Patent Publication Number: US-9837049-B2

Title: Visible light communication system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on and claims priority of Japanese Patent Application No. 2014-155588 filed on Jul. 30, 2014. The entire disclosure of the above-identified application, including the specification, drawings and claims is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to visible light communication systems, and in particular, to a visible light communication system which allows pairing in wireless communication between an information terminal and an information presentation apparatus to be performed using visible light. 
     2. Description of the Related Art 
     A light communication (visible light communication) technique is currently available in which visible light emitted from an illumination device is modulated for data transmission and a receiver receives the visible light and decodes the data from the modulated visible light. Wireless communication requires a dedicated device. In contrast, visible light communication using illumination does not require a dedicated device because an illumination device, which is normally installed inside a building, serves two functions of illumination and communication. Accordingly, the visible light communication has advantages in that interior design can be given consideration, a range illuminated by visible light is visible, and communication can be established in a limited space or area. The visible light communication can be mainly used in, for example, location-based services provided inside buildings, where radio waves of the global positioning system (GPS) are unlikely to be provided, by causing each illumination device to emit location information as data. 
     In a space such as an office, a conference room, or a public facility, it may be desired that content in an information terminal held by a user is output to an information presentation apparatus (for example, a speaker, a television (TV), a projector, a printer, and an electronic whiteboard) located away from the user in the same space. In such a case, connection information of each information presentation apparatus in the wireless network, to which the information presentation apparatus is connected, is obtained, and the connection information (internet protocol (IP) address, service set identifier (SSID), and password in the case of wireless fidelity (Wi-Fi)) is input to the information terminal of the user for wireless network connection. Accordingly, pairing between the information terminal and the information presentation apparatus is performed in wireless communication, allowing the content in the information terminal to be transmitted to the information presentation apparatus for output or display. Additionally, the pairing allows the information terminal to remotely control the information apparatuses. In order to facilitate convenience, when communication is to be established between two apparatuses, the connection information of one of the apparatuses is desirably input to the other apparatus easily. The term “pairing” refers to a process in which apparatuses which communicate with each other in wireless communication register links to one another. 
     For example, Japanese Unexamined Patent Application Publication No. 2009-124581 (hereinafter, referred to as PTL 1) discloses a method of establishing a connection between apparatuses, by pairing a remote controller with a TV to be controlled by the remote controller. 
     According to the technique disclosed in PTL 1, in a wireless control apparatus including a TV and a remote controller which wirelessly controls the TV, the remote controller is turned on. The remote controller then outputs a connection request packet to the photodiode in the TV using an infrared light-emitting diode (LED) and simultaneously performs pairing in wireless communication. On the other hand, upon receipt of the light of the connection request packet, the TV performs pairing in wireless communication. 
     SUMMARY OF THE INVENTION 
     The conventional technique disclosed in PTL 1 is directed to pairing performed between specific apparatuses which are the remote controller and the TV. Hence, the infrared rays from the remote controller need to be directed to the photodiode in the TV. In other words, the operator is required to know the location of the TV. Moreover, the remote controller which has been paired with the TV is capable of controlling TV even from a relatively distant location (for example, from a room which is next to, above, or below the current room and separated by a wall from the current room). Hence, the remote controller is capable of changing channels even when another person is using the TV. Additionally, the TV (an apparatus to be controlled) needs to include a dedicated function (photodiode, demodulating unit and the like) for receiving a signal from the infrared LED of the remote controller. The conventional technique in PTL 1 is thus not applicable to an existing apparatus to be controlled. 
     The present disclosure has been conceived to solve such a conventional problem. An object of the present disclosure is to provide a visible light communication system which performs pairing between an information terminal and an information presentation apparatus. The pairing is performed while requiring the information presentation apparatus to include a wireless communication function instead of a dedicated function, and without requiring a dedicated operation for pairing in wireless communication. 
     In order to achieve the above object, a visible light communication system according to one aspect of the present disclosure includes: an illumination device which emits visible light including identification information identifying the illumination device, and performs communication using the visible light; an information presentation apparatus which presents information to a person in a range illuminated by the visible light; an information terminal which receives the identification information included in the visible light; and an information recording medium which holds pairing information associating the identification information identifying the illumination device with connection information required for connection via wireless communication with the information presentation apparatus, in which when the information terminal is illuminated by the visible light, the information terminal refers to the pairing information held in the information recording medium to identify the connection information associated with the identification information included in the visible light, and establishes connection with the information presentation apparatus based on the connection information identified. 
