JP2015126275A - Counter synchronization method for sensor terminal, synchronization device, and synchronization program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method having high accuracy and high versatility capable of synchronizing counters in sensor terminals configuring a radio sensor network.SOLUTION: A relay terminal's post-update counter value is calculated (S4) by using: a counter value in transmitting a radio signal (S2) after a coordinator resets a counter value (S1); a counter value in the relay terminal's reception (S3); and a counter value when update processing on the counter value starts. A relayed terminal's post-update counter value is calculated (S7) by using: a counter value in the relay terminal's transmission (S5); a counter value in the relayed terminal's reception (S6); and a counter value when update processing on the counter value starts. An offset value is calculated (S8) by using: the relay terminal's post-update counter value; a time stamp when the relay terminal's post-update counter value is input to an external apparatus; the relayed terminal's post-update counter value; and a time stamp when the relayed terminal's post-update counter value is input to the external apparatus.

Description

  The present invention relates to a counter synchronization method, a synchronization device, and a synchronization program for a sensor terminal. More specifically, the present invention relates to correction of a counter value when synchronizing counters of sensor terminals constituting a wireless sensor network.

  A wireless sensor network is a collection of sensor terminals that have a wireless communication function, so that a plurality of sensor terminals establish a wireless network by relaying communication between each other. It has a function of transmitting data, and is expected to be applied to medical treatment, welfare, crime prevention, disaster prevention, environmental measurement, and the like (Patent Document 1, Patent Document 2).

  Various application examples and application examples of the wireless sensor network can be considered. Depending on the use of the wireless sensor network, accurate synchronization of counters of a plurality of sensor terminals may be required.

  As a conventional technique for synchronizing the counters of the wireless terminal devices constituting the wireless network, there is a method using GPS (abbreviation for Global Positioning System).

Special table 2005-526416 JP 2008-78963 A

  However, in the method of synchronizing the counter of the wireless terminal device using GPS, the wireless terminal device is placed in a place where the GPS signal reception state is not good because the GPS receiving antenna is hidden behind the structure, such as indoors. In this case, there is a problem that the synchronization process cannot be performed. For this reason, it is difficult to say that the counter synchronization method using GPS is highly versatile.

  Therefore, the present invention provides a synchronization method, a synchronization device, and a synchronization program for a counter of a sensor terminal that can accurately synchronize the counters of the sensor terminals constituting the wireless sensor network by a highly versatile method. Objective.

  In order to achieve this object, the counter synchronization method of the sensor terminal of the present invention is based on the counter value c1 when the coordinator resets its counter value and transmits a radio signal, and the radio signal transmitted from the coordinator. Using the counter value c2 when the relayed first hop sensor terminal receives a radio signal and the counter value c3 when the first hop sensor terminal starts updating the counter value, the first hop sensor The updated counter value C1 = c3−c2 + c1 of the terminal is calculated, and the counter value c4 when the sensor terminal of the first hop transmits the wireless signal after calculating the updated counter value C1 and the first hop The counter value c5 when the second hop sensor terminal receiving the radio signal transmitted from the sensor terminal receives the radio signal, and the second hop sensor terminal The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6 when the update process is started, and the updated counter value C1 of the first hop sensor terminal is calculated. The time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the value C2 is input to the external device (where Ct is the reciprocal of the counter speed [count / Time)), the counter value C2 ′ = C2 + Vo is calculated, and the counter value C2 ′ is used as the synchronized counter value of the second hop sensor terminal.

  In the sensor terminal counter synchronization method of the present invention, the first hop relays the counter value c1 when the coordinator resets its counter value and transmits a radio signal and the radio signal transmitted from the coordinator. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal received the radio signal, and the second hop sensor terminal started updating the counter value The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the time counter value c6, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor are calculated. The time stamp t1 when the updated counter value C1 of the terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input to (where Ct is the reciprocal of the counter speed [count / time]), The third hop sensor terminal that receives the radio signal transmitted from the second hop sensor terminal and the counter value c7 when the second hop sensor terminal transmits the radio signal after calculating the updated counter value C2. Is wireless Counter value c8 when the third hop sensor terminal starts update processing of the counter value C3 = c9− c8 + c7 is calculated, and the counter value C3 ′ = C3 + Vo is calculated, and the counter value C3 ′ is used as the synchronized counter value of the third hop sensor terminal.

The counter synchronization method of the sensor terminal according to the present invention may further include a counter value c1 when the coordinator resets its counter value and transmits a radio signal, and one hop that relays the radio signal transmitted from the coordinator. After updating the first hop sensor terminal using the counter value c2 when the eye sensor terminal receives the radio signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value Counter value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and the second hop sensor terminal starts updating the counter value The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6 of the first hop, and the updated counter value C1 of the first hop sensor terminal is further calculated. The time stamp t1 when the updated counter value C1 of the sensor terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are external. Using the time stamp t2 when input to the device, the offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated (where Ct is the reciprocal of the counter speed [count / time]) , [K−1] hop sensor terminal calculates the updated counter value C _k−1 and then transmits a radio signal, and then the counter value c _{3 (k−1) +1} and [k−1] K-hop relays the radio signal transmitted from the hop sensor terminal. Using the counter value c _3k-1 when the eye sensor terminal receives a radio signal, a counter value c _3k when k th hop of the sensor terminal starts updating the counter value, k th hop of the sensor The process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} of the terminal is repeated from k = 3 to k = n (where n is an integer of 3 or more). Then, the counter value Cn ′ = Cn + Vo is calculated, and the counter value Cn ′ is used as the synchronized counter value of the n-hop sensor terminal.

  Alternatively, the counter synchronization method of the sensor terminal according to the present invention is based on the counter value c1 when the coordinator resets its counter value and transmits the radio signal, and the first hop for relaying the radio signal transmitted from the coordinator. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal receiving the received radio signal received the radio signal and the second hop sensor terminal started updating the counter value The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the time counter value c6, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor are calculated. The time stamp t1 when the updated counter value C1 of the terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when it is input to (where Ct is the reciprocal of the counter speed [count / time]) For each actual transmission of a wireless signal, the first hop sensor terminal transmits a wireless signal after the coordinator resets its counter value, and the first hop sensor terminal transmits a wireless signal. Receive Counter value c_2 when the first hop and the sensor value c_3 when the first hop sensor terminal starts updating the counter value are used to calculate the updated counter value C_1 = c_3−c_2 + c_1, and the second hop When the sensor terminal of the first sensor terminal determines that the wireless signal received by itself has arrived by retransmission, the counter when the sensor terminal of the first hop transmits the wireless signal after calculating the updated counter value C_1 Using the value c_4, the counter value c_5 when the second hop sensor terminal receives the radio signal, and the counter value c_6 when the second hop sensor terminal starts the update process of the counter value, the updated counter The value C_2 = c_6−c_5 + c_4 is calculated, and the synchronized counter value C_2 ′ = C_2 + Vo is output.

  In the sensor terminal counter synchronization method of the present invention, the first hop relays the counter value c1 when the coordinator resets its counter value and transmits a radio signal and the radio signal transmitted from the coordinator. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal received the radio signal, and the second hop sensor terminal started updating the counter value The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the time counter value c6, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor are calculated. The time stamp t1 when the updated counter value C1 of the terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when it is input to (where Ct is the reciprocal of the counter speed [count / time]) For each actual transmission of a wireless signal, the first hop sensor terminal transmits a wireless signal after the coordinator resets its counter value, and the first hop sensor terminal transmits a wireless signal. Receive Counter value c_2 obtained when the first hop sensor terminal starts updating the counter value, and the updated counter value C_1 = c_3−c_2 + c_1 is calculated. Counter value c_4 when the sensor terminal of the first hop has transmitted the wireless signal after the sensor terminal of the first hop has calculated the updated counter value C_1, and the counter value when the sensor terminal of the second hop received the wireless signal The updated counter value C_2 = c_6−c_5 + c_4 is calculated using c_5 and the counter value c_6 when the second hop sensor terminal starts the update process of the counter value, and the third hop sensor terminal When it is determined that the wireless signal received by itself has arrived by retransmission, the counter value c_7 when the second hop sensor terminal calculates the updated counter value C_2 and then transmits the wireless signal. Using the counter value c_8 when the third hop sensor terminal receives the radio signal and the counter value c_9 when the third hop sensor terminal starts the counter value update process, the updated counter value C_3 = c_9−c_8 + c_7 is calculated, and a synchronized counter value C_3 ′ = C_3 + Vo is output.

The counter synchronization method of the sensor terminal according to the present invention may further include a counter value c1 when the coordinator resets its counter value and transmits a radio signal, and one hop that relays the radio signal transmitted from the coordinator. After updating the first hop sensor terminal using the counter value c2 when the eye sensor terminal receives the radio signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value Counter value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and the second hop sensor terminal starts updating the counter value The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6 of the first hop, and the updated counter value C1 of the first hop sensor terminal is further calculated. The time stamp t1 when the updated counter value C1 of the sensor terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are external. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when it is input to the device (where Ct is the reciprocal of the counter speed [count / time]) ) For each actual transmission of the wireless signal, the sensor terminal of the first hop transmits the wireless signal after the coordinator resets its counter value, and the counter value c_1 when the sensor terminal of the first hop transmits wirelessly. Signal The updated counter value C_1 = c_3−c_2 + c_1 is calculated using the counter value c_2 at the time of transmission and the counter value c_3 when the sensor terminal of the first hop starts updating the counter value, and [k -1] Each sensor terminal as the k-th hop that relays the radio signal transmitted from the hop-th sensor terminal calculates the updated counter value C_k _-1 by the [k-1] -th hop sensor terminal. from the counter value c_ ₃ when transmitting the wireless signal _{(k-1) +1,} and the counter value c_ _3k-1 when k th hop of the sensor terminal receives a radio signal, the k-th hop of the sensor terminal using the counter value c_ _3k when starting the updating process of the counter value, the updated counter value _{C_ k = c_ 3k -c_ 3k-} 1 + c_ 3 (k-1) calculated ₊₁ (where, 2 ≦ k ≦ n−1, n is an integer of 3 or more), and the radio signal received by the nth hop sensor terminal is received by itself. When it is determined that are those that arrived by retransmissions, [n-1] th hop of the sensor terminal counter value when after calculating the updated counter value C_ _n-1 has transmitted the radio signal c_ _{3 ( n-1) +1} , a counter value c_3n _-1 when the n-hop sensor terminal receives a radio signal, and a counter value c_ when the n-hop sensor terminal starts a counter value update process using the _3n, while calculating the updated counter value _{C_n = c_ 3n -c_ 3n-1} + c_ 3 (n-1) +1, and to output a synchronized counter value C_n '= C_n + Vo.

  The counter synchronization apparatus of the sensor terminal according to the present invention relays the counter value c1 when the coordinator resets its counter value and transmits a radio signal and the radio signal transmitted from the coordinator at the first hop. The counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value are used, and C1 = c3 by the first hop sensor terminal. -The updated counter value C1 calculated by -c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1, and the wireless signal is transmitted, and the first hop sensor terminal The counter value c5 when the second hop sensor terminal receiving the transmitted radio signal receives the radio signal and the second hop sensor terminal updating the counter value Using the counter value c6 at the start of processing, means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and updating the first hop sensor terminal The post-counter value C1, the updated counter value C1 of the first hop sensor terminal when it is input to the external device, the post-update counter value C2 of the second hop sensor terminal, and the second hop The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the sensor terminal is input to the external device (where Ct: counter Speed reciprocal [count / time]) and means for calculating the synchronized counter value C2 '= C2 + Vo of the second hop sensor terminal.

  The counter synchronizer of the sensor terminal of the present invention, or the first hop relaying the radio signal transmitted from the coordinator and the counter value c1 when the coordinator resets its own counter value and transmits the radio signal The counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value are used, and C1 = c3 by the first hop sensor terminal. -The updated counter value C1 calculated by -c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1, and the wireless signal is transmitted, and the first hop sensor terminal The counter value c5 when the second hop sensor terminal that relays the transmitted radio signal receives the radio signal, and the second hop sensor terminal Using the counter value c6 at the start of the new process, means for receiving the updated counter value C2 calculated by C2 = c6-c5 + c4 by the second hop sensor terminal, and the first hop sensor terminal The updated counter value C 1, the time stamp t 1 when the updated counter value C 1 of the first hop sensor terminal is input to the external device, the updated counter value C 2 of the second hop sensor terminal, and the second hop The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the sensor terminal is input to the external device (where Ct: Counter value c7 when the second hop sensor terminal calculates the updated counter value C2 and then transmits a radio signal after the second hop sensor terminal calculates the updated counter value C2, and the second hop sensor terminal From the counter value c8 when the third hop sensor terminal receiving the transmitted radio signal receives the radio signal and the counter value c9 when the third hop sensor terminal starts the updating process of the counter value, Using the updated counter value C3 of the third hop sensor terminal calculated by C3 = c9−c8 + c7, means for calculating the synchronized counter value C3 ′ = C3 + Vo of the third hop sensor terminal is provided. .

