Patent Publication Number: US-2021195505-A1

Title: Communication apparatus and communication method

Description:
TECHNICAL FIELD 
     The present technology relates to a communication apparatus and a communication method. More particularly, the technology relates to a communication apparatus and a communication method for performing wireless communication with higher efficiency. 
     BACKGROUND ART 
     In recent years, there have been increasing use cases in which multiple wireless base stations (base stations) are set up indoors such as in the office or home in order to expand wireless LAN (Local Area Network) services. That means a wireless terminal that starts to offer wireless LAN services is required to select an optimal wireless base station from among the multiple wireless base stations being present. 
     Further, it is preferred that the wireless terminal presumably using wireless LAN services while on the move, such as a smartphone, a tablet terminal, or a laptop personal computer switches the connection likewise from one optimal wireless base station to another on site so as to maintain uninterrupted wireless communication. 
     There is a disclosed technology for establishing the time to be set for a scan through the use of learning information from the wireless terminal in the case where the active scan method is adopted when using wireless LAN services (e.g., see PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] 
     Japanese Patent Laid-open No. 2007-306510 
     SUMMARY 
     Technical Problem 
     However, the technology disclosed in PTL 1 requires learning wireless communication and cannot be used for initialization, which leaves the technology considered less than efficient. There has been a need for techniques for carrying out more efficient wireless communication. 
     The present technology has been devised under the above circumstances and is aimed at performing wireless communication with higher efficiency. 
     Solution to Problem 
     According to a first aspect of the present technology, there is provided a communication apparatus acting as a wireless base station including a control section configured to acquire, from another wireless base station, information related to configuration information regarding the other wireless base station. On the basis of the information related to the configuration information regarding the other wireless base station, the control section performs control to generate sharing verification information indicating whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station. The control section performs control to transmit the sharing verification information to the other wireless base station. 
     According to the first aspect of the present technology, there is provided a communication method for use with a communication apparatus of a wireless base station, the communication method including causing the communication apparatus to acquire, from another wireless base station, information related to configuration information regarding the other wireless base station; on the basis of the information related to the configuration information regarding the other wireless base station, causing the communication apparatus to generate sharing verification information indicating whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station; and causing the communication apparatus to transmit the sharing verification information to the other wireless base station. 
     With the communication apparatus and the communication method according to the first aspect of the present technology, information related to configuration information regarding another wireless base station is acquired from the other wireless base station. On the basis of the information related to the configuration information regarding the other wireless base station, sharing verification information is generated to indicate whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station. The sharing verification information is transmitted to the other wireless base station. 
     According to a second aspect of the present technology, there is provided a communication apparatus acting as a wireless terminal, the communication apparatus including a control section configured to perform control to transmit a request signal to a wireless base station, the request signal including multiplexing information related to multiplexing of a response signal responding to the request signal. 
     According to the second aspect of the present technology, there is provided a communication method for use with a communication apparatus of a wireless terminal, the communication method including causing the communication apparatus to perform control to transmit a request signal to a wireless base station, the request signal including multiplexing information related to multiplexing of a response signal responding to the request signal. 
     With the communication apparatus and the communication method according to the second aspect of the present technology, a request signal is transmitted to a wireless base station, the request signal including multiplexing information related to multiplexing of a response signal responding to the request signal. 
     The communication apparatus according to the first and the second aspects of the present technology may be an independent apparatus or may be an internal block or blocks constituting a single apparatus. 
     Advantageous Effect of Invention 
     According to the first and the second aspects of the present technology, wireless communication is performed more efficiently. 
     Note that the advantageous effects outlined above are not limitative of the present disclosure; further advantages will become apparent from a reading of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view depicting a configuration example of a wireless communication system. 
         FIG. 2  is a block diagram depicting a configuration example of an embodiment of a communication apparatus to which the present technology is applied. 
         FIG. 3  is a view outlining the active scan method. 
         FIG. 4  is a view depicting an example of multiplex communication of probe responses. 
         FIG. 5  is a view depicting an example of multiplex communication of probe responses performed by use of a narrow band. 
         FIG. 6  is a view depicting an example of the probe response multiplex communication to which the present technology is applied. 
         FIG. 7  is a view depicting an example of a common configuration information list. 
         FIG. 8  is a view depicting an example of overall sequence. 
         FIG. 9  is a flowchart explaining a flow of an AP scan phase. 
         FIG. 10  is a view depicting a state transition diagram of a common flag in the AP scan phase. 
         FIG. 11  is a view depicting a typical format of a multiplexing information frame. 
         FIG. 12  is a flowchart explaining a flow of a multiplexing information negotiation phase. 
         FIG. 13  is a state transition diagram of the common flag in the multiplexing information negotiation phase. 
         FIG. 14  is a view depicting a first example of sharing the common configuration information list. 
         FIG. 15  is a view depicting a second example of sharing the common configuration information list. 
         FIG. 16  is a view depicting a typical format of a probe trigger frame. 
         FIG. 17  is a view depicting a typical format of a probe response multiplexed frame. 
         FIG. 18  is a flowchart explaining a flow of a STA scan phase. 
         FIG. 19  is a flowchart explaining a flow of the process of generating a multiplexed probe response. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     A preferred embodiment of the present technology is described below with reference to the accompanying drawings. Note that the description will be given in the following order. 
     1. Embodiment of the present technology
 
2. Alternative example
 
     1. Embodiment of the Present Technology 
     Configuration Example of the Wireless Communication System 
       FIG. 1  is a view depicting a configuration example of a wireless communication system. 
     In  FIG. 1 , the wireless communication system is a wireless LAN (Local Area Network) system configured with multiple networks (BSS: Basic Service Set) each including wireless base stations (AP: Access Point) and a wireless terminal (STA: Station) connected therewith. 
       FIG. 1  depicts a case where three wireless base stations AP 1  to AP 3  are set up in a home along with one wireless terminal STA. The wireless base station AP 1  operates a network BSS 1 . Likewise, the wireless base stations AP 2  and AP 3  operate networks BSS 2  and BSS 3 , respectively. In this case, the wireless terminal STA may be connected to any one of the networks BSS 1  to BSS 3  operated by the wireless base stations AP 1  to AP 3 . 
     Incidentally, the configuration of the wireless communication system depicted in  FIG. 1  is an example and not limitative of how the system is to be configured. There need only be multiple connected communication apparatuses (wireless base stations AP) each having a communication apparatus (wireless terminal STA) as a terminal present in the vicinity. As along as these apparatuses meet the conditions depicted in  FIG. 1 , they may have any positional relations therebetween. 
     Configuration Example of the Communication Apparatus 
       FIG. 2  is a block diagram depicting a configuration example of an embodiment of a communication apparatus (wireless communication apparatus) to which the present technology is applied. 
     A communication apparatus  10  depicted in  FIG. 2  is configured as a wireless base station AP or as a wireless terminal STA in the wireless communication system of  FIG. 1 . 
     In  FIG. 2 , the communication apparatus  10  includes a control section  101 , a storage section  102 , a data processing section  103 , a transmission section  104 , a reception section  105 , and an antenna sharing section  106 . The communication apparatus  10  is also provided with an antenna  107  for the antenna sharing section  106 . 
     The control section  101  includes a processor such as a microprocessor that controls the operations of blocks constituting the communication apparatus  10 . The control section  101  further transfers information (data) between the blocks. 
     For example, the control section  101  controls the transmission section  104  to perform processes such as adjustment and determination of transmission parameters. In another example, the control section  101  controls the reception section  105  to carry out processes such as adjustment and determination of reception parameters. 
