Abstract:
A method of controlling a mobile terminal apparatus includes selecting, using a processor, a sensor from a plurality of sensors installed on the mobile terminal apparatus based on both of power consumption for determining whether the mobile terminal apparatus has moved based on an output of at least any one of the sensors and power consumption for identifying a position of the mobile terminal apparatus, determining whether the mobile terminal apparatus has moved based on an output of the sensor selected in the selecting, and identifying a position of the mobile terminal apparatus when it is determined that the mobile terminal apparatus has moved in the determining.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2012-234419 filed on Oct. 24, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a method of controlling a mobile terminal apparatus and a mobile terminal apparatus. 
     BACKGROUND 
     In recent years, so-called positional services are becoming widespread. In the positional services, positional information of a mobile terminal apparatus is obtained using the Global Positioning System (GPS), a wireless local area network (WLAN), a baseband, and so on, and services depending on a position of the mobile terminal apparatus are provided. 
     Under the above-described circumstances, power consumption for positioning a mobile terminal apparatus (hereinafter referred to as a positioning power) is increasing. In particular, in the GPS, a bit rate of GPS signals from satellites is low (50 bps), and it takes about 30 minutes for receiving a GPS signal frame (1500 bits). Accordingly, compared with power consumption for obtaining state information of a mobile terminal apparatus by, for example, an acceleration, the number of steps, and so on, positioning power at the time of using GPS increases drastically. Also, in a WLAN and a baseband, a Basic Service Set Identifier (BSSID) and a cell-ID, which are obtained by a mobile terminal apparatus, have to be transmitted to a server, and thus compared with power consumption for obtaining state information of a mobile terminal apparatus, for example, an acceleration, the number of steps, and so on, positioning power increases drastically. Accordingly, it becomes important to reduce power consumption for positioning the mobile terminal apparatus. 
     For a mechanism to reduce power consumption, a control technique of a mobile terminal apparatus has been proposed in which, for example, a determination (hereinafter referred to as a “movement determination”) is made of whether the mobile terminal apparatus has moved or not using sensors installed on the mobile terminal apparatus, and if the mobile terminal apparatus has not been moved, positioning is not carried out, and the positional information already obtained is used. 
     In the above control technique, a sensor consumes power for movement determination, but positioning power, which is greater than power consumption for movement determination, is reduced, and thus it is possible to suppress power consumption of the mobile terminal apparatus as a result. 
     Related-art techniques have been disclosed in Japanese Laid-open Patent Publication Nos. 2011-149860, 2000-352519, and 2011-022115. 
     SUMMARY 
     According to an aspect of the invention, a method of controlling a mobile terminal apparatus includes selecting, using a processor, a sensor from a plurality of sensors installed on the mobile terminal apparatus based on both of power consumption for determining whether the mobile terminal apparatus has moved based on an output of at least any one of the sensors and power consumption for identifying a position of the mobile terminal apparatus, determining whether the mobile terminal apparatus has moved based on an output of the sensor selected in the selecting, and identifying a position of the mobile terminal apparatus when it is determined that the mobile terminal apparatus has moved in the determining. 
     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. 
     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 
         FIG. 1  is a schematic diagram of a hardware configuration of a mobile terminal apparatus according to a first embodiment; 
         FIG. 2  is a schematic diagram of functional blocks of the mobile terminal apparatus according to the first embodiment; 
         FIG. 3  is a schematic diagram of a movement-determination failure rate table according to the first embodiment; 
         FIG. 4  is a schematic diagram of a power consumption table according to the first embodiment; 
         FIG. 5  is a flowchart of sensor selection processing according to the first embodiment; 
         FIG. 6  is a schematic diagram of a movement-determination failure rate table according to a second embodiment; 
         FIG. 7  is a schematic diagram of a power consumption table according to the second embodiment; 
         FIG. 8  is a schematic diagram of functional blocks of a mobile terminal apparatus according to a third embodiment; 
         FIG. 9  is a schematic diagram of a movement-determination failure rate table according to the third embodiment; and 
         FIG. 10  is a flowchart of sensor update processing according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In a control technique of a mobile terminal apparatus according to related-art techniques, a sensor determined in advance is used for movement determination for the mobile terminal apparatus. However, movement determination of a mobile terminal apparatus is largely dependent on a kind of and a combination of sensors used, or an operation state of the mobile terminal apparatus, and so on. Accordingly, if a sensor determined in advance is used, that is to say, if a sensor to be used is fixed, a failure often occurs in movement determination depending on a kind of and a combination of the sensors. If determined that a mobile terminal apparatus has moved in spite of the fact that the mobile terminal apparatus has not moved, for example, positioning is carried out uselessly, and the power consumption increases as a result. 
     First Embodiment 
     In the following, a description will be given of a first embodiment with reference to  FIG. 1  to  FIG. 5 . 
     Hardware Configuration of Mobile Terminal Apparatus  100   
     A description will be given of a mobile terminal apparatus  100  according to the first embodiment. Here, Android (a registered trademark) is employed as an operating system (OS) to be installed in the mobile terminal apparatus  100 . However, an embodiment of the present disclosure is not limited to this, and an OS other than Android may be employed. Also, although not limited in particular, the mobile terminal apparatus  100  according to the present embodiment is assumed to be a mobile information processing apparatus, for example a smart phone, a tablet PC, a digital camera, and so on. 
     Hardware of Mobile Terminal Apparatus  100   
       FIG. 1  is a schematic diagram of a hardware configuration of the mobile terminal apparatus  100  according to the first embodiment. 
