JPH08251066A - Radio data communication device - Google Patents

Abstract

PURPOSE: To guarantee a stable radio communication and improve communication efficiency in environment wherein an interference radio wave is present by inhibiting transmission from a local station only when a carrier reception state lasts for a specific time. CONSTITUTION: A reception time delay circuit 18 monitors the carrier state signal CS from a carrier sense part 141 and the text state signal Tx from a transmission part 14a with the output of an OR gate 17. When a carrier reception state or local station transmission state lasts for the specific time, a binary signal indicating the reception state is sent to a non-reception time point delay circuit 19 until a carrier nonreception state or local station nontransmission state is entered. The circuit 19 monitors the output signal of the circuit 18 and sends a binary signal indicating the carrier presence state as a carrier sense delay signal CST to a CPU 11 until the carrier nonreception state continues for the specific time after the carrier reception state is entered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention observes a carrier wave and controls the transmission opportunity of its own station to avoid collision of radio waves transmitted between radio stations.
nse multiple-access: A wireless data communication apparatus adopting a carrier detection multiple access method.

[0002]

2. Description of the Related Art In the CSMA system, each radio station monitors the use status of radio waves by the reception state of a carrier wave, and when it receives a carrier wave, it recognizes that another station is transmitting, and Even if a station has information that it wants to send to another station, the transmission is postponed. By doing so, collisions of radio waves transmitted between radio stations are avoided, which is often used in so-called simplex radio data communication systems in which the transmission radio channel and the reception radio channel are the same.

A general wireless data communication device which can be a wireless station adopting the CSMA system monitors carrier wave detecting means for outputting a signal indicating a receiving state of a carrier wave by an antenna, and an output signal from this detecting means, It is provided with a transmission control means such as a microcomputer which prohibits the transmission of its own station when the state of receiving the carrier wave is indicated. Note that some wireless data communication devices of this type are designed to save power by, for example, stopping the operation of the receiving function unit when the local station is transmitting, and in this case, the radio wave transmitted from the local station is The carrier wave due to is not detected.

By the way, the communication protocol in wireless communication basically indicates that the receiving station normally receives the information or command in response to transmission of information (data) or command (command), so-called command transmission. Sending a response, so-called response sending is returned. Therefore, assuming a case where a plurality of stations send commands at almost the same time, after one station finishes sending commands, the receiving station sends a response to the sending station, and then another The transmission opportunity may be controlled so that the station transmits the command.

However, in the conventional wireless data communication apparatus of this type, the transmission of its own station is prohibited only when the carrier wave is detected by the carrier wave detecting means, so that before the receiving station transmits a response. Sometimes another station started sending commands. For this reason, the timing of the response from the receiving station is different for the station that transmitted the command, and it is necessary to judge the communication abnormality while considering it, so the processing of the abnormal system becomes complicated. In addition, since there are cases where information and commands from a plurality of stations are received at the same time, it is necessary to prepare reception buffers for the number of other stations.

Therefore, recently, the output signal from the carrier wave detecting means is monitored, and when the carrier wave no-reception state continues for a preset time, a signal indicating the carrier wave no-reception state is output until the carrier wave reception is present. A time delay unit is provided, the output signal from this delay unit is monitored by the transmission control unit, and when the carrier reception state is indicated, command transmission of the own station is prohibited, and 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 the configuration of the main part of such a conventional wireless data communication apparatus, which is 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 3 which can be read and written at any time) 3, a wireless circuit unit 4, and a non-reception time delay circuit 5.

The radio circuit section 4 creates a transmission message for command transmission and response transmission in response to a command from the CPU 1, and a transmission message given from this transmission section 4a is modulated at a predetermined frequency to aerial line 6. Output of the demodulator 4c and the demodulator 4c for wirelessly transmitting the radio signal, the demodulator 4c for demodulating the radio signal received by the antenna 6, the receiver 4d for instructing the CPU 1 to take in the received signal demodulated by the demodulator 4c, and the demodulator 4c. Carrier from signal to antenna 6
And a carrier sense section 4e which outputs the monitored content as a binary signal carrier status signal CS to the non-reception time delay circuit 5.