     The storage section  102  includes a semiconductor memory such as a nonvolatile memory or a volatile memory. Under control of the control section  101 , the storage section  102  stores diverse kinds of data. 
     For example, in the case where the communication apparatus  10  is a wireless base station AP, the storage section  102  may store necessary signal transmission status and signal reception status such as the reception power of beacons transmitted from other wireless base stations AP. The storage section  102  may further store a common configuration information list, to be discussed later. 
     Under control of the control section  101 , the data processing section  103  performs data processing on the data (signals) to be communicated. Specifically, at the time of transmission, for example, the data processing section  103  generates transmission data to be transmitted in packets, and supplies the generated data to the transmission section  104 . At the time of reception, for example, the data processing section  103  extracts reception data from a reception signal supplied from the reception section  105 . 
     Under control of the control section  101 , the transmission section  104  generates a transmission signal from the transmission data supplied from the data processing section  103 . The transmission section  104  supplies the generated transmission signal to the antenna sharing section  106 . 
     The transmission section  104  includes an analog signal conversion section  111  and an RF transmission section  112 . The analog signal conversion section  111  converts transmission data from digital to analog format and supplies the resulting analog signal to the RF transmission section  112 . The RF transmission section  112  generates a transmission signal by performing processes such as frequency conversion and power amplification on the analog signal supplied from the analog signal conversion section  111 . 
     Here, in the case where the communication apparatus  10  is a wireless base station AP, the transmission section  104  may generate the transmission signal using a frequency band (RU: Resource Unit) designated by the control section  101 . 
     At the time of transmission, the antenna sharing section  106  emits the transmission signal via the antenna  107  as an electromagnetic wave, the transmission signal being supplied from the transmission section  104  (from the RF transmission section  112  therein). At the time of reception, the antenna sharing section  106  supplies the reception section  105  with a reception signal received as an electromagnetic wave via the antenna  107 . 
     Under control of the control section  101 , the reception section  105  extracts reception data from the reception signal supplied from the antenna sharing section  106 . The reception section  105  supplies the extracted reception data to the data processing section  103 . 
     The reception section  105  includes an RF reception section  121  and a digital signal conversion section  122 . The RF reception section  121  converts the reception signal to a digital-ready analog signal by performing processes such as frequency conversion and power amplification on the reception signal, and supplies the resulting analog signal to the digital signal conversion section  122 . Note that an LNA (Low Noise Amplifier) included in the RF reception section  121  controls the gain of the reception intensity using AGC (Auto Gain Control). The digital signal conversion section  122  converts the analog signal supplied from the RF reception section  121  from analog to digital format, and supplies the resulting digital signal to the data processing section  103 . 
     The communication apparatus  10  configured as described above is provided as a wireless base station AP (or as a wireless terminal STA) in the wireless communication system in  FIG. 1 . In order to perform wireless communication with higher efficiency, the control section  101  may include features such as those explained below. That is, as will be discussed later in more detail, the control section  101  controls the operations of the configured blocks in such a manner as to carry out highly efficient active scans by transmitting a multiplexed probe response on the basis of a common configuration information list shared by the wireless base stations AP. 
     (Overview of the Present Technology) 
     Meanwhile, in utilizing wireless LAN services, the wireless terminal STA selects an optimal wireless base station from among multiple wireless base stations AP being present. While on the move, the wireless terminal STA switches the connection from one optimal wireless base station to another on site so as to maintain uninterrupted wireless communication. 
     In order to implement such operations, the wireless terminal STA is required to perform a fast scan over the networks BS in the vicinity. For example, the IEEE 802.11 standard for the PHY/MAC layers of wireless LANs stipulates two scan methods: a passive scan method and an active scan method. 
     The passive scan method involves obtaining information necessary for the connection from beacon signals (beacons) transmitted periodically from wireless base stations AP. The active scan method, on the other hand, involves having a request signal (probe request) transmitted from the wireless terminal STA to the wireless base stations AP so as to acquire diverse information in the form of response signals (probe responses) from the base stations AP. 
     According to the passive scan method, the wireless terminal STA is required to wait for a beacon to be transmitted from a wireless base station AP. In order to search for a connection destination at higher speed, it is desired to use the active scan method that causes the request signal to be transmitted from the wireless terminal STA. 
     However, according to the active scan method, it is necessary to wait for a certain period of time to receive signals from multiple wireless base stations AP. There is fear that information may not be collected efficiently from the wireless base stations AP depending on the wait time being set. Thus, there has been a need for making the active scan method more efficient. 
     For example, the above-mentioned PTL 1 discloses a method of setting the scan-related time through the use of learning information from the wireless terminal. The method disclosed in PTL 1 requires learning for a certain period of time at the same location. That means the method cannot be used for initialization, for example. The present technology aims to implement a highly efficient active scan method that can also be used for initialization without requiring learning from the wireless terminal. 
       FIG. 3  is a view outlining the active scan method. Note that, in  FIG. 3 , the left-to-right direction represents the direction of time. 
     By the active scan method, the wireless terminal STA first transmits a probe request to the wireless base stations AP in the vicinity. Upon receipt of the probe request, each of the wireless base stations AP transmits a probe response to the wireless terminal STA. At this time, each wireless base station AP counts down a randomly set time to start transmitting the probe response at the count “zero” so that the communication does not conflict (coincide) with that of the other wireless base stations AP. 
     If a wireless base station AP in a wait state finds that another wireless base station AP is transmitting a probe response, the wireless base station AP suspends its countdown until the transmission of the probe response by the other wireless base station AP comes to an end. Following the wait for the probe response transmission to come to an end, the wireless base station AP resumes the countdown. 
     More specifically, as depicted in  FIG. 3 , in the case where the wireless terminal STA transmits a probe request to each of the wireless base stations AP 1 , AP 2 , and AP 3 , the wireless base station AP 2  from among the three base stations transmits a probe response to the wireless terminal STA at time t 12  through time t 14 . During the transmission, the wireless base stations AP 1  and AP 3  are in a wait state, with the wireless base station AP 2  excluded. 
     Thereafter, at time t 15  through time t 17 , the wireless base station AP 1  out of the remaining two base stations AP 1  and AP 3  transmits a probe response to the wireless terminal STA, with the wireless base station AP 2  excluded. During the transmission, the wireless base station AP 3  is in a wait state. At time t 18  through time  20 , the remaining wireless base station AP 3  transmits a probe response to the wireless terminal STA, with the wireless base stations AP 1  and AP 2  excluded. 
     Note that, in  FIG. 3 , a reference sign DIFS (DCF Inter Frame Space) indicates that a given wireless base station waits for a certain period of time after another wireless base station AP has transmitted data. A reference sign SIFS (Short Inter Frame Space) indicates that in the case where the wireless terminal STA has correctly received the data destined therefor, the wireless terminal STA waits for a predetermined period of time before transmitting a response (Ack: Acknowledgement). 
     As described above, the larger the number of wireless base stations AP are in the vicinity of the wireless terminal STA, the longer it takes for the wireless terminal STA to process the scan. Furthermore, in the case where there is no knowing how many wireless base stations AP are in the vicinity, the wireless terminal STA is required to set a prolonged time period in which a probe response (probe response wait time) is waited for. That means more time is needed for the scan. 
     In view of the above, there is envisaged a method that involves frequency-multiplexing probe responses from multiple wireless base stations AP and transmitting the frequency-multiplexed probe responses in order to shorten the processing time of the active scan method.  FIG. 4  depicts an example of multiplex communication of probe responses. 