     As illustrated in  FIG. 1 , the mobile terminal apparatus  100  according to the present embodiment includes a central processing unit (CPU)  101 , a main memory  102 , an auxiliary memory  103 , a clock supply circuit  104 , a voltage supply circuit  105 , a battery  106 , a power source circuit  107 , an external power supply unit  108 , a display  109 , a touch screen  110 , a network interface (I/F)  111 , and a sensor  112  as hardware modules. These hardware modules are mutually connected through a bus  113 . 
     It is assumed that the CPU  101  is not a baseband large scale integrated (LSI), but is a processor that executes an application program. The CPU  101  is operated by a clock signal supplied from the clock supply circuit  104  and a voltage supplied from the voltage supply circuit  105 , and controls various hardware modules of the mobile terminal apparatus  100 . Further, the CPU  101  reads various programs stored in the auxiliary memory  103  into the main memory  102 , and executes the various programs read in the main memory  102  so as to achieve various functions. Detailed descriptions will be given of the various functions later. 
     The main memory  102  stores the various programs to be executed by the CPU  101 . Further, the main memory  102  is used as a work area of the CPU  101 , and stores various kinds of data that is desired for processing by the CPU  101 . For a main memory  102 , for example, a random access memory (RAM), and so on may be used. 
     The auxiliary memory  103  stores various programs that operate the mobile terminal apparatus  100 . For the various programs, for example, application programs that are executed by the mobile terminal apparatus  100 , an OS  1000 , which is an execution environment of the application programs, and so on are provided. The control program  1100  according to the present embodiment is also stored in the auxiliary memory  103 . For the auxiliary memory  103 , a nonvolatile memory, for example a hard disk, a flash memory, and so on may be used. 
     The clock supply circuit  104  generates the clock signal to be supplied to the CPU  101 . The clock supply circuit  104  may be achieved, for example, by a quartz oscillator that oscillates the clock signal and a real time clock (RTC). 
     The voltage supply circuit  105  generates a variable voltage to be supplied to the CPU  101  on the basis of the power supplied from the power source circuit  107 . The voltage supply circuit  105  may be achieved by a voltage detector and a voltage regulator. 
     The battery  106  supplies power to the power source circuit  107 . The battery  106  may be achieved, for example by a battery, such as a lithium-ion battery, and so on, and a battery protection integrated circuit (IC). 
     The power source circuit  107  supplies the power supplied from the battery  106  to various hardware modules of the mobile terminal apparatus  100  through a power source line (not illustrated in  FIG. 1 ). In this regard, if an external power source (not illustrated in  FIG. 1 ) is connected to the external power supply unit  108 , the power source circuit  107  may supply the power supplied from the external power supply unit  108  to various hardware modules of the mobile terminal apparatus  100 . The power source circuit  107  may be achieved, for example by a switching regulator and a voltage regulator. 
     The display  109  is controlled by the CPU  101 , and displays image information to be presented to the user. The touch screen  110  is attached to the display  109 , and receives input of positional information touched by a user&#39;s fingertip, a pen point, and so on. 
     The network I/F  111  is controlled by the CPU  101 , and functions, for example as an interface of communication by a WLAN and a baseband. 
     The sensor  112  obtains the state information (state information of the user of the mobile terminal apparatus  100 ) of the mobile terminal apparatus  100 . For the sensor  112 , for example, a baseband, a pedometer, a WLAN, Bluetooth (a registered trademark), an accelerometer, a camera, an illuminance meter, a barometer, and so on may be used. In the case of using a pedometer, Bluetooth, an accelerometer, a camera, an illuminance meter, and a barometer as a sensor  112 , a number of steps, a peripheral device of Bluetooth, an acceleration, an image, an illuminance, an atmospheric pressure are detected, respectively. 
     In this regard, a baseband here is handled as a sensor for detecting a cell-ID transmitted from a base station of, for example, 3G (3rd Generation), and so on, and a WLAN is handled as a sensor for detecting a BSSID transmitted from an access point. However, a baseband and a WLAN according to the present embodiment are sometimes used as a positioning mechanism in the same manner as the GPS. 
     Functional Blocks of Mobile Terminal Apparatus  100   
       FIG. 2  is a schematic diagram of functional blocks of the mobile terminal apparatus  100  according to the first embodiment. 
     As illustrated in  FIG. 2 , the mobile terminal apparatus  100  according to the present embodiment includes a positioning control unit  121 , a movement determination unit  122 , and a sensor selection unit  123 . 
     Any one of the positioning control unit  121 , the movement determination unit  122 , and the sensor selection unit  123  is achieved by the CPU  101  reading the control program  1100  into the main memory  102 , and executing the control program  1100  read into the main memory  102 . 
     In this regard, an application  130  in  FIG. 2  is an application (position use application) that uses positional information, and is achieved by the CPU  101  reading the application program into the main memory  102 , and executing the application program read into the main memory  102 . A positioning driver  140  in  FIG. 2  is achieved by the CPU  101  reading the kernel of the OS  1000  into the main memory  102 , and executing the application program read into the main memory  102 . 
     Positioning Control Unit  121   
     The positioning control unit  121  gives an indication of whether the mobile terminal apparatus  100  has moved or not, that is to say, a movement determination to the movement determination unit  122  on the basis of a positioning request from the application  130 . Further, the positioning control unit  121  obtains positional information of the mobile terminal apparatus  100  on the basis of the determination result by the movement determination unit  122 , and notifies the positional information to the application  130 . For example, if the determination result by the movement determination unit  122  is “moved”, the positioning control unit  121  instructs the positioning driver  140  to perform positioning, and notifies the positional information obtained by the positioning driver  140  to the application  130 . On the other hand, if the determination result by the movement determination unit  122  is “not moved”, the positioning control unit  121  notifies the latest positional information stored in a positional information storage unit  126  to the application  130 . In this regard, the latest positional information corresponds to the positional information obtained by the previous positioning. 
