Patent Publication Number: US-2015062643-A1

Title: Wireless communication apparatus, wireless communication method, and storage medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a technique for communication between wireless communication apparatuses that can perform short-distance wireless communication. 
     2. Description of the Related Art 
     Some image forming apparatuses such as printers and multifunction peripherals have a user authentication function for managing permission for users. Radio Frequency Identification (RFID) tags can be used for such user authentication function. When an RFID tag is used, an image forming apparatus includes a tag reader/writer for reading/writing the RFID tag. More specifically, when an RFID tag is brought near the image forming apparatus, the tag reader/writer in the image forming apparatus reads authentication data from the RFID tag and performs user authentication based on the read authentication data. 
     Recent mobile terminals such as smartphones and tablet personal computers (PCs) and image forming apparatuses employs Near Field Communication (NFC), which is a short-distance wireless communication technique that is compatible with RFID. In NFC, three functions are defined. The first function is a reader/writer function, which realizes a function equivalent to that of a tag reader/writer for RFID tags. The second function is a card-emulation function, which realizes a function equivalent to that of an RFID tag. The third function is a peer-to-peer function, which realizes transmission and reception of various data by using NFC. 
     NFC-enabled mobile terminals can read and write data from/in an RFID card or an NFC card, by using the reader/writer function. Thus, a function equivalent to a user authentication function using an RFID tag can be realized between an NFC-enabled mobile terminal and an NFC-enabled image forming apparatus. In such a case, the image forming apparatus realizes a function equivalent to that of an RFID tag by using the NFC card-emulation function, and the mobile terminal writes authentication data in the image forming apparatus. 
     When a mobile terminal transmits image data to an image forming apparatus for printing, the mobile terminal uses longer-distance and larger-capacity wireless communication than NFC, such as wireless Local Area Network (LAN) and Bluetooth (registered trademark). Since no cables are required for communication, complicated work for connection is not necessary. However, unlike communication in which a mobile terminal and an image forming apparatus are clearly connected by cables, the image forming apparatus needs to determine a mobile terminal to be a peer (connection partner) from among a large number of unspecified mobile terminals. 
     Japanese Patent Application Laid-Open No. 2001-156723 discusses a wireless communication apparatus determining a peer by using wireless communication with directivity (directional wireless communication). After performing directional wireless communication to determine a peer, the wireless communication apparatus switches the connection to wireless communication without directivity such as to a wireless LAN. In Japanese Patent Application Laid-Open No. 2001-156723, Infrared Data Association (IrDA) is used as directional wireless communication. Japanese Patent Application Laid-Open No. 2007-267370 discusses an information processing apparatus, which first determines a mobile terminal to be a peer by using a non-contact IC card capable of short-distance wireless communication and next establishes wireless communication such as a wireless LAN with this mobile terminal. 
     With growing environmental awareness, there are image forming apparatuses with a power saving mode. For example, when not used for a certain period of time, these image forming apparatuses shift to a low power consumption state (for example, a sleep mode). In such a low power consumption state, power supply to various functions is shut off, except for some functions such as a network interface in the image forming apparatus. It takes several seconds to several tens of seconds for an image forming apparatus to restart from a low power consumption state. NFC is established when a user places a mobile terminal close to (approximately 10 [cm]) the image forming apparatus, for example. Normally, the duration of time for which a mobile terminal is placed close to an image forming apparatus is shorter than the duration of time required for the image forming apparatus to shift back to a normal power supply state from the low power consumption state. Therefore, even if the mobile terminal attempts to perform NFC with the image forming apparatus in the low power consumption state, the mobile terminal is moved away from the NFC area before the image forming apparatus restarts. As a result, since NFC cannot be performed, processing such as user authentication using NFC and establishment of a wireless LAN cannot be performed. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a wireless communication apparatus and a wireless communication method capable of performing short-distance wireless communication with other apparatuses even when the wireless communication apparatus is in a low power consumption state. 
     According to an aspect of the present invention, there is provided an image processing apparatus capable of operating in a first power mode and a second power mode requiring less power consumption than that in the first power mode. The image processing apparatus includes a first communication unit configured to perform short-distance wireless communication, a shift unit configured to cause, when the image processing apparatus establishes communication with another apparatus via the first communication unit while operating in the second power mode, the image processing apparatus to shift from the second power mode to the first power mode, and an instruction unit configured to instruct, when the shift unit causes the image processing apparatus to shift to the first power mode, a user of the other apparatus to perform an action for establishing communication via the first communication unit again. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an overall configuration of a system. 
         FIG. 2  illustrates a schematic configuration of an image forming apparatus. 
         FIG. 3  illustrates a configuration of a mobile terminal. 
         FIG. 4  is a flowchart illustrating a procedure of user authentication processing performed by the image forming apparatus. 
         FIG. 5  illustrates a guiding image. 
         FIG. 6  is a flowchart illustrating a procedure of processing performed when the mobile terminal establishes a wireless LAN communication. 
         FIG. 7  is a connection sequence diagram illustrating a procedure for establishing wireless LAN communication. 
         FIG. 8  is a flowchart illustrating a procedure of user authentication processing performed by an image forming apparatus. 
