Patent Publication Number: US-11039365-B2

Title: Communication apparatus, method for controlling communication apparatus, and storage medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a communication apparatus which connects to a base station. 
     Description of the Related Art 
     There has been formulated the Institute of Electrical and Electronics Engineers (IEEE) 802.11ai standard (hereinafter, 11ai) for speeding up connection between a wireless local area network (LAN) base station (access point (AP)) and a terminal apparatus (station (STA)). Fast Initial Link Setup (FILS) for shortening connection processing between an STA and an AP is standardized in 11ai. Japanese Patent Application Laid-Open No. 2011-217078 discusses a configuration for performing handover processing in which an STA switches its connection destination AP by using a FILS method. 
     If the FILS method can be used and an AP more appropriate than the currently-connected one is detected like an AP having a higher reception signal intensity, the STA can automatically perform a handover. In an actual environment, APs to which a handover can be made may include both a FILS-capable AP and a not FILS-capable one. 
     If, in such an environment, the STA automatically performs a handover to the not FILS-capable AP, connection processing is performed by a conventional method with several seconds of communication-disabled time. In such a case, for example, a communication application may terminate with an error due to timeout, or throughput may drop. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to enabling performing handover processing in consideration of whether a handover designation wireless network is capable of connection using the FILS method. 
     According to an aspect of the present invention, a communication apparatus includes one or more processors, and one or more memories including instructions that, when executed by the processor(s), cause the communication apparatus to detect, when in connection with a first wireless network, a second wireless network different from the first wireless network, determine, in a case where the second wireless network is detected, whether the second wireless network is capable of connection using a Fast Initial Link Setup (FILS) method, determine, based on a result of the determination, whether to perform handover processing for switching a connection destination from the first wireless network to the second wireless network, and perform the handover processing in a case where the handover processing is determined to be performed. 
     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  is a system configuration diagram. 
         FIG. 2  is a hardware configuration diagram of a communication apparatus. 
         FIG. 3  is a software function block diagram of the communication apparatus. 
         FIG. 4  is a flowchart implemented by the communication apparatus. 
         FIG. 5  is an operation sequence diagram during handover processing. 
         FIG. 6  is a flowchart implemented by a communication apparatus. 
         FIG. 7  is an operation sequence diagram during handover processing. 
         FIG. 8  is a flowchart implemented by a communication apparatus. 
         FIG. 9  is an operation sequence diagram during handover processing. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A communication apparatus according to a first exemplary embodiment will be described in detail below with reference to the drawings.  FIG. 1  illustrates a configuration of a communication system according to the present exemplary embodiment. The communication system according to the present exemplary embodiment includes a communication apparatus  101 , a base station  102 , and a base station  103 . 
     For example, the communication apparatus  101  may be an image input apparatus such as an imaging apparatus (camera or video camera) and a scanner. The communication apparatus  101  may be an image output apparatus such as a printer (single function printer (SFP) or multi-function printer (MFP)), a copying machine, and a projector. The communication apparatus  101  may be a storage device such as a hard disk drive and a memory device, or an information processing apparatus such as a personal computer and a smartphone. 
     The communication apparatus  101  and the base stations  102  and  103  perform wireless communication compliant with at least any one of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 series standards. 
     The base station  102  operates as an access point (AP) compliant with the IEEE 802.11 series standard and constructs a wireless network  112  (hereinafter, network  112 ). The base station  102  may operate as a group owner compliant with the Wi-Fi Direct standard (Wi-Fi Peer-to-Peer standard) and construct the network  112 . 
     The base station  103  operates as an AP and constructs a wireless network  113  (hereinafter, network  113 ). The base station  103  may operate as a group owner compliant with the Wi-Fi Direct standard and construct the network  113 . 
     The base stations  102  and  103  support IEEE 802.11ai (hereinafter, 11ai). The communication apparatus  101  can thus perform connection processing, using the Fast Initial Link Setup (FILS) method, with the wireless networks  112  and  113  constructed by the respective base stations  102  and  103 . FILS, defined in 11ai, is a method for speeding up processing equivalent to conventional Wi-Fi Protected Access (WPA)-Enterprise authentication processing and Dynamic Host Configuration Protocol (DHCP)-based Internet Protocol (IP) address assignment processing and enabling execution of connection processing. 
