Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-03-08
2003-02-18
Rao, Suwa S. (Department: 2666)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S395600, C370S466000, C370S474000
Reexamination Certificate
active
06522669
ABSTRACT:
FIELD OF INVENTION
The present invention relates to devices and methods pertaining to telecommunications equipment, and more particularly to methods for coupling TDM-channels through a node in a telecommunications system. The invention also relates to such nodes, and to a device board in such a node, and to a telecommunications system that includes such device boards and such nodes.
DESCRIPTION OF THE PRIOR ART
Several different ways of coupling TDM-channels through a node with the aid of different forms of transport modules, such as cells for instance, are known in the art.
U.S. Pat. No. 5,237,564 describes how frames are coupled through an ATM-switch, said frames being referred to as frame relay types and having variable lengths.
U.S. Pat. No. 5,412,655 describes a system which couples TDM-channels through an ATM-switch. In this system, there is received a frame which includes a plurality of time slots of which each may include a TDM-channel. Information transmitted in the channels is stored in a corresponding buffer, i.e. there is one buffer for each TDM-channel. When one such buffer is full, its contents are sent through the switch in an ATM-cell and one cell is thus used with each connection.
U.S. Pat. No. 5,450,411 describes a system for multiplexing isochronous data and burst data and sending the multiplexed data through an ATM-switch with the aid of an ATM-cell.
WO94/11975 and WO95/17789 describe ATM-networks. Among other things, these documents describe an ATM node or an ATM-switch which receives traffic in the form of PCM signals (Pulse Code Modulation) in channels having the form of time slots in mutually sequential frames, wherein PCM signals arriving at ATMU units (ATM Interface Unit) are packed in ATM-cells and coupled through an ATM-switch core to a corresponding ATMU unit, where the PCM signals are transmitted in time slots in mutually sequential frames. A node or switch contains several such ATMU units and all PCM channels that are to be transmitted between two such ATMU units are packed in the same cell. An ATMU unit receives the PCM signals on something that is referred to as NCT links, and includes a number of multiplexors coupled to a matrix-configured buffer CWB (Cell Wide Buffer) which is dimensioned in accordance with the number of bytes (i.e. the complete PCM word in a time slot) that can be included in an ATM-cell, and also in accordance with the number of other ATMU units present in the node. In this case, the number of multiplexors is equally as large as the number of bytes that can be accommodated in a cell. All multiplexors are also connected to an incoming NCT line. These multiplexors receive mutually synchronized frames with time slots over the NCT lines, and each multiplexor is able to switch a selected time slot from a selected line to a selected position in CWB. In this case, the multiplexors first switch the first time slot of all incoming frames to selected positions, and then switch the second time slot of all frames, and so on. Cells are then formed from the contents of the CWB. ATMU operates essentially in the same way in the opposite direction, although with the use of demultiplexors which couple out bytes with PCM signals on NCT lines synchronously with one another. In this case, the multiplexors and demultiplexors operate synchronously with one another and thus require all channels to be equally large for switching the channels. The size described is that of pulse-code modulated signals, which normally have a size of one byte. However, channels of different sizes on one and the same line are very usual in the concept of present-day telecommunications. For instance, it is usual to compress PCM signals and take up less than one byte, for instance. Such compression may be of interest when wishing to reduce the costs of using a public network. The aforedescribed system does not allow such smaller channels to be switched at the same time as switching the larger PCM channels, because of the use of multiplexors. The system described in this prior publication also requires the NCT lines, as experienced by the multiplexors, to be synchronized with one another.
SUMMARY OF THE INVENTION
The present invention addresses the problem of how TDM-channels of mutually different sizes can be coupled simultaneously through a node in a telecommunications system when all TDM-channels that are received in a frame on a device board in the node and that shall be sent to a second device board in the node are packed in a common transport module.
This problem is solved by storing in an input buffer the contents of a frame from an information stream received on a first device board, copying the contents of all TDM-channels that are stored in each such input buffer on the first device board and that are to be further coupled from the node via a transmitting section of a second device board, to a transmitting buffer corresponding to said transmitting section, and sending the content of the transmitting buffer to the second device board by means of a transport module.
The problem is also solved by receiving one such transport module that includes TDM-channels in a transmitting section of a second device board in the node, wherein the transport module solely includes a plurality of TDM-channels arriving from a first device board, wherein the content of the transport module is stored in a receiving buffer corresponding to the first device board, wherein all TDM-channels in each receiving buffer on the second device board that shall be sent in a frame on a node outgoing line are copied in an output buffer to positions corresponding to said channels, and wherein the content of the output buffer is sent in a frame in a node-outgoing information stream that includes mutually sequential frames.
Thus, an object of the present invention is to provide a method, a telecommunications system, a node, and a device board in which simultaneous coupling of TDM-channels of mutually different sizes through a node in a telecommunications system is achieved wherewith all TDM-channels that are received in a frame on a device board in the node and that shall be sent to a second device board in said node are packed in a common transport module which is sent to said second device board.
The object is achieved with a method that includes the steps of receiving in a receiving section of a first device board in the node at least one information stream that includes mutually sequential frames, where each frame includes a number of TDM-channels, storing the content of one frame from an information stream in a corresponding input buffer, copying the content of all TDM-channels that are stored in each such input buffer and that are to be forwarded from the node to a second device board via a transmitting section (
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) to at least one transmitting buffer corresponding to said transmitting section, and transmitting the content of the transmitting buffer by means of at least one transport module.
The object is also achieved with a telecommunications system, a node in a telecommunications system, and a device board in such a node, wherein the device board includes a receiving section that has at least one input port for receiving. TDM-channels in TDM-frames, and at least one transmitting buffer which is adapted for connection between the receiving section and a transmitting section of another device board. Each input port has connected thereto at least one corresponding input buffer for receiving a frame that contains TDM-channels, wherein each input buffer is also connected to each transmitting buffer. The receiving section also includes control means. The control means is connected to all transmitting buffers and to all input buffers and is responsible for copying to said transmitting buffer all the TDM-channels that are received on the device board and stored in the input buffers and that are intended for the transmitting section of the other device board, and to ensure that the content of the transmitting buffer reaches the transmitting section of the other device board, by sending at least one
Duong Frank
Rao Suwa S.
Telefonaktiebolaget LM Ericsson (publ)
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