
     • The users operate in separate parts of a frequency band and bandpass filters keep them separated.
   • TDMA (Time Division Multiple Access)
     • The users use the channel at separate time periods, time slots.
   • TDMA with carrier sense and collision detection
   • CDMA (Code Division Multiple Access)

5. 8.5 User-Network Interface for ISDN

   • 8.5.1 Protocols and reference models
     • OSI reference model
       • Physical layer
       • Data link layer
       • Network layer
       • Transport layer
       • Session layer
       • Presentation layer
       • Application layer
   • 8.5.2 Reference configurations
   • 8.5.3 Placement of terminals
   • 8.5.4 Physical characteristics of the S/T-interface
   • 8.5.6 ISDN layer 2