JP2017215712A - Sensor relay device and time stamp correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid collision of time stamps with respect to the same sensor terminal.SOLUTION: A sensor relay device comprises: a reception time detection part 3 for detecting a reception time of a packet that is received from a sensor terminal; an interval calculation part 4 for calculating an interval ΔT of reception times of packets with respect to packets that are received from the same sensor terminal; a smoothing part 5 for smoothing the interval ΔT; a time calculation part 6 for correcting a reception time of a packet received from a sensor terminal by using a smoothed interval ΔT' with respect to the sensor terminal, and calculating a reception time of sensor data included in packets received from the sensor terminal for each piece of sensor data; and a time stamp application part 7 for applying a time stamp indicating a reception time of each piece of sensor data included in a packet received from a sensor terminal to each piece of sensor data in the packet based on a calculation result of the time calculation part 6 with respect to the packet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor network system that aggregates sensor data from a sensor terminal and transfers it to a server device or the like, and in particular, a time stamp to be added to packet data in a sensor relay device that transfers packets transmitted from the sensor terminal. This is related to the correction technique.

  In an IoT (Internet of Things) society in which all devices are connected to the Internet, various sensors are connected to the network, collecting a large amount of data and analyzing the data to extract useful information for humans. Expected. Specifically, the use of data that requires real-time analysis to some extent, such as acceleration, angular acceleration, and electrocardiographic waveform, has been expanded based on recent advances in wireless technology. For example, in the example of FIG. 8, the sensor terminals 100-1 to 100 -N wirelessly transmit sensor data, and the sensor relay device 101 transmits the sensor data from the sensor terminals 100-1 to 100 -N via the network 103 to the server device. 102 is transmitted.

  In a sensor network system that collects sensor data from the sensor terminals 100-1 to 100-N, a technique for giving a time stamp to the sensor data is a very important technique for analyzing the sensor data. For this purpose, it is indispensable to accurately synchronize the time between the sensor terminals, and research on time synchronization is underway (see Non-Patent Document 1).

  In order to give the time stamp accurately, each sensor terminal 100-1 to 100-100 can be attached at the moment when the physical quantity measured by the sensor terminals 100-1 to 100-N is converted into digital data. It is best to have -N have an accurate clock. However, in this method, as shown in FIG. 9, each sensor terminal 100-1 to 100-N has a clock 104-1 to 104-N composed of elements including a very accurate crystal oscillator. There is a problem that it is indispensable and difficult to use from the viewpoint of cost (see Non-Patent Document 2).

  When the sensor terminals 100-1 to 100-N do not have an accurate clock, the sensor relay device 101 gives a time stamp to the sensor data. The sensor relay device 101 considered here is provided with a plurality of communication circuits 105-A, 105-B,..., 105-X of the wireless communication standard as shown in FIG. Each communication circuit is connected to the communication circuit 105-A of the wireless communication standard A, and the sensor terminals 100-1B to 100-NB are connected to the communication circuit 105-B of the wireless communication standard B. Sensor terminals corresponding to the respective wireless communication standards A, B,..., X are connected to 105-A, 105-B,. Considering that a time stamp is given to sensor data of these sensor terminals, a clock 107 that provides time information is necessary.

  When attaching a time stamp to sensor data using a sensor relay device, especially in the case of acceleration, angular acceleration, electrocardiogram waveform, myoelectric waveform data with a fast sampling rate, one packet transmitted from the sensor terminal There are many cases in which a plurality of data are included (see Non-Patent Document 3). In such a case, it is necessary to add a known sampling period based on the first time stamp.

For example, consider a case where the sensor relay device receives packets from the sensor terminals 100-1A, 100-NA, and 100-1B as shown in FIG. As shown in FIG. 12A, one packet 200 includes N pieces of sensor data D _{1 to} D _N , and the reception time of this packet 200 is T ₁ , and the sensor data is known at a sampling period. Is T _S , the reception times t _D1 , t _D2 , t _D3 ,..., T _DN of the first to Nth sensor data D _{1 to} D _N are as follows.
t _D1 = T ₁
t _D2 = T ₁ + T _s
t _D3 = T ₁ + 2T _s
t _DN = T ₁ + (N−1) T _s (1)