     Movement Determination Unit  122   
     The movement determination unit  122  gives an instruction of selection of the sensors  112  to be used for movement determination of the mobile terminal apparatus  100  to the sensor selection unit  123  with a trigger of an instruction from the positioning control unit  121 . Further, the movement determination unit  122  carries out movement determination of the mobile terminal apparatus  100  using the sensor  112  selected by the sensor selection unit  123 . Here, if the sensor selection unit  123  selects a plurality of the sensors  112 , the movement determination unit  122  carries out movement determination of the mobile terminal apparatus  100  using all of the plurality of the sensors  112 . Specifically, if a baseband, a pedometer, a WLAN, Bluetooth, a camera, an illuminance meter, a barometer, an accelerometer, and so on are selected as the sensors  112 , the movement determination unit  122  carries out movement determination of the mobile terminal apparatus  100  on the basis of a change of cell-ID, a change in radio wave intensity, a change in the number of steps, a change in the BSSID obtained by scanning, a change of peripheral device of Bluetooth, a change of an image, a change in illuminance, a change in atmospheric pressure, a change in acceleration, respectively, or a combination of these. 
     Sensor Selection Unit  123   
     The sensor selection unit  123  selects sensors  112  to be used for movement determination of the mobile terminal apparatus  100 , that is to say, sensors for use from the plurality of sensors  112  with a trigger of the instruction from the movement determination unit  122 . Specifically, the sensor selection unit  123  selects a combination of the sensors  112  to be used for movement determination on the basis of the operation state of the sensors  112  (operation state of the mobile terminal apparatus  100 ) and a movement-determination failure rate table Ta and a power consumption table Tb. In this regard, the operation state of the sensors  112  is information of whether the individual sensors  112  are capable of sensing or not. For example, if a certain sensor  112  is in a state capable of sensing (in operation), the operation state becomes “OK”, and if the sensor  112  is in a state not capable of sensing (in a sleeping state), the operation state becomes “NG”. The sensor selection unit  123  checks the operation states of the individual sensors  112 . 
     Movement-Determination Failure Rate Table Storage Unit  124   
     A movement-determination failure rate table storage unit  124  stores the movement-determination failure rate table Ta in which movement-determination failure rates of the individual sensors  112  are described. The movement-determination failure rate is a probability of failure at the time of carrying out movement determination of the mobile terminal apparatus  100  using the individual sensors  112 . In this regard, the movement-determination failure rate is determined in advance, but may be determined in consideration of, for example, a probability of not moving in reality while determined that the sensor has moved, and a probability of determination that the sensor has not moved while the sensor has actually moved. 
       FIG. 3  is a schematic diagram of the movement-determination failure rate table Ta according to the first embodiment. 
     As illustrated in  FIG. 3 , in the movement-determination failure rate table Ta, the individual sensors  112  are tied to movement-determination failure rates. In the present embodiment, a baseband, a pedometer, and a WLAN are tied to movement-determination failure rates 0.3, 0.1, and 0.3, respectively. For example, if baseband is only used for movement determination of the mobile terminal apparatus  100 , it is understood that the movement-determination failure rate becomes 0.3. 
     Power-Consumption Table Storage Unit  125   
     A power-consumption table storage unit  125  stores the power consumption table Tb in which power consumption of the individual sensors  112  are described. The power consumption is an amount of power that is consumed when movement determination of the mobile terminal apparatus  100  is carried out using the individual sensors  112 . 
       FIG. 4  is a schematic diagram of the power consumption table Tb according to the first embodiment. 
     As illustrated in  FIG. 4 , the power consumption table Tb ties the individual sensors  112  to average power consumption for movement detection. In the present embodiment, power consumption 1 [mW], 6 [mW], and 4 [mW] are tied to the baseband, the pedometer, and the WLAN, respectively. For example, in the case of using only the baseband for movement determination of the mobile terminal apparatus  100 , the power consumption becomes 1 [mW]. 
     Positional Information Storage Unit  126   
     The positional information storage unit  126  records positional information and precision information that are obtained by positioning carried out immediately before (most recently). For the positional information, for example, longitude information and latitude information are used. However, the positional information storage unit  126  may record not only the positional information and the precision information that are obtained by the positioning immediately before, but also may tie the positional information and the precision information that are obtained by the positioning carried out before that time to positioning time. 
     Sensor Selection Processing 
       FIG. 5  is a flowchart of sensor selection processing according to the first embodiment. 
     As illustrated in  FIG. 5 , the sensor selection unit  123  obtains the operation states of all of the plurality of sensors  112  (step S 101 ) with a trigger of an instruction from the movement determination unit  122 . For the operation state, “OK”, which is capable of sensing, and “NG”, which is not capable of sensing, are defined. 
     Next, the sensor selection unit  123  selects one combination out of all the combinations of the plurality of sensors  112  (step S 102 ). For example, if there are three sensors  112 , one combination is selected from seven combinations (= 3 C 1 + 3 C 2 + 3 C 3 ). 
     Next, the sensor selection unit  123  calculates a movement-determination failure rate in the case of using all the sensors  112  of the selected combination, that is to say, a total movement-determination failure rate (step S 103 ). The total movement-determination failure rate is a probability of failure in movement determination when all the sensors  112  of the selected combination are used. Specifically, the sensor selection unit  123  calculates the total movement-determination failure rate using the following expression (1).
 