     The communication apparatus  101  can operate as a station (STA) compliant with the IEEE 802.11 series standard and perform connection processing using the FILS method with the wireless networks  112  and  113  constructed by the base stations  102  and  103 . The communication apparatus  101  can also perform connection processing using WPA-Enterprise. 
     The communication apparatus  101  can perform handover processing for switching the base station to be connected (for example, switching the connection destination from the base station  102  to the base station  103 ). As employed herein, the use of the FILS method for connection processing with the switched (new destination) wireless network during handover processing will be referred to as handover processing using FILS. Use of WPA-Enterprise for connection processing with the switched (new destination) wireless network will be referred to as handover processing using WPA-Enterprise. The handover processing using WPA-Enterprise includes IP address assignment processing by DHCP. 
     In the present exemplary embodiment, the same network identifier is set for the networks  112  and  113 . An example of the network identifier is a service set identifier (SSID). 
       FIG. 2  illustrates a hardware configuration of the communication apparatus  101 . 
     A storage unit  201  includes a memory such as a read-only memory (ROM) and a random access memory (RAM). The storage unit  201  stores programs for performing various operations to be described below, and various types of information such as a communication parameter for wireless communication. Aside from a ROM and a RAM, recording media such as a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a Compact Disc Read-Only Memory (CD-ROM), a Compact Disc-Recordable (CD-R), a magnetic tape, a nonvolatile memory card, and a digital versatile disc (DVD) may be used as the storage unit  201 . The storage unit  201  may include a plurality of memories. 
     A control unit  202  includes a processor such as a central processing unit (CPU) and a microprocessing unit (MPU). The control unit  202  controls the entire communication apparatus  101  by executing the programs stored in the storage unit  201 . The control unit  202  may control the entire communication apparatus  101  through cooperation of the programs stored in the storage unit  201  and an operating system (OS). The control unit  202  may include a plurality of processors like multi-core processors, and control the entire communication apparatus  101  by the plurality of processors. 
     The control unit  202  controls a functional unit  203  to perform predetermined processing such as imaging, printing, and projection. The functional unit  203  is hardware for the communication apparatus  101  to perform predetermined processing. For example, if the communication apparatus  101  is a camera, the functional unit  203  is an imaging unit and performs imaging processing. For example, if the communication apparatus  101  is a printer, the functional unit  203  is a printing unit and performs print processing. For example, if the communication apparatus  101  is a projector, the functional unit  203  is a projection unit and performs projection processing. Data to be processed by the functional unit  203  may be data stored in the storage unit  201  or data communicated from another communication apparatus via a communication unit  206  to be described below. 
     An input unit  204  accepts various operations from a user. An output unit  205  makes various outputs to the user. The outputs of the output unit  205  include at least one of the following: display on a screen, an information output using a liquid crystal display (LCD) or a light-emitting diode (LED), an audio output from a speaker, and a vibration output. Both the input unit  204  and the output unit  205  may be implemented by one module like a touch panel. 
     The communication unit  206  performs control on wireless communication compliant with the IEEE 802.11 series standard and performs control on Transmission Control Protocol (TCP)/IP communication. The communication unit  206  may perform control on User Datagram Protocol (UDP) communication instead of or in addition to TCP communication. 
     The communication unit  206  controls an antenna  207  to transmit and receive wireless signals for wireless communication. The communication apparatus  101  communicates contents such as image data, document data, and video data with other communication apparatuses (base stations and apparatuses connected over the base stations) via the communication unit  206 . The communication unit  206  may also be capable of communications compliant with other communication standards such as Bluetooth (registered trademark), near field communication (NFC), and the Ethernet. 
       FIG. 3  illustrates software function blocks implemented by the control unit  202  of the communication apparatus  101  reading programs stored in the storage unit  201 . At least part of the software function blocks illustrated in  FIG. 3  may be implemented by hardware. In the case of hardware implementation, for example, dedicated circuits may be generated from the programs for implementing the respective function blocks on a field programmable gate array (FPGA) by using a predetermined compiler, and the generated dedicated circuits may be used as hardware modules having the functions of the corresponding software modules. Like an FPGA, gate array circuits may be formed for hardware implementation. 