Makoto Suzuki, Shunsuke Saruwatari, Masateru Minami, Hiroyuki Morikawa, “Research Trends of Time Synchronization Technology in Wireless Sensor Networks”, Morikawa Laboratory, Research Center for Advanced Science and Technology, The University of Tokyo, No. 2008001, 2008 "Knowledge Base Knowledge Forest Group 4-5-Chapter 3 Sensor Network", IEICE, 2010, Internet <http://www.ieice-hbkb.org/files/04/04gun_05hen_03.pdf> “Sensor Network Module Evaluation Kit Application Note Android Application User Manual”, Alps Electric Co., Ltd., 2016

  As described above, when a time stamp is given to sensor data from a sensor terminal in the sensor relay device, the reception time of a plurality of sensor data included in the packet is calculated from the reception time of the packet, and the reception time is calculated. The time stamp shown is given to each sensor data.

However, when a retransmission is caused by a transmission delay or packet error, or when an interrupt is received from another process in the microcomputer of the sensor relay device, a delay occurs in the time stamp, and a time stamp collision occurs with respect to the same sensor terminal. was there. For example, when packets 201 and 202 are continuously received from one sensor terminal as in the example of FIG. 12B, the reception time T ₁ of packet 201 and the reception time T _{2 of} packet 202 are T ₂ −T. _{When 1} <(N−1) T _s , a time stamp collision occurs in the packets 201 and 202.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sensor relay device and a time stamp correction method that can avoid a time stamp collision related to the same sensor terminal.

  The sensor relay device of the present invention includes: a first communication circuit that receives a packet from a sensor terminal; a reception time detection unit that detects a reception time of the packet; and a reception time of the packet for packets received from the same sensor terminal An interval calculation unit for calculating the interval of the reception time, a smoothing unit for smoothing the interval of the reception time, and the reception time of the packet being processed received from the sensor terminal, the interval after the smoothing relating to the sensor terminal The time calculation unit that calculates the sensor data reception time included in the packet being processed for each sensor data and the time stamp indicating the reception time of each sensor data included in the packet being processed A time stamp assigning unit for attaching to each sensor data in a packet based on a calculation result of the time calculating unit, and the time stamp It is characterized in further comprising a second communication circuit for transferring the granted packets.

Further, in the configuration example of the sensor relay device of the present invention, a communication control unit that determines whether access is permitted / not permitted when communication is performed in response to an access request from a sensor terminal, and access is not permitted. A waiting time timer for measuring the waiting time until the access permission of the sensor terminal is received, and the time calculation unit is configured such that when the sensor terminal that has transmitted the packet being processed is a sensor terminal for which access is not permitted once The waiting time of the sensor terminal is subtracted from the corrected reception time of the packet being processed, and the reception time of the sensor data included in the packet being processed is determined for each sensor data using the reception time obtained by the subtraction process. It is characterized by calculating.
In addition, one configuration example of the sensor relay device of the present invention further includes a priority storage unit that stores in advance the communication priority of each sensor terminal, and the communication control unit is stored in the priority storage unit. Based on the priority information, access permission / denial is determined for the access request from the sensor terminal.
Further, in one configuration example of the sensor relay device of the present invention, the communication control unit determines whether to permit / deny access to an access request from the sensor terminal based on a size of a packet transmitted from the sensor terminal. It is characterized by doing.

  The present invention also relates to a time stamp correction method for correcting a time stamp to be added to packet data in a sensor relay device for transferring a packet transmitted from a sensor terminal, the reception time of the packet transmitted from the sensor terminal. A reception time detection step for detecting the packet, an interval calculation step for calculating an interval between the reception times of the packets received from the same sensor terminal, a smoothing step for smoothing the interval between the reception times, and a sensor terminal A time calculation step of correcting the reception time of the received packet being processed using the interval after the smoothing related to the sensor terminal, and calculating the reception time of the sensor data included in the packet being processed for each sensor data And a time stamp indicating the reception time of each sensor data included in the packet being processed And it is characterized in that it comprises a time stamping step of applying on the basis of the calculation result of the time calculation step for this packet to the sensor data in the packet.

