ITU-T G.707 155520 kbit/s (STM-1) interface

Frame formats, multiplexing, definitions

The following figure demonstrates the multiplexing structure and section layers of SDH. Structure provides the multiplexing and mapping of the ATM cells both the European (2..140 Mbit/s) (SDH), and American (1.5 .. 44 Mbit/s) (SONET) G.702 PDH signal stream of hierarchy:



ATM --->----+                                       SDH
      +---+ |                                  +----+ +----+ +---+ +-----+
      |C-4| +-------------->-------------------|VC-4|-|AU-4|-|AUG|-|STM-N|->
140  >|   |-|-------------->-------------------|    | |    |+|   | |     |
Mbit/s+---+ |                                 +|    | +----+||   | |STM-1|
            |                                 3+----+       |+---+ +-----+
      +---+ | +----+ +----+            +-----+|             |
44    |C-3| +-|VC-3|-|TU-3|>-----------|TUG-3|+             3
(34) >|   |--+|    | |    |            |     |              |
Mbit/s+---+ ||+----+ +----+          +-|     |     SONET    |
            ||                       7 +-----+ +----+ +----+|
            |+------------->---------|---------|VC-3|-|AU-3|+
      +---+ | +----+ +----+   +-----+|  +--7---|    | +----+
      |C-2| +-|VC-2|-|TU-2|>--|TUG-2|+  |      +----+|   + pointer         |
6    >|   |-|-|    | |    |   |     |   |        |   |     állítás         |
Mbit/s+---+ | +----+ +----+ +-|     |---+        |   |                     |
            |               3+|     |            |   |                     |
      +---+ | +----+ +----+ ||+-----+            |   |                     |
      |C12|---|VC12|-|TU12|>+|                       |                     |
E1 2 >|   | +-|    | |    |  |                   |   |                     |
Mbit/s+---+ | +----+ +----+  4                   |   |                     |
      +---+ | +----+ +----+  |                HOVC   |                     |
DS1   |C11| +-|VC11|-|TU11|>-+             Higher    |                     |
1.5  >|   |---|    | |    |                Order     |                     |
Mbit/s+---+   +----+ +----+                Virtual   |                     |
     |      |   |   |   + pointer         Container  |                     |
  circuit  PDH  |  SDH    állítás                   SDH          Transmission
   layer  path  |  Lower                            Higher       media (physical)
          layer |  Order                            Order        layer
                |  Path                             Path
                |  layer                            layer
                |
               LOVC
              Lower
              Order
              Virtual
              Container

Definitions:

SDH-PDH comparision:
PDH -> numerous hierarchy levels, numerous bit rates
             multiplexing technique: rate equalization

Advantages of the synchronous digital multiplexing and the connecting synchronous digital hierarchy:
    - more simple mutiplexing/demultiplexing technique
    - indirect access to the tributaries with smaller rate 
    - enhanced Operations Administrations and Maintenance (OAM) capabilities.
    - upgradeability towards higher bit rates