Communication system and method

Details Communication system and method Communication system and method

1998-05-11

2003-04-15

Marcelo, Melvin (Department: 2663)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S412000

Reexamination Certificate

active

06549537

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication system and a method for transmission and reception of a plurality of data different in quality of communication from each other including real-time data and nonreal-time data.
2. Description of Related Art
The ATM (Asynchronous Transfer Mode) communication system can provide an asynchronous communication, transmit data at a transfer rate covering a wide range from several tens Megabits per second (Mbps) to Gigabits per second (Gbps), and meets the requirements for a next-generation LAN (Local Area Network).
FIG. 1
shows an ATM terminal adopting an ATM communication of this type. As shown, the ATM terminal comprises a CPU (Central Processing Unit)
101
, a memory
102
in which data to be transmitted are stored, a dual-port RAM
104
, circuits
105
,
108
and
111
to generate cells, circuits
106
,
109
and
112
to add a header to each cell, traffic shaver circuits
107
,
110
and
113
, and an arbiter circuit
114
.
The CPU
101
reads data from the memory
102
via a CPU bus
103
, and transfers it to the dual-port RAM
104
which will supply three data to the cell generation circuits
105
,
108
and
111
, respectively, which will generate cells based on a size of PDU (Protocol Data Unit). The cells are supplied to the head add circuits
106
,
109
and
112
which will add headers to the supplied cells, respectively, to generate ATM cells for delivery to the traffic shaver circuits
107
,
110
and
113
, respectively. In the traffic shaver circuits
107
,
110
and
113
, the supplied cells are subjected to a traffic shaving to adjust the ATM transfer rate to supply the cells to the arbiter circuit
114
. The arbiter circuit
114
supplies the cells from the traffic shaver circuits
107
,
110
and
113
to physical layers (not illustrated), respectively while re-arranging, by buffering, cells supplied at a same timing and also supplying them to the physical layers. More specifically, the arbiter circuit
114
arbitrates all connections in a same manner without discrimination of the quality of transmitted data, for example, whether they are real-time data or nonreal-time data.
The above ATM terminal is featured by maintaining a real-time occurrence of a data communication, namely, a necessary bandwidth for the communication. However, when supplied with ATM cells from the traffic shaver circuits
107
,
110
and
113
, respectively, at a same timing, the arbiter circuit
114
has to provide an arbitration to buffer one of the ATM cells. Therefore, jitters take place in the ATM cells. As shown in
FIG. 2
, for example, when real-time ATM cells are supplied more early than nonreal-time ATM cells, the arbiter circuit
114
will output the real-time ATM cells more early. On the other hand, when nonreal-time ATM cells are continuously supplied more early than real-time ATM cells, the arbiter circuit
114
will output the real-time ATM cells after outputting the nonreal-time ATM cells. In this case, however, the longer the continuation of the nonreal-time ATM cells, larger cumulated jitters will take place in the real-time ATM cells, which will impair the real-time occurrence of a data communication.
SUMMARY OF THE INVENTION
The present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a communication system and a method for transmission of real-time and nonreal-time cells without any jitters caused in the real-time cells.
The above object can be accomplished by providing a communication system for outputting a first data to be real-time transmitted and a second data to be nonreal-time transmitted, comprising, according to the present invention, means for generating synchronous cells to output the first data synchronously with the communication system, means for generating asynchronous cells to output the second data, means for selecting either the synchronous or asynchronous cells, and means for controlling the selecting means to preferentially output either the synchronous or asynchronous cells.
According to another aspect of the present invention as set forth in claim
2
, the controlling means controls the selecting means to preferentially output the synchronous cells.
Therefore, when synchronous cells are generated, the communication system according to the present invention will preferentially output the synchronous cells rather than asynchronous cells.


REFERENCES:
patent: 5173901 (1992-12-01), DeSomer
patent: 5204857 (1993-04-01), Obara
patent: 5392280 (1995-02-01), Zheng
patent: 5570355 (1996-10-01), Dail et al.
patent: 5768273 (1998-06-01), Aznar et al.

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