JP3308423B2 - Wireless data communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CSMA (carrier-sequence) in which a transmission wave of a radio station is controlled by observing a carrier wave to control a transmission opportunity of the radio station.
The present invention relates to a wireless data communication device that employs a carrier detection multiple access (nse multiple-access) method.

[0002]

2. Description of the Related Art In the CSMA system, each radio station monitors the use status of a radio wave based on the reception state of a carrier wave (carrier). When a radio wave is being received, another station recognizes that another station is transmitting. Even if there is information that the station wants to transmit to another station, the transmission is postponed. By doing so, collision of transmission radio waves between wireless stations is avoided, and it is often used in a so-called simplex wireless data communication system in which a transmission radio channel and a reception radio channel are the same.

A general wireless data communication device that can be a radio station adopting the CSMA system includes a carrier detection unit that outputs a signal indicating a reception state of a carrier by an antenna, and monitors an output signal from the detection unit. The transmission control means is provided with a microcomputer or the like which prohibits the transmission of the own station when the carrier wave reception state is indicated. Note that some wireless data communication devices of this type are configured to stop the operation of the reception function unit when the own station is transmitting to save power, etc. In this case, the transmission radio wave from the own station is used. No carrier is detected.

A communication protocol in wireless communication basically indicates that a receiving station normally receives information or a command in response to transmission of information (data) or a command (command), that is, command transmission. Response transmission, so-called response transmission is returned. For this reason, assuming a case where a plurality of stations transmit commands at substantially the same time, after one station ends command transmission, the receiving station transmits a response to the transmitting station, and then another The transmission opportunity may be controlled so that the station performs command transmission.

However, in this type of conventional wireless data communication apparatus, transmission of the own station is prohibited only when a carrier is detected by the carrier detection means. Another station may start sending commands. Therefore, the timing of the response from the receiving station is different for the station that has transmitted the command, and it is necessary to determine a communication abnormality while taking this into account, thus complicating the processing of the abnormal system. Further, since information and commands from a plurality of stations may be received at the same time, it is necessary to prepare reception buffers for the number of other stations.

Accordingly, recently, the output signal from the carrier detection means is monitored, and if the non-carrier reception state lasts for a predetermined time, a signal indicating the non-carrier reception state is output until the carrier reception state is reached. A time delay means is provided, and an output signal from the delay means is monitored by a transmission control means. When the carrier signal reception state is indicated, the command transmission of the own station is prohibited, and the response transmission can be transmitted regardless of the carrier reception state. Such a wireless data communication device has been devised.

FIG. 8 is a block diagram showing a configuration of a main part of such a conventional wireless data communication apparatus, and shows a CPU (central proc) incorporated in a one-chip microcomputer.
essing unit: Central processing unit 1, ROM (read only)
memory: read-only memory 2 and RAM (random acc
ess memoly: a memory that can be read and written at any time) 3, a radio circuit unit 4, and a non-receiving time delay circuit 5.

The radio circuit unit 4 generates a transmission message for command transmission and response transmission in accordance with a command from the CPU 1, and modulates a transmission message given from the transmission unit 4a at a predetermined frequency to the antenna 6 And a demodulation unit 4c for demodulating the radio signal received by the antenna 6, receiving the demodulated signal by the demodulation unit 4c and instructing the CPU 1 to output the output of the demodulation unit 4c. Carrier from signal to antenna 6
And a carrier sense section 4e which outputs the monitored content to the non-reception time delay circuit 5 as a carrier signal CS as a binary signal.

When the operation of the reception function unit is stopped while the own station is transmitting to save power, etc., a changeover switch is provided between the antenna 6 and the modulation unit 4b and the demodulation unit 4c. Normally, the antenna 6 is connected to the demodulation unit 4c to disconnect the modulation unit 4b from the antenna 6, and during transmission, the modulation unit 4
The antenna b is connected to the antenna 6 so that the antenna 6 and the demodulation unit 4c are separated from each other.

The non-reception time delay circuit 5 monitors the carrier sense signal CS output from the carrier sense section 4c and, when detecting the state of receiving a carrier wave, sets the carrier sense delay signal CST output to the CPU 1 to the state of receiving a carrier wave. The carrier sense signal CS detects the absence of carrier wave reception, and if this state lasts for a preset time, sets the carrier sense delay signal CST to the carrier absence state.