 f ( r TOTAL MOVEMENT-DETERMINATION FAILURE RATE =Π i=1   n MOVEMENT-DETERMINATION FAILURE RATE OF SENSOR i   (1)
 
     Next, the sensor selection unit  123  calculates a power-consumption evaluation value on the basis of the operation state of the sensor  112 , the total movement-determination failure rate, and the positioning power (step S 104 ). Specifically, the sensor selection unit  123  calculates the power-consumption evaluation value using the following expression (2).
 
Power-consumption evaluation value=total movement-determination failure rate×positioning power+increment of sensor power consumption  (2)
 
     In this regard, the positioning power is power to be used for positioning. In the present embodiment, it is assumed that the average positioning power is 40 [mW] on the assumption of GPS positioning. The increment of sensor power consumption is an increment of power consumption at the time of operating the sensor  112  in a sleeping state for movement determination of the mobile terminal apparatus  100 . Accordingly, the sum total power consumption of the sensors  112  in a sleeping state (operation state is “NG”) among the sensors  112  included in the selected combination becomes an increment of sensor power consumption. In this regard, in the case of using only the sensor  112  in operation for movement determination of the mobile terminal apparatus  100 , an increase of power consumption will not occur. 
     Next, the sensor selection unit  123  determines whether the total movement-determination failure rate is less than the movement-determination failure threshold value determined in advance (step S 105 ). 
     Here, if not determined that the total movement-determination failure rate is less than the movement-determination failure threshold value (No in step S 105 ), it is estimated that the probability of failure in movement determination of the mobile terminal apparatus  100  is high. Accordingly, the sensor selection unit  112  throws away the selected combination of the sensors  112 , and determines whether there is another combination of the sensors  112  or not (step S 108 ). 
     On the other hand, if determined that the total movement-determination failure rate is less than the movement-determination failure threshold value (Yes in step S 105 ), it is estimated that the probability of failure in movement determination of the mobile terminal apparatus  100  is low. Accordingly, the sensor selection unit  123  determines whether the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the power-consumption evaluation value of a use sensor candidate, which is a combination of sensors  112  having the lowest power-consumption evaluation value, and whether the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the positioning power (step S 106 ). 
     Here, if not determined that the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the power-consumption evaluation value of the combination of the sensors  112  which are use sensor candidates, and the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the positioning power (No in step S 106 ), the sensor selection unit  123  determines whether there are no combinations of the other sensors  112  or not (step S 108 ). 
     On the other hand, if determined that the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the power-consumption evaluation value of the combination of the sensors  112  which are use sensor candidates, and the power-consumption evaluation value of the selected combination of the sensors  112  is lower than the positioning power (Yes in step S 106 ), the sensor selection unit  123  stores the selected combination of the sensors  112  as a use sensor candidate (step S 107 ). 
     Next, the sensor selection unit  123  determines whether there are no other combinations of the sensors  112  or not (step S 108 ). 
     Here, if determined that there are no other combinations of the sensors  112  (Yes in step S 108 ), the sensor selection unit  123  determines whether there is a combination of the sensors  112  stored as a use sensor candidate (step S 109 ). 
     Here, if determined that there is a combination of the sensors  112  stored as a use sensor candidate (Yes in step S 109 ), the sensor selection unit  123  determines the combination of the sensors  112  stored as a use sensor candidate to be a use sensor to be used for movement determination (step S 110 ). 
     On the other hand, if not determined that there is a combination of the sensors  112  stored as a use sensor candidate (No in step S 109 ), the sensor selection unit  123  terminates the sensor selection processing. 
     Also, if not determined that there are no other combinations of the sensors  112  (No in step S 108 ), that is to say, if determined that there is the other combination of the sensors  112 , the sensor selection unit  123  selects one combination again out of all the combinations of the plurality of sensor  112  (step S 102 ). 
     In this regard, the movement determination of the mobile terminal apparatus  100  is carried out until a positioning stop request is notified from the application  130 , and the movement determination unit  122  stops the use of the sensors  112  for movement determination with a trigger of a positioning stop request. 
     SPECIFIC EXAMPLE 1 
     In the following, descriptions will be given of examples of calculation of the total movement-determination failure rate and the power-consumption evaluation value by the sensor selection unit  123  when the baseband and the WLAN are operating among the sensors  112  of the mobile terminal apparatus  100 . Here, the movement-determination failure rates and the power consumption described in the movement-determination failure rate table Ta in  FIG. 3 , and the power consumption table Tb in  FIG. 4 , respectively are used. Also, it is assumed that the movement-determination failure threshold value is 0.1, and the positioning power is 2000 [mWs]. 
     (A1) When only the baseband is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3
 