         FIG. 9  is a flowchart illustrating a procedure of processing performed when a mobile terminal establishes wireless LAN communication. 
         FIG. 10  illustrates a guiding image. 
         FIG. 11  is a connection sequence diagram illustrating a procedure for establishing wireless LAN communication. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. The constituent elements described in the following exemplary embodiments are merely used as examples, and the scope of the present invention is not limited to such constituent elements. 
       FIG. 1  illustrates an overall configuration of a system according to a first exemplary embodiment. The system includes an image forming apparatus  100  such as a printer and a multifunction peripheral, a computer terminal  200 , a mobile terminal  300 , and a wireless LAN master unit  400 . In this system, these components are connected to each other via a network  500  such as a LAN and communicate with each another. The network  500  is realized by Ethernet (registered trademark) or the like. Short-distance wireless communication (hereinafter, referred to as “NFC communication”)  600  can be performed between the image forming apparatus  100  and the mobile terminal  300 . Longer-distance and larger-capacity wireless communication (hereinafter, referred to as “wireless LAN communication”)  700  than the short-distance wireless communication can be performed between the mobile terminal  300  and the wireless LAN master unit  400 . However, the wireless LAN communication  700  is merely an example, and another communication method may be used as long as the method achieves longer-distance and larger-capacity wireless communication than the short-distance wireless communication. 
     The image forming apparatus  100  is realized by a copying machine, a multifunction peripheral, or the like having copy, print, and scan functions. In addition, the image forming apparatus  100  includes a function of authenticating users using the above functions. The image forming apparatus  100  performs user authentication of an authentication card (not illustrated) or the mobile terminal  300  in which ID data (identification information) for identifying a user is stored. The ID data is an example of authentication data. The image forming apparatus  100  receives the ID data stored in the authentication card or the mobile terminal  300  via the NFC communication  600  and performs the user authentication by referring to an internal authentication database (not illustrated). Alternatively, the user authentication may be performed by separately arranging a server including an authentication database on the network  500 . In this case, the image forming apparatus  100  transmits the ID data to the server and receives an authentication result from the server. 
     The computer terminal  200  transmits a print job to the image forming apparatus  100 . In addition, the computer terminal  200  can display electronic data obtained by a scanner function or the like in the image forming apparatus  100 . 
     The mobile terminal  300  is a portable wireless communication apparatus such as a smartphone and a tablet PC. The mobile terminal  300  can perform the NFC communication  600  and the wireless LAN communication  700 . The mobile terminal  300  exchanges various data such as IP addresses and user ID data with the image forming apparatus  100  via the NFC communication  600 . In addition, the mobile terminal  300  performs communication with various apparatuses connected to the network  500  by using the wireless LAN communication  700  via the wireless LAN master unit  400 . In other words, the wireless LAN master unit  400  relays communication between an apparatus such as the mobile terminal  300  that makes access by using the wireless LAN communication  700  and an apparatus connected to the network  500 . 
     &lt;Image Forming Apparatus&gt; 
       FIG. 2  illustrates a schematic configuration of the image forming apparatus  100 . The image forming apparatus  100  includes a controller  101 , a scanner unit  102 , a printer unit  103 , an operation unit  108 , an NFC unit  110 , a power supply unit  116 , and a power supply control unit  117 . The scanner unit  102  is an image input device that scans documents and acquires images. The printer unit  103  is an image output device that performs image forming processing on paper or the like. The controller  101  controls operations of the scanner unit  102  and the printer unit  103 . The scanner unit  102  and the printer unit  103  can have various configurations based on conventional techniques. 
     The controller  101  includes a central processing unit (CPU)  104  that controls an overall operation of the image forming apparatus  100 . The CPU  104  executes a computer program read from a read only memory (ROM)  106  while using a random access memory (RAM)  105  as a work area. 
     In addition, the controller  101  includes a hard disk drive (HDD)  107  and a network interface (I/F)  109 . The HDD  107  is a large-capacity storage device storing software programs relating to control of the image forming apparatus  100 , various settings, image data, and documents, for example. In addition, the above authentication database is included in the HDD  107 . The network I/F  109  is an interface for performing communication with other apparatuses on the network  500  (with the computer terminal  200  in  FIG. 2 ) via the network  500 . 
     The operation unit  108  is an input/output interface including a touch panel with operation buttons and a display. A user can input data, and check information on the display on the operation unit  108 . 
     The NFC unit  110  includes an NFC communication unit  111  including a buffer  112 , an antenna  113  transmitting and receiving radio waves used for the NFC communication  600 , a micro processor (MP)  114 , and a work memory  115 . The MP  114  communicates with the CPU  104  in the controller  101  and controls the NFC unit  110  while using the work memory  115  as a work area. The NFC unit  110  realizes the reader/writer function, the card-emulation function, and the peer-to-peer function. Since the NFC unit  110  enables the NFC communication  600 , the image forming apparatus  100  is also a wireless communication apparatus. 