     In  FIG. 4 , upon transmitting a probe request to the wireless base stations AP in the vicinity, the wireless terminal STA adds a frame to the request for notification purpose, the frame including information regarding signal multiplexing (trigger information). Upon receipt of the probe request, the wireless base station AP may select a frequency band, based on the information included in the received trigger information with regard to signal multiplexing, before transmitting a probe response in the selected frequency band. 
     More specifically, as depicted in  FIG. 4 , the wireless terminal STA transmits the probe request including the trigger information to each of the wireless base stations AP 1 , AP 2 , and AP 3 . In this case, upon receipt of the probe request, the wireless base stations AP 1 , AP 2 , and AP 3  frequency-multiplex their probe responses on the basis of the trigger information and transmit the frequency-multiplexed probe responses simultaneously to the wireless terminal STA. This allows the wireless terminal STA to receive simultaneously the probe responses from the wireless base stations AP 1 , AP 2 , and AP 3 . Consequently, the wireless terminal can shorten the probe response wait time and thereby reduce the active scan time. 
     This method related to frequency multiplexing is based on the technology adopted by IEEE 802.11ax currently being standardized. IEEE 802.11ax grants only one wireless base station AP means to let multiple wireless terminals STA perform frequency multiplexing. The literature cited below discloses technology for allowing wireless base stations AP to exchange multiplexing information therebetween. 
     Literature: Japanese Patent Laid-open No. 2017-22459 
     However, in the case where there is no knowing how many wireless base stations AP are in the vicinity of the wireless terminal STA, the band for use in probe responses cannot be designated by the wireless terminal STA. The band needs to be designated by the wireless base stations AP. In this case, the wireless terminal STA narrows the band for probe response (signal) transmission as much as possible in order to reduce the probability of conflicting with the bands used by the wireless base stations AP in the vicinity. 
       FIG. 5  depicts an example of multiplex communication of probe responses performed by use of a narrow band. Note that, in  FIG. 5 , the left-to-right direction represents the direction of time, and the bottom-up direction denotes the magnitude of frequency. 
     Here, if the band is excessively narrowed for probe response transmission as depicted in  FIG. 5 , it takes more time to transmit a single probe response. There is fear that the processing time for active scans may not be effectively reduced as expected. 
     That is, what is transmitted in  FIG. 5  includes a preamble signal common to all wireless base stations AP and probe responses from the wireless base stations AP 1 , AP 2 , and AP 3 . Since the probe response from each wireless base station AP is transmitted in a narrow band, it is expected that the processing time for active scans is not effectively reduced. 
     For cases in which the wireless terminal STA causes multiple wireless base stations AP to perform frequency division multiplex communication, the present technology proposes the method of implementing highly efficient active scans by determining a transmission band for use in frequency multiplexing on the basis of a previously generated (prepared) list (common configuration information list, to be discussed later). 
       FIG. 6  depicts an example of the probe response multiplex communication to which the present technology is applied. The probe response multiplex communication to which this technology is applied involves transmitting probe responses using a wide band in the case of concurrently sending information common to the wireless base stations AP in the vicinity (the information will be referred to as the common information hereunder). In this case, the wireless terminal STA receives probe responses (signals) in a manner overlapping with one another from multiple wireless base stations. If the information transmitted from each of the wireless base stations AP is all identical, the signals can be decoded without interference with each other. 
     Meanwhile, the probe response multiplex communication to which the present technology is applied uses a narrow band in a case where each wireless base station transmits information different from that of the other wireless base stations in the vicinity (the non-common information will be referred to as the unique information hereunder). In this case, the wireless terminal STA can separately receive and decode the probe responses (signals) because they are transmitted from the wireless base stations AP in different frequency bands. 
     In  FIG. 6 , as described above, the common information and the other information (unique information) are separately handled in the multiplex communication of probe responses by use of a wide band and a narrow band. Compared with the existing method ( FIG. 5 ) of having all information transmitted in a narrow band, the transmission time is shortened, and the time required to do active scans is reduced correspondingly. 
     Note that the wide band (broadband) as a first band means it is wider than the narrow band (narrow band) as a second band. As long as the first band (e.g., 20 to 40 MHz) is wider than the second band (e.g., 2 MHz) upon comparison in terms of relations therebetween (the second band is narrower than the first band), the first and the second bands may each be assigned a desired band. In the first band, the same band is assigned to all wireless base stations AP, and in the second band, a different band is assigned (randomly) to each wireless base station AP. 
     Example of the Common Configuration Information List 
     Here, the determination of whether or not given information has a commonality with the wireless base stations AP is performed by each wireless base station AP on the basis of a list (hereinafter, called the common configuration information list) prepared collectively beforehand by the wireless base stations AP in the vicinity.  FIG. 7  depicts an example of the common configuration information list. The common configuration information list may also be said to be common configuration information determination information used by a given wireless base station AP to determine whether or not given configuration information has a commonality with the other wireless base stations AP. 
     In  FIG. 7 , the information that may be transmitted by use of a probe response is referred to as the configuration information. That is, the common configuration information list includes four patterns of information, “Yes,” “No,” “Unknown,” and “Initial,” with respect to various kinds of configuration information. The four patterns of information are distinguished from one another by a two-bit common flag. 
     For example, of the sets of configuration information requested by a probe request, the configuration information with its common flag set to “Yes” has a commonality with the wireless base stations in the vicinity and thus can be transmitted by use of the wide band. The configuration information with its common flag set to other than “Yes” is different from the wireless base stations AP in the vicinity and thus can be transmitted by use of the narrow band. That is, the common flag may also be said to be information regarding the configuration information in the common configuration information list for the wireless base stations AP. 
     Alternatively, the common configuration information list may be generated in predetermined units, e.g., in units of an SSID (Service Set Identifier) or in units of an established group.  FIG. 7  indicates that the common configuration information list is generated for the same SSID and for each of other settings (for specific groups). 
     For example, configuration information “Timestamp” is set with “No” and “No” as common flags (for the same SSID and for the others, in that order); “Beacon interval” is set with “Yes” and “No”; and “Capability Information” is set with “Yes” and “Yes.” Further, configuration information “SSID” is set with “Yes” and “No”; “Supported Rates and BSS Membership Selectors” is set with “Yes” and “No”; and “DSSS Parameter SET” is set with “Unknown” and “Unknown,” for example. 
     Here, in a case where wireless base station products are used in the office, for example, the information such as “Capability Information” is presumed to be approximately the same for all the products as common information. In a case where different products of wireless base stations are introduced in the home, for example, there presumably exist multiple sets of common information, such as support for IEEE 802.11n, support for IEEE 802.11ac, and usable frequency bands. 
     On the other hand, the information unique to each wireless base station AP such as a MAC (Media Access Control address) address and Timestamp needs to be communicated individually. Such information is handled not as the common information but as the unique information. 
     Example of Overall Sequence 
       FIG. 8  is a view depicting an example of overall sequence according to the present technology. 
     In  FIG. 8 , if the flow of processes to which the present technology is applied is depicted in an overall sequence, the process flow may be divided into three phases: an AP scan phase (S 1 ), a multiplexing information negotiation phase (S 2 ), and an STA scan phase (S 3 ). 
     The AP scan phase (S 1 ) is a phase in which each wireless base station AP updates (or generates) the common configuration information list it retains, on the basis of beacons (notification signals) from the other wireless base stations AP. 
     In the AP scan phase (S 1 ), each wireless base station AP (e.g., wireless base station AP 1 ) receives beacons sent from the other wireless base stations AP (e.g., wireless base stations AP 2  and AP 3 ) (S 11 , S 12 , and S 13 ). Each wireless base station AP updates (or generates) the common configuration information list it retains on the basis of the configuration information included in the received beacons. 
     Note that the AP scan phase will be discussed later in more detail with reference to  FIGS. 9 and 10 . 