     A packet transmission unit  301  packetizes transmission data the communication apparatus  101  transmits into packets compliant with the IEEE 802.11 series standard, and transmits the packets to a partner apparatus or apparatuses (here, the base stations  102  and  103 ) via a wireless network. A packet reception unit  302  receives packets compliant with the IEEE 802.11 series standard from the partner apparatus(es) (here, the base stations  102  and  103 ) via the wireless network, and obtains data included in the packets. The packet transmission unit  301  and the packet reception unit  302  transmit and receive packets by using the communication unit  206 . 
     A management unit  303  manages communication parameters for connecting to the networks  112  and  113 . Communication parameters include an operation channel of a wireless network, an identifier (for example, SSID) of the wireless network, an encryption key (for example, passphrase) used in the wireless network, and information about an encryption method and authentication method used in the wireless network. The communication parameters may include only some of the pieces of such information. The communication parameters for connecting to the networks  112  and  113  may be referred to as communication parameters for connecting to the base stations  102  and  103 . 
     The management unit  303  further manages reception signal intensities from the base stations  102  and  103 , and threshold information about the reception signal intensities. The management unit  303  manages such information by using the storage unit  201 . The threshold information will be described to be stored in the storage unit  201  in advance. However, this is not restrictive. The threshold information may be settable by the user, or obtainable from a base station or an external apparatus. 
     A handover control unit  304  determines whether to switch the wireless network to be connected, based on management signals received from base stations around and parameter information stored in the communication apparatus  101 . The handover control unit  304  performs the handover processing for switching the wireless network to be connected based on the determination. The handover control unit  304  may further be able to perform processing for reconnection to the originally-connected wireless network if the handover processing fails. 
     The handover processing includes disconnection processing by which the communication apparatus  101  disconnects from the wireless network in connection, and connection processing by which the communication apparatus  101  connects to the new wireless network to be connected. Here, the handover control unit  304  supports connection processing both for connection using the WPA-Enterprise method and for connection using the FILS method. The handover control unit  304  performs the handover processing by using the communication unit  206 . 
       FIG. 4  illustrates a flowchart to be started when the communication apparatus  101  is connected to a wireless network (here, network  112 ). The flowchart may be started if the communication apparatus  101  is in connection with a wireless network and a predetermined instruction (such as a wireless network search instruction) is given by the user. The flowchart may be started if the reception signal intensity of a signal from the base station constructing the wireless network with which the communication apparatus  101  is in connection falls below a predetermined threshold. The flowchart may be started if a predetermined time has elapsed since the connection of the communication apparatus  101  to the wireless network, or if the communication apparatus  101  has moved by a predetermined distance since the connection to the wireless network. The flowchart may be started based on a combination of such conditions. 
     The flowchart illustrated in  FIG. 4  is implemented by the control unit  202  reading and executing a program stored in the storage unit  201  of the communication apparatus  101 . Part or all of the steps illustrated in the flowchart of  FIG. 4  may be implemented by hardware such as an application specific integrated circuit (ASIC). In the flowchart, a network will be referred to simply as “NW”. 
     If the flowchart illustrated in  FIG. 4  is started, then in step S 401 , the communication apparatus  101  performs a wireless LAN scan to detect wireless networks existing around. For the wireless LAN scan, the communication apparatus  101  detects wireless networks by transmitting a probe request signal (Probe Request) and receiving probe response signals (Probe Response) from base stations receiving the probe request signal. Such a method is referred to as active scanning. However, this is not restrictive. Passive scanning in which the communication apparatus  101  detects wireless networks by receiving beacon signals (Beacon) transmitted from base stations may be used. 
     If, as a result of the wireless LAN scan, no network having the same SSID as that of the wireless network in which the communication apparatus  101  is currently participating is detected (NO in step S 402 ), the processing returns to step S 401 . In step S 401 , the communication apparatus  101  retries a wireless LAN scan. In retrying a wireless LAN scan, the communication apparatus  101  may wait for a certain time before retrying the wireless LAN scan so that processing load does not increase because wireless LAN scans are successively performed in a short time. If, in any of the steps to be described below, the processing returns to step S 401  and the communication apparatus  101  retries a wireless LAN scan, the communication apparatus  101  may also wait for a certain time before retrying the wireless LAN scan. 
