SAES-T-360 PDF – Synchronous Digital Hierarchy Transmission Systems

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SAES-T-360 PDF Download

SAES-T-360

Synchronous Digital Hierarchy Transmission Systems

The standard includes specifications and requirements for various aspects of SDH systems, including:

1. Bit rates: The standard specifies the supported bit rates for SDH systems operating at 155 megabits per second and above.
2. Interface specifications/requirements: The standard defines the interface specifications and requirements for the transport of payloads, including digital signals of the Plesiochronous Digital Hierarchy (PDH) and Asynchronous Transfer Mode (ATM) cells. These specifications ensure compatibility and interoperability between different equipment and systems.
3. Multiplexing structures: The standard outlines the multiplexing structures used in SDH line and terminal equipment. This includes the organization and arrangement of the transmitted signals to efficiently utilize the available bandwidth and provide effective transmission and multiplexing capabilities.

By adhering to the requirements outlined in SAES-T-360, Saudi Aramco ensures the proper design and implementation of SDH systems, enabling reliable and efficient transmission of digital signals at high speeds.

sDH Design Requirements

According to SAES-T-360 “Synchronous Digital Hierarchy – Transmission Systems” standard of Saudi Aramco, the latest recommendations of the International Telecommunication Union – Telecommunications Standardization Sector (ITU-T) are recognized as the basis for SDH equipment specifications and deployment.

The ITU-T recommendations, specified in Section 3.2 of the standard, provide the basic specifications for SDH equipment, including deployment, interconnection, and interworking between SDH network elements. These recommendations cover the transport of payloads, including digital signals of Plesiochronous Digital Hierarchy (PDH) and ATM cells.

Any revisions made to the ITU-T recommendations listed in Section 3.2 automatically update the SAES-T-360 standard to reflect the revised specifications.

It’s important to note that additional Saudi Aramco Engineering Standards related to other aspects of SDH, such as network management, optical and microwave interface requirements, synchronization, etc., may be issued separately in the future.

In terms of design requirements, the SAES-T-360 standard specifies the following:

4.1 Digital Hierarchy Bit Rates:

The SDH transmission systems should support the following PDH bit rates as lower-level tributaries, based on specific Saudi Aramco application requirements. Additionally, support for the North American PDH bit rate of 44.736 Mb/s (T3) is required.

4.2 Synchronous Digital Hierarchy Bit Rates:

The first-level bit rate of the synchronous digital hierarchy should be 155.520 Mb/s, and higher SDH bit rates should be obtained as integer multiples of this first-level bit rate. The higher SDH levels are denoted by the corresponding multiplication factor of the first-level rate.

4.3 Basic Multiplexing Principle and Multiplexing Elements:

The standard provides a diagram (Figure 1) illustrating the relationship between various multiplexing elements and defines them in the context of SDH multiplexing structures.

These design requirements ensure the consistent implementation of SDH technology and support the efficient transport of digital signals in Saudi Aramco’s communication systems.

In the context of the SAES-T-360 standard, the following definitions are provided:

4.4.1 Synchronous Digital Hierarchy (SDH):

SDH is a hierarchical set of digital transport structures that are standardized for the transport of adapted payloads over physical transmission networks. It provides a framework for organizing and transmitting data in a synchronous manner.

4.4.2 Synchronous Transport Module (STM):

STM refers to the information structure used in SDH. It consists of an information payload and section overhead (SOH) information fields in a block frame structure that repeats every 125 microseconds. The basic STM is known as STM-1, defined at a rate of 155.520 Mb/s. Higher-order STMs (STM-N) are formed at rates equivalent to N (where N can be 1, 4, or 16) times multiples of the basic rate. Table 2 of the standard lists the standardized STMs.

Virtual Container (VC):

VCs are information structures used in SDH to support Path Layer Connections. They consist of an information payload and path overhead (POH) information fields in a block frame structure that repeats every 125 or 500 microseconds. Two types of VCs have been standardized: lower-order VCs (such as VC-1s and VC-2s, with further classifications like VC-11 and VC-12) and higher-order VCs (such as VC-3 and VC-4). Lower-order VCs contain a single container (C-11s, C-12s, or C-2s) along with the appropriate POH, while higher-order VCs comprise either a single container (C-3 or C-4) or an assembly of TUG-2s or TUG-3s along with the appropriate POH.

Administrative Unit (AU):

An AU (AU-3 or AU-4) is the information structure that provides adaptation between the higher-order Path Layer and the multiplex Section Layer in SDH. It consists of an information payload (the higher-order VC) and an AU pointer. AU-4 comprises a VC-4 along with an AU pointer indicating the phase alignment of the VC-4 with respect to the STM-N frame. AU-3 comprises a VC-3 along with an AU pointer indicating the phase alignment of the VC-3 with respect to the STM-N frame. In both cases, the AU pointer location remains fixed with respect to the STM-N frame.

Administrative Unit Group (AUG):

An AUG refers to one or more AUs occupying fixed and defined positions within an STM payload. It consists of a homogeneous, byte-interleaved assembly of AU-3s or an AU-4.

Tributary Unit (TU):
A TU is an information structure used for adaptation between the lower-order and higher-order Path Layer in SDH. It consists of an information payload (the lower-order VC) and a TU pointer. The TU-n (where n = 1, 2, 3) comprises VC-n along with a TU pointer. TU-1s are further classified as TU-11, which carries VC-11, and TU-12, which can carry either VC-11 or VC-12.

Tributary Unit Group (TUG):

A TUG refers to one or more TUs that occupy fixed and defined positions within a higher-order VC payload. TUGs are composed of mixed capacity payloads of different sizes. A TUG-2 consists of a homogeneous assembly of TU-11s, TU-12s, or a TU-2. A TUG-3 consists of a homogeneous assembly of TUG-2s or a TU-3.

Container: C-n (where n = 1-4):
A container is the information structure that forms the network synchronous information payload for a VC. Each defined VC has a corresponding container. Adaptation functions have been defined for common network rates into a limited number of standard containers. The rates associated with containers are specified in ITU-T Recommendation G.702. For example, C-1s are further classified as C-11, which carries the North American rate of 1.544 Mbits/s (T-1), and C-12, which carries the European rate of 2.048 Mbits/s (E-1). The containers for the rates associated with Saudi Aramco applications, as specified in Section 4.1 of the standard, include C-12 for 2.048 Mbits/s (E-1), C-3 for European 34.368 Mbits/s (E-3) or North American 44.736 Mbits/s (T-3), and C-4 for 139.264 Mbits/s.

Pointer (PTR):

A Pointer is an indicator that defines the frame offset of a VC with respect to the frame reference of the transport entity on which it is supported. It helps in maintaining synchronization and alignment of the VC within the transport entity.

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