JP2011229050A - Communication device and method of communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid communication disruption resulting from misalignment of transmission and reception timing by correcting the misalignment of transmission and reception timing with a communication partner.SOLUTION: A slave unit 200 includes: a piezoelectric element section 226 for detecting or generating a ultrasound; a communication section 218 for performing communication using the ultrasound; a memory section 202 for storing a common table which is shared with a master unit 100 and in which a slot with a certain length of time are chronologically allocated; a slot timing control section 208 for performing synchronization with the master unit 100 and giving a transmission or reception instruction based on the slot; a distance acquisition section 212 for acquiring distance information in relation to a distance to the master unit 100; a time measurement section 214 for measuring time required for the communication section 218 to receive a signal transmitted from the master unit 100 based on the table; and a slot timing correction instruction section 210 for calculating a time lag in relation to the synchronization with the master unit 100 based on the required time and the distance information to give an instruction to correct misaligned time.

Description

  The present invention relates to a communication device and a communication method.

Divers who are diving need to communicate with other divers and mother ships in order to ensure their own safety. Since underwater radio waves are greatly attenuated, communication using ultrasonic waves is widely performed.
Thus, a communication device used underwater is desired to be reduced in size and power consumption. For example, as shown in Patent Document 1 below, synchronization is performed in a synchronization slot using one frequency, and transmission / reception timing is set. A technique for performing two-way bi-directional communication by combining the two is proposed.

JP 7-212268 A

  Such a communication device needs to measure time accurately in order to synchronize with a communication partner, and measures time using a crystal resonator. However, when the communication device is used underwater, the characteristics of the crystal unit change due to a decrease in the temperature of the usage environment, a timing error occurs, and there is a time lag in the transmission / reception timing with the communication partner. In some cases, communication could not be performed. An object of this invention is to correct | amend the time gap of the transmission / reception timing which arises between communication partners.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A communication apparatus according to this application example is a communication apparatus that communicates with other communication apparatuses using ultrasonic waves as a transmission medium in water, using the ultrasonic transducer that detects or generates the ultrasonic waves, and the ultrasonic waves. A communication unit that communicates, a table in which slots having a certain length of time are assigned in time series, a storage unit that stores the table common to the other communication device, and a synchronization with the other communication device A slot timing management unit that instructs the communication unit to switch transmission / reception based on the slot, a distance acquisition unit that acquires distance information about a distance from the other communication device, and the other according to the table A time measuring unit for measuring a time required for the communication unit to receive a signal transmitted from the communication device, and based on the time required and the distance information. A slot timing correction instruction unit that calculates a difference time of synchronization with the other communication device and instructs the slot timing management unit to correct synchronization according to the calculated difference time. The management unit corrects the synchronization with the other communication device according to the time difference based on an instruction from the slot timing correction instruction unit.

  According to such a configuration, communication instructions are assigned in time series, and based on a table common to other communication devices, in order to switch between a transmission state, a reception state, and a standby state in synchronization with other communication devices, A communication device can communicate bidirectionally with other communication devices using ultrasonic waves of one frequency. Further, the slot timing correction instruction unit calculates a difference time of synchronization with the other communication device based on a required time and distance information required to receive a signal transmitted from the other communication device according to the table, The slot timing management unit is instructed to correct synchronization with another communication device according to the calculated difference time. As a result, the slot timing management unit corrects synchronization with other communication devices according to the difference time. Therefore, even when a transmission / reception timing with another communication apparatus is misaligned, the misalignment is corrected, so that it is possible to prevent communication with another communication apparatus from being disabled due to a deviation in the transmission / reception timing.

[Application Example 2]
The communication apparatus according to the application example preferably includes a receiving unit that receives information and a power control unit that controls power supplied to the receiving unit based on an instruction from the slot timing management unit.

  According to such a configuration, since the power supplied to the receiving device is controlled based on the slot, the power consumption of the communication device can be reduced.