     The multiplexing information negotiation phase (S 2 ) is a phase in which it is ascertained whether or not the wireless base stations AP share the common configuration information list generated in the AP scan phase and whether or not the same common configuration information list is retained by the wireless base stations AP. 
     In the multiplexing information negotiation phase, the wireless base station AP 1 , for example, generates a multiplexing information frame, and transmits the generated frame to the wireless base stations AP 2  and AP 3  (S 21 ). As will be discussed later in more detail, the multiplexing information frame includes information regarding the configuration information in the common configuration information list retained by the own station (base station AP). 
     The wireless base stations AP 2  and AP 3  receive the multiplexing information frame from the wireless base station AP 1 . In the case where the wireless base stations AP 2  and AP 3  retain the same common configuration information list as that of the wireless base station AP 1 , the wireless base stations AP 2  and AP 3  transmit responses (Ack) to that effect to the wireless base station AP 1  (S 22  and S 23 ). 
     Here, in the example of  FIG. 8 , the wireless base stations AP 2  and AP 3  retain the same common configuration information list as that of the wireless base station AP 1  and thus transmit Ack to the latter. In the case where the wireless base stations AP 2  and AP 3  retain a common configuration information list different from that of the wireless base station AP 1 , the wireless base stations AP 2  and AP 3  each generate a multiplexing information frame that includes information regarding the configuration information in their common configuration information list. The wireless base stations AP 2  and AP 3  transmit the generated multiplexing information frames to the wireless base station AP 1 . 
     It is assumed that the multiplexing information negotiation phase is performed at predetermined time intervals. Apart from such timing, the multiplexing information negotiation phase may be triggered to be performed when any one of the wireless base stations AP has changed its configuration information or when a new adjacent wireless base station AP is detected, for example. 
     Note that the multiplexing information negotiation phase will be discussed later in more detail with reference to  FIGS. 11 to 15 . 
     The STA scan phase (S 3 ) is a phase in which, in a case where the wireless terminal STA transmits a probe request using the active scan method, the wireless base stations AP transmit probe responses in reply to the request. 
     It is to be noted here that the wireless terminal STA transmits a trigger-carrying probe request and that the wireless base stations AP transmit multiplexed probe responses in reply to the request. Here, it may be said that the probe request (trigger-carrying probe request) is a request signal and that the probe responses (multiplexed probe response) are a response signal in reply to the request signal. 
     As will be discussed later in detail, the trigger-carrying probe request includes, besides the probe request, trigger information including such information as the frequency band and transmission power at the time of multiplexed probe responses. In the multiplexed probe responses, the common information regarding the wireless base stations AP is transmitted in a wide band frame and the unique information specific to each wireless base station AP is transmitted in a narrow band frame. 
     In the STA scan phase, upon turning on power, for example (S 41 ), the wireless terminal STA transmits the trigger-carrying probe request to each of the wireless base stations AP 1  to AP 3  (S 31 ). On the basis of the trigger-carrying probe request from the wireless terminal STA, the wireless base stations AP 1  to AP 3  transmit multiplexed probe responses to the wireless terminal STA (S 32 ). 
     The wireless terminal STA receives the multiplexed probe responses from the wireless base stations AP 1  to AP 3 , and transmits a response (Multi-STA Ack) to each of the wireless base stations AP 1  to AP 3  in reply (S 33 ). 
     Note that the STA scan phase will be discussed later in more detail with reference to  FIGS. 16 to 19 . 
     According to the present technology, as described above, the operation of wireless LAN services based on the active scan method is implemented using the three phases, i.e., an AP scan phase, a multiplexing information negotiation phase, and an STA scan phase. These phases will be discussed individually below in detail. 
     (Details of the AP Scan Phase) 
     First, with reference to  FIGS. 9 and 10 , the AP scan phase depicted in  FIG. 8  is explained in detail. 
       FIG. 9  is a flowchart explaining a flow of the AP scan phase performed by the communication apparatus  10  serving as a wireless base station AP. 
     In step S 101 , the reception section  105  receives a beacon transmitted from another wireless base station AP. 
     In step S 102 , on the basis of the configuration information included in the received beacons, the control section  101  extracts various kinds of configuration information from inside the common configuration information list stored in the storage section  102 . 
     In step S 103 , on the basis of the extracted configuration information, the control section  101  updates the common flag in the common configuration information list stored in the storage section  102 . 
     Here, in the case where the relations between the configuration information (e.g., Timestamp and Beacon interval) included in the beacon received from the other wireless base station AP on one hand and various kinds of configuration information (e.g., Timestamp and Beacon interval) in the common configuration information list on the other hand meet predetermined conditions, the state of the common flag (e.g., “Yes,” “No,” and “Unknown”) regarding the configuration information in the common configuration information list is updated. 
     Upon completion of the processing of step S 103 , the AP scan phase depicted in  FIG. 9  is terminated. 
       FIG. 10  depicts a state transition diagram of the common flag in the AP scan phase. 
     In the AP scan phase, as described above, the two-bit common flag can represent four states, i.e., “Initial,” “Yes,” “No,” and “Unknown.” 
     First, in the case where the state of the common flag is “Initial,” when there is configuration information in the beacon from another wireless base station AP, and when the configuration information is the same as the own configuration information, the state of the common flag transitions from “Initial” to “Yes” (T 11  indicated by an arrow originating from a circle “Initial” in the drawing). When there is configuration information in the beacon and when the configuration information differs from the own configuration information, the state of the common flag transitions from “Initial” to “No” (T 12  indicated by an arrow originating from the circle “Initial” in the drawing). 
     Note that, in the case where the state of the common flag is “Initial” and where there is no configuration information in the beacon from another wireless base station AP, the state of the common flag transitions from “Initial” to “Unknown” (T 13  indicated by an arrow originating from the circle “Initial” in the drawing). 
     Second, in the case where the state of the common flag is “Yes,” where there is configuration information in the beacon from another wireless base station AP, and where the configuration information is the same as the own configuration information, the state of the common flag remains “Yes” (T 11  indicated by an arrow originating from a circle “Yes” in the drawing). When there is configuration information in the beacon and when the configuration information differs from the own configuration information, the state of the common flag transitions from “Yes” to “No” (T 12  indicated by an arrow originating from the circle “Yes” in the drawing). 
     Note that, even in the case where the state of the common flag is “Yes,” if there is no configuration information in the beacon from another wireless base station AP, the state of the common flag transitions from “Yes” to “Unknown” (T 13  indicated by an arrow originating from the circle “Yes” in the drawing). 
     Third, in the case where the state of the common flag is “No,” where there is configuration information in the beacon from another wireless base station AP, and either where the configuration information is the same as or different from the own configuration information or where there is no configuration information in the beacon from another wireless base station AP, the state of the common flag remains “No” (T 11 , T 12 , or T 13  indicated by an arrow originating from a circle “No” in the drawing). 
     Fourth, in the case where the state of the common flag is “Unknown,” where there is configuration information in the beacon from another wireless base station AP, and either where the configuration information is the same as the own configuration information or where there is no configuration information in the beacon, the state of the common flag remains “Unknown” (T 11  or T 13  indicated by an arrow originating from a circle “Unknown” in the drawing). When there is configuration information in the beacon and when the configuration information differs from the own configuration information, the state of the common flag transitions from “Unknown” to “No” (T 12  indicated by an arrow originating from the circle “Unknown” in the drawing). 
     Here, in a case where it is assumed that a given wireless base station AP receives the beacons from multiple wireless base stations AP and where at least one of the sets of configuration information coming from these wireless base stations AP and included in the received beacons is detected to be different from the own configuration information, the state of the common flag is caused to transition to “No.” Also, in the case where at least one of the beacons received from the multiple wireless base stations AP does not include configuration information, the state of the common flag is caused to transition to “No” or to “Unknown.” 