     On the other hand, if a wireless network having the same SSID is detected (YES in step S 402 ), the processing proceeds to step S 403 . In step S 403 , the communication apparatus  101  compares the reception signal intensity of the signal received from the base station constructing the detected wireless network with a threshold stored in the storage unit  201  in advance. In the flowchart, the “reception signal intensity of the signal received from the base station constructing the detected wireless network” is referred to simply as “reception signal intensity of detected NW”. 
     The threshold is a value indicating a reception signal intensity for checking whether communication with the detected base station can be performed with a sufficient field intensity, and is stored in the storage unit  201  in advance. The reception signal intensity is measured by the packet reception unit  302 . The threshold may be settable by the user, or obtainable from a base station or an external apparatus. The threshold may be the same value as the “predetermined threshold” that can be used as a starting condition of the present flowchart. The threshold may be the reception signal intensity of the signal received from the base station constructing the wireless communication with which the communication apparatus  101  is currently in connection. 
     If the reception signal intensity is lower than or equal to the threshold (NO in step S 403 ), the processing returns to step S 401 . In step S 401 , the communication apparatus  101  retries a wireless LAN scan. Alternatively, if the reception signal intensity is equal to the threshold, it may be determined YES in step S 403  and the processing may proceed to S 404 . 
     If the reception signal intensity is higher than the threshold (YES in step S 403 ), the processing proceeds to step S 404 . In step S 404 , the communication apparatus  101  analyzes the content of the signal received from the base station, and determines whether the wireless network constructed by the base station is capable of connection using the FILS method. Suppose here that the signal transmitted from the base station (such as Beacon and Probe Response) includes bit information (FILS bit) indicating whether the wireless network constructed by the base station is capable of connection using the FILS method. The communication apparatus  101  determines whether the wireless network is capable of connection using the FILS method, by referring to the bit information. Being capable of connection using the FILS method will hereinafter be referred to as being FILS-capable. Being incapable of connection using the FILS method will be referred to as not being FILS-capable. 
     If the detected wireless network is not FILS-capable (NO in step S 404 ), the processing returns to step S 401 . In step S 401 , the communication apparatus  101  retries a wireless LAN scan. On the other hand, if the detected wireless network is FILS-capable (YES in step S 404 ), the processing proceeds to step S 405 . In step S 405 , the communication apparatus  101  leaves the wireless network in connection. In step S 406 , the communication apparatus  101  performs connection processing for connecting to the detected wireless network by using the FILS method. Specifically, the communication apparatus  101  transmits and receives messages compliant with the FILS method to/from the base station constructing the wireless network, and performs authentication processing and IP address assignment processing. 
     If the connection processing in step S 406  fails, i.e., the connection to the wireless network is not normally completed (NO in step S 407 ), the processing proceeds to step S 408 . In step S 408 , the communication apparatus  101  performs reconnection processing with the wireless network left in step S 405 . In the reconnection processing, like in step S 404 , the communication apparatus  101  determines whether the wireless network to be reconnected is FILS-capable. If the wireless network is FILS-capable, the communication apparatus  101  performs the reconnection processing by using the FILS method. On the other hand, if the wireless network is not FILS-capable, the communication apparatus  101  performs the reconnection processing by using WPA-Enterprise and DHCP. After the reconnection processing, the processing returns to step S 401 . In step S 401 , the communication apparatus  101  retries a wireless LAN scan. 
     On the other hand, if the connection processing in step S 406  is successful (YES in step S 407 ), the wireless LAN handover processing ends. That is, the processing illustrated in  FIG. 4  ends. If the wireless LAN handover processing ends, the processing may return to step S 401  so that the communication apparatus  101  may retry a wireless LAN scan. The processing illustrated in  FIG. 4  may be started again according to the foregoing starting condition. 
       FIG. 5  illustrates a sequence of processing implemented between the communication apparatus  101  and the base stations  102  and  103 . 
     In F 501 , the communication apparatus  101  initially performs connection processing by the FILS method with the network  112  constructed by the base station  102 . In response to the completion of the connection processing, the communication apparatus  101  starts the wireless LAN handover processing ( FIG. 4 ). 
     In step S 401 , the communication apparatus  101  performs a wireless LAN scan. In F 502 , the communication apparatus  101  broadcasts a probe request signal. In F 503 , the communication apparatus  101  receives a probe response signal from the base station  102 . At this point in time, the communication apparatus  101  lies outside the coverage of the network  113  constructed by the base station  103 . The communication apparatus  101  therefore does not receive a probe response signal from the base station  103 . 