[Application Example 3]
In the communication device according to the application example, the distance acquisition unit may receive and acquire the distance information transmitted from the other communication device.

[Application Example 4]
In the communication device according to the application example, the distance acquisition unit calculates the distance information based on a time required for the communication unit to receive the signal transmitted by the other communication device according to the table. May be.

[Application Example 5]
The communication method according to this application example is based on a slot having a certain length of time allocated to a common table with the other communication device by synchronizing with other communication devices using ultrasonic waves as a transmission medium in water. A communication method for communicating using the ultrasonic wave, wherein a distance acquisition step for acquiring distance information related to a distance from the other communication device and a signal transmitted from the other communication device according to the table are received A time measuring step for measuring a required time required for the calculation, a calculating step for calculating a difference time of synchronization with the other communication device based on the required time and the distance information, and according to the calculated difference time And a correction step for correcting synchronization.

  According to such a method, communication instructions are assigned in time series, and based on a table common to other communication devices, in order to switch between a transmission state, a reception state, and a standby state in synchronization with other communication devices, Bidirectional communication with other communication devices is possible using ultrasonic waves of one frequency. Also, based on the time required to receive a signal transmitted from another communication device according to the table and the distance information, the difference time of synchronization with the other communication device is calculated, and the difference time calculated according to the calculated difference time To instruct synchronization correction with other communication devices. As a result, synchronization with other communication devices is corrected according to the difference time. Therefore, even when a transmission / reception timing with another communication apparatus is misaligned, the misalignment is corrected, so that it is possible to prevent communication with another communication apparatus from being disabled due to a deviation in the transmission / reception timing.

The figure explaining the underwater communication system to which the communication apparatus which concerns on this embodiment is applied. The figure explaining the functional structure of a main | base station and a subunit | mobile_unit. The figure explaining the structure of a slot. The figure explaining transmission / reception of the packet based on a slot. The figure explaining the hardware constitutions of a subunit | mobile_unit. The flowchart which shows the flow of the process which a subunit | mobile_unit corrects slot timing.

  Hereinafter, a communication device capable of transmitting and receiving underwater will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a diagram illustrating an application example of an underwater communication system 50 to which a communication device according to the present embodiment is applied. This underwater communication system 50 communicates between the parent device 100 provided in the mother ship 10 and the child device 200 attached to the arm of the diver 5 diving underwater by ultrasonic waves of a predetermined frequency.
The base unit 100 includes a piezoelectric element portion 120 that has been subjected to waterproofing treatment or waterproof pressure treatment. The piezoelectric element portion 120 is connected to the mother ship 10 via the communication line 102 and is supported from the mother ship 10 underwater. The communication signal generated by the base unit 100 is radiated into the water as ultrasonic waves from the piezoelectric element unit 120. Also, the ultrasonic wave transmitted from the underwater child device 200 is converted into a communication signal by the piezoelectric element unit 120 and received by the parent device 100.

Slave device 200 is a diver watch that has been subjected to waterproofing treatment or water pressure resistance treatment. The slave device 200 receives ultrasonic waves emitted from the piezoelectric element portion 120 of the parent device 100 and transmits ultrasonic waves to the parent device 100. Send.
The frequency of the ultrasonic wave is determined in consideration of the size of the parent device 100 and the child device 200, the power of the communication signal, the advantage in the circuit configuration, and the like, assuming a frequency between 10 KHz and 2 MHz. For example, 455 KHz may be employed as the frequency, and 2 kbps to 8 kbps may be employed as the bit rate. Moreover, the communication distance between the main | base station 100 and the subunit | mobile_unit 200 assumes about 40-50 m.