     The visible light communication system according to an aspect of the present disclosure performs pairing between an information terminal and an information presentation apparatus while requiring the information presentation apparatus to include a wireless communication function instead of a dedicated function, and without requiring a dedicated operation for pairing in wireless communication. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The figures depict one or more implementations in accordance with the present teaching, by way of examples only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
         FIG. 1  illustrates a configuration of a visible light communication system according to Embodiment 1; 
         FIG. 2  illustrates a structure of pairing information according to Embodiment 1; 
         FIG. 3  is a flowchart of operations in the visible light communication system according to Embodiment 1; 
         FIG. 4  illustrates a configuration of a visible light communication system according to Embodiment 2; 
         FIG. 5  is a flowchart of operations in the visible light communication system according to Embodiment 2; 
         FIG. 6  illustrates a configuration of a visible light communication system according to Embodiment 3; 
         FIG. 7  illustrates a structure of pairing information according to Embodiment 3; 
         FIG. 8  is a flowchart of operations in the visible light communication system according to Embodiment 3; 
         FIG. 9  illustrates an example of a screen display of an information terminal according to Embodiment 3; 
         FIG. 10  illustrates a configuration of a visible light communication system according to Embodiment 4; and 
         FIG. 11  illustrates a structure of pairing information according to Embodiment 4. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following describes embodiments in detail with reference to the drawings as appropriate. 
     It is to be noted that each of the embodiments described below shows a specific example of the present disclosure. The numerical values, structural elements, the arrangement and connection of the structural elements, steps, the processing order of the steps etc., shown in the following embodiments are mere examples and do not restrict the present disclosure. Furthermore, among the structural elements in the following embodiments, structural elements not recited in the independent claims each indicating the broadest concept are described as arbitrary structural elements. 
     (Embodiment 1) 
       FIG. 1  illustrates a configuration of a visible light communication system according to Embodiment 1. 
     Visible light communication system  1  is a system in which pairing in wireless communication between information terminal  103  and information presentation apparatus  102  is automatically performed using visible light. Visible light communication system  1  includes illumination device  101 , information presentation apparatus  102 , and information terminal  103 . Illumination device  101  performs communication using visible light. Illumination device  101  emits visible light including identification information identifying illumination device  101 . Information presentation apparatus  102  presents information to a person or people in a range illuminated by the visible light emitted from illumination device  101 . Information terminal  103  receives the identification information included in the visible light emitted from illumination device  101 . 
     Illumination device  101  which emits visible light may be an illumination device which emits light of another wavelength such as infrared light, or a projector. Information presentation apparatus  102  is an apparatus which presents information, such as a speaker, a projector, a TV, a digital signage, an electronic whiteboard, a printer, and an illumination device. The information presented by information presentation apparatus  102  include not only video, image, audio, and text, but also light provided by the illumination device. This is to allow information terminal  103  to perform, for example, dimming or color adjustment on the illumination device. The expression “information presentation apparatus  102  presents information to a person or people in a range illuminated by the visible light” includes a meaning that information presentation apparatus  102  is located at a position where a person in the range illuminated by the visible light can directly view or hear information”. For example, the expression includes a case where information presentation apparatus  102  is located in an area near the range illuminated by the visible light. Examples of the area near the range illuminated by the visible light include a room or a building in which illumination device  101  is located and which is surrounded by a door or a wall, an area divided by a partition, a private room in a restaurant, an area where each exhibit is present in a museum or an art museum. 
     Hereinafter, detailed configurations of illumination device  101 , information presentation apparatus  102 , and information terminal  103  will be described. 
     Illumination device  101  includes a light source (for example, LED), a power circuit which supplies power to the light source, and a visible light communication transmitter which modulates light and superimpose a signal on the modulated light (not illustrated). A signal (visible light communication signal, here, identification information) transmitted by illumination device  101  through visible light communication is, for example, a digital signal having a fixed length predetermined to illumination device  101 . The visible light communication transmitter of illumination device  101  turns on the output of the power circuit (supplies power) or turns off the output of the power circuit (supplies no power) according to the value (1 or 0) of the digital signal so that the signal is superimposed on the illumination light. Examples of the digital signal include 128-bit ucode standardized by international telecommunication union (ITU). Illumination device  101  is generally fixed in a space, and thus, assignment of the ucode to illumination device  101  is convenience because the ucode is used as location information of each item. In the present embodiment, location information is used as an example of the identification information identifying illumination device  101 . The identification information identifying illumination device  101  is also referred to as location information in the following description. 
