JPS63211837A - Data transmission control system - Google Patents

Abstract

PURPOSE:To attain effective utilization of a transmission line by allowing each node station to reference a status management table prior to data transmission and to send a data only when an opposite node station is normal. CONSTITUTION:When one of node stations is going to send a data to other node station, a transmission/reception section 11 of the node station 1 intending to make transmission uses at first the status management table 13 provided in its own node station to retrieve the status of a reception side node station 2 and does not send a data if it is detected that the reception side node station 2 is faulty, and starts data transmission while confirming the idle transmission line 5 only when the reception side node station 2 is normally. Since useless data transmission is not executed, the increase in the utilizing rate of the transmission line by useless data transmission is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to data transmission control in a multi-access node station in which a plurality of node stations share a transmission path, and in particular to eliminating unnecessary data transmission. The present invention relates to a data transmission control method suitable for use in effectively using a transmission line.

[Conventional technology]

Generally, in a transmission network that has a multi-access transmission path to which multiple node stations are connected, when attempting to transmit data to one node station or another, the transmitting node station: Since the state of the receiving node station cannot be known in advance, data is transmitted unconditionally. If the receiving node is unable to receive data for some reason, such as the power being turned off, the transmitting node detects the receiving node's non-response to the data transmission described above, and IJ) After confirming that the receiving node is unable to respond, data transmission is stopped. If the receiving node station is in an abnormal state and cannot receive data, the transmitting node station that sends data to this node station will perform unnecessary data transmission for IJ tries, etc., as described above, and the transmission path will be interrupted. It will be wasted.

As a technique to eliminate such wasteful use of transmission lines, only a certain node station is kept alive at all times, and that node station inquires of each node station about the status of other node stations and returns the results. There is a method of managing the information by retaining it. This method requires wasted time because the specific node station queries all node stations, and the transmitting node station queries this specific node station regarding the status of the receiving node station. In this case, the managing node station needs to perform several retransmission operations in order to detect an abnormality in the node station that is the destination of one inquiry. It is something.

As a prior art related to this type of transmission method, for example, the technology described in Japanese Patent Application Laid-Open No. 101933/1988 is known, but this technology also does not take into consideration the effective use of the transmission path. do not have.

In general, in the C8MA/CD method, which is a multi-access method in which multiple node stations compete for transmission rights, there are fewer collisions of transmitted data between node stations when the utilization rate of the transmission path is low. However, as the utilization rate of the transmission path increases, the probability of collision of transmitted data between node stations increases.

Therefore, in this method, it is necessary to suppress the utilization rate of the transmission path as much as possible.

Hereinafter, the conventional technology of this CS MA/CD system will be explained with reference to the drawings.

FIG. 4 is a block diagram showing a transmission network to which the conventional C 8 MA/CD system is applied, and FIG. 5.6 is a timing chart explaining its operation.

In FIG. 4, 1 to 4 are node stations, and 5 is a transmission line.

11.21 is a transmitting/receiving section, and 12.22 is a buffer.

A transmission network according to the prior art is shown in FIG.

It is composed of a plurality of node stations 1 to 4 and a transmission line 5 of the C 8 MA/CD system, which is a type of multi-access system, and each node station 1 to 4 is represented within the node station 1.2. As shown in the figure, transmission and reception with other node stations and +C
Transmitter/receiver unit 11.21 that performs OMA/CD transmission control
and buffers 12 and 22 for storing transmitted and received data.

The timing chart shown in FIG. 5 is a timing chart for transmitting a small amount of transmission data 15 from the node station 1 to the node station 2. Hereinafter, the data transmission and reception operation in FIG. 4 will be explained with reference to this diagram.

In FIGS. 4 and 5, when the node station 1 transmits data to the node station 2, the transmitter/receiver 11 of the node station 1:
Whether or not other node stations 2 to 4 are using the transmission path 5 is confirmed by detecting carrier waves on the transmission path. If the other node stations 2 to 4 are using the transmission line 5, the transmitting/receiving unit 11 waits until the transmission line 5 becomes vacant;
Preamble that I generated myself (hereinafter simply referred to as P) 1
6, the address (hereinafter simply referred to as A) 17 of the destination node station read from the buffer 12, and data (hereinafter simply referred to as D) 18 are transmitted to the transmission path 5 as transmission data 15.