     The communication apparatus  101  then moves into the coverage of the network  113 . In F 504 , the communication apparatus  101  broadcasts a probe request signal again. After the broadcast, in F 505  and F 506 , the communication apparatus  101  receives probe response signals from the base stations  102  and  103 . The probe response signal received in F 506  includes, as the SSID of the network  113 , the same SSID information as that of the network  112 . The probe response signal also includes information indicating that the network  113  is capable of connection processing using the FILS method. Suppose that the reception signal intensity of this probe response signal is higher than the threshold described in step S 403  of  FIG. 4 . 
     In steps S 402 , S 403 , and S 404 , the communication apparatus  101  checks that the network  113  is a wireless network satisfying a handover condition (YES in step S 404 ), based on the content and the reception signal intensity of the received probe response signal. In F 507 , the communication apparatus  101  leaves the network  112  in connection. The communication apparatus  101  here transmits a disassociation signal for requesting disconnection of the wireless communication to the base station  102 . In F 508 , the communication apparatus  101  performs connection processing with the network  113  by using the FILS method. 
     As described above, according to the present exemplary embodiment, the communication apparatus  101  can switch whether to perform handover processing according to whether the candidate wireless network for handover is capable of connection using the FILS method. This enables quick switching of the wireless network to connect to while preventing the occurrence of a prolonged communication-disabled period because of the handover processing, and thus improves user convenience. 
     In the first exemplary embodiment, a method for performing handover processing only on a FILS-capable wireless network has been described. In a second exemplary embodiment, a method for performing handover processing even on a not FILS-capable wireless network depending on situations will be described. A configuration of a communication system according to the present exemplary embodiment and a hardware configuration and software function blocks of a communication apparatus  101  are similar to those of the first exemplary embodiment. A description thereof will thus be omitted. 
       FIG. 6  illustrates a flowchart implemented by the control unit  202  reading and executing a program stored in the storage unit  201  of the communication apparatus  101 . The starting condition of the flowchart is similar to that of  FIG. 4 . 
     Steps S 601  to S 608  of  FIG. 6  are similar to steps S 401  to S 408  of  FIG. 4 , respectively. A description thereof will thus be omitted. Now, an operation in a case where the wireless network detected in step S 601  is not FILS-capable (NO in step S 604 ) will be described below. 
     If the wireless network is not FILS-capable (NO in step S 604 ), the processing proceeds to step S 609 . In step S 609 , the communication apparatus  101  compares the reception signal intensity of the signal received from the base station constructing the wireless network currently in connection and a predetermined threshold. Here, the reception signal intensity is compared with a second threshold different from the threshold (referred to as a first threshold) used in the comparison of step S 603 . The second threshold is lower than the first threshold. The second threshold may be stored in the storage unit  201  in advance. The second threshold may be settable by the user, or obtainable from a base station or an external apparatus. A value having a predetermined difference from the first threshold may be used as the second threshold. 
     If the reception signal intensity is higher than or equal to the second threshold (NO in step S 609 ), the processing returns to step S 601 . In step S 601 , the communication apparatus  101  retries a wireless LAN scan. On the other hand, if the reception signal intensity is lower than the second threshold (YES in step S 609 ), the processing proceeds to step S 610 . In step S 610 , the communication apparatus  101  leaves the wireless network in connection. Alternatively, if the reception signal intensity is equal to the second threshold, it may be determined YES in step S 609  and the processing may proceed to S 610 . In step S 611 , the communication apparatus  101  having left the wireless network performs connection processing for connecting to the detected wireless network according to the WPA-Enterprise method. In step S 611 , after the completion of authentication by the WPA-Enterprise method, the communication apparatus  101  performs IP address assignment processing by DHCP. 
     If the connection processing in step S 611  fails (NO in step S 612 ), the processing proceeds to step S 613 . In step S 613 , the communication apparatus  101  performs reconnection processing with the wireless network left in step S 610 . The processing then returns to step S 601 . On the other hand, if the connection processing in step S 606  is successful (YES in step S 612 ), the wireless LAN handover processing illustrated in  FIG. 6  ends. 
     If the wireless LAN handover processing ends, the processing may return to step S 601  so that the communication apparatus  101  may retry a wireless LAN scan. The processing illustrated in  FIG. 6  may be started again according to the foregoing starting condition. 
