Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-09-25
2001-10-09
Olms, Douglas (Department: 2663)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S461000, C370S462000, C370S455000
Reexamination Certificate
active
06301241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission right assigning method for assigning a transmission right to one device of a plurality of devices which are connected to a transmission line and a communication system in which the method is employed.
2. Prior Art
Heretofore, there has been known a network system as a Local Area Network (LAN) management system described in Japanese Patent application of Laid-open No. Hei 5-95361. The LAN management system is constructed by interconnecting a plurality of terminal units through a data transmission line for exchanging data between.
In the above conventional LAN management method, one master unit and a plurality of terminal units are connected by a ring-like data transmission line, and the master unit sends a polling frame to the terminal units one by one through the ring-like data transmission line.
Each terminal unit having no data for transmission sends back a response polling frame to the master unit, while each terminal unit having data for transmission sends back a message data frame to the master unit.
When the master unit receives a response polling frame from a certain terminal unit, the master unit sends a polling frame to the next terminal unit. On the other hand, when the master unit receives a message data frame from a certain terminal unit, the master unit sends a message data frame to the terminal unit and then sends a polling frame to the next terminal unit.
In the above conventional Local Area Network (LAN) management system, however, the master unit sends a polling frame to each terminal unit one by one through the ring-like data transmission line, therefore it takes relatively long time to receive response frame, with the result that it is difficult to transmit emergency data to a destination terminal unit quickly.
As the master unit assigns a transmission right to all terminal unit one after another, but some of them having no data for transmission, there is a certain amount of waist time for data transmission. In addition, as a communication between each terminal unit is carried out through the master unit, there is a disadvantage that data communication speed is relatively low.
SUMMARY OF THE INVENTION
In view of the above situation, it is an object of the present invention to provide a transmission right assigning method and a communication system which are capable of satisfying a request for transmitting emergency data immediately and improving a transmission efficiency on the system.
To attain the above object of the present invention, there is provided a transmission right assigning method for assigning a transmission right indicating right of exploitation of a communication line to one device out of a plurality of devices, which are connected to the communication line and communicate each other, by a transmission right assigning device which is one device of the plurality of the devices, the method comprising the steps of: transmitting, to the plurality of the devices, a transmission request retrieving frame for retrieving transmission requests from the plurality of the devices by the transmission right assigning device; adding, if necessary, transmission request information including emergency degree information on transmission data in own device to the transmitted transmission request retrieving frame, by the plurality of the devices; retrieving the transmission request retrieving frame added, if necessary, with transmission request information including emergency degree information on transmission data at each of the plurality of the devices, by the transmission right assigning device; and assigning the transmission right to one device out of the plurality of the devices, based on the transmission request information included in the retrieved transmission request retrieving frame, by the transmission right assigning device.
In a preferred embodiment of the present invention, the transmission right assigning device assigns the transmission right to one device out of the plurality of the devices, based on the emergency degree information on the transmission data and transmission request count information regarding the transmission data included in the transmission request information.
In a preferred embodiment of the present invention, the transmission right assigning device, every time retrieving the transmission request retrieving frame, performs a calculation between the emergency degree information on the transmission data and transmission request count information regarding the transmission data included in the transmission request information; generates calculation information indicating how high the emergency degree is and how many the transmission request count is; stores the calculation information into a transmission request information table; and assigns the transmission right to one device out of the plurality of the devices, based on the calculation information.
In a preferred embodiment of the present invention, when a device to be assigned the transmission right can not be determined because of the presence of a plurality of devices having the same value of the calculation information each other, the transmission right assigning device assigns the transmission right to a device having the highest emergency degree out of the plurality of the devices having the same value of the calculation information each other in accordance with emergency degree.
In a preferred embodiment of the present invention, when a device to be assigned the transmission right can not be determined because of the presence of a plurality of devices having the same value of the emergency degree each other, the transmission right assigning device assigns the transmission right to a device having the highest device priority out of the plurality of the devices having the same value of the emergency degree each other.
To attain the above object of the present invention, there is provided a communication system, comprising: a communication line; and a plurality of devices, each connected to the communication line, for communicating each other; one of the plurality of the devices being a transmission right assigning device which assigns a transmission right indicating right of exploitation of a communication line to one device out of the plurality of the devices, wherein the plurality of the devices comprises an information transmitting means for adding, if necessary, transmission request information including emergency degree information on transmission data in own device to a transmitted transmission request retrieving frame; and the transmission right assigning device comprises a transmitting/receiving means for transmitting a transmission request retrieving frame to the plurality of the devices and retrieving the transmission request retrieving frame added, if necessary, with transmission request information including emergency degree information on transmission data at each of the plurality of the devices; and a transmission right assigning means for assigning the transmission right to one device out of the plurality of the devices, based on the transmission request information included in the retrieved transmission request retrieving frame.
According to the present invention, the transmission right assigning device transmits the transmission request retrieving frame to each of the plurality of the devices and then the information transmitting means in each device adds, if necessary, transmission request information including emergency degree information on transmission data in own device to the transmitted transmission request retrieving frame to transmit the added transmission request retrieving frame. The transmitting/receiving means retrieves the transmission request retrieving frame added, if necessary, with transmission request information including emergency degree information on transmission data at each of the plurality of the devices. The transmission right assigning means for assigning the transmission right to one device out of the plurality of the devices
Mehra Inder Pal
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Olms Douglas
Yazaki -Corporation
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