The counter synchronizer of the sensor terminal according to the present invention may further include a counter value c1 when the coordinator resets its counter value and transmits a radio signal, and one hop that relays the radio signal transmitted from the coordinator. Using the counter value c2 when the first sensor terminal receives the radio signal and the counter value c3 when the first hop sensor terminal starts updating the counter value, C1 = The updated counter value C1 calculated by c3−c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the first hop sensor terminal Counter value c5 when the second hop sensor terminal that relays the radio signal transmitted from the terminal receives the radio signal, and the second hop sensor terminal counter Means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal using the counter value c6 at the start of the update process of the first hop, and the first hop sensor terminal Counter value C1 after update, time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to the external device, updated counter value C2 of the second hop sensor terminal, and 2 hops The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the eye sensor terminal is input to the external device (provided that Ct : Counter value of counter speed [count / time]) and counter value c ₃ when [k−1] hop sensor terminal calculates the updated counter value C _k−1 and then transmits a radio signal _{(k-1) +1} and [k-1] The counter value c _3k-1 when the k-th hop sensor terminal that relays the radio signal transmitted from the first hop sensor terminal receives the radio signal, and the k-th hop sensor terminal updates the counter value. The process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} of the _k-th hop sensor terminal using the counter value c _3k at the time of starting is k = 3. Use Cn repeatedly calculated from 3 to k = n (where n is an integer of 3 or more), and have means for calculating the synchronized counter value Cn ′ = Cn + Vo of the n-hop sensor terminal. ing.

  The counter synchronization program of the sensor terminal according to the present invention also includes a counter value c1 when the coordinator resets its counter value and transmits a radio signal, and a first hop that relays the radio signal transmitted from the coordinator. The counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value are used, and C1 = c3 by the first hop sensor terminal. -The updated counter value C1 calculated by -c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1, and the wireless signal is transmitted, and the first hop sensor terminal The counter value c5 when the second hop sensor terminal receiving the transmitted radio signal receives the radio signal and the second hop sensor terminal counter Using the counter value c6 when the update process is started, and receiving the updated counter value C2 calculated by C2 = c6-c5 + c4 by the second hop sensor terminal, and the first hop sensor terminal Counter value C1 after update, time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to the external device, updated counter value C2 of the second hop sensor terminal, and 2 hops The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the eye sensor terminal is input to the external device (provided that Ct : Reciprocal of counter speed [count / time]), and processing for calculating the synchronized counter value C2 '= C2 + Vo of the second hop sensor terminal.

  The synchronization program for the counter of the sensor terminal of the present invention, or the first hop that relays the counter value c1 when the coordinator resets its counter value and transmits the radio signal and the radio signal transmitted from the coordinator The counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value are used, and C1 = c3 by the first hop sensor terminal. -The updated counter value C1 calculated by -c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1, and the wireless signal is transmitted, and the first hop sensor terminal The counter value c5 when the second hop sensor terminal that relays the transmitted radio signal receives the radio signal and the second hop sensor terminal count A process of receiving an input of the updated counter value C2 calculated by C2 = c6−c5 + c4 by the sensor terminal of the second hop using the counter value c6 when the value update process is started, and the sensor of the first hop The updated counter value C1 of the terminal, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, 2 The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the sensor terminal of the hop is input to the external device (however, Ct: reciprocal of counter speed [count / time]), and counter value c7 when the second hop sensor terminal calculates the updated counter value C2 and transmits a radio signal, and the second hop sensor end A counter value c8 when the third hop sensor terminal receiving the radio signal transmitted from the end receives the radio signal, and a counter value c9 when the third hop sensor terminal starts updating the counter value; Then, using the updated counter value C3 of the third hop sensor terminal calculated by C3 = c9−c8 + c7, the computer performs a process of calculating the synchronized counter value C3 ′ = C3 + Vo of the third hop sensor terminal. I try to make it.

The counter synchronization program of the sensor terminal according to the present invention may further include a counter value c1 when the coordinator resets its counter value and transmits a radio signal, and one hop that relays the radio signal transmitted from the coordinator. Using the counter value c2 when the first sensor terminal receives the radio signal and the counter value c3 when the first hop sensor terminal starts updating the counter value, C1 = The updated counter value C1 calculated by c3−c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the first hop sensor terminal The counter value c5 when the second hop sensor terminal that relays the radio signal transmitted from the receiver receives the radio signal and the second hop sensor terminal Using the counter value c6 at the start of the update process of the counter value, the process of receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and the first hop The updated counter value C1 of the sensor terminal, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to the external device, the updated counter value C2 of the second hop sensor terminal, The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device (however, , Ct: reciprocal of counter speed [count / time]), and counter value when wireless signal is transmitted after sensor terminal of [k-1] hop calculates updated counter value _Ck-1 and _{c 3 (k-1) +1} , [k 1] and the counter value c _3k-1 when k th hop of the sensor terminal for relaying a radio signal transmitted from hops th sensor terminal receives a radio signal, k th hop of the sensor terminal updating the counter value The process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} of the _k-th hop sensor terminal using the counter value c _3k at the start of = 3 to k = n (where n is an integer greater than or equal to 3), Cn is used to calculate the synchronized counter value Cn ′ = Cn + Vo of the nth hop sensor terminal. I try to do it.

  Therefore, according to the synchronization method, the synchronization device, and the synchronization program of the counters of these sensor terminals, “t2−t1” of the offset value Vo is the relayed terminal (2 hops) after the relay terminal (first hop terminal) completes synchronization. The offset time Vo is a counter error at the time of hopping because “C2−C1” is a difference between counter estimation values using the internal processing time as a correction value. Therefore, the offset value Vo is calculated for the sensor terminals constituting the wireless sensor network, and the counter values C2 ′ (= C2 + Vo), C3 ′ (= C3 + Vo), and Cn ′ (= Cn + Vo) are used as synchronized counter values. Thus, the counter error at the time of hop is corrected, and a counter value with high synchronization accuracy is determined.

  According to the synchronization method, the synchronization device, and the synchronization program of the counters of these sensor terminals, the counter error at the time of hop is corrected without using a special device that may be restricted in use such as GPS. The counter value thus determined is determined.

  The counter synchronizer of the sensor terminal according to the present invention provides a time stamp t1 when the updated counter value C1 is input and a time stamp t2 when the updated counter value C2 is input. The updated counter value C1 may be input from the first hop sensor terminal and the updated counter value C2 may be input from the second hop sensor terminal. Also, the counter terminal counter synchronization program of the present invention provides a time stamp t1 when the updated counter value C1 is input and a time stamp t2 when the updated counter value C2 is input. The computer is caused to function as an external device to which the updated counter value C1 is input from the first hop sensor terminal and the updated counter value C2 is input from the second hop sensor terminal. You may do it. In these cases, since the device or computer that calculates the synchronized counter value of the sensor terminal also functions as an external device, an external device that is different from the device or computer that calculates the synchronized counter value of the sensor terminal is used. It becomes a simple structure which does not have.

  According to the sensor terminal counter synchronization method, synchronization device, and synchronization program of the present invention, the estimated counter value using the elapsed time and the internal processing time from the relay terminal being synchronized to the relayed terminal being completed as the correction value Since the offset value Vo, which is a counter error at the time of hop, is calculated in consideration of the difference between the two, the offset value Vo is calculated for the sensor terminals constituting the wireless sensor network, and the counter value C ′ (= C + Vo) is calculated. Can be used as a synchronized counter value to determine a counter value in which the counter error at the time of hop is corrected, and it is possible to improve the synchronization accuracy of the counter values of the sensor terminals constituting the wireless sensor network. .

  According to the synchronization method, the synchronization device, and the synchronization program of the counter of the sensor terminal of the present invention, the counter error at the time of hop without using a special device that may be restricted in use such as GPS, for example. Therefore, it is possible to improve the versatility as a method of synchronizing counter values of sensor terminals constituting a wireless sensor network.

  In addition, the counter synchronization apparatus and the synchronization program of the sensor terminal according to the present invention further includes means for giving a time stamp when the updated counter value is input, and the external counter value is input from the sensor terminal. A computer that can also function as a device or an external device that receives an updated counter value from a sensor terminal by further causing the computer to perform a process of giving a time stamp when the updated counter value is input In this case, since it is possible to provide a simple configuration that does not have an external device separate from the device or computer that calculates the synchronized counter value of the sensor terminal, It is possible to further improve the versatility as a method of synchronizing counter values of sensor terminals constituting a sensor network That.

It is a flowchart explaining an example of embodiment of the synchronization method of the counter of the sensor terminal of this invention. It is a functional block diagram of the counter synchronization device of the sensor terminal realized by the program when the counter synchronization method of the sensor terminal of the embodiment is implemented using the counter synchronization program of the sensor terminal. It is a figure which shows an example of the wireless sensor network corresponding to an example of embodiment. It is a figure which shows the apparatus structure in the case of implementing the counter synchronization method of the sensor terminal of an example of embodiment. It is a figure explaining the flow of calculation of the correction value by the synchronization method of the counter of the sensor terminal of an example of an embodiment. It is a flowchart explaining an example of other embodiment of the synchronization method of the counter of the sensor terminal of this invention. It is a figure which shows an example of the wireless sensor network corresponding to an example of other embodiment. It is a figure which shows the apparatus structure in the case of implementing the counter synchronization method of the sensor terminal of an example of other embodiment. It is a figure explaining the flow of calculation of the correction value by the synchronizing method of the counter of the sensor terminal of an example of other embodiments.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 to FIG. 9 show examples of embodiments of the counter synchronization method, synchronization device, and synchronization program of the sensor terminal of the present invention.

  Note that a wireless sensor network transmits sensor data collected by each sensor terminal by transmitting a plurality of sensor terminals having a wireless communication function and relaying communication between the sensor terminals. It is a network configured. The sensor terminals can transmit radio signals and autonomously transmit data between the sensor terminals by multi-hop communication. Multi-hop communication refers to communication that connects to each other without intervention of an access point.

  Specifically, for example, it is conceivable to construct a wireless sensor network using ZigBee, which is one of the short-range wireless communication standards whose main purpose is a sensor network. The ZigBee terminals have a relay function, and information can be transmitted as long as ZigBee terminals can communicate with each other by repeating the relay. Also, the specification of the basic part of ZigBee is standardized as IEEE 802.15.4.

  In order to construct a wireless sensor network using sensor terminals, a plurality of sensor terminals are installed at appropriate intervals within the reach of the radio waves transmitted from the sensor terminals with respect to the equipment, structures and areas to be monitored. The In addition, a coordinator is provided that transmits a radio signal to the sensor terminal, receives a radio signal from the sensor terminal, converts the radio signal into digital information, and outputs the digital information to an external device.

  Here, in the wireless sensor network, the wireless signal wirelessly transmitted from the coordinator is relayed to other sensor terminals, or the wireless signal transmitted from the other sensor terminals is relayed to the coordinator and further other sensor terminals. A sensor terminal that receives a radio signal relayed by the relay terminal is called a relayed terminal.

  As an example of a wireless sensor network constructed by installing a plurality of sensor terminals, an example in which two sensor terminals 2A, 2B are installed is shown in FIG. 3, and three sensor terminals 2A, 2B, 2C are installed. Examples of these are shown in FIG. In the example shown in FIG. 3, the sensor terminal 2A is a relayed terminal, and the sensor terminal 2B is a relay terminal. In the example shown in FIG. 7, the sensor terminal 2A is a relayed terminal, and the sensor terminals 2B and 2C are relay terminals. In the following, when it is not necessary to distinguish each sensor terminal, or when referring to all sensor terminals, they are referred to as “sensor terminal 2”.

  The sensor terminal 2 includes a control unit, a clock unit, and a transmission / reception unit. The sensor terminal 2 also exhibits a sensor function according to the purpose of the sensor terminal, performs measurement, and outputs measurement data acquired by measurement to the control unit, or a sensor terminal such as a dry cell or a solar cell 2 is a part that accepts the supply of power from a power source that enables self-sustained driving or an external power source, and appropriately includes a power source unit that supplies power to each part in the terminal.

  The control unit controls the operation of the sensor terminal 2, and is configured by, for example, an integrated circuit.

  The clock unit measures (measures in other words, accumulates) time by changing at a predetermined interval such as 1 millisecond or 100 microseconds (in other words, counter speed or time increment). Then, this measurement time is extracted as a counter value from the clock unit and used for processing inside the terminal or output to an external device (in other words, it can be acquired by the external device).

  The transmission / reception unit is a circuit that transmits / receives a radio signal via an antenna. Specifically, for example, measurement data acquired by the sensor unit is input via the control unit by the transmission / reception unit, and the measurement data (digital information) is converted into a radio signal and wirelessly transmitted to the outside via the antenna. In addition, a radio signal received by the antenna is input, the radio signal is converted into digital information, and output as reception data to the control unit.

  If each sensor terminal 2 in the example of the wireless sensor network shown in FIGS. 3 and 7 is associated with the ZigBee configuration, the sensor terminal 2A that is a relayed terminal is a ZigBee Router or a data that is a terminal that includes a data relay function. It corresponds to ZigBee End Device which is a terminal having no relay function, and the sensor terminals 2B and 2C which are relay terminals correspond to ZigBee Router which is a terminal including a data relay function.

