Abstract:
A first station for communicating with a second station is disclosed. The first station may include a storage unit configured to store relationship information defining a communication relationship between the first station and the second station. The first station may also include a communication unit configured to communicate with the second station and with an access point. The communication relationship may be maintained when the communication unit begins communicating with the access point.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority of Japanese Patent Application No. 2009-260293, filed on Nov. 13, 2009, the entire content of which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a wireless communication device, a wireless communication system, a program and a wireless communication method. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, a wireless LAN (Local Area Network) system typified by IEEE (Institute of Electrical and Electronics Engineers) 802.11 has become widespread in place of wired networks, because the degree of freedom of a device can be enlarged. For example, as described in JP 2008-283590 A, a wireless LAN system defined in IEEE802.11 is configured from a group of wireless communication devices including an access point that operates as a master device and a plurality of stations that operates as slaves, and a plurality of stations are connected to an access point. 
         [0006]    Moreover, a frequency to use in the wireless LAN system is, in general, configured autonomously by a master device or a user. In the wireless LAN system defined in IEEE802.11, a slave device detects the frequency that the master uses, and connects to the master device at the detected frequency to configure a group of the wireless communication devices. Note that the slave device may detect the frequency that the master uses by a beacon transmitted from the master device as notification information, or may detect the frequency that the master uses by transmitting and receiving a probe request and a probe response. 
       SUMMARY 
       [0007]    Here, if there are two groups of wireless communication devices which use different frequencies respectively, the groups cannot communicate with each other since the frequencies each group uses are different. For this reason, in order to communicate between wireless communication devices belonging to different groups, connections between a plurality of wireless communication devices in one of the groups should be disconnected and connect the plurality of wireless communication devices to wireless communication devices in another group. 
         [0008]    However, if the connection between the plurality of wireless communication devices in one group are disconnected, communications between the wireless communication devices are lost. Moreover, there has been a problem that it takes time to set an encryption (for example, WPS or WPA) for security again as connection processing, and that it is difficult for users. 
         [0009]    In light of the foregoing, it is desirable to provide a wireless communication device, a wireless communication system, a program and a wireless communication method, which are novel and improved, and which are capable of connecting to another group while maintaining connections between wireless communication devices which configure a same group. 
         [0010]    Accordingly, there is disclosed a first station for communicating with a second station. The first station may include a storage unit configured to store relationship information defining a communication relationship between the first station and the second station. The first station may also include a communication unit configured to communicate with the second station and with an access point. The communication relationship may be maintained when the communication unit begins communicating with the access point. 
         [0011]    There is also disclosed a method of operating a first station. A processor may execute a program to cause the first station to perform the method. The program may be stored on a computer-readable storage medium. The method may include storing relationship information defining a communication relationship between the first station and a second station. The method may also include communicating with the second station and communicating with an access point. The communication relationship may be maintained when the first station begins communicating with the access point. 
         [0012]    Consistent with the embodiments of the present invention described above, it becomes possible to connect to another group while maintaining connections between wireless communication devices which configure a same group. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an explanatory diagram showing a configuration of a wireless communication system consistent with an embodiment of the present invention; 
           [0014]      FIG. 2  is an explanatory diagram showing a problem in a connection between groups; 
           [0015]      FIG. 3  is a function block diagram showing a configuration of a master device as an example of a wireless communication device according to the present embodiment; 
           [0016]      FIG. 4  is a sequence diagram showing an example of a first operation to connect different groups; 
           [0017]      FIG. 5  is an explanatory diagram showing a configuration of an Extended Channel Switch Announcement message; 
           [0018]      FIG. 6  is an explanatory diagram showing a connection relationship between each of the wireless communication devices after performing a connection operation between groups; 
           [0019]      FIG. 7  is a sequence diagram showing an example of a second operation to connect different groups; 
           [0020]      FIG. 8  is a sequence diagram showing an example of a third operation to connect different groups; 
           [0021]      FIG. 9  is an explanatory diagram showing a configuration example of DFS information; and 
           [0022]      FIG. 10  is a sequence diagram showing an example of a fourth operation to connect different groups. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Hereinafter, embodiments of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
         [0024]    In this specification and the drawings, each of a plurality of structural elements having substantially the same function is distinguished by affixing a different alphabetical letter to the same reference numeral in some cases. For example, a plurality of structural elements having substantially the same function are distinguished like slave devices  22 A and  22 B where necessary. However, when there is no particular need to distinguish between a plurality of structural elements having the same function, they are denoted by the same reference numeral. For example, when there is no particular need to distinguish between the slave devices  22 A and  22 B, they are referred to simply as the slave devices  22 . 