FIG. 2 is a diagram illustrating the functional configuration of the parent device 100 and the child device 200. Note that the number of slave units 200 with respect to one master unit 100 is not limited to one, but may be a plurality of units configured by substantially the same functional units.
In the present embodiment, the parent device 100 and the child device 200 communicate with each other through a communication procedure as shown in FIG. In this case, base unit 100 communicates according to one communication table (time slot) 300 and two slave units (200A, 200B) communicate according to the other time slot (310A, 310B) corresponding to one time slot 300. To do. These time slots (300, 310A, 310B) have a fixed time length (T0), and are communicated alternately for each slot instructing communication with the other, thereby enabling bidirectional communication with one frequency. Realize. The other time slot (310A, 310B) is uniquely determined by the master unit 100 determining one time slot 300. The other time slot (310 </ b> A, 310 </ b> B) may be stored in advance by handset 200 or transmitted from base unit 100.
One slot includes a transmission packet PKS from the parent device to the child device and a response packet PKR from the child device to the parent device. The data structure of the transmission packet PKS and the response packet PKR assumes, for example, a preamble area for indicating the head and synchronization, an ID information area, a transmission information area, a cyclic redundancy check (CRC) area for error check, and the like.

  As shown in the time slot (300, 310A, 310B), communication between the parent device 100 and the two child devices (200A, 200B) is first performed between the child device 1 (200A) in the first slot. Communication is performed, and then communication is performed with the slave unit 2 (200B) in the second slot to complete one cycle. In the time slot (300, 310A, 310B), six cycles are executed from the first slot to the sixth slot, and the base unit 100 and the two slave units (200A, 200B) The communication according to (300, 310A, 310B) is repeated. In addition, the subunit | mobile_unit 1 (200A) and the subunit | mobile_unit 2 (200B) change to a standby state, when self does not communicate with a main | base station.

Returning to FIG. 2, the functional configuration of base unit 100 will be described. Master device 100 includes operation unit 104, control unit 106, storage unit 108, distance calculation unit 109, communication unit 110, switching unit 116, piezoelectric element unit 120, and display unit 118.
The operation unit 104 sends an operation instruction corresponding to the operation to the control unit 106. In the present embodiment, the operation unit 104 is assumed to be a button (not shown) disposed on the parent device 100.

  The control unit 106 controls the operation of each functional unit of the parent device 100 based on the operation instruction sent from the operation unit 104. When the base unit 100 performs communication, the control unit 106 performs transmission / reception or non-communication instruction based on the slot assigned to the time slot 300 (FIG. 3). More specifically, the control unit 106 controls the communication unit 110 to transition to a transmission or reception communication state (communication mode) or a non-communication state (standby state) in which transmission and reception are not performed. Note that the time slots 310A and 310B (FIG. 3) of the slave unit 200 are uniquely determined according to the time slot 300 (FIG. 3) of the master unit 100, and the clock of the slave unit 200 serving as a reference for the operation is Synchronized with the clock when starting to use. In the present embodiment, the control unit 106 transmits information on the time slots 310A and 310B (FIG. 3) corresponding to the time slot 300 (FIG. 3) before exchanging information between the parent device 100 and the child device 200. Instructed to be transmitted to the slave unit 200 via the unit 112, the slave unit 200 receives the instruction and synchronizes with the clock of the master unit 100.

In the present embodiment, the information exchanged between the parent device 100 and the child device 200 may be a fixed sentence. This standard sentence assumes requirements and communication items for the communication partner. In this case, the amount of information exchanged in one communication is about 30 bytes.
The distance calculation unit 109 calculates the communication distance between the parent device 100 and the child device 200 based on the response time from the child device 200 to the communication signal transmitted from the parent device 100 to the child device 200. Information about the calculated distance is sent to the slave 200 at a predetermined timing. A technique for calculating the communication distance between the parent device 100 and the child device 200 from the time from when the communication signal is transmitted from the parent device 100 until the child device 200 responds and returns is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-265527. Has been.
The communication unit 110 includes a transmission unit 112 and a reception unit 114. The transmission part 112 produces | generates the communication signal of the fixed frequency modulated by the fixed sentence and request signal to transmit, and produces | generates a high frequency signal by amplifying the produced | generated communication signal to a predetermined output. The switching unit 116 electrically connects the transmission unit 112 and the piezoelectric element unit 120 during transmission, and electrically connects the reception unit 114 and the piezoelectric element unit 120 during reception. As a result, the generated high frequency signal is sent to the piezoelectric element unit 15.

