Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2000-07-14
2004-12-28
Vanderpuye, Kenneth (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S278000, C370S395600, C370S472000, C370S476000
Reexamination Certificate
active
06836482
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a method for the transmission of data in an ATM transmission system as well as to an ATM transmission system, particularly an ATM broadband transmission system.
DESCRIPTION OF THE RELATED ART
Many new transmission or switching principles for various types of transmission in communication networks have been developed during the course of the rapid development of communications technology in recent years. The STM transmission principle (synchronous transfer mode) deals with a synchronous transfer or transmission method, in which the data of various data channels are serially transmitted within different time slots, and the individual time slots are combined into frames. A frame synchronization word is transmitted for the synchronization of each and every frame, so that each time slot of a frame allocated to a specific date channel exhibits a fixed time spacing from the frame synchronization word. Each time slot can contain a relatively small number of bits, for example 8 bits, and appears at constant time intervals. However, highly different bit rates cannot be uniformly governed with the assistance of this STM principle, i.e., different communication networks for different bit rate ranges would have to be provided given application of the STM principle, particularly given the currently desired broadband signal transmission. A uniform digital broadband communication network (broadband integrated services digital network, BISDN) cannot be realized with the assistance of the STM principle.
The ATM transmission or switching principle (asynchronous transfer mode) is significantly more flexible compared to the STM transmission principle. According to this ATM principle, calls that contain 63 octets or bytes as payload information as a standard are transmitted instead of the time slots of the STM principle. These ATM cells are transmitted with a constant transmission rate dependent on the band width of the transmission medium. Dummy cells are used when no messages are to be transmitted. A “header”, which contains the control or address information for the corresponding cell, is attached to the information field of every cell, which contains the actual payload information.
FIG. 3
a
shows an illustration for explaining the ATM principle. As shown in
FIG. 3
a
, a plurality of cells Z are successively transmitted (in the direction indicated by the arrow) from a sender to a receiver. Each cell comprises a header with address or control information as well as an information field with the actual payload information. According to the defined standard, the information field comprises 48 octets, and the header comprises 5 octets, so that each cell is formed by 53 octets or bytes. Additional (header) octets can be attached to this cell format, which are capable of being employed for the routing of the cell upon transmission of the cell from a sending subscriber to a receiving subscriber.
In newer ATM broadband transmission systems or communication networks, the data streams between the individual transmission and reception assemblies are optically transmitted via light waveguides. These ATM broadband communication networks allow an extremely high data throughput that cannot—due to technological limitations—be processed by the switching elements that are thereby employed and that are usually fashioned in CMOS technology. To address this problem, the data to be transmitted are therefore supplied in parallel to transmission modules via a plurality of data lines and transmitted by the transmission modules serially multiplex via the light waveguides to reception modules, which in turn divide the serial ATM data stream onto corresponding, parallel data channels at the output side for further processing.
This principle is shown in
FIG. 3
b
. An optical ATM link serving as transmitter receives digital data of a plurality of data channels K
0
-K
n
. Further, the sender S is supplied with a clock signal T. Dependent on the clock signal T, the sender S thus respectively reads n+1 bits in in parallel, and converts these bits into a serial, multiplexed ATM data stream D having a correspondingly higher data transmission rate, and this data stream D is optically transmitted to a receiver E. This receiver E parallelizes the received, serial data streams D, and in turn outputs it in parallel via date channel lines K
0
-K
n
of the output side together with a clock signal T.
It is apparent on the basis of the above description that the demultiplexing of the serial data stream D in the receiver E represents a specific problem. For demultiplexing the data stream D, the receiver E must known which bit of the serial data stream D is to be allocated to which data channel K
0
-K
n
of the output side. For this purpose, known solutions provide that additional synchronization information be attached to the actual serial data stream D at the transmission side, these additional synchronization information being interpreted in the receiver E and defining the allocation of the digital information transmitted in the serial data stream D to the individual data channels K
0
-K
n
of the output side. Thus, for example, additional synchronization information can be attached with the assistance of an encoding implemented in the sender S, particularly a block encoding. As a result of the block encoding in the sender S, a redundancy is attached to the actual serial data stream D, as a result of which the serial data rate of the data stream D rises. On the other hand, a relatively high circuit outlay is required in the receiver E in order to be able to interpret the synchronization information attached to the serial data stream D. This all results in, for example, no inexpensive standard lasers can be utilized for the transmission of the data of the input-side data channels K
0
-K
n
.
An example for the demultiplexing of a serial data stream is disclosed in U.S. Pat. No. 5,579,324, in which the arriving bit stream is synchronized by a control block, resulting in a significant outlay in the demultiplexing at the reception side.
Furthermore, Swiss Letters Patent 682 277 discloses methods for the synchronization of a serial ATM bit stream, which particularly addresses how the cell boundaries of a serial ATM bit stream can be identified. However, how a demultiplexing of a serially transmitted data stream is to be efficiently undertaken at the reception side is not addressed in this reference.
SUMMARY OF THE INVENTION
The present invention is therefore based on the object of creating a transmission method for an ATM transmission system as well as a corresponding ATM transmission system, in which a receiver-side demultiplexing of the serially transmitted data stream is possible with the relatively simple circuit-oriented outlay. In particular, a correct demultiplexing of the serial data stream should be possible without attaching additional synchronization information and, thus, without attaching reduncancy.
According to the present invention, this object is achieved by a method for the transmission of data in an ATM transmission system, comprising the steps of supplying digital data of a specific plurality of data channels parallel to an input side of a sender, converting the digital data into data units that respectively comprise an identical plurality of bits from each of the data channels, serially transmitting individual the data units in a form of cells that are respectively composed of a specific plurality of the data units, each cell having a specific, characteristic bit sequence, receiving, by a receiver the serially transmitted data units, monitoring, by the receiver, the received data units for an occurrence of the characteristic bit sequence and, after identifying the characteristic bit sequence, identifying a first data unit of a cell corresponding to the characteristic bit sequence, successively dividing, beginning with the first data unit of the cell corresponding to the characteristic bit sequence, individual bits of each the data unit of the correspondin
Nguyen Van Kim T.
Schiff & Hardin LLP
Siemens Aktiengesellschaft
Vanderpuye Kenneth
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