When the operation of the reception function unit is stopped while the local station is transmitting to save electric power, a changeover switch is provided between the modulator unit 4b and the demodulator unit 4c and the antenna 6. Normally, the antenna 6 and the demodulator 4c are connected to separate the modulator 4b from the antenna 6, and the modulator 4 is used for transmission.
b and the antenna 6 are connected to each other 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 carrier reception state, sets the carrier sense delay signal CST output to the CPU 1 to the carrier reception state. When the carrier sense signal CS is not received, the carrier sense delay signal CST is set to the state where no carrier is received when this state continues for a preset time.

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) and commands (commands) to other stations, the carrier sense delay signal CST from the non-reception time delay circuit 5 is checked and a signal indicating no carrier reception (for example, When the signal is a low level signal “0”), command transmission is performed, and when the signal is a signal indicating no carrier reception (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 the reception of the command, the response transmission is performed regardless of the state of the carrier sense delay signal CST.

In the conventional apparatus having such a configuration, the carrier reception delay signal CST is set to the carrier reception non-detection state after the delay time by the non-reception time delay circuit 5, that is, the carrier reception non-detection state of the carrier sense signal CS is detected. By setting the time until it is set to the processing time of the wireless data communication device from the command reception to the response transmission or a time longer than that, it is possible for other stations to receive information or commands until the station returns a response. Since command transmission is prohibited, response transmission is promptly performed in response to command transmission, and stable wireless communication is guaranteed.

[0013]

However, the conventional wireless data communication device having the non-reception time delay means also has the following problems to be solved. That is, since wireless communication does not have a physical line like wire communication, radio waves emitted from electronic devices other than wireless devices may be detected as carrier waves. 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, the radio wave emitted from a microwave oven or the like is included in the used band, and a carrier wave is received by this interference radio wave. May become.

In the conventional wireless data communication apparatus having the non-reception point delay means, even if the interference radio wave is received as a carrier wave, the delay time by the non-reception point delay means after the interference radio wave disappears. Since the transmission opportunity could not be obtained until after the elapse of, the transmission opportunity was reduced and the communication efficiency was lowered.

The present invention has been made under such circumstances, and an object thereof is to be able to promptly perform response transmission in response to command transmission, and to ensure stable wireless communication. An object of the present invention is to provide a wireless data communication device capable of suppressing loss of transmission opportunity due to interference radio waves to a minimum and improving communication efficiency in an environment where interference radio waves exist.

[0016]

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

Further, according to the present invention, transmission detecting means for outputting a signal indicating the transmission state of the own station is provided, and the reception time delay means monitors the output signal from the carrier wave detecting means and the output signal from the transmission detecting means. However, if 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 non-state or the own station transmission no state. Is.

[0018]

According to the present invention having such a structure, when the carrier wave detecting means detects the carrier wave reception state, the transmission of the own station is prohibited. Then, when the carrier wave reception present state continues for a preset first time, the output signal from the reception time delay means becomes a signal indicating the carrier wave reception present state. Then, the output signal from the non-reception time delay means also becomes a signal indicating the carrier reception state. After that, when the carrier wave detecting means detects the carrier wave non-receiving state, the output signal from the reception time delay means becomes a signal indicating the carrier wave non-receiving state. Then, when this carrier wave non-reception state continues for the preset second time, the output signal from the non-reception time delay means becomes a signal indicating the carrier wave non-reception state. At this time, the local station can transmit.

However, when the carrier wave reception state is detected by the carrier wave detection means but the carrier wave reception state is not maintained for the first time, the output signal from the non-reception time delay means is no carrier wave reception. It remains a signal indicating the state. Therefore, when the output signal of the carrier wave detecting means is in the state of no carrier wave reception, the own station can transmit. That is, the carrier detected by the carrier detecting unit is the first
In the case of an interfering radio wave shorter than the time of, the transmission of the own station becomes possible when it is no longer detected.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 device A, wireless device B, wireless device C, wireless device D, ...) 10 are capable of data communication with each other. A case will be described in which each wireless data communication device 10 is of a type in which the operation of the reception function unit is stopped when the wireless data communication device 10 is transmitting.