Further, the receiving unit 114 acquires a communication signal from the high frequency signal sent from the piezoelectric element unit 120. The communication signal transmitted from the child device 200 includes a fixed sentence, and the fixed sentence is displayed on the display unit 118.
The piezoelectric element unit 120 is an ultrasonic transducer having a constant resonance frequency. In the present embodiment, an ultrasonic transducer (not shown) that transmits and receives ultrasonic waves by elastic vibration is employed as the piezoelectric element unit 120. As disclosed in Japanese Patent Application Laid-Open No. 8-275294, this ultrasonic transducer converts and outputs a high-frequency signal when ultrasonic vibration is detected, and responds to the high-frequency signal when a high-frequency signal is input. Generate and emit ultrasonic vibrations.
The storage unit 108 stores information about the time slot 300 (FIG. 3), communication conditions, communication procedures, attribute information of the communication partner and communication partner, fixed phrases, and the like.

Next, the functional configuration of the slave unit 200 will be described. The subunit | mobile_unit 200 is provided with the operation part 204, the control part 206, the memory | storage part 202, the communication part 218, the switching part 224, the piezoelectric element part 226, and the display part 216.
The operation unit 204 is operated by the diver 5 holding the child device 200, and an operation instruction corresponding to the operation is sent to the control unit 206. In the present embodiment, it is assumed that the operation unit 204 is a button (not shown) arranged on the child device 200.

The control unit 206 includes a slot timing management unit 208, a slot timing correction instruction unit 210, a distance acquisition unit 212, a time measurement unit 214, and a power supply control unit 215. The control unit 206 controls the operation of each functional unit of the child device 200 based on the operation instruction sent from the operation unit 204.
Here, details of each function of the control unit 206 will be described with reference to FIG. In this case, it is assumed that handset 200 is handset 2 (200B) in FIG.
The slot timing management unit 208 reads the time slot 310B stored in the storage unit 202, and manages timing for switching transmission / reception with the parent device 100 with reference to its own clock. More specifically, after the slave unit 1 (200A) and the slave unit 2 (200B) are synchronized with the master unit 100, the master unit 100, the slave unit 1 (200A), and the slave unit 2 (200B) The time slots (300, 310A, 310B) are in a synchronized state. Therefore, the slot timing management unit 208 can manage the transmission / reception timing in accordance with the timing of the parent device 100. When a correction instruction is received from the slot timing correction instruction unit 210, the slot timing is corrected by adjusting its own internal clock.

The power control unit 215 controls the power supply ON / OFF of the reception unit 220 based on the slot timing managed by the slot timing management unit 208. In the present embodiment, the slot timing management unit 208 instructs the power supply control unit 215 to turn on the power of the receiving unit 220 when the slot to be executed is to receive the slave unit 200, and the slot to be executed is the slave unit. When 200 is not received, the power control unit 215 is instructed to turn off the power of the receiving unit 220.
The distance acquisition unit 212 acquires information related to the distance from the parent device 100 from the parent device 100. The acquired distance information is referenced from the slot timing correction instruction unit 210 as necessary. In the present embodiment, the parent device 100 calculates the communication distance between the parent device 100 and the child device 200, but other methods may be used. For example, when synchronization is established with the parent device 100 and the slot timings coincide with each other, the communication distance is determined from the time received by the receiving unit 220, starting from the timing at which transmission is started in the time slot 300 of the parent device 100. It may be calculated.