Power-consumption evaluation value=0.3×40+1=13
 
     (A2) When only the pedometer is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1
 
Power-consumption evaluation value=0.1×40+6=10
 
     (A3) When only the WLAN is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3
 
Power-consumption evaluation value=0.3×40+0=12
 
     (A4) When the baseband and the pedometer are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.1=0.03
 
Power-consumption evaluation value=0.03×40+1+6=8.2
 
     (A5) When the baseband and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.3=0.09
 
Power-consumption evaluation value=0.09×40+0=3.6
 
     (A6) When the pedometer and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1×0.3=0.03
 
Power-consumption evaluation value=0.03×40+50=7.2
 
     (A7) When the baseband, the pedometer, and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.1×0.3=0.009
 
Power-consumption evaluation value=0.009×40+6=6.36
 
     As described above, when the combination of the baseband and the WLAN is selected, it is understood that the total movement-determination failure rate becomes lower than the threshold value of the movement-determination failure rate, and the power-consumption evaluation value becomes the minimum. Accordingly, if the baseband and the WLAN are operating, the baseband and the WLAN ought to be selected as use sensors. 
     SPECIFIC EXAMPLE 2 
     In the following, descriptions will be given of examples of calculation of the total movement-determination failure rate and the power-consumption evaluation value by the sensor selection unit  123  when only the baseband is operating among the sensors  112  of the mobile terminal apparatus  100 . Here, the movement-determination failure rates and the power consumption described in the movement-determination failure rate table Ta in  FIG. 3 , and the power consumption table Tb in  FIG. 4 , respectively are also used. Also, it is assumed that the movement-determination failure threshold value is 0.1, and the positioning power is 40[mW]. 
     (B1) When only the baseband is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3
 
Power-consumption evaluation value=0.3×40+=12
 
     Baseband sensor&#39;s power-consumption is not added because baseband is operating, so already on. 
     (B2) When only the pedometer is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1
 
Power-consumption evaluation value=0.1×40+6=10
 
     (B3) When only the WLAN is selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3
 
Power-consumption evaluation value=0.3×40+4=16
 
     (B4) When the baseband and the pedometer are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.1=0.03
 
Power-consumption evaluation value=0.03×40+6=7.2
 
     (B5) When the baseband and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.3=0.09
 
Power-consumption evaluation value=0.09×50+4=7.6
 
     (B6) When the pedometer and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1×0.3=0.03
 
Power-consumption evaluation value=0.03×50+6+4=11.2
 
     (B7) When the baseband, the pedometer, and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.3×0.1×0.3=0.009
 