       FIG. 7  illustrates a sequence of processing implemented between the communication apparatus  101  and the base stations  102  and  103 . In the present exemplary embodiment, suppose that the base station  103  does not support 11ai, and the communication apparatus  101  is unable to perform connection processing by the FILS method with the network  113 . 
     In F 701 , the communication apparatus  101  initially performs connection processing by the FILS method with the network  112  constructed by the base station  102 . In response to the completion of the connection processing, the communication apparatus  101  starts the wireless LAN handover processing ( FIG. 6 ). 
     In step S 601 , the communication apparatus  101  performs a wireless LAN scan. In F 702 , the communication apparatus  101  broadcasts a probe request signal. In F 703 , the communication apparatus  101  receives a probe response signal from the base station  102 . At this point in time, the communication apparatus  101  lies outside the coverage of the network  113  constructed by the base station  103 . The communication apparatus  101  therefore does not receive a probe response signal from the base station  103 . 
     The communication apparatus  101  then moves into the coverage of the network  113 . In F 704 , the communication apparatus  101  broadcasts a probe request signal again. After the broadcast, in F 705  and F 706 , the communication apparatus  101  receives probe response signals from the base stations  102  and  103 . 
     The probe response signal received from the base station  103  in F 706  includes, as the SSID of the network  113 , the same SSID information as that of the network  112 . The probe response signal also includes information indicating that the network  113  is not capable of connection processing using the FILS method. Suppose that the reception signal intensity of the probe response signal is higher than the first threshold. Suppose also that the reception signal intensity of the probe response signal received from the base station  102  in F 705  is lower than the second threshold. 
     Based on the content and the reception signal intensities of the received probe response signals, the communication apparatus  101  determines that the network  113  is not capable of connection processing using the FILS method (NO in step S 604 ), and to switch the connection destination (YES in step S 609 ). 
     In F 707 , the communication apparatus  101  then leaves the network  112  in connection. The communication apparatus  101  here transmits a disassociation signal for requesting disconnection of wireless communication to the base station  102 . In F 708 , the communication apparatus  101  performs connection processing with the network  113  by using the WPA-Enterprise. Specifically, the communication apparatus  101  performs the connection processing by transmitting and receiving messages compliant with the WPA-Enterprise method and DHCP to/from the base station  103 . 
     As described above, according to  FIGS. 6 and 7 , if the field intensity from the base station in connection is insufficient and the detected wireless network is not capable of FILS (11ai), the communication apparatus  101  performs handover processing. As a result, the communication apparatus  101  can perform communication in a better radio wave environment while preventing deterioration in communication performance, such as a drop in communication speed, due to a lower field intensity resulting from staying in the wireless network in connection. 
     In step S 609 , the communication apparatus  101  may determine whether the field intensity from the base station constructing the detected network is lower than a third threshold. The third threshold is a value greater than the first threshold. If the field intensity from the base station constructing the detected network is lower than the third threshold, the processing returns to step S 601 . On the other hand, if the field intensity from the base station constructing the detected network is higher than or equal to the third threshold, the processing proceeds to step S 610 . 
     With such a configuration, if the detected wireless network is FILS-capable, handover processing can be performed based on the first threshold. If the detected wireless network is not FILS-capable, handover processing can be performed based on the third threshold which is higher than the first threshold. In such a manner, whether to perform handover processing can be determined based on different thresholds depending on whether the detected wireless network is FILS-capable. In particular, since the third threshold has a value greater than the first threshold, handover processing is more likely to be performed with a FILS-capable wireless network than with a not FILS-capable one. 
     A third exemplary embodiment describes a method for performing, if connection processing using the FILS method with a detected wireless network fails, connection using the WPA-Enterprise method depending on the field intensity from the base station constructing the previously-connected wireless network. A configuration of a communication system according to the present exemplary embodiment and a hardware configuration and software function blocks of a communication apparatus  101  are similar to those of the first exemplary embodiment. A description thereof will thus be omitted. 
       FIG. 8  illustrates a flowchart implemented by the control unit  202  reading and executing a program stored in the storage unit  201  of the communication apparatus  101 . The starting condition of the flowchart is similar to that of  FIG. 4 . 