     The NFC communication unit  111  performs the NFC communication  600  with the other apparatuses. The buffer  112  is a first-in first-out (FIFO) memory and stores data transmitted/received via the NFC communication  600 . The buffer  112  has a minimum storage capacity sufficient to perform the NFC communication  600 . Thus, data stored in the buffer  112  can easily be overwritten. 
     The power supply unit  116  supplies direct-current (DC) power generated from a commercial power supply to each of the units such as the controller  101 , the scanner unit  102 , the printer unit  103 , and the NFC unit  110  in the image forming apparatus  100 . The power supply unit  116  includes a switch that shuts off the DC power supply to various units, in response to a control signal from the power supply control unit  117 . For example, when the image forming apparatus  100  shifts to the low power consumption state, the power supply control unit  117  transmits a control signal to the power supply unit  116  and causes the power supply unit  116  to supply the DC power only to a minimum number of units. 
     According to the present exemplary embodiment, in the low power consumption state, the DC power is supplied only to the network I/F  109 , the power supply control unit  117 , and the NFC unit  110 . Since the controller  101  consumes a large amount of power, the DC power is not supplied to the controller  101 . The other components may be supplied with the DC power. However, the DC power is not supplied to components that consume a large amount of power. Alternatively, in the low power consumption state, only the DC power supplied to the operation unit  108  and the scanner unit  102  may be shut off. In addition, in the low power consumption state, a plurality of configurations for supplying the DC power may be provided, and the DC power supplied to the units may be sequentially shut off at regular intervals. In other words, the low power consumption state is a state in which the image forming apparatus  100  requires less power consumption than that required in a normal operation. 
     &lt;Mobile Terminal&gt; 
       FIG. 3  illustrates a configuration of the mobile terminal  300 . The mobile terminal  300  includes a CPU  301 , a RAM  302 , a flash ROM  303 , an operation unit  304 , a camera  305 , a wireless LAN I/F  306 , an NFC control unit  307 , and an antenna  308 . These components are connected with each other so that these components can exchange data with each other via a system bus  309 . 
     The CPU  301  controls an overall operation of the mobile terminal  300 . The CPU  301  executes a computer program read from the flash ROM  303  while using the RAM  302  as a work area. Other than such a computer program, various data is stored in the flash ROM  303 . 
     The operation unit  304  is an input/output interface including a touch panel with a display. A user can input data and check information on the display on the operation unit  304 . The camera  305  is an imaging apparatus that captures still images and moving images. The wireless LAN I/F  306  is an interface for performing the wireless LAN communication  700  with the other apparatuses (for example, with the wireless LAN master unit  400 ). The NFC control unit  307  is an interface for performing the NFC communication  600  with the other apparatuses capable of the NFC communication  600  (e.g., with the image forming apparatus  100 ). The antenna  308  transmits and receives radio waves for the NFC communication  600 . The NFC control unit  307  realizes the reader/writer function and the peer-to-peer function. Unlike the image forming apparatus  100 , the NFC control unit  307  in the mobile terminal  300  does not have a card-emulation function. 
     &lt;Processing by Image Forming Apparatus&gt; 
       FIG. 4  is a flowchart illustrating a procedure of user authentication processing performed by the image forming apparatus  100  in the low power consumption state. The image forming apparatus  100  can perform user authentication of an authentication card and the mobile terminal  300 . In this flowchart, when the image forming apparatus  100  performs user authentication of the mobile terminal  300 , settings for establishing the wireless LAN communication  700  between the image forming apparatus  100  and the mobile terminal  300  are made. 
     When the image forming apparatus  100  is not used for a predetermined period of time or when the image forming apparatus  100  receives an instruction from a user via the operation unit  108 , the CPU  104  in the image forming apparatus  100  causes the image forming apparatus  100  to shift to the low power consumption state. First, in step S 401 , the CPU  104  writes a sleep-flag-on signal in the buffer  112  in the NFC unit  110 . The sleep-flag-on signal is a flag signal indicating that the image forming apparatus  100  is in the low power consumption state. The CPU  104  writes the sleep-flag-on signal in the buffer  112  when the image forming apparatus  100  is in the low power consumption state. On the other hand, the CPU  104  writes a sleep-flag-off signal when the image forming apparatus  100  shifts back to the normal power supply state from the low power consumption state. In step S 402 , after writing the sleep-flag-on signal in the buffer  112 , the CPU  104  causes the power supply control unit  117  to control the power supply unit  116  to shift the image forming apparatus  100  to the low power consumption state. Controlled by the power supply control unit  117 , the power supply unit  116  appropriately shuts off the power supply to relevant components. Since the power supply to the CPU  104  is shut off, processing by the CPU  104  is stopped while the image forming apparatus  100  is in the low power consumption state. 
     When the image forming apparatus  100  is in the low power consumption state, the NFC communication unit  111  therein waits while switching between the reader/writer function and the card-emulation function. The NFC communication unit  111  waits until the mobile terminal  300  or an authentication card comes close to the image forming apparatus  100  and the NFC communication  600  is established. The NFC communication unit  111  can establish the NFC communication  600  with the mobile terminal  300  while realizing the card-emulation function. The NFC communication unit  111  can establish the NFC communication  600  with an authentication card while realizing the reader/writer function. 