Power-consumption evaluation value=0.009×50+6+4=10.45
 
     As described above, when the combination of the baseband and the pedometer is selected, it is understood that the total movement-determination failure rate becomes lower than the threshold value of the movement-determination failure rate, and the power-consumption evaluation value becomes the minimum. Accordingly, if the baseband is only operating, the baseband and the pedometer ought to be selected as use sensors. 
     According to the present embodiment, a combination of the sensors  112  to be used for movement determination of the mobile terminal apparatus  100  is determined in consideration of the operation states of the individual sensors  112 , and the increments of the movement-determination failure rate and the power consumption. Accordingly, it is possible to suppress the occurrence of useless power consumption without decreasing a success rate of movement determination of the mobile terminal apparatus  100 . 
     In this regard, in the present embodiment, at the time of calculating the power-consumption evaluation value, an increment of the sensor power consumption is used. However, the present disclosure is not limited to this. For example, the power-consumption evaluation value may be calculated on the basis of only the total movement-determination failure rate×positioning power. Also, at the time of calculating the power-consumption evaluation value, sensor power consumption may be used in place of an increment of the sensor power consumption. Further, a movement-determination success rate (=1−total movement-determination failure rate) may be used in place of a total movement-determination failure rate. In the case of using a movement-determination success rate, a combination of the sensors  112  that makes the power-consumption evaluation value the greatest ought to be selected. 
     Further, in the present embodiment, operating power of a positioning device is used as positioning power. However, the present disclosure is not limited. For example, positioning power in consideration of positioning frequency may be used. For example, if an operating frequency of GPS by a positioning request from the application  130  is 1/10 of the total time period, it is thought that power consumption of the positioning device becomes 1/10 in general. Accordingly, the positioning power one-tenth of the operating power of the positioning device may be used as the positioning power. 
     Also, in the present embodiment, movement determination is carried out when the power-consumption evaluation value is less that the positioning power. However, for example, when the power-consumption evaluation value is greater than the positioning power, the movement determination may not be carried out, and positioning may be carried out all the time. 
     Also, the GPS is used as a positioning method in the present embodiment. However, the WLAN and the baseband, and so on may be used in addition. 
     Second Embodiment 
     In the following, a description will be given of a second embodiment with reference to  FIG. 6  and  FIG. 7 . Note that the descriptions will be omitted of the same configuration and functions as those of the first embodiment. 
       FIG. 6  is a schematic diagram of a movement-determination failure rate table Tc according to the second embodiment. 
     As illustrated in  FIG. 6 , the movement-determination failure rate table Tc according to the present embodiment describes a movement-determination failure rate for each combination of the sensors  112 . That is to say, the movement-determination failure rate according to the present embodiment is a probability of failure when movement determination of the mobile terminal apparatus  100  is carried out using combinations of the sensors  112 . 
       FIG. 7  is a schematic diagram of a power consumption table Td according to the second embodiment. 
     As illustrated in  FIG. 7 , in the power consumption table Td according to the present embodiment, power consumption is described for each combination of the sensors  112 . That is to say, the power consumption according to the present embodiment is an amount of power consumed when movement determination of the mobile terminal apparatus  100  is carried out using the combinations of the sensors  112 . 
     SPECIFIC EXAMPLE 
     In the following, descriptions will be given of examples of calculation of the total movement-determination failure rate and the power-consumption evaluation value by the sensor selection unit  123  when the baseband and the WLAN are operating among the sensors  112  of the mobile terminal apparatus  100 . Here, the movement-determination failure rates and the power consumption described in the movement-determination failure rate table Tc in  FIG. 6  and the power consumption table Td in  FIG. 7  are used, respectively. Also, it is assumed that the movement-determination failure threshold value is 0.1, and the positioning power is 40 [mW]. 
     (C1) When the baseband and the WLAN are selected as a combination of the sensors  112 , the movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Movement-determination failure rate=0.12
 
Power-consumption evaluation value=0.12×40+(5−5)=240
 
     (C2) When the baseband, the pedometer, and the WLAN are selected as a combination of the sensors  112 , the movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Movement-determination failure rate=0.01
 
Power-consumption evaluation value=0.01×40+(11−5)=320
 
     (C3) When the baseband, the pedometer, the Bluetooth, and the WLAN are selected as a combination of the sensors  112 , the movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Movement-determination failure rate=0.08
 
