JPH11252103A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a communication error caused by fading or interruption of a radio wave or the like efficiently. SOLUTION: A communication error detection means 1 of the radio communication system detects a packet causing a communication error and allows a re-transmission means 4 to send the packet after a prescribed time set in a re-transmission timing setting means 3. When the communication error cannot be recovered even after repeating the re-transmission 4, a re-transmission stop timing setting means 5 and a re-transmission stop timing detection means 6 cooperate with each other to stop the re-transmission. A same packet is repetitively and continuously sent in advance and when a receiver side selects s packet without a communication error among 2nd and succeeding packets, a probability of recovering the communication error before the re-transmission is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication apparatus in which a radio transmitting station performs packet radio communication with a radio receiving station.

[0002]

2. Description of the Related Art For example, at a manufacturing site, with the demand for computerization, a programmable controller, a CNC,
Networking of robot controllers and the like is progressing. Such FA networks require higher data transmission reliability as well as higher speed and higher performance for improving production efficiency.

[0003] In the case of wired communication, communication cables must be re-installed in response to the addition or change of a line at a manufacturing site, or a layout change, or data transmission to a moving worker or a mobile unit. Needs to reconnect the communication cable, and the cost and labor involved cannot be ignored, so it can be easily and more cost-effectively dealt with in case of layout change or mobile communication station moving during work. Attention has been focused on wireless communication that is easy to perform, and the introduction and spread of wireless communication has been desired in such fields.

However, in packet radio communication using radio waves, the communication environment is much worse than in wired communication, and noise is mixed, fading occurs due to reflection of radio waves, radio waves are blocked due to passage of obstacles, radio field strength is reduced, and the like. Therefore, an error occurs in the data or a packet is lost in the middle of a communication path, and a communication error occurs on a daily basis.

Therefore, in the packet radio communication, a reception notification is generally sent back from the radio reception station to the radio transmission station, and the reception notification does not reach the radio transmission station within a predetermined time or is a notification of an error reception. In such a case, immediately retransmit the packet that caused the communication error, so-called ARQ
(Auto Repeat reQuest) method is used to recover communication errors caused by high-speed changes in radio wave intensity due to noise and the like.

However, in a wireless communication device as shown in FIG. 8, a remote I / O of a programmable controller is used.
A wireless transmitting station (master) M is connected to the O master via a remote I / O network, and a communication radio wave transmitted from the wireless transmitting station M propagates in the factory and directly or in the factory. The light reaches the wireless receiving stations (slaves) S1, S2 # while being reflected irregularly or blocked by obstacles. Then, fading occurs depending on the state of reflection until arrival, and the like. Further, as shown in FIG. 9 (a), the worker H blocks the radio wave, or as shown in FIG. 9 (b), the radio receiving station (slave) S moves to the moving body B which is moving. Radio waves may be interrupted. In such a case, the fading cycle and the interruption time of the communication radio wave by the moving worker H or the moving body B are much longer than the repetition cycle of the normal packet communication, and are several milliseconds to several tens of milliseconds, or In some cases, the communication error recovery method described above may be repeated for a long time, so that the retransmission is repeated many times while the communication failure continues. The repetition of this useless retransmission of the useless packet also delays communication with another wireless receiving station.

As a measure for recovering from a communication error, the aforementioned AR
In addition to the Q system, an error correction system using an error correction code is also known. However, this system is not suitable for a long-time communication failure like the ARQ system, and uses extremely redundant data by encoding. However, the transmission efficiency is deteriorated, and the encoding and decoding processes become complicated, resulting in an increase in cost.

In order to compensate for the strength of the received radio wave,
A wireless receiving station often has an automatic gain control circuit (hereinafter, referred to as AGC) for automatically compensating the level of a received signal. The signal may fluctuate drastically due to fading due to reflection or the like. In such a case, the response of the AGC is delayed, and the reception level of the head portion of the received packet may be lower than the threshold, so that the packet may not be decoded. is there.

In the conventional ARQ system, a communication error caused by the response delay of the AGC can be recovered by retransmitting when the radio field intensity becomes strong. Many, again, wasteful retransmissions while radio waves are weak increase. On the other hand, in the error correction method, since the head of the packet cannot be read, it is useless at all.

