Multiplex communications – Wide area network – Packet switching
Patent
1994-07-14
1996-11-26
Hsu, Alpus H.
Multiplex communications
Wide area network
Packet switching
370 82, 370 941, H04Q 1104
Patent
active
055793100
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In the digital communication network according to CCITT Recommendations G. 709, the digital signals to be transmitted are inserted into special data function blocks called containers. These are extended by adding additional information (POH) to form virtual containers VC-n and can in turn be combined again to form "tributary units" TU-n or higher-order virtual containers and administrative units, and can be transmitted, inserted into a synchronous transport module STM-1, on the 155-Mbit/s level (or a higher level). The administrative or tributary units are switched through via switching networks (cross-connectors) in the form of special data blocks (cross-connect data blocks). In addition to the meaningful information (payload), data for switching path addresses, processor information, error control, alarm signals, etc. are also to be transmitted. The pulse frame of the STM-1 signal does not have the additional transmission capacity required for these data.
A method for switching through multiplexed signals via cross-connectors is known from European Patent Application EP-A3-0 407 851 (corresponding to U.S. Pat. No. 5,123,010. However, the pulse frame used therein permits only the transmission of a small amount of special information.
SUMMARY OF THE INVENTION
The object of the invention is to state a method for switching through digital signals suitable for the synchronous digital hierarchy.
This object is achieved by a method of the present invention for switching through digital signals wherein the digital signals re inserted into DSM pulse frames which have (in two-dimensional representation) in each case 9 lines and up to 100 N columns. It is possible to transmit a DSM data word comprising 9 bits in every position of a column, of which an octet comprising 8 bits is used for transmitting the digital signal.
Advantageous further developments of the invention are are as follows.
A further bit for transmitting monitoring and control information is provided for each octet of the digital signal. A DSM base pulse frame comprises 9 lines and 100 columns. Higher-order DSM pulse frames are generated by column-by-column interlacing of DSM base pulse frames.
Digital signals having higher data rates of the synchronous digital hierarchy are distributed over a plurality of DSM base pulse frames. The STM-1 signal and each DSM pulse frame have the same period length. The ratio of the system clock frequencies of the STM-1 frames and the DSM base pulse frames is 12 to 5. Four successive DSM-N pulse frames form one DSM multiframe.
The cross-connect base pulse frame (DSM base pulse frame) according to the invention for inserting a through-connect signal DSM comprises 9 lines and 100 columns with 9-bit words at each column position. The frame has a repetition time of 125 .mu.s. Four successive DSM base pulse frames form one multiframe.
The frame structure adapted to the signals of the synchronous digital hierarchy is advantageous. Thus, the number of lines matches, while the number of columns was extended.
The transmission rate of the DSM base pulse frame is 64.8 Mbit/s. Modules for this transmission rate can be produced with the CMOS-ASIC technology currently available. DSM-N signals with n-times the transmission rate can be generated by multiplexing DSM-1 signals column-by-column and are transmitted in corresponding DSM-N pulse frames.
Signals of the synchronous digital hierarchy (or else plesiochronous signals inserted therein) having higher data rates are divided into a plurality of signals, which are then transmitted in a plurality of DSM base pulse frames.
The repetition rate of the pulse frames is 8 kHz, which corresponds to a repetition time of 125 .mu.s. The ratio of system clocks (bit clocks) of the STM-1 pulse frame transmitted in the synchronous digital hierarchy and of the DSM base pulse frame is 12:5. This makes it readily possible to derive the one system clock from the other one. Even in the case of higher-order pulse frames which have the same repetition time, there is a simp
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Hamborg Franz-Otto
Heiles Jurgen
Kersten Hans-Otto
Wild Horst
Hsu Alpus H.
Ngo Ricky Q.
Siemens Aktiengesellschaft
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