Concepts And Characteristics In Sdh Technology; Sdh Structure; Introduction - Siemens SRA 4 User Manual

1 - PRELIMINARY INFORMATION
1.4 CONCEPTS AND CHARACTERISTICS IN SDH

1.4.1 SDH structure

1.4.1.1
1-10
TECHNOLOGY
Given the application of novel concepts and characteristics used in SDH technology, the
following paragraphs contain general information regarding the synchronous hierarchy.
Signal processing in SDH equipment is carried out in accordance with ITU-T
Recommendations G.707 to G.709, G.781 to G.784 and G.957 to G.958.
The SDH is a hierarchically configured set of digital transport structures which have
been standardized to facilitate the transmission of payload signals in transmission
networks.
The basic digital structure of the SDH hierarchy is formed by the frame of the so-called
synchronous transport module, first hierarchical level at 155.520 Mbit/s, indicated by the
acronym STM-1.

Introduction

A new generation of transmission systems based on the SDH hierarchy (synchronous
digital hierarchy) has been developed because of the need to overcome the limitations
of plesiochronous multiplexing (PDH).
The SDH hierarchy, standardized through ITU-T recommendations G.707, G.708 and
G.709, answers the need of telecommunications administrations for a network that
associates a high performance level with those characteristics of flexibility and
manageability which are required to cope with growing user demands, both in terms of
multiple services and direct supervision of the resources used.
We have also seized the opportunity offered by global redefinition of frame structure and
transmission system characteristics to obtain further advantages in terms both of
management of low speed digital streams originating from existing networks and of
equipment simplification.
The "synchronous" multiplex technology allows to configure the sequence of bit groups
in the frame in order to permit the extraction/insertion (drop/insert) of low speed digital
data (for example a 34 Mbit/s signal in a 155 Mbit/s stream) without the use of costly
multiplex/demultiplex procedures in the knots of the network, that is without influencing
at the same time other digital signals contained in the high speed stream.
SRA 4 - 6/7/8/10/11/13 GHz (WB ODU) - UMN
911-381/02C0000 - Issue 3, July 2004