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

The radio circuit section 14 prepares a transmission message for command transmission and response transmission in response to a command from the CPU 11, and a transmission message given from this transmission section 14a is modulated at a predetermined frequency to obtain an antenna. 16, a demodulation unit 14b that wirelessly transmits, a demodulation unit 14c that demodulates a radio signal received by the antenna 16, and a demodulation unit 14
The reception state of the carrier wave by the antenna 16 is monitored from the output signals of the reception unit 14d and the demodulation unit 14c which take in the reception signal demodulated in c and instruct the CPU 11,
The monitoring contents are constituted by the CPU 11 and a carrier sense unit 14e as a carrier detecting means for outputting to the one input terminal of the two-input OR gate 17 as a carrier state signal CS of a binary signal.

Although not shown, a changeover switch is inserted between the modulator 14b and the demodulator 14c and the antenna 16, and this changeover switch is operated by the CPU 11.
Normally, the antenna 16 and the demodulation unit 14c are connected to each other and the modulation unit 1 is connected.
4b and the antenna 16 are separated from each other, and at the time of transmission, the modulator 1
4b and the antenna 16 to connect the antenna 16 and the demodulation unit 14
It is controlled so as to separate from c.

The transmitting unit 14a changes the transmission state of the own station to 2
The OR gate 1 as the text state signal Tx of the value signal
It outputs to the other input terminal of 7, and here, the transmission unit 1
Reference numeral 4a constitutes a transmission detecting means.

The output terminal of the OR gate 17 is connected to the 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 status signal CS from the carrier sense section 14e and the text status signal Tx from the transmission section 14a by the logical sum output of the OR gate 17, and detects the carrier reception status or the own station. A binary signal indicating a carrier reception state is output to the non-reception time delay circuit 19 until a carrier reception state or a local station transmission state is maintained when the transmission state continues for a preset first time. And the reception time delay circuit 1
Reference numeral 8 constitutes a reception time delay means.

The non-reception time delay circuit 19 monitors the output signal from the reception time delay circuit 18, and detects the carrier wave until the carrier wave is not received until the carrier wave is not received for a second preset time. The CPU receives the binary signal indicating the reception state as a carrier sense delay signal CST.
11 is output to the non-reception time delay circuit 1
Reference numeral 9 constitutes a non-reception time delay means.

In the present embodiment, for convenience 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 are high level signals "1" indicating that the carrier is being received. , A no-reception state is a binary signal indicated by a low-level signal “0”, and the signal output from the transmitter 14a indicates a transmission-presence state of its own station by a high-level signal “1” and no transmission. The state is a binary signal indicated by a low level signal "0".

Therefore, 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), commands (commands), etc. to another station, the carrier sense signal CS from the carrier sense unit 14e is checked as ST (step) 1. If the carrier sense signal CS indicates a low level signal "0", that is, no carrier is received, the non-reception time point delay circuit 1 is set as ST2.
Check the carrier sense delay signal CST from 9. If the carrier sense delay signal CST also indicates the low level signal "0", that is, no carrier wave is received, the transmitter 14a is controlled as ST3 to perform command transmission.

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

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

In the present embodiment thus constructed,
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, response transmission time is 1 ms, maximum time that carrier sense signal CS becomes high level signal “1” due to interference radio wave is 4 ms, at the time of reception The first time set in the delay circuit 18 is 5 ms, and the second delay time set in the non-reception time delay circuit 19 is 8 ms.

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

4A shows a transmission output signal, a carrier sense signal CS and a carrier sense delay signal CST in the radio A, and FIG. 4B shows a radio B.
2 is a transmission output signal, a carrier sense signal CS and a carrier sense delay signal CST in FIG. 3C, and FIG. 7C is a transmission output signal, a carrier sense signal CS and a carrier sense delay signal CST in the radio device C.