     That is, only in the case where the beacons from all wireless base stations AP include configuration information and where the sets of configuration information from all wireless base stations AP are the same as the own configuration information, is the state of the common flag caused to transition to “Yes.” 
     In the AP scan phase, as described above, each wireless base station AP updates the common flag in the common configuration information list it retains on the basis of the configuration information included in the beacons from the other wireless base stations AP. In this manner, the same common configuration information list is retained by the wireless base stations AP. 
     (Details of the Multiplexing Information Negotiation Phase) 
     Next, the multiplexing information negotiation phase in  FIG. 8  is explained below in detail with reference to  FIGS. 11 to 15 . 
       FIG. 11  depicts a typical format of the multiplexing information frame. 
     Here in  FIG. 11 , the multiplexing information frame is based on the frame format called the element stipulated by the IEEE 802.11 standard. However, this is not limitative of the format of the multiplexing information frame. Incidentally, the frame format depicted in  FIG. 11  includes a multiplexing information element (AP multiplexing information element) and is thus called the multiplexing information frame here. 
     In  FIG. 11 , the multiplexing information frame includes Element ID, Length, Element ID Extension, and Common Flag Info fields. 
     The Element ID stores identification information indicating that this element is the multiplexing information element. The Length stores information regarding the length of the frame. The Element ID Extension stores extension information regarding the element. 
     The Common Flag Info stores common flag information including the state of the common flag for each configuration information. Here, the common flag information indicates whether or not the configuration information regarding the own wireless base station AP has a commonality with another wireless base station AP. The common flag information is used as sharing verification information for ascertaining whether or not the same common configuration information list is retained, and thus shared, by the wireless base stations AP. 
     The common flag information represents the state of the common flag for each configuration information (e.g., “Yes,” “No,” and “Unknown”) using two bits assigned to each configuration information. Here in the common flag information, the state of the common flag for each configuration information is determined by information regarding the configuration information from the other wireless base station AP, i.e., by the common flag information included in the configuration information or in the multiplexing information frame in the beacon from the other wireless base station AP. 
     Also, the Order number stipulated by the IEEE 802.11 standard, for example, may be used here to define the order of the configuration information arranged in the Common Flag Info. Specifically, as depicted in the above-described  FIG. 7 , Order number 1 stands for Timestamp, Order number 2 for Beacon interval, and Order number 3 for Capability Information. Likewise, Order numbers 4, 5, 6, . . . denote SSID, Supported Rates and BSS Membership Selectors, DSSS Parameter Set, . . . , respectively. 
     In this manner, the Common Flag Info has Order 1 Common Flag, Order 2 Common Flag, Order 3 Common Flag, . . . as two-bit Common Flags, arranged in sequence. For example, Order 1 Common Flag denotes the state of the common flag of Timestamp, Order 2 Common Flag represents the state of the common flag of Beacon interval, and Order 3 Common Flag stands for the state of the common flag of Capability Information. 
     Note that, in the description that follows, the common flag (Order Common Flag) included in the common flag information (Common Flag Info) may be referred to as the order common flag so as to be distinguished from the common flag included in the above-described common flag information list. 
     In the multiplexing information negotiation phase, the multiplexing information frame structured as described above is exchanged between the wireless base stations AP. 
       FIG. 12  is a flowchart explaining a flow of the multiplexing information negotiation phase performed by the communication apparatus  10  serving as the wireless base station AP. 
     In step S 201 , the reception section  105  receives a multiplexing information frame sent from another wireless base station AP. This allows the control section  101  to acquire the common flag information (Common Flag Info) included in the multiplexing information frame. 
     In step S 202 , the control section  101  determines whether or not the information (state of the Order Common Flag) in the acquired common flag information (Common Flag Info) matches with the information (state of the Order Common Flag) in the own common configuration information list retained by the own wireless base station AP. 
     In the case where it is determined in step S 202  that the two sets of information match with each other, control is transferred to step S 203 . In step S 203 , the transmission section  104  waits for a randomly determined period of time so that an upcoming notification will not conflict with that of any other wireless base station AP, before transmitting Ack to the other wireless base station that is the transmission source. 
     That is, in this case, the same common configuration information list is retained by the wireless base stations AP in the AP scan phase, so that there is no need to update the common configuration information list. 
     On the other hand, in the case where it is determined in step S 202  that the two sets of information fail to match with each other, control is transferred to step S 204 . In step S 204 , given the sets of configuration information in the common flag information list, the control section  101  extracts each configuration information whose state of the common flag fails to match with the state of the order common flag in the common flag information. 
     In step S 205 , the control section  101  updates the common flag for each extracted configuration information out of the sets of configuration information in the common configuration information list. 
     In the case here in which, for example, the states (e.g., “Yes,” “No,” and “Unknown”) of the order common flags in the common flag information included in the multiplexing information frame received from the other wireless base station AP fail to match with the states (e.g., “Yes,” “No,” and “Unknown”) of the common flags in various kinds of configuration information (e.g., Timestamp and Beacon interval) in the common configuration information list retained by the own wireless base station AP (for example, even in the case of a single mismatch), the unmatched states of the common flags (e.g., “Yes,” “No,” and “Unknown”) are updated in the common configuration information list. 
     In step S 206 , the transmission section  104  waits for a randomly determined period of time so that an upcoming notification will not conflict with that of any other wireless base station AP, before transmitting a multiplexing information frame to the other wireless base station that is the transmission source. Here, the multiplexing information frame including the common flag information reflecting the content of the updated common configuration information list is generated and transmitted. 
     In other words, the communication apparatus  10  acting as the (own) wireless base station AP acquires information regarding the configuration information (the configuration information included in the beacon, or the common flag information included in the multiplexing information frame) from another wireless base station AP. On the basis of the acquired information, the communication apparatus  10  generates the multiplexing information frame including the common flag information as the sharing verification information indicating whether or not the configuration information regarding the own wireless base station AP has a commonality with the other wireless base station AP. The multiplexing information frame thus generated is transmitted to the other wireless base station AP. 
     That is, in this case, it is possible to detect and correct differences between the different common configuration information lists generated by the wireless base stations AP at the time of the AP scan phase. 
     Upon completion of the processing of step S 203  or step S 206 , the process of the multiplexing information negotiation phase indicated in  FIG. 12  is terminated. 
       FIG. 13  is a state transition diagram of the common flag in the multiplexing information negotiation phase. 
     In the multiplexing information negotiation phase, it is assumed that the two-bit common flag represents three states, i.e., “Yes,” “No,” and “Unknown.” That is, compared with the AP scan phase, the common flag in the multiplexing information negotiation phase excludes the state of “Initial,” i.e., the initial state. 
     First, in the case where the state of the common flag in the common configuration information list is “Yes” and where the state of the order common flag in the common flag information (Common Flag Info) included in the multiplexing information frame from another wireless base station AP is “Yes,” the state of the common flag in the common configuration information list remains “Yes” (T 21  indicated by an arrow originating from a circle “Yes” in the drawing). 
     In the case where the state of the common flag in the common configuration information list is “Yes” and where the state of the order common flag in the common flag information is “No,” the state of the common flag in the common configuration information list transitions from “Yes” to “No” (T 22  indicated by an arrow originating from the circle “Yes” in the drawing). Further, in the case where the state of the common flag in the common configuration information list is “Yes” and where the state of the order common flag in the common flag information is “Unknown,” the state of the common flag in the common configuration information list transitions from “Yes” to “Unknown” (T 23  indicated by an arrow originating from the circle “Yes” in the drawing). 