In addition, one configuration example of the time stamp correction method of the present invention further includes a communication control step for determining whether access is permitted or not when performing communication in response to an access request from a sensor terminal, A waiting time measuring step for measuring a waiting time until the access permission of the sensor terminal is performed, and the time calculating step is a sensor terminal in which the sensor terminal that has transmitted the packet being processed is once denied access In this case, the waiting time of the sensor terminal is subtracted from the corrected reception time of the packet being processed, and the reception time of the sensor data included in the packet being processed is calculated using the reception time obtained by the subtraction process. The method includes a step of calculating each time.
Further, in one configuration example of the time stamp correction method of the present invention, the communication control step refers to a priority storage unit that stores in advance the communication priority of each sensor terminal, and is stored in the priority storage unit. The method includes a step of determining whether to permit / deny access to an access request from a sensor terminal based on priority order information.
Further, in one configuration example of the time stamp correction method of the present invention, the communication control step determines whether to permit / deny access to an access request from a sensor terminal based on a size of a packet transmitted from the sensor terminal. Including the step of performing

  According to the present invention, in the sensor relay device in which a time stamp collision may occur due to delay by providing the sensor relay device with the reception time detecting unit, the interval calculating unit, the smoothing unit, the time calculating unit, and the time stamp assigning unit. , It is possible to avoid time stamp conflicts for the same sensor terminal.

  Further, in the present invention, the sensor relay device is further provided with a communication control unit and a waiting time timer, and the time calculation unit is a sensor terminal in which the sensor terminal that transmitted the packet being processed is once denied access In this case, by subtracting the waiting time of the sensor terminal from the corrected reception time of the packet being processed, the time stamp It becomes possible to guarantee consistency.

  In the present invention, the sensor relay device further includes a priority order storage unit, and the communication control unit accesses the access request from the sensor terminal based on the priority order information stored in the priority order storage unit. By determining permission / non-permission, communication priority is increased for sensor terminals that transmit sensor data that requires high-speed sampling, and conversely, sensor data with a low communication frequency and a small amount of information is transmitted. Sensor terminals can be handled by lowering the communication priority.

  Further, in the present invention, the communication control unit determines whether access is permitted or not for the access request from the sensor terminal based on the size of the packet transmitted from the sensor terminal, so that real-time property is required. It is possible to preferentially receive short data of data packets.

It is a block diagram which shows the structure of the sensor relay apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the sensor relay apparatus which concerns on the 1st Embodiment of this invention. It is a histogram of the interval of reception time. It is a block diagram which shows the structure of the sensor relay apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart explaining operation | movement of the sensor relay apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the sensor relay apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the sensor relay apparatus which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the structure of the conventional sensor network system. It is a block diagram which shows the structure of a sensor network system in case each sensor terminal has a timepiece. It is a block diagram which shows the structure of a sensor network system in case a sensor relay apparatus has a timepiece. It is a figure explaining the example which receives the packet from a sensor terminal in a sensor relay apparatus. It is a figure explaining the conventional problem.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the sensor relay device according to the first embodiment of the present invention. The sensor relay device is the same as the communication circuits 1-A and 1-B for performing wireless communication with the sensor terminal, the clock 2, and the reception time detection unit 3 that detects the reception time of the packet received from the sensor terminal. An interval calculation unit 4 that calculates an interval ΔT of packet reception times for a packet received from the sensor terminal, a smoothing unit 5 that smoothes the interval ΔT, and a reception time of the packet received from the sensor terminal are related to this sensor terminal. It is corrected using the interval ΔT ′ after smoothing, and is included in the packet received from the sensor terminal, and the time calculation unit 6 that calculates the reception time of the sensor data included in the packet received from the sensor terminal for each sensor data. A time stamp indicating the reception time of each sensor data is assigned to each sensor data in the packet based on the calculation result of the time calculation unit 6 regarding this packet. It comprises a time stamp assigning unit 7 and a communication circuit 8 for transferring a packet to which a time stamp is assigned.

  FIG. 2 is a flowchart for explaining the operation of the sensor relay device of this embodiment. The sensor relay device is provided with a plurality of communication circuits 1 having different wireless communication standards with the sensor terminal. In the example of FIG. 1, the communication circuit 1-A of the wireless communication standard A and the communication of the wireless communication standard B are used. Only circuit 1-B is shown.

  The reception time detection unit 3 of the sensor relay device detects the reception time of the packet received from the corresponding sensor terminal by each of the communication circuits 1-A and 1-B based on the time information obtained from the clock 2 (see FIG. 2 step S100).

  The interval calculation unit 4 calculates, for each sensor terminal, an interval ΔT that is a difference value between the reception time of a packet and the reception time of the next packet for packets received from the same sensor terminal (step S101 in FIG. 2). ). Needless to say, from which sensor terminal the received packet is transmitted can be identified, for example, based on the source address given to the header of the packet.