     Information terminal  103  is capable of performing communication using visible light. Information terminal  103  includes visible light communication receiver  104 , communication unit  105 , information recording medium  106 , display unit  107 , input unit  108 , and controller  109 . Visible light communication receiver  104  is a circuit which receives and decodes the signal of visible light communication transmitted from illumination device  101 . Communication unit  105  is a communication interface for communicating with information presentation apparatus  102 . Information recording medium  106  holds pairing information associating the identification information identifying illumination device  101  (location information in Embodiment 1) with connection information required for connection via wireless communication with information presentation apparatus  102 . In Embodiment 1, information recording medium  106  holds content to be reproduced by information presentation apparatus  102 , application programs and the like, in addition to the pairing information required for the network connection with information presentation apparatus  102 . Display unit  107  displays an operation graphical user interface (GUI). Input unit  108  is an input device for operation. Controller  109  is a circuit for controlling operations of information terminal  103 , and, for example, includes a nonvolatile memory storing programs, a volatile working memory, a timer counter, and a processor which executes programs. Examples of information terminal  103  include a smart phone, a tablet, and a notebook computer. However, information terminal  103  is not limited to the above examples, but may be a dedicated terminal. 
     Information presentation apparatus  102  presents information using video, images, printed materials, sound, light, and the like (or provides light), and includes communication unit  110 , controller  111 , and information presentation unit  112 . Communication unit  110  is a communication interface for communicating with communication unit  105  of information terminal  103 . Information presentation unit  112  is an output unit which outputs the content transmitted from information terminal  103  and the like. Controller  111  is a circuit for controlling operations of information presentation apparatus  102 , and includes, for example, a nonvolatile memory storing programs, a volatile working memory, and a processor which executes programs. Examples of information presentation apparatus  102  include a speaker, a projector, a TV, a digital signage, an electronic whiteboard, a printer, an illumination device, and an information terminal such as a personal computer (PC) each of which includes a network function (wireless communication function). 
     Referring to  FIG. 2 , pairing information held in information recording medium  106  will be described. Pairing information  201  is information which associates the identification information identifying illumination device  101  (location information in Embodiment 1) with connection information required for connection via wireless communication with information presentation apparatus  102 . In Embodiment 1, pairing information is generated for each piece of location information (pairing information 1 to m in (a) of  FIG. 2 ). Each piece of pairing information  201  includes location information  202  of corresponding illumination device  101 , and network connection information  203  for connecting with information presentation apparatus  102  connectable near an area where a visible light communication signal from illumination device  101  can be received. Here, the term “network” refers to a communication network. Examples of the network include various networks such as Wi-Fi and Bluetooth (registered trademark). Network connection information  203  is connection information required for connection via wireless communication, and is, for example, an SSID, a security password, and an IP address in the case of Wi-Fi. Network connection information  203  is a model name (or a media access control (MAC) address), and a password of information presentation apparatus  102  in the case of Bluetooth (registered trademark). A plurality of information presentation apparatuses  102  which are connectable may be placed in the same space region (for example, in the same room). Such a case will be later described in Embodiment 3. In Embodiment 1, location information  202  and information presentation apparatus  102  are in a one-to-one correspondence (one information presentation apparatus  102  is associated with one piece of location information  202 ). An example of such a configuration is a case where a predetermined interpretive sound is output from a speaker (information presentation apparatus  102  which is connected via Bluetooth (registered trademark)) placed near an exhibit in a museum or an art museum. 
     Referring to the flowchart in  FIG. 3 , operations in visible light communication system  1  according to Embodiment 1 will be described.  FIG. 3  illustrates a flow of operations of information terminal  103 . 
     First, in Step S 301 , when information terminal  103  is started, controller  109  resets the internal timer counter and causes the timer counter to start counting up. In Step S 302 , visible light communication receiver  104  attempts to decode a visible light communication signal (location information) transmitted from illumination device  101 . In Step S 303 , controller  109  determines whether or not visible light communication receiver  104  has successfully received location information  202 . When location information  202  has been successfully received, controller  109  resets the timer counter to 0 in Step S 304 . In Step S 305 , controller  109  reads, based on received location information  202 , network connection information  203  associated with received location information  202  from pairing information  201  in information recording medium  106 . Subsequently, in Step S 306 , controller  109  determines whether or not connection with the apparatus indicated by read network connection information  203  (that is, information presentation apparatus  102 ) has been established. When the connection has been established, the processing returns to Step S 302 . When the connection has not been established, controller  109  establishes connection with information presentation apparatus  102  based on read network connection information  203  in Step S 307 . In Step S 308 , controller  109  sets the output destination of sound and video of information terminal  103  to information presentation apparatus  102  with which the connection has been established. 
