Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-04-10
2001-08-28
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06282198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a frequency band control device and, more particularly, to a frequency band control device advantageously applicable to controlling a frequency band of a line constituting an ATM (Asynchronous Transfer Mode) network.
2. Description of the Background Art
Today, there is an increasing demand for a B-ISDN (Broadband Integrated Services Digital Network) capable of implementing high speed, high quality communication. Standardization of ATM technology which is the heart of the B-ISDN is progressing at high speed. The ATM technology divides data to be transmitted into segments of forty-eight bytes, adds five-bytes of control information or a five-byte header to each forty-eight bytes so as to form a cell having a fixed length of fifty-three bytes, and transfers such cells via a transmission path. Because the ATM technology is feasible for high speed switching using hardware, it is attracting increasing attention in the B-ISDN field, which is required to transfer a plurality of media information lying in different frequency bands at the same time.
When a single line is shared by a plurality of channels, the conventional ATM technology fixedly allocates a frequency band available with the line in accordance with the frequency band needed by the individual channel. For this kind of control, it is a common practice to use a table listing information for designating the channel to occupy the line on a time slot or cell time basis. The position of the table from which the information is to be read is sequentially shifted every cell time, so that the frequency band is allocated to the channels.
The above frequency band control device, however, has the following problem left unsolved. Assume that a buffer assigned to the channel designated by the table stores no cells to be sent to the circuit. Then, not only the above channel is wastefully designated, but also cells cannot be sent from the other channels on which cells to be sent exist, resulting in an unoccupied frequency band.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a frequency band control device capable of sending data immediately, whenever an unoccupied frequency band occurs in a line, by using the unoccupied band, while guaranteeing the minimum frequency band for the individual channel to transfer respective data.
In accordance with the present invention, a frequency band control device for an ATM circuit in which a plurality of channels share a single frequency band on a frequency band division basis includes a plurality of input buffers each being assigned to a respective channel for storing respective cells input from the channel until receiving an acknowledge signal. A priority order giving circuit gives, in each of consecutive time slots, a particular priority order to the send request signals output from the input buffers storing the cells. A cell conflict controller selects, from among the send request signals fed from the priority order giving circuit, the send request signal given the highest degree of priority, and then sends the acknowledge signal to the input buffer that output the above send request signal. When any idle frequency band exists in the circuit, the control device effectively assigns it to an ATM cell while guaranteeing the minimum frequency band required of the individual channel.
REFERENCES:
patent: 4564838 (1986-01-01), Boulogne et al.
patent: 5083269 (1992-01-01), Syobatake et al.
patent: 5130975 (1992-07-01), Akata
patent: 5687324 (1997-11-01), Green et al.
patent: 6-37785 (1994-02-01), None
patent: 7-66836 (1995-03-01), None
Chin Wellington
Jones Prenell
OKI Electric Industry Co., Ltd.
Rabin & Berdo P.C.
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