Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-09-22
2001-12-18
Vincent, David R. (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395610, C370S396000
Reexamination Certificate
active
06331981
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method as well as a corresponding network component, both used in a communications network, for switching connections with a low bit rate between input modules and output modules of the network component.
2. Description of the Prior Art
In communications networks such as mobile radio networks or stationary networks, information—e.g. traffic information or signaling information in speech transmission—is transmitted with low transmission rates via lines between network components by means of TDMA (Time Division Multiplex Access). Thus, PCM30 or PCM24 terminal lines can be employed. For hardwired information transmission—in stationary networks, but also in mobile radio networks, especially of the next generation—ATM (Asynchronous Transfer Mode) transmission, due to its advantages regarding broadband applications, is gaining increasing acceptance. Nevertheless, narrowband information transmission via connections with a low bit rate—e.g. TDM connections—remains an important application for the majority of the mobile or stationary network subscribers. Therefore, when the TDM multiplex technology is converted or translated into ATM transmission technology in a network component, a large delay usually arises—e.g. 8 msec given 8 kbit/sec speech transmission. This leads to a degradation of the speech quality.
In principle, a conversion procedure from TDM multiplex technology into ATM transmission technology does exist which leads only to small delays—e.g. by filling the ATM cells with only a few bytes—however, this results in an uneconomical use of the ATM bandwidth. For this reason, it has long been a problem to realize network components of a telecommunications network so that they distribute the traffic internally via an ATM switching means and simultaneously support TDM traffic with a low bit rate at the external lines.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and a network component for switching connections with a low bit rate on the basis of ATM, by means of which method or component a lowest possible delay time and a high utilization ratio of the available ATM bandwidth are simultaneously achievable.
This object is inventively achieved in a method and network component for switching connections with a low bit rate between input modules and output modules of the network component in a communications network, wherein the input modules and the output modules inventively form a first switching level and an ATM switching stage arranged between the input modules, and the output modules forms a second switching level. In the first switching level, a number of low bit rate connections at the input module, which are to be transmitted to the same output module, are merged by the input module into at least one ATM connection. In the second switching level, the switching through of the ATM connections ensues by the switching stage for transmission of information in ATM cells. Additionally in the first switching level, the switched through ATM connections of one or more input modules are converted by the output module into the low bit rate connections.
By dividing the switching process into two levels, a number of connections are forwarded together in the same ATM connection, so that a low delay and a good utilization of the ATM cell capacity are advantageously achieved. The combined switching in two switching levels represents a particularly economical solution for functions specific to mobile radio and switching applications dealing with low bitrate traffic, simultaneously assuring an acceptable speech quality with good exploitation of the ATM bandwidth. The employment of multilevel switching in an ATM switching means and in input and output modules arranged separately therefrom harmonizes two opposing aspects—namely, the delay by the conversion of connections of low bit rate into ATM technology is minimized, and the exploitation of the ATM bandwidth is increased. The concept of decentralized switching in two levels has the advantage that the switching processes can be performed in the same, or substantially the same manner, not only in the input and output modules, but also in the ATM switching means. Furthermore, an adjustment of the software and hardware in the switching levels is possible using a switching controller in a simple and low-cost fashion.
In an embodiment of the invention, a common control unit takes over the control of the functions not only in the first switching level but also in the second switching level. It is particularly advantageous if the ATM switching unit is driven according to a decentralized switching principle and has a control arrangement which effects adjustments in the input modules and the output modules of the first switching level. The uniform controlling of the first and second switching levels can be realized with low hardware and software outlays.
The bi-level method for switching can be applied according to alternative embodiments of the invention, regardless of whether external lines are respectively connected at the input modules and the output modules of the first switching level, via which lines data packets (information) are received and transmitted by time division multiplex connections—e.g. TDM connections—or if external ATM lines are respectively connected at the input modules and output modules of the first switching level, over which lines data packets (information) from a number of connections are received and transmitted in a structured fashion in a time division multiplex frame—e.g. TDM frame—or in ATM minicells.
According to other embodiments of the invention, different techniques can perform the narrowband switching in the first switching level. Two of those techniques are based on the collection of minipackets in ATM cells, wherein a selection is made, using a connections table in the input module or in the output module, as to which minipacket is inserted into which ATM cell, or which minipacket is distributed to which connections of the output module. Three methods follow the principle of first merging the connections—e.g. TDM connections—at common outputs and subsequently converting these connections into the packet connections, which is the same as entering the information into the ATM cells. This process has the advantage that up to a five-times lower delay and simultaneously at least twice as high a utilization of the available bandwidth are obtainable, compared to the two techniques initially described.
The switching in two levels preferably relates to traffic connections of low bit rate (since these constitute the majority of connections which occur); however, it can also be applied to signaling connections and to operations and maintenance connections (O&M, Operations & Maintenance).
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Harth Arno
Holzner Peter
Klug Andreas
Korte Werner
Schrodi Karl
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
Vincent David R.
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