         [0025]    Embodiments of the invention will be explained in the following order described below. 
         [0026]    1. An overall configuration of a wireless communication system 
         [0027]    2. A configuration of a wireless communication device 
         [0028]    3. Connection operations between groups
       3-1. An example of a first operation   3-2. An example of a second operation   3-3. An example of a third operation   3-4. An example of a fourth operation   4. Conclusion       
 
       1. AN OVERALL CONFIGURATION OF A WIRELESS COMMUNICATION SYSTEM 
       [0034]    At first, the overall configuration of a wireless communication system will be explained with reference to  FIG. 1 . 
         [0035]      FIG. 1  is an explanatory diagram showing a configuration of a wireless communication system. As shown in  FIG. 1 , the wireless communication system is configured from a plurality of groups of wireless communication stations (i.e., devices). 
         [0036]    Specifically, a group 1 includes a master device  20 A, and slave devices  22 A and  22 B which are connecting to the master device  20 A. In the group 1, the master device  20 A controls communication, and a frequency 1 is used for the communication. Note that, using WiFi Direct, it is possible that even if the master  20 A is not a dedicated access point, it can perform operations of an access point, such as a beacon transmission, and connect a plurality of the slave devices  22  as shown in  FIG. 1 . It should be understood that the term “access point,” as used herein, has the same meaning as in IEEE802.11-2007. In general, a router equipped with a built-in access point, called a wireless LAN router, is a dedicated access point. In the example herein, the master device  20 A is a PC (personal computer) and is not a dedicated access point. 
         [0037]    Moreover, a group 2 includes a master device  20 C, and slave devices  22 C and  22 D which are connecting to the master device  20 C. In the group 2, the master device  20 C controls communication, and a frequency 2, which is different from the frequency the group 1 uses, is used for the communication. Here, the master device  20 C is a dedicated access point. 
         [0038]    Note that it may be or may not be determined, at a time of production of each wireless communication device, which wireless communication device is to operate as the master device  20  and which wireless communication device is to operate as the slave device  22 . In a case where it is not determined, it may be determined by negotiation which wireless communication device is to operate as the master device and which wireless communication device is to operate as the slave device among a plurality of wireless communication devices. 
         [0039]    Data transmitted between the master device  20  and the slave device  22  which belong to the same group is music data such as music, a radio program or the like, video data such as a movie, a television program, a vide program, a photograph, a document, a picture, a table or the like, a game data, a software or the like. 
         [0040]    In  FIG. 1 , a case where the master device  22 C is an access point and the master device  20 A is a PC (Personal Computer) is illustrated as examples of the master devices  20 , and cellular phones ( 22 A,  22 C), a mobile music player ( 22 B), and an imaging device ( 22 D) are illustrated as examples of the slave devices  22 , however, the wireless communication devices such as the master device  20  and the slave devices  22  are not limited to these examples. For example, the wireless communication device may be an information processing apparatus such as a home video processing device (a DVD recorder, a video cassette recorder, or the like), a personal digital assistant (PDA), a home game machine, a home appliance, a portable video processing device, a portable game machine, or the like. 