The CPU 1 is programmed to control command transmission and response transmission according to the transmission algorithm shown in FIG. That is, in the case of command transmission for transmitting information (data), a command (command), or the like to another station, the carrier sense delay signal CST from the non-reception time delay circuit 5 is checked, and a signal indicating the absence of carrier wave reception (for example, When the signal is a low-level signal “0”), command transmission is performed. When the signal is a signal indicating no carrier reception state (for example, a high-level signal “1”), command transmission is prohibited and postponed. On the other hand, in the case of response transmission, which is a response to command reception, response transmission is performed regardless of the state of the carrier sense delay signal CST.

In the conventional apparatus having such a configuration, after detecting the delay time by the non-reception time delay circuit 5, that is, the state in which the carrier sense signal CS does not receive the carrier, the carrier sense delay signal CST is changed to the state in which the carrier does not receive. By setting the time until the station that received the information or the command returns a response, the time until the station that received the information or the command returns a response by setting the time until the command can be transmitted from the command reception to the transmission of the response. Since command transmission is prohibited, response transmission is performed promptly for command transmission, and stable wireless communication is guaranteed.

[0013]

However, the following problems still need to be solved in the conventional wireless data communication apparatus having the non-reception time delay means. That is, since wireless communication does not have a physical line unlike wired communication, a radio wave emitted from an electronic device other than a wireless device may be detected as a carrier. This type of radio wave is called an interference radio wave. For example, when a wireless data communication system is constructed using the 2.4 GHz band spread spectrum communication method, a radio wave emitted from a microwave oven or the like is included in the used band, and the interference radio wave causes a state in which a carrier wave is received. It may be.

In a conventional wireless data communication apparatus provided with a non-reception time delay means, even if an interference radio wave is received as a carrier, the delay time by the non-reception time delay means after the interference radio wave disappears. Since the transmission opportunity cannot be obtained until after the elapse of the transmission time, the transmission opportunity is reduced and the communication efficiency is reduced.

The present invention has been made in view of such circumstances, and a purpose of the present invention is to make it possible to promptly transmit a response to a command transmission and to ensure stable wireless communication. An object of the present invention is to provide a wireless data communication device capable of minimizing loss of transmission opportunity due to interference radio waves and improving communication efficiency in an environment where interference radio waves exist.

[0016]

According to the present invention, there is provided a carrier detecting means for outputting a signal indicating a receiving state of a carrier by means of an antenna, and an output signal from the detecting means for monitoring the output signal from the detecting means, and a carrier receiving state is set in advance. A reception time delay means for outputting a signal indicating the presence of carrier wave until the state of no carrier wave reception when the time of 1 is maintained, and an output signal from the reception time delay means is monitored, and the carrier wave reception is performed after the reception of the carrier wave is detected. A non-reception time delay unit that outputs a signal indicating a carrier reception state until the absence state lasts for a preset second time; an output signal from the non-reception time delay unit and an output signal from the carrier detection unit; And a transmission control means for prohibiting the transmission of the own station when at least one of the signals indicates a state of receiving a carrier wave.

Further, according to the present invention, transmission detection means for outputting a signal indicating the transmission state of the own station is provided, and reception time delay means is provided for monitoring an output signal from the carrier wave detection means and an output signal from the transmission detection means. When the carrier reception state or the own station transmission state lasts for a preset first time, a signal indicating the carrier reception state is output until the carrier reception state or the own station non-transmission state is reached. It is.

[0018]

According to the present invention having such a configuration, when the carrier wave detecting means detects the presence of the carrier wave, the transmission of the own station is prohibited. When the carrier reception state lasts for a preset first time, the output signal from the reception time delay means becomes a signal indicating the carrier reception state. Then, the output signal from the non-reception time delay means also becomes a signal indicating that the carrier wave has been received. Thereafter, when the carrier wave non-reception state is detected by the carrier wave detection means, the output signal from the reception time delay means becomes a signal indicating the carrier wave non-reception state. When the non-reception state of the carrier wave lasts for a preset second time, the output signal from the non-reception time delay means becomes a signal indicating the non-reception state of the carrier wave. At this time, the transmission of the own station becomes possible.

