Abstract:
A sensor value acquiring method employed in a computer, comprising:
       acquiring a sensor value obtained by a sensor included in each terminal from the terminals; storing the acquired sensor value along with an identifier used to identify each terminal; differentiating the stored sensor values, each of the stored sensor value corresponding to a different identifier and obtaining differences through the differentiating; extracting identifiers corresponding to the differences each of which is equal to or smaller than a threshold value; instructing at least one of the terminals corresponding to the extracted identifier to acquire a corresponding sensor value; and transmitting an instruction for extending a sensor value acquisition interval to the terminals which are other than the at least of terminals corresponding to the extracted identifier.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2011-061761, filed on Mar. 18, 2011, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a sensor value acquiring method, a sensor control apparatus, a sensor control method, a sensor control medium, and an acquisition interval control medium. 
       BACKGROUND 
       [0003]    In general, a sensor-mounted terminal which includes a sensor such as a temperature sensor, a humidity sensor, or an air pressure sensor disposed therein and which has a communication function has been used. Using such a sensor-mounted terminal, a sensor value obtained by a sensor at a predetermined interval is transmitted to a center server connected to the sensor-mounted terminal through communication network. An administrator who manages the center server recognizes states of areas around such terminals in accordance with such sensor values supplied from the terminals. 
         [0004]    As described above, since a sensor-mounted terminal uses electric power for operating sensors and electric power for executing communications, a considerably larger amount of electric power is consumed when compared with a communication terminal which does not include a sensor or a sensor which does not have a communication function. 
         [0005]    In recent years, a technique of reducing power consumption of such a sensor-mounted terminal has been disclosed. For example, the following technique has been used: A portable terminal which operates using a battery is installed in a certain region such that a user can reach the terminal and another portable terminal is installed in another region such that the user may not reach the terminal. In this state, when output values of two sensors are equal to or smaller than a predetermined value per a predetermined period of time, the terminals enter a power-off mode in a general technique. 
       SUMMARY 
       [0006]    According to an aspect of the invention, a method includes, acquiring a sensor value obtained by a sensor included in each terminal from the terminals; storing the acquired sensor value along with an identifier used to identify each terminal; differentiating the stored sensor values, each of the stored sensor value corresponding to a different identifier and obtaining differences through the differentiating; extracting identifiers corresponding to the differences each of which is equal to or smaller than a threshold value; instructing at least one of the terminals corresponding to the extracted identifier to acquire a corresponding sensor value; and transmitting an instruction for extending a sensor value acquisition interval to the terminals which are other than the at least of terminals corresponding to the extracted identifier. 
         [0007]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0008]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a diagram illustrating an entire configuration of a system according to a first embodiment. 
           [0010]      FIG. 2  is a block diagram illustrating a configuration of a server according to the first embodiment. 
           [0011]      FIG. 3  is a diagram illustrating information stored in a temperature data table. 
           [0012]      FIG. 4  is a block diagram illustrating a configuration of a sensor wireless terminal according to the first embodiment. 
           [0013]      FIG. 5  is a flowchart illustrating a process executed by the server according to the first embodiment. 
           [0014]      FIG. 6  is a flowchart illustrating a process executed by the sensor wireless terminal according to the first embodiment. 
           [0015]      FIG. 7A  is a sequence diagram illustrating a process executed by the system according to the first embodiment. 
           [0016]      FIG. 7B  is a sequence diagram illustrating the process executed by the system according to the first embodiment. 
           [0017]      FIG. 7C  is a sequence diagram illustrating the process executed by the system according to the first embodiment. 
           [0018]      FIG. 8  is a sequence diagram illustrating a process executed by a system according to a second embodiment. 
           [0019]      FIG. 9  is a diagram illustrating grouping; 
           [0020]      FIG. 10  is a diagram illustrating grouping according to access points. 
           [0021]      FIG. 11  is a diagram illustrating a hardware configuration of a computer which executes a server-side sensor control program. 
           [0022]      FIG. 12  is a diagram illustrating a hardware configuration of a computer which executes a terminal-side sensor control program. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    When power consumption is to be reduced using the same types of sensors, the reduction of the power consumption is limited for each terminal. Furthermore, since the same types of two sensors are mounted on the terminal, high cost is a matter of concern. 
         [0024]    Hereinafter, embodiments of a sensor value acquiring method, a sensor control apparatus, a sensor control method, a sensor control medium, and an acquisition interval control medium will be described in detail with reference to the accompanying drawings. The embodiments discussed herein, each of a sensor wireless terminal includes sensor-mounted mobile node which communicates plural mobile stations by hand over. 
       First Embodiment 
       [0025]    Entire Configuration 
         [0026]      FIG. 1  is a diagram illustrating an entire configuration of a system according to a first embodiment. As illustrated in  FIG. 1 , in this system, a server  10  and a sensor wireless terminal A are connected to each other through wireless communication, and similarly, the server  10  and a sensor wireless terminal B are connected to each other through a wireless communication. Note that the number of the apparatuses and the communication method illustrated in  FIG. 1  are merely examples and the embodiment is not limited to these. 
         [0027]    Each of the sensor wireless terminals A and B includes sensors such as a temperature sensor, a humidity sensor, and an acceleration sensor. Furthermore, each of the sensor wireless terminals A and B has a WLAN (Wireless Local Area Network) function such as a Wi-Fi (Wireless Fidelity) function. Each of the sensor wireless terminals A and B executes sensing using the sensors at a predetermined interval and transmits sensor values obtained through the sensing to the server  10  at a predetermined interval. 
         [0028]    Furthermore, the sensor wireless terminals A and B are installed in the same space or held by persons in the same space. Examples of the space include a data center, a classroom, a theater, and a train. Moreover, other examples of the space include a range in which wireless communication can be performed using a single access point, that is, a region which is managed by a single access point. 
         [0029]    The server  10  has a function as an access point for a wireless communication and receives the sensor values from the sensor wireless terminals A and B at a predetermined interval. The sensor values obtained by the server  10  are used by an administrator and the like. For example, when the server  10  receives temperature information, air conditioning is performed in accordance with the temperature information. 
         [0030]    The server  10  stores sensor values obtained from sensor wireless terminals in a table along with identifiers used to identify the sensor wireless terminals. Subsequently, the server  10  differentiates the stored sensor values having the different identifiers with one another and extracts identifiers having a difference which is equal to or smaller than a threshold value. Thereafter, the server  10  instructs at least one of the sensor wireless terminals having the extracted identifiers to obtain a sensor value and instructs the other of the sensor wireless terminals having the extracted identifiers to extend a sensor-value acquisition interval. 
         [0031]    As described above, when a difference between sensor values obtained from wireless communication terminals having the same type of sensor is small, the server  10  transmits an instruction for obtaining a sensor value to one of the sensor wireless terminals and transmits an instruction for extending a sensing interval to the other of the sensor wireless terminals. As a result, the server  10  may normally obtain a sensor value from one of the sensor wireless terminals while suppressing power consumption of the other of the sensor wireless terminals corresponding to the extended sensing interval. Accordingly, electric power saving is realized in a unit of a group of terminals. 