         [0041]    Here, in order to communicate between the wireless communication devices which belong to the different groups, there may be a method that disconnects the connection between a plurality of wireless communication devices in one group and connects the plurality of wireless communication devices to wireless communication devices in the other group. For example, the master device  20 A, the slave devices  22 A and  22 B that belong to the group 1, as shown in  FIG. 2 , may disconnect connection between the master device  20 A, and the slave devices  22 A and  22 B and may reconnect to the master device  22 C that belongs to the group 2. 
         [0042]    However, if the connection between the master device  20 A, the slave devices  22 A and  22 B is disconnected, communication of the slave devices  22 A and  22 B are lost. Moreover, there may be a problem that if each of the master device  20 A, and the slave devices  22 A and  22 B connects to the master device  20 C that belongs to the group 2, it will increase the processing load and time. 
         [0043]    Hence, the present embodiments have been invented considering the above issue as a focused point. According to the present embodiments, it becomes possible to connect, while maintaining connections between wireless communication devices which configure a same group, to another group. Hereinafter, the detail of such present embodiments will be explained. 
       2. A CONFIGURATION OF A WIRELESS COMMUNICATION DEVICE 
       [0044]      FIG. 3  is a function block diagram showing a configuration of a master device  20  as an example of a wireless communication device according to the present embodiment. Note that the detail explanation on the slave devices  22  will be omitted since the slave device  22  can be configured to be substantially identical to the master device  20 . 
         [0045]    As shown in  FIG. 3 , the master device  20  includes a data processing unit  204 , a transmission processing unit  208 , a wireless interface unit  212 , a control unit  216 , a detection unit  220 , a memory  230  and an antenna  234 . 
         [0046]    At the time of transmission, the data processing unit  204  creates various data frames and various data packets in response to a request from, for example, a higher-level layer to supply the data frames and the data packets to the transmission processing unit  208 . The transmission processing unit  208  at the time of transmission performs processing of addition of error detection codes such as various data headers or FCSs (Frame Check Sequences) to the packets created by the data processing unit  204 , and provides the processed data to the wireless interface unit  212 . The wireless interface unit  212  creates a modulation signal in a frequency band of a carrier wave from the data received from the transmission processing unit  208  and causes the antenna  234  to transmit the modulation signal as a wireless signal. 
         [0047]    Further, in a receiving operation, the wireless interface unit  212  down-converts the wireless signal received by the antenna  234  and converts the wireless signal into a bit string to decode various data frames. The transmission processing unit  208  analyses a header added to the data frame supplied from the wireless interface unit  212 . When the transmission processing unit  208  confirms that the data frame has no error based on the error detection code, the transmission processing unit  208  supplies the data frame to the data processing unit  204 . The data processing unit  204  processes and analyses the data frame and the data packet supplied from the transmission processing unit  208 . Thus, the data processing unit  204 , the transmission processing unit  208 , the wireless interface unit  212  and the antenna  234  function as a communication unit. 
         [0048]    The control unit  216  controls receiving and transmitting operations of each of the data processing unit  204 , the transmission processing unit  208  and the wireless interface unit  212 . For example, the control unit  216  can perform operations such as determination of a frequency to use, creation of a control message (notification information such as a beacon, a beacon acknowledgement, a probe request and a probe response), issuance of a transmission command for the control message, and interpretation of the control message. 
         [0049]    The detection unit  220  detects frequency information indicative of a frequency that is used by other groups existing around. For example, when receiving a probe response with respect to a probe request from other group, the detection unit  220  detects the frequency of the probe response. 
         [0050]    The memory  230  plays the role of a work area for the data processing by the control unit  216 , and has a function of a storage unit (i.e. a non-transitory storage medium) for holding various types of data. The data may include relationship information defining a communication relationship between the master device  20  and a slave device  22  and/or another master device  20 . For example, the relationship information may indicate that the master device  20  is a master device relative to the slave device  22  and/or may indicate encryption information shared between the master device  20  and the slave device  22 . For example, the relationship information may include a passphrase, a service set identifier (SSID), a preshared key (PSK), and/or a temporal key (TK). The memory  230  may be a storage medium such as a non-volatile memory, a magnetic disk, an optical disk, a magneto optical (MO) disk, and the like. The non-volatile memory may be an electrically erasable programmable read-only memory (EEPROM), and an erasable programmable ROM (EPROM), for example. Also, the magnetic disk may be a hard disk, a discoid magnetic disk, and the like. Also, the optical disk may be a compact disc (CD), a digital versatile disc recordable (DVD-R), a BD (Blu-ray disc; registered trademark), and the like. 