PI3. A17. It is assumed that the length of D18 has a specified length that is predetermined among the node stations 1 to 4. Node station 2
~4, the transmission data 15 from the node station 1 is received by the transceiver section of each station, and when A17 is the address of the own node station,
This transmission data 15 is recognized as data addressed to the own node station, and D18 is taken into the buffer of the own node station. If A17 is not the address of the own node station, the transmission data 15 from the node station 1 is discarded. In the example shown in FIG. 5, the transmission data 15 is transmitted from the node station 1 to the node station 2, so the address of the node station 2 is entered in A17. The first node station 2 receives the transmission data 15 from the node station 1 by the transmitter/receiver 21 within itself, and stores D18 in the buffer 22 since A17 indicates the address of the node station.

Similarly, node station 3.4 also transmits data 1 from node station 1.
However, since A17 is not an address addressed to the node itself, this transmission data 15 is discarded.

Data transmission from node station 1 to node station 2 is performed as described above. The node station 2 receives this transmission data 15
After receiving , data is transmitted to the node station 1 for a response, and this response is also performed in the same manner as described above.

Generally, in the (SMA/C1) system, node stations 1 to 4
can start transmission at any time if the transmission path 5 is free. In this case, there is a possibility that a collision will occur between a plurality of nodes at the start of transmission. In the example explained with reference to FIG. 5, when node station 1 starts transmitting, node station 2 also starts transmitting at the same time, and data may collide on the transmission path.

The time chart in FIG. 6 shows an example of such a case, and this case will be explained below. In addition, in FIG. 6, it is assumed that the node station 3.4 does not use the transmission path 5.

In FIG. 6, the node station 1 confirms that the transmission path 5 is free and starts transmitting P31 from the transmitting/receiving section 11. At the same time, the node station 2 also detects that the transmission path 5 is empty and starts transmitting P34 from the transmitting/receiving section 21. The transmitting/receiving unit 11.21 of the node station 1.2 transmits P31. Even during the transmission of P34, reception from the transmission path 5 is performed, and the transmitting/receiving unit 1
1 is.

The transmitting/receiving unit 21 compares the data received during the transmission of P31 with the P31 being transmitted, and similarly compares the data received during the transmission of P34 with the P34 being transmitted. Therefore, the transmitting/receiving unit 11゜21 receives a signal in which P31゜P34 transmitted by the node station 1.2 overlaps, and combines this received data with P31゜P34 transmitted by its own node station.
．． The occurrence of a collision is detected by detecting a mismatch with P34. This P31. The length of P34 is determined in consideration of the signal propagation time for all node stations, and the transmitting/receiving unit of each node station can detect the above-mentioned collision while transmitting P3ts P34. Also, P31 after collision detection. P3
The timing of stopping No. 4 is also agreed upon among all nodes. When the transmitting/receiving section 11.21 of the node station 1.2 detects the collision as described above, the transmitting/receiving section 11.21 of the node station 1.2 receives P31. The transmission of the P8 cow is stopped, and the waiting times 'l'l and T2 for starting retransmission production are determined from the random number table in the transmitter and receiver, respectively.

As a result, the transmitting/receiving unit 11 of the node station 1 attempts to retransmit the transmission data 33 after the time T1 has elapsed.

Further, the transmitting/receiving unit 21 of the node station 2 also attempts to retransmit the transmission data 36 after 12 hours have elapsed. In the example shown in FIG.
1 is smaller than T2, so the transmitter/receiver 1 of the node station 1
The retransmission is successful first, and the transmitter/receiver 21 of the node station 2
An attempt is made to retransmit the transmission data 36 after the time T2 has elapsed, but since the node station 1 is using the transmission path 5, this retransmission will be performed after the node station 1 completes transmission. Note that the retransmission operation of the node station 1.2 is performed in the same manner as described with reference to FIG.

In the C8M A/CD transmission control system described above, when the traffic to the transmission path 5, that is, the utilization rate of the transmission path 5 increases, collisions as explained in FIG. become unable. especially,
If data is sent to a node station that is unable to receive data, the data will be retransmitted due to no response from the other station.
The amount of traffic on the transmission path 5 increases due to unnecessary data transmission.