  The smoothing unit 5 smoothes the interval ΔT calculated by the interval calculating unit 4 for each sensor terminal (step S102 in FIG. 2). This smoothing process in the time domain corresponds to a low-pass filter process in the frequency domain.

  The time calculation unit 6 corrects the reception time of the packet received from the sensor terminal using the interval ΔT ′ after the smoothing process related to the sensor terminal so that the time stamp does not collide (step S103 in FIG. 2). .

If the reception time of the packet received from the sensor terminal is T _i−1 and the reception time of the next packet received from the sensor terminal is T _i , the interval ΔT is ΔT = T _i −T _i−1 . Appearance of interval ΔT when N pieces of sensor data (acceleration, angular acceleration, electrocardiogram waveform, electromyogram waveform, etc. measured in the sensor terminal are converted into digital data) are included in one packet The frequency draws a distribution having a spread centering on N · T _S where the sampling period T _{S of} sensor data is N (FIG. 3).

Here, for the same sensor terminal, when the interval ΔT is (N−1) T _S or more and (N + 1) T _S or less, it is possible to assign time stamps to each data without collision. However, if it falls outside this range, a time stamp collision will occur or a collision will occur in the next sample.

Therefore, in this embodiment, smoothing processing (low-pass filter processing in the frequency domain) is performed on the packet reception time interval ΔT, and the packet reception time is corrected based on the interval ΔT ′ after the smoothing processing. To do. Specifically, assuming that the reception time of the _first received packet is T ₁ , and the reception time of the _second received packet is T ₂ , the reception time interval ΔT ₁ is as shown in Equation (2). When the interval ΔT _{1 ′ obtained} by smoothing the interval ΔT ₁ is used, the corrected reception times T ₁ ′ and T ₂ ′ are expressed by the equations (3) and (4).
ΔT ₁ = T ₂ −T ₁ (2)
T ₁ '= T ₁ (3)
T ₂ '= ΔT ₁ ' + T ₁ '(4)

Similarly, assuming that the reception time of the _third received packet is T ₃ , the reception time interval ΔT ₂ is as shown in Equation (5). By using the interval ΔT ₂ ′ obtained by smoothing this interval ΔT ₂ , The corrected reception time T ₃ ′ is as shown in Equation (6).
ΔT ₂ = T ₃ −T ₂ (5)
T ₃ '= ΔT ₂ ' + T ₂ '(6)

Similarly, assuming that the reception time of the _fourth received packet is T ₄ , the reception time interval ΔT ₃ is as shown in Equation (7). By using the interval ΔT ₃ ′ obtained by smoothing this interval ΔT ₃ , The corrected reception time T ₄ ′ is as shown in Expression (8).
ΔT ₃ = T ₄ −T ₃ (7)
T ₄ '= ΔT ₃ ' + T ₃ '(8)

Generalizing the above, if the reception time of the (i−1) -th received packet is T _i−1 and the reception time of the _i- th received packet is T _i , the reception time interval ΔT _i-1 can be expressed as is as 9), 'the use of, receiving time T _i of the corrected' interval [Delta] T _i-1 of this interval [Delta] T _i-1 obtained by smoothing is as equation (10).
ΔT _i-1 = T _i -T _i-1 (9)
T _i '= ΔT _i-1 ' + T _i-1 '(10)

As an example, consider a case where a moving average filter is used as the smoothing process. According to this method, as shown in the appearance frequency of FIG. 3, the distribution after the smoothing of the interval ΔT is distributed around N · T _S by the central limit theorem. That is, it is very effective because a value that may cause a collision of the time stamp is less likely to occur. In FIG. 3, 30 and 31 indicate distributions before smoothing, and 32 indicates a distribution after smoothing.

The time calculation unit 6 calculates the reception time of the sensor data included in the packet for each sensor data from the reception time T _i ′ of the packet corrected in step S103 and the known sampling period T _S of the sensor data included in the packet. Calculate (step S104 in FIG. 2). If it contains N sensors data in one packet, the reception time t _D1 of the sensor data from the first to _{N-th, t D2, t D3, ···} , t DN the following formula become that way.
t _D1 = T _i '
t _D2 = T _i '+ T _s
t _D3 = T _i '+ 2T _s
t _DN = T _i ′ + (N−1) T _s (11)

The time stamp assigning unit 7 assigns a time stamp indicating the reception time of each sensor data included in the packet received from the sensor terminal to each sensor data in the packet based on the calculation result of the time calculating unit 6 regarding the packet. (FIG. 2, step S105).
The interval calculation unit 4, the smoothing unit 5, the time calculation unit 6, and the time stamp assigning unit 7 perform the above processing independently for each sensor terminal.