         [0032]    Configuration of Apparatus 
         [0033]    Next, the server  10  and the sensor wireless terminals A and B will be described in detail using concrete examples. Here, a configuration of the server  10 , configurations of the sensor wireless terminals A and B, processing flows, and advantages will be described. Note that, in this embodiment, a case where each of the sensor wireless terminals A and B includes a temperature sensor and transmits sensed temperature information to the server  10  will be described. Furthermore, since the sensor wireless terminals A and B have the same configuration, the sensor wireless terminals A and B are collectively referred to as a sensor wireless terminal  30  hereinafter. 
         [0034]    Configuration of Server 
         [0035]      FIG. 2  is a block diagram illustrating a configuration of the server  10  according to the first embodiment. As illustrated in  FIG. 2 , the server  10  includes a WLAN transmitter/receiver  11 , a temperature data table  12 , a data receiver  13 , a data comparator  14 , a reference data determination device  15 , a control signal generator  16 , an extra-interval determination device  17 , a command generator  18 , and a command transmitter  19 . 
         [0036]    The WLAN transmitter/receiver  11  serves as a communication interface which connects the sensor wireless terminals A and B to a wireless communication. For example, the WLAN transmitter/receiver  11  establishes a wireless communication using the Wi-Fi, for example, between the sensor wireless terminals A and B and executes transmission and reception of data between the sensor wireless terminals A and B. 
         [0037]    The temperature data table  12  stores temperature information obtained from the sensor wireless terminals A and B.  FIG. 3  is a diagram illustrating information stored in the temperature data table  12 . As illustrated in  FIG. 3 , the temperature data table  12  stores an “ID”, a “terminal name”, “temperature data (° C.)”, “sensor control”, and an “extra acquisition interval” which are associated with one another. Note that the information is stored by the data receiver  13  in the temperature data table  12  which will be described hereinafter. Furthermore, the information illustrated in  FIG. 3  is merely examples, and the information is not limited to this and may be arbitrarily set and changed. For example, the temperature data table  12  may store information used for communication such as IP (Internet Protocol) addresses of the sensor wireless terminals A and B. 
         [0038]    The stored “ID” which is an identifier used to identify a sensor wireless terminal  30  may be assigned when the WLAN transmitter/receiver  11  establishes a wireless communication or may be set in advance. The “terminal name” representing a name of a device specifying a sensor wireless terminal  30  may be obtained by the WLAN transmitter/receiver  11  through a wireless communication or may be obtained in advance. The “temperature data (° C.)” representing a sensor value sensed by a sensor wireless terminal  30  is stored by the data receiver  13  or the like which will be described hereinafter. The “sensor control” representing a sensing instruction supplied to a sensor wireless terminal  30  is stored by the command generator  18  or the like. The “extra acquisition interval” which represents a period of time in which a sensing interval is extended and which is supplied to a sensor wireless terminal  30  is stored by the command generator  18  which will be described hereinafter or the like. 
         [0039]    In a case of the first row in  FIG. 3 , temperature data of “34° C.” is obtained from the sensor wireless terminal A having an ID of  100  assigned thereto, an “enable signal” is supplied as sensor control to the sensor wireless terminal A, and information representing “extra acquisition interval=none” is supplied to the sensor wireless terminal A. In a case of the second row in  FIG. 3 , temperature data of “32° C.” is obtained from the sensor wireless terminal B having an ID of  110  assigned thereto, a “disable signal” is supplied as sensor control to the sensor wireless terminal B, and information representing “extra acquisition interval=5 seconds” is supplied to the sensor wireless terminal B. 
         [0040]    The data receiver  13  receives sensor values from the sensor wireless terminals A and B through the WLAN transmitter/receiver  11 . For example, the data receiver  13  receives a packet including temperature data added thereto from each of the sensor wireless terminals A and B. Then the data receiver  13  extracts the ID from a header or the like of the packet, associates the extracted ID with the received temperature data, and stores the ID and the temperature data in the temperature data table  12 . 
         [0041]    The data comparator  14  performs, when the temperature data table  12  is updated, comparison of temperature data stored in the temperature data table  12 . For example, the data comparator  14  refers to the temperature data table  12  so as to extract temperature data (SA) of the sensor wireless terminal A and temperature data (SB) of the sensor wireless terminal B. Thereafter, the data comparator  14  calculates a difference between the temperature data SA and the temperature data SB and determines whether the calculated difference is smaller than a threshold value such as 1° C. 
         [0042]    Subsequently, when it is determined that the calculated difference is smaller than the threshold value, the data comparator  14  determines that an acquisition interval of the sensor wireless terminal A is maintained and outputs the determination to the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17 . Furthermore, when it is determined that the calculated difference is equal to or larger than the threshold value, the data comparator  14  determines that the acquisition interval of the sensor wireless terminal A and an acquisition interval of the sensor wireless terminal B are initialized and outputs the determination to the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17 . Note that a determination as to whether the acquisition interval of the sensor wireless terminal A or the acquisition interval of the sensor wireless terminal B is maintained when the difference calculated by the data comparator  14  is smaller than the threshold value may be arbitrarily made by the user. 
         [0043]    The reference data determination device  15  determines a reference destination of a sensing application which operates in each of the sensor wireless terminals A and B. It is assumed that the reference data determination device  15  receives a notification representing that the acquisition interval of the sensor wireless terminal A is to be maintained from the data comparator  14 . In this case, the reference data determination device  15  outputs information representing that the sensor wireless terminal A refers to the temperature data of itself to the command generator  18 . Furthermore, the reference data determination device  15  outputs information representing that the sensor wireless terminal B refers to the temperature data of the other terminal to the command generator  18 . 
         [0044]    On the other hand, it is assumed that the reference data determination device  15  receives a notification representing that the acquisition intervals of the sensor wireless terminals A and B are to be initialized from the data comparator  14 . In this case, the reference data determination device  15  outputs information representing that the sensor wireless terminal A refers to the temperature data of itself to the command generator  18 . Furthermore, the reference data determination device  15  outputs information representing that the sensor wireless terminal B also refers to the temperature data of itself to the command generator  18 . 
         [0045]    The control signal generator  16  generates a control signal representing whether each of the sensor wireless terminals A and B is caused to perform sensing. In the example described above, it is assumed that the reference data determination device  16  receives the notification representing that the acquisition interval of the sensor wireless terminal A is to be maintained from the data comparator  14 . In this case, the control signal generator  16  generates an “enable signal” representing permission of sensing for the sensor wireless terminal A and outputs the “enable signal” to the command generator  18 . Furthermore, the control signal generator  16  generates a “disable signal” representing inhibition of sensing for the sensor wireless terminal B and outputs an instruction for generating a command to the command generator  18 . 
         [0046]    The extra-interval determination device  17  determines extra intervals of sensing performed by the sensor wireless terminals A and B. In the example described above, it is assumed that the extra-interval determination device  17  receives the notification representing that the acquisition interval of the sensor wireless terminal A is to be maintained from the data comparator  14 . In this case, the extra-interval determination device  17  outputs information representing that it is determined that the sensor wireless terminal A performs sensing with an initial value, that is, without extension of the interval to the command generator  18 . Furthermore, the extra-interval determination device  17  outputs information representing that it is determined that the sensing interval of the sensor wireless terminal B is extended by 5 seconds to the command generator  18 . 