Power-consumption evaluation value=0.08×40+(7−5)=260
 
     Here, only three kinds of combinations of the sensors  112  are described. However, the other combinations ought to be calculated in the same manner. 
     As described above, when the combination of the baseband, the Bluetooth, and the WLAN is selected, it is understood that the movement-determination failure rate becomes lower than the threshold value of the movement-determination failure rate, and the power-consumption evaluation value becomes the minimum. Accordingly, if the baseband and the WLAN are operating, the combination of the baseband, the Bluetooth, and the WLAN ought to be selected as use sensors. 
     In this regard, here, although the Bluetooth in a sleeping state is started, the power-consumption evaluation value is low. This is because the Bluetooth and the WLAN are packaged in a combo chip. In this manner, for example, depending on a packaging state, a difference sometimes occurs between the power-consumption evaluation value of a combination of a plurality of sensors  112  and the power-consumption evaluation value calculated by the movement-determination failure rates of the individual sensors  112 . However, by the present embodiment, it is possible to calculate more precise power-consumption evaluation value. 
     Third Embodiment 
     In the following, a description will be given of a third embodiment with reference to  FIGS. 8 to 10 . Note that descriptions will be omitted of the same configuration and functions as those of the first embodiment. 
     Functional Blocks of Mobile Terminal Apparatus  100 M 
       FIG. 8  is a schematic diagram of the functional blocks of the mobile terminal apparatus  100 M according to the third embodiment. 
     As illustrated in  FIG. 8 , the movement determination unit  122  according to the present embodiment includes a movement-state estimation unit  127 . The movement-state estimation unit  127  estimates whether the movement state of the mobile terminal apparatus  100 M (of the user) is a walking state or an in-vehicle state on the basis of the detection result by the sensor  112  and the determination result by the movement determination unit  122 . For example, although there is no change in the count value (the number of steps) of the pedometer in operation, if determined as “have moved”, it is estimated that the user of the mobile terminal apparatus  100 M is in a vehicle. The movement-state estimation unit  127  holds movement states as the individual state probabilities estimated from the sensors  112 . For example, the movement-state estimation unit  127  holds the probability that the movement state of the user is walking as a walking-state probability, and the probability that the movement state of the user is in a vehicle as an in-vehicle state probability. 
     The sensor selection unit  123  according to the present embodiment selects sensors  112  to be used for movement determination of the mobile terminal apparatus  100 M, that is to say, sensors for use from the plurality of sensors  112  on the basis of the estimation result by the movement-state estimation unit  127  and the movement-determination failure rate table Te. 
     Specifically, the sensor selection unit  123  calculates the total movement-determination failure rate on the basis of the walking-state probability and the in-vehicle state probability that are determined by the movement-state estimation unit  127  for each estimation result using the following expression (3). 
     
       
         
           
             
               
                 
                   
                     TOTAL 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     MOVEMENT 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     DETERMINATION 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     FAILURE 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     RATE 
                   
                   = 
                   
                     
                       WALKING 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       STATE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       PROBABILITY 
                       × 
                       
                         
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                             i 
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                           n 
                         
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                           MOVEMENT 
                           ⁢ 
                           
                             - 
                           
                           ⁢ 
                           DETERMINATION 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           FAILURE 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           RATE 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           OF 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             SENSOR 
                             i 
                           
                         
                       
                     
                     + 
                     
                       IN 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       VEHICLE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       STATE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       PROBABILITY 
                       × 
                       
                         
                           ∏ 
                           
                             i 
                             = 
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                           n 
                         
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                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           MOVEMENT 
                           ⁢ 
                           
                               
                             
                                 
                             
                             ⁢ 
                             
                               
                                 - 
                               
                               ⁢ 
                               DETERMINATION 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 
 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               FAILURE 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               RATE 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               OF 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 SENSOR 
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                   ( 
                   3 
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     Note that if it is difficult to estimate the movement state, both of the walking-state probability and the in-vehicle state probability are set to 0.5. 
     Further, the sensor selection unit  123  calculates the power-consumption evaluation value on the basis of the total movement-determination failure rate using the above-described expression (2). 
     And the sensor selection unit  123  selects a combination of the sensors  112  to be used for movement determination of the mobile terminal apparatus  100 M on the basis of the operation states of the sensors  112  (the operation state of the mobile terminal apparatus  100 M), the total movement-determination failure rate, and the power-consumption evaluation value. 
       FIG. 9  is a schematic diagram of the movement-determination failure rate table Te according to the third embodiment. 
     As illustrated in  FIG. 9 , the movement-determination failure rate table Te according to the present embodiment describes a each movement-determination failure rate of each of the sensors  112  for each movement state. For example, in the case of the pedometer, the movement-determination failure rate at the time of walking is set to 0.05, and the movement-determination failure rate at the time of in-vehicle is set to 0.8. A pedometer is suitable for movement detection in a walking state, but is not suitable for movement detection in an in-vehicle state, and thus the movement-determination failure rate at the time of walking is set to low, and the movement-determination failure rate at the time of in-vehicle is set to high. 
     Sensor Update Processing 
       FIG. 10  is a flowchart of sensor update processing according to the third embodiment. 
     As illustrated in  FIG. 10 , first, the sensor selection unit  123  performs sensor selection processing according to the first embodiment using the expression (3) in place of the expression (1) (step S 201 ). Here, it is assumed that both of the walking-state probability and the in-vehicle state probability are set to 0.5 on the assumption that it is difficult to estimate the movement state. 
     Next, the movement determination unit  122  carries out the movement determination of the mobile terminal apparatus  100 M using the sensors  112  selected by the sensor selection unit  123  (step S 202 ). 
     Next, the movement-state estimation unit  127  obtains positional information from the positioning driver  140  or the positional information storage unit  126  on the basis of the result of the movement determination, notifies the positional information to the application  130 , and further, determines whether it has bee possible to estimate movement state of the mobile terminal apparatus  100 M or not (step S 203 ). 
     Here, if not determined that it has bee possible to estimate the movement state (No in step S 203 ), the movement-state estimation unit  127  terminates the sensor update processing without updating the sensors  112  to be used for the movement determination of the mobile terminal apparatus  100 M. 
     On the other hand, if determined that it has bee possible to estimate the movement state (Yes in step S 203 ), the movement-state estimation unit  127  obtains the walking-state probability and the in-vehicle state probability that are tied to the movement state as an estimation result (step S 204 ). In the present embodiment, it is assumed that in-vehicle state is estimated, and thus the walking-state probability is 0.1, and the in-vehicle state probability is 0.9. 
     Next, the sensor selection unit  123  calculates the total movement-determination failure rate on the basis of the walking-state probability and the in-vehicle state probability that are obtained by the movement-state estimation unit  127  using the above-described expression (3) (step S 205 ). 
     Next, the sensor selection unit  123  calculates the power-consumption evaluation value on the basis of the total movement-determination failure rate using the above-described expression (2) (step S 206 ). 
     Next, the sensor selection unit  123  determines whether a newly calculated power-consumption evaluation value is less than the power-consumption evaluation value calculated immediately before (most recently) or not (step S 207 ). 
     Here, if not determined that the newly calculated power-consumption evaluation value is less than the power-consumption evaluation value calculated immediately before (No in step S 207 ), the sensor selection unit  123  terminates the sensor update processing without updating the sensors  112  to be used for the movement determination of the mobile terminal apparatus  100 M. 
     On the other hand, if determined that the newly calculated power-consumption evaluation value is less than the power-consumption evaluation value calculated immediately before (Yes in step S 207 ), the sensor selection unit  123  updates the sensors  112  to be used for the movement determination to newly selected sensors  112  (step  208 ). 
     Specific Example 1 in the Case that Estimation of Movement State is not Possible 
     In the following, descriptions will be given of examples of calculation of the total movement-determination failure rate and the power-consumption evaluation value by the sensor selection unit  123  when the baseband and the WLAN are operating among the sensors  112  of the mobile terminal apparatus  100 M. Here, the movement-determination failure rates described in the movement-determination failure rate table Te in  FIG. 9  are used. Also, it is assumed that the movement-determination failure threshold value is 0.1, and the positioning power is 40 [mW]. In the present specific example 1, it is assumed that estimation of movement state is not possible, and thus both of the movement state walking-state probability and the in-vehicle state probability are 0.5. 
     (D1) When the baseband and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.5×(0.8×0.5)+0.5×(0.2×0.1)=0.21
 