     In step S 403 , the MP  114  determines whether the NFC communication  600  is established with the authentication card while the NFC communication unit  111  is realizing the reader/writer function. If the NFC communication  600  is established with the authentication card (YES in step S 403 ), the operation proceeds to step S 404 . In step S 404 , the MP  114  issues a restoration request signal for requesting a restoration from the low power consumption state to the normal power supply state to the control unit  117 . In step S 405 , the MP  114  reads ID data of the authentication card via the NFC communication  600  and writes the read ID data in the buffer  112 . 
     If the NFC communication  600  is not established with the authentication card (NO in step S 403 ), the operation proceeds to step S 406 . If In step S 406 , the MP  114  determines whether the NFC communication  600  is established with the mobile terminal  300  while the NFC communication unit  111  is realizing the card-emulation function. If the NFC communication  600  is established with the mobile terminal  300  (YES in step S 406 ), the operation proceeds to step S 407 . In step S 407 , the MP  114  issues a restoration request signal to the power supply control unit  117 . In this case, the mobile terminal  300  writes a “command” in the buffer  112 . This command is an instruction for displaying an instruction image for requesting the user of the mobile terminal  300  to perform the NFC communication  600  again via the NFC communication  600 . 
     In step S 408 , in response to the restoration request signal issued in step S 404  or S 407 , the power supply control unit  117  causes the power supply unit  116  to shift to the normal power supply state and to supply power to each component. When the power supply unit  116  is shifted to the normal power supply state, the MP  114  shifts the processing of the NFC unit  110  to the CPU  104 . In step S 409 , the CPU  104  reads the data from the buffer  112 . After reading the data from the buffer  112 , the CPU  104  writes a sleep-flag-off signal in the buffer  112 . 
     In step S 410 , the CPU  104  determines whether the read data is the command written by the mobile terminal  300 . If the CPU  104  determines that the read data is the command written by the mobile terminal  300  (YES in step S 410 ), the operation proceeds to step S 101 . In step S 101 , the CPU  104  in the image forming apparatus  100  displays a guiding image illustrated in  FIG. 5  on the display of the operation unit  108  in response to the command. This guiding image requests the user to place the mobile terminal  300  close to the image forming apparatus  100 . In step S 412 , the CPU  104  determines whether the user places the mobile terminal  300  close to the image forming apparatus  100  again in accordance with the guiding image and the NFC communication  600  is re-established. If the CPU  104  determines that the user places the mobile terminal  300  close to the image forming apparatus  100  again (YES in step S 412 ), the mobile terminal  300  writes ID data thereof in the buffer  112  via the NFC communication  600 . Then, the operation proceeds to step S 413 . In step S 413 , the CPU  104  reads the ID data of the mobile terminal  300  written in the buffer  112 , refers to the authentication database established in the HDD  107 , and performs user authentication. In step S 414 , after the user authentication, in response to a request from the mobile terminal  300 , the CPU  104  writes wireless information in the buffer  112 . Then, the CPU  104  ends the processing. By writing the wireless information in the buffer  112 , the image forming apparatus  100  can provide the wireless information to the mobile terminal  300 . The mobile terminal  300  reads the wireless information via the NFC communication  600 . The wireless information includes information such as an IP address of the image forming apparatus  100  and a service set identifier (SSID) for connection between the image forming apparatus  100  and the mobile terminal  300  via the wireless LAN master unit  400 . 
     If the data read in step S 410  is not the command (NO in step S 410 ), the operation proceeds to step S 416 . In step S 416 , the CPU  104  determines whether the read data is the ID data written in the buffer  112  in step S 405 . If the CPU  104  determines that the read data is the ID data (YES in step S 416 ), the operation proceeds to step S 417 . In step S 417 , the CPU  104  performs user authentication as in step S 413 . Next, the CPU  104  ends the processing. If the read data is not the ID data (NO in step S 416 ), the CPU  104  ends the processing without performing user authentication. 
     &lt;Processing by Mobile Terminal&gt; 
       FIG. 6  is a flowchart illustrating a procedure of processing performed when the mobile terminal  300  establishes the wireless LAN communication  700 . This processing is realized by causing the mobile terminal  300  to execute application software for setting wireless LAN communication. The application software is not limited to a single configuration. The processing can be realized by using a plurality of application software programs or by replacing part of an application software program with an operation by a user. The CPU  301  in the mobile terminal  300  executes this application software. 
     In step S 601 , the CPU  301  determines whether the user places the mobile terminal  300  close to the image forming apparatus  100  and the NFC communication  600  is established with the image forming apparatus  100  by the NFC control unit  307 . If the CPU  301  determines that the user places the mobile terminal  300  close to the image forming apparatus  100  (YES in step S 601 ), the operation proceeds to step S 602 . In step S 602 , the CPU  301  in the mobile terminal  300  reads data stored in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . The read data is either a sleep-flag-on signal or a sleep-flag-off signal. Through the sleep-flag-on signal or the sleep-flag-off signal, the mobile terminal  300  is notified by the image forming apparatus  100  of the power supply state thereof. 