However, when the carrier wave receiving state is detected by the carrier wave detecting means, but the carrier wave receiving state is not maintained for the first time, the output signal from the non-reception time delay means is the absence of the carrier wave receiving. The signal indicating the state remains. Therefore, when the output signal of the carrier detection means is in a state of no carrier reception, transmission of the own station becomes possible. That is, the carrier detected by the carrier detector is the first carrier.
In the case of the interference radio wave shorter than the time, the transmission of the own station becomes possible at the time when it is no longer detected.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIG. 1, a plurality of wireless data communication devices (wireless devices A, B, C, D,...) 10 are capable of wireless communication with each other. A case will be described in which each wireless data communication device 10 uses a type that stops the operation of the reception function unit when the own station is transmitting.

FIG. 2 is a block diagram showing a configuration of a main part of the wireless data communication apparatus 10, and each unit has the same configuration. That is, the wireless data communication device 10 constitutes a control unit main body, and information (data) and a command (command) are provided.
CPU 11 for controlling the control of transmission of information and the like, processing of received information and commands, ROM 12 for storing programs such as transmission algorithms, RAM 13 for temporarily storing transmission information and reception information, and information (data) Under the control of the CPU 11, the wireless circuit unit 14 performs transmission of commands (commands), so-called command transmission and reception thereof, and transmission of responses indicating that information and commands have been normally received, so-called response transmission and reception thereof. These are connected by a bus line 15.

The radio circuit unit 14 generates a transmission message for command transmission and response transmission in accordance with a command from the CPU 11, and modulates a transmission message given from the transmission unit 14a at a predetermined frequency to an antenna. And a demodulation unit 14c for demodulating a radio signal received by the antenna 16, the demodulation unit 14c.
c, receiving the demodulated reception signal and monitoring the receiving state of the carrier by the antenna 16 from the output signals of the receiving unit 14d and the demodulating unit 14c instructing the CPU 11;
It comprises a CPU 11 and a carrier sense section 14e as a carrier detection means for outputting the monitored content as a binary carrier state signal CS to one input terminal of the CPU 11 and the two-input OR gate 17.

Although not shown, a changeover switch is interposed between the antenna 16 and the modulator 14b and the demodulator 14c.
Normally, the antenna 16 and the demodulation unit 14c are connected to each other to connect the modulation unit 1
4b and the antenna 16 are separated from each other.
4b is connected to the antenna 16, and the antenna 16 and the demodulator 14 are connected.
c is controlled to be separated from c.

The transmitting section 14a sets the transmission state of its own station to 2
The OR gate 1 is used as a text state signal Tx of a value signal.
7 is output to the other input terminal.
4a constitutes transmission detection means.

The output terminal of the OR gate 17 is connected to a reception time delay circuit 18. That is, the reception time delay circuit 18 is provided with the logical sum output of the carrier sense signal CS from the carrier sense unit 14e and the text state signal Tx from the transmission unit 14a.

The reception time delay circuit 18 monitors the carrier state signal CS from the carrier sense section 14e and the text state signal Tx from the transmission section 14a based on the logical sum output of the OR gate 17, and detects whether the carrier wave is received or the local station. When the transmission state lasts for a preset first time, a binary signal indicating the carrier reception state is output to the non-reception time delay circuit 19 until the carrier reception absence state or the own station transmission absence state is reached. The reception time delay circuit 1
Reference numeral 8 denotes a reception time delay unit.

The non-reception time delay circuit 19 monitors the output signal from the reception time delay circuit 18, and sets the carrier wave reception state from the state where the carrier wave is received until the state where the carrier wave is not received for a predetermined second time. The CPU uses a binary signal indicating the reception state as a carrier sense delay signal CST.
11 in which the non-reception time delay circuit 1
Reference numeral 9 denotes non-reception time delay means.

In this embodiment, for the sake of explanation, the signals output from the carrier sense unit 14e, the reception time delay circuit 18 and the non-reception time delay circuit 19 indicate that the carrier reception state is a high level signal "1". , The no-reception state is a binary signal indicated by a low-level signal “0”, and the signal output from the transmitting unit 14a indicates the own station's transmission state by a high-level signal “1”, and no transmission is performed. The state is a binary signal indicated by a low level signal “0”.