Further, the wireless data communication apparatus having the conventional non-reception time delay circuit 5 shown in FIG.
5 is a timing chart similar to that of FIG. 4 when C is used.
Shown in

That is, in the apparatus of this embodiment, the wireless device A
The carrier sense signal CS of the other wireless devices B and C becomes the high level signal "1" indicating the carrier reception state at the transmission output timing of. Here, the transmission output time is 10 ms, and the first time set in the reception time delay circuit 18 is 5 ms.
Therefore, the carrier sense delay signal CST of each of the radios A, B, and C will be transmitted 5 ms after the start of transmission output.
Becomes a high level signal “1” indicating the state of carrier reception.

After that, when the transmission output of the wireless device A is exhausted, the carrier sense signals CS of the other wireless devices B and C return to the low level signal "0" indicating the state of no carrier wave reception. However, the carrier sense delay signal C of each radio A, B, C
ST is a second delay set in the non-reception time delay circuit 19.
The high level signal "1" is maintained until the time of 8 ms has passed. As a result, the command transmission operation of each wireless device A, B, C is prohibited.

Then, when 7 ms has elapsed after 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, radio A and radio C
The carrier sense signal CS of becomes a high level signal "1" indicating the carrier detection state, but the response transmission time is 1 ms.
Is shorter than the first time 5 ms set in the reception time delay circuit 18, the signals output from the reception time delay circuit 18 of each of the wireless devices A, B, and C are low level indicating the carrier non-detection state. The signal "0" remains. 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 carrier non-reception state when 8 ms has elapsed after the radio output from the radio A was stopped. As a result, each of the wireless devices A, B and C can transmit a command.

Here, when 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, the carrier sense signals CS of the respective wireless devices A, B and C are in the carrier detected state. Becomes a high level signal "1" indicating that the wireless devices A, B and C are prohibited from transmitting commands. However, since the time when the carrier sense signal CS becomes the high level signal “1” due to the interference radio wave is 4 ms at the maximum, which is shorter than the first time 5 ms set in the reception time delay circuit 18, each radio A, B, C
Carrier sense delay signal CST does not become high level signal "1". Therefore, the carrier sense signal CS is a low level signal "0" indicating that there is no carrier wave reception.
Then, each of the wireless devices A, B, and C becomes ready to send a command.

At this time, if the wireless device C is in a state of transmitting information or a command to the wireless device B, the wireless device C starts command transmission. After that, radio A is radio B
It 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.
At the transmission output timing of the wireless device A, the carrier sense signal CS and the carrier sense delay signal CS of the other wireless devices B and C are transmitted.
T becomes a high level signal "1" indicating the state of carrier reception. After that, 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 state of no carrier reception. However, since the carrier sense delay signal CST of each of the radios B and C maintains the high level signal "1" until the time 8 ms set in the non-reception time delay circuit 5 has elapsed, the radios B, C
Command transmission operation of C is prohibited.

When 7 ms have passed after 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, radio A and radio C
Carrier sense signal CS becomes a high level signal "1" indicating a carrier wave 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 continues to be the high level signal “1”. And after receiving the response transmission,
The high level signal "1" is maintained until 8 ms has passed.

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 radio device in the system before the lapse of 8 seconds, the carrier of each radio device A, B, C is generated. The sense signal CS becomes the high level signal "1". Further, the carrier sense delay signal CST of the wireless device B becomes the high level signal "1", and the carrier sense delay signal CST of the other wireless devices A and C maintains the high level signal "1". Then, 8 ms 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. It becomes possible to send.

At this time, if the wireless device C is in a state of transmitting information or a command to the wireless device B, the wireless device C starts command transmission. After that, radio A is radio B
It operates in the same way as when a command is sent to.

Therefore, as is clear from comparison between FIG. 4 and FIG. 5, when an interfering radio wave is generated in the related art, command transmission can be performed only after the time set in the non-reception time delay circuit 5 has elapsed. However, in this embodiment, if the time when the carrier sense signal CS becomes the high level signal "1" is less than the first time set in the reception time delay circuit 18, the carrier wave due to this interference wave is detected. The command can be sent when it disappears.

