JP2013143624A - Access point, wireless terminal, and program for wireless lan for minimizing sensing time for multiple wireless communication bands - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an access point, wireless terminal, and program for a wireless LAN that minimize the sensing time for multiple wireless communication bands.SOLUTION: An access point has a first radio communication part for communicating in a first frequency band and a second radio communication part for communicating in a second frequency band. A beacon signal transmitted from the first radio communication part includes a network identifier and at least used channel information indicating whether the second radio communication part is used or not. The first frequency band is, e.g., the 2.4 GHz band or 5 GHz band based on IEEE 802.11, and the second frequency band is, e.g., 5 GHz band or 2.4 GHz band based on IEEE 802.11. A wireless terminal, upon receiving the beacon signal in the first frequency band from the access point, starts to sense a beacon signal in the second frequency band on the basis of the used channel information included in the received beacon signal.

Description

  The present invention relates to a communication sequence technique for a wireless terminal to find an access point for a wireless local area network (LAN).

  According to the wireless LAN, there is a MAC (Medium Access Control) layer technology for controlling packet transmission between a wireless terminal and an access point. The MAC frame exchanged between the wireless stations by the MAC layer is defined by, for example, the IEEE 802.11 standard.

  In the case of the IEEE802.11 infrastructure mode, the access point periodically transmits a control frame called a beacon signal (for example, about every 100 ms). The beacon signal advertises the presence of an access point to surrounding wireless terminals, and includes a network identifier SSID (Service Set IDentifier). As a result, the wireless terminal can easily find an access point (network identifier) existing in the vicinity. A wireless terminal that has discovered the presence of an access point by receiving a beacon signal executes a connection sequence for the access point in order to attempt the connection. In the ad hoc mode, the terminal also periodically transmits a beacon signal.

  Wireless LANs are not limited to home networks, but are constructed as public hotspots in various places. In addition, the wireless LAN communication function is not limited to personal computers, but has spread to terminals such as mobile phones and smartphones. Therefore, since a large number of access points and a large number of wireless terminals coexist, it is desirable for the wireless terminal to use a wireless communication band with as good communication quality as possible.

  In general, the wireless terminal 2 displays the SSIDs of a plurality of discovered access points on a display, and allows the user to select an access point. At this time, it is also preferable to display the radio wave intensity at each access point on the display. As long as the service contents are the same, the user naturally selects an access point with high radio field intensity. Of course, without the user himself / herself selecting an access point, the wireless terminal 2 automatically selects one having a good communication quality from among the connectable access points among the plurality of discovered access points. There may be.

  Conventionally, in order to find an access point, there is a technique for switching an access point search method based on whether a wireless terminal is within or out of range (see, for example, Patent Document 1). Further, communication quality information is included in a beacon signal notified by a base station, and there is a technique in which a wireless terminal switches a base station according to the communication quality information (see, for example, Patent Document 2).

  In recent years, wireless LAN access points equipped with a plurality of wireless communication units that communicate in different frequency bands have been commercially available.

  FIG. 1 is a system configuration diagram having an access point capable of communicating in a plurality of different radio bands.

  One access point 1 connects to the Internet via an access network, and the other communicates with the wireless terminal 2 via air. A wireless terminal 2 located in an area where radio waves transmitted from the access point 1 reach can connect to the Internet via the access point 1. According to FIG. 1, the wireless terminal 2 can discover a plurality of access points 1.

  According to FIG. 1, the wireless LAN access point 1 includes a plurality of wireless communication units so as to communicate with the wireless terminal 2 in a plurality of different frequency bands. Specifically, the access point 1 has a first wireless communication unit that communicates in the 2.4 GHz band and a second wireless communication unit that communicates in the 5 GHz band. For example, according to the IEEE802.11n communication standard, a maximum transmission speed of 600 Mbps (channel bonding with a bandwidth of 40 MHz and 4 streams) and an effective speed of 100 Mbps or more are realized using a frequency band of 2.4 GHz / 5 GHz.