     Second, in the case where the state of the common flag in the common configuration information list is “No” and where the state of the order common flag in the common flag information is “Yes,” “No,” or “Unknown,” the state of the common flag in the common configuration information list remains “No” (T 21 , T 22 , or T 23  indicated by an arrow originating from a circle “No” in the drawing). 
     Third, in the case where the state of the common flag in the common configuration information list is “Unknown” and where the state of the order common flag in the common flag information is “Yes,” the state of the common flag in the common configuration information list transitions from “Unknown” to “Yes” (T 21  indicated by an arrow originating from a circle “Unknown” in the drawing). 
     Also, in the case where the state of the common flag in the common configuration information list is “Unknown” and where the state of the order common flag in the common flag information is “No,” the state of the common flag in the common configuration information list transitions from “Unknown” to “No” (T 22  indicated by an arrow originating from the circle “Unknown” in the drawing). Further, in the case where the state of the common flag in the common configuration information list is “Unknown” and where the state of the order common flag in the common flag information is “Unknown,” the state of the common flag in the common configuration information list remains “Unknown” (T 23  indicated by an arrow originating from the circle “Unknown” in the drawing). 
     As described above, even in the case where the state of the common flag in the common configuration information list is “Unknown” in the AP scan phase, for example, if the state of the order common flag in the common flag information is “Yes” or “No” in the multiplexing information negotiation phase, the state of the common flag in the common configuration information list can be caused to transition from “Unknown” to “Yes” or to “No” for correction. 
       FIG. 14  is a view depicting a first example of sharing the common configuration information list. 
       FIG. 14  depicts an example in which the wireless base stations AP 1 , AP 2 , and AP 3  share the common configuration information list. It is assumed here that configuration information A and configuration information B has a commonality with the wireless base stations AP 1  and AP 2 , that configuration information A and configuration information C has a commonality with the wireless base stations AP 2  and AP 3 , and that configuration information A and configuration information C has a commonality with the wireless base stations AP 1  and AP 3 . 
     First, the wireless base station AP 1  retains a common configuration information list L- 1  in which the state of the common flag is “Initial” for the configuration information A, B, and C. 
     At this time, the wireless base station AP 2  transmits a beacon. Upon receipt of the beacon, the wireless base station AP 1  updates the state of the common flag for the configuration information A, B, and C to “Yes,” “Yes,” and “No,” respectively, in a common configuration information list L- 2  because the configuration information A and configuration information B has a commonality with the wireless base stations AP 1  and AP 2 . 
     Thereafter, the wireless base station AP 3  transmits a beacon. Upon receipt of the beacon, the wireless base station AP 1  updates the state of the common flag for the configuration information B from “Yes” to “No” in a common configuration information list L- 3  because the configuration information A and configuration information C has a commonality with the wireless base stations AP 1  and AP 3 . 
     As described above, with the beacons exchanged between the wireless base stations AP in the AP scan phase, each wireless base station updates the common configuration information list it retains. Thus, the same common configuration information list is retained by the wireless base stations AP. 
       FIG. 15  is a view depicting a second example of sharing the common configuration information list. 
     It is assumed in the sharing example of  FIG. 15  that, unlike in the above-described sharing example of  FIG. 14 , the wireless base station AP 1  has failed to receive a beacon sent from the wireless base station AP 3  in the AP scan phase. 
     In this case, upon receipt of the beacon from the wireless base station AP 2  in the AP scan phase, the wireless base station AP 1  updates the common flag for the configuration information A, B, and C from the initial state to “Yes,” “Yes” and “No,” respectively, in the common configuration information list L- 2 . 
     Thereafter, in the multiplexing information negotiation phase, the wireless base station AP 2  transmits a multiplexing information frame. At this time, the wireless base station AP 1  receives the multiplexing information frame from the wireless base station AP 2  and, based on the order common flag in the common flag information obtained from the frame, updates the state of the common flag for the configuration information B from “Yes” to “No” as the common configuration information list L- 3 ′. 
     As described above, even in the case where the wireless base station AP 1  fails to receive the beacon from the wireless base station AP 3  in the AP scan phase, the wireless base station AP 2  has received the beacon from the wireless base station AP 3 . Thus, in the multiplexing information negotiation phase, the wireless base station AP 1  can correct the common configuration information list by receiving the multiplexing information frame from the wireless base station AP 2 . This allows the same common configuration information list to be retained by the wireless base stations AP 1 , AP 2 , and AP 3 . 
     As described above, in the case where the same common configuration information list is not retained by the wireless base stations AP in the AP scan phase, the common configuration information list is corrected by use of the multiplexing information frame in the multiplexing information negotiation phase. This enables the wireless base stations AP to retain the same common configuration information list. 
     (Details of the STA Scan Phase) 
     Next, the STA scan phase in  FIG. 8  is explained below in detail with reference to  FIGS. 16 to 19 . 
     In the case where the active scan method is adopted for using wireless LAN services, the wireless terminal STA transmits a probe request to the wireless base stations AP. According to the present technology, the probe request together with trigger information (trigger-carrying probe request) is transmitted. 
       FIG. 16  depicts a typical format of a frame that holds the trigger-carrying probe request (probe trigger frame). 
     In  FIG. 16 , the probe trigger frame includes MAC Header, Frame Body, Trigger Field, and FCS. The MAC Header is the header of the MAC layer. The Frame Body stores the probe request. The FCS (Frame Check Sequence) stores information regarding error detection and correction. 
     The probe trigger frame includes trigger information stored in the Trigger Field in addition to the probe request stored in the Frame Body. The Trigger Field includes Common Info and Per SSID Info as the trigger information. The Common Info stores the time until response and STA information, among others. 
     The Per SSID Info refers to information for each SSID to which a multiplexed probe response is to be transmitted, and includes SSID, Bandwidth Information, MCS, and Target RSSI, for example. These sets of information represent information related to multiplexing of probe responses (multiplexing information). The information can indicate whether or not multiplexing is available by means of the presence or absence of the information for each SSID. 
     The SSID stores information for identifying the wireless base station AP. The Bandwidth Information stores bandwidth information regarding the frequency band in which multiplexed probe responses are to be transmitted. The MCS (Modulation and Coding Scheme) stores information that indexes spatial streams by a modulation method or by an encoding rate. The Target RSSI (Received Signal Strength Indication) stores information regarding a received signal strength. 
     In the STA scan phase, the probe trigger frame structured as described above is transmitted from the wireless terminal STA to the wireless base stations AP in the vicinity. Upon receipt of the trigger-carrying probe request, each of the wireless base stations AP transmits a probe response to the wireless terminal STA. According to the present technology, what is transmitted here is a probe response in which the probe responses transmitted in the wide band and in the narrow band are multiplexed (i.e., multiplexed probe response). 
       FIG. 17  depicts a typical format of a frame that holds a multiplexed probe response (i.e., probe response multiplexed frame). 
     In  FIG. 17 , the probe response multiplexed frame includes a wide band frame and a narrow band frame. Here, the frame having a preamble signal and a probe response including shared information is referred to as the wide band frame, and the frame having a probe response including unique information (information other than the shared information) is referred to as the narrow band frame. Note that the relations between the wide band as the first band and the narrow band as the second band have already been discussed earlier. 
     In the wide band frame, the preamble signal includes a Wide Band Frame Duration field. The Wide Band Frame Duration stores wide band frame duration information. The wide band frame duration information relates to the length of the wide band frame, designating the time in which transmission is performed by use of the wide band frame. 