  In addition, the sensor terminal 2A corresponds to RFD (abbreviation of reduced-function device) or FFD (abbreviation of full-function device) in IEEE802.15.4 which is a protocol for WPAN (abbreviation of wireless personal area network). Therefore, ZigBee Router, ZigBee End Device, RFD or FFD is an example of the configuration of the sensor terminal 2A.

  Then, ZigBee Router is an example of the configuration of the sensor terminals 2B and 2C.

  In addition, a coordinator 1 is provided that transmits a radio signal to the sensor terminal 2 or receives a radio signal from the sensor terminal 2 and converts the radio signal into digital information and outputs the digital information to the external device 9. The coordinator 1 is capable of transmitting and receiving (that is, inputting and outputting) signals such as data and control commands to a processing device (specifically, for example, a computer) having a data signal input / output function and an arithmetic function. For example, it is electrically connected by a cable having a USB terminal or the like. In this embodiment, the external device 9 to which the coordinator 1 is connected is a processing device to which the coordinator 1 is connected, and digital information is output from the coordinator 1 to the external device 9 to which the coordinator 1 is connected.

  The coordinator 1 corresponds to a ZigBee Coordinator when associated with the ZigBee configuration, and is a terminal that exists in the network and controls the network. The coordinator 1 corresponds to an FFD as a PAN coordinator in IEEE 802.15.4 which is a protocol for WPAN. Therefore, the coordinator 1 is an example of the configuration of an FFD as a ZigBee Coordinator or a PAN coordinator. Specifically, at least an antenna for transmitting and receiving a radio signal and a radio signal received by the antenna are input. And a transmission / reception circuit that converts the radio signal into digital information and outputs it as received data, and converts data (digital information) input from the outside into a radio signal and outputs the radio signal to the antenna.

  Here, the counter synchronization method of the sensor terminal of the present embodiment can be realized as a counter synchronization device of the sensor terminal. The counter synchronization device 10 of the sensor terminal according to the present embodiment includes a data input receiving unit 11a as means for receiving an input of an updated counter value calculated by the sensor terminal 2, and a time when the updated counter value is input. Using a time stamp giving unit 11b as means for giving a stamp, an offset value calculating unit 11c as means for calculating an offset value using the updated counter value and the time stamp, an updated counter value, and an offset value And a synchronous counter value calculation unit 11d as means for calculating the counter value synchronized with each other.

  The sensor terminal counter synchronization method and sensor terminal counter synchronization apparatus can also be realized by executing a sensor terminal counter synchronization program on a computer. Here, a case will be described in which a counter synchronization apparatus for a sensor terminal is realized and a counter synchronization method for a sensor terminal is executed by executing a synchronization program for the counter of the sensor terminal on a computer.

  FIG. 2 shows an overall configuration of a computer 10 (which is also a sensor terminal counter synchronization device 10 in this embodiment) for executing the sensor terminal counter synchronization program 17. This computer 10 (sensor terminal counter synchronization device 10) includes a control unit 11, a storage unit 12, an input unit 13, a display unit 14, and a memory 15, and is connected to each other by a signal line such as a bus.

  The control unit 11 performs control related to the overall control of the computer 10 and the synchronization of the counter of the sensor terminal by the sensor terminal counter synchronization program 17 stored in the storage unit 12, for example, a CPU (Central Processing Unit). ).

  The storage unit 12 is a device that can store at least data and programs, and is, for example, a hard disk.

  The memory 15 serves as a memory space that is a work area when the control unit 11 executes various controls and operations, and is, for example, a RAM (abbreviation of Random Access Memory).

  The input unit 13 is an interface for giving at least an operator's command to the control unit 11, and is, for example, a keyboard.

  The display unit 14 performs drawing / display of characters, graphics, and the like under the control of the control unit 11 and is, for example, a display.

  Then, the control unit 11 of the computer 10 (which is also the sensor terminal counter synchronization apparatus 10 in this embodiment) updates the sensor terminal 2 by executing the sensor terminal counter synchronization program 17. A data input receiving unit 11a that performs a process of receiving an input of a post-counter value, a time stamp adding unit 11b that performs a process of applying a time stamp when the post-update counter value is input, an updated counter value and a time stamp; An offset value calculation unit 11c that performs a process of calculating an offset value using the counter, and a synchronous counter value calculation unit 11d that performs a process of calculating a counter value synchronized using the updated counter value and the offset value are configured. The

  In this embodiment, the computer 10 (counter synchronizer 10 of the sensor terminal) receives the updated counter value of the relay terminal, stores it with a time stamp t1, and inputs the updated counter value of the relayed terminal. Then, it also functions as an external device to which the sensor terminal 2 is connected, which is stored with the time stamp t2.

  That is, a relay terminal and a relayed terminal transmit and receive signals such as data and control commands (that is, input / output) to / from a computer 10 (synchronizer 10 for a counter of a sensor terminal; an external device to which the sensor terminal 2 is connected). For example, it is electrically connected by a cable having a USB terminal or the like.

  Here, the counter synchronization method of the sensor terminal of the present invention is applied regardless of whether the number of relays (also called the number of hops) by the relay terminal between the coordinator 1 and the relayed terminal is one time or more than two times. Is possible. That is, according to the present invention, even when a relayed terminal receives a radio signal wirelessly transmitted from the coordinator 1 through a single relay by a single relay terminal, the relayed through a plurality of relays by a plurality of relay terminals. It is applicable even when the terminal receives.

  In the following, (1) the case where there is one relay terminal as in the wireless sensor network shown in FIG. 3 and (2) the case where there are two relay terminals as in the wireless sensor network shown in FIG. (3) A case where there are [n-1] relay terminals will be described.

(1) When there is one relay terminal First, as shown in FIG. 3, when the sensor terminal 2B relays a radio signal wirelessly transmitted from the coordinator 1 and the sensor terminal 2A receives the signal, the coordinator 1 and the sensor terminal 2A An example of synchronizing the counter with (in other words, calculating a correction value for synchronizing the counter value) will be described.

  In the example shown in FIG. 3, when attention is paid to transmission of a radio signal from the coordinator 1 to the sensor terminal 2A, the sensor terminal 2B is a relay terminal because the radio signal transmitted from the coordinator 1 is relayed to the sensor terminal 2A. The sensor terminal 2A is a relayed terminal because it receives a radio signal wirelessly transmitted from the coordinator 1 and relayed by the sensor terminal 2B. In other words, the sensor terminal 2B is a first hop sensor terminal, and the sensor terminal 2A is a second hop sensor terminal.

  The sensor terminal 2B operates as a relay terminal and the sensor terminal 2A is adjusted to be a relayed terminal, and the sensor terminal 2A and the sensor terminal 2B are connected to the computer 10 as shown in FIG. In the following, the relay terminal 2B and the relayed terminal 2A are also described.

  As shown in FIGS. 1 and 5, the synchronization method of the counter of the sensor terminal in this example is such that the coordinator 1 resets its counter value (S1) and transmits a radio signal (S2). The relay terminal 2B (the first hop sensor terminal) that relays the radio signal transmitted from the coordinator 1 receives the radio signal (S3), and the relay terminal 2B performs the update process of the counter value. The updated counter value C1 = c3−c2 + c1 of the relay terminal 2B is calculated using the counter value c3 at the start (S4), and the radio signal is transmitted after the relay terminal 2B calculates the updated counter value C1. The counter value c4 at the time of transmission (S5) and the relayed terminal 2A (second-hop sensor terminal) that receives the radio signal transmitted from the relay terminal 2B receives the radio signal (S6) The updated counter value C2 = c6−c5 + c4 of the relayed terminal 2A is calculated using the counter value c5 and the counter value c6 when the relayed terminal 2A starts the updating process of the counter value (S7). Time stamp t1 when the updated counter value C1 of the relay terminal 2B, the updated counter value C1 of the relay terminal 2B are input to the computer 10 (counter synchronizer 10 of the sensor terminal) as an external device, and relayed The updated counter value C2 of the terminal 2A and the time stamp t2 when the updated counter value C2 of the relayed terminal 2A is inputted to the computer 10 (counter synchronizer 10 of the sensor terminal) as an external device are used. Calculate offset value Vo = (t2-t1) x Ct-(C2-C1) (where Ct is the reciprocal of counter speed [count / time]) and calculate counter value C2 '= C2 + Vo (S8) The counter value C2 ′ is used as the synchronized counter value of the relayed terminal 2A.

  The counter synchronization apparatus 10 of the sensor terminal relays the counter value c1 when the coordinator 1 resets its counter value and transmits a radio signal and the relay terminal 2B that relays the radio signal transmitted from the coordinator 1. Using the counter value c2 when the (first hop sensor terminal) receives the radio signal and the counter value c3 when the relay terminal 2B starts the updating process of the counter value, the relay terminal 2B makes C1 = c3− The updated counter value C1 calculated by c2 + c1, the counter value c4 when the relay terminal 2B calculates the updated counter value C1, and the wireless signal transmitted from the relay terminal 2B are received. Counter value c5 when the relayed terminal 2A (second-hop sensor terminal) receives the radio signal, and the relayed terminal 2A starts updating the counter value. Data input receiving unit 11a as means for receiving an input of the updated counter value C2 calculated by C2 = c6−c5 + c4 by the relayed terminal 2A, and the updated counter value C1. A time stamp adding unit 11b as a means for giving the time stamp t1 when the updated counter value C2 is inputted and the time stamp t2 when the updated counter value C2 is inputted, and the updated counter value C1 of the relay terminal 2B; The time stamp t1 when the updated counter value C1 of the relay terminal 2B is input to the counter synchronizer 10 of the sensor terminal as an external device, the updated counter value C2 of the relayed terminal 2A, and the relayed terminal 2A Using the time stamp t2 when the updated counter value C2 is input to the counter synchronizer 10 of the sensor terminal as an external device, Offset value calculation unit 11c as means for calculating (Vt = t2−t1) × Ct− (C2−C1) (where Ct is the reciprocal of the counter speed [count / time]), and relayed terminal 2A A synchronized counter value calculation unit 11d as means for calculating the synchronized counter value C2 '= C2 + Vo.

  Further, the control unit 11 of the computer 10 (sensor terminal counter synchronizer 10: FIG. 2) executes a sensor terminal counter synchronization program 17 so that the coordinator 1 resets its counter value. The counter value c1 when the radio signal is transmitted, the counter value c2 when the relay terminal 2B (the first hop sensor terminal) that relays the radio signal transmitted from the coordinator 1 receives the radio signal, and the relay terminal 2B Using the counter value c3 when the counter value update processing starts, the updated counter value C1 calculated by C1 = c3−c2 + c1 by the relay terminal 2B and the updated counter value C1 calculated by the relay terminal 2B The counter value c4 when the radio signal is transmitted and the relayed terminal 2A (2 hops) that receives the radio signal transmitted from the relay terminal 2B. The counter value c5 when the second sensor terminal) receives the radio signal and the counter value c6 when the relayed terminal 2A starts updating the counter value are used by the relayed terminal 2A to obtain C2 = c6-c5 + c4. A data input receiving unit 11a that performs processing for receiving an input of the updated counter value C2 calculated by the above, a time stamp t1 when the updated counter value C1 is input, and an updated counter value C2 are input. The time stamp assigning unit 11b for performing the process of assigning the time stamp t2 when the relay terminal 2B is updated, the updated counter value C1 of the relay terminal 2B, and the updated counter value C1 of the relay terminal 2B The time stamp t1 when input to the synchronization device 10, the updated counter value C2 of the relayed terminal 2A, and the updated counter value C2 of the relayed terminal 2A are outside. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when input to the synchronization device 10 of the counter of the sensor terminal as the component device (where Ct: An offset value calculation unit 11c that performs processing of reciprocal of counter speed [count / time]) and a synchronous counter value calculation unit 11d that performs processing of calculating synchronized counter value C2 ′ = C2 + Vo of relayed terminal 2A are configured. The

  Then, as the processing of the counter synchronization method of the sensor terminal, first, the counter value of the coordinator 1 is reset (S1).

  Specifically, the external device 9 to which the coordinator 1 is connected resets the counter value from the external device 9 to the coordinator 1, and further includes a radio signal including a command to reset the counter value of the clock unit to the terminal (reset request signal and A control command for wirelessly transmitting a call is input.

  Then, the counter value of the clock unit of the coordinator 1 is reset.

  Subsequently, a radio signal is wirelessly transmitted by the coordinator 1 (S2).

  Specifically, the coordinator 1 wirelessly transmits the reset request signal and the counter value (c1) of the clock unit when the coordinator 1 wirelessly transmits the reset request signal (strictly speaking, immediately before transmission). (Broadcast).

  The counter value c1 is an elapsed counter value corresponding to the internal processing time from the application layer to the physical layer in the coordinator 1 after resetting the counter value of the clock unit.

  Next, the relay terminal 2B (first hop sensor terminal) receives a radio signal from the coordinator 1 (S3).

  At this time, the counter value (referred to as c2) of the clock unit when the relay terminal 2B receives the radio signal (reset request signal and counter value c1) from the coordinator 1 is held. Specifically, for example, it is stored in a storage area (storage device, storage element) provided in the relay terminal 2B.