  In order to perform data communication via the access point 1, the wireless terminal 2 must first discover the presence of the access point 1. As a method for discovering the access point 1, there are “active scan” and “passive scan”. In “active scan”, the wireless terminal 2 transmits a probe request signal, and the wireless terminal 2 receives the probe response signal transmitted by the access point 1 that has received the probe request signal. On the other hand, in the “passive scan”, the wireless terminal 2 passively receives a beacon signal transmitted from the access point 1 to discover the presence of the access point 1. When the access point 1 has wireless communication units in two frequency bands of 2.4 GHz / 5 GHz, a beacon signal including an SSID is broadcast from the access point 1 for each frequency band.

  Hereinafter, the infrastructure mode will be described on the assumption that the access point transmits a beacon signal. Of course, in the ad hoc mode, the terminal transmits a beacon signal.

JP 2005-012539 A Japanese Patent Laid-Open No. 6-244781

  FIG. 2 is a sequence diagram including a beacon signal in the prior art.

According to FIG. 2, the access point 1 constantly reports beacon signals (for example, at intervals of about 100 ms) for each of the 2.4 GHz band and the 5 GHz band. Assume that the wireless terminal 2 senses (searches) whether there is a notification of a beacon signal from an access point that is a partner to which each of the 2.4 GHz band and the 5 GHz band, for example, 10 channels is connected. In this case, the wireless terminal 2 needs to wait for a beacon signal for at least 100 ms in each channel. Then, it takes a search time of at least about 2 seconds to sense all channels as follows.
100 msec x (10 channels x 2 bands) = 2 sec
Thereafter, the wireless terminal 2 that has received the beacon signal connects to the access point according to a predetermined procedure of the standard.

  Further, according to the standard, the frequency is shared with other systems such as a radar in the 5 GHz band. For this purpose, the access point 1 monitors the frequency channel for a time of about 30 minutes, for example, and confirms that there is no other system that may affect the frequency channel. In addition, the access point 1 needs to determine whether or not there is no problem even if radio waves are transmitted through the frequency channel. That is, in the 5 GHz band, active scan cannot be used as a method for confirming the presence of the access point 1. As a result, in order for the wireless terminal to connect to the access point, there is a problem in transmitting the probe request packet without monitoring the frequency channel and confirming the signal transmitted from the access point 1. It was. For this reason, in order to search for an access point operating in the 5 GHz band, the wireless terminal has to search for a beacon signal for all channels, and there is a problem that it takes time. The beacon signal is found on any one of all channels in the 5 GHz band. For this reason, the wireless terminal must search in all channels in order to search for a beacon signal.

  Furthermore, according to the wireless LAN in the prior art, a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method is adopted in which the same channel is temporally transferred to establish communication between a plurality of terminals. Therefore, according to the active scan, the exchange of packets for the purpose of searching increases, and there is a fear that the exchange of packets for the purpose of data communication is hindered.

  Therefore, an object of the present invention is to provide a wireless LAN access point, a wireless terminal, and a program that shorten the search time for a plurality of wireless communication bands as much as possible.

According to the present invention, an access point for a wireless LAN (Local Area Network) having a first wireless communication unit that communicates in a first frequency band and a second wireless communication unit that communicates in a second frequency band In
The beacon signal transmitted from the first wireless communication unit includes at least usage channel information indicating whether or not the second wireless communication unit is used together with a network identifier.

According to another embodiment of the access point of the present invention,
The first frequency band is a 2.4 GHz band or a 5 GHz band based on IEEE802.11.
The second frequency band is also preferably a 5 GHz band or a 2.4 GHz band based on IEEE802.11.

  According to another embodiment of the access point of the present invention, it is also preferable that the used channel information included in the beacon signal is represented by a bit set / reset with respect to the used channel number of the usable second wireless communication unit. .

According to the present invention, a wireless terminal that communicates with the aforementioned access point,
When a beacon signal is received from the access point in the first frequency band, sensing of the beacon signal in the second frequency band is started based on use channel information included in the beacon signal.