     In step S 603 , the CPU  301  determines whether the read data is a sleep-flag-on signal. If the read data is a sleep-flag-on signal (YES in step S 603 ), the CPU  301  determines that the image forming apparatus  100  is in the low power consumption state, and the operation proceeds to step S 604 . In step S 604 , the CPU  301  writes a command in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . This command is the command written in step S 407  in  FIG. 4 . In accordance with the command, the image forming apparatus  100  displays the guiding image illustrated in  FIG. 5 . According to this guiding image, the user of the mobile terminal  300  places the mobile terminal  300  close to the image forming apparatus  100  again. With this operation, in step S 605 , the CPU  301  determines whether the NFC communication  600  is established again between the mobile terminal  300  and the image forming apparatus  100 . If the NFC communication  600  is established (YES in step S 605 ), the operation proceeds to step S 606 . 
     In step S 606 , the CPU  301  writes the ID data in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In addition, in step S 606 , the CPU  301  writes a wireless information request signal for requesting wireless information in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . As a result, in step S 413  in  FIG. 4 , the image forming apparatus  100  can perform user authentication. After the user authentication, in step S 414  in  FIG. 4 , in response to the wireless information request signal, the image forming apparatus  100  writes wireless information in the buffer  112 . The buffer  112  in the image forming apparatus  100  has a small storage capacity as described above. Therefore, the CPU  301  in the mobile terminal  300  may not be able to simultaneously write the ID data and the wireless information request signal in the buffer  112 . In such a case, the CPU  301  in the mobile terminal  300  writes the wireless information request signal in the buffer  112  after a period of time sufficient for the CPU  104  in the image forming apparatus  100  to read the ID data from the buffer  112 . 
     In step S 607 , the CPU  301  in the mobile terminal  300  reads the wireless information written in the buffer  112  via the NFC communication  600 . In step S 608 , the CPU  301  makes settings for the wireless LAN communication  700  on the basis of the read wireless information and establishes the wireless LAN communication  700  with the image forming apparatus  100 . Then, the CPU  301  ends the processing. 
     On the other hand, in step S 603 , if the data read in step S 602  is a sleep-flag-off signal (NO in step S 603 ), the CPU  301  in the mobile terminal  300  determines that the image forming apparatus  100  is in the normal power supply state. In this case, since the NFC communication  600  does not need to be established again, the CPU  301  in the mobile terminal  300  performs processing in step S 606  and the subsequent steps. 
     &lt;Operational Embodiment&gt; 
       FIG. 7  is a connection sequence diagram illustrating a procedure for establishing the wireless LAN communication  700  between the image forming apparatus  100  and the mobile terminal  300 . Since  FIG. 7  includes the same steps as those in the flowcharts in  FIGS. 4 and 6 , these steps are denoted by the same reference numerals. 
     When the image forming apparatus  100  shifts to the low power consumption state, the controller  101  in the image forming apparatus  100  transmits a sleep-flag-on signal to the NFC unit  110 . In step S 401 , the CPU  104  writes the sleep-flag-on signal in the buffer  112  in the NFC unit  110 . In step S 402 , the controller  101  transmits a shift request signal for requesting a shift to the low power consumption state to the power supply control unit  117 . Accordingly, the image forming apparatus  100  shifts to the low power consumption state. In step S 701 , the power supply to the controller  101  is shut off. 
     In step S 601 , the mobile terminal  300  comes close to the image forming apparatus  100  in the low power consumption state, and the NFC control unit  307  in the mobile terminal  300  transmits an NFC communication request signal for requesting establishment of the NFC communication  600  to the NFC unit  110  in the image forming apparatus  100 . In step S 406 , in response to the NFC communication request signal, the NFC unit  110  in the image forming apparatus  100  transmits an NFC communication response signal to the NFC control unit  307  in the mobile terminal  300 . Thus, in step S 702 , the NFC communication  600  is established between the mobile terminal  300  and the image forming apparatus  100 . 
     In step S 407 , after the NFC communication  600  is established, the NFC unit  110  in the image forming apparatus  100  issues a restoration request signal to the power supply control unit  117 . In response to the restoration request signal, the power supply control unit  117  causes the power supply unit  116  to shift back to the normal power supply state and to supply power to each component. 
     In step S 602 , the mobile terminal  300  acquires a sleep-flag-on signal from the buffer  112  in the image forming apparatus  100  via the NFC communication  600  and determines that the image forming apparatus  100  is in the low power consumption state. In step S 604 , after determining that the image forming apparatus  100  is in the low power consumption state, the mobile terminal  300  writes a command for displaying a guiding image in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600 . Normally, the mobile terminal  300  is moved away from the area in which the NFC communication  600  can be performed in approximately one second after the NFC communication  600  is established. Therefore, the NFC communication  600  between the mobile terminal  300  and the image forming apparatus  100  is interrupted in approximately one second after the NFC communication  600  is established. Thus, the NFC communication  600  is established temporarily. Therefore, the series of steps including writing the command is performed within one second after the NFC communication  600  is established. 