       3. CONNECTION OPERATIONS BETWEEN GROUPS 
       [0051]    The configuration of the wireless communication devices such as the master device  20  and the slave devices  22  are explained with reference to  FIG. 3 , as above. Next, examples of a first operation to a fourth operation of the present embodiment for connecting different groups will be explained in order. 
         [0052]    3-1. An Example of a First Operation 
         [0053]      FIG. 4  is a sequence diagram showing an example of a first operation to connect different groups. In an example illustrated in  FIG. 4 , the master device  20 A and the slave device  22 A are connected, and the master device  20 C is currently using the frequency 2 while the master device  20 A and the slave device  22 A are currently using the frequency 1. Here, in order to connect the master device  20 A and the slave device  22 A to the master device  20 C, when a push button as a connection trigger is pressed by a user in the master device  20 A and the master device  20 C (S 304 ), the master device  20 A starts an active frequency scanning operation to search a connection destination. 
         [0054]    Note that the above push button may be mounted physically on the master device  20 A and the master device  20 C, or may be displayed to be selectable on a screen. Moreover, the above push button may be, for example, a WPS Push Button, or may be other dedicated button. Further, the connection trigger may be a press of a push button or a PIN input. The active frequency scanning operation is an operation which transmits the probe request at all frequencies that the master device  20 A can use, and which waits for the probe response for a certain period of time. Further, the connection trigger for connecting the master device  20 A and the slave device  22 A to the master device  20 C is not limited to the button operation by the user, and it may set a configuration, for example, in which the connection trigger would be generated by a decision of devices such as the master device  20 A and the slave device  22 A when a predetermined condition is met. 
         [0055]    This active frequency scanning operation enables the master device  20 A to receive the probe response from the master device  20 C at the frequency 2 (S 312 ), and to detect the master device  20 C that is a wireless communication device to be connected to, and the frequency 2 that the master device  20 C is currently using. 
         [0056]    Afterward, the control unit  216  of the master device  20 A allows the communication unit to broadcast the Extended Channel Switch Announcement message defined in IEEE802.11y for changing the frequency to be used by the group. Hereinafter, the Extended Channel Switch Announcement message will be explained with reference to  FIG. 5 . 
         [0057]      FIG. 5  is an explanatory diagram showing a configuration of an Extended Channel Switch Announcement message. As shown in  FIG. 5 , this message includes Category, ActionValue, ChannelSwitchMode, NewRegulatoryClass, NewChannelNumber, and ChannelSwitchCount. 
         [0058]    NewChannelNumber is information indicating a frequency after changed (i.e., a new frequency), and ChannelSwitchCount is information indicating when communication with the new frequency will begin (i.e., a timing of frequency change (for example, information on how many beacon transmission timings ahead it is)). In the example of operation shown in  FIG. 4 , information indicating the frequency 2 is described in NewChannelNumber. 
         [0059]    Therefore, the slave device  22 A that receives this message can refer to NewChannelNumber and ChannelSwitchCount to change the frequency to use into the frequency 2 at the same timing as the master device  20 A (S 320 ). Note that  FIG. 4  omits the explanation on which other slave device  22 B currently connecting to the master device  20 A also performs the same operation as the slave device  22 A. That is, the slave device  22 B receives the Extended Channel Switch Announcement message to acknowledge when and to which frequency to change, then changes the frequency to use into the frequency 2. 