         [0047]    In this case, it is assumed that the extra-interval determination device  17  consecutively receives a notification representing that the acquisition interval of the sensor wireless terminal A is maintained from the data comparator  14 . In this case, the extra-interval determination device  17  outputs information representing that it is determined that the sensor wireless terminal A performs sensing with the initial value to the command generator  18 . Furthermore, the extra-interval determination device  17  outputs information representing that it is determined that the sensing interval of the sensor wireless terminal B is further extended by 10 seconds to the command generator  18 . 
         [0048]    The command generator  18  generates a command in accordance with the commands and the instructions supplied from the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17 . In the example described above, the command generator  18  generates a control command A representing “reference temperature data=temperature data SA of itself, control signal=enable signal, and extra acquisition interval=none” for the sensor wireless terminal A. Furthermore, the command generator  18  generates a control command B representing “reference temperature data=temperature data SA of the other sensor wireless terminal, control signal=disable signal, and extra acquisition interval=5 seconds” for the sensor wireless terminal B. Note that the command generator  18  transmits the control commands A and B and the transmission destinations to the command transmitter  19 . 
         [0049]    The command transmitter  19  transmits the control commands A and B generated by the command generator  18  to the sensor wireless terminals A and B, respectively, through the WLAN transmitter/receiver  11 . For example, the command transmitter  19  obtains “IDs” and “terminal names” from the command generator  18  as the transmission destination. The command transmitter  19  specifies an IP address from the temperature data table  12  or the like using the information as a key and transmits a corresponding control command to the specified IP address. 
         [0050]    Configuration of Sensor Wireless Terminal 
         [0051]      FIG. 4  is a block diagram illustrating a configuration of the sensor wireless terminal  30  according to the first embodiment. As illustrated in  FIG. 4 , the sensor wireless terminal  30  includes a WLAN transmitter/receiver  31 , a temperature sensor  32 , a timer  33 , a command receiver  34 , a command interpreter  35 , a measurement device  36 , a sensing application  37 , a switch  38 , and a data transmitter  39 . 
         [0052]    The WLAN transmitter/receiver  31  is a communication interface which connects the server  10  and a wireless communication to each other. For example, the WLAN transmitter/receiver  31  establishes a wireless communication using the Wi-Fi, for example, with the server  10  or another sensor wireless terminal and executes transmission and reception of data using the established communication. 
         [0053]    The temperature sensor  32  serving as a sensing device detects a temperature all the time or at a predetermined interval to be stored in a data buffer  36   c  which will be described hereinafter. The timer  33  controls a sensing interval of the temperature sensor  32 . The command receiver  34  receives a control command from the server  10  through the WLAN transmitter/receiver  31  and outputs the received control command to the command interpreter  35 . 
         [0054]    The command interpreter  35  analyzes the control command supplied from the command receiver  34  and instructs a controller to perform a process. In the example described above, it is assumed that the command receiver  34  receives the control command A representing “reference temperature data=temperature data SA of itself, control signal=enable signal, and extra acquisition interval=none”. 
         [0055]    In this case, the command interpreter  35  instructs the switch  38  to refer to the “sensor value of itself” in accordance with the information representing “the temperature data SA of it” extracted from the control command A. Furthermore, the command interpreter  35  outputs the “enable signal” extracted from the control command A to a sensor setting device  36   a . Moreover, the command interpreter  35  outputs the information representing “extra acquisition interval=none” extracted from the control command A to a sensor interval setting device  36   b.    
         [0056]    Furthermore, it is assumed that the command receiver  34  receives the control command B representing “reference temperature data=temperature data SA of the other terminal, control signal=disable signal, and extra acquisition interval=5 seconds”. 
         [0057]    In this case, the command interpreter  35  instructs the switch  38  to refer to the “temperature data SA sensed by the sensor wireless terminal A” in accordance with the information representing “temperature data SA of the other terminal” extracted from the control command B. Furthermore, the command interpreter  35  outputs the “disable signal” extracted from the control command B to the sensor setting device  36   a . Moreover, the command interpreter  35  outputs the information representing that “extra acquisition interval=5 seconds” extracted from the control command B to the sensor interval setting device  36   b.    
         [0058]    The measurement device  36  including the sensor setting device  36   a , the sensor interval setting device  36   b , and the data buffer  36   c  controls the temperature sensor  32  using the sensor setting device  36   a , the sensor interval setting device  36   b , and the data buffer  36   c  so as to detect a temperature. The sensor setting device  36   a  controls a state of the temperature sensor  32  in accordance with the information obtained from the command interpreter  35 . For example, the sensor setting device  36   a  enables the temperature sensor  32  when receiving the “enable signal” from the command interpreter  35 . On the other hand, the sensor setting device  36   a  disables the temperature sensor  32  for a period of time set in the timer  33  when receiving the “disable signal” from the command interpreter  35 . 
         [0059]    The sensor interval setting device  36   b  controls the timer  33  of the temperature sensor  32  in accordance with the information obtained from the command interpreter  35 . For example, the sensor interval setting device  36   b  does not set the timer  33  when receiving the information representing “extra acquisition interval=none” from the command interpreter  35 . Furthermore, the sensor interval setting device  36   b  sets 5 seconds to the timer  33  when receiving the information representing “extra acquisition interval=5 seconds” from the command interpreter  35 . 
         [0060]    The data buffer  36   c  serves as a storage device which stores data of temperatures sensed by the temperature sensor  32 . The temperature data stored in the data buffer  36   c  is referenced by the sensing application  37  under control of the switch  38 . 
         [0061]    The sensing application  37  manages entire temperature sensing executed by the sensor wireless terminal  30 . Specifically, when the sensing application  37  is executed, the measurement device  36 , the temperature sensor  32 , and the like operate to thereby execute the temperature sensing. Furthermore, the sensing application  37  reads the temperature data stored in the data buffer  36   c  and outputs the temperature data to the data transmitter  39  through the switch  38 . Moreover, the sensing application  37  refers to temperature data of the other terminal obtained by the command interpreter  35  through the switch  38 . In this case, the sensing application  37  inhibits the data transmitter  39  to output the temperature data. 
         [0062]    The switch  38  switches a reference destination of the sensing application  37  in accordance with an instruction issued by the command interpreter  35 . For example, when the command interpreter  35  instructs the switch  38  to refer to “temperature data of the other terminal”, the switch  38  switches access from the sensing application  37  to the “temperature data of the other terminal” instead of the data buffer  36   c . Note that the information representing “temperature data of the other terminal” is stored in a memory, an internal memory of the measurement device  36 , or the like. On the other hand, when the command interpreter  35  instructs the switch  38  to refer to “temperature data of itself”, the switch  38  switches access from the sensing application  37  to the data buffer  36   c.    
         [0063]    The data transmitter  39  transmits the temperature data obtained by the sensing application  37  from the data buffer  36   c  to the server  10  through the WLAN transmitter/receiver  31 . In this case, the data transmitter  39  may add an ID which identifies the device itself to a packet including the temperature data to be transmitted. 