     Steps S 801  to S 807  of  FIG. 8  are similar to steps S 401  to S 407  of  FIG. 4 , respectively. A description thereof will thus be omitted. Now, an operation in a case where the connection processing using the FILS method with the wireless network detected in step S 801  fails (NO in step S 807 ) will be described. The connection processing using the FILS method can fail in cases such as when the settings of the authentication processing using the FILS method are not properly made in the base station. Without the proper settings of the authentication processing using the FILS method, the connection processing using FILS fails even if the base station transmits a signal including information indicating that the wireless network is capable of connection processing using the FILS method. 
     If the connection processing using the FILS method fails (NO in step S 807 ), the processing proceeds to step S 808 . In step S 808 , the communication apparatus  101  compares the reception signal intensity of the signal received from the base station constructing the wireless network left in step S 805  with a predetermined threshold. Here, a value similar to the second threshold according to the second exemplary embodiment is used as the predetermined threshold. 
     If the reception signal intensity is lower than or equal to the second threshold (NO in step S 808 ), the processing proceeds to step S 811 . In step S 811 , the communication apparatus  101  reconnects to the wireless network left in step S 805 . The processing then returns to step S 801 . On the other hand, if the reception signal intensity is higher than the second threshold (YES in step S 808 ), the processing proceeds to step S 809 . In step S 809 , the communication apparatus  101  performs connection processing for connecting to the wireless network left in step S 805 . Here, the communication apparatus  101  transmits and receives messages according to the WPA-Enterprise method to/from the base station constructing the wireless network and connects to the base station. The communication apparatus  101  then performs IP address assignment processing by DHCP with the base station. Alternatively, if the reception signal intensity is equal to the second threshold, it may be determined YES in step S 808  and the processing may proceed to step S 809 . 
     If the connection processing in step S 809  fails (NO in step S 810 ), the processing proceeds to step S 811 . In step S 811 , the communication apparatus  101  reconnects to the wireless network left in step S 805 . The processing then returns to step S 801 . On the other hand, if the connection processing in step S 809  is successful (YES in step S 810 ), the wireless LAN handover processing illustrated in  FIG. 8  ends. 
     If the wireless LAN handover processing ends, the processing may return to step S 801  so that the communication apparatus  101  may retry a wireless LAN scan. The processing illustrated in  FIG. 8  may be started again according to the foregoing starting condition. 
       FIG. 9  illustrates a sequence of processing implemented between the communication apparatus  101  and the base stations  102  and  103 . In the present exemplary embodiment, the base stations  102  and  103  support 11ai. The communication  101  can perform connection processing by the FILS method with the networks  112  and  113 . 
     In F 901 , the communication apparatus  101  initially performs connection processing by the FILS method with the network  112  constructed by the base station  102 . In response to the completion of the connection processing, the communication apparatus  101  starts the wireless LAN handover processing ( FIG. 8 ). 
     In step S 801 , the communication apparatus  101  performs a wireless LAN scan. In F 902 , the communication apparatus  101  broadcasts a probe request signal. In F 903 , the communication apparatus  101  receives a probe response signal from the base station  102 . At this point in time, the communication apparatus  101  lies outside the coverage of the network  113  constructed by the base station  103 . The communication apparatus  101  therefore does not receive a probe response signal from the base station  103 . 
     The communication apparatus  101  then moves into the coverage of the network  113 . In F 904 , the communication apparatus  101  broadcasts a probe request signal again. After the broadcast, in F 905  and F 906 , the communication apparatus  101  receives probe response signals from the base stations  102  and  103 . 
     The probe response signal received from the base station  103  in F 906  includes, as the SSID of the network  113 , the same SSID information as that of the network  112 . The probe response signal also includes information indicating that the network  113  is capable of connection processing using the FILS method. Suppose that the reception signal intensity of the probe response signal is higher than the first threshold. Suppose also that the reception signal intensity of the probe response signal received from the base station  102  in F 905  is lower than the second threshold. 
     Based on the content and the reception signal intensities of the received probe response signals, the communication apparatus  101  determines to switch the connection destination to the network  113  (YES in step S 804 ). In F 907 , the communication apparatus  101  leaves the network  112  in connection. Here, the communication apparatus  101  transmits a disassociation signal for requesting disconnection of wireless communication to the base station  102 . In F 908 , the communication apparatus  101  performs connection processing with the network  113  by using the FILS method. 