         [0060]    Thus, the frequency which the master device  20 A, the slave device  22 A and the master device  20 C use becomes the same. This enables the master device  20 A to operate as a master device of the slave device  22 A, and as a slave device of the master device  20 C as well. Note that the example herein shows a case where the master slave  20 A which is not a dedicated access point operates as a slave device of the master device C that is a dedicated access point, however, it may be a case where the master device  20 C operates as a slave device of the master device  20 A. 
         [0061]    Next, the master device  20 A performs a connection processing, defined in IEEE802.11 and WiFi Alliance, with respect to the master device  20 C. Specifically, the master device  20 A and the master device  20 C perform Authentication, Association, WPS procedure, 4-way handshake, or the like (S 324 , S 328 , S 332 ), and complete a security setting. As the result, a mutual data communication among the master device  20 C, the master device  20 A and the slave device  22 A can be realized (S 336 ). 
         [0062]      FIG. 6  is an explanatory diagram showing a connection relationship between each of the wireless communication devices after performing the above-mentioned connection operation between groups. As shown in  FIG. 6 , the master device  20 A can connect to the master device  20 C in the group 2 while maintaining the connection relationship with the slave devices  22 A and  22 B which belong to the same group. That is, according to the present embodiment, the slave devices  22 A and  22 B can communicate with wireless communication devices which belong to the group 2 without performing a connection processing respectively with the master device  20 C in the group 2. Note that the connection relationship shown in  FIG. 6  will be the same in the examples of the second, third, and fourth operations explained below. 
         [0063]    As described above, since the connection relationship between the master device  20 A and the slave devices  22 A and  22 B is maintained at the time of connection operation between groups, there is a merit that the processes for reconnection illustrated by the following examples will be not necessary. 
         [0064]    (1) Setting an encryption for security (for example, WPS/WPA) 
         [0065]    (2) Building a master-slave relationship to determine which of a master device or a slave device will be a role each device operates (a Group Owner negotiation process by WiFi Direct). 
         [0066]    Note that as shown in  FIG. 4 , maintaining the connection relationship between the master device  20 A and the slave devices  22  will be realized by not performing the disconnection process illustrated by the following examples. 
         [0067]    (1) One of either the master device  20 A or the slave devices  22  expressly transmits deauthentication frame for disconnecting the connection. 
         [0068]    (2) The master device  20 A is turned off, or is switched to operate at different frequency. In this case, the slave device  22  becomes unable to receive a beacon from the master device  20 A, determines that the master device  20 A does not exist, and internally treats it as being disconnected or transmits deauthentication frame. 
         [0069]    (3) The slave device  22  is turned off, or is switched to operate at different frequency. In this case, the master device  20  becomes unable to observe the transmission/reception with the slave device  22  for over a certain period of time, determines that the slave device  22  does not exist, and internally treat it as being disconnected or transmits deauthentication frame. 
         [0070]    3-2. An Example of a Second Operation 
         [0071]    Next, an example of the second operation to connect different groups will be explained with reference to  FIG. 7 . 
         [0072]      FIG. 7  is a sequence diagram showing an example of the second operation to connect different groups. In the example illustrated in  FIG. 7 , the master device  20 A and the slave device  22 A are connected, and the master device  20 C is currently using the frequency 2 while the master device  20 A and the slave device  22 A are currently using the frequency 1. Here, in order to connect the master device  20 A and the slave device  22 A to the master device  20 C, when a push button is pressed by a user in the master device  20 A and the master device  20 C (S 404 ), the master device  20 A starts an active frequency scanning operation to search a connection destination. 
         [0073]    This active frequency scanning operation enables the master device  20 A to receive the probe response from the master device  20 C at the frequency 2(S 412 ), and to detect the master device  20 C that is a wireless communication device to be connected to, and the frequency 2 that the master device  20 C is currently using. 
