Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Patent
1997-10-07
2000-05-02
Pham, Chi H.
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
370907, 370503, H04J 316
Patent
active
060581190
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a module which may be used singly or in combination with other like modules to provide an interface circuit into and out of SONET/SDH-standard signals. The invention also concerns a SONET/SDH interface circuit employing one or more such modules. The module of the present invention can take the form of an application specific integrated circuit.
BACKGROUND OF THE INVENTION
The American National Standards Institute has recently established a new basic standard for high-speed, multiplexed digital data transmission. This is the "synchronous optical network" standard, henceforth referred to as SONET. The SONET standard specifies optical interfaces, data rates, operation procedures and frame structures for multiplexed digital transmission via fiber optic networks.
The International Telecommunications Union (ITU) has adopted the interface principles of SONET and recommended a new global transmission standard for high-speed digital data transmission. This standard is the "synchronous digital hierarchy" (SDH).
For an account of the SDH standard, reference should be made to the report entitled "REPORT OF Q.22/15 MEETING" from "STUDY GROUP 15" of the ITU International Telecommunication Standardization Sector, bearing the document number "Temporary Document 62(3/15)" and the date "Geneva, May 16-27, 1994".
The SDH standard is designed to enable manufacturers to develop telecommunications equipment which: the world to its standard; and which older telecommunications formats used in N.America, Europe and Japan.
This is achieved by a complex hierarchy of so-called "Containers" (C) and "Virtual Containers" (VC), see FIG. 1. The container, e.g. C-4, C-3, C-12, etc., are information structures designed to accommodate data traffic with specific transmission rates. The C-4 carries traffic with a base rate of up to 139 264 kbit/s, the C-3 container carries either up to 44 736 or 34368 kbit/s, etc. The containers are turned into virtual containers by adding Path OverHead information (POH) to it. By procedures defined as multiplexing, mapping, or aligning, data structures are generated which are constitutive to the SDH. These data structures are named "Administrative Unit Groups" (AUG) and "Synchronous Transport Module" (STM). The label of an STM is defined by the number of AUGs it carries: a STM-4 contains for example four AUGs. An AUG contains either one "Administration Units" (AUs) of type 4 or three AU-3. Referring to the simplest cases, in turn one AU-4 contains one C-4 signal and one AU-3 carries one C-3 signal.
The SDH/SONET data frames, i.e., the STM-N signals, are 125 micro-seconds long. The amount of data transmitted in each frame depends on the hierarchy level N of the signal. The higher hierarchical levels are transmitted at higher data rates than the basic STM-1 level of approximately 155 Mbit/s. (The exact transmission rate is defined as 155.52 Mbit/s. However here and in the following transmission rates are often denoted by their approximate values. This in particular due to the fact that the exact data transmission rates are distorted by overhead data traffic and idle cell stuffing.) The integer N indicates how many times faster the data is transmitted than in the STM-1 level. For example STM-4 denotes a data transmission rate of 622 Mbit/s, whereby each data frame contains four times as many bytes as does a frame of STM-1. The highest defined level is STM-64, which has a data rate of 9.95 Gb/s. Clearly, each part of the STM-N signal is broadcast in the same time as the corresponding part of an STM-1 signal, but contains N times as many bytes.
The STM-1 signal, as shown in FIG. 2, contains an information rectangle of 9 rows with 270 bytes/row corresponding to a SONET/SDH data rate of 155.52 Mbit/s. The first 9 bytes/row represent the "Section OverHead", henceforth SOH. The remaining 261 bytes/row are reserved for the VCs, which in FIG. 1 is a VC-4. The first column of a VC-4 container consists of the "Path Overhead" (POH). The rest is occupied by the payload (a C-4 signal). Sever
REFERENCES:
patent: 5206858 (1993-04-01), Nakano et al.
patent: 5907682 (1999-05-01), Miyazawa
Engbersen Antonius P.
Herkersdorf Andreas
Lemppenau Wolfram
Schindler Hans R
Flynn John D.
International Business Machines - Corporation
Pham Chi H.
Tran Maikhanh
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