     On the other hand, when the location information has not been received in Step S 303 , controller  109  determines in Step  309  whether or not the timer counter indicates a lapse of a predetermined time period (for example, five minutes). In Embodiment 1, the predetermined time period is five minutes, but the present disclosure is not limited to the example. The location information is not received successfully, for example, when information terminal  103  is out of the range illuminated by the visible light emitted from illumination device  101 . Specific examples of the case where information terminal  103  is out of the range include a case where information terminal  103  is located in the shade of another object relative to the visible light emitted from illumination device  101 , information terminal  103  is shielded by another object covering information terminal  103 , or information terminal  103  leaves the range illuminated by visible light. 
     If five minutes have passed since the time counter was rest, controller  109  disconnects network connection from (cancels pairing with) information presentation apparatus  102  in Step  310 , and resets the timer counter in Step  311 . If five minutes have not passed since the time counter was reset, controller  109  returns to Step  302 . 
     As described above, in the present embodiment, when information terminal  103  is illuminated by visible light, information terminal  103  refers to pairing information held in information recording medium  106  to identify connection information associated with the location information included in the visible light, and establishes connection with information presentation apparatus  102  based on the identified connection information. In other words, when information terminal  103  enters the range illuminated by illumination device  101  and receives location information, information terminal  103  is automatically connected to predetermined information presentation apparatus  102  placed near an area illuminated by visible light emitted by illumination device  101 . Accordingly, pairing between information terminal  103  and information presentation apparatus  102  is performed while requiring information presentation apparatus  102  to include a wireless communication function instead of a dedicated function, and without requiring a dedicated operation for pairing in wireless communication. As a result, for example, information terminal  103  can output content to information presentation apparatus  102  placed near information terminal  103   c , or information terminal  103  can operate information presentation apparatus  102 . 
     When information terminal  103  leaves the range illuminated by visible light, information terminal  103  disconnects from information presentation apparatus  102 . Accordingly, connection between information terminal  103  with information presentation apparatus  102  is established only when information terminal  103  is in the range illuminated by visible light. Hence, it is possible to prevent another information terminal located outside the range illuminated by the visible light from connecting with information presentation apparatus  102 . 
     Here, when information terminal  103  is continuously out of the range illuminated by visible light for a predetermined period, information terminal  103  disconnects from information presentation apparatus  102 . This prevents chattering phenomenon in which information terminal  103  and information presentation apparatus  102  are repeatedly connected and disconnected when information terminal  103  is near a border of the range illuminated by visible light. 
     In Embodiment 1, information terminal  103  includes display unit  107  and input unit  108 , but these units are unnecessary if predetermined content is to be reproduced. 
     (Embodiment 2) 
     In Embodiment 1, pairing information is held in information recording medium  106  in information terminal  103 , but the present disclosure is not limited to this example. The pairing information may be held in server  402  on the network. 
       FIG. 4  illustrates a configuration of visible light communication system  2  according to Embodiment 2. 
     Visible light communication system  2  is a system in which pairing in wireless communication between information terminal  103   a  and information presentation apparatus  102  is automatically performed using visible light. Visible light communication system  2  includes illumination device  101 , information presentation apparatus  102 , information terminal  103   a , and server  402 . In Embodiment 2, illumination device  101  and information presentation apparatus  102  are approximately the same as those in Embodiment 1, and thus, the descriptions thereof are not given. The same reference numerals are assigned to the structural elements which are included in information terminal  103   a  and approximately the same as those in Embodiment 1, and the descriptions thereof are not given. 
     Information terminal  103   a  is capable of performing communication using visible light. Information terminal  103   a  includes visible light communication receiver  104 , communication unit  105 , information recording medium  106   a , display unit  107 , input unit  108 , controller  109   a , and network (NW) communication unit  401 . NW communication unit  401  is a communication interface for communicating with server  402 . In Embodiment 2, information recording medium  106   a  holds no pairing information, but holds content to be reproduced by information presentation apparatus  102 , applications, and the like. Controller  109   a  is a circuit for controlling operations of information terminal  103   a , and, for example, includes a nonvolatile memory storing programs, a volatile working memory, a timer counter, and a processor which executes programs. 
     Server  402  is an apparatus which provides pairing information to information terminal  103   a , and includes NW communication unit  403 , controller  404 , and information recording medium  405 . Information recording medium  405  is a recording medium which holds pairing information associating identification information identifying illumination device  101  (location information in Embodiment 2) with connection information of information presentation apparatus  102 . In other words, information recording medium  405  holds pairing information required for network connection (wireless connection) of information presentation apparatus  102 . NW communication unit  403  is a communication interface for communicating with information terminal  103   a . Controller  404  is a circuit for controlling operations of server  402 , and includes, for example, a nonvolatile memory storing programs, a volatile working memory, and a processor which executes programs. Server  402  may be, for example, a PC, and may be placed distant from information terminal  103   a  and information presentation apparatus  102  as long as server  402  is connected to the network. 