  Subsequently, the counter value of the relay terminal 2B (first hop sensor terminal) is updated (S4).

  More specifically, the counter value of the clock unit when the relay terminal 2B starts updating the counter value (c3) is used, and the counter value of the relay terminal 2B is updated to the updated counter value C1 = c3−c2 + c1. Is done. This process is autonomously performed by the relay terminal 2B.

  At this time, the updated counter value C1 of the relay terminal 2B is stored with a time stamp (t1) attached by the counter synchronization device 10 of the sensor terminal (an external device to which the sensor terminal 2 is connected).

  Specifically, for example, an updated counter value C1 is output to the serial port together with a log message indicating that the relay terminal 2B has updated the counter value, and the updated counter value C1 is a sensor connected to the relay terminal 2B. The data is input to the terminal counter synchronizer 10 via the data input receiving unit 11 a of the control unit 11.

  Then, the time stamp assigning unit 11b of the control unit 11 adds the time stamp t1 when the updated counter value C1 is input to the counter synchronizer 10 of the sensor terminal, and the updated counter value C1 is stored in the memory 15. And saved.

  “C3−c2” is an elapsed counter value corresponding to the internal processing time from the physical layer to the application layer in the relay terminal 2B.

  Subsequently, a wireless signal is wirelessly transmitted by the relay terminal 2B (first-hop sensor terminal) (S5).

  Specifically, the relay terminal 2B causes the reset request signal and the counter value (referred to as c4) of the clock unit when the relay terminal 2B wirelessly transmits the reset request signal (strictly speaking, immediately before transmission) Wireless transmission (broadcast).

  The counter value c4 is an elapsed counter value from the updated counter value C1, and “c4−C1” is an elapsed counter value corresponding to the internal processing time from the application layer to the physical layer in the relay terminal 2B.

  Then, the relayed terminal 2A (second hop sensor terminal) receives a radio signal from the relay terminal 2B (first hop sensor terminal) (S6).

  At this time, the counter value (referred to as c5) of the clock unit when the relayed terminal 2A receives the radio signal (reset request signal and counter value c4) from the relay terminal 2B is held. Specifically, for example, it is stored in a storage area (storage device, storage element) provided in the relayed terminal 2A.

  Subsequently, the counter value of the relayed terminal 2A (second-hop sensor terminal) is updated (S7).

  More specifically, the counter value (c6) of the clock unit when the relayed terminal 2A starts updating the counter value is used, and the counter value of the relayed terminal 2A is the updated counter value C2 = c6-c5 + c4. Updated to This process is autonomously performed by the relayed terminal 2A.

  At this time, the updated counter value C2 of the relayed terminal 2A is stored with a time stamp (t2) attached by the counter synchronizer 10 of the sensor terminal (an external device to which the sensor terminal 2 is connected). .

  Specifically, for example, an updated counter value C2 is output to the serial port together with a log message indicating that the relayed terminal 2A has updated the counter value, and this updated counter value C2 is connected to the relayed terminal 2A. Is input to the counter 10 of the sensor terminal counter via the data input receiving unit 11a of the control unit 11.

  Then, the time stamp adding unit 11b of the control unit 11 adds the time stamp t2 when the updated counter value C2 is input to the counter synchronizer 10 of the sensor terminal, and the updated counter value C2 is stored in the memory 15. And saved.

  “C6−c5” is an elapsed counter value corresponding to the internal processing time from the physical layer to the application layer in the relayed terminal 2A.

  Next, the offset value Vo is calculated by the synchronization device 10 of the counter of the sensor terminal (S8).

  Specifically, the offset value calculation unit 11c of the control unit 11 updates the updated counter value C1 and the time stamp t1 stored in the memory 15 in the process of S4 and the updated value stored in the memory 15 in the process of S7. The counter value C2 and the time stamp t2 are read, and the offset value Vo is calculated by Equation 1. Then, the offset value Vo calculated by the offset value calculator 11 c is stored in the memory 15.

    (Equation 1) Vo = (t2−t1) × Ct− (C2−C1)

  Ct in Equation 1 is the reciprocal of the counter speed (in other words, time increment) of the clock part of the sensor terminal 2, that is, the reciprocal of the time per count, and the unit is, for example, [count / millisecond] or [count / Microsecond]. The time unit is aligned with the time units (for example, [millisecond], [microsecond]) of the time stamps t1 and t2.

  In the right side of Equation 1, “t2−t1” is an elapsed time from the completion of synchronization of the relay terminal 2B to the completion of synchronization of the relayed terminal 2A, and “C2−C1” is a counter using the internal processing time as a correction value. Since it is the difference between the estimated values, the offset value Vo calculated by Equation 1 is a counter error at the time of hopping.

  Subsequently, the updated counter value C2 stored in the memory 15 in the process of S7 is read and the offset value Vo stored in the memory 15 in the above process is read and synchronized by the synchronization counter value calculation unit 11d. The counter value C2 ′ is calculated by Equation 2.

    (Equation 2) C2 '= C2 + Vo

  Then, the offset value Vo is calculated for the sensor terminals constituting the wireless sensor network and the synchronized counter value C2 ′ is calculated. When the relayed terminal 2A is synchronized, C2 ′ is synchronized with respect to the relayed terminal 2A. By using it as a counter value, it is possible to obtain a counter value in which the counter error at the time of hop is corrected.

  In addition, the first hop wireless transmission counter value c4 sent from the relay terminal 2B, which is the first hop sensor terminal, to the relayed terminal 2A, which is the second hop sensor terminal, Since all processing delays at the sensor terminal are included, only the offset Vo is required, and the counter error can be corrected by taking this Vo into account.

(2) When there are two relay terminals Next, as shown in FIG. 7, the sensor terminal 2B relays the wireless signal wirelessly transmitted from the coordinator 1, and then the sensor terminal 2C relays the sensor terminal 2A. In the case of reception, an example of synchronizing the counters of the coordinator 1 and the sensor terminal 2A (in other words, calculating a correction value for synchronizing the counter value) will be described.

  In the example shown in FIG. 7, when attention is paid to transmission of a radio signal from the coordinator 1 to the sensor terminal 2A, the sensor terminal 2B is a relay terminal because the radio signal transmitted from the coordinator 1 is relayed to the sensor terminal 2C. The sensor terminal 2C is a relay terminal because it relays the radio signal transmitted from the sensor terminal 2B to the sensor terminal 2A, and the sensor terminal 2A is wirelessly transmitted from the coordinator 1 to the sensor terminal 2B and the sensor terminal. It is a relayed terminal because it receives a radio signal relayed by 2C. In other words, the sensor terminal 2B is a first hop sensor terminal, the sensor terminal 2C is a second hop sensor terminal, and the sensor terminal 2A is a third hop sensor terminal.

  Then, the sensor terminal 2B operates as a relay terminal and the sensor terminal 2C is adjusted to be a relayed terminal, and the sensor terminal 2B and the sensor terminal 2C are connected to the computer 10 as shown in FIG. Hereinafter, the relay terminal 2B, the relay terminal 2C, and the relayed terminal 2A are also described.

  6 and 9, the coordinator 1 resets its own counter value (S1) and transmits a radio signal after (S2). As shown in FIGS. 6 and 9, the counter value c1 The relay terminal 2B (the first hop sensor terminal) that relays the radio signal transmitted from the coordinator 1 receives the radio signal (S3), and the relay terminal 2B performs the update process of the counter value. The updated counter value C1 = c3−c2 + c1 of the relay terminal 2B is calculated using the counter value c3 at the start (S4), and the radio signal is transmitted after the relay terminal 2B calculates the updated counter value C1. The counter value c4 at the time of transmission (S5) and the relay terminal 2C (second-hop sensor terminal) that relays the radio signal transmitted from the relay terminal 2B receive the radio signal (S6). The updated counter value C2 = c6−c5 + c4 of the relay terminal 2C is calculated using the counter value c5 and the counter value c6 when the relay terminal 2C starts the updating process of the counter value (S7). The counter value c7 when 2C calculates the updated counter value C2 and transmits the radio signal (S8), and the relayed terminal 2A (the third hop sensor terminal) that receives the radio signal transmitted from the relay terminal 2C ) Receives the radio signal (S9) and the counter value c9 when the relayed terminal 2A starts updating the counter value, the updated counter value C3 of the relayed terminal 2A = c9-c8 + c7 is calculated (S10), and the updated counter value C1 of the relay terminal 2B and the updated counter value C1 of the relay terminal 2B are used as the external device. 0), the time stamp t1, the updated counter value C2 of the relay terminal 2C, and the updated counter value C2 of the relay terminal 2C are computers 10 as external devices (sensor terminal counter synchronizer 10). The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when it is input to (where Ct is the reciprocal of the counter speed [count / time]) and the counter The value C3 ′ = C3 + Vo is calculated (S11), and the counter value C3 ′ is used as the synchronized counter value of the relayed terminal 2A.

  The counter synchronization device of the sensor terminal is a relay terminal 2B that relays the counter value c1 when the coordinator 1 resets its own counter value and transmits a radio signal and the radio signal transmitted from the coordinator 1. Using the counter value c2 when the first hop sensor terminal receives the radio signal and the counter value c3 when the relay terminal 2B starts updating the counter value, the relay terminal 2B makes C1 = c3−c2 + c1. The updated counter value C1 calculated by the above, the counter value c4 when the relay terminal 2B transmits the wireless signal after calculating the updated counter value C1, and the wireless signal transmitted from the relay terminal 2B are relayed. The counter value c5 when the relay terminal 2C (the sensor terminal of the second hop) receives the radio signal and the count when the relay terminal 2C starts the update process of the counter value. The data input receiving unit 11a as means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the relay terminal 2C and the updated counter value C1. Time stamp t1 and a time stamp giving unit 11b as means for giving the time stamp t2 when the updated counter value C2 is inputted, the updated counter value C1 of the relay terminal 2B, and the relay terminal 2B The updated counter value C1 is input to the counter synchronizer 10 of the sensor terminal as an external device, the time stamp t1, the updated counter value C2 of the relay terminal 2C, and the updated counter value C2 of the relay terminal 2C. Is inputted to the synchronization device 10 of the counter of the sensor terminal as an external device, and the offset value Vo = (t2 t1) × Ct− (C2−C1) (where Ct is the reciprocal of the counter speed [count / time]) and the offset value calculation unit 11c as a means, and the relay terminal 2C calculates the updated counter value C2. Counter value c7 when the radio signal is transmitted after that, and counter value c8 when the relayed terminal 2A (the third hop sensor terminal) receiving the radio signal transmitted from the relay terminal 2C receives the radio signal From the counter value c9 when the relayed terminal 2A starts the updating process of the counter value, the updated counter value C3 calculated by C3 = c9−c8 + c7 by the relayed terminal 2A is used. A synchronization counter value calculation unit 11d is provided as means for calculating the synchronized counter value C3 ′ = C3 + Vo.

  Further, the control unit 11 of the computer 10 (sensor terminal counter synchronizer 10; also in this example has the configuration shown in FIG. 2) executes the sensor terminal counter synchronization program 17 so that the coordinator 1 When the counter value c1 when the radio signal is transmitted after resetting its own counter value and the relay terminal 2B (the first hop sensor terminal) that relays the radio signal transmitted from the coordinator 1 receives the radio signal Counter value C2 and the counter value c3 when the relay terminal 2B starts updating the counter value, the updated counter value C1 calculated by the relay terminal 2B by C1 = c3−c2 + c1, and the relay terminal The counter value c4 when the radio signal is transmitted after 2B calculates the updated counter value C1 and the radio signal transmitted from the relay terminal 2B The relay terminal 2C is used by using the counter value c5 when the relay terminal 2C (the second hop sensor terminal) receives the radio signal and the counter value c6 when the relay terminal 2C starts the update process of the counter value. A data input receiving unit 11a that performs processing for receiving an input of the updated counter value C2 calculated by C2 = c6−c5 + c4, and a time stamp t1 when the updated counter value C1 is input are given and updated. The time stamp assigning unit 11b that performs the process of assigning the time stamp t2 when the counter value C2 is input, the updated counter value C1 of the relay terminal 2B, and the updated counter value C1 of the relay terminal 2B are external devices. The time stamp t1 when input to the counter synchronizer 10 of the sensor terminal, the updated counter value C2 of the relay terminal 2C, and the relay terminal 2C The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated by using the time stamp t2 when the new counter value C2 is input to the counter 10 of the counter of the sensor terminal as an external device. (Where Ct is the reciprocal of the counter speed [count / time]) and the counter value when the radio signal is transmitted after the relay terminal 2C calculates the updated counter value C2 c7, the counter value c8 when the relayed terminal 2A (the third hop sensor terminal) receiving the radio signal transmitted from the relay terminal 2C receives the radio signal, and the relayed terminal 2A updating the counter value The updated counter value C3 calculated by C3 = c9−c8 + c7 by the relayed terminal 2A from the counter value c9 when the relayed terminal 2A is started, and the synchronized counter value C3 ′ = C3 + of the relayed terminal 2A is used. Synchronization counter value calculating unit 11d to perform the process of calculating the o is formed.