As described above, in the wireless data communication apparatus 10 of this embodiment, the carrier sense unit 14e monitors the reception state of the carrier wave on the antenna 16. When the carrier reception state is detected, the carrier sense signal CS is detected. The low level signal "0" indicating no carrier wave reception state is changed to the high level signal "1" indicating carrier wave reception state to prohibit command transmission of the own station. Then, this carrier wave reception presence state is set in the reception time delay circuit 18 in advance as the first
When the time continues, the output signal from the reception time delay circuit 18 changes to the high level signal "1" indicating the state of carrier reception. Then, the non-reception time delay circuit 1
Carrier sense delay signal CST, which is an output signal from 9
Also changes to the high level signal "1" indicating the state of carrier reception.

After that, when the carrier sense section 14e detects the no carrier wave reception state, the output signal from the reception time delay circuit 18 changes to the low level signal "0" indicating the no carrier wave reception state. Then, when this carrier-reception-free state continues for the second time preset in the non-reception-time delay circuit 19, the carrier sense delay signal CST from this non-reception-time delay circuit 19 also has a low level indicating the carrier-reception-free state. The signal changes to "0". At this time, if the carrier sense signal CS from the carrier sense unit 14e is the low level signal "0", the own station can transmit.

However, when the carrier sense section 14e detects the carrier reception state, but the carrier reception state does not continue for the first time or longer, the output from the reception time delay circuit 18 does not receive the carrier. 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 state where no carrier wave is received. Therefore, when the carrier sense unit 14e detects a state in which no carrier wave is received, the own station can perform transmission.

Therefore, if the maximum time for 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, the interference radio wave is detected. When it is no longer possible, the local station can perform transmission, the loss of transmission opportunity due to the interference radio wave can be suppressed to the minimum, and the communication efficiency in the environment where the interference radio wave exists can be improved.

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

For example, the wireless communication system of the present embodiment is
Multiple wireless POSs that perform product sales data registration processing
(Point of sales: Point of sales information management) When applied to a wireless POS system in which a terminal and a host computer that centrally controls each POS terminal are connected by a wireless line, each POS terminal sends a command to the host computer. In order to register product sales data, an inquiry message for product information is frequently wirelessly transmitted, and prompt response is required for replying the product information to this inquiry. On the other hand, in a supermarket or the like in which this type of POS system is introduced, there are cases where a microwave oven is installed near the accounting location where each POS terminal is installed to warm the food purchased by the customer.

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. It is possible to promptly respond to the inquiry and speed up the merchandise sales data registration process at each POS terminal.

By the way, in the case of the wireless data communication device 10 of the type in which the operation of the reception function unit is stopped when the local station is transmitting as in the present embodiment, the carrier sense is performed while the local station is transmitting a command. The signal CS remains the low level signal "0". Therefore, if the transmission unit 14a does not have the transmission detection means, the carrier sense delay signal CST does not become the high level signal "1" indicating the state of carrier reception with respect to the transmission operation of the own station. As a result, the transmitting station can immediately transmit the next command after completing the command transmission, but other stations including the receiving station change the carrier sense delay signal CST to the high level signal “1” indicating the carrier reception state. As a result, there is no chance to send a command.

Therefore, in the present embodiment, the transmitting section 14a is provided with a function as a transmission detecting means for outputting the text state signal Tx which is a binary signal indicating the transmission state of its own station, and the text state signal Tx and carrier sense are provided. An OR output from 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
When the carrier reception present state or the own station transmission present state lasts for a preset first time, the binary signal indicating the carrier reception present state is not displayed until the carrier reception not present state or the own station transmission not present state. It is configured to output to the reception time delay circuit 19.

With such a configuration, in the transmitting station, the carrier sense delay signal CST becomes the high level signal "1" indicating the state of carrier reception in the same manner as the other stations in the transmitting operation of the own station. Can equalize the opportunity of sending commands.