According to another embodiment of the wireless terminal of the present invention,
A connection purpose identifier storage means for storing a network identifier as a connection purpose in advance;
A connection purpose identifier determining means for determining whether or not the network identifier contained in the received beacon signal is stored in the connection purpose identifier storage means;
It is also preferable to start sensing the beacon signal in the second frequency band based on the used channel information included in the beacon signal only when it is determined to be true by the connection purpose identifier determination unit.

According to the present invention, a computer mounted on a wireless LAN access point having a first wireless communication unit that communicates in a first frequency band and a second wireless communication unit that communicates in a second frequency band. In the program that makes
The beacon signal transmitted from the first wireless communication unit causes the computer to function so as to include at least usage channel information indicating whether or not the second wireless communication unit is used together with the network identifier.

According to the present invention, there is provided a program for causing a computer mounted on a wireless terminal that communicates with the above-described access point to function.
When a beacon signal is received from the access point in the first frequency band, the computer is caused to function to start sensing the beacon signal in the second frequency band based on the use channel information included in the beacon signal. It is characterized by.

According to the present invention, a wireless LAN access point beacon signal transmission method includes a first wireless communication unit that communicates in a first frequency band and a second wireless communication unit that communicates in a second frequency band. In
The beacon signal transmitted from the first wireless communication unit includes at least usage channel information indicating whether or not the second wireless communication unit is used together with a network identifier.

According to the present invention, there is provided a beacon signal receiving method for a wireless terminal that communicates with the access point described above,
When a beacon signal is received from the access point in the first frequency band, sensing of the beacon signal in the second frequency band is started based on use channel information included in the beacon signal.

  According to the wireless LAN access point, wireless terminal, and program of the present invention, the search time for a plurality of wireless communication bands can be shortened as much as possible.

It is a system configuration diagram having an access point capable of communicating in a plurality of different wireless bands. It is a sequence diagram containing the beacon signal in a prior art. It is a sequence diagram containing the beacon signal in this invention. It is a frame block diagram of the beacon signal in the present invention. It is a flowchart showing the 1st process of the radio | wireless terminal in this invention. It is a flowchart showing the 2nd process of the radio | wireless terminal in this invention. It is a function block diagram of the access point in this invention. It is a function block diagram of the radio | wireless terminal in this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  According to a general wireless LAN, since it is frequently used in the 2.4 GHz band, the influence of interference from other access points and wireless terminals is large. For this reason, it is often possible to perform communication with good communication quality using the 5 GHz band. Specifically, according to the present invention, the wireless terminal can recognize the presence or absence of the 5 GHz band only by receiving a 2.4 GHz band beacon signal from the access point. As a result, the wireless terminal can shorten the time required to receive a 5 GHz band beacon signal.

  FIG. 3 is a sequence diagram including a beacon signal in the present invention with respect to FIG. 2 described above.

The access point 1 for wireless LAN has a first wireless communication unit that communicates in a first frequency band and a second wireless communication unit that communicates in a second frequency band. For example, when the wireless LAN communication method is based on IEEE802.11, there are the following two frequency bands.
(1) 1st frequency band = 2.4 GHz band based on IEEE802.11 2nd frequency band = 5 GHz band based on IEEE802.11 (The 2.4 GHz band is first monitored as a fundamental frequency)
(2) First frequency band = 5 GHz band based on IEEE802.11 Second frequency band = 2.4 GHz band based on IEEE802.11 (5 GHz band is first monitored as a fundamental frequency)

According to the present invention, the beacon signal transmitted from the first wireless communication unit includes at least usage channel information indicating whether or not the second wireless communication unit is used together with the SSID (network identifier). According to FIG. 3, the wireless terminal 2 can know whether or not the 5 GHz band is used only by monitoring the beacon signal in the 2.4 GHz band notified by the access point 1. That is, according to FIG. 3, compared with FIG. 2, the wireless terminal 2 only requires a search time of about 1 second as follows.
100 msec x (10 channels x 1 band (2.4 GHz)) = 1 sec