     In step S 408 , when the power supply is received from the power supply unit  116 , the controller  101  in the image forming apparatus  100  is restarted. After restarted, the controller  101  reads the data written in the buffer  112  in the NFC unit  110 . In step S 410 , the controller  101  reads the command written by the mobile terminal  300 . In step S 411 , in response to the read command, the controller  101  displays the guiding image illustrated in  FIG. 5  on the display of the operation unit  108 . 
     In steps S 605 , S 412 , and S 703 , in accordance with the guiding image, the user of the mobile terminal  300  places the mobile terminal  300  close to the image forming apparatus  100  again, and the NFC communication  600  is established again through the same processing as that in steps S 601  and S 406 . In step S 606 , after the NFC communication  600  is established, the mobile terminal  300  writes ID data in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600 . In step S 413 , the controller  101  in the image forming apparatus  100  reads the ID data written in the buffer  112 . As a result, the controller  101  in the image forming apparatus  100  acquires the ID data of the mobile terminal  300 . In step S 413 , the controller  101  in the image forming apparatus  100  performs the user authentication processing using the ID data acquired from the mobile terminal  300 . 
     In step S 606 , the mobile terminal  300  writes a wireless information request signal in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600  a predetermined period of time after writing the ID data. The “predetermined period of time” needs to be sufficiently long for the controller  101  in the image forming apparatus  100  to read the ID data in the buffer  112 . In step S 414 , after the user authentication, the controller  101  in the image forming apparatus  100  reads the wireless information request signal written in the buffer  112 . As a result, the controller  101  in the image forming apparatus  100  acquires the wireless information request signal. In step S 414 , in response to the wireless information request signal, the controller  101  writes wireless information in the buffer  112  in the NFC unit  110 . 
     In step S 607 , the mobile terminal  300  reads the wireless information from the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In step S 608 , the mobile terminal  300  establishes the wireless LAN communication  700  by using the wireless information read in the buffer  112  in the image forming apparatus  100 . Then, the mobile terminal  300  ends the processing. 
     Through the above processing, the image forming apparatus  100  shifts from the low power consumption state and completes the user authentication of the mobile terminal  300 . As a result, the wireless LAN communication  700  is established between the image forming apparatus  100  and the mobile terminal  300 . 
     Next, a second exemplary embodiment of the present invention will be described. In the second exemplary embodiment, the image forming apparatus  100  performs user authentication and establishes the wireless LAN communication  700  without using a sleep-flag-on signal indicating that the image forming apparatus  100  is in the low power consumption state. Processing according to the second exemplary embodiment is performed in the same system as that illustrated in  FIG. 1  according to the first exemplary embodiment. In addition, the image forming apparatus  100  and the mobile terminal  300  according to the second exemplary embodiment have similar configurations to those according to the first exemplary embodiment. Thus, redundant descriptions of the configurations of the system, the image forming apparatus  100 , and the mobile terminal  300  will be avoided. 
     &lt;Processing by Image Forming Apparatus&gt; 
       FIG. 8  is a flowchart illustrating a procedure of user authentication processing performed by the image forming apparatus  100  in the low power consumption state. 
     In step S 801 , when the image forming apparatus  100  is not used for a predetermined period of time or when the image forming apparatus  100  receives an instruction from a user via the operation unit  108 , the CPU  104  in the image forming apparatus  100  causes the image forming apparatus  100  to shift to the low power consumption state. In steps S 802  to S 807 , after the image forming apparatus  100  shifts to the low power consumption state, the CPU  104  performs the similar processing to that performed in steps S 403  to S 408  illustrated in  FIG. 4  according to the first exemplary embodiment. As a result, the MP  114  issues a restoration request signal to the power supply control unit  117  and the power supply unit  116  shifts back to the normal power supply state. If an authentication card comes close to the image forming apparatus  100 , ID data of this authentication card is written in the buffer  112  in the NFC unit  110 . If the mobile terminal  300  comes close to the image forming apparatus  100 , ID data of this mobile terminal  300  and a wireless information request signal are written in the buffer  112  in the NFC unit  110 . However, the “command” used in the first exemplary embodiment is not written. 
     In step S 808 , after the image forming apparatus  100  shifts back to the normal power supply state, the CPU  104  reads the data from the buffer  112  in the NFC communication unit  111 . In the buffer  112 , the ID data of the authentication card or the ID data of the mobile terminal  300  is written. Therefore, the CPU  104  reads either one of the ID data. The CPU  104  also reads the wireless information request signal if such signal is written. In step S 809 , the CPU  104  performs user authentication suing the read ID data. The user authentication is performed in the similar way to that in step S 413  illustrated in  FIG. 4 . 