[0010]

As described above, according to the conventional communication error recovery measure, a communication error caused by a high-speed change of the radio wave intensity due to the contamination of noise or the like can be recovered, but a communication having a longer cycle. With respect to obstacles, the effect was less effective, and there were many unnecessary and unnecessary retransmissions.

[0011] The present invention solves the above-mentioned problems, and can effectively and efficiently recover a communication error not only from a communication error caused by a high-speed change of radio wave intensity but also a communication failure having a longer period. A communication device is provided.

[0012]

According to one aspect of the present invention, there is provided a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station.
A communication error detection unit for detecting a packet communication error, and a retransmission timing setting unit for setting a timing for retransmitting the packet in which the communication error has occurred, wherein when the communication error detection unit detects a packet communication error,
A packet having a communication error is retransmitted from the radio transmitting station to the radio receiving station by delaying the retransmission timing set in the retransmission timing setting means.

According to a second aspect of the present invention, in the first aspect of the present invention, the retransmission timing is set so as to change according to the number of retransmissions of the same packet.

According to a third aspect of the present invention, in the first aspect of the present invention, a retransmission stop timing setting unit and a retransmission stop timing detecting unit are further provided, and the number of retransmissions of the same packet is determined by the retransmission stop timing setting unit. The transmission of the same packet is stopped when the retransmission stop timing detecting means detects that the predetermined value has been reached.

According to a fourth aspect of the present invention, in a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station in a predetermined communication cycle, a communication error detecting means for detecting a packet in which a communication error has occurred. And a retransmission cycle setting means for setting the number of retransmission cycles of the packet detected by the communication error detection means,
When the communication error detecting means detects a packet in which a communication error has occurred, a packet in which a communication error has occurred is retransmitted in a communication cycle after the number of retransmission cycles set in the retransmission cycle setting means. I do.

A fifth aspect of the present invention provides a radio receiving station having an automatic gain control circuit for automatically controlling a reception gain.
In a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication, the wireless transmitting station repeatedly and continuously transmits the same packet to a wireless receiving station, and the wireless receiving station performs transmission from the second and subsequent packets of the same packet continuously transmitted. , Wherein a received packet having no communication error is selected.

According to a sixth aspect of the present invention, there is provided a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station, wherein the same packet continuous transmitting means repeatedly and continuously transmits the same packet to the wireless receiving station; A communication error detecting means for detecting a communication error based on a status of a reception notification from the wireless receiving station for the repeated continuous transmission, and a retransmission timing for setting a retransmission timing of a packet having a communication error detected by the communication error detecting means Comprising a setting unit, when the communication error detection unit detects a packet having a communication error, based on the setting value of the retransmission timing setting unit, a packet having a communication error,
The same packet continuous transmitting means repeatedly and continuously retransmits.

According to a seventh aspect of the present invention, there is provided a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station having an automatic gain control circuit for automatically controlling a reception gain. Communication error detecting means for detecting a packet in which an error has occurred; and retransmission cycle setting means for setting the number of retransmission cycles of the packet detected by the communication error detecting means. A communication error occurrence packet retransmission communication cycle function unit for retransmitting a packet in which a communication error has occurred in a communication cycle subsequent to the number of retransmission cycles set in the retransmission cycle setting means when the detected packet is detected. The same packet repeatedly transmitted by the radio transmitting station to the radio receiving station repeatedly and the same packet is continuously transmitted. From the second and subsequent packets, the radio reception station is characterized by comprising the same packet repeatedly continuous transmission function unit so as to select the received packets without communication errors.

[0019]

Embodiments of the present invention will be described below.
This will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, the communication error detecting means 1 comprises:
When an error occurs in the packet communication result of the wireless communication 2, the error is detected, and a packet having a communication error is retransmitted 4 by delaying a predetermined retransmission timing preset in the retransmission timing setting means 3. When the packet transmitted by retransmission 4 again causes a communication error, the above retransmission cycle is repeated.

The above-mentioned retransmission timing may be a fixed value set to a constant value from the beginning, or may be changed in accordance with repetition of a retransmission cycle, for example, the retransmission interval may be gradually increased. With the latter setting, communication failures can be avoided if the communication failure time is longer than expected, for example, several tens of milliseconds or longer, or if the communication failure period and the retransmission interval are synchronized. Unnecessary retransmission can be prevented. Also,
The retransmission timing may be changed according to the communication environment.