  Then, as the processing of the counter synchronization method of the sensor terminal, first, the counter value of the coordinator 1 is reset (S1).

  Specifically, the external device 9 to which the coordinator 1 is connected resets the counter value from the external device 9 to the coordinator 1, and further includes a radio signal including a command to reset the counter value of the clock unit to the terminal (reset request signal and A control command for wirelessly transmitting a call is input.

  Then, the counter value of the clock unit of the coordinator 1 is reset.

  Subsequently, a radio signal is wirelessly transmitted by the coordinator 1 (S2).

  Specifically, the coordinator 1 wirelessly transmits the reset request signal and the counter value (c1) of the clock unit when the coordinator 1 wirelessly transmits the reset request signal (strictly speaking, immediately before transmission). (Broadcast).

  The counter value c1 is an elapsed counter value corresponding to the internal processing time from the application layer to the physical layer in the coordinator 1 after resetting the counter value of the clock unit.

  Next, the relay terminal 2B (first hop sensor terminal) receives a radio signal from the coordinator 1 (S3).

  At this time, the counter value (referred to as c2) of the clock unit when the relay terminal 2B receives the radio signal (reset request signal and counter value c1) from the coordinator 1 is held. Specifically, for example, it is stored in a storage area (storage device, storage element) provided in the relay terminal 2B.

  Subsequently, the counter value of the relay terminal 2B (first hop sensor terminal) is updated (S4).

  More specifically, the counter value of the clock unit when the relay terminal 2B starts updating the counter value (c3) is used, and the counter value of the relay terminal 2B is updated to the updated counter value C1 = c3−c2 + c1. Is done. This process is autonomously performed by the relay terminal 2B.

  At this time, the updated counter value C1 of the relay terminal 2B is stored with a time stamp (t1) attached by the counter synchronization device 10 of the sensor terminal (an external device to which the sensor terminal 2 is connected).

  Specifically, for example, an updated counter value C1 is output to the serial port together with a log message indicating that the relay terminal 2B has updated the counter value, and the updated counter value C1 is a sensor connected to the relay terminal 2B. The data is input to the terminal counter synchronizer 10 via the data input receiving unit 11 a of the control unit 11.

  Then, the time stamp assigning unit 11b of the control unit 11 adds the time stamp t1 when the updated counter value C1 is input to the counter synchronizer 10 of the sensor terminal, and the updated counter value C1 is stored in the memory 15. And saved.

  “C3−c2” is an elapsed counter value corresponding to the internal processing time from the physical layer to the application layer in the relay terminal 2B.

  Subsequently, a wireless signal is wirelessly transmitted by the relay terminal 2B (first-hop sensor terminal) (S5).

  Specifically, the relay terminal 2B causes the reset request signal and the counter value (referred to as c4) of the clock unit when the relay terminal 2B wirelessly transmits the reset request signal (strictly speaking, immediately before transmission) Wireless transmission (broadcast).

  The counter value c4 is an elapsed counter value from the updated counter value C1, and “c4−C1” is an elapsed counter value corresponding to the internal processing time from the application layer to the physical layer in the relay terminal 2B.

  Next, the relay terminal 2C (second hop sensor terminal) receives a radio signal from the relay terminal 2B (first hop sensor terminal) (S6).

  At this time, the counter value (referred to as c5) of the clock unit when the relay terminal 2C receives the radio signal (reset request signal and counter value c4) from the relay terminal 2B is held. Specifically, for example, it is stored in a storage area (storage device, storage element) provided in the relay terminal 2C.

  Subsequently, the counter value of the relay terminal 2C (second hop sensor terminal) is updated (S7).

  Specifically, the counter value of the clock unit (represented as c6) when the relay terminal 2C starts the updating process of the counter value is used, and the counter value of the relay terminal 2C is updated to the updated counter value C2 = c6−c5 + c4. Is done. This process is autonomously performed by the relay terminal 2C.

  At this time, the updated counter value C2 of the relay terminal 2C is stored with a time stamp (t2) attached by the counter synchronizer 10 of the sensor terminal (an external device to which the sensor terminal 2 is connected).

  Specifically, for example, an updated counter value C2 is output to the serial port together with a log message indicating that the relay terminal 2C has updated the counter value, and the updated counter value C2 is a sensor connected to the relay terminal 2C. The data is input to the terminal counter synchronizer 10 via the data input receiving unit 11 a of the control unit 11.

  Then, the time stamp adding unit 11b of the control unit 11 adds the time stamp t2 when the updated counter value C2 is input to the counter synchronizer 10 of the sensor terminal, and the updated counter value C2 is stored in the memory 15. And saved.

  “C6−c5” is an elapsed counter value corresponding to the internal processing time from the physical layer to the application layer in the relay terminal 2C.

  Subsequently, a wireless signal is wirelessly transmitted by the relay terminal 2C (second-hop sensor terminal) (S8).

  Specifically, the reset request signal by the relay terminal 2C and the counter value (c7) of the clock unit when the relay terminal 2C wirelessly transmits the reset request signal (strictly speaking, immediately before transmission) Wireless transmission (broadcast).

  The counter value c7 is an elapsed counter value from the updated counter value C2, and “c7−C2” is an elapsed counter value corresponding to the internal processing time from the application layer to the physical layer in the relay terminal 2C.

  Then, the relayed terminal 2A (third hop sensor terminal) receives a radio signal from the relay terminal 2C (second hop sensor terminal) (S9).

  At this time, the counter value (referred to as c8) of the clock unit when the relayed terminal 2A receives the radio signal (reset request signal and counter value c7) from the relay terminal 2C is held. Specifically, for example, it is stored in a storage area (storage device, storage element) provided in the relayed terminal 2A.

  Subsequently, the counter value of the relayed terminal 2A (the third hop sensor terminal) is updated (S10).

  Specifically, the counter value of the clock unit (referred to as c9) when the relayed terminal 2A starts updating the counter value is used, and the counter value of the relayed terminal 2A is the updated counter value C3 = c9−c8 + c7. Updated to This process is autonomously performed by the relayed terminal 2A.

  Note that (c9−c8) is an elapsed counter value corresponding to the internal processing time from the physical layer to the application layer in the relayed terminal 2A.

  Next, the offset value Vo is calculated by the counter synchronizer 10 of the sensor terminal (S11).

  Specifically, the offset value calculation unit 11c of the control unit 11 updates the updated counter value C1 and the time stamp t1 stored in the memory 15 in the process of S4 and the updated value stored in the memory 15 in the process of S7. The counter value C2 and the time stamp t2 are read, and the offset value Vo is calculated by Equation 3. Then, the offset value Vo calculated by the offset value calculator 11 c is stored in the memory 15.

    (Equation 3) Vo = (t2-t1) * Ct- (C2-C1)

  Ct in Formula 3 is the reciprocal of the counter speed (in other words, time increment) of the clock portion of the sensor terminal 2, that is, the reciprocal of the time per count, and the unit is, for example, [count / millisecond] or [count / Microsecond]. The time unit is aligned with the time units (for example, [millisecond], [microsecond]) of the time stamps t1 and t2.

  Of the right side of Equation 3, “t2−t1” is an elapsed time from the completion of synchronization of the relay terminal 2B to the completion of synchronization of the relay terminal 2C, and “C2−C1” is a counter estimation using the internal processing time as a correction value. Since it is a difference between values, the offset value Vo calculated by Equation 3 is a counter error at the time of hopping.

  Subsequently, the offset value Vo stored in the memory 15 in the above-described process is read by the synchronous counter value calculation unit 11d, and the counter value C3 ′ synchronized with the updated counter value C3 calculated in the process of S10 is used. Is calculated by Equation 4.

    (Equation 3) C3 '= C3 + Vo

  Then, the offset value Vo is calculated for the sensor terminals constituting the wireless sensor network and the synchronized counter value C3 ′ is calculated. When the relayed terminal 2A is synchronized, C3 ′ is synchronized with respect to the relayed terminal 2A. By using it as a counter value, it is possible to obtain a counter value in which the counter error at the time of hop is corrected.

  In addition, the second hop wireless transmission counter value c7 sent from the relay terminal 2C as the second hop sensor terminal to the relayed terminal 2A as the third hop sensor terminal is up to the second hop. Therefore, only the Vo is required as an offset, and the counter error can be corrected by taking this Vo into consideration.

(3) When [n−1] Relay Terminals are Referring to the above example, [n−1] sensor terminals relay the radio signal wirelessly transmitted from the coordinator 1 and the nth hop sensor terminal Is received, the procedure for synchronizing the counter of the coordinator 1 and the n-th sensor terminal (in other words, calculating the correction value for synchronizing the counter value) is as follows (however, n is an integer of 3 or more).

  First, as a process corresponding to S1 to S5 in the example (2), the counter value of the coordinator 1 is reset (S1), and a radio signal is wirelessly transmitted by the coordinator 1 (wireless transmission counter value c1) (S2 ), The wireless signal from the coordinator 1 is received by the first hop sensor terminal which is a relay terminal (signal reception counter value c2) (S3), and the counter value of the first hop sensor terminal is updated (update process start) Hour counter value c3, updated counter value C1 = c3−c2 + c1, external device storage time stamp t1) (S4) The wireless signal is wirelessly transmitted by the first hop sensor terminal (wireless transmission counter value c4) (S5) ).

Next, as a process corresponding to S6 to S8 in the example of (2) above, a radio signal is received from the [k−1] hop sensor terminal by the k hop sensor terminal as a relay terminal (signal The counter value at the time of reception c _3k-1 ) and the counter value of the sensor terminal at the k-th hop are updated (the counter value c _3k at the start of the update process, the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k -1) +1} ) The process of wirelessly transmitting a wireless signal by the k-th hop sensor terminal (wireless transmission counter value c _{3k + 1} ) is repeated from k = 2 to k = n−1. When k = 2, the updated counter value C2 of the second hop sensor terminal is time stamped (t2) by the external device (sensor terminal counter synchronization device 10) to which the sensor terminal is connected. Attached and saved. On the other hand, when k ≧ 3, input of the updated counter value C _k from the sensor terminal to the external device and storage with a time stamp are not performed.

Then, as processing corresponding to S9 to S11 in the example of (2) above, a radio signal from the [n−1] -th hop sensor terminal is received by the n-th hop sensor terminal (a signal reception counter value c). _3n-1 ), and the counter value of the sensor terminal at the n-th hop is updated (counter value c _3n at the start of update processing, counter value after update Cn = c _3n −c _3n−1 + c _{3 (n−1) +1} ) , The offset value Vo is calculated by Equation 5 and the synchronized counter value Cn ′ is calculated by Equation 6.

(Equation 5) Vo = (t2-t1) * Ct- (C2-C1)
(Equation 6) Cn '= Cn + Vo

  Then, the offset value Vo is calculated for the sensor terminals constituting the wireless sensor network and the synchronized counter value Cn ′ is calculated. When the n-hop sensor terminal is synchronized, Cn ′ is set for the n-hop sensor terminal. As a counter value synchronized with each other, it is possible to obtain a counter value in which the counter error at the time of hop is corrected.

In addition, the counter value c _{3 (n−1) +1} at the time of [n−1] -th hop wireless transmission sent from the [n−1] -th hop sensor terminal to the n-th hop sensor terminal is Since all processing delays up to the [n−1] th hop are included, only Vo is required as an offset, and the counter error can be corrected by considering this Vo.

The counter synchronization method of the sensor terminal in this case is the first hop relaying the counter value c1 when the coordinator 1 resets its counter value and transmitting the radio signal and the radio signal transmitted from the coordinator 1. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and when the second hop sensor terminal starts updating the counter value Is used to calculate the updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor terminal. The time stamp t1 when the updated counter value C1 is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are stored in the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input (where Ct is the reciprocal of the counter speed [count / time]) and [ The counter value c3 _{(k-1) +1} when the k-1] -th hop sensor terminal calculates the updated counter value _Ck-1 and transmits the radio signal, and the [k-1] -th hop The k-th hop to relay the radio signal transmitted from the sensor terminal The counter value c _3k-1 when the capacitors terminal receives a radio signal, using the counter value c _3k when k th hop of the sensor terminal starts updating the counter value, the k-th hop of the sensor terminal The process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} is repeated from k = 3 to k = n (where n is an integer of 3 or more), and The counter value Cn ′ = Cn + Vo is calculated, and the counter value Cn ′ is used as the synchronized counter value of the n-hop sensor terminal.