     NW communication unit  401  of information terminal  103   a  and NW communication unit  403  of Server  402  are communication interfaces which can use public mobile phone network, internet network via Wi-Fi, and the like. When network connecting information terminal  103   a  and information presentation apparatus  102  is the same type of network as network connecting information terminal  103   a  and server  402  (for example, Wi-Fi), the following is possible. Specifically, information terminal  103   a  can share communication unit  105  and NW communication unit  401 , which eliminates the need for one of communication unit  105  and NW communication unit  401  (for example, NW communication unit  401  is unnecessary). 
     Referring to the flowchart in  FIG. 5 , operations in visible light communication system  2  according to Embodiment 2 will be described.  FIG. 5  illustrates a flow of operations of information terminal  103   a.    
     First, in Step  501 , when information terminal  103   a  is started, controller  109   a  resets the internal timer counter and causes the timer counter to start counting up, and deletes last pairing information. In Step  502 , visible light communication receiver  104  attempts to decode a visible light communication signal (location information) transmitted from illumination device  101 . In Step  503 , controller  109   a  determines whether or not visible light communication receiver  104  has successfully received location information. When location information has been successfully received, controller  109   a  resets the timer counter to 0 in Step  504 . In Step  505 , controller  109   a  determines whether or not the currently received location information is the same as the last location information (held as the last pairing information). When the result of the determination indicates that the currently received location information is different from the last location information, controller  109   a  requests, in Step  506 , server  402  to search information recording medium  405  for pairing information associated with the currently received location information. Specifically, controller  109   a  queries network connection information  203  associated with currently received location information  202 , and, in Step  507 , establishes connection with information presentation apparatus  102  based on network connection information  203  obtained as a result of the query. In Step  508 , controller  109   a  sets the output destination of sound and video of information terminal  103   a  to information presentation apparatus  102  with which the connection has been established. In Step  509 , controller  109   a  stores pairing information (the currently received location information and the network connection information of the information presentation apparatus with which the connection has been established) as last pairing information. 
     On the other hand, when the currently received location information is the same as the last location information in Step  505 , controller  109   a  determines in Step  510  whether or not the connection with the apparatus of network connection information  203  (that is, information presentation apparatus  102 ) is still connected. When the connection is determined to be still connected, controller  109   a  returns to Step  502 , and when the connection is determined not to be connected, controller  109   a  executes Step  506  to Step  509 . 
     When the location information has not been successfully received in Step  503 , controller  109   a  determines in Step  511  whether or not the timer counter indicates that a predetermined time period (for example, five minutes) has passed. When the timer counter indicates that five minutes have passed since the timer counter was reset, controller  109   a  disconnects network connection from (cancels pairing with) information presentation apparatus  102  in Step  512 , and resets the timer counter in Step  513 . When five minutes have not passed since the time counter was reset, controller  109   a  deletes the last pairing information in Step  514 , and returns to Step  502 . 
     With such operations, when information terminal  103   a  enters the range illuminated by illumination device  101  and receives location information as described above, information terminal  103   a  is automatically connected to predetermined information presentation apparatus  102  placed near an area illuminated by visible light emitted from illumination device  101 . In other words, pairing between information terminal  103   a  with information presentation apparatus  102  is performed while requiring information presentation apparatus  102  to include a wireless communication function instead of a dedicated function, and without requiring a dedicated operation for pairing in wireless communication. As a result, for example, information terminal  103   a  can output content to information presentation apparatus  102  placed near information terminal  103   a , or information terminal  103   a  can operate information presentation apparatus  102 . 
     In Embodiment 2, the pairing information is held in server  402  instead of information terminal  103   a . Hence, editing the pairing information in server  402  facilitates change to pairing between information terminal  103   a  and information presentation apparatus  102 . As a result, the pairing information is centrally controlled, leading to increase in efficiency. 
     Moreover, in Embodiment 2, the latest pairing information is held in information terminal  103   a . This avoids unnecessary query sent to server  402  on the network, leading to reduced communication traffic. 
     (Embodiment 3) 
     Embodiment 1 and Embodiment 2 describe the case where there is one information presentation apparatus  102 , but in practice, a plurality of information presentation apparatuses may exist. In Embodiment 3, a user can select an information presentation apparatus to which an information terminal outputs information, from among a plurality of information presentation apparatuses. 