[Problem that the invention seeks to solve]

As mentioned above, the data transmission power method according to the conventional technology does not take into consideration the effective use of the transmission line, and wasteful data is transmitted on the transmission line due to retransmission, etc., which increases the traffic on the transmission line. There is a problem in that the amount increases, the probability of data collision between nodes increases, and effective use of the transmission path is inhibited.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a data transmission control system for a multi-access system transmission path to which a plurality of node stations are connected, which eliminates the need for wasteful data transmission and allows effective use of the transmission path.

[Means for solving problems]

According to the present invention, the object is to have a node station status management table in order for each node station connected to a multi-access transmission line to grasp the status of other node stations; When the state of its own station changes, it notifies other node stations to that effect, updates the status management tables of all other stations, and the node station that intends to transmit data changes the state before transmitting data. This is achieved by referring to the management table and transmitting data only to node stations in a normal state.

[For production]

When transmitting data, all node stations connected to a multi-access transmission path refer to the status management table provided within their own node station, and transmit data only when the status of the receiving node station is normal. Send. This eliminates wasteful transmission to a node station in an abnormal state and retransmission due to no response, making it possible to effectively utilize the transmission path.

As a result of the above, unnecessary data is not transmitted on a multi-access transmission line to which multiple node stations are connected, so it is possible to prevent an increase in the utilization rate of the transmission line due to unnecessary data, and It is possible to provide a data transmission control method that can effectively use the data transmission control method.

〔Example〕

Hereinafter, one embodiment of the data transmission system according to the present invention will be described in detail with reference to the drawings.

Figure 1 shows a node station and C8MA/C, which is a multi-access system to which the data transmission control system of the present invention is applied.
A block diagram showing an embodiment of a transmission network using a transmission path of the D method, FIG. 2 is a diagram explaining the state management table in FIG. 1, and FIG. 3 is a timing diagram explaining the operation of the data transmission control method according to the present invention. It is a chart. In FIGS. 1 and 2, 13.23 is a state management table, and the other symbols are the same as in FIG. 4.

As shown in FIG. 1, a transmission network to which the data transmission system of the present invention is applied has a plurality of node stations 1 to 4.

C8 MA/CD, which is a multi-access method
Each node station 1 to 4 performs transmission/reception with other node stations and transmission control of the C8MA/CD system, as shown in node station 1.2. A transmitting/receiving unit 11.21, a buffer 12.22 for storing transmitted and received data, and a state management table 13.23 provided according to the present invention and storing the states of other node stations.
It is composed of In addition, the status management table 13.23 provided in each node station is as shown in FIG.
Station addresses 41 of all node stations connected to the transmission path 5
and status information 42 corresponding to these station addresses. In the figure, the node station 10 station address 43
The state information 44 corresponding to is jllll, and the state information 44 corresponding to
indicates that it is in a normal state. Similarly, the node station 2.4 is also in a normal state, or the status information 42 corresponding to the station address of the node station 3 is 10'', indicating that the node station 3 is in an abnormal state.

In an embodiment configured as described above, one of the node stations
When a node station attempts to transmit data to another node station, the transmitting/receiving unit of the transmitting node station first searches for the status of the receiving node station using the status management table provided within the node station. As a result, if it is detected that the receiving side node station is in an abnormal state, data transmission is not performed, and only when it is detected that the receiving side node station is in a normal state, the transmission path 5 is cleared. Confirm and start data transmission. For example, when node station 1 transmits data to node station 2, the transmitting/receiving unit 11 of node station 1 has state information corresponding to the station address of node station 2 in state management table 130 as I11, and the node station After confirming that the node station 2 is in a normal state, the data transmission operation to the node station 2 is started. The data transmission operation in this case is performed in the same manner as in the conventional technique described with reference to FIGS. 5 and 6. However, in one embodiment of the present invention,
Since the transmission of data to a node station that is in an abnormal state and cannot receive data is suppressed as described above, unnecessary traffic is not added to the transmission path 5, and the data transmission as explained in FIG. 6 is suppressed. , the probability of a collision is extremely low.