Further, the counter synchronization device of the sensor terminal is configured to relay the radio signal transmitted from the coordinator 1 and the counter value c1 when the coordinator 1 resets its own counter value and transmits the radio signal. Using the counter value c2 when the sensor terminal receives the radio signal and the counter value c3 when the first hop sensor terminal starts the updating process of the counter value, the sensor terminal C1 = c3− The updated counter value C1 calculated by c2 + c1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1, and the wireless signal is transmitted, and the first hop sensor terminal transmits it. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and the second hop sensor terminal updates the counter value. Means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal using the counter value c6 at the start of the operation, and the updated counter value C1 Means for giving the time stamp t1 and the time stamp t2 when the updated counter value C2 is inputted, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor terminal The time stamp t1 when the updated counter value C1 is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are stored in the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input (where Ct is the reciprocal of the counter speed [count / time]. Means, as well as, a [k-1] after th hop of the sensor terminal update counter value C _k-1 counter value c ₃ when transmitting the radio signals from the calculated _{(k-1) +1, [} k -1] The counter value c _3k-1 when the k-hop sensor terminal that relays the radio signal transmitted from the hop sensor terminal receives the radio signal, and the k-hop sensor terminal updates the counter value. The process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} of the _k-th hop sensor terminal using the counter value c _3k at the start of the process is as follows: Using Cn repeatedly calculated from k = 3 to k = n (where n is an integer of 3 or more), means for calculating a synchronized counter value Cn ′ = Cn + Vo of the n-th hop sensor terminal .

Further, the control unit 11 of the computer 10 (sensor terminal counter synchronizer 10; which also has the configuration shown in FIG. 2 in this case) executes the sensor terminal counter synchronization program 17 so that the coordinator 1 A counter value c1 when the wireless signal is transmitted after resetting its own counter value, and a counter value c2 when the first hop sensor terminal relaying the wireless signal transmitted from the coordinator 1 receives the wireless signal; The updated counter value C1 calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c3 when the first hop sensor terminal starts the updating process of the counter value, and 1 The counter value c4 when the sensor terminal of the hop calculates the updated counter value C1 and then transmits a radio signal, and the sensor end of the first hop The counter value c5 when the second hop sensor terminal that relays the radio signal transmitted from the end receives the radio signal, and the counter value c6 when the second hop sensor terminal starts the update process of the counter value And a data input receiving unit 11a that performs processing for receiving an input of the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and when the updated counter value C1 is input. A time stamp assigning unit 11b that performs a process of assigning a time stamp t1 and a time stamp t2 when the updated counter value C2 is input, and an updated counter value C1 of the first hop sensor terminal and 1 A time stamp t1 when the updated counter value C1 of the hop sensor terminal is input to the counter 10 of the sensor terminal counter as an external device; The updated counter value C2 of the hop sensor terminal and the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the counter synchronizer 10 of the sensor terminal as an external device are used. Offset value Vo = (t2−t1) × Ct− (C2−C1) (where Ct is the reciprocal of the counter speed [count / time]), and [k− 1] The counter value c _{3 (k−1) +1} when the sensor terminal at the hop calculates the updated counter value C _k−1 and transmits the radio signal, and the sensor at the [k−1] hop The counter value c _3k-1 when the k-hop sensor terminal that relays the radio signal transmitted from the terminal receives the radio signal, and the counter when the k-hop sensor terminal starts update processing of the counter value using the value c _3k, the k-th hop of the sensor terminal Processing to calculate the new rear counter value _{C k = c 3k -c 3k-} 1 + c 3 (k-1) +1 is, k = 3 from k = n (where, n is an integer of 3 or more) are repeated until Using the calculated Cn, a synchronization counter value calculation unit 11d that performs a process of calculating the synchronized counter value Cn ′ = Cn + Vo of the n-hop sensor terminal is configured.

(4) When an offset value is given in advance to the sensor terminal In the examples (1) to (3) above, the updated counter values C2, C3, Cn are input to the external device (counter synchronizer 10 of the sensor terminal). Thus, synchronized counter values C2 ', C3', Cn 'are calculated. However, the offset value Vo is stored in advance in each sensor terminal, and when each sensor terminal outputs a counter value together with the collected sensor data, for example, it outputs the updated counter value plus the offset value Vo. You may do it.

(4-1) When there is a single relay terminal As shown in FIG. 3, as a wireless signal transmission, the wireless signal transmitted from the coordinator 1 is transmitted to the sensor terminal 2B (relay terminal, first hop sensor terminal). Is assumed to be received by the sensor terminal 2A (relayed terminal, second hop sensor terminal), and the connection configuration shown in FIG. 4 is constructed in advance and S1 to S8 described in (1) above. Is performed, the offset value Vo is calculated, and the offset value Vo is stored in the sensor terminal 2A.

  In actual transmission of a radio signal, when the sensor terminal wirelessly transmits a radio signal as a relay terminal, a flag indicating whether the radio signal is a retransmitted radio signal (hereinafter referred to as a retransmission flag) is included in the radio signal. Included. Specifically, for example, when the retransmission flag is 0 (zero), it is determined that the radio signal has arrived directly, and when the retransmission flag is 1, it is determined that the radio signal has arrived by retransmission (two or more hops).

  In actual transmission of the radio signal in this case, first, the coordinator 1 performs the processing of S1 and S2 in the example of (1) (counter value c_1 at the time of radio transmission). Note that “retransmission flag = 0” in the radio signal transmitted from the coordinator 1 by radio.

  Subsequently, the relay terminal 2B performs the processing from S3 to S5 in the example of (1) (signal reception counter value c_2, update processing start counter value c_3, post-update counter value C_1 = c_3−c_2 + c_1, Wireless transmission counter value c_4). However, the updated counter value C_1 is not input from the relay terminal 2B to the external device (sensor terminal counter synchronization device 10) and stored with a time stamp in the process of S4. Further, “retransmission flag = 1” is set in the radio signal transmitted by radio from the relay terminal 2B.

  Further, in the relayed terminal 2A, the processes of S6 and S7 in the example of (1) are performed (counter value c_5 at the time of signal reception, counter value c_6 at the start of update processing, counter value C_2 after update C_2 = c_6−c_5 + c_4). However, the updated counter value C_2 from the relayed terminal 2A to the external device (counter synchronization apparatus 10 of the sensor terminal) and the storage with the time stamp are not performed in the process of S7.

  Then, the relayed terminal 2A (assuming that it is assumed that the sensor terminal is in the second hop. In other words, the sensor terminal that can receive the radio signal in the first hop and the second hop) is, for example, When the counter value is output together with the collected sensor data, if the received wireless signal is “retransmission flag = 1”, it is determined that the wireless signal has arrived by retransmission, and is offset to its own updated counter value C_2 The counter value C_2 ′ (= C_2 + Vo) synchronized by adding the value Vo is autonomously calculated and output.

  On the other hand, the relayed terminal 2A (assuming that it is assumed that the sensor terminal is in the second hop. In other words, the sensor terminal that can receive the radio signal in the first hop and the second hop) is, for example, When the counter value is output together with the collected sensor data, if the received radio signal is “Retransmission flag = 0”, it is determined that the radio signal has arrived directly, and the updated counter value C_2 is output as it is. To do. At this time, the relayed terminal 2A directly receives the radio signal wirelessly transmitted from the coordinator 1, that is, receives the counter value c_1 at the time of radio transmission of the coordinator 1 as the counter value included in the radio signal. ing. Therefore, the updated counter value C_2 of the relayed terminal 2A is actually calculated by C_2 = c_6−c_5 + c_1.

  The counter synchronization method of the sensor terminal in this case is the first hop relaying the counter value c1 when the coordinator 1 resets its counter value and transmitting the radio signal and the radio signal transmitted from the coordinator 1. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal receiving the received radio signal receives the radio signal and when the second hop sensor terminal starts updating the counter value Is used to calculate the updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor terminal. The time stamp t1 when the updated counter value C1 is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are stored in the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input (where Ct is the reciprocal of the counter speed [count / time]), A counter when the first hop sensor terminal that relays the radio signal transmitted from the coordinator 1 transmits a radio signal after the coordinator 1 resets its counter value for each actual transmission of the radio signal The updated counter value is used using c_1, the counter value c_2 when the first hop sensor terminal receives the radio signal, and the counter value c_3 when the first hop sensor terminal starts updating the counter value. C_1 = c_3−c_2 + c_1 is calculated, and when the second hop sensor terminal determines that the radio signal received by itself is retransmitted, the first hop sensor terminal updates the updated counter value. The counter value c_4 when the wireless signal is transmitted after calculating C_1, the counter value c_5 when the second hop sensor terminal receives the wireless signal, and the second hop sensor terminal update processing of the counter value. The updated counter value C_2 = c_6−c_5 + c_4 is calculated using the counter value c_6 at the start time, and the synchronized counter value C_2 ′ = C_2 + Vo is output, while the radio received by itself When it is determined that the signal has arrived directly, the counter value c_1 when the coordinator 1 resets its counter value and then transmits a wireless signal, and the second hop sensor terminal receives the wireless signal The updated counter value C_2 = c_6−c_5 + c_1 is calculated using the counter value c_5 at the time and the counter value c_6 when the second hop sensor terminal starts the update process of the counter value, and the updated counter value C_2 is output. The second hop sensor terminal here includes both receiving a radio signal retransmitted by the first hop sensor terminal and receiving a radio signal transmitted from the coordinator 1 directly. It means the sensor terminal to obtain.

(4-2) When there are two relay terminals As shown in FIG. 7, the wireless signal transmitted from the coordinator 1 is transmitted as a wireless signal to the sensor terminal 2B (relay terminal, first hop sensor terminal). ) Is relayed and then sensor terminal 2C (relay terminal, second hop sensor terminal) relays and sensor terminal 2A (relayed terminal, third hop sensor terminal) receives, The connection configuration shown in FIG. 8 is constructed, the processes from S1 to S7 and the process of S11 described in (2) above are performed, the offset value Vo is calculated, and the offset value Vo is stored in the sensor terminal 2A. (It may be stored in the sensor terminal 2C as necessary).

  Further, in actual transmission of a radio signal, when the sensor terminal wirelessly transmits a radio signal as a relay terminal, a flag indicating whether the radio signal is a retransmitted radio signal (when retransmission flag: retransmission flag = 0) It is determined that the radio signal has arrived directly, and when the retransmission flag = 1, the radio signal is determined to have been retransmitted (determined to have arrived by two or more hops).

  In actual transmission of the radio signal in this case, first, the coordinator 1 performs the processing of S1 and S2 in the example of (2) (counter value c_1 at the time of radio transmission). Note that “retransmission flag = 0” in the radio signal transmitted from the coordinator 1 by radio.

  Subsequently, in the relay terminal 2B, the processing from S3 to S5 in the example of (2) is performed (counter value c_2 at the time of signal reception, counter value c_3 at the start of update processing, counter value after update C_1 = c_3−c_2 + c_1, Wireless transmission counter value c_4). However, the updated counter value C_1 is not input from the relay terminal 2B to the external device (sensor terminal counter synchronization device 10) and stored with a time stamp in the process of S4. Further, “retransmission flag = 1” is set in the radio signal transmitted by radio from the relay terminal 2B.

  Further, the relay terminal 2C performs the processing from S6 to S8 in the example (2) (signal reception counter value c_5, update process start counter value c_6, post-update counter value C_2 = c_6−c_5 + c_4, wireless Transmission counter value c_7). However, the updated counter value C_2 from the relay terminal 2C to the external device (sensor terminal counter synchronization device 10) and the storage with the time stamp added are not performed in the process of S7. When the relay terminal 2C performs radio transmission, “retransmission flag = 1” is maintained.

  In the relayed terminal 2A, the processes of S9 and S10 in the example (2) are performed (counter value c_8 at the time of signal reception, counter value c_9 at the start of update processing, and counter value C_3 after update C_3 = c_9−c_8 + c_7).

  Then, the relayed terminal 2A (assuming that it is assumed that the sensor terminal is the third hop. In other words, the sensor terminal that can receive the radio signal at the first hop and the third hop) is, for example, When the counter value is output together with the collected sensor data, if the received radio signal is “retransmission flag = 1”, it is determined that the radio signal has arrived by retransmission, and is offset to its own updated counter value C_3 The counter value C_3 ′ (= C_3 + Vo) synchronized by adding the value Vo is autonomously calculated and output.

  On the other hand, the relayed terminal 2A (assuming that it is assumed that the sensor terminal is in the third hop. In other words, the sensor terminal that can receive the radio signal in the first hop and the third hop) is, for example, When the counter value is output together with the collected sensor data, if the received radio signal is “retransmission flag = 0”, it is determined that the radio signal has arrived directly, and the updated counter value C_3 is output as it is. To do. At this time, the relayed terminal 2A directly receives the radio signal wirelessly transmitted from the coordinator 1, that is, receives the counter value c_1 at the time of radio transmission of the coordinator 1 as the counter value included in the radio signal. ing. Therefore, the updated counter value C_3 of the relayed terminal 2A is actually calculated by C_3 = c_9−c_8 + c_1.

  Note that the relay terminal 2C (assuming that it is assumed that the sensor terminal is in the second hop. In other words, the sensor terminal that can receive the radio signal in the first hop and the second hop) is collected, for example. When the counter value is output together with the received sensor data, if the received wireless signal is “retransmission flag = 1”, it is determined that the wireless signal has arrived by retransmission, and an offset value is added to its own updated counter value C_2. The counter value C_2 ′ (= C_2 + Vo) synchronized by adding Vo may be autonomously calculated and output.