       FIG. 6  illustrates a configuration of visible light communication system  3  according to Embodiment 3. 
     Visible light communication system  3  is a system in which pairing in wireless communication between information terminal  103   b  and information presentation apparatuses  102   a  to  102   c  is automatically performed using visible light. Visible light communication system  3  includes illumination device  101 , information presentation apparatuses  102   a  to  102   c , and information terminal  103   b.    
     In Embodiment 3, illumination device  101  and information presentation apparatuses  102   a  to  102   c  respectively have approximately the same configurations as those of illumination device  101  and information presentation apparatus  102  according to Embodiment 1. Hence, the descriptions of illumination device  101  and information presentation apparatuses  102   a  to  102   c  according to Embodiment 3 are not given. The same reference numerals are assigned to the structural elements which are included in information terminal  103   b  and approximately the same as those in Embodiment 1, and the descriptions thereof are not given. 
     Information terminal  103   b  is capable of performing communication using visible light. Information terminal  103   b  includes visible light communication receiver  104 , communication unit  105 , information recording medium  106   b , display unit  107 , input unit  108 , and controller  109   b . Information recording medium  106   b  is a recording medium which holds pairing information associating the identification information identifying illumination device  101  and a plurality of pieces of connection information required for connection in wireless communication with information presentation apparatuses  102   a  to  102   c . In Embodiment 3, information recording medium  106   b  holds pairing information associating the location information of one illumination device  101  with a plurality of pieces of connection information required for connection in wireless communication with information presentation apparatuses  102   a  to  102   c . Controller  109   b  is a circuit for controlling operations of information terminal  103   b , and, for example, includes a nonvolatile memory storing programs, a volatile working memory, a timer counter, and a processor which executes programs. It is assumed that information terminal  103   b  is a smart phone, and a processing program executed by controller  109   b  is given by an application downloaded from the internet or the like. 
     Information presentation apparatuses  102   a  to  102   c  associated with one illumination device  101  by pairing information are information presentation apparatuses belonging to one group, such as information presentation apparatuses of the same type or different types placed in the same room. 
       FIG. 7  illustrates a structure of the pairing information held in information recording medium  106   b . Pairing information  201  is provided for each piece of location information transmitted from illumination device  101  (pairing information  1  to m in (a) of  FIG. 7 ). Each piece of pairing information  201  includes corresponding location information  202  and a plurality of pieces of information presentation apparatus information  701  (location information m and information presentation apparatus information M 1  to m 5  in (b) of  FIG. 7 ). Each piece of information presentation apparatus information  701  includes network connection information  203  and identification information  702  such as the name of an information presentation apparatus ((c) of  FIG. 7 ). Information presentation apparatuses  102   a  to  102   c  each output certain details or types of content. For example, a speaker can output only sound information, and a TV, a projector and the like can output sound and video (moving pictures and still images). 
     An application is downloaded to information terminal  103   b  via a mobile telephone network or Wi-Fi, held in information recording medium  106   b , and executed by controller  109   b . Alternatively, the application may be constantly executed as a resident software, or activated by a user operation. Here, the application is assumed to be constantly executed as a resident software. Moreover, the application implements programs (software) corresponding to the processing in the flowcharts illustrated in  FIG. 3 ,  FIG. 5 , and  FIG. 8  and pairing information. For security purpose, the application is desirably operable only when location information is received from illumination device  101 . Specifically, it is desirable that the application is operable under the location information which matches the location information included in the pairing information. Accordingly, the application is executable only under illumination device  101  which permits the operation of the application. 
     A description will be given of operations in visible light communication system  3  according to Embodiment 3 in such a situation, with reference to the flowchart in  FIG. 8 .  FIG. 8  illustrates a flow of operations of information terminal  103   b.    
     First, after an application is started, controller  109   b  resets the timer counter and causes the timer counter to start counting up in Step  801 . In Step  802 , visible light communication receiver  104  attempts to decode a visible light communication signal (location information) transmitted from illumination device  101 . In Step  803 , controller  109   b  determines whether or not the location information has been successfully received. When the location information has been successfully received, controller  109   b  resets the timer counter to 0 in Step  804 , and obtains pairing information based on the location information in Step  805 . Controller  109   b  determines in Step  806  whether or not connection has been established with any one of information presentation apparatuses associated with the information presentation apparatus information included in the pairing information. When the result of the determination indicates that there is no established connection with information presentation apparatuses, in Step  807 , controller  109   b  displays a list of information presentation apparatuses on display unit  107 , as in the example of a screen display in  FIG. 9 , and prompts a user to select an information presentation apparatus to be connected. In Step  808 , when the user selects at least one information presentation apparatus using input unit  108  (using a touch panel in the case of a smart phone), controller  109   b  makes a setting such that the smart phone outputs sound and video to the selected information presentation apparatus. Subsequently, the screen display in  FIG. 9  is not shown on information terminal  103   b  (in the case of resident application, the application runs in the background), and another function (such as reproduction of content) can be executed. 