The CPU 11 is programmed to control command transmission and response transmission according to the transmission algorithm shown in FIG. That is,
In the case of command transmission for transmitting information (data), a command (command), or the like to another station, as ST (step) 1, the carrier sense signal CS from the carrier sense unit 14e is checked. If the carrier sense signal CS is a low level signal "0", that is, indicates that there is no carrier reception, the non-reception time delay circuit 1 is set as ST2.
9 is checked. When the carrier sense delay signal CST also indicates the low level signal “0”, that is, the state in which no carrier wave is received, the control unit 14a controls the transmitting unit 14a to perform command transmission as ST3.

On the other hand, when the carrier sense signal CS indicates a high level signal "1" in ST1, that is, indicates that there is a carrier reception, or in ST2, the carrier sense delay signal CST indicates a high level signal "1". That is, when indicating the state with carrier wave reception, the transmission operation is prohibited and the transmission is postponed. Here, the CPU 11 constitutes transmission control means.

On the other hand, in the case of a response transmission which is a response to the reception of the command, the transmission unit 14a is controlled to perform the response transmission in ST3 without performing the signal determination processing in ST1 and ST2.

In the present embodiment configured as described above,
The wireless communication specifications of each wireless device A, wireless device B, wireless device C, and wireless device D as the wireless data communication device 10 shown in FIG.
Radio wave format = spread spectrum method (direct spread), radio frequency band = 2.4 GHz band, communication method = simplex method, data communication speed = 1 Mbps. Also, set the command transmission time to 1
0 ms or more, the maximum processing time of the receiving station required from command reception to response transmission is 7 ms, the response transmission time is 1 ms, the maximum time when the carrier sense signal CS becomes a high-level signal “1” due to interference radio waves is 4 ms, and the reception time The first time set in the delay circuit 18 is 5 ms, and the second delay time set in the non-receiving time delay circuit 19 is 8 ms.

In this case, first, the radio device A transmits a command of 10 ms to the radio device B, whereby the radio device B performs a reception process of 7 ms, and then transmits a response of 1 ms to the radio device A. Next, after the carrier sense signal CS becomes "1" for 4 ms due to the interference radio wave, the radio device C transmits a command of 10 ms to the radio device B, whereby the radio device B performs the reception process of 7 ms, FIG. 4 shows a timing chart when a 1 ms response is transmitted to the device C.

FIG. 4A shows a transmission output signal, a carrier sense signal CS and a carrier sense delay signal CST in the radio A, and FIG.
2 shows a transmission output signal, a carrier sense signal CS, and a carrier sense delay signal CST in FIG. 1, and FIG. 2C shows a transmission output signal, a carrier sense signal CS, and a carrier sense delay signal CST in the wireless device C.

The wireless data communication apparatus having the conventional non-reception time delay circuit 5 shown in FIG.
FIG. 5 is a timing chart similar to FIG.
Shown in

That is, in the apparatus of this embodiment, the radio A
At the transmission output timing, the carrier sense signals CS of the other wireless devices B and C become high-level signals "1" indicating that there is carrier wave reception. Here, the transmission output time is 10 ms, and the first time set in the reception time delay circuit 18 is 5 ms.
5 ms after the start of transmission output, the carrier sense delay signal CST
Becomes a high-level signal "1" indicating that there is carrier wave reception.

Thereafter, when the transmission output of the radio A disappears, the carrier sense signals CS of the other radios B and C return to the low level signal "0" indicating the no carrier reception state. However, the carrier sense delay signal C of each of the wireless devices A, B, and C
ST is the second set in the non-reception time delay circuit 19.
The high level signal "1" is maintained until the time of 8 ms elapses. Accordingly, the command transmission operation of each of the wireless devices A, B, and C is prohibited.

After a lapse of 7 ms from the transmission output of the wireless device A, the wireless device B transmits a response of 1 ms to the wireless device A. At this time, the radio A and the radio C
Of the carrier sense signal CS becomes a high level signal “1” indicating the carrier detection state, but the response transmission time is 1 ms.
Since the time is shorter than the first time 5 ms set in the reception time delay circuit 18, the signal output from the reception time delay circuit 18 of each of the radios A, B, and C has a low level indicating a carrier non-detection state. The signal remains at "0". Therefore, the carrier sense delay signal CST of each of the radios A, B, and C returns to the low level signal “0” indicating the non-reception of the carrier when 8 ms elapse after the radio output from the radio A is stopped. Thus, each of the wireless devices A, B, and C can transmit a command.