As described above, by performing retransmission at an appropriate time interval, it is possible to recover a communication error caused by a long-period communication failure caused by fading, interruption of radio waves, and the like.

5 is a retransmission stop timing setting means, 6
Is a retransmission stop timing detecting means. The retransmission stop timing setting means 5 determines beforehand how many times retransmission 4 is repeated, or how long retransmission 4 is repeated, and how long retransmission 4 is stopped. The retransmission stop timing detecting means 6 monitors the state of the retransmission 4 and, when the number of retransmissions 4 or the like reaches the set value of the retransmission stop timing setting means 5, detects this and stops the retransmission 4 repetition. Thereby, it is possible to avoid unnecessary repetition of retransmission when the wireless receiving station S is not in the communicable area or when the power is turned off.

In the following embodiment, the configuration of this radio communication apparatus is a polling / selecting method having a communication cycle in which a radio transmitting station circulates a plurality of radio receiving stations and performs packet radio communication at a predetermined cycle. A more specific description will be given of a case where the present invention is applied to a wireless communication network and a case where the present invention is applied to a polling and selecting wireless communication network in which a wireless transmitting station repeatedly and repeatedly transmits the same packet to one wireless receiving station. I do.

First, polling having a communication cycle
An embodiment applied to a selecting type wireless communication network will be described with reference to FIGS.

FIG. 2 is an explanatory diagram illustrating a state in which data retransmission of the wireless communication apparatus according to the present invention is used in a polling and selecting wireless communication network having a communication cycle.

As shown in FIG. 2, normally, in the communication cycle, in each communication cycle 1, 2, 3,.
Master (wireless transmitting station) M is slave (wireless receiving station) S
The packet communication is performed in order of 1, S2,. Master M
When transmitting a command to each slave Sx (x = 1, 2, 3,...), The transmission monitoring timer TM
Start The slave Sx receives this packet and immediately returns a response (reception notification) to that effect to the master M upon decoding the command in the packet. This response (reception notification) reaches the master M within the time-up time set in the transmission monitoring timer TM, thereby confirming the normal completion of command (packet) communication.

If the packet carrying the command for the slave S2 is interrupted during the communication and does not reach the slave S2 as in the communication cycle 2 in FIG. 2, the transmission monitoring timer is left without a response (reception notification). The TM times out and a communication error is detected. In the retransmission timing setting means 2 (in this case, the retransmission cycle setting means), “1” is set as the retransmission cycle, and the master M transmits the next communication cycle 3 to the slave S2 in the communication cycle 2 immediately after. Retransmit the transmitted packet again.

In FIG. 2, the retransmitted command arrives at the slave S2 this time, and the slave 2 returns a response. (Including the case where the (reception notification) does not reach the master M), if the arrived response (reception notification) is not a reception notification of normal reception, retransmission is repeated in a further later communication cycle.

The data retransmission process in the communication cycle shown in FIG. 2 will be described in more detail with reference to FIGS.

FIG. 3 is a flowchart showing the flow of the communication master (wireless transmitting station) M side in FIG.

In step 301 of FIG. 3, communication processing is performed with respect to one slave Sx.
Then, it is checked whether the communication processing to all the slaves S1, S2,... Has been completed and all the slaves have been refreshed. If the refresh has not been completed (no), the process proceeds to step 303, the pointer is moved by one, and the process returns to step 301 to perform communication processing with the next slave. In step 302, if all the slaves have been refreshed (yes), one communication cycle is completed.

The details of the step 301 are shown below.
4 is a flowchart of FIG.
Now, the retransmission stop counter RSTP for the slave Sx
x is a preset “retransmission count RST for stopping retransmission”
P ”is checked. If retransmission has already been repeated and RSTPx matches RSTP (for example, five times) (yes), communication processing in this communication cycle is not performed, and the flow in FIG. 4 ends. Normally, the process proceeds to step 402 because they do not match (no).