Power-consumption evaluation value=0.21×40+4=26
 
     (D2) When the baseband, the pedometer, and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.5×(0.8×0.05×0.5)+0.5(0.2×0.8×0.1)=0.018
 
Power-consumption evaluation value=0.018×40+6=
 
     As described above, in the case that estimation of movement state is not possible, when the combination of the baseband, the pedometer, and the WLAN is selected, it is understood that the movement-determination failure rate becomes lower than the threshold value of the movement-determination failure rate, and the power-consumption evaluation value becomes the minimum. Accordingly, if the baseband and the WLAN are operating, and estimation of movement state is not possible, the combination of the baseband, the pedometer, and the WLAN ought to be selected as use sensors. 
     Specific Example 2 in the Case that Estimation of Movement State was possible 
     In the following, descriptions will be given of examples of calculation of the total movement-determination failure rate and the power-consumption evaluation value by the sensor selection unit  123  when the baseband and the WLAN are operating among the sensors  112  of the mobile terminal apparatus  100 M. Here, the movement-determination failure rates described in the movement-determination failure rate table Te in  FIG. 9  are used. Also, it is assumed that the movement-determination failure threshold value is 0.1, and the positioning power is 2000 [mWs]. In the present specific example 2, it is assumed that estimation of movement state has been possible, and thus the walking-state probability is 0.1, and the in-vehicle state probability is 0.9. 
     (E1) When the baseband and the WLAN are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1×(0.8×0.5)+0.9×(0.2×0.1)=0.058
 
Power-consumption evaluation value=0.058×40+0=2.32
 
     (E2) When the baseband and the pedometer are selected as a combination of the sensors  112 , the total movement-determination failure rate and the power-consumption evaluation value become as follows.
 
Total movement-determination failure rate=0.1×(0.8×0.05×0.5)+0.9(0.2×0.8×0.1)=0.0164
 
Power-consumption evaluation value=0.0164×40+6=8.98
 
     As described above, in the case that estimation of movement state is possible, when the combination of the baseband, and the WLAN is selected, it is understood that the movement-determination failure rate becomes lower than the threshold value of the movement-determination failure rate, and the power-consumption evaluation value becomes the minimum. Accordingly, if the baseband and the WLAN are operating, and estimation of movement state is possible, the combination of the baseband and the WLAN ought to be selected as use sensors. 
     By the present embodiment, a combination of the sensors  112  to be used for movement determination is selected in consideration of the movement state of the mobile terminal apparatus  100 M. Accordingly, it is possible to carry out movement determination in accordance with the movement state of the mobile terminal apparatus  100 M. As a result, it is possible to suppress the occurrence of useless power consumption further. 
     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.