When the wireless terminal 2 desires to connect to the SSID 2 in the 5 GHz band, the search time is only about 1.1 seconds.
100 msec x (10 channels x 1 band (2.4 GHz)) +
100 msec x (1 channel x 1 band (5 GHz)) = 1.1 sec

  In addition, when the 5 GHz band is not operated at all, the wireless terminal 2 can know only by searching for 2.4 GHz, so there is no need to execute a useless search process for the 5 GHz band.

  When the wireless terminal 2 is a mobile phone or a smart phone that operates on a battery, such a useless search process can be omitted from the viewpoint of suppressing power consumption.

  FIG. 4 is a frame configuration diagram of a beacon signal in the present invention.

  The beacon signal is composed of a MAC frame. The MAC frame includes “frame control”, “DurationID”, “destination address”, “source address”, “BSSID (Basic Service Set IDentifier)”, “sequence control”, “frame body”, and “FCS”.

  “Frame control” includes various control information. Among them, a beacon signal is specified by “type” and “subtype”. “Type = 00” means a management frame, and “subtype = 1000” means a beacon signal.

  “DurationID” represents a scheduled period (μs) in which the radio link is used. “BSSID” (Basic Service Set IDentifier) represents the MAC address of the access point. “Sequence control” represents a sequence number of a MAC frame and a fragment number. “FCS” represents an error detection code.

  FIG. 4 shows information elements included in the message body of the beacon signal. Information elements are roughly divided into “beacon basic information” and “other information”.

Normally, the “beacon basic information” includes the following information.
・ Timestamp: Timer TSFTIMER value (μs unit)
・ Beacon Interval: Beacon period (1024μs unit)
-Capability Information: Presence of centralized polling control (PCF) or encryption-SSID (Service Set ID): ESSID or IBSSID
-Supported Rate: List of wireless transmission rates supported by the access point

  According to the present invention, “used channel information” is further included in “beacon basic information”. For example, a 2.4 GHz band beacon signal includes a bit string for identifying a 5 GHz band use channel. The wireless terminal can know the channel used in the 5 GHz band by knowing that the bit corresponding to the usable channel is set. Conversely, the bit being reset is not a usable channel. The use channel information is preferably not limited to the use channel information that can be used in the second wireless communication unit, but preferably includes the use channel information that can be used in the first wireless communication unit. The wireless terminal can recognize all the used channels in all the frequency bands by receiving one beacon signal.

  FIG. 5 is a flowchart showing the first processing of the wireless terminal in the present invention.

(S501) The wireless terminal 2 starts monitoring all channels (m = 1 to M) in the 2.4 GHz band. The process between S508 is repeated for channels 1 to M.
(S502) The radio terminal 2 loops for x milliseconds (for example, 100 msec) with S507 for each channel m.

(S503) The wireless terminal 2 senses a 2.4 GHz band beacon signal broadcast from the access point 1 for the channel m.
(S504) If the wireless terminal 2 cannot receive a beacon signal on the channel m in the 2.4 GHz band, the wireless terminal 2 proceeds to S508 and starts monitoring the next channel (m = m + 1) in the 2.4 GHz band. .
(S505) If the wireless terminal 2 can receive a beacon signal on the channel m in the 2.4 GHz band, whether or not the SSID of the beacon signal is a connection purpose identifier stored in advance in the connection purpose identifier storage unit. Determine whether. That is, the character string match between the SSID and the connection purpose identifier is determined. If it is not a connection purpose identifier, the wireless terminal 2 proceeds to S507, and further continues monitoring on the channel m in the 2.4 GHz band. The connection purpose identifier storage unit includes a network identifier (SSID) that the user desires to connect to.