In step 402, it is checked whether or not the retransmission waiting cycle counter RWCx for the slave Sx is "1". Since “RWCx = 1” (yes) indicates that this communication cycle is the timing of retransmission of the packet in which the communication error occurred earlier, the process proceeds to step 403 to reset the retransmission waiting cycle counter RWCx to 0, Add 1 to the retransmission stop counter RSTPx.
Note that the initial value of RSTPx is “0”. Next, in step 404, a retransmission packet having the same content as the packet addressed to the slave Sx in which the communication error occurred in the previous communication cycle is assembled.

In step 402, "RWCx ≠ 1" (n
If it is o), the process proceeds to step 405, and further checks whether or not the retransmission waiting cycle counter RWCx is “0”. As will be described later, this RWCx is “0” when there is no communication error, and when a communication error is detected, the number of communication cycles before retransmission RWC (in FIG. 2,
"1"). "RWCx = 0"
Since (yes) indicates that there is no communication error, the process proceeds to step 406 to assemble the next transmission packet. In step 405, if “RWCx） 0” (no),
Proceeding to step 407, the retransmission wait cycle counter RW
Cx is reduced by “1”, and the slave S in this communication cycle is reduced.
The communication to x is rested, and the flow of FIG. 4 ends.

When packet assembly is completed in step 404 or step 406, step 408
Go to and send the packet. Then, step 40
At 9, the transmission monitoring timer TM is started. The transmission monitoring timer TM sets a waiting time for receiving a packet transmission reception notification from the slave Sx. If there is no abnormality in the communication, the reception notification is obtained within this time.

After the transmission monitoring timer TM is started, in the next step 410, a packet reception notification is received from the slave Sx. When the transmission monitoring timer TM times out without receiving the packet reception notification or without receiving the packet reception notification, the process proceeds to step 411 to check for a communication error. That is, when the reception notification of the normal reception is transmitted from the slave Sx (no), the communication processing has been completed successfully, and therefore, in step 412, the retransmission stop counter RSTP is reset to “0”, and FIG. Ends the flow. In the case of a retransmission route via step 403, RS
This is because TP> 0. In step 411,
If "communication error occurred", that is, if step 411 has been reached after the transmission monitoring timer TM has timed out, or if a notification of abnormal reception has been sent from the slave Sx (yes), the process proceeds to step 413 and waits for retransmission. Set the cycle counter RWCx to “the number of communication cycles R before retransmission”
WC ”and the flow of FIG. 4 ends.

In the data retransmission processing in the communication cycle shown in FIGS. 2 to 4, the transmission monitoring timer TM and the processing means of step 411 are used as the communication error detecting means 1, and the retransmission timing setting means is used. As (retransmission cycle setting means) 3, a retransmission waiting cycle counter RWCx and a communication cycle number RWC setting means for retransmission are used.

The communication cycle number RWC setting means may be either a fixed value or a variable value depending on the communication environment. If repetition of retransmission is repeated, the communication environment may be worse than expected. In such a case, the setting value of the communication cycle number RWC setting means is set to gradually increase according to the number of retransmission repetitions. Thus, the frequency of useless retransmissions in a communication error occurrence environment can be reduced.

In the data retransmission processing in the communication cycle shown in FIGS. 2 to 4, the retransmission stop timing setting means 5 sets the number of retransmissions RST for stopping retransmission.
A P setting unit is used, and a retransmission stop counter RSTPx is used as a retransmission stop timing detecting unit.
The retransmission number RSTP setting means may be either a fixed value set or a variable set value according to use conditions.

When a communication error occurs in a communication cycle,
The time interval of retransmission in the subsequent communication cycle for this communication error often exceeds the normal communication disabled time of several msec to several tens msec due to fading, radio wave interference, noise, cutoff, etc., and therefore a communication error occurred. There is less needless retransmission to recover the packets.

Next, a case where the present invention is applied to a wireless communication network in which a wireless transmitting station repeatedly and repeatedly transmits the same packet to one wireless receiving station will be described with reference to FIGS.

FIG. 5 is an explanatory diagram illustrating a state in which data retransmission according to the present invention is used for repeated continuous transmission.