         [0064]    Processing Flow 
         [0065]    Next, a process executed by the system illustrated in  FIG. 1  will be described with reference to  FIGS. 5 to 8 . Here, a process executed by the server  10 , a process executed by the sensor wireless terminal  30 , and a sequence of the system will be described. 
         [0066]    Process Executed by Server 
         [0067]      FIG. 5  is a flowchart illustrating a process executed by the server  10  according to the first embodiment. As illustrated in  FIG. 5 , when the WLAN transmitter/receiver  11  establishes a wireless communication with the sensor wireless terminals A and B (a determination is affirmative in step S 101 ), the data receiver  13  initializes the temperature data table  12  (in step S 102 ). Specifically, the data receiver  13  initializes the sensor control and the acquisition interval in the temperature data table  12 . 
         [0068]    Thereafter, when receiving the temperature data from the sensor wireless terminals A and B (a determination is affirmative in step S 103 ), the data receiver  13  stores the received temperature data in the temperature data table  12  (in step S 104 ) after associating the temperature data with IDs used to identify the terminals serving as transmission sources. Then the data comparator  14  compares the temperature data of the sensor wireless terminal A and the temperature data of the sensor wireless terminal B with each other with reference to the temperature data table  12  so as to determine whether a difference is smaller than a threshold value (in step S 105 ). 
         [0069]    When the difference between the temperature data of the sensor wireless terminals A and B is smaller than the threshold value (the determination is affirmative in step S 105 ), the extra-interval determination device  17  determines that one of the sensor wireless terminals A and B performs normal sensing and the sensing interval for the other of the sensor wireless terminals A and B is extended (in step S 106 ). In the example described above, the extra-interval determination device  17  determines “extra acquisition interval=none” for the sensor wireless terminal A whereas the extra-interval determination device  17  determines “extra acquisition interval=5 seconds” for the sensor wireless terminal B. 
         [0070]    Subsequently, the reference data determination device  15  determines that the sensor wireless terminals A and B refer to the same temperature data (in step S 107 ). In the example described above, the reference data determination device  15  determines that the sensor wireless terminal A obtains the sensor value of itself the sensor wireless terminal B obtains the sensor value obtained by the sensor wireless terminal A. 
         [0071]    Thereafter, the control signal generator  16  generates a control signal representing whether each of the sensor wireless terminals A and B is to perform sensing (in step S 108 ). In the example described above, the control signal generator  16  generates an “enable signal” for the sensor wireless terminal A and a “disable signal” for the sensor wireless terminal B. 
         [0072]    On the other hand, when the difference between the temperature data of the sensor wireless terminal A and the temperature data of the sensor wireless terminal B is not smaller than the threshold value (the determination is negative in step S 105 ), the extra-interval determination device  17  determines that the sensor wireless terminals A and B initialize the sensing intervals (in step S 109 ). 
         [0073]    Subsequently, the reference data determination device  15  determines that each of the sensor wireless terminals A and B refers to the temperature data sensed by itself (in step S 110 ). Furthermore, the control signal generator  16  generates a control signal which causes the sensor wireless terminals A and B to execute normal sensing (in step S 111 ). In the example described above, the control signal generator  16  generates an “enable signal” for the sensor wireless terminals A and B. 
         [0074]    Note that step S 106  to step S 108  are replaceable with one another. Similarly, step S 109  to step S 111  are replaceable with one another. 
         [0075]    Thereafter, the command generator  18  generates control commands for the sensor wireless terminals A and B in accordance with the information determined by the process from step S 106  to step S 108  or the information determined by the process from step S 109  to step S 111  (in step S 112 ). Then the command transmitter  19  transmits the control commands generated by the command generator  18  to the sensor wireless terminals A and B through the WLAN transmitter/receiver  11  (in step S 113 ). 
         [0076]    Thereafter, when the wireless connection with the sensor wireless terminals A and B is disconnected and the communication is terminated (a determination is affirmative in step S 114 ), the server  10  terminates the process. On the other hand, the wireless connection with the sensor wireless terminals A and B is continued (the determination is negative in step S 114 ), the server  10  repeatedly performs the process from step S 103  onwards. 
         [0077]    Process Executed by Sensor Wireless Terminal 
         [0078]      FIG. 6  is a flowchart illustrating a process executed by the sensor wireless terminal according to the first embodiment. As illustrated in  FIG. 6 , when the WLAN transmitter/receiver  31  establishes a wireless communication with the server  10  (a determination is affirmative in step S 201 ), the sensing application  37  starts temperature sensing (in step S 202 ). The data transmitter  39  transmits temperature data detected by the temperature sensor  32  to the server  10  through the WLAN transmitter/receiver  31  (in step S 203 ). 
         [0079]    Specifically, when the sensing application  37  executes the temperature sensing by operating the measurement device  36 , the temperature sensor  32 , and the like. Note that the temperature sensor  32  detects a temperature at a preset interval in an initial operation. 
         [0080]    Thereafter, when the command receiver  34  receives a control command from the server  10  (a determination is affirmative in step S 204 ), the command interpreter  35  determines whether a control signal included in the received control command is an “enable signal” (in step S 205 ). 
         [0081]    When the “enable signal” is received (the determination is affirmative in step S 205 ), the sensor setting device  36   a  sets the “enable signal” extracted from the control command by the command interpreter  35  to the temperature sensor  32  and enables the temperature sensor  32  (in step S 206 ). Subsequently, the sensor interval setting device  36   b  controls the switch  38  such that a reference destination of the sensing application  37  corresponds to the data buffer  36   c  in accordance with “reference destination temperature data” extracted by the command interpreter  35  from the control command (in step S 207 ). 
         [0082]    On the other hand, when a “disable signal” is received instead of the “enable signal” (the determination is negative in step S 205 ), the “disable signal” extracted by the command interpreter  35  from the control command is set to the temperature sensor  32  (in step S 208 ). As a result, the temperature sensor  32  stops the sensing for a period of time set in the timer  33 . Subsequently, the sensor interval setting device  36   b  controls the switch  38  such that the reference destination of the sensing application  37  corresponds to the “temperature data of the other device” obtained from the server  10  in accordance with “reference destination temperature data” extracted by the command interpreter  35  from the control command (in step S 209 ). Furthermore, the sensor interval setting device  36   b  sets an extra time to the timer  33  in accordance with the “extra acquisition interval” extracted by the command interpreter  35  from the control command (in step S 210 ). 
         [0083]    Thereafter, when the wireless connection with the server  10  is disconnected (a determination is affirmative in step S 211 ), the sensor wireless terminal  30  terminates the sensing of temperature data. On the other hand, the wireless communication with the server  10  is continued (the determination is negative in step S 211 ), the sensing application  37  of the sensor wireless terminal  30  determines whether the sensing interval has been reached (in step S 212 ). 
         [0084]    When the sensing interval has been reached (the determination is affirmative in step S 212 ), the sensing application  37  executes a process from step S 202  onwards. For example, when the process from step S 206  to step S 207  is performed, the sensing application  37  obtains temperature data after a prescribed initial interval such as an interval of 5 seconds is elapsed and transmits the temperature data to the server  10 . On the other hand, when the process from step S 208  to step S 210  is performed, the sensing application  37  obtains temperature data after the initial interval plus an extra time is elapsed, for example, and transmits the temperature data to the server  10 . 