Based on the timing of time slot 310B, time measurement unit 214 measures the time required for slave device 200 to receive the signal transmitted by master device 100. Information about the measured required time is sent to the slot timing correction instruction unit 210. In the present embodiment, the time measurement unit 214 measures time at a rate of about once per 100 packets, but is not limited to this.
The slot timing correction instruction unit 210 calculates a difference time (deviation time) from the slot timing of the parent device 100 based on the information related to the required time measured by the time measurement unit 214 and the distance information acquired by the distance acquisition unit 212. If the calculated deviation time exceeds a predetermined value, the slot timing management unit 208 is instructed to correct its own slot timing.

  Here, the correction of the slot timing will be described with reference to FIG. In FIG. 4, out of the two slave units (200A, 200B), the slave unit 1 (200A) is disregarded as an error with the slot timing between the master unit 100 and the slave unit 2 ( 200B) and the base unit 100 only. Further, the horizontal axis of FIG. 4 indicates the passage of time. Further, the power supply control unit 215 turns on / off the power of the reception unit 220 in accordance with the timing of the time slot 310B as shown in FIG. In the present embodiment, the power control unit 215 turns on the power of the reception unit 220 immediately before the reception unit 220 starts reception.

First, base unit 100 executes the Lth slot and transmits / receives a packet to / from slave unit 1 (200A), then, base unit 100 executes the (L + 1) th slot, and at time t5, “2 The transmission packet PKS of “2” is transmitted to the slave unit 2 (200B), and the response packet PKR of “2” from the slave unit 2 (200B) is received at time t8. In this case, since the two time slots (300, 310B) are in a synchronized state, there is no timing shift time. Accordingly, the slot timing correction instruction unit 210 does not instruct the slot timing management unit 208 to correct its own slot timing. The distance calculation unit 109 of the parent device 100 transmits the transmission packet PKS of “2” to the child device 2 (200B), and the time required for receiving the response packet PKR from the child device 2 (200B). And the communication distance to the child device 2 (200B) is calculated.
Next, the diver equipped with the slave unit 2 (200B) dives, and in the (M + 1) th slot, the master unit 100 transmits the transmission packet PKS of “2” to the slave unit 2 (200B) at time t13, After receiving at time t14, slave unit 2 (200B) transmits response packet PKR of “2” at time t15. As a result, base unit 100 receives response packet PKR of “2” at time t16. Here, a deviation occurs in the time slot 310B of the slave unit 2 (200B) due to a shape distortion of the piezoelectric element unit 120 due to a temperature difference between the ground and water, and a deviation time ΔT from the time slot 300 of the master unit 100 Occurs. Note that the transmission packet PKS “2” includes information on the communication distance calculated by the distance calculation unit 109. Accordingly, the distance acquisition unit 212 of the child device 2 (200B) can acquire the distance information with respect to the parent device 100 from the received transmission packet PKS of “2”.

  The slot timing correction instruction unit 210 excludes the delay time component caused by the distance from the parent device 100 from the time measured from the information related to the time measured by the time measurement unit 214 and the distance information acquired by the distance acquisition unit 212. Thus, a time difference (ΔT) indicating a delay or advance with respect to the time slot 310 </ b> B of the parent device 100 is calculated. Further, the slot timing correction instruction unit 210 instructs the slot timing management unit 208 to correct its own slot timing so that the calculated ΔT becomes zero. As a result, the two time slots (300, 310B) are in a synchronized state, and the timing shift time is greatly improved in the (N + 1) th slot at time t21.

Here, whether or not to improve the deviation time of ΔT is determined as follows. For example, if the time measured from the timing when slave unit 2 (200B) is turned on at its own slot timing is 7 milliseconds, and the communication distance with master unit 100 is 10 m, the sound wave travels underwater. At the transmission speed (about 1500 m / sec), 10 m is 6.7 milliseconds, so that the slot timing of slave unit 2 (200B) is determined to be substantially synchronized with the slot timing of master unit 100. At least, it is determined that the level is not out of sync.
If the time measured from the timing when slave unit 2 (200B) is turned on at its own slot timing is 14 milliseconds, and the communication distance with master unit 100 is 10 m, slave unit 2 (200B) It is presumed that the timing of turning on at the slot timing is earlier, and it is determined to delay the slot timing of the slave unit 2 (200B).