As shown in FIG. 5, normally, in repeated continuous transmission, the radio transmitting station M is connected to one radio receiving station Sx
(X = 1, 2 ‥‥) and the same packet as * (c) 1
/ 4, * (c) 2/4, * (c) 3/4, * (c) 4 /
4 and repeatedly transmitted four times in the example of FIG. After finishing the continuous transmission to one radio receiving station Sx, the master M activates a continuous transmission monitoring timer RTM. The slave Sx continuously receives the plurality of continuously transmitted identical packets, and immediately returns a reception notification (ACK) to that effect to the master M the number of times of continuous communication as soon as the command in the packet is decoded. The plurality of acknowledgments (ACK) reach the master M within the time-up time set in the continuous transmission monitoring timer RTM, thereby confirming the normal completion of packet communication.

If, as shown in FIG.
, The first packet (* (c) 1/4) is interrupted during communication and does not reach the slave S2, and the other three packets (* (c) 2/4, * (c) 3 / 4, *
If (c) 4/4) has reached the slave S2, the data contents such as the command can be determined from the received three packets. Also, as shown in FIG. 5, the reception notification (ACK) from the slave S2 has a poor communication state, and even if the third reception notification (ACK) does not reach the master M, the remaining three reception notifications (ACK) are not received. ), The master M can determine that the packet transmission content has arrived at the slave S2 and has been normally processed.

As described above, if continuous transmission is performed, a communication error due to a communication failure in a relatively short time can often be recovered in one continuous transmission, and the necessity of retransmission is considerably reduced. In particular, when the AGC is provided in the slave S to automatically adjust the gain of the received radio wave, the AGC tends to delay the response to the sudden deterioration of the received radio wave, which tends to cause a communication error. When the second and subsequent packets are received, AGC compensation can already be sufficiently performed, and normal reception often becomes possible.

If the communication failure continues for a long time, packets of continuous transmission * (c) 1/4, * (c) 2/4,.
Is not reached to the slave Sx or the continuous communication of the reception notification ACK from the slave Sx to the master M is not received, the continuous transmission monitoring timer RT
M times out and a communication error is detected. Then, according to the set values (number of times of “continuous transmission” until retransmission, elapsed time, etc.) set in retransmission timing setting means 2, retransmission continuous transmission is performed at an opportunity of subsequent continuous transmission.

If the communication error cannot be recovered even after repeating the retransmission continuous transmission, the retransmission is stopped according to the value set by the retransmission stop timing setting means 5.

The data retransmission process in the continuous transmission shown in FIG. 5 will be described in more detail with reference to FIGS.

FIG. 6 is a flowchart showing the processing flow on the master (wireless transmitting station) M side of the continuous communication in FIG.

In step 601 of FIG. 6, the slave Sx
It is checked whether or not the retransmission stop counter RSTPx corresponding to the “retransmission stop count RSTP for retransmission stop” is set in advance. If retransmission has already been repeated and matches RSTP (for example, 5 times) (yes), communication processing is not performed in this continuous transmission, and the flow in FIG. 6 ends. Normally, since they do not match (no), step 6
Go to 02.

In step 602, the retransmission wait timer RWTx for the slave Sx is set to the retransmission wait time RWT (for example, 50 m) set in the retransmission timing setting means.
It is checked whether or not sec. "RWTx> RW
"T" (yes) indicates that this continuous transmission is the timing of continuous retransmission of a packet in which a communication error has occurred previously, so that the process proceeds to step 603 and the retransmission wait timer RW
Tx is reset to 0, and a retransmission stop counter R
Add 1 to STPx. Note that the initial value of RSTPx is “0”. Next, in step 604, a retransmission packet having the same content as the packet addressed to the slave Sx having a communication error in the previous continuous transmission is assembled by using the same packet continuous transmission means, and is continuously retransmitted. At this time, the serial number / total number of consecutive transmissions is 1/4, 2
/ 4, 3/4, and 4/4.

In step 602, “RWTx ≦ RWT”
If (no), the process moves to step 605, and further checks whether or not the retransmission waiting timer RWTx is “0”. This RW
Tx is counted up from “0” when there is no communication error, and is counted up from “0” as time elapses, as described later, when a communication error is detected. "RWTx =
"0" (yes) indicates that there is no communication error,
Proceeding to step 606, the next transmission packet is assembled and transmitted continuously using the same packet continuous transmission means.
Also in this case, the serial number and the total number of continuous transmissions are sequentially incorporated into the packet, such as 1/4, 2/4, 3/4, and 4/4. In step 605, “RWTx ≠ 0” (n
If it is o), it means that continuous retransmission is waiting.
Ends the flow.

