Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-05-17
2002-12-24
Vanderpuye, Ken (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000
Reexamination Certificate
active
06498794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmitter equipped with a cell switching function, and more particularly to a transmitter adapted for mapping and demapping of synchronous frames containing ATM cells of multiple channels.
2. Description of the Related Art
In the known public transmission network, audio signals and data information are transmitted to be processed via an infrastructure of SONET (Synchronous Optical Network) in a format of STM (Synchronous Transfer Mode). Such service signals according to the STM format are accessed, in each transmitter, at an STS-
1
(Synchronous Transport Signal: 51.84 MHz) level conforming with the SONET frame format or a VT (Virtual Tributary: 1.726 MHz) level. External interfaces employed therefor conform with OC-
48
(optical signal: 2.4 GHz), OC-
12
(optical signal: 600 MHz), OC-
3
(optical signal: 150 MHz), DS
3
(electric signal: 44.736 MHz), DS
1
(electric signal: 1.544 MHz) and so forth. Further, there is practically used of late a data information service which is based on the ATM (Asynchronous Transfer Mode) signal format to realize effective utilization of transmission lines and the band of transmission equipment.
Recently, eager demand is noticed in respect of a transmitter having, in particular, a cell switching function relative to ATM signals of multiple channels for achieving services with ATM signals while running the existing SONET network or the like. However, any transmitter equipped with such a switching function for STM signals and ATM cells has not been available heretofore. When STM signals of multiple channels to be switched are mapped to an STS-
1
signal, the mapping positions of the individual channel signals multiplexed to the STM signals are predetermined, so that the signals of the individual channels may be mapped to the relevant frame positions of the STS-
1
signal. Also in routing the STM signal of the each channel mapped to the STS-
1
signal, it has been possible heretofore to achieve easy routing since the relevant channel can be detected from the corresponding frame position of the STS-
1
signal.
However, when connecting a multi-channel ATM network to a SONET network or the like, there may be adopted a method of allocating one channel of each ATM cell to one channel of the STS-
1
signal; or when mapping multi-channel ATM cells to one channel of the STS-
1
signal, there may be adopted a method of mapping the ATM cells after determining the mapping position of each channel of the ATM cells in the same manner as the method relative to the STM signal. In the former case of allocating ATM cells to one channel, the number of required STS-
1
channels becomes equal to that of the channels of ATM cells. Using many STS-
1
channels signifies an increase of the number of physical paths in the transmitter, whereby a cross-connector and other devices employed for switching the ATM cells are rendered greater to consequently raise a problem that the transmitter as a whole is also enlarged in scale. Meanwhile, in the latter case of allocating ATM cells to multiple channels, some density nonuniformity is caused in the STS-
1
signal due to the density nonuniformity of the multi-channel ATM cells, so that any low-density channel portion in the STS-
1
signal is not usable for any high-density channel of the ATM cells to eventually result in an extreme inefficiency.
The ATM cells are routed in accordance with VPI/VCI which represent logical addresses stored in an ATM header, and then each ATM cell is transmitted to the relevant network. Since a logical connection is set per network (per ATM channel), there may occur a case where the same logical address is set in different ATM channels. In such a case, if each channel mapping position is not determined, it becomes impossible to identify the respective channels of the ATM cells mapped to the STS-
1
signal, hence raising another problem that proper routing to the relevant network fails to be performed. In addition, there may arise a further problem that, since no discrimination is executable between the channels when the ATM cells mapped to the STS-
1
signal are distributed to the relevant channels, exact distribution to the individual channels is rendered impossible.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a transmitter capable of efficiently mapping ATM cells of multiple channels to one STS-
1
signal.
Another object of the present invention resides in providing a transmitter which is capable of routing ATM cells to any interface module from an interface module containing multiple channels.
And a further object of the present invention is to provide a transmitter capable of routing ATM cells from any interface module to any network of an interface module containing multiple channels.
In accordance with an aspect of the present invention, there is provided a transmitter equipped with a cell switching function and having an interface module to serve as an interface between ATM cells and synchronous frames. The transmitter comprises a plurality of first physical paths for inputting ATM cells with channel identifiers given thereto to identify channels respectively; a second physical path for outputting the synchronous frame signal; channel identifier insertion means for inserting the channel identifiers, which are given to the first physical paths where the ATM cells are inputted, into predetermined areas of the ATM cells; and mapping means for mapping the multi-channel ATM cells, where the channel identifiers are inserted, to one synchronous frame signal and outputting the same to the second physical path.
Preferably, a detection means is incorporated in the interface module for detecting whether a predetermined value is set or not in the predetermined area of each ATM cell, and discarding any ATM cell where the predetermined value is not set.
In the above structure, when the interface module contains multiple channels, channel identifiers are previously given respectively to the individual first physical paths in the interface module. The channel identifier insertion means inserts the channel identifier given to the relevant first physical path into a predetermined area (e.g., cell header) of the ATM cell inputted from the first physical path. The mapping means maps the multi-channel ATM cells, where the channel identifiers are inserted, to the synchronous frame signal. Since the channel identifiers are inserted in the ATM cells mapped to the synchronous frame signal, any ATM cell can be identified with respect to the relevant channel, so that proper routing thereof to desired channels can be performed when the interface module is used in the transmitter.
In accordance with another aspect of the present invention, there is provided a transmitter equipped with a cell switching function and having an interface module to serve as an interface between ATM cells and synchronous frames. The transmitter comprises a plurality of first physical paths for inputting ATM cells with channel identifiers given thereto to identify channels respectively; a second physical path for inputting a synchronous frame signal where multi-channel ATM cells are mapped; and demapping means for demapping the ATM cells mapped to the synchronous frame signal and outputting the ATM cells to the first physical paths corresponding to the channel identifiers inserted into the predetermined areas of the ATM cells.
Preferably, a detection means is incorporated in the interface module for detecting whether the value in the predetermined area of each ATM cell is coincident or not with any of the channel identifiers, and the ATM cell is discarded if the result of such detection signifies no coincidence with any of the channel identifiers.
A channel identifier is previously given to each of first physical paths. The demapping means demaps the ATM cells mapped to the synchronous frame signal inputted from the second physical paths, and outputs each ATM cell to the relevant first physical path having the c
Taki Yoshitaka
Tsukamoto Keiichiro
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