         [0085]    Processing Sequence 
         [0086]      FIGS. 7A and 7B  and  FIG. 7C  are sequence diagrams illustrating a flow of a process executed by the system according to the first embodiment. Note that the process illustrated in  FIGS. 7A and 7B  and  FIG. 7C  is merely an example and does not limit the processing flow. 
         [0087]    As illustrated in  FIG. 7 , the WLAN transmitter/receiver  31  included in the sensor wireless terminal A accepts an instruction operation performed by the user or the like and establishes a wireless communication with the server  10  (in step S 301 ). Then the sensing application  37  activates the measurement device  36 , the temperature sensor  32 , and the like so as to obtain temperature data “SA 0 ”, and the data transmitter  39  transmits the temperature data “SA 0 ” to the server  10  (in step S 302 ). The data receiver  13  included in the server  10  receives the temperature data “SA 0 ” from the sensor wireless terminal A through the WLAN transmitter/receiver  11  and stores the temperature data “SA 0 ” in the temperature data table  12  (in step S 303 ). 
         [0088]    Similarly, the WLAN transmitter/receiver  31  included in the sensor wireless terminal B accepts an instruction operation performed by the user or the like and establishes a wireless communication with the server  10  (in step S 304 ). Then the sensing application  37  activates the measurement device  36 , the temperature sensor  32 , and the like so as to obtain temperature data “SB 0 ”, and the data transmitter  39  transmits the temperature data “SB 0 ” to the server  10  (in step S 305 ). The data receiver  13  included in the server  10  receives the temperature data “SB 0 ” from the sensor wireless terminal B through the WLAN transmitter/receiver  11  and stores the temperature data “SB 0 ” in the temperature data table  12  (in step S 306 ). 
         [0089]    Thereafter, the data comparator  14  included in the server  10  compares the temperature data “SA 0 ” and the temperature data “SB 0 ” with each other (in step S 307 ) and determines that a difference is smaller than a threshold value, that is, the difference is within an allowable range (in step S 308 ). Here, the data comparator  14  selects the temperature data “SA 0 ” as main data. 
         [0090]    Subsequently, the command generator  18  included in the server  10  generates control commands A and B in accordance with results output from the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17  (in step S 309 ). Specifically, the command generator  18  generates a control command A including information representing “control signal=enable signal, reference destination=SA 0 , and extra acquisition interval=timer zero”. Furthermore, the command generator  18  generates a control command B including information representing “control signal=disable signal, reference destination=SA 0 , and extra acquisition interval=timer (5 sec)”. 
         [0091]    Then the command transmitter  19  transmits the control commands A and B to the sensor wireless terminals A and B, respectively, through the WLAN transmitter/receiver  11  (in step S 310 ). 
         [0092]    In the sensor wireless terminal A, the command receiver  34  receives the control command A from the server  10  through the WLAN transmitter/receiver  31  (in step S 311 ). The sensor wireless terminal A executes a process in step S 312  and step S 313  in accordance with a result of an interpretation of the control command A performed by the command interpreter  35 . 
         [0093]    Specifically, the sensor setting device  36   a  sets the enable signal to the temperature sensor  32  so as to enable the temperature sensor  32  (in step S 312 ). Furthermore, the command interpreter  35  sets the data buffer  36   c  as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data “SA 0 ” of itself (in step S 313 ). 
         [0094]    In the sensor wireless terminal B, the command receiver  34  receives the control command B from the server  10  through the WLAN transmitter/receiver  31  (in step S 314 ). The sensor wireless terminal B executes a process from step S 315  to step S 317  in accordance with a result of an interpretation of the control command B performed by the command interpreter  35 . 
         [0095]    Specifically, the sensor setting device  36   a  sets the disable signal to the temperature sensor  32  so as to disable the temperature sensor  32  (in step S 315 ). Furthermore, the command interpreter  35  sets the received temperature data “SA 0 ” as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data of the other terminal (in step S 316 ). Moreover, the sensor interval setting device  36   b  sets a timer value “5 sec” to the timer  33  in accordance with the information “extra acquisition interval=timer (5 sec)” (in step S 317 ). 
         [0096]    Thereafter, the sensor wireless terminal A executes temperature sensing at a preset initial interval. Specifically, the temperature sensor  32  detects temperature data “SA 1 ” after the preset initial interval and the data transmitter  39  transmits the detected temperature data “SA 1 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 318 ). The data receiver  13  included in the server  10  receives the temperature data “SA 1 ” from the sensor wireless terminal A through the WLAN transmitter/receiver  11  and stores the temperature data “SA 1 ” in the temperature data table  12  (in step S 319 ). 
         [0097]    Furthermore, the temperature sensor  32  detects temperature data “SA 2 ” after the preset initial interval and the data transmitter  39  transmits the detected temperature data “SA 2 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 320 ). The data receiver  13  included in the server  10  receives the temperature data “SA 2 ” from the sensor wireless terminal A through the WLAN transmitter/receiver  11  and stores the temperature data “SA 2 ” in the temperature data table  12  (in step S 321 ). 
         [0098]    Thereafter, the sensor wireless terminal B executes temperature sensing after a period of time obtained by adding the timer setting value to the preset initial interval (in step S 322 ). Specifically, the temperature sensor  32  detects temperature data “SB 1 ” after the period of time obtained by adding the timer setting value to the preset initial interval and the data transmitter  39  transmits the detected temperature data “SB 1 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 323 ). The data receiver  13  included in the server  10  receives the temperature data “SB 1 ” from the sensor wireless terminal B through the WLAN transmitter/receiver  11  and stores the temperature data “SB 1 ” in the temperature data table  12  (in step S 324 ). 
         [0099]    Thereafter, the data comparator  14  included in the server  10  compares the temperature data “SA 2 ” and the temperature data “SB 1 ” with each other (in step S 325 ) and determines that a difference is smaller than a threshold value, that is, the difference is within an allowable range (in step S 326 ). Here, the data comparator  14  selects the temperature data “SA 2 ” as main data. Note that the data comparator  14  determines a comparison target using time stamps of temperature data received from the terminals A and B. 
         [0100]    Subsequently, the command generator  18  included in the server  10  generates control commands A and B in accordance with results output from the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17  (in step S 327 ). Here, the extra-interval determination device  17  specifies an extra time which is longer than a period of time which has been extended before since a difference between the temperature data is consecutively smaller than the threshold value. Specifically, the command generator  18  generates a control command A including information representing “control signal=enable signal, reference destination=SA 2 , and extra acquisition interval=timer zero”. Furthermore, the command generator  18  generates a control command B including information representing “control signal=disable signal, reference destination=SA 2 , and extra acquisition interval=timer (5 sec×2=10 sec)”. 
         [0101]    Then the command transmitter  19  included in the server  10  transmits the control commands A and B to the sensor wireless terminals A and B, respectively, through the WLAN transmitter/receiver  11  (in step S 328 ). 