When the continuous transmission in step 604 or 606 is completed, subsequently, in step 607, the continuous transmission monitoring timer RTM is started. The continuous transmission monitoring timer RTM sets a wait time for receiving a notification of continuous packet transmission from the slave Sx. If there is no abnormality in the communication, the reception notification is obtained within this time.

After the continuous transmission monitoring timer RTM is started, in the next step 608, a packet reception notification is received from the slave Sx. Continuous transmission monitoring timer RTM without receiving packet reception notification or without receiving packet reception notification
When the time is up, the process proceeds to step 409, where the communication error detecting means checks for the presence or absence of a communication error. That is, when the reception notification of the normal reception is transmitted from the slave Sx (no), the communication processing has been completed successfully, and therefore, in step 610, the retransmission stop counter RSTP is reset to “0”, and FIG. Ends the flow. This is because RSTP> 0 in the case of the retransmission route via step 603. In step 609, "there is a communication error", that is, whether or not the continuous transmission monitoring timer RTM has timed out, and
When a notification of abnormal reception is sent from x, (yes
s), and proceed to Step 611, where the retransmission wait timer RWTx
(In the case of retransmission via step 604, the retransmission wait timer RWTx is reset and then restarted), and FIG.
Ends the flow.

FIG. 7 is a flowchart showing the processing flow on the slave (wireless receiving station) Sx side of the continuous communication in FIG.

In step 701 of FIG. 7, the first packet is received. Next, the process proceeds to step 702. In step 702, the total number of continuous transmissions (“4” in the example of FIG. 5) incorporated into the received packet is fetched, thereby predicting the number of continuous transmissions and the total number of continuous transmissions. The reception monitoring timer is set to a time-up value corresponding to the number of times, and is activated.

After step 702 is completed, the process proceeds to step 703, where the second and subsequent packets are sequentially received. When the packets of the total number of continuous transmissions are received or the reception monitoring timer times out, the process proceeds to step 704. Note that, when the reception of the total number of continuous transmission packets is completed before the reception monitoring timer times out, the reception monitoring timer is reset.

At step 704, it is checked whether or not there is a packet that can be normally received. If there is at least one normally received packet (yes), the process proceeds to step 705 for determining received data. If one packet has not been successfully received, the process proceeds to step 707.

The process of determining received data in step 705 is as follows.

(1) When all data of normally received packets match (including the case where only one packet is normally received): The data is determined as received data.

(2) When the data of the normally received packet differs depending on the packet and is of a plurality of types: The received data is determined by majority decision. When the maximum number is two or more, for example, the data of the packet having the smaller serial number among them is determined as the received data.

In step 706 following step 705, a reception notification packet is assembled on the basis of the determined reception data, using the normal reception result (the head of the received data, the execution result when the received data is a command, etc.) as data.

On the other hand, in step 707 when normal reception has failed, a reception notification packet for notifying a communication error is assembled.

When a polling signal is received from the master M after step 706 or step 707, the flow advances to step 708 to continuously transmit a reception notification to the master M, and the flow in FIG. The number of times of continuous transmission is assumed to be the same as the communication environment at the time of transmission from the master M to the slave Sx, and the total number of continuous transmissions from the master M previously taken ("4" in FIG. 5). Adjust to The continuous transmission of the reception notification is performed in step 60 of FIG.
At 8, the receiving process is performed by the master M.

In the data retransmission processing in the continuous transmission shown in FIGS. 5 to 7, the continuous transmission monitoring timer RTM and the step 609 are used as the communication error detecting means 1.
As the retransmission timing setting means 3, a retransmission waiting timer RWTx and a minimum waiting time RWT setting before retransmission are used.

The minimum waiting time RWT setting means may be a fixed value or a variable value according to the communication environment. When retransmission is repeated, the communication environment may be worse than expected. In such a case, the set value of the minimum waiting time RWT setting means is set to gradually increase according to the number of retransmission repetitions. Thus, the frequency of useless retransmissions in a communication error occurrence environment can be reduced.