     On the other hand, when information presentation apparatus information includes information presentation apparatus information corresponding to the currently connected information presentation apparatus, controller  109   b  determines in Step  809  whether or not the user has performed reselecting operation of an information presentation apparatus (whether or not the user has reselected an information presentation apparatus). When the user has not performed the reselecting operation, controller  109   b  returns to Step  802 , whereas, when the user has performed the reselecting operation, controller  109   b  executes Step  807  and Step  808 . 
     On the other hand, when the location information has not bee successfully received in Step  803 , controller  109   b  determines in Step  810  whether or not the timer counter indicates that a predetermined time period (for example, five minutes) has passed. When five minutes have passed since the timer counter was reset, controller  109   b  disconnects network connection from (cancels pairing with) the information presentation apparatus in Step  811 , and resets the timer counter in Step  812 . When five minutes have not passed since the timer counter was reset, controller  109   b  returns to Step  802 . 
     In Embodiment 3, pairing information is encrypted and stored in an application so that the pairing information can be referred to only when the location information is received from illumination device  101 . Such a configuration is also applicable to Embodiment 1. Security can be similarly secured in Embodiment 2 as well by encrypting access right to a server (an IP address, a login ID, a password and the like) for storage in an application. 
     As described above, in Embodiment 3, information recording medium  106   b  holds pairing information associating the location information of illumination device  101  with each of information presentation apparatuses  102   a  to  102   c . When information terminal  103   b  is illuminated by visible light, information terminal  103   b  selects at least one piece of connection information from among a plurality of pieces of connection information associated with the location information included in the visible light, and establishes connection with at least one information presentation apparatus based on the selected at least one piece of connection information. In other words, even when a plurality of information presentation apparatuses  102   a  to  102   c  are present near an area illuminated by the visible light emitted from illumination device  101 , the user is only necessary to select an information presentation apparatus to allow pairing between information terminal  103   b  and the selected information presentation apparatus. Hence, pairing is performed between information terminal  103   b  and a desired information presentation apparatus while requiring information presentation apparatuses to include a wireless communication function instead of a dedicated function, and requiring a user to simply select a desired information presentation apparatus from among a plurality of information presentation apparatuses. As a result, for example, information terminal  103   b  can output content to a desired information presentation apparatus, or information terminal  103   b  can operate the information presentation apparatus. 
     Moreover, in Embodiment 3, pairing information is encrypted and held in the form of an application on information terminal  103   b  (smart phone in Embodiment 3), and information terminal  103   b  receives permitted location information from illumination device  101 . This prevents information from being output to an information presentation apparatus improperly (for example, from outside the room). 
     (Embodiment 4) 
       FIG. 10  illustrates a configuration of visible light communication system  4  according to Embodiment 4. 
     Visible light communication system  4  is a system in which pairing between information terminal  103   c  and information presentation apparatus  102  is automatically performed using visible light in wireless communication. 
     Visible light communication system  4  includes a plurality of illumination devices  101   a  to  101   b , information presentation apparatus  102 , and information terminal  103   c.    
     In Embodiment 4, illumination devices  101   a  to  101   b  are approximately the same as illumination device  101  according to Embodiment 1 except that illumination devices  101   a  to  101   b  emit visible light including different pieces of identification information m 1  to mM (location information m 1  to mM in Embodiment 4). Information presentation apparatus  102  is approximately the same as that in Embodiment 1, and thus, its description is not given. The same reference numerals are assigned to the structural elements which are included in information terminal  103   c  and which are approximately the same as those in Embodiment 1, and the descriptions thereof are not given. 
     Information terminal  103   c  is capable of performing communication using visible light. Information terminal  103   c  includes visible light communication receiver  104 , communication unit  105 , information recording medium  106   c , display unit  107 , input unit  108 , and controller  109   c . Information recording medium  106   c  is a recording medium which holds pairing information associating a plurality of pieces of identification information identifying illumination devices  101   a  to  101   b  with connection information required for connection via wireless communication with information presentation apparatus  102 . In Embodiment 4, information recording medium  106   c  holds pairing information associating the plurality of pieces of location information of illumination devices  101   a  to  101   b  with connection information required for connection via wireless communication with one information presentation apparatus  102 . Controller  109   c  is a circuit for controlling operations of information terminal  103   c , and, for example, includes a nonvolatile memory storing programs, a volatile working memory, a timer counter, and a processor which executes programs. 