Then, the communication circuit 8 transfers the packet with the time stamp to the transmission destination (for example, server device) via the network (step S106 in FIG. 2).
As described above, according to the present embodiment, it is possible to avoid time stamp collisions related to the same sensor terminal in a sensor relay device in which time stamp collisions may occur due to delay.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the sensor relay device according to the second embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. The sensor relay device of the present embodiment includes communication circuits 1-A, 1-B, a clock 2, a reception time detection unit 3, an interval calculation unit 4, a smoothing unit 5, a time calculation unit 6a, The communication control unit 9 that determines whether access is permitted or not permitted when performing communication in response to an access request from the time stamp assigning unit 7, the communication circuit 8, and the sensor terminal, and the sensor terminal that is not permitted access And a waiting time timer 10 for measuring a waiting time until access is permitted.

  In this embodiment, in addition to the technique of the first embodiment, access request based connection control is applied to a plurality of sensor terminals of the same wireless system, and the value of the waiting time timer 10 is subtracted. To ensure time stamp consistency.

FIG. 5 is a flowchart for explaining the operation of the sensor relay device of this embodiment. Each sensor terminal connected to the sensor relay device of the present embodiment transmits an access request when transmitting a packet including sensor data.
Although the packet may be transmitted simultaneously with the access request, the packet transmission may be regarded as the access request transmission.

  When there is an access request from the sensor terminal (YES in step S107 in FIG. 5), the communication control unit 9 of the sensor relay device determines whether to permit access from the sensor terminal (step S108 in FIG. 5). Since the operation for permitting access from the sensor terminal is as described in the first embodiment, the description thereof is omitted.

  For example, when there is an access request from a plurality of sensor terminals of the same wireless method, the communication control unit 9 permits access to one of the sensor terminals and denies access from other sensor terminals. To do. The communication control unit 9 wirelessly transmits a packet indicating access permission to the sensor terminal determined to be permitted to access, and wirelessly transmits a packet indicating access permission to the sensor terminal determined to be access not permitted. The sensor terminal that has received the notification of unauthorized access transmits an access request again.

  When there is a sensor terminal for which access is not permitted, the waiting time timer 10 measures the waiting time until access to this sensor terminal is permitted (step S109 in FIG. 5). The waiting time timer 10 performs such waiting time measurement for each sensor terminal for which access is not permitted. In the case where the determination of access disapproval is repeated for one sensor terminal, the waiting time from the access request first transmitted by this sensor terminal until the access request is finally permitted is measured. .

  The processing in steps S100 to S102 is as described in the first embodiment. Similar to the first embodiment, the time calculation unit 6a corrects the reception time of the packet received from the sensor terminal by using the interval ΔT ′ after the smoothing process related to the sensor terminal (step S103 in FIG. 5). In addition, when the sensor terminal is a sensor terminal whose access is not permitted once and the waiting time is measured by the waiting time timer 10 (YES in step S110 in FIG. 5), from the reception time corrected in step S103 The waiting time is subtracted (step S111 in FIG. 5).

If the reception time of the packet modified in step S103 is T _i ′ and the waiting time is Wait _i , the reception time T _i ″ after subtraction is as follows.
T _i ″ = T _i ′ −Wait _i (12)

The time calculation unit 6a initializes the waiting time Wait _i of the sensor terminal subjected to the subtraction processing of the reception time in step S111 among the waiting times being measured or held by the waiting time timer 10 to 0 (FIG. 5 step S112).