     Suppose here that the connection processing by the FILS method fails. After the failure of the connection processing, the communication apparatus  101  determines to retry connection processing with the base station  103  (YES in step S 808 ). The communication apparatus  101  then performs connection processing with the network  113  by using WPA-Enterprise. Specifically, in F 909 , the communication apparatus  101  performs the connection processing by transmitting and receiving messages compliant with the WPA-Enterprise method and DHCP to/from the base station  103 . 
     As described above, according to  FIGS. 8 and 9 , the communication apparatus  101 , after a failure of connection processing by the FILS method, performs handover processing again with the connection-failed wireless network depending on the field intensity from the base station constructing the previously-connected wireless network. The communication apparatus  101  can thereby perform communication in a better radio wave environment while preventing deterioration in communication performance due to not performing handover even if the handover processing using the FILS method fails. 
     The first to third exemplary embodiments have been described above. According to the foregoing exemplary embodiments, the communication apparatus  101  automatically performs a wireless LAN handover by the FILS method with FILS (11ai)-capable wireless networks (base stations). The communication apparatus  101  can thereby achieve seamless data communication without the user&#39;s awareness of which base station is in connection. 
     The exemplary embodiments may be combined as appropriate. For example, if NO in step S 804  of  FIG. 8 , the processing may proceed to step S 609  of  FIG. 6 . Which processing to perform may be switched according to user settings or a state of the communication apparatus  101 . 
     In the foregoing exemplary embodiments, in step S 609  of  FIG. 6  and step S 808  of  FIG. 8 , the communication apparatus  101  determines whether to perform handover based on the second threshold. However, the communication apparatus  101  may instead, or additionally, make the determination according to whether the communication apparatus  101  is communicating data (data communication is in process) via the wireless network in connection. 
     Specifically, if data communication is in process (NO in step S 609 , or NO in step S 808 ), the communication apparatus  101  may avoid performing handover processing. If data communication is not in process (YES in step S 609 , or YES in step S 808 ), the communication apparatus  101  may perform handover. Whether data communication is in process may be determined based on whether a data packet is currently being transmitted or received, or based on whether there is a communication session established with a specific apparatus. The determination may be made based on the presence or absence of data addressed to a specific apparatus. 
     Handover processing using the WPA-Enterprise method, which takes longer to establish connection compared to the FILS method, can thereby be performed at timing not affecting data communication. This also improves user convenience. 
     In the foregoing exemplary embodiments, the communication apparatus  101  determines whether the FILS method is supported, based on the signals from the base stations  102  and  103 . However, this is not restrictive. The communication apparatus  101  may determine whether 11ai is supported, based on the signals from the base stations  102  and  103 . This can provide similar effects. 
     In performing handover by the WPA-Enterprise method, the communication apparatus  101  may make the user select whether to perform the handover. Connection by the WPA-Enterprise method, which takes longer to establish connection compared to the FILS method, can thereby be performed with the consent of the user. This also improves user convenience. 
     In the foregoing exemplary embodiments, a wireless network having the same SSID is detected as the handover-destination wireless network (in steps S 402 , S 602 , and S 802 ). However, the communication apparatus  101  may detect a handover-capable wireless network that has a different SSID. In such a case, the determinations in steps S 402 , S 602 , and S 802  may be YES. For example, if the communication apparatus  101  stores, in the storage unit  201 , communication parameters needed to connect to a wireless network, the wireless network is a handover-capable one. Examples of the communication parameters include an encryption key (for example, passphrase) used in the wireless network and information about an encryption method and authentication method used in the wireless network. Even in such a case, one or more effects described above can be obtained. 
     The exemplary embodiments of the present invention can be implemented by processing for supplying a program for implementing one or more functions of the foregoing exemplary embodiments to a system or an apparatus via a network or a storage medium, and reading and executing the program by one or more processors of a computer of the system or apparatus. An exemplary embodiment of the present invention can also be implemented by a circuit (for example, an ASIC) that implements the one or more functions. 
     According to an exemplary embodiment of the present invention, handover processing can be performed in consideration of whether the handover-destination wireless network is capable of connection using the FILS method. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), 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) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. 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. 2017-226811, filed Nov. 27, 2017, which is hereby incorporated by reference herein in its entirety.