     In step S 810 , after the user authentication is completed, the CPU  104  determines whether the mobile terminal  300  comes close to the image forming apparatus  100 , and the NFC communication  600  is established again. If the CPU  104  determines that the mobile terminal  300  comes close to the image forming apparatus  100  (YES in step S 810 ), the operation proceeds to step S 811 . In step S 811 , the CPU  104  in the image forming apparatus  100  acquires the ID data from the mobile terminal  300  again via the NFC communication  600  and determines whether the acquired ID data is the same ID data as the ID data authenticated in step S 809 . If the CPU  104  in the image forming apparatus  100  determines that the acquired ID data is the same ID data (YES in step S 811 ), the operation proceeds to step S 812 . In step S 812 , in response to the wireless information request signal read in step S 808 , the CPU  104  writes wireless information in the buffer  112 . Then, the CPU  104  ends the processing. The CPU  104  in the image forming apparatus  100  provides the wireless information to the mobile terminal  300  by writing the wireless information in the buffer  112 . In step S 810 , if the mobile terminal  300  does not come close to the image forming apparatus  100  or if user authentication is performed on ID data of an authentication card (NO in step S 810 ), the CPU  104  ends the processing without writing the wireless information in the buffer  112 . If the ID data acquired in step S 811  is not the same as the ID data authenticated in step S 809  (NO in step S 811 ), the CPU  104  ends the processing. 
     &lt;Processing by Mobile Terminal&gt; 
       FIG. 9  is a flowchart illustrating a procedure of processing performed when the mobile terminal  300  establishes the wireless LAN communication  700 . This processing is realized by causing the mobile terminal  300  to execute application software for setting wireless LAN communication. The application software is not limited to a single configuration. The processing can be realized by using a plurality of application software programs or by replacing part of an application software program with an operation by a user. The CPU  301  in the mobile terminal  300  executes this application software. 
     In step S 901 , the CPU  301  determines whether a user places the mobile terminal  300  close to the image forming apparatus  100  and the NFC control unit  307  establishes the NFC communication  600  with the image forming apparatus  100 . If the CPU  301  determines that a user places the mobile terminal  300  close to the image forming apparatus  100  (YES in step S 901 ), the operation proceeds to step S 902 . In step S 902 , the CPU  301  in the mobile terminal  300  writes ID data in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In addition, in step S 902 , the CPU  301  writes a wireless information request signal for requesting wireless information in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . The buffer  112  in the image forming apparatus  100  has a storage capacity capable of storing the ID data and the wireless information request signal at once. 
     In step S 903 , after writing the ID data and the wireless information request signal, the CPU  301  in the mobile terminal  300  attempts to read the wireless information from the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . If the image forming apparatus  100  is in the normal power supply state, the CPU  301  in the mobile terminal  300  can read the wireless information. However, if the image forming apparatus  100  is in the low power consumption state, the CPU  301  in the mobile terminal  300  cannot acquire the wireless information. If the CPU  301  cannot acquire the wireless information in its first attempt, the CPU  301  may make a plurality of attempts to read the wireless information. 
     In step S 904 , the CPU  301  determines whether the wireless information is acquired. If the wireless information cannot be acquired (NO in step S 904 ), the operation proceeds to step S 905 . In step S 905 , the CPU  301  in the mobile terminal  300  determines that the image forming apparatus  100  is in the low power consumption state and displays a guiding image illustrated in  FIG. 10  on the display of the operation unit  304 . This guiding image is to request the user to perform the NFC communication  600  again. 
     In step S 906 , the CPU  301  determines whether the user places the mobile terminal  300  close to the image forming apparatus  100  according to the guiding image and the NFC communication  600  is established again. If the CPU  301  determines whether the user places the mobile terminal  300  close to the image forming apparatus  100  (YES in step S 906 ), the operation proceeds to step S 907 . In step S 907 , the CPU  301  in the mobile terminal  300  writes the ID data in the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In step S 811  in  FIG. 8 , the image forming apparatus  100  uses this ID data to confirm the user. After the user is confirmed, in response to the wireless information request signal, the image forming apparatus  100  writes wireless information in the buffer  112 . In step S 908 , after the ID data is written, the CPU  301  in the mobile terminal  300  reads the wireless information from the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In step S 909 , the CPU  301  makes settings for the wireless LAN communication  700  on the basis of the read wireless information to establish the wireless LAN communication  700  with the image forming apparatus  100 . Then, the CPU  301  ends the processing. 
     On the other hand, in step S 904 , if the wireless information is acquired (YES in step S 904 ), the operation proceeds to step S 909 . In step S 909 , the CPU  301  makes settings for the wireless LAN communication  700  on the basis of the acquired wireless information to establish the wireless LAN communication  700  with the image forming apparatus  100 . Next, the CPU  301  ends the processing. 
     &lt;Operational Embodiment&gt; 
       FIG. 11  is a connection sequence diagram illustrating a procedure for establishing the wireless LAN communication  700  between the image forming apparatus  100  and the mobile terminal  300 . Since  FIG. 11  includes the same steps as those in the flowcharts in  FIGS. 8 and 9 , these steps are denoted by the same reference characters. 
     In step S 801 , the controller  101  in the image forming apparatus  100  transmits a shift request signal for requesting a shift to the low power consumption state to the power supply control unit  117 . Accordingly, the image forming apparatus  100  shifts to the low power consumption state. In step S 1101 , the power supply to the controller  101  is shut off. 