         [0102]    In the sensor wireless terminal A, the command receiver  34  receives the control command A from the server  10  through the WLAN transmitter/receiver  31  (in step S 329 ). The sensor wireless terminal A executes a process in step S 330  and step S 331  in accordance with a result of an interpretation of the control command A performed by the command interpreter  35 . 
         [0103]    Specifically, the sensor setting device  36   a  sets the enable signal to the temperature sensor  32  so as to enable the temperature sensor  32  (in step S 330 ). Furthermore, the command interpreter  35  sets the data buffer  36   c  as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data “SA 2 ” of itself (in step S 331 ). 
         [0104]    In the sensor wireless terminal B, the command receiver  34  receives the control command B from the server  10  through the WLAN transmitter/receiver  31  (in step S 332 ). The sensor wireless terminal B executes a process from step S 333  to step S 335  in accordance with a result of an interpretation of the control command B performed by the command interpreter  35 . 
         [0105]    Specifically, the sensor setting device  36   a  sets the disable signal to the temperature sensor  32  so as to disable the temperature sensor  32  (in step S 333 ). Furthermore, the command interpreter  35  sets the received temperature data “SA 2 ” as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data “SA 2 ” of the other terminal (in step S 334 ). Moreover, the sensor interval setting device  36   b  sets a timer value “10 sec” to the timer  33  in accordance with the information “extra acquisition interval=timer (10 sec)” (in step S 335 ). 
         [0106]    Thereafter, the sensor wireless terminal A executes temperature sensing after the preset initial interval. Specifically, the temperature sensor  32  detects temperature data “SA 3 ” after the preset initial interval and the data transmitter  39  transmits the detected temperature data “SA 3 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 336 ). The data receiver  13  included in the server  10  receives the temperature data “SA 3 ” from the sensor wireless terminal A through the WLAN transmitter/receiver  11  and stores the temperature data “SA 3 ” in the temperature data table  12  (in step S 337 ). 
         [0107]    Furthermore, the temperature sensor  32  detects temperature data “SA 4 ” after the preset initial interval and the data transmitter  39  transmits the detected temperature data “SA 4 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 338 ). The data receiver  13  included in the server  10  receives the temperature data “SA 4 ” from the sensor wireless terminal A through the WLAN transmitter/receiver  11  and stores the temperature data “SA 4 ” in the temperature data table  12  (in step S 339 ). 
         [0108]    Thereafter, the sensor wireless terminal B executes temperature sensing after a period of time obtained by adding the timer setting value to the preset initial interval (in step S 340 ). Specifically, the temperature sensor  32  detects temperature data “SB 2 ” after the period of time obtained by adding the timer setting value to the preset initial interval and the data transmitter  39  transmits the detected temperature data “SB 2 ” to the server  10  through the WLAN transmitter/receiver  31  (in step S 341 ). The data receiver  13  included in the server  10  receives the temperature data “SB 2 ” from the sensor wireless terminal B through the WLAN transmitter/receiver  11  and stores the temperature data “SB 2 ” in the temperature data table  12  (in step S 342 ). 
         [0109]    Thereafter, the data comparator  14  included in the server  10  compares the temperature data “SA 4 ” and the temperature data “SB 2 ” with each other (in step S 343 ) and determines that a difference is not smaller than a threshold value, that is, the difference is out of the allowable range (in step S 344 ). Note that the data comparator  14  determines a comparison target using time stamps of temperature data received from the terminals A and B. 
         [0110]    Subsequently, the command generator  18  included in the server  10  generates control commands A and B in accordance with results output from the reference data determination device  15 , the control signal generator  16 , and the extra-interval determination device  17  (in step S 345 ). Specifically, the command generator  18  generates a control command A including information representing “control signal=enable signal, reference destination=SA 4 , and extra acquisition interval=timer zero”. Furthermore, the command generator  18  generates a control command B including information representing “control signal=enable signal, reference destination=SB 2 , and extra acquisition interval=timer zero”. 
         [0111]    Then the command transmitter  19  transmits the control commands A and B to the sensor wireless terminals A and B, respectively, through the WLAN transmitter/receiver  11  (in step S 346 ). 
         [0112]    In the sensor wireless terminal A, the command receiver  34  receives the control command A from the server  10  through the WLAN transmitter/receiver  31  (in step S 347 ). The sensor wireless terminal A executes a process in step S 348  and step S 349  in accordance with a result of an interpretation of the control command A performed by the command interpreter  35 . 
         [0113]    Specifically, the sensor setting device  36   a  sets the enable signal to the temperature sensor  32  so as to enable the temperature sensor  32  (in step S 348 ). Furthermore, the command interpreter  35  sets the data buffer  36   c  as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data “SA 4 ” of itself (in step S 349 ). 
         [0114]    In the sensor wireless terminal B, the command receiver  34  receives the control command B from the server  10  through the WLAN transmitter/receiver  31  (in step S 350 ). The sensor wireless terminal B executes a process from step S 351  to step S 353  in accordance with a result of an interpretation of the control command B performed by the command interpreter  35 . 
         [0115]    Specifically, the sensor setting device  36   a  sets the enable signal to the temperature sensor  32  so as to enable the temperature sensor  32  (in step S 351 ). Furthermore, the command interpreter  35  sets the data buffer  36   c  as a switching destination of the switch  38  since the received “reference destination” indicates the temperature data “SB 2 ” of itself (in step S 352 ). Moreover, the sensor interval setting device  36   b  initializes the timer value of the timer  33  in accordance with the information “extra acquisition interval=timer zero” (in step S 353 ). Thereafter, while the server  10  and the sensor wireless terminals A and B are connected to each other by the wireless communication, the process from step S 301  to step S 353  described above is repeatedly performed. 
       Advantages of First Embodiment 
       [0116]    As described above, the sensor wireless terminals A and B execute the temperature sensing in accordance with extra times (timer) supplied from the server  10  and supplies results of the sensing to the server  10 . When a difference between the temperature data of the sensor wireless terminals A and B is smaller than the threshold value, the server  10  instructs one of the sensor wireless terminals A and B to perform the temperature sensing and instructs the other of the sensor wireless terminals A and B to interrupt the temperature sensing for a predetermined period of time. As a result, power consumed when the temperature sensing is performed by one of the sensor wireless terminals A and B may be reduced, and therefore, power consumption of the sensor wireless terminals A and B may be suppressed and reduction of power consumption may be realized in a unit of a terminal group. Accordingly, electric power saving is realized with a high degree which is not realized by a single terminal. 
       Second Embodiment 
       [0117]    In the first embodiment, the server  10  receives sensing data from the sensor wireless terminals A and B and controls the sensing intervals. However, the embodiment is not limited to this. For example, the server  10  may receive usage states of the sensor wireless terminals A and B so as to control the sensing intervals. 
         [0118]    In a second embodiment, as an example of a server  10  which receives usage states of sensor wireless terminals so as to control sensing intervals, the server  10  obtains usage information representing as to whether a user which has sensor wireless terminals is on a train. Therefore, in the second embodiment, the sensor wireless terminals include acceleration sensors. Furthermore, the server  10  includes a usage information table which stores usage information received from the sensor wireless terminals. 