Here, when an interfering radio wave for the 2.4 GHz band spread spectrum communication system is generated from an electronic device other than the radio device in the system, the carrier sense signal CS of each of the radio devices A, B, and C is in a state where the carrier wave is detected. , Indicating that the command transmission is prohibited for each of the wireless devices A, B, and C. However, the time during which the carrier sense signal CS becomes the high-level signal “1” due to the interference radio wave is 4 ms at the maximum, and is shorter than the first time 5 ms set in the reception time delay circuit 18. B, C
Does not become the high level signal "1". Therefore, the carrier sense signal CS is a low level signal “0” indicating that there is no carrier reception.
At this point, the wireless devices A, B, and C can transmit commands.

At this time, assuming that the radio C transmits information or a command to the radio B, the radio C starts command transmission. After that, radio A becomes radio B
Operates in the same way as when a command is sent to

On the other hand, in the case of the conventional device shown in FIG.
The carrier sense signal CS and the carrier sense delay signal CS of the other radios B and C at the transmission output timing of the radio A
T becomes a high-level signal "1" indicating the state of receiving a carrier wave. Thereafter, when the transmission output of the wireless device A disappears, the carrier sense signals CS of the other wireless devices B and C return to the low level signal “0” indicating the no-carrier-reception state. However, the carrier sense delay signal CST of each of the radios B and C keeps the high level signal “1” until the time 8 ms set in the non-reception time delay circuit 5 elapses.
The command transmission operation of C is prohibited.

After a lapse of 7 ms from the transmission output of the wireless device A, a response transmission of 1 ms is performed from the wireless device B to the wireless device A. At this time, the radio A and the radio C
Becomes a high level signal "1" indicating a carrier detection state. Further, the carrier sense delay signal CST of the wireless device A becomes the high level signal “1”, and the carrier sense delay signal CST of the wireless device C maintains the high level signal “1”. And after receiving the response transmission,
The high level signal "1" is maintained until 8 ms elapses.

Here, if an interference radio wave for the 2.4 GHz band spread spectrum communication system is generated from an electronic device other than the wireless device in the system before the lapse of 8 seconds, the carrier of each of the wireless devices A, B and C is generated. The sense signal CS becomes a high level signal "1". Further, the carrier sense delay signal CST of the radio B becomes the high level signal “1”, and the carrier sense delay signals CST of the other radios A and C maintain the high level signal “1”. When 8 ms elapse after the carrier wave due to the interference radio wave is no longer detected, the carrier sense delay signal CST of each of the wireless devices A, B, and C becomes a low level signal “0”, and each of the wireless devices A, B, and C receives a command. Transmission becomes possible.

At this time, assuming that the wireless device C is transmitting information or a command to the wireless device B, the wireless device C starts command transmission. After that, radio A becomes radio B
Operates in the same way as when a command is sent to

Therefore, as is apparent from a comparison between FIG. 4 and FIG. 5, conventionally, when an interference radio wave is generated, a command cannot be transmitted until a time set in the non-reception time delay circuit 5 has elapsed. However, in the present embodiment, if the time when the carrier sense signal CS becomes the high-level signal “1” is an interference radio wave shorter than the first time set in the reception time delay circuit 18, the carrier wave due to this interference radio wave is detected. Command transmission becomes possible at the point when it has disappeared.

As described above, the wireless data communication apparatus 10 of this embodiment monitors the reception state of the carrier wave on the antenna 16 by the carrier sense section 14e. The low-level signal “0” indicating the no-carrier-wave receiving state is changed to the high-level signal “1” indicating the no-carrier-receiving state, and the command transmission of the own station is prohibited. Then, this carrier wave reception present state is set to the first time preset in the reception time delay circuit 18.
, The output signal from the reception time delay circuit 18 changes to a high-level signal "1" indicating that there is carrier wave reception. Then, the non-reception time delay circuit 1
9, the carrier sense delay signal CST
Also changes to a high-level signal "1" indicating the carrier reception state.

Thereafter, when the carrier sense section 14e detects the state of no carrier reception, the output signal from the reception time delay circuit 18 changes to a low level signal "0" indicating the state of no carrier reception. When this non-reception time state lasts for a second time preset in the non-reception time delay circuit 19, the carrier sense delay signal CST from the non-reception time delay circuit 19 also becomes a low level indicating the non-reception time state. The signal changes to "0". At this time, if the carrier sense signal CS from the carrier sense unit 14e is a low level signal "0", transmission of the own station becomes possible.