As mentioned above, the present invention suppresses wasteful data transmission and makes effective use of the transmission path by using the status management table provided in each node station, so the status of each node station can be checked. The managed state management table needs to be updated so that it always has the correct contents. For this reason 5
In the present invention, when the state of a node station is changed, that node station notifies all other node stations of the change in state.

Below, the operation for updating this state management table will be explained in the third section.
This will be explained using the timing chart shown in the figure.

Now, if node station 1 changes from a normal state to an abnormal state,
For example, when node station l is powered off.

The node station 1 notifies the node stations 2 to 4 of the status change using transmission data 50 shown in FIG. 3.

The data 50 transmitted by the transmitter/receiver 11 of the node station 1 is P
51, a command for instructing a status change (hereinafter simply referred to as I) 52, and a source address (hereinafter simply referred to as F).
53, a receiving address (hereinafter simply referred to as T) 54, and D55.

P51. I52. F1a, T54. The length of D55 and the timing of starting transmission are determined in advance between the node stations 1 to 4. I52 is a command that instructs the receiving station to change the state of the state management table, and D55 is
It shows whether the state of the node station transmitting this data is changed from an abnormal state to a normal state or from a normal state to an abnormal state. Also, %F53 is set to 1I11 as the address of the own node station, and T54f'
! .

It is set to all 11N, which indicates addresses for all other stations.

The transmitting/receiving unit 11 of the node station 1 sends %P51 to the transmission path 5 after leaving to indicate that the transmission path 5 is empty, and then
I52. which was previously stored in the buffer 12. F'53.
T54. D55 is sequentially sent out to the transmission path. When the destination address T54 is a specific node station, the transmitter/receiver 11 checks the status of the destination node station using the status management table 13, and performs a transmission operation only when it is normal. 111, indicating that it is addressed to all stations, so the transmission data 5o is transmitted unconditionally.

When the node stations 2 to 4 receive this transmission data 5o,
It identifies that I52 is a status change instruction and that T54 is addressed to all stations, reads D55, and changes the status information corresponding to node station 1 in the status management table provided in its own node station according to the contents of 55. do. In this case, D5
5 instructs to change from normal state to abnormal state, each /-)' node station 1 in the status management table of stations 2 to 4.
The status information of is changed from 111 to llo''.

Each of the node stations 2 to 4 that received the transmission data 50 from the node station 1 attempts to respond to the node station 1, but
Since the status information of the node station 1 in the status management table is 11O1, indicating an abnormality, data transmission for response is not performed.

Next, the node station in the abnormal state recovers to the normal state and performs operations to instruct other nodes to change their status, inquire about status information of other nodes, and receive responses from other nodes. explain.

Now, when the node station 3 recovers from the abnormal state and transmits a status change instruction to the other node stations 1.2.4, the node station 3 transmits the transmission data 60 to all other nodes.

The transmission data 60 is composed of P61゜I6', F1a, T64, and D65, where D65 is an instruction to change from an abnormal state to a normal state, and F1a is the own node address l3.
-1T64 indicates an address addressed to all stations, which is all 111. The transmitting/receiving unit of the node station 3 receives P61 and 162. which are stored in the buffer in advance. F1a, T64, D65
is transmitted to the transmission path 5 without referring to the state management table, after checking whether the transmission path 5 is empty.

For the node stations 1 and 2.4, the operation 62 is a state change instruction,
Since T64 is all l1II and indicates that it is addressed to all stations, based on the contents of D65, the status information corresponding to node station 3 in the status management table within the local station is changed from lθ'' to 111.
Change to Further, the node stations 1, 2.4 are the node stations 3 and 3.
Upon receiving the transmission data 60 from , D65 indicates a change from abnormal state to normal state, and %T64 indicates all l11''.
As a result, a response is sent using the transmission data 70 to inform the station 3 of the contents of the status management table in each station. In the illustrated example, the node station 2 makes a response,
At this time, it is assumed that no transmission collision with other stations will occur.

Node station 2 has PI3. I72. F1a, T74 and D
75 is transmitted to the node station 3.