     Illumination devices  101   a  to  101   b  associated with one information presentation apparatus  102  by pairing information are illumination devices belonging to one group, and are, for example, illumination devices installed in the same room. 
       FIG. 11  illustrates a structure of pairing information held in information recording medium  106   c  of information terminal  103   c  according to Embodiment 4. As  FIG. 11  illustrates, in Embodiment 4, pairing information  201  (pairing information 1 to m in (a) of  FIG. 11 ) is generated for each piece of network connection information. Each piece of pairing information  201  includes a plurality of pieces of location information  202  and associated one piece of network connection information  203  (location information ml to mM and network connection information ml in (b) of  FIG. 11 ). 
     Information terminal  103   c  operates in a similar manner to the flowchart in  FIG. 3  according to Embodiment 1, but operates differently in Step  305 . Specifically, controller  109   c  of information terminal  103   c  searches pairing information  201  based on the received location information. As a result of the search, if the received location information matches any one of the plurality of pieces of location information  202  in pairing information  201 , controller  109   c  obtains associated network connection information  203 , and establishes connection with information presentation apparatus  102  based on obtained network connection information  203 . The other operations of Information terminal  103   c  are the same as those in the flowchart in  FIG. 3 . 
     As described above, in Embodiment 4, information recording medium  106   c  holds pairing information associating the plurality of pieces of location information of illumination devices  101   a  to  101   b  and connection information of information presentation apparatus  102 . When information terminal  103   c  is illuminated by visible light emitted from at least one of illumination devices  101   a  to  101   b , information terminal  103   c  refers to pairing information held in information recording medium  106   c  to identify connection information associated with the location information included in the visible light. Information terminal  103   c  establishes connection with information presentation apparatus  102  based on the identified connection information. In other words, when information terminal  103   c  enters the range illuminated by any one of illumination devices  101   a  to  101   b  and receives location information, information terminal  103   c  is automatically connected to predetermined information presentation apparatus  102  placed near an area where the visible light is emitted by the illumination device. Accordingly, pairing between information terminal  103   c  and information presentation apparatus  102  is performed while requiring information presentation apparatus  102  to include a wireless communication function instead of a dedicated function, and without requiring a dedicated operation for pairing in wireless communication. As a result, for example, information terminal  103   c  can output content to information presentation apparatus  102  placed near information terminal  103   c , or information terminal  103   c  can operate information presentation apparatus  102 . 
     Moreover, even when a plurality of illumination devices are present in the same room or area and each illumination device emits a different piece of location information (digits of location information may be partly or entirely different), pairing between information terminal  103   c  and information presentation apparatus  102  is automatically performed. In other words, information terminal  103   c  receives any one of a plurality of pieces of location information, and can connect to associated information presentation apparatus  102 . 
     Visible light communication systems according to the present disclosure have been described based on Embodiments 1 to 4, but the present disclosure is not limited to Embodiments 1 to 4. Those skilled in the art would readily appreciate that, without departing from the teachings of the present disclosure, various modifications may be made in the above-described Embodiments 1 to 4 and other embodiments may be obtained by arbitrarily combining the structural elements in the above described Embodiments 1 to 4. 
     For example, pairing information held in an information recording medium may be a mixture of three types of pairing information described in Embodiments 1, 3, and 4. Specifically, the first type of pairing information may be pairing information which associates location information with connection information in a one-to-one correspondence as described in Embodiment 1. The second type of pairing information may be pairing information which associates location information with a plurality of pieces of connection information in a one-to-many correspondence as described in Embodiment 3. The third type of pairing information is pairing information which associates a plurality of pieces of location information with connection information in a many-to-one correspondence as described in Embodiment 4. 
     Moreover, in Embodiments 1 to 4, the information presentation apparatus is an apparatus which presents information (or provides light) on site, such as a speaker, a projector, a TV, a digital signage, an electronic whiteboard, a printer, and an illumination device, but the present disclosure is not limited to such apparatuses. The information presentation apparatus may be a reproduction apparatus which transmits content such as video and sound via wireless communication. With this, when pairing is performed between an information terminal and an information presentation apparatus, the content transmitted from the information presentation apparatus via wireless communication is reproduced by the information terminal. 
     While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings.