LINE APPLICATIONS

LINE APPLICATIONS WITH TERMINAL MULTIPLEXERS & A/D MUX


SDH MULTIPLEXING PRINCIPLES
The SDH multiplexing structure accommodates the mapping and multiplexing of
 higher order plesiochronous tributary rates into a synchronous signal. The basic
synchronous transmission rate 155.52Mbit/s,which is organized in frames each
designated a Synchronous Transport Module(STM).Higher bitrates of
N*155.52Mbit/s are obtained by multiplexing N subscribers into oneSTM-N signal.
It shows the SDH multiplexing structure.
The figure comprises the different multiplexing elements which are defined
according to their functional level.
The C-12 container is a defined unit of payload capacity ,for carrying 2Mbit/s
signals.
The VC-12 comprises a C-12 plus path overhead including information about the
origin of the path and a bit interleaved parity over the VC-12 for subsequent error
performance monitoring.
Within the defined time slot the VC-12 can drift if the VC-12 and the
corresponding C-4 phase/freq. are not the same .This is accounted for by adding
the TU-12 pointer at a defined place in the C-4 container .The TU-12 pointer
points at the start of the VC-12 container.
TUG-2 and TUG-3 describes the multiplexing into the C-4 container.
63 VC-12s can be multiplexed into one C-4.The C-4 container is a defined
unit of payload capacity for carrying one 140Mbit/s signal or 3 TUG-3s.
The Virtual Container (VC-4) comprises a single C-4,including
information about the origin of the path and a bit interlesved parity over the VC-4
for subsequent error performance monitoring.


MULTIPLEXING
An Administrative Unit (AU) comprises a VC-4 together with a AU-pointer
.The AU-pointer allows the VC-4 to drift within the STM-1frame.
The AU Group (AUG) is identical to the AU-4 in the described multiplexing
structure.
A Synchronous Transport Module (STM) comprises AUGs together with
system information (Multiplexer and Regenerator Section Overhead
MSOH/RSOH).
The STM-1 frame is repeated with 8K giving a line speed of the bit serial data
stream of 155.52Mbit/s.
Four AUGs can be multiplexed into an STM-4 which together with SDH
has a bit rate of 622.8Mbit/s.16 AUGs can be multiplexed into a STM-16 , which
together with SDH has a bit rate of 2.488Gbit/s.
AUG into structure provide adaptation between high order path later and
multiplex section layer. It consist payload information.