         [0074]    Afterward, the master device  20 A changes the frequency to use into the frequency 2 same as the master device  20 C, and performs the connection processing, such as authentication, association, WPS procedure, 4-way handshake or the like with respect to the master device  20 C (S 416 , S 420 , S 424 ). Note that since the master device  20 A changes the frequency to use temporarily, the master device  20 A and the slave devices  22  may hold the connection information (encryption information, information on a master-slave relationship, or the like) so that the connection relationship will be maintained. After the completion of security setting by the connection processing, the master device  20 A changes the frequency to use back to the frequency 1, and transmits the Extended Channel Switch Announcement message (S 428 ). 
         [0075]    Therefore, the slave device  22 A that receives this message can refer to NewChannelNumber and ChannelSwitchCount to change the frequency to use into the frequency 2 at the same timing as the master device  20 A (S 432 ). Thus, the frequency which the master device  20 A, the slave device  22 A and the master device  20 C use becomes the same. As the result, a mutual data communication among the master device  20 C, the master device  20 A and the slave device  22 A can be realized (S 436 ). 
         [0076]    3-3. An Example of a Third Operation 
         [0077]    Next, an example of the third operation to connect different groups will be explained with reference to  FIG. 8  and  FIG. 9 . 
         [0078]      FIG. 8  is a sequence diagram showing an example of the third operation to connect different groups. In an example illustrated in  FIG. 8 , the master device  20 A and the slave device  22 A are connected, and the master device  20 C is currently using the frequency 2 while the master device  20 A and the slave device  22 A are currently using the frequency 1. Here, in order to connect the master device  20 A and the slave device  22 A to the master device  20 C, when a push button is pressed by a user in the master device  20 A and the master device  20 C (S 504 ), the master device  20 A starts an active frequency scanning operation to search a connection destination. 
         [0079]    This active frequency scanning operation enables the master device  20 A to receive the probe response from the master device  20 C at the frequency 2 (S 512 ), and to detect the master device  20 C that is a wireless communication device to be connected to, and the frequency 2 that the master device  20 C is currently using. 
         [0080]    Afterward, the control unit  216  of the master device  20 A allows the communication unit to broadcast the beacon including Channel Switch Announcement IE (Information Element) that is DFS (Dynamic Frequency Selection) information defined in IEEE802.11-2007 for changing the frequency to be used by the group. Hereinafter, the DFS information will be explained with reference to  FIG. 9 . 
         [0081]      FIG. 9  is an explanatory diagram showing a configuration example of the DFS information. As shown in  FIG. 9 , the DFS information includes ElementID, Length, ChannelSwithMode, NewChannelNumber, and ChannelSwitchCount. 
         [0082]    In the DFS information, NewChannelNumber is information indicating a frequency after changed (i.e., a new frequency), and ChannelSwitchCount is information indicating when communication with the new frequency will begin (i.e., a timing of frequency change (for example, how many beacon transmission timings ahead it is)). In the example of operation shown in  FIG. 8 , information indicating the frequency 2 is described in NewChannelNumber. 
         [0083]    Note that the function of this DFS is normally used to change the frequency to use to other frequency when a wireless communication device using a specific frequency, which is assigned to the public use as well, detects that the specific frequency is used in the neighborhood. Therefore, there may be a case where the DFS function is not installed onto a wireless communication device that does not use the above specific frequency, however, a wireless communication device installed with the DFS function can utilize the DFS function for connection between groups as the present embodiment. 
         [0084]    The slave device  22 A that receives the beacon including the above DFS information can refer to NewChannelNumber and ChannelSwitchCount to change the frequency to use into the frequency 2 at the same timing as the master device  20 A (S 520 ). Note that  FIG. 8  omits the explanation on which other slave device  22 B currently connecting to the master device  20 A also performs the same operation as the slave device  22 A. That is, the slave device  22 B receives the beacon including the DFS information to acknowledge when and to which frequency to change, then changes the frequency to use into the frequency 2 at the same time with the master device  20 A and the slave device  22 B. 
         [0085]    Thus, the frequency which the master device  20 A, the slave device  22 A and the master device  20 C use becomes the same. This enables the master device  20 A to operate as a master device of the slave device  22 A, and as a slave device of the master device  20 C as well. 