If the time measured from the timing when slave unit 2 (200B) is turned on at its own slot timing is 4 milliseconds, and the communication distance with master unit 100 is 10 m, slave unit 2 (200B) It is presumed that the ON timing is delayed at the slot timing, and it is determined to advance the slot timing of the slave unit 2 (200B).
In practice, when the communication distance between the parent device 100 and the child device 2 (200B) is grasped with a resolution of about 1 m, the slot timings of the parent device 100 and the child device 2 (200B) are synchronized with a time resolution of about 670 microseconds. be able to.

The communication unit 218 includes a transmission unit 222 and a reception unit 220. The transmission unit 222 generates a communication signal having a predetermined frequency modulated by a fixed sentence or request signal to be transmitted, and generates a high-frequency signal by amplifying the generated communication signal to a predetermined output. At the time of transmission, the switching unit 224 electrically connects the transmission unit 222 and the piezoelectric element unit 226. As a result, the generated high frequency signal is sent to the piezoelectric element unit 226.
At the time of reception, the switching unit 224 electrically connects the receiving unit 220 and the piezoelectric element unit 226. As a result, the receiving unit 220 acquires a communication signal from the high frequency signal sent from the piezoelectric element unit 226. The communication signal transmitted from the parent device 100 includes a fixed sentence, and the fixed sentence is displayed on the display unit 216.

The storage unit 202 stores information on the time slot 310B, communication conditions, communication procedures, attribute information of the communication partner and communication partner, fixed phrases, and the like.
The piezoelectric element unit 226 is an ultrasonic transducer having a constant resonance frequency. In the present embodiment, an ultrasonic transducer (not shown) that transmits and receives ultrasonic waves by elastic vibration is employed as the piezoelectric element unit 226, as in the base unit 100.
As shown in FIG. 5, the parent device 100 and the child device 200 include, as hardware, a control device 250 including a CPU 254, a memory 252, a crystal resonator 256, and various electronic circuits, and a display device 260 such as a liquid crystal panel. , An operation button 265, a communication device 270, a power supply device 275, and the like. Each functional unit described above is realized by the cooperation of these hardware and software stored in the memory 252.

FIG. 6 is a flowchart showing a flow of processing in which the slave unit 200 corrects the slot timing.
When this processing is started, first, the CPU 254 of the child device 200 acquires distance information from the parent device 100 (step S350) <distance acquisition step>. Subsequently, the CPU 254 calculates a time required for communication with the parent device 100 from the distance information (step S352).
Next, the CPU 254 determines whether or not it is time to start reception with reference to the time slot 310B (step S354). If it is determined that it is not time to start reception (No in step S354), the process returns to step S354. On the other hand, if it is determined that it is time to start reception (Yes in step S354), the CPU 254 issues an instruction to the power control unit 215 to turn on the power of the receiving unit 220 (step S356).

Next, CPU 254 starts time measurement (step S358), and determines whether or not a signal from parent device 100 has been received (step S360). If it is determined that the signal from the parent device 100 is not received (No in step S360), the process returns to step S360 and this process is repeated. On the other hand, when it is determined that the signal from base unit 100 has been received (Yes in step S360), CPU 254 ends the time measurement (step S362) <time measurement step>.
Next, the CPU 254 acquires information regarding the slot timing deviation from the measured time and the time required for communication (step S364) <calculation step>.

Subsequently, the CPU 254 determines whether or not the slot timing deviation exceeds an allowable range (step S366).
If it is determined that the slot timing deviation exceeds the allowable range (Yes in step S366), the CPU 254 corrects the slot timing (step S368) <correction step> and ends the series of processes. On the other hand, if it is determined that the slot timing deviation does not exceed the allowable range (No in step S366), the series of processing ends.