In the data retransmission processing in the continuous transmission shown in FIGS. 5 to 7, the retransmission stop timing setting means 5 uses a retransmission count RSTP setting means for stopping retransmission, and detects the retransmission stop timing. As a means, a retransmission stop counter RSTPx is used. The retransmission number RSTP setting means may be either a fixed value set or a variable set value according to use conditions.

In the case of retransmission in this continuous transmission method,
As in the case of retransmission in the communication cycle shown in FIGS. 2 to 4, unnecessary retransmission is reduced. In addition, communication errors can often be recovered during continuous transmission before retransmission continuous communication is required, and communication failures of several msec to tens of msec due to fading, radio wave interference, noise, interruption, etc. are overcome. In addition, at this time, correct data can be extracted from a received radio wave having a weak radio field intensity by utilizing the characteristics of the AGC of the receiving slave.

A third embodiment of the present invention is a communication cycle function unit for retransmitting a communication error-occurring packet retransmitted in the communication cycle processing of FIGS. 2 to 4 and a continuous transmission processing of FIGS. 5 to 7. And a wireless communication device having the same packet repetition continuous transmission function unit for retransmitting the same packet. This 2
The two functional units can be appropriately selected and used according to the communication environment and communication contents, and have extremely high practical value when applied to FA networks such as programmable controllers, CNCs, and robot controllers.

[0072]

As will be understood from the above description, according to the first aspect of the present invention, when the communication error detecting means detects a packet communication error, the packet is delayed by the retransmission timing set in the retransmission timing setting means. Therefore, since a packet in which a communication error has occurred is retransmitted from the wireless transmitting station to the wireless receiving station, fading, radio wave interference, noise,
Due to interruption or the like, a communication error occurring during a communication disabled time period that lasts several msec to several tens msec can be efficiently recovered, and the reliability of wireless communication can be improved. Further, it is possible to avoid packet retransmission in the above-mentioned communication disabled time period in which a communication error occurs reliably.

Further, according to the second aspect of the present invention, the retransmission timing is changed in accordance with the number of retransmissions of the same packet repeatedly, so that adverse effects on other communications due to repetition of useless retransmission are further reduced. As a result, the overall efficiency of the wireless communication device can be increased.

According to the third aspect of the present invention, when the number of retransmissions of the same packet reaches a predetermined value, the transmission of the same packet is stopped. The adverse effect on communication can be further reduced, and the overall efficiency of the wireless communication device can be increased.

According to the fourth aspect of the invention, when performing packet radio communication in a communication cycle of a predetermined cycle, the number of retransmission cycles is set as retransmission timing, and a communication error occurs in a communication cycle subsequent to the number of retransmission cycles. Is retransmitted, the other communication on the wireless communication network can continue the communication without being affected by the retransmission at all.

According to the fifth aspect of the present invention, the radio transmitting station repeatedly and continuously transmits the same packet to the radio receiving station having the automatic gain control device for automatically controlling the reception gain. Since the receiving-side wireless receiving station selects a received packet having no communication error from the second and subsequent packets of the same transmitted packet, the wireless receiving station is caused by an extreme decrease in radio field intensity due to fading or the like. A communication error caused by a response delay of the automatic gain control circuit AGC on the side can be efficiently recovered, and the reliability of wireless communication can be improved.

According to the sixth aspect of the present invention, in the case of repeated continuous transmission, when the communication error detecting means detects a packet in which a communication error has occurred, a communication error is detected based on the set value of the retransmission timing setting means. Because the same packet continuous transmission means repeatedly and continuously retransmits the lost packet, it is possible to recover communication errors due to fading, radio wave interference, noise, interruption, etc. Packet retransmission can be avoided, and the adverse effect on the other communication on the wireless communication network that the unnecessary continuous retransmission time has can be eliminated.

Further, according to the invention of claim 7, a communication error occurring packet retransmission communication cycle function unit for retransmitting a packet in which a communication error has occurred during a communication cycle in a communication cycle after a predetermined number of retransmission cycles, Since the wireless receiving station has the same packet repetition continuous transmission function unit that selects a received packet without a communication error from the second and subsequent packets of the continuously transmitted same packet, the communication error occurrence packet is selected according to the communication environment. The retransmission communication cycle function unit and the same packet repetition continuous transmission function unit can be appropriately switched and selected, which is of great practical value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a state in which data retransmission according to the present invention is used in a communication cycle.