  On the other hand, the relay terminal 2C (assuming that it is assumed that the sensor terminal is in the second hop. In other words, the sensor terminal that can receive the radio signal in the first hop and the second hop) is collected, for example. When the counter value is output together with the received sensor data, if the received wireless signal is “retransmission flag = 0”, it is determined that the wireless signal has arrived directly, and the updated counter value C_2 is output as it is. You may do it. At this time, the relay terminal 2C directly receives the radio signal wirelessly transmitted from the coordinator 1, that is, receives the counter value c_1 at the time of radio transmission of the coordinator 1 as the counter value included in the radio signal. Yes. Therefore, the updated counter value C_2 of the relay terminal 2C is actually calculated by C_2 = c_6−c_5 + c_1.

  The counter synchronization method of the sensor terminal in this case is the first hop relaying the counter value c1 when the coordinator 1 resets its counter value and transmitting the radio signal and the radio signal transmitted from the coordinator 1. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and when the second hop sensor terminal starts updating the counter value Is used to calculate the updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor terminal. The time stamp t1 when the updated counter value C1 is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are stored in the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input (where Ct is the reciprocal of the counter speed [count / time]), A counter when the first hop sensor terminal that relays the radio signal transmitted from the coordinator 1 transmits a radio signal after the coordinator 1 resets its counter value for each actual transmission of the radio signal The updated counter value is used using c_1, the counter value c_2 when the first hop sensor terminal receives the radio signal, and the counter value c_3 when the first hop sensor terminal starts updating the counter value. C_1 = c_3−c_2 + c_1 is calculated, and the second hop sensor terminal that relays the radio signal transmitted from the first hop sensor terminal calculates the updated counter value C_1. Counter value c_4 when the radio signal is transmitted from the counter, counter value c_5 when the second hop sensor terminal receives the radio signal, and counter when the second hop sensor terminal starts the update process of the counter value The updated counter value C_2 = c_6−c_5 + c_4 is calculated using the value c_6, and the third hop sensor terminal determines that the radio signal received by itself has arrived by retransmission. When the second hop sensor terminal calculates the updated counter value C_2, the counter value c_7 when the wireless signal is transmitted, and when the third hop sensor terminal receives the wireless signal, the counter value c_8 The updated counter value C_3 = c_9−c_8 + c_7 is calculated using the counter value c_9 when the third hop sensor terminal starts the counter value update process, and the synchronized counter value C_3 ′ = C_3 + Vo is output. On the other hand, if it is determined that the radio signal received by the coordinator 1 has arrived directly, the counter value c_1 when the coordinator 1 resets its counter value and then transmits the radio signal, and the third hop Counter after updating using the counter value c_8 when the first sensor terminal receives the wireless signal and the counter value c_9 when the third hop sensor terminal starts the updating process of the counter value. With calculating the C_3 = c_9-c_8 + c_1, will output the updated counter value C_3. The third hop sensor terminal here includes both receiving a radio signal retransmitted by the second hop sensor terminal and directly receiving a radio signal transmitted from the coordinator 1. It means the sensor terminal to obtain.

(4-3) When there are [n-1] relay terminals in some cases [n-1] sensor terminals (relay terminals, 1 hop) are transmitted from the coordinator 1 as radio signal transmissions. It is assumed that sensor terminals from the first to the [n-1] hop) (where n is an integer of 3 or more) are sequentially relayed and received by the sensor terminal (relayed terminal, n-hop sensor terminal). In advance, a coordinator 1 and a first hop sensor terminal and a second hop sensor terminal (which may be candidate sensor terminals for the first hop and the second hop in the wireless sensor network) constituting the wireless sensor network are used. Then, the processing necessary for calculating the offset value Vo described in (3) above is performed to calculate the offset value Vo, and the offset value Vo is stored in the n-hop sensor terminal (note that If necessary, it may be stored in the sensor terminal from the second hop to the [n-1] hop).

  Further, in actual transmission of a radio signal, when the sensor terminal wirelessly transmits a radio signal as a relay terminal, a flag indicating whether the radio signal is a retransmitted radio signal (when retransmission flag: retransmission flag = 0) It is determined that the radio signal has arrived directly, and when the retransmission flag = 1, the radio signal is determined to have been retransmitted (determined to have arrived by two or more hops).

  In the actual transmission of the radio signal in this case, first, the coordinator 1 performs the processing of S1 and S2 in the example of (3) (the counter value c_1 at the time of radio transmission). Note that “retransmission flag = 0” in the radio signal transmitted from the coordinator 1 by radio.

  Subsequently, in the sensor terminal of the first hop, the processing from S3 to S5 in the example of (3) is performed (counter value c_2 at the time of signal reception, counter value c_3 at the start of update processing, and counter value C_1 after updating C_1 = c_3) −c_2 + c_1, wireless transmission counter value c_4). However, the updated counter value C_1 from the first hop sensor terminal to the external device (sensor terminal counter synchronization device 10) in the process of S4 and the storage with the time stamp added are not performed. Also, “retransmission flag = 1” is set in a radio signal wirelessly transmitted by the first hop sensor terminal.

In the k-th hop sensor terminal, the processing associated with the k-th hop sensor terminal in the example (3) is repeatedly performed from k = 2 to k = n−1 (counter value _{c_3k−} at the time of signal reception _{). 1,} the update processing start counter value c_ _3k, updated counter value _{C_ k = c_ 3k -c_ 3k-} 1 + c_ 3 (k-1) +1, the wireless transmission time counter value c_ _{3k + 1).} However, when k = 2, the updated counter value C_2 from the second hop sensor terminal to the external device (sensor terminal counter synchronization device 10) and the storage with the time stamp attached are not performed. . When the k-th hop sensor terminal performs radio transmission, “retransmission flag = 1” is maintained.

Further, in the n-hop sensor terminal, a process related to the calculation of the updated counter value C_n of the n-hop sensor terminal in the example of (3) is performed (the counter value c_3n _-1 at the time of signal reception, the update process) start counter value c_ _3n, updated counter value _{C_n = c_ 3n -c_ 3n-1} + c_ 3 (n-1) +1).

  An n-hop sensor terminal (where n is an integer equal to or greater than 3) (assuming an n-hop sensor terminal. In other words, receiving a radio signal at the first hop and receiving at the n-hop. If the received wireless signal is “retransmission flag = 1” when the sensor terminal) outputs a counter value together with the collected sensor data, for example, the wireless signal has arrived by retransmission The counter value C_n ′ (= C_n + Vo) that is synchronized by adding the offset value Vo to the updated counter value C_n is autonomously calculated and output.

On the other hand, an n-hop sensor terminal (where n is an integer of 3 or more) (assuming an n-hop sensor terminal. In other words, receiving a radio signal at the first hop and receiving at the n-hop. When the received wireless signal is “retransmission flag = 0”, for example, when the sensor terminal) outputs a counter value together with the collected sensor data, it is determined that the wireless signal has arrived directly Then, the counter value C_n after update is output as it is. At this time, the nth hop sensor terminal directly receives the radio signal wirelessly transmitted from the coordinator 1, that is, the counter value c_1 of the coordinator 1 is used as the counter value included in the radio signal. Receiving. Thus, the updated counter value C_n the n th hop of the sensor terminal is actually being calculated by _{C_n = c_ 3n -c_ 3n-1} + c_1.

Note that the k-hop sensor terminal (2 ≦ k ≦ n−1) (assuming the k-hop sensor terminal. In other words, receiving a radio signal at the first hop and receiving at the k-hop. When the received wireless signal is “retransmission flag = 1” when the sensor terminal outputs a counter value together with collected sensor data, for example, the wireless signal arrives by retransmission. was a determined, may be output to autonomously calculate its counter value synchronized by adding the offset value Vo to updated counter value C_ _k C_ _k 'a (= C_ _k + Vo).

On the other hand, the sensor terminal of the k hop (however, 2 ≦ k ≦ n−1) (assuming the sensor terminal of the k hop. In other words, receiving a radio signal at the first hop and receiving at the k hop. When the received wireless signal is “retransmission flag = 0” when the sensor terminal) outputs a counter value together with the collected sensor data, for example, the wireless signal has arrived directly. discriminated, it may be the updated counter value C_ _k itself to output it. At this time, the sensor terminal at the k-th hop directly receives the radio signal wirelessly transmitted from the coordinator 1, that is, the counter value c_1 of the coordinator 1 is used as the counter value included in the radio signal. Receiving. Thus, the updated counter value C_ _k of k-th hop of the sensor terminal are calculated in practice by _{C_ k = c_ 3k -c_ 3k-} 1 + c_1.

The counter synchronization method of the sensor terminal in this case is the first hop relaying the counter value c1 when the coordinator 1 resets its counter value and transmitting the radio signal and the radio signal transmitted from the coordinator 1. Counter after updating the first hop sensor terminal using the counter value c2 when the first sensor terminal receives the wireless signal and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1 = c3−c2 + c1 is calculated, and the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and then transmits a radio signal is transmitted from the first hop sensor terminal. Counter value c5 when the second hop sensor terminal that relays the received radio signal receives the radio signal, and when the second hop sensor terminal starts updating the counter value Is used to calculate the updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal, and the updated counter value C1 of the first hop sensor terminal and the first hop sensor terminal. The time stamp t1 when the updated counter value C1 is input to the external device, the updated counter value C2 of the second hop sensor terminal, and the updated counter value C2 of the second hop sensor terminal are stored in the external device. The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 at the time of input (where Ct is the reciprocal of the counter speed [count / time]), A counter when the first hop sensor terminal that relays the radio signal transmitted from the coordinator 1 transmits a radio signal after the coordinator 1 resets its counter value for each actual transmission of the radio signal The updated counter value is used using c_1, the counter value c_2 when the first hop sensor terminal receives the radio signal, and the counter value c_3 when the first hop sensor terminal starts updating the counter value. C_1 = c_3−c_2 + c_1 is calculated, and each sensor terminal as the k-th hop that relays the radio signal transmitted from the [k−1] -th hop sensor terminal is the [k−1] -th hop sensor terminal. Counter value C_3 _{(k-1) +1} when the wireless signal is transmitted after calculating the updated counter value C_k _-1, and the counter value when the _k-th sensor terminal receives the wireless signal and c_ _3k-1, using the counter value c_ _3k when k th hop of the sensor terminal starts updating the counter value updated counter value _{C_ k = c_ 3k -c_ 3k-} 1 + c_ 3 (k- ₁₎ calculated ₊₁ (where, 2 ≦ k ≦ n-1 , n is an integer of 3 or more), and, n -Up th sensor terminal, the radio signals it receives when it is determined that those arriving by retransmissions is to calculate the [n-1] th hop of the sensor terminal updated counter value C_ _n-1 the counter value c_ _{3 (n-1) +1} when transmitting the radio signals from, the counter value c_ _3n-1 when n th hop of the sensor terminal receives a radio signal, n th hop of the sensor terminal counter but using the counter value c_ _3n when starting the updating process of the counter value, together with calculating the updated counter value _{C_n = c_ 3n -c_ 3n-1} + c_ 3 (n-1) +1, which is synchronized When the value C_n ′ = C_n + Vo is output and the wireless signal received by itself is determined to have arrived directly, the counter when the coordinator 1 transmits the wireless signal after resetting its counter value The value c_1 and the value when the nth hop sensor terminal receives a radio signal. A pointer value c_ _3n-1, using the counter value c_ _3n when n th hop of the sensor terminal starts updating the counter value, to calculate the updated counter value _{C_n = c_ 3n -c_ 3n-1} + c_1 At the same time, the updated counter value C_n is output. Here, the n-hop sensor terminal refers to receiving a radio signal retransmitted by the [n−1] -hop sensor terminal and directly receiving a radio signal transmitted from the coordinator 1. It means a sensor terminal that can be both.

  According to the sensor terminal counter synchronization method, the synchronization device, and the synchronization program configured as in the above examples (1) to (4), after the relay terminal completes synchronization, the relay terminal completes synchronization. Since the offset value Vo, which is a counter error at the time of hop, is calculated in consideration of the time and the difference between the counter estimation values using the internal processing time as a correction value, the offset of the sensor terminals constituting the wireless sensor network By calculating the value Vo and using the counter value C ′ (= C + Vo) as a synchronized counter value, it is possible to determine the counter value in which the counter error at the time of hop is corrected, and configure a wireless sensor network. It becomes possible to improve the synchronization accuracy of the counter value of the sensor terminal.

  In addition, although embodiment in the example of said (1) thru | or (4) is an example of the suitable form at the time of implementing this invention, embodiment of this invention is not limited to the above-mentioned form, The present invention can be variously modified without departing from the gist of the present invention. For example, in the above-described embodiment, the sensor terminal counter synchronizer 10 (computer 10) is connected to the sensor terminal 2 in which the updated counter value of the relay terminal or the relayed terminal is input and the time stamp is added and stored. However, the present invention is not limited to this configuration, and the sensor terminal 2 is connected separately from the counter synchronization device 10 of the sensor terminal, and the updated counter value of the relay terminal or the relayed terminal is An external device to be input may be provided. That is, the updated counter value of the relay terminal or relayed terminal is input to the external device to which the sensor terminal 2 is connected, and a time stamp is given and stored, and these data are wired from the external device to which the sensor terminal 2 is connected. Alternatively, the signal may be input to the counter synchronization device of the sensor terminal via wireless communication or a storage medium. In this case, the counter synchronization device of the sensor terminal does not include the time stamp assigning unit 11b.

