Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-18
2001-10-23
Ton, Dang (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S404000, C370S395430
Reexamination Certificate
active
06307859
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of telecommunication and particularly to a device and method in telecommunication networks or a connection device, an exchange unit comprising at least one such connection device, and methods for sending, receiving and switching signals within an exchange unit. Such an exchange unit can, for instance, be a telephone exchange for switching digital information.
PRIOR ART
Transport of data and information mostly occurs in some kind of serial transmission, where the information flow is arranged in time according to a standard stipulated sequence pattern. Examples of this are transmission of the TV-signal to a television set, digital PCM-transmission (Pulse Code Modulation) of data and telephony, transmission of speech and data via the radio signal to a GSM-phone etc. A particular such sequence pattern for telecommunication is division of the information flow into successive frames, where each frame comprises a set number of time slots, and one channel or connection between two communicating units takes up one time slot in several successive frames. Signals in such a channel may in these cases comprise video image information, speech information, pure data information or control information.
Pure data transmission can often occur using HDLC-packages (High Level Data Link Control). Such a package comprises data and an address, and the package is sent from one computer to another over any network using the address. Such data packages are used in pure computer networks, i.e. where several computers are interconnected. Such networks usually have a bus or ring structure. Such an HDLC-package can also be transmitted over an ordinary telecommunication network, where the ordinary telecommunication network transfers information over, for in-stance, PCM-lines in the previously mentioned time slots. An HDLC-package is then divided and transferred in one or several time slots in any successive frames over the telecommunication line according to any particular protocol and is coupled through an exchange unit in the shape of time slots, i.e. the whole package is not switched through the exchange at the same time.
Another transfer system is ATM (Asynchronous Transfer Mode), where data and telephony is transferred in the form of cells of a fixed size. An ATM-cell comprises 53 bytes of block information, where 48 bytes are data or telephony and the remaining 5 bytes comprises address and control information. Different ways exist for interconnecting telecommunication lines of PCM-type with exchanges through which speech and data in cells are transported. In an ATM-exchange a queue can form when simultaneous incoming information from different directions is to go out the same way through the switching core in such an exchange. Such forming of a queue can cause inpredictable delay and lost information.
U.S. Pat. No. 5,412,655 discloses a system switching TDM-channels (Time Division Multiplex) through an ATM-exchange. In this system a frame is received comprising a number of time slots, where each time slot can comprise a TDM-channel. Information transferred in the channels is stored in a corresponding buffer, i.e. there is one buffer per TDM-channel. When such a buffer has been filled, its content is sent through the exchange as an ATM-cell and one cell per connection is thus used.
U.S. Pat. No. 5,495,484 discloses an ATM-network interconnected using a bidirectional optical loop.
U.S. Pat. No. 5,414,819 discloses a network for interconnecting a processing element and which comprises an optical connection.
U.S. Pat. No. 5,327,427 discloses a logical hybrid ring device comprising two loops interconnected using two cross-connection nodes.
U.S. Pat. No. 5,319,486 discloses a node comprising address reading means for received packages. Since the information transferred in the above mentioned frame-divided transfer structure can vary in dependence of which type of information is being transferred, where the information can be data, compressed speech, pure speech or video, the information in one channel takes up parts of the structure of different sizes. It can fill one time slot, several time slots or only a part of a time slot. It is therefore of interest to provide an exchange unit which can handle these varying flows in an efficient way. The problem with ATM-exchanges in this context, i.e. when used in connection with PCM-links, is that it is difficult to use the ATM-structure efficiently. In efficient use of the ATM-structure, a cell used for transfer of one channel is filled completely. This is no problem when the channel used is large, i.e. uses more than one time slot, which can be the case in data transmission, but when the channel is small, i.e. only takes up one or part of one time slot and is used for transfer of telephony, long and unacceptable delays arise in an ATM-exchange. The other extreme of only filling the cell with the contents of one channel from one frame, normally only one time slot, means a considerably faster exchange but inefficient use of the cells. Such switching of many cells through the ATM-exchange can cause problems with great delays due to buffering. This structure is not flexible and adaptive to different conditions such as channels taking up less than one time slot per frame, either.
DESCRIPTION OF THE INVENTION
The present invention addresses a problem of providing an efficient way of fast switching of signals through an exchange unit when it is to be possible to use this exchange unit flexibly for different applications, such as transmission of speech and data, while a constant delay through the exchange unit is guaranteed.
Another problem solved by the present invention is to provide a signal structure for sending through an exchange unit which is simple and easily adaptable to different user requirements, such as long or short delay of signals switched through the exchange unit.
An object of the present invention is thus to provide an efficient way of switching signals through an exchange unit while avoiding long switching delays.
A further object of the invention is to provide a signal transport and handling of signals switched through the exchange unit.
One more object is to provide an exchange unit with high capacity of signal switching.
This is achieved by adding, to at least a part of a signal in a traffic channel received on a first telecommunication line, said traffic channel filling one, a part of one or more than one time slot in several consecutive frames, an address at least partly pointing to the time slot/s in the frame/s in which a part of the signal/s is going to be sent.
This problem is thus solved by a connection device, an exchange unit comprising such a connection device, and a method for sending signals within the exchange unit, said connection device comprising at least one input buffer for receiving and storing at least one frame of traffic incoming to the exchange unit, where signals are transmitted in traffic channels in time slots, a message writing device connected to the input buffer and a descriptor write unit connected to the message writing device. The descriptor write unit comprises descriptors established in advance for signals received in the input buffer, each descriptor comprising an address. The message writing device adds, for each traffic channel, an address from the first descriptor write unit to a pay-load comprising at least a part of one or a limited number of signals received in the traffic channel for forming a message, said address pointing to a corresponding message reading device and, at least indirectly, at least one time slot or a part of a time slot in at least one frame in which the pay-load is to be sent from the exchange unit, and sends the message to the message reading device. The length of the messages can be varied.
The problem is also solved by a connection device, an exchange unit comprising such a connection device and a method for receiving signals within the exchange unit, said connection device comprising at least one output buffer for storing sig
Burns Doane Swecker & Mathis L.L.P.
Nguyen Toan
Telefonaktiebolaget LM Ericsson (publ)
Ton Dang
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