However, if the carrier sense section 14e detects the state with carrier wave reception, but the state with carrier wave reception has not continued for the first time or more, the output from the reception time delay circuit 18 will be the absence of carrier wave reception. The low level signal “0” indicating the state is maintained. As a result, the carrier sense delay signal CST from the non-reception time delay circuit 19 also maintains the low level signal “0” indicating the absence of carrier wave reception. Therefore, when the carrier sense unit 14e detects the state of no carrier wave reception, the own station can transmit.

Therefore, if the maximum time during which the carrier sense signal CS becomes the high-level signal "1" due to the interference radio wave is shorter than the first time set in the reception time delay circuit 18, this interference radio wave is detected. At that point, transmission of the own station becomes possible, loss of transmission opportunities due to interference radio waves can be suppressed to a minimum, and communication efficiency in an environment where interference radio waves exist can be improved.

In this embodiment, the non-reception time delay circuit 1
9, the carrier sense delay signal CST is changed to the low level signal "0" for the second time set in the circuit 19, that is, after the carrier sense signal CS becomes the low level signal "0" indicating the state of no carrier reception. Is set to be equal to or longer than the maximum processing time of the receiving station required from the command reception to the response transmission, the response transmission is promptly performed in response to the command transmission. Therefore, stable wireless communication can be guaranteed even if the number of wireless devices increases and the amount of communication traffic increases.

For example, the wireless communication system of this embodiment
A plurality of wireless POSs that register product sales data
(Point of sales: sales starting point information management) In a case where the present invention is applied to a wireless POS system in which a terminal and a host computer for centrally controlling each POS terminal are connected by a wireless line, each POS terminal sends the information to the host computer. Frequently, an inquiry message of product information is wirelessly transmitted for product sales data registration processing, and promptness is required for returning the product information in response to this inquiry. On the other hand, in a supermarket or the like in which this type of POS system is introduced, a microwave oven for heating food purchased by customers may be installed near a checkout place where each POS terminal is installed.

In such a case, by incorporating the function as the wireless data communication device 10 of the present invention into the wireless POS terminal, it becomes possible to minimize the influence of the interference radio wave from the microwave oven and to obtain the product information. Responsiveness to the response to the inquiry, and furthermore, speeding up the merchandise sales data registration processing at each POS terminal can be achieved.

By the way, in the case of the wireless data communication apparatus 10 of the type in which the operation of the receiving function unit is stopped when the own station is transmitting, as in the present embodiment, the carrier sense is performed while the own station is transmitting a command. The signal CS remains at the low level signal “0”. Therefore, if the transmitting section 14a does not have the transmission detecting means, the carrier sense delay signal CST does not become the high-level signal "1" indicating the carrier receiving state for the transmitting operation of the own station. As a result, the transmitting station can transmit the next command immediately after completing the command transmission, but the other stations including the receiving station change the carrier sense delay signal CST to the high-level signal “1” indicating the carrier receiving state. Therefore, a transmission opportunity for command transmission cannot be obtained.

Therefore, in this embodiment, the transmitting section 14a is provided with a function as transmission detecting means for outputting a binary text state signal Tx indicating the transmission state of its own station. The OR output of the OR gate 17 with the carrier sense signal CS from the section 14e is given to the reception time delay circuit 18, and the reception time delay circuit 1
8 is the carrier status signal CS and the text status signal Tx
If the carrier reception state or the own station transmission state lasts for a preset first time, the binary signal indicating the carrier wave reception state is not changed until the carrier wave non-reception state or the own station non-transmission state is reached. The signal is output to the reception time delay circuit 19.

With such a configuration, the carrier sense delay signal CST becomes the high level signal "1" indicating the carrier reception state in the transmitting station similarly to the other stations for the transmitting operation of the own station. Command transmission opportunities can be equalized.

In the case of the wireless data communication apparatus 10 of the type which does not stop the operation of the receiving function unit even when the own station is transmitting, as shown in FIG. , And the OR gate 17 may be omitted to directly input the carrier sense signal CS from the carrier sense unit 14e to the reception time delay circuit 18.