FIG. 3 is a flowchart showing an outline of a flow on a wireless transmitting station side in FIG. 2;

FIG. 4 is a flowchart showing a flow of a communication process in FIG. 3;

FIG. 5 is an explanatory diagram illustrating a state in which data retransmission according to the present invention is used for repeated continuous transmission.

FIG. 6 is a flowchart showing the flow of the communication in FIG. 5 on the wireless transmission station side.

FIG. 7 is a flowchart showing the flow of the communication in FIG. 5 on the wireless receiving station side.

FIG. 8 is an explanatory diagram showing an outline of a wireless communication network in the programmable controller system.

FIGS. 9A and 9B are explanatory diagrams showing examples of communication failure occurrence situations.

[Explanation of symbols]

 Reference Signs List 1 communication error detecting means 3 retransmission timing setting means 5 retransmission stop timing setting means 6 retransmission stop timing detecting means M wireless transmitting station (master) S1, S2, ‥‥ wireless receiving station (slave) RSTP retransmission stop count RSTPx retransmission Stop counter RWCx Retransmission wait cycle counter RWC Number of communication cycles before retransmission

Claims (7)

[Claims] In a wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station, a communication error detecting means for detecting a packet communication error, and a timing for retransmitting a packet having a communication error are set. Retransmission timing setting means for performing a retransmission timing set by the retransmission timing setting means when the communication error detection means detects a packet communication error, and wirelessly transmitting the packet having the communication error from the radio transmitting station. A wireless communication device for retransmitting to a receiving station. 2. The wireless communication apparatus according to claim 1, wherein the retransmission timing is set to change according to the number of retransmissions of the same packet repeatedly. 3. A retransmission stop timing setting means, and a retransmission stop timing detection means, further comprising: a retransmission stop timing detection means for detecting that the number of retransmissions of the same packet has reached the set value of the retransmission stop timing setting means. 2. The wireless communication apparatus according to claim 1, wherein when detecting the transmission of the same packet, the transmission of the same packet is stopped. 4. A wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station in a communication cycle of a predetermined cycle, wherein a communication error detecting means for detecting a packet in which a communication error has occurred; Retransmission cycle setting means for setting the number of retransmission cycles of a packet detected by the detection means, wherein when the communication error detection means detects a packet having a communication error, the number of retransmission cycles set in the retransmission cycle setting means A wireless communication apparatus characterized in that a packet in which a communication error has occurred is retransmitted in a communication cycle just after. 5. A radio communication apparatus in which a radio transmission station performs packet radio communication with a radio reception station provided with an automatic gain control circuit for automatically controlling a reception gain. Wireless communication apparatus wherein the same packet is repeatedly and continuously transmitted, and the wireless receiving station selects a received packet without a communication error from the second and subsequent packets of the same packet continuously transmitted. . 6. A wireless communication apparatus in which a wireless transmitting station performs packet wireless communication with a wireless receiving station, wherein the same packet continuous transmitting means repeatedly and continuously transmits the same packet to the wireless receiving station; Communication error detecting means for detecting a communication error based on the status of the reception notification from the wireless receiving station with respect to the packet, and retransmission timing setting means for setting a retransmission timing of a packet having a communication error detected by the communication error detecting means. When the communication error detecting means detects the packet in which the communication error has occurred, the same packet continuous transmitting means repeatedly and continuously retransmits the packet in which the communication error has occurred based on the setting value of the retransmission timing setting means. Wireless communication device. 7. A radio communication apparatus in which a radio transmission station performs packet radio communication with a radio reception station having an automatic gain control circuit for automatically controlling a reception gain, comprising: (1) a packet in which a communication error has occurred; And a retransmission cycle setting means for setting a retransmission cycle number of the packet detected by the communication error detecting means, wherein the communication error detecting means detects a packet having a communication error. A communication error occurrence packet retransmission communication cycle function unit for retransmitting a packet in which a communication error has occurred in a communication cycle after the number of retransmission cycles set in the retransmission cycle setting means; The same packet is repeatedly and continuously transmitted to the wireless receiving station, and the second and subsequent packets of the same packet transmitted continuously are transmitted. A wireless communication apparatus comprising: a same packet repetition continuous transmission function unit that allows a wireless receiving station to select a received packet without a communication error from a packet.