     In step S 901 , the mobile terminal  300  comes close to the image forming apparatus  100 , and the NFC control unit  307  in the mobile terminal  300  transmits an NFC communication request signal to the NFC unit  110  in the image forming apparatus  100 . In step S 805 , in response to the NFC communication request signal, the NFC unit  110  in the image forming apparatus  100  transmits an NFC communication response signal to the NFC control unit  307  in the mobile terminal  300 . As a result, in step S 1102 , the NFC communication  600  is established between the mobile terminal  300  and the image forming apparatus  100 . 
     In step S 806 , after the NFC communication  600  is established, the NFC unit  110  in the image forming apparatus  100  issues a restoration request signal to the power supply control unit  117 . In response to the restoration request signal, the power supply control unit  117  causes the power supply unit  116  to shift back to the normal power supply state and to supply power to each component. 
     In step S 902 , the mobile terminal  300  writes ID data in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600 . In addition, in step S 902 , the mobile terminal  300  writes a wireless information request signal in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600 . In step S 905 , if the mobile terminal  300  cannot acquire any wireless information in response to the wireless information request signal, the mobile terminal  300  displays the guiding image illustrated in  FIG. 10  on the display of the operation unit  304 . Normally, the mobile terminal  300  is moved away from the area in which the NFC communication  600  can be performed in approximately one second after the NFC communication  600  is established, whether or not acquisition of wireless information is succeeded. Therefore, the NFC communication  600  between the mobile terminal  300  and the image forming apparatus  100  is interrupted in approximately one second after the NFC communication  600  is established. Thus, the NFC communication  600  is established temporarily. 
     In step S 807 , when the power supply is received from the power supply unit  116 , the controller  101  in the image forming apparatus  100  is restarted. After restarted, in step S 808 , the controller  101  reads the data written in the buffer  112  in the NFC unit  110 . In this case, the controller  101  reads the ID data and the wireless information request signal written by the mobile terminal  300 . In step S 809 , the controller  101  performs user authentication using the read ID data. 
     In steps S 906 , S 810 , and S 1103 , in accordance with the guiding image, the user of the mobile terminal  300  places the mobile terminal  300  close to the image forming apparatus  100  again, and the NFC communication  600  is established again through the similar processing to that in steps S 901  and S 805 . In step S 907 , after the NFC communication  600  is established, the mobile terminal  300  writes the ID data in the NFC unit  110  (the buffer  112 ) in the image forming apparatus  100  via the NFC communication  600 . 
     In step S 811 , the controller  101  in the image forming apparatus  100  reads the ID data from the buffer  112  in the NFC unit  110  again and determines whether the acquired ID data is the same as the authenticated user ID. In step S 811 , if the user ID is the same as the authenticated user ID, in response to the wireless information request signal read in step S 808 , the controller  101  in the image forming apparatus  100  writes wireless information in the buffer  112  in the NFC unit  110 . In step S 908 , the mobile terminal  300  reads the wireless information from the buffer  112  in the image forming apparatus  100  via the NFC communication  600 . In step S 909 , the mobile terminal  300  establishes the wireless LAN communication  700  by using the wireless information read from the buffer  112  in the image forming apparatus  100 . Then, the mobile terminal  300  ends the processing. 
     Through the above processing, the image forming apparatus  100  completes the user authentication of the mobile terminal  300 . As a result, the wireless LAN communication  700  is established between the image forming apparatus  100  and the mobile terminal  300 . 
     As described above, according to the first and second exemplary embodiments, even when the image forming apparatus  100  receives a request for the NFC communication  600  from the mobile terminal  300  while operating in the low power consumption state, the image forming apparatus  100  can immediately shift to the normal operation and perform user authentication on the mobile terminal  300 . In addition, the image forming apparatus  100  can perform predetermined processing (establishment of the wireless LAN communication  700 ) after the user authentication via the NFC communication  600  established again after the image forming apparatus  100  shifts back to the normal power supply state. 
     According to the first and second exemplary embodiments, if the image forming apparatus  100  receives a request for establishing the NFC communication  600  while operating in the low power consumption state, the image forming apparatus  100  displays the guiding image for requesting the user to place the mobile terminal  300  close to the image forming apparatus  100  again. However, in place of the guiding image, the image forming apparatus  100  and/or the mobile terminal  300  may use voice to request the user to place the mobile terminal  300  close to the image forming apparatus  100 . Alternatively, the mobile terminal  300  may be vibrated to request the user to place the mobile terminal  300  close to the image forming apparatus  100 . 
     According to the present invention, if short-distance wireless communication is performed in a low power consumption state, the user of a peer apparatus in the short-distance wireless communication is requested to perform the short-distance wireless communication again. If the user performs the short-distance wireless communication again in response to the request, processing via the short-distance wireless communication such as user authentication can be performed. Thus, even if an apparatus is in a low power consumption state when the first short-distance wireless communication is performed, subsequent processing can be performed. 
     Other Embodiments 
     Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions recorded on a storage medium (e.g., non-transitory computer-readable storage medium) to perform the functions of one or more of the above-described embodiment(s) of the present invention, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more of a central processing unit (CPU), micro processing unit (MPU), or other circuitry, and may include a network of separate computers or separate computer processors. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2013-182012 filed Sep. 3, 2013, which is hereby incorporated by reference herein in its entirety.