Then, when the sensor terminal that transmitted the packet being processed is a sensor terminal for which access is not permitted, the time calculation unit 6a performs subtraction processing instead of the packet reception time T _i ′ corrected in step S103. The reception time of the sensor data included in the packet is calculated for each sensor data using the received time T _i ″ (step S104 in FIG. 5). The processing at this time is expressed by the following equation (11): 13).
t _D1 = T _i ″
t _D2 = T _i "+ T _s
t _D3 = T _i "+ 2T _s
t _DN = T _i ″ + (N−1) T _s (13)

  Other processes are as described in the first embodiment. According to the present embodiment, it is possible to guarantee time stamp consistency by introducing access control in a situation where a plurality of sensor terminals adopting the same wireless method exist in the same space. . In addition, since only the communication control unit 9 and the waiting time timer 10 need to be added in the present embodiment, a large amount of hardware resources are not required and it is economical.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of the sensor relay device according to the third embodiment of the present invention. The same components as those in FIGS. 1 and 4 are denoted by the same reference numerals. The sensor relay device of the present embodiment includes communication circuits 1-A, 1-B, a clock 2, a reception time detection unit 3, an interval calculation unit 4, a smoothing unit 5, a time calculation unit 6a, The time stamp adding unit 7, the communication circuit 8, the communication control unit 9, the waiting time timer 10, and a priority storage unit 11 that stores in advance the communication priority of each sensor terminal.

  In this embodiment, in the method of the second embodiment, whether access from the sensor terminal to the sensor relay device is permitted or not is determined based on the priority order of each sensor terminal. Since the processing flow in this embodiment is the same as that in the second embodiment, description will be made using the reference numerals in FIG.

  As described in the second embodiment, when there is an access request from the sensor terminal, the communication control unit 9 of the sensor relay device determines whether to permit access from the sensor terminal (FIG. 5). Step S108), for example, when there are access requests from a plurality of sensor terminals of the same wireless system, access is permitted to one of the sensor terminals, and access from other sensor terminals is not permitted.

Here, in this embodiment, communication priority information of each sensor terminal is registered in advance in the priority storage unit 11, and the communication control unit 9 requests access from a plurality of sensor terminals of the same wireless system. If there is, access is permitted to the sensor terminal with the highest priority among these sensor terminals, and access from other sensor terminals is not permitted.
Other processes are as described in the second embodiment.

  Thus, in this embodiment, communication priority is increased for sensor terminals that transmit sensor data that requires high-speed sampling, such as acceleration, angular acceleration, electrocardiogram waveform, and electromyogram waveform, and conversely, communication such as temperature is performed. A sensor terminal that transmits sensor data that is low in frequency and does not have a large amount of information can be handled by lowering the communication priority.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the sensor relay device according to the fourth embodiment of the present invention. The same components as those in FIGS. 1, 4, and 6 are denoted by the same reference numerals. The sensor relay device of the present embodiment includes communication circuits 1-A, 1-B, a clock 2, a reception time detection unit 3, an interval calculation unit 4, a smoothing unit 5, a time calculation unit 6a, The time stamp adding unit 7, the communication circuit 8, the communication control unit 9 a, and a waiting time timer 10 are included.

  In this embodiment, in the technique of the second embodiment, whether access from the sensor terminal to the sensor relay device is permitted or not is determined based on the packet size. Since the processing flow in this embodiment is the same as that in the second embodiment, description will be made using the reference numerals in FIG.

  Similar to the second embodiment, the communication control unit 9a of the sensor relay device determines whether or not to permit access from the sensor terminal when there is an access request from the sensor terminal (step S108 in FIG. 5). ). In this embodiment, access permission / denial is determined based on the packet size. Specifically, when there is an access request from a plurality of sensor terminals of the same wireless method, the communication control unit 9a permits access to the sensor terminal having the shortest packet size among these sensor terminals, Disallow access from other sensor terminals.

In the case of the present embodiment, since it is necessary to detect the size of the packet, packets from all sensor terminals are transmitted to the corresponding communication circuits 1-A, 1- 1 of the corresponding wireless communication standards regardless of whether access is permitted or not. Receive at B. Then, only the packet for which access is permitted by the communication control unit 9a is valid, and the reception time detection unit 3 detects the reception time of this packet (step S100 in FIG. 5), and the sensor terminal whose access is not permitted. Packets from are discarded. The sensor terminal that has received the notification of access disapproval from the communication control unit 9a transmits the access request and the packet again.
Other processes are as described in the second embodiment.

  In this embodiment, when the packet size is short, the packet reception is performed preferentially. Conversely, when the packet size is long, the packet reception priority is lowered, so that the data packet requiring real-time property is short. Since data can be received preferentially, it is useful in an environment where data that requires real-time characteristics and data that is suitable for output after being stored once are mixed.