     That is, upon receipt of the probe response multiplexed frame, the wireless terminal STA can recognize (detect) where transmission of the narrow band frame starts (i.e., boundary (break) between the wide band frame and the narrow band frame) on the basis of the wide band frame duration information included in the preamble signal. 
     Also in the wide band frame, the probe response includes MAC Header  1  and Frame Body fields. The MAC Header  1  is the header of the MAC layer and includes Frame Control, Duration, and Receiver Address fields, for example. 
     The Frame Control stores information regarding the type and destination of the probe response multiplexed frame. The Duration stores information regarding the length of the probe response multiplexed frame (time for transmission). That is, upon receipt of the probe response multiplexed frame, the wireless terminal STA can recognize the total length of the probe response multiplexed frame (i.e., end of (the narrow band frame of) the probe response multiplexed frame) on the basis of the duration information in the MAC Header  1 . The Receiver Address stores information regarding the address of the transmission destination (wireless terminal STA) of the probe response multiplexed frame. 
     Incidentally, the Frame Control, Duration, and Receiver Address constitute an example of the MAC Header  1 . Alternatively, the MAC Header  1  may include header information common to the other wireless base stations AP (e.g., wireless base stations AP 2  and AP 3 ) in the vicinity of the own wireless base station AP (e.g., wireless base station AP 1 ). 
     In the wide band frame, the Frame Body (Probe Common Info.) in the probe response stores shared information as the information (probe response) transmitted by use of the wide band frame. For example, the shared information as part of the configuration information has a commonality with the other wireless base stations AP (e.g., wireless base stations AP 2  and AP 3 ) in the vicinity of the own wireless base station AP (e.g., wireless base station AP 1 ). 
     In the narrow band frame, the probe response includes MAC Header  2  and Frame Body fields, for example. The MAC Header  2  is the header of the MAC layer and includes a Transmitter Address field. The Transmitter Address stores information regarding the address of the transmission source of this frame. 
     Note that the Transmitter Address is an example of the MAC Header  2 . The Transmitter Address may include header information that is different from (not common to) that of the other wireless base stations AP (e.g., wireless base stations AP 2  and AP 3 ) in the vicinity of the own wireless base station AP (e.g., wireless base station AP 1 ). 
     In the narrow band frame, the Frame Body (Not Probe Common Info.) in the probe response stores unique information as the information transmitted by use of the narrow band frame (probe response). For example, the unique information as part of the configuration information is different from (not common to) the other wireless base stations AP (e.g., wireless base stations AP 2  and AP 3 ) in the vicinity of the own wireless base station AP (e.g., wireless base station AP 1 ). 
     Note that, with respect to the frame structure in  FIG. 17 , it has been explained above that where the transmission of the narrow band frame starts is recognized on the basis of the wide band frame duration information included in the preamble signal. Here, it is sufficient if the break between the wide band frame and the narrow band frame can be recognized. For example, a Length (bit count) field may be used in place of the Duration (time). 
       FIG. 18  is a flowchart explaining a process flow of the STA scan phase performed by the communication apparatus  10  serving as the wireless base station AP. 
     In step S 301 , the reception section  105  receives a probe request transmitted from the wireless terminal STA. 
     In step S 302 , the control section  101  analyzes the received probe request and determines whether the probe request is broadcast or destined to the own wireless base station. 
     In the case where it is determined in step S 302  that the probe request is broadcast or destined to the own wireless base station, control is transferred to step S 303 . In step S 303 , the control section  101  determines whether or not the received probe request is a probe trigger frame. 
     In the case where it is determined in step S 303  that the frame is not the probe trigger frame, the received probe request is handled as the current probe request. Control is then transferred to step S 304 . 
     In step S 304 , the control section  101  generates a probe response in reply to the received current probe request. 
     In step S 305 , the transmission section  104  waits for a randomly determined period of time to avoid conflicting with a response from any other wireless base station AP, before transmitting the generated probe response to the wireless terminal STA. 
     On the other hand, in the case where it is determined in step S 303  that the frame is the probe trigger frame, control is transferred to step S 306 . In step S 306 , the control section  101  determines whether or not the Trigger Field in the probe trigger frame stores trigger information destined to the own SSID. 
     In the case where it is determined in step S 306  that the Trigger Field stores the trigger information destined to the own SSID, the received probe request is the trigger-carrying probe request and is destined to the own wireless base station. Then, control is transferred to step S 307 . 
     In step S 307 , the control section  101  generates a multiplexed probe response in reply to the received trigger-carrying probe request. Note that the process of generating the multiplexed probe response will be discussed later in detail with reference to the flowchart of  FIG. 19 . 
     In step S 308 , the transmission section  104  waits for a predetermined period of time to avoid conflicting with a response from any other wireless base station AP, before transmitting the generated multiplexed probe response to the wireless terminal STA. 
     Note that, when the multiplexed probe response is to be transmitted, the transmission parameters such as the frequency band to be used and the transmission power are determined on the basis of the bandwidth information stored in the Bandwidth Information and of the information regarding the received signal strength stored in the Target RSSI from among the trigger information stored in the Trigger Field of the probe trigger frame and destined to the own SSID. 
     Upon completion of the processing of step S 305  or step S 308 , the process of executing the STA scan phase depicted in  FIG. 18  is terminated. 
     Note that, in the case where it is determined in step S 302  that the received probe request is neither broadcast nor destined to the own wireless base station (“NO” in S 302 ), or where it is determined in step S 306  that the received probe request is the trigger-carrying probe request but does not hold the trigger information destined to the own wireless base station (“NO” in S 306 ), the process depicted in  FIG. 18  is terminated without the transmission of a probe response or a multiplexed probe response. 
     The process of generating the multiplexed probe response corresponding to the processing of step S 307  of  FIG. 18  is explained below in detail with reference to the flowchart of  FIG. 19 . 
     In step S 351 , the control section  101  reads and acquires the common configuration information list stored in the storage section  102 . After acquiring the common configuration information list, the control section  101  performs the processing of steps S 352  through S 355  to generate a multiplexed probe response. 
     That is, the control section  101  successively takes one or multiple sets of configuration information requested by the received trigger-carrying probe request as the configuration information of interest and, by referencing the acquired common configuration information list, determines successively whether or not the state of the common flag set in each configuration information of interest is “Yes” (S 352  and S 353 ). 
     Of the sets of configuration information of interest in the common configuration information list, those with the state of the common flag determined to be “Yes” are stored as common information into the Frame Body (Probe Common Info.) in the wide band frame of the probe response multiplexed frame (S 354 ). The sets of configuration information of interest having the state of the common flag determined to be other than “Yes” (e.g., “No” or “Unknown”) are stored as unique information into the Frame Body (Not Probe Common Info.) in the narrow band frame (S 355 ). This is how the multiplexed probe response is generated. 
     After the multiplexed probe response is generated as described above, control is returned to step S 307  in  FIG. 18 . Step S 307  and subsequent steps are then repeated. 
     In the STA scan phase, as described above, when the wireless terminal STA has its power turned on, for example, the wireless terminal STA transmits the trigger-carrying probe request to each of the wireless base stations AP in the vicinity. The wireless terminal STA then receives multiplexed probe responses from the wireless base stations AP in the vicinity. 
     The multiplexed probe response is transmitted by multiplex communication in which the configuration information requested by the trigger-carrying probe request comes in two groups, i.e., common information common to the wireless base stations AP in the vicinity and unique information not common thereto. Thus, even in the case where the active scan method is adopted for using wireless LAN services, the time required for active scans is shortened. This makes it possible to perform handover at higher speeds when the wireless terminal STA switches wireless base stations AP while on the move, for example. 