         [0119]      FIG. 8  is a sequence diagram illustrating a process executed by the system according to the second embodiment. When a WLAN transmitter/receiver  31  included in a sensor wireless terminal A accepts an instruction operation performed by a user or the like and establishes a wireless communication with the server  10  (in step S 401 ). 
         [0120]    Then a sensing application  37  activates a measurement device  36 , an acceleration sensor, and the like so as to obtain an acceleration rate, and a data transmitter  39  transmits usage information A determined in accordance with the acceleration rate to the server  10  (in step S 402 ). For example, when the obtained acceleration rate is equal to or larger than a predetermined value, the sensing application  37  determines that a user who has the sensor wireless terminal A is on a train or the like. The data transmitter  39  transmits information representing “on board” to the server  10  as usage information A. Note that, when the obtained acceleration rate is smaller than the predetermined value, the sensing application  37  determines that the user who has the sensor wireless terminal A is not on a train or the like. In this case, the data transmitter  39  transmits information representing “not on board” to the server  10  as the usage information A. 
         [0121]    The data receiver  13  included in the server  10  receives the usage information A “on board” from the sensor wireless terminal A through a WLAN transmitter/receiver  11  and stores the usage information “on board” in the usage information table (in step S 403 ). 
         [0122]    Similarly, the WLAN transmitter/receiver  31  included in the sensor wireless terminal B accepts an instruction operation performed by the user or the like and establishes a wireless communication with the server  10  (in step S 404 ). Then the sensing application  37  activates the measurement device  36 , the acceleration sensor, and the like so as to obtain an acceleration rate, and the data transmitter  39  transmits usage information B “on board” determined in accordance with the acceleration rate to the server  10  (in step S 405 ). 
         [0123]    The data receiver  13  included in the server  10  receives the usage information B “on board” from the sensor wireless terminal B through the WLAN transmitter/receiver  11  and stores the usage information B “on board” in the usage information table (in step S 406 ). 
         [0124]    Thereafter, a data comparator  14  included in the server  10  compares the usage information A “on board” and the usage information B “on board” with each other (in step S 407 ) and determines that the usage information A and the usage information B match each other (in step S 408 ). In this case, the data comparator  14  selects the usage information A “on board” as main data. 
         [0125]    Subsequently, a command generator  18  included in the server  10  generates control commands A and B in accordance with results output from a reference data determination device  15 , a control signal generator  16 , and an extra-interval determination device  17  (in step S 409 ). Specifically, the command generator  18  generates a control command A including information representing “control signal=enable signal, reference destination=usage information A “on board”, and extra acquisition interval=timer zero”. Furthermore, the command generator  18  generates a control command B including information representing “control signal=disable signal, reference destination=usage information A “on board”, and extra acquisition interval=timer (10 sec)”. 
         [0126]    Then the command transmitter  19  included in the server  10  transmits the control commands A and B to the sensor wireless terminals A and B, respectively, through the WLAN transmitter/receiver  11  (in step S 410 ). 
         [0127]    In the sensor wireless terminal A, a command receiver  34  receives the control command A from the server  10  through the WLAN transmitter/receiver  31  (in step S 411 ). The sensor wireless terminal A executes a process in step S 412  and step S 413  in accordance with a result of an interpretation of the control command A performed by a command interpreter  35 . 
         [0128]    Specifically, a sensor setting device  36   a  sets the enable signal to the acceleration sensor so as to enable the acceleration sensor (in step S 412 ). Furthermore, the command interpreter  35  sets the information representing “on board” as a usage scene in accordance with the obtained “usage information A “on board”” (in step S 413 ). Specifically, the command interpreter  35  sets a data buffer  36   c  as a switching destination of the switch  38 . 
         [0129]    In the sensor wireless terminal B, the command receiver  31  receives the control command B from the server  10  through the WLAN transmitter/receiver  31  (in step S 414 ). The sensor wireless terminal B executes a process from step S 415  to step S 417  in accordance with a result of an interpretation of the control command B performed by the command interpreter  35 . 
         [0130]    Specifically, a sensor setting device  36   a  sets the disable signal to the acceleration sensor so as to disable the acceleration sensor (in step S 415 ). Furthermore, the command interpreter  35  sets the information representing “on board” as a usage scene in accordance with the obtained “usage information A “on board”” (in step S 416 ). Specifically, the command interpreter  35  sets the received data as a switching destination of the switch  38  instead of the data buffer  36   c . Moreover, the sensor interval setting device  36   b  sets a timer value “10 sec” to the timer  33  in accordance with the information “extra acquisition interval=timer (10 sec)” (in step S 417 ). 
         [0131]    As described above, the server  10  may control not only the sensing data but also the sensing interval using the information determined by the sensing data. Accordingly, a method for controlling the sensing interval performed by the server  10  may be utilized in various fields. 
       Third Embodiment 
       [0132]    Although the embodiments of the present disclosure have been described hereinabove, various modifications of the foregoing embodiments may be made. Therefore, other embodiments will be described hereinafter. 
         [0133]    Grouping According to Electric Wave Intensity 
         [0134]    For example, a server  10  may group sensor wireless terminals which are in the same space, that is, which use the same access point according to electric wave intensity and thereafter may perform the processes in the first and second embodiments for each group. 
         [0135]      FIG. 9  is a diagram illustrating the grouping. As illustrated in  FIG. 9 , the server  10  is connected to sensor wireless terminals A to D via a wireless communication. The sensor wireless terminals A to D are included in the same space. 
         [0136]    When establishing the wireless communication with the sensor wireless terminals A to D, the server  10  measures intensities of electric waves of the wireless communication transmitted by the sensor wireless terminals A to D. Note that the measurement of the electric wave intensities may be performed using a general technique, and therefore, detailed description thereof is omitted. 
         [0137]    For example, the server  10  determines that the sensor wireless terminal A transmits an electric wave having an intensity of “intensity level 1”, the sensor wireless terminal B transmits an electric wave having an intensity of “intensity level 2”, the sensor wireless terminal C transmits an electric wave having an intensity of “intensity level 2”, and the sensor wireless terminal D transmits an electric wave having an intensity of “intensity level 1”. 
         [0138]    Thereafter, the server  10  makes a group including the sensor wireless terminals A and D which have the electric wave intensity of “intensity level 1” and a group including the sensor wireless terminals B and C which have the electric wave intensity of “intensity level 2”. The server  10  may execute the processes of the first and second embodiments for each group. 
         [0139]    In this way, even when sensor wireless terminals are located in a large space, the server  10  divides the space into a plurality of regions by performing the grouping according to electric wave intensities. When similar values are sensed in each of the regions, the server  10  may realize power saving of the terminals other than at least one terminal. Note that, as for the grouping according to the electric wave intensities, not only the grouping performed by grouping terminals having the same electric wave intensity but also grouping performed by grouping terminals having electric wave intensities within a predetermined range may be employed. 
         [0140]    Grouping According to Access Point 
         [0141]    Although the case where the server  10  has a function of an access point has been described in the first embodiment, the embodiment is not limited to this and the server  10  and the access point may be separately provided. 