FIG. 7 shows a timing chart similar to that of FIG. 4 in the case where the wireless data communication device 10 shown in FIG. 6 is replaced by wireless devices A, B and C. That is, the timing chart shown in FIG. 7 is different from the timing chart of FIG. 4 in that the carrier sense signal CS is a high-level signal “1” with respect to the transmission output of the own station.
The timings at which the B and C carrier sense signals CS and the carrier sense delay signal CST simultaneously maintain the low level “0” coincide. Therefore, the same effect as the wireless data communication device 10 shown in FIG. 2 can be obtained also in the wireless data communication device 10 shown in FIG.

In the above embodiment, the signals output from the carrier sense section 14e, the reception time delay circuit 18 and the non-reception time delay circuit 19 indicate that the carrier is being received by a high level signal "1". The absent state is a binary signal indicated by a low-level signal “0”, and the signal output from the transmitting unit 14a indicates the own station's transmission state by a high-level signal “1”, and the non-transmission state is a low-level signal. Although the binary signal indicated by “0” is used, the state of reception of a carrier is indicated by a low-level signal “0”, and the state of no reception is indicated by a high-level signal “1”. May be represented by a low-level signal “0”, and the no-transmission state may be represented by a binary signal represented by a high-level signal “1”.

[0059]

As described in detail above, according to the present invention, it is possible to promptly transmit a response to a command transmission, secure stable wireless communication, and minimize the loss of transmission opportunities due to interference radio waves. It is possible to provide a wireless data communication device which can suppress the interference to a minimum and can improve the communication efficiency in an environment where interference radio waves exist.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a wireless communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of the wireless data communication device in the embodiment.

FIG. 3 is a flowchart showing a transmission algorithm of the wireless data communication device in the embodiment.

FIG. 4 is a diagram showing an example of a communication time chart of the wireless data communication device in the embodiment.

FIG. 5 is a diagram showing an example of a communication time chart of a conventional wireless data communication device.

FIG. 6 is a main block diagram of a wireless data communication apparatus according to another embodiment of the present invention.

FIG. 7 is a diagram showing an example of a communication time chart of the wireless data communication device in another embodiment.

FIG. 8 is a block diagram of a main part of a conventional wireless data communication device.

FIG. 9 is a flowchart showing a transmission algorithm of a conventional wireless data communication device.

[Explanation of symbols]

 Reference Signs List 10 wireless data communication device 11 CPU (transmission control means) 14 wireless circuit section 14a transmission section (transmission detection section) 14b modulation section 14c demodulation section 14d reception section 14e carrier sense section (carrier detection section 16 ... Antenna 17 ... Oregade 18 ... Reception time delay circuit 19 ... Non-reception time delay circuit

Claims (2)

(57) [Claims] 1. A carrier wave detecting means for outputting a signal indicating a receiving state of a carrier wave by an antenna, and a carrier wave receiving state is monitored when an output signal from the detecting means is monitored and a carrier wave receiving state is maintained for a first predetermined time. A reception time delay unit that outputs a signal indicating a carrier reception state until the state is reached, and a carrier reception absence state that is set in advance by monitoring an output signal from the reception time delay unit and entering a carrier reception state. A non-reception time delay means for outputting a signal indicating that a carrier wave is present until the time of 2 is maintained; and monitoring an output signal from the non-reception time delay means and an output signal from the carrier wave detection means. A wireless data communication apparatus comprising: a transmission control unit that prohibits transmission of the own station when a signal indicates a state of receiving a carrier wave. 2. A carrier detecting means for outputting a signal indicating a receiving state of a carrier by an antenna, a transmitting detecting means for outputting a signal indicating a transmitting state of the own station, an output signal from the carrier detecting means and the transmission detecting Monitoring the output signal from the means, and when the carrier reception state or the own station transmission state lasts for a first predetermined time, indicates the carrier reception state until the carrier reception state or the own station non-transmission state is reached. A reception time delay means for outputting a signal, and a second state in which the output signal from the reception time delay means is monitored and the state without carrier wave reception is set after the state becomes the state with carrier wave reception.
Non-reception time delay means for outputting a signal indicating the presence of the carrier wave until the time of the non-reception time, monitoring the output signal from the non-reception time delay means and the output signal from the carrier wave detection means, at least one of the signals And a transmission control means for prohibiting transmission of the own station when indicates the presence of carrier wave reception.