In the case of the wireless data communication device 10 of the type in which the operation of the reception function unit is not stopped even when the local station is transmitting, as shown in FIG. The carrier sense signal CS from the carrier sense unit 14e can be directly input to the reception time delay circuit 18 by omitting the OR function and the OR gate 17.

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 the 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 the high level signal “1” with respect to the transmission output of the own station.
The timings at which the carrier sense signals CS of B and C and the carrier sense delay signal CST maintain the low level "0" at the same time coincide with each other. Therefore, also in the wireless data communication device 10 shown in FIG. 6, the same effect as that of the wireless data communication device 10 shown in FIG. 2 can be obtained.

In the above embodiment, the signals output from the carrier sense unit 14e, the reception time delay circuit 18 and the non-reception time delay circuit 19 indicate the presence of a carrier wave as a high level signal "1". The absence state is a binary signal indicated by a low level signal "0", and the signal output from the transmission unit 14a indicates a transmission presence state of the local station by a high level signal "1" and a transmission non-transmission state is a low level signal. Although the binary signal indicated by “0” is used, the reception state of the carrier wave is indicated by the low level signal “0”, and the non-reception state is changed by the high level signal “1” to the binary signal to indicate the transmission state of the own station. May be represented by a low level signal “0”, and the non-transmission state may be a binary signal represented by a high level signal “1”.

[0059]

As described above in detail, according to the present invention, it is possible to quickly send a response to a command transmission, ensure stable wireless communication, and minimize the loss of transmission opportunity due to an interference radio wave. It is possible to provide a wireless data communication device that can be suppressed to the maximum and that can improve communication efficiency in an environment in which interference radio waves exist.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a main part of the wireless data communication apparatus according to the embodiment.

FIG. 3 is a flowchart showing a transmission algorithm of the wireless data communication apparatus 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 block diagram of a main part of a wireless data communication device 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 apparatus in the other 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]

 DESCRIPTION OF SYMBOLS 10 ... Wireless data communication apparatus 11 ... CPU (transmission control means) 14 ... Wireless circuit section 14a ... Transmission section (transmission detection means) 14b ... Modulation section 14c ... Demodulation section 14d ... Reception section 14e ... Carrier sense section (carrier detection section) ) 16 ... Antenna 17 ... Ogate 18 ... Reception time delay circuit 19 ... Non-reception time delay circuit

Claims (2)

[Claims] 1. A carrier wave detecting means for outputting a signal indicating a receiving state of a carrier wave by an antenna, and an output signal from this detecting means is monitored, and when the carrier wave receiving existence state lasts for a preset first time, no carrier wave is received. Until the state is reached, the reception time delay means for outputting a signal indicating the presence of the carrier wave, and the output signal from the reception time delay means are monitored, and after the state of reception of the carrier wave, the state of no reception of carrier wave is preset. The non-reception time point delay means for outputting the signal indicating the carrier reception state until the time of 2 is maintained, the output signal from the non-reception time point delay means and the output signal from the carrier wave detection means are monitored, and at least one of them is monitored. A wireless data communication apparatus, comprising: a transmission control unit that prohibits transmission of the local station when a signal indicates a state of receiving a carrier wave. 2. A carrier wave detecting means for outputting a signal indicating a receiving status of a carrier wave by an antenna, a transmission detecting means for outputting a signal indicating a transmitting status of the own station, an output signal from the carrier wave detecting means and the transmission detecting operation. The output signal from the means is monitored, and if the carrier reception present state or the own station transmission present state lasts for a preset first time, the carrier reception present state is displayed until the carrier reception not present state or the own station transmission not present state. A reception point delay means for outputting a signal, and a second preset for a carrier wave no reception state after monitoring a signal output from the reception time point delay means and a carrier wave reception present state.
Of the non-reception time point delay means for outputting a signal indicating the carrier reception state until the time period of (1), and the output signal from the non-reception time point delay means and the carrier wave detection means are monitored, and at least one of the signals is monitored. A wireless data communication device, comprising: a transmission control unit that prohibits the transmission of the local station when the signal indicates the presence of carrier wave reception.