SDH multiplexing process
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SDH provides for multiplexing of 2-Mbit/s (C-12) and 34-Mbit/s (C-3) signals into an
STM-1 frame.
Furthermore, multiplexing paths also exist for the SONET specific 1.5-Mbit/s, 6-Mbit/s
and 45-Mbit/s signals.
Process
The following describes the process for multiplexing a 2-Mbit/s signal. The “SDH
digital multiplexing” (p. A-11) illustrates the multiplexing process.
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1
Input 2-Mbit/s tributary is mapped
• Each VC-12 carries a single 2-Mbit/s payload.
• The VC-12 is aligned into a Tributary Unit TU-2 using a TU pointer.
• Three TU-2 are then multiplexed into a Tributary Unit Group TUG-2.
• Seven TUG-2 are multiplexed into an TUG-3.
• Three TUG-3 are multiplexed into an VC-4.
• The VC-4 is aligned into an Administrative Unit AU-4 using a AU pointer.
• The AU-4 is mapped into an AUG which is then mapped into an STM-1 frame.
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2
After VCs are multiplexed into the STM-1 payload, the section overhead is added.
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3
Scrambled STM-1 signal is transported to the optical stage.
An SDH overview
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A-14
Alcatel-Lucent - Proprietary
See notice on first page
365-312-801R7.2
Issue 3, May 2007
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