172 in this transmission data 70 is a command that responds to the status of one station, F1a is the address of node station 2, T74 is the address of node station 3, and D75
is data representing the status of all node stations connected to the transmission path 5. The transmitting/receiving unit 21 of the node station 2 records the availability of the transmission path 5 and the normal state of the node station 3 in a status table 23.
PI3 is sent to the transmission path 5, and then I72. F1a, T7
4. D75 is sequentially sent to the transmission line 5. The node station 3 is
When this transmission data 70 from the node station 2 is received, the status information corresponding to each node station in the status management table within the own node is initialized to the correct state based on the contents of D75 of the transmission data 70.

In the embodiment of the present invention described above, the node station that changes its status updates the status management table provided in each node station by notifying other nodes of the status change. However, due to a sudden abnormality such as an emergency power cut, a node station may not be able to notify other node stations of the abnormal state.

The present invention allows each node station in a normal state to constantly monitor the responses of other node stations during transmission and reception, thereby making it possible to update the state management table even in the above-mentioned case.
Next, updating of the state management table in such a case will be explained.

A transmitting node station that attempts to transmit data to a node station that was unable to notify other node stations of the abnormality due to a sudden abnormality will check if the other receiving node station is normal according to its own node station's status management table. It is determined that there is an error, and the data is transmitted without knowing that there is an abnormality in the receiving node. However, the sending node station cannot obtain a response because the receiving node station is abnormal, and after retransmitting the operation a predetermined number of times, it confirms the abnormality in the other receiving node station and updates the status management table within its own node station. Run the update. On the other hand, all other node stations that were not directly involved in this data transmission are monitoring the response status of this data transmission, and similar to the above-mentioned transmitting node station, the receiving node station opposite to this transmitting node station detects that the node is in an abnormal state, and updates the status information corresponding to the receiving node station from 11'' in the status management table within its own node.
Change to OI' and update the management table. As a result, from now on, each node station in a normal state can suppress data transmission to the node station in an abnormal state.

The embodiments in which the present invention is applied to the 2008 MA/CS system have been described above.

It can be easily applied to systems using other methods.

According to the embodiment of the present invention described above, unnecessary data transmission and retransmission to a node station in an abnormal state is eliminated, and especially in the case of the %C8MA/CD method, unnecessary traffic added to the transmission path is eliminated, so that the transmission between node stations is eliminated. Since there is no collision at the start of transmission, the transmission path can be used effectively.

Furthermore, there is no need to inquire of a specific station as to whether the receiving node is abnormal or not prior to transmission.

Transmission paths can be used effectively.

〔Effect of the invention〕

As explained above, according to the present invention, there is no need to transmit or retransmit useless data to a station in an abnormal state, and prior to transmission, there is no need to send or retransmit data to a station that is in an abnormal state. Data transmission is also no longer necessary, and the transmission path can be used more effectively.

[Brief explanation of the drawing]

In FIG. 1, the data transmission control method according to the present invention is applied. C8MA is a combination of node station and multi-access system
A block diagram showing an embodiment of a transmission network using a /CD method transmission path, FIG. 2 is a diagram explaining the state management table in FIG. 1, and FIG. 3 is a timing diagram explaining the operation of the data transmission method according to the present invention. 4 is a block diagram showing a single transmission network applying the C8MA/CD system according to the prior art, and FIGS. 5 and 6 are timing charts illustrating its operation. 1 to 4... Node station, 5... Transmission line,
11゜21... Transmitting/receiving section% 12.22...
...buffer, 13.23...state management table. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Fl Figure 6 1aa”□

Claims (1)

[Claims] 1. In a data transmission control system in a transmission network configured by a plurality of node stations connected to a multi-access transmission path, each node station manages the status of other node stations. Equipped with a state management table that allows each node to
A data transmission control method characterized in that the state management table is referred to prior to transmitting data, and data is transmitted only when the partner node is in a normal state. 2. When the status of the node station changes, each node station notifies other nodes of the change in status, and the node station that receives this notification updates the management table within the node station. Claim 1, characterized in that when the content is updated and this notification is from a node station starting up in an initial state, the content of the management table of the own node station is transmitted to the partner node station. Data transmission control method described. 3. Each of the node stations monitors the transmission and reception of data between other node stations, and updates the contents of its own status management table based on the results. Data transmission control method described in section.