  Among the configurations of the sensor relay devices described in the first to fourth embodiments, at least the clock 2, the reception time detection unit 3, the interval calculation unit 4, the smoothing unit 5, the time calculation units 6 and 6a, and the time stamp assignment The unit 7, the communication control units 9 and 9a, the waiting time timer 10 and the priority order storage unit 11 are based on a computer having a CPU (Central Processing Unit), a storage device and an interface, and a program for controlling these hardware resources. Can be realized. The CPU executes the processes described in the first to fourth embodiments in accordance with a program stored in the storage device.

  The present invention can be applied to a sensor network system that collects sensor data from a sensor terminal.

  DESCRIPTION OF SYMBOLS 1-A, 1-B, 8 ... Communication circuit, 2 ... Clock, 3 ... Reception time detection part, 4 ... Interval calculation part, 5 ... Smoothing part, 6, 6a ... Time calculation part, 7 ... Time stamp provision part , 9, 9a ... communication control unit, 10 ... waiting time timer, 11 ... priority storage unit.

Claims (8)

A first communication circuit for receiving a packet from the sensor terminal;
A reception time detector for detecting the reception time of the packet;
An interval calculation unit that calculates an interval of reception times of the packets for packets received from the same sensor terminal;
A smoothing unit that smoothes the interval between the reception times;
The reception time of the packet being processed received from the sensor terminal is corrected using the interval after the smoothing relating to the sensor terminal, and the reception time of the sensor data included in the packet being processed is calculated for each sensor data. A time calculation unit;
A time stamp giving unit for giving a time stamp indicating a reception time of each sensor data included in the packet being processed to each sensor data in the packet based on a calculation result of the time calculating unit regarding the packet;
And a second communication circuit for transferring the packet with the time stamp. The sensor relay device according to claim 1,
Furthermore, when performing communication in response to an access request from the sensor terminal, a communication control unit that determines whether access is permitted or not,
A waiting time timer that measures the waiting time until access permission of the sensor terminal that has been denied access,
When the sensor terminal that has transmitted the packet being processed is a sensor terminal that has been denied access, the time calculation unit determines the waiting time of the sensor terminal from the corrected reception time of the packet being processed. A sensor relay device that calculates the reception time of the sensor data included in the packet being processed for each sensor data using the reception time obtained by subtracting. The sensor relay device according to claim 2,
Furthermore, a priority storage unit that stores in advance the communication priority of each sensor terminal,
The sensor control apparatus, wherein the communication control unit makes an access permission / non-permission determination for an access request from a sensor terminal based on priority information stored in the priority storage unit. The sensor relay device according to claim 2,
The communication control unit determines whether access is permitted or not for an access request from a sensor terminal based on a size of a packet transmitted from the sensor terminal. In a sensor relay device for transferring a packet transmitted from a sensor terminal, a time stamp correction method for correcting a time stamp to be added to packet data,
A reception time detection step of detecting a reception time of a packet transmitted from the sensor terminal;
An interval calculation step for calculating an interval of reception times of the packets for packets received from the same sensor terminal;
A smoothing step of smoothing the interval of the reception times;
The reception time of the packet being processed received from the sensor terminal is corrected using the interval after the smoothing relating to the sensor terminal, and the reception time of the sensor data included in the packet being processed is calculated for each sensor data. A time calculation step;
Including a time stamp giving step of giving a time stamp indicating a reception time of each sensor data included in the packet being processed to each sensor data in the packet based on a calculation result of the time calculating step regarding the packet. A characteristic time stamp correction method. The time stamp correction method according to claim 5,
Furthermore, when performing communication in response to an access request from the sensor terminal, a communication control step for determining access permission / denial;
A waiting time measuring step for measuring a waiting time until the access permission of the sensor terminal that is not permitted to be accessed,
In the time calculation step, when the sensor terminal that has transmitted the packet being processed is a sensor terminal that is once denied access, the waiting time of the sensor terminal is determined from the corrected reception time of the packet being processed. And a step of calculating for each sensor data the reception time of the sensor data included in the packet being processed, using the reception time after subtraction. The time stamp correction method according to claim 6,
The communication control step refers to a priority storage unit that stores the communication priority of each sensor terminal in advance, and responds to an access request from the sensor terminal based on the priority information stored in the priority storage unit. A time stamp correction method comprising a step of judging whether access is permitted or not. The time stamp correction method according to claim 6,
The communication control step includes a step of determining whether access is permitted or not for an access request from a sensor terminal based on a size of a packet transmitted from the sensor terminal.

Images