         [0142]      FIG. 10  is a diagram illustrating grouping according to access points. As illustrated in  FIG. 10 , the server  10  is connected to sensor wireless terminals A to D via a wireless communication. Furthermore, the sensor wireless terminals A and B are managed by an access point having an ID of AP 01 . The sensor wireless terminals C and D are managed by an access point having an ID of AP 02 . The server  10  is connected to the access points. 
         [0143]    The server  10  may execute the processes of the first and second embodiments for each access point. Specifically, the server  10  performs the processes of the first and second embodiments on a first group including the sensor wireless terminals A and B and a second group including the sensor wireless terminals C and D. 
         [0144]    By this, processes the same as those of the first and second embodiments may be executed without adding a function to the existing access points. Furthermore, since the server  10  may manage a plurality of access points, reduction of cost and reduction of power consumption may be attained when compared with a case where a plurality of servers  10  are provided for a plurality of access points. 
         [0145]    Communication Method 
         [0146]    In the foregoing embodiments, the server  10  receives a sensing value from the sensor wireless terminals or the access points through a wireless communication, for example. However, the embodiments are not limited to these. For example, the server  10  and sensor wireless terminals or access points may be connected to one another in a wired manner. Furthermore, the server  10  may receive sensor values of the sensor wireless terminals input by an administrator. In this case, the server  10  executes the processes in the first embodiment in accordance with the sensor values input by the administrator and displays information on generated control commands in a display or the like. Then advantages similar to those of the first embodiment may be obtained by executing commands input by the administrator to the sensor wireless terminals. 
         [0147]    The Number of Sensor Wireless Terminals 
         [0148]    For example, in the foregoing embodiments, the case where the two sensor wireless terminals are used has been described. However, the embodiments are not limited to this and three or more sensor wireless terminals may be used. When three or more sensor wireless terminals are used, processes similar to those of the second embodiment may be executed by performing a determination as to whether an average or a standard deviation of sensor values obtained from the terminals is smaller than a threshold value by the server  10 . Furthermore, processes similar to those of the second embodiment may be executed by performing calculations of differences of the sensor values of the terminals and performing a determination as to whether a sum of the differences is smaller than a threshold value. 
         [0149]    Control of Interval 
         [0150]    In the foregoing embodiments, the case where the server  10  extends the sensing interval of the sensor wireless terminals, that is, an interval of detection of temperature data performed by the temperature sensor has been described. However, the embodiments are not limited to this. For example, the server  10  may extend an interval of transmission of a sensor value from a sensor wireless terminal to the server  10 . 
         [0151]    In the foregoing embodiments, in the sensor wireless terminals, when the temperature sensor or the like obtains a sensor value, the sensor value is transmitted to the server  10 . However, an interval of the transmission of the sensor value to the server  10  may be extended. Consequently, power consumption of the transmission of the sensor value may be suppressed instead of power consumption of the sensor. Furthermore, control of an acquisition interval and control of a transmission interval may be performed in combination. In this case, both of the power consumption of the sensor and the power consumption of the transmission of the sensor value may be suppressed. 
         [0152]    System 
         [0153]    Furthermore, in the processes described in the foregoing embodiments, all or some of processes which are automatically executed may be manually performed. Alternatively, all or some of processes which are manually executed may be automatically performed using a general method. Furthermore, the processing procedures, the control procedures, the concrete names, and the information including various data illustrated in  FIG. 3  and parameters which are described in the specification and illustrated in the drawings may be arbitrarily changed unless otherwise specified. 
         [0154]    Moreover, the illustrated components included in the devices are conceptual functions and may not be physically configured as illustrated in the drawings. Specifically, a detailed configuration of distribution and integration of the devices is not limited to those illustrated in the drawings. That is, all or some of the devices may be functionally or physically distributed or integrated in an arbitrary unit depending on various loads or usage states. Furthermore, all or some of the processing functions performed by the devices may be realized by a CPU or programs which are analyzed and executed by the CPU or may be realized as hardware using a wired logic. 
         [0155]    Program 
         [0156]    The various processes described in the foregoing embodiments may be realized by executing programs which are provided in advance using a computer system such as a personal computer or a work station. Therefore, an example of a computer system which executes programs having functions the same as the functions of the foregoing embodiments will be described. 
         [0157]      FIG. 11  is a diagram illustrating a hardware configuration of a computer which executes a server-side sensor control program. As illustrated in  FIG. 11 , a computer system  100  include a CPU  102 , an input device  103 , an output device  104 , a communication interface  105 , an HDD (Hard Disk Drive)  106 , and a RAM (Random Access Memory)  107  which are connected to a bus  101 . 
         [0158]    The input device  103  includes a mouse and a keyboard. The output device  104  includes a display. The communication interface  105  is an interface such as an NIC (Network Interface Card). The HDD  106  stores information stored in the table illustrated in  FIG. 3  along with a server sensor-control program  106   a . Although the HDD  106  is employed as an example of a recording medium, various programs may be stored in a computer readable recording medium such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a CD-ROM and may be read by a computer. Alternatively, the programs may be obtained when a computer accesses the storage medium remotely located. In this case, the obtained programs to be may be stored in a recording medium included in the computer. 
         [0159]    The CPU  102  reads the server sensor-control program  106   a  and executes the server sensor-control program  106   a  in the RAM  107  to thereby activate a server sensor-control process  107   a  which executes the various functions described with reference to  FIG. 2  and so on. Specifically, the server sensor-control process  107   a  executes functions similar to those of the data receiver  13 , the data comparator  14 , the reference data determination device  15 , the control signal generator  16 , the extra-interval determination device  17 , the command generator  18 , and the command transmitter  19  illustrated in  FIG. 2 . As described above, the computer system  100  operates as an information processing apparatus which executes a server sensor control method by reading and executing the programs. 
         [0160]      FIG. 12  is a diagram illustrating a hardware configuration of a computer which executes a terminal-side sensor control program. As illustrated in  FIG. 12 , a computer system  200  include a CPU  202 , an input device  203 , an output device  204 , a communication interface  205 , an HDD  206 , and a RAM  207  which are connected to a bus  201 . 
         [0161]    The input device  203  includes a mouse and a keyboard. The output device  204  includes a display. The communication interface  205  is an interface such as an NIC. The HDD  206  stores the information stored in the data buffer illustrated in  FIG. 3  along with a terminal sensor-control program  206   a . Although the HDD  206  is employed as an example of a recording medium, various programs may be stored in a computer readable recording medium such as a ROM, a RAM, or a CD-ROM and may be read by a computer. Alternatively, the programs may be obtained when a computer accesses a storage medium remotely located. In this case, the obtained programs may be stored in a recording medium included in the computer. 
         [0162]    The CPU  202  reads the terminal sensor-control program  206   a  and executes the terminal sensor-control program  206   a  in the RAM  207  to thereby activate a terminal sensor-control process  207   a  which executes the various functions described with reference to  FIG. 4  and so on. Specifically, the terminal sensor-control process  207   a  executes functions similar to those of the command receiver  34 , the command interpreter  35 , the measurement device  36 , the sensing application  37 , the switch  38 , and the data transmitter  39  illustrated in  FIG. 4 . As described above, the computer system  200  operates as an information processing apparatus which performs a terminal sensor control method by reading and executing a program. 
         [0163]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.