DESCRIPTION OF SYMBOLS 1 Coordinator 2A Relayed terminal 2B Relay terminal 2C Relay terminal 9 External device to which coordinator is connected 10 Counter synchronization device of sensor terminal (external device to which sensor terminal is connected)
DESCRIPTION OF SYMBOLS 11 Control part 12 Memory | storage part 13 Input part 14 Display part 15 Memory 17 Counter synchronization program of sensor terminal

Claims (14)

  The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. In addition, the counter value c4 when the sensor terminal of the first hop calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the sensor terminal of the first hop are received. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the post counter value C2 is input to the external device (where Ct is the reciprocal of the counter speed) [Count / Time]) and a counter value C2 ′ = C2 + Vo, and the counter value C2 ′ is used as the synchronized counter value of the second hop sensor terminal. Method of synchronization data.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. Further, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the first hop sensor terminal are relayed. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the post counter value C2 is input to the external device (where Ct is the reciprocal of the counter speed) [Count / Time]) and the counter value c7 when the second hop sensor terminal calculates the updated counter value C2 and transmits a radio signal, and the second hop sensor terminal The counter value c8 when the third hop sensor terminal receiving the radio signal receives the radio signal and the counter value c9 when the third hop sensor terminal starts updating the counter value are used. The updated counter value C3 = c9−c8 + c7 of the third hop sensor terminal is calculated, and the counter value C3 ′ = C3 + Vo is calculated. The counter value C3 ′ is synchronized with the third hop sensor terminal. A counter synchronization method for a sensor terminal, wherein the counter is used as a counter value. The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. Further, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the first hop sensor terminal are relayed. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the post counter value C2 is input to the external device (where Ct is the reciprocal of the counter speed) [Count / Time]) and the counter value c _{3 (k−1) +1} when the sensor terminal at the [k−1] -th hop calculates the updated counter value C _k−1 and transmits the radio signal. And from the [k-1] hop sensor terminal The counter value c _3k-1 when k th hop of the sensor terminal for relaying signals to said wireless signal receiving the radio signal, when the k-th hop of the sensor terminal starts updating the counter value Using the counter value c _3k , the process of calculating the updated counter value C _k = c _3k −c _3k−1 + c _{3 (k−1) +1} of the _k-th hop sensor terminal is performed from k = 3 to k = N (where n is an integer greater than or equal to 3), and the counter value Cn ′ = Cn + Vo is calculated, and the counter value Cn ′ is used as the synchronized counter value of the n-th hop sensor terminal. A method of synchronizing the counter of the sensor terminal.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. In addition, the counter value c4 when the sensor terminal of the first hop calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the sensor terminal of the first hop are received. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the subsequent counter value C2 is input to the external device (where Ct is the counter speed) The counter value c_1 when the sensor terminal of the first hop transmits a radio signal after the coordinator resets its counter value every time a radio signal is actually transmitted. , The counter value c_2 when the first hop sensor terminal receives the wireless signal and the counter value c_3 when the first hop sensor terminal starts updating the counter value, When the value C_1 = c_3−c_2 + c_1 is calculated and the sensor terminal of the second hop determines that the radio signal received by the second hop is retransmitted, the sensor terminal of the first hop The counter value c_4 when the wireless signal is transmitted after calculating the updated counter value C_1, the counter value c_5 when the second hop sensor terminal receives the wireless signal, and the second hop sensor The updated counter value C_2 = c_6−c_5 + c_4 is calculated using the counter value c_6 when the terminal starts the updating process of the counter value, and the synchronized counter value C_2 ′ = C_2 + Vo is calculated. The method of synchronizing the counter of the sensor terminals and outputs.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. Further, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the first hop sensor terminal are relayed. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the subsequent counter value C2 is input to the external device (where Ct is the counter speed) The counter value c_1 when the sensor terminal of the first hop transmits a radio signal after the coordinator resets its counter value every time a radio signal is actually transmitted. , The counter value c_2 when the first hop sensor terminal receives the wireless signal and the counter value c_3 when the first hop sensor terminal starts updating the counter value, The value C_1 = c_3−c_2 + c_1 is calculated, and the counter value when the second hop sensor terminal transmits the wireless signal after the first hop sensor terminal calculates the updated counter value C_1. update using c_4, a counter value c_5 when the second hop sensor terminal receives the wireless signal, and a counter value c_6 when the second hop sensor terminal starts a counter value update process. When the post-counter value C_2 = c_6−c_5 + c_4 is calculated, and the third hop sensor terminal determines that the wireless signal received by the third hop is retransmitted, A counter value c_7 when the sensor terminal of the eye calculates the updated counter value C_2 and transmits the wireless signal; a counter value c_8 when the sensor terminal of the third hop receives the wireless signal; The updated counter value C_3 = c_9−c_8 + c_7 is calculated using the counter value c_9 when the third hop sensor terminal starts the updating process of the counter value, and the synchronized counter value C_3 ′ = C_3 + Vo is output. A method of synchronizing a counter of a sensor terminal. The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. Using the counter value c2 and the counter value c3 when the first hop sensor terminal starts the update process of the counter value, the updated counter value C1 = c3−c2 + c1 of the first hop sensor terminal is calculated. Further, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal and the radio signal transmitted from the first hop sensor terminal are relayed. The counter value c5 when the second hop sensor terminal receives the wireless signal and the count value when the second hop sensor terminal starts updating the counter value. The updated counter value C2 = c6−c5 + c4 of the second hop sensor terminal is calculated using the counter value c6, and the updated counter value C1 of the first hop sensor terminal is further calculated. A time stamp t1 when the updated counter value C1 of the second sensor terminal is input to an external device, the updated counter value C2 of the second hop sensor terminal, and the update of the second hop sensor terminal The offset value Vo = (t2−t1) × Ct− (C2−C1) is calculated using the time stamp t2 when the subsequent counter value C2 is input to the external device (where Ct is the counter speed) The counter value c_1 when the sensor terminal of the first hop transmits a radio signal after the coordinator resets its counter value every time a radio signal is actually transmitted. , The counter value c_2 when the first hop sensor terminal receives the wireless signal and the counter value c_3 when the first hop sensor terminal starts updating the counter value, The value C_1 = c_3−c_2 + c_1 is calculated, and each sensor terminal as the k-th hop that relays the radio signal transmitted from the [k−1] -th hop sensor terminal is transmitted to the [k−1] -th hop. The counter value c_3 _{(k-1) +1} when the sensor terminal calculates the updated counter value C_k _-1 and then transmits the radio signal, and the k-hop sensor terminal has received the radio signal the counter value c_ _3k-1 of time, the k-th hop of the sensor terminal using the counter value c_ _3k when starting the updating process of the counter value, updated counter value _{C_ k = c_ 3k -c_ 3k-} 1 + c_ _{3 (k-1)} calculated ₊₁ (where, 2 ≦ k ≦ n-1 , n is 3 or more Integer), and, n th hop of the sensor terminal, when a radio signal that it has received is determined that it is intended to arrive by retransmission, [n-1] th hop of the sensor terminal updated counter value C_ after calculating the _n-1 at the time of transmitting a radio signal counter value c_ _{3 (n-1) +1,} wherein n th hop of the sensor terminal counter value when receiving the radio signal c_ _3n-1 when the n th hop of the sensor terminal using the counter value c_ _3n when starting the updating process of the counter value, the updated counter value _{C_n = c_ 3n -c_ 3n-1} + c_ 3 (n-1) +1 And synchronizing counter value C_n ′ = C_n + Vo is output, and the counter synchronization method of the sensor terminal is characterized in that:   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal receiving the wireless signal is received, and the second hop sensor terminal updates the counter value. Means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal using the counter value c6 at the time of starting, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]) and means for calculating the synchronized counter value C2 ′ = C2 + Vo of the second hop sensor terminal. Synchronizer of sensor nodes, wherein the counter.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal that relays the radio signal receives the wireless signal, and the second hop sensor terminal updates the counter value. Means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal using the counter value c6 at the time of starting, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]), and when the second hop sensor terminal calculates the updated counter value C2 and transmits a radio signal. Counter value c7, counter value c8 when the third hop sensor terminal receiving the radio signal transmitted from the second hop sensor terminal receives the radio signal, and the third hop sensor terminal The updated counter value C3 of the third hop sensor terminal calculated from C3 = c9−c8 + c7 from the counter value c9 when the counter value update process is started is used to synchronize the third hop sensor terminal. A counter for a counter of a sensor terminal, characterized in that it has means for calculating the counter value C3 '= C3 + Vo. The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal that relays the radio signal receives the wireless signal, and the second hop sensor terminal updates the counter value. Means for receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal using the counter value c6 at the time of starting, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]), and the sensor terminal at the [k−1] hop calculates the updated counter value C _k−1 and transmits the radio signal. When Counter value c ₃ and _{(k-1) +1,} the [k-1] counter when the k-th hop of the sensor terminal that relays the radio signal transmitted from hops th sensor terminal receives the radio signal The updated counter value C _k = c _{3k of the k} -th hop sensor terminal is used using the value c _3k−1 and the counter value c _3k when the k-th hop sensor terminal starts the updating process of the counter value. −c _3k−1 + c _{3 (k−1) +1} is calculated by repeating the process from k = 3 to k = n (where n is an integer of 3 or more), and using n calculated, n hops A counter synchronization apparatus for a sensor terminal, comprising means for calculating a synchronized counter value Cn ′ = Cn + Vo of an eye sensor terminal.   Means for giving the time stamp t1 when the updated counter value C1 is inputted and for giving the time stamp t2 when the updated counter value C2 is inputted, 10. The device according to claim 7, which functions as the external device to which the updated counter value C 1 is input from a sensor terminal and the updated counter value C 2 is input from the second hop sensor terminal. The counter synchronizer of the sensor terminal as described in any one.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal receiving the wireless signal is received, and the second hop sensor terminal updates the counter value. Using the counter value c6 at the start of the process, and receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]) and the process of calculating the synchronized counter value C2 '= C2 + Vo of the second hop sensor terminal Synchronization program counter sensor terminal, characterized in that to perform the.   The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal that relays the radio signal receives the wireless signal, and the second hop sensor terminal updates the counter value. Using the counter value c6 at the start of the process, and receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]), and the second hop sensor terminal calculates the updated counter value C2 and then transmits a radio signal. Counter value c7, counter value c8 when the third hop sensor terminal receiving the radio signal transmitted from the second hop sensor terminal receives the radio signal, and the third hop sensor terminal The updated counter value C3 of the third hop sensor terminal calculated from C3 = c9−c8 + c7 from the counter value c9 when the counter value update process is started is used to synchronize the third hop sensor terminal. A synchronization program for a counter of a sensor terminal, which causes a computer to perform a process of calculating the counter value C3 '= C3 + Vo. The counter value c1 when the coordinator resets its own counter value and transmits the radio signal, and the first hop sensor terminal that relays the radio signal transmitted from the coordinator receives the radio signal. The updated counter calculated by C1 = c3−c2 + c1 by the first hop sensor terminal using the counter value c2 and the counter value c3 when the first hop sensor terminal starts updating the counter value. The value C1, the counter value c4 when the first hop sensor terminal calculates the updated counter value C1 and transmits a radio signal, and the radio signal transmitted from the first hop sensor terminal Counter value c5 when the second hop sensor terminal that relays the radio signal receives the wireless signal, and the second hop sensor terminal updates the counter value. Using the counter value c6 at the start of the process, and receiving the updated counter value C2 calculated by C2 = c6−c5 + c4 by the second hop sensor terminal, and the first hop sensor terminal The updated counter value C1, the time stamp t1 when the updated counter value C1 of the first hop sensor terminal is input to an external device, and the updated counter value C2 of the second hop sensor terminal And the time stamp t2 when the updated counter value C2 of the second hop sensor terminal is input to the external device, the offset value Vo = (t2−t1) × Ct− (C2−C1) (Where Ct is the reciprocal of the counter speed [count / time]), and the sensor terminal at the [k-1] hop calculates the updated counter value C _k-1 and transmits the radio signal. When Counter value c ₃ and _{(k-1) +1,} the [k-1] counter when the k-th hop of the sensor terminal that relays the radio signal transmitted from hops th sensor terminal receives the radio signal The updated counter value C _k = c _{3k of the k} -th hop sensor terminal is used using the value c _3k−1 and the counter value c _3k when the k-th hop sensor terminal starts the updating process of the counter value. −c _3k−1 + c _{3 (k−1) +1} is calculated by repeating the process from k = 3 to k = n (where n is an integer of 3 or more), and using n calculated, n hops A counter synchronization program for a sensor terminal, which causes a computer to calculate a synchronized counter value Cn ′ = Cn + Vo of an eye sensor terminal.   A process of giving the time stamp t1 when the updated counter value C1 is inputted and further giving the time stamp t2 when the updated counter value C2 is inputted; The computer also functions as the external device to which the updated counter value C1 is input from the first hop sensor terminal and the updated counter value C2 is input from the second hop sensor terminal. The counter terminal synchronization program according to any one of claims 11 to 13.

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