According to the embodiment described above, the following effects can be obtained.
(1) Since synchronization between the parent device 100 and the child device 200 can be ensured, it is possible to avoid a communication disabled state due to synchronization shift.
(2) Since the slave unit 200 can turn off the power of the receiving unit 220 until immediately before the communication signal from the master unit 100 is received, the power consumption of the slave unit 200 can be reduced.

Although the embodiment of the present invention has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention. For example, the time difference calculated by the slot timing correction instruction unit 210 may not be for all slots, and may be calculated at a predetermined rate. Moreover, when not calculating | requiring deviation | shift time, you may delay the timing which turns ON the receiving part 220 based on the communication distance with the main | base station 100 already acquired. Thereby, the power consumption required for reception can be further reduced.
Moreover, the apparatus which implements the above methods may be realized by a single apparatus or may be realized by combining a plurality of apparatuses, and includes various aspects.

  DESCRIPTION OF SYMBOLS 10 ... Mother ship, 50 ... Underwater communication system, 100 ... Main | base station, 102 ... Communication line, 104 ... Operation part, 106 ... Control part, 108 ... Memory | storage part, 109 ... Distance calculation part, 110 ... Communication part, 112 ... Transmission part , 114 ... receiving unit, 116 ... switching unit, 118 ... display unit, 120 ... piezoelectric element unit, 200 ... slave unit, 202 ... storage unit, 204 ... operation unit, 206 ... control unit, 208 ... slot timing management unit, 210 ... slot timing correction instruction unit, 212 ... distance acquisition unit, 214 ... time measurement unit, 215 ... power supply control unit, 216 ... display unit, 218 ... communication unit, 220 ... reception unit, 222 ... transmission unit, 224 ... switching unit, 226 ... piezoelectric element unit, 250 ... control device, 252 ... memory, 254 ... CPU, 256 ... crystal resonator, 260 ... display device, 265 ... operation button, 270 ... communication device, 2 5 ... power supply, 300,310A, 310B ... time slot.

Claims (5)

A communication device that communicates with other communication devices using ultrasonic waves as a transmission medium in water,
An ultrasonic transducer for detecting or generating the ultrasonic wave;
A communication unit that communicates using the ultrasonic wave;
A table in which slots having a certain time length are allocated in time series, and a storage unit that stores the table common to the other communication devices;
A slot timing management unit that synchronizes with the other communication device and instructs the communication unit to switch between transmission and reception based on the slot;
A distance acquisition unit that acquires distance information regarding a distance to the other communication device;
A time measuring unit for measuring a time required for the communication unit to receive a signal transmitted from the other communication device according to the table;
A slot timing correction instruction that calculates a difference time of synchronization with the other communication device based on the required time and the distance information, and instructs the slot timing management unit to correct synchronization according to the calculated difference time And comprising
The slot timing management unit corrects synchronization with the other communication device according to the difference time based on an instruction from the slot timing correction instruction unit. The communication device according to claim 1,
A receiving unit for receiving information;
And a power control unit configured to control power supplied to the receiving unit based on an instruction from the slot timing management unit. The communication device according to claim 1,
The distance acquisition unit receives and acquires the distance information transmitted from the other communication apparatus. The communication device according to claim 1,
The distance acquisition unit calculates the distance information based on a time required for the communication unit to receive the signal transmitted by the other communication device according to the table. Communication that uses ultrasonic waves as a transmission medium in water and synchronizes with other communication devices, and communicates using the ultrasonic waves based on slots having a certain length of time assigned to a common table with the other communication devices A method,
A distance acquisition step of acquiring distance information regarding the distance to the other communication device;
A time measuring step of measuring a time required to receive a signal transmitted from the other communication device according to the table;
A calculation step of calculating a difference time of synchronization with the other communication device based on the required time and the distance information;
And a correction step of correcting synchronization according to the calculated difference time.

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