     2. Alternative Example 
     It has been explained above that in the communication apparatus  10  ( FIG. 2 ), the control section  101  ( FIG. 2 ) performs control to implement highly efficient active scans by transmitting the multiplexed probe response on the basis of the shared common configuration information list. Alternatively, this control function may be taken over by the control section or the communication section included in a communication module or in a communication chip (communication apparatus). 
     It has been also explained above that frequency multiplexing is carried out at the time of multiplexing the probe response. Alternatively, some other suitable multiplexing method may be adopted. It has been further explained above that the common information is transmitted by use of the wide band as the first band while the unique information is transmitted by use of the narrow band as the second band. Alternatively, some other band such as an intermediate band (middle band) may be utilized as a third band between the first band and the second band. This can address a variety of operation modes such as where a low band is assigned to wireless base stations AP with low priority whereas the middle band is assigned to other wireless base stations AP with high priority. 
     Note that the wireless terminal STA as the communication apparatus  10  may be configured as an electronic device having wireless communication capability, such as a smartphone, a tablet terminal, a mobile phone, a personal computer, a digital camera, a game console, a TV set, a wearable terminal, or a speaker device. Alternatively, the communication apparatus  10  may be configured as part of an apparatus constituting the wireless base station AP or the wireless terminal STA (e.g., a communication module or a communication chip). That is, examples of the communication apparatus  10  not only include an electronic device but also the communication module or communication chip (in this case, the communication apparatus  10  does not include the antenna  107 ). 
     The communication as understood in the foregoing description is not only wireless communication but also a type of communication in which wireless communication and wired communication coexist, i.e., in which wireless communication is performed over a certain segment while wired communication is implemented over another segment. As another alternative, the communication may be a type of communication in which wired communication is implemented from a first apparatus to a second apparatus while wireless communication is performed from the second apparatus to the first apparatus. 
     Note that the present technology is not limited to the preferred embodiment discussed above and may be implemented in diverse variations so far as they are within the scope of this technology. 
     The present technology may be implemented preferably in the following configurations: 
     (1) 
     A communication apparatus acting as a wireless base station, including: 
     a control section configured to acquire, from another wireless base station, information related to configuration information regarding the other wireless base station, in which 
     on the basis of the information related to the configuration information regarding the other wireless base station, the control section performs control to generate sharing verification information indicating whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station, and 
     the control section performs control to transmit the sharing verification information to the other wireless base station. 
     (2) 
     The communication apparatus as stated in (1) above, in which 
     the control section performs control to generate common configuration information determination information for determining whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station with respect to each configuration information regarding the wireless base station included in a response signal responding to a request signal from a wireless terminal, and 
     the control section performs control to update the common configuration information determination information on the basis of the sharing verification information transmitted from the other wireless base station. 
     (3) 
     The communication apparatus as stated in (2) above, in which 
     in a case where the configuration information regarding the other wireless base station included in the sharing verification information is different from the configuration information regarding the wireless base station included in the common configuration information determination information, the control section updates information related to the configuration information regarding the wireless base station included in the common configuration information determination information. 
     (4) 
     The communication apparatus as stated in (2) or (3) above, in which 
     in a case where the common configuration information determination information is updated, the control section performs control to generate the sharing verification information in such a manner as to reflect content of the updated common configuration information determination information, and 
     the control section performs control to transmit the generated sharing verification information to the other wireless base station. 
     (5) 
     The communication apparatus as stated in any one of (2) to (4) above, in which 
     on the basis of the common configuration information determination information, the control section performs control to multiplex the response signal including the configuration information regarding the wireless base station with the response signal including the configuration information regarding the other wireless base station transmitted from the other wireless base station, before transmitting the multiplexed response signal to the wireless terminal. 
     (6) 
     The communication apparatus as stated in (5) above, in which 
     the configuration information regarding the wireless base station includes common information common to the configuration information regarding the other wireless base station and unique information unique to the wireless base station, and 
     on the basis of the common configuration information determination information, the control section performs control to transmit the common information in a first band and the unique information in a second band that is narrower than the first band. 
     (7) 
     The communication apparatus as stated in (6) above, in which 
     in the first band, the same band is assigned to the wireless base station and to the other wireless base station, and 
     in the second band, a different band is assigned to each of the wireless base station and the other wireless base station. 
     (8) 
     The communication apparatus as stated in (6) or (7) above, in which 
     the response signal includes a first frame corresponding to the first band and a second frame corresponding to the second band, and 
     the response signal includes information regarding the length of the first frame and length of the second frame. 
     (9) 
     The communication apparatus as stated in (8) above, in which 
     the response signal includes information regarding the time for transmission using the first frame and the time for transmission using the second frame. 
     (10) 
     The communication apparatus as stated in (5) above, in which 
     the request signal includes multiplexing information related to multiplexing of the response signal, and 
     the control section performs control to transmit the response signal to the wireless terminal on the basis of the common configuration information determination information and the multiplexing information. 
     (11) 
     The communication apparatus as stated in (10) above, in which 
     the multiplexing information includes at least one of information indicating whether or not multiplexing is possible, information regarding a frequency band for transmitting the response signal, information indicating time until the response signal is transmitted, or information regarding a received signal strength. 
     (12) 
     The communication apparatus as stated in any one of (2) to (4) above, in which 
     the control section generates the common configuration information determination information on the basis of a notification signal transmitted from the other wireless base station. 
     (13) 
     The communication apparatus as stated in (12) above, in which 
     the control section updates the generated common configuration information determination information on the basis of the notification signal transmitted from the other wireless base station. 
     (14) 
     The communication apparatus as stated in (13) above, in which 
     the control section updates the information related to the configuration information regarding the wireless base station in the common configuration information determination information, based on the presence or absence of the configuration information regarding the other wireless base station included in the notification signal and on whether or not the configuration information regarding the wireless base station has a commonality with the other wireless base station. 
     (15) 
     The communication apparatus as stated in any one of (2) to (14) above, further including: 
     a storage section configured to store the common configuration information determination information. 
     (16) 
     The communication apparatus as stated in (5) above, in which 
     the multiplexing of the response signal includes frequency multiplexing. 
     (17) 
     A communication method for use with a communication apparatus of a wireless base station, the communication method including: 
     causing the communication apparatus to acquire, from another wireless base station, information related to configuration information regarding the other wireless base station; 
     on the basis of the information related to the configuration information regarding the other wireless base station, causing the communication apparatus to generate sharing verification information indicating whether or not the configuration information regarding the other wireless base station has a commonality with the wireless base station; and 
     causing the communication apparatus to transmit the sharing verification information to the other wireless base station. 
     (18) 
     A communication apparatus acting as a wireless terminal, the communication apparatus including: 
     a control section configured to perform control to transmit a request signal to a wireless base station, the request signal including multiplexing information related to multiplexing of a response signal responding to the request signal. 
     (19) 
     The communication apparatus as stated in (18) above, in which 
     the multiplexing information includes at least one of information indicating whether or not multiplexing is possible, information regarding a frequency band for transmitting the response signal, information indicating time until the response signal is transmitted, or information regarding a received signal strength. 
     (20) 
     A communication method for use with a communication apparatus of a wireless terminal, the communication method including: 
     causing the communication apparatus to perform control to transmit, to a wireless base station, a request signal including multiplexing information related to multiplexing of a response signal responding to the request signal. 
     REFERENCE SIGNS LIST 
       10  Communication apparatus,  101  Control section,  102  Storage section,  103  Data processing section,  104  Transmission section,  105  Reception section,  106  Antenna sharing section,  111  Analog signal conversion section,  112  RF transmission section,  121  RF reception section, AP Wireless base station, STA Wireless terminal