         [0086]    Next, the master device  20 A performs a connection processing, defined in IEEE802.11 and WiFi Alliance, with respect to the master device  20 C. Specifically, the master device  20 A and the master device  20 C perform Authentication, Association, WPS procedure, 4-way handshake, or the like (S 524 , S 528 , S 532 ), and complete a security setting. As the result, a mutual data communication among the master device  20 C, the master device  20 A and the slave device  22 A can be realized (S 536 ). 
         [0087]    3-4. An Example of a Fourth Operation 
         [0088]    Finally, an example of the fourth operation to connect different groups will be explained with reference to  FIG. 10 . 
         [0089]      FIG. 10  is a sequence diagram showing an example of a fourth operation to connect different groups. In an example illustrated in  FIG. 10 , the master device  20 A and the slave device  22 A are connected, and the master device  20 C is currently using the frequency 2 while the master device  20 A and the slave device  22 A are currently using the frequency 1. Here, in order to connect the master device  20 A and the slave device  22 A to the master device  20 C, when a push button is pressed by a user in the master device  20 A and the master device  20 C (S 604 ), the master device  20 A starts an active frequency scanning operation to search a connection destination. 
         [0090]    This active frequency scanning operation enables the master device  20 A to receive the probe response from the master device  20 C at the frequency 2 (S 612 ), and to detect the master device  20 C that is a wireless communication device to be connected to, and the frequency 2 that the master device  20 C is currently using. 
         [0091]    Afterward, the master device  20 A changes the frequency to use into the frequency 2 same as the master device  20 C, and performs the connection processing, such as authentication, association, WPS procedure, 4-way handshake or the like with respect to the master device  20 C (S 616 , S 620 , S 624 ). Note that since the master device  20 A changes the frequency to use temporarily, the master device  20 A and the slave devices  22  may hold the connection information (encryption information, information on a master-slave relationship, or the like) so that the connection relationship will be maintained. After the completion of security setting by the connection processing, the master device  20 A changes the frequency to use back to the frequency 1, and transmits the Extended Channel Switch Announcement message (S 628 ). 
         [0092]    Therefore, the slave device  22 A that received this message can refer to NewChannelNumber and ChannelSwitchCount to change the frequency to use into the frequency 2 at the same timing as the master device  20 A. Note that  FIG. 4  omits the explanation on which other slave device  22 B currently connecting to the master device  20 A also performs the same operation as the slave device  22 A (S 632 ). Thus, the frequency which the master device  20 A, the slave device  22 A and the master device  20 C use becomes the same. As the result, a mutual data communication among the master device  20 C, the master device  20 A and the slave device  22 A can be realized (S 636 ). 
       4. CONCLUSION 
       [0093]    As described above, according to the present embodiment, the master device  20  notifies the slave device  22  that belong to the same group of a frequency used by other groups and a timing of frequency change, changes the frequency to use at the same time with the slave device  22 , and performs a connection processing with respect to other groups using the frequency after the change. Therefore, according to the present embodiment, the master device  20  can connect to wireless communication devices that belong to other groups while maintaining a connection relationship with the slave device  22  that belongs to the same group. 
         [0094]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
         [0095]    For example, the above example described a case where selection of a push button becomes a trigger for a connection operation between groups, however, the present invention is not limited to this example. As a modified example, a PIN input of WPS may trigger the start of the connection operation between groups. 
         [0096]    Further, each step in the processing of the wireless communication system in this specification is not necessarily performed in the order as described in the sequence diagrams chronologically. For example, each step in the wireless communication system may be processed in the order different from the one described in the flowchart herein, or may be processed in parallel. 
         [0097]    Furthermore, it may be created a computer program which enables the hardware such as a CPU, a ROM, a RAM or the like built in the master device  20  and the slave device  22  to perform the equivalent function same as each of the above-described configuration of the master device  20  and the slave device  22 . Moreover, a storage medium storing the computer program may be provided.