(S506) When the SSID of the beacon signal is a connection purpose identifier, the wireless terminal 2 determines whether or not the use channel information is included in the beacon signal. At this time, communication quality is obtained from the beacon signal. The communication quality may be obtained by measuring a beacon signal, or may include communication quality information in the beacon signal itself. If the used channel information is included and any channel bit of the 5 GHz band is not set, the wireless terminal 2 proceeds to S507 and continues to monitor the channel m of the 2.4 GHz band.

(S507) The wireless terminal 2 loops with S502 until monitoring on the channel m has passed x milliseconds. Thereafter, when x milliseconds have elapsed, the process proceeds to S508, and monitoring of the next channel (m = m + 1) in the 2.4 GHz band is started.

(S508) The wireless terminal 2 loops with S501 until all the channels in the 2.4 GHz band (m = 1 to M) are monitored. When monitoring of all channels (m = 1 to M) is completed without receiving a beacon signal including a connection purpose identifier (SSID), the wireless terminal 2 is within a range where radio waves based on the connection purpose identifier reach. It is recognized that they are not located.

  Note that it is also preferable to preferentially monitor channels that have been successfully connected in the past as the monitoring order of the channel m in S501. For example, in the 2.4 GHz band, since there is radio wave interference between adjacent channels, it is common to use channels with a gap such as 1, 6, 11 channels. For this reason, when these channels are already connected channels, the beacon signal from the connection purpose identifier may be received as quickly as possible by preferentially monitoring.

(S509) If the wireless terminal 2 determines in S506 that any channel bit in the 5 GHz band is set, the wireless terminal 2 starts monitoring the channel in use in the 5 GHz band. The wireless terminal 2 senses the beacon signal for y milliseconds in the use channel in the 5 GHz band broadcast from the access point 1. At this time, communication quality is obtained from the beacon signal. The communication quality may be obtained by measuring a beacon signal, or may include communication quality information in the beacon signal itself.

(S510) Next, even if the wireless terminal 2 has the same SSID (connection purpose identifier), it is also preferable to select the 2.4 GHz band or the 5 GHz band according to the communication quality. Here, the communication quality of the 2.4 GHz band is compared with the communication quality of the 5 GHz band.

  The “communication quality” may be a reception level, for example. Further, it may be communication quality information included in the beacon signal itself. Further, it may be a congestion degree (for example, an index generated from a retransmission frequency or the like). The communication environment of the 2.4 GHz band wireless LAN is frequently used, and the number of times of access control in the CSMA / CA system is increasing (congested). Therefore, it is also preferable to set the degree of congestion as communication quality.

(S511) When the communication quality of the 2.4 GHz band is high, the used channel number of the 2.4 GHz band is set as the connection channel for the SSID.
(S512) When the communication quality in the 5 GHz band is high, the channel number used in the 5 GHz band is set as the connection channel for the SSID.

  FIG. 6 is a flowchart showing the second processing of the wireless terminal in the present invention.

  According to FIG. 5, the wireless terminal 2 detects a channel used in the 5 GHz band for the connection purpose identifier (SSID) discovered first by searching in the 2.4 GHz band. However, when a plurality of types of connection purpose identifiers are stored in the connection purpose identifier storage unit (memory), the user generally desires to connect to an access point with the best communication quality. Therefore, according to FIG. 6, it is possible to connect to an access point having the best communication quality for all the access points that can be connected in the 2.4 GHz band and the 5 GHz band.

(S601) The wireless terminal 2 starts monitoring all channels (m = 1 to M) in the 2.4 GHz band. The processing between S608 is repeated for channels 1 to M.
(S602) The wireless terminal 2 loops for x milliseconds (for example, 100 msec) with S607 for each channel m.

(S603) The wireless terminal 2 senses a 2.4 GHz band beacon signal broadcast from the access point 1 for the channel m.
(S604) If the wireless terminal 2 cannot receive a beacon signal in the channel m of the 2.4 GHz band, the wireless terminal 2 proceeds to S608 and starts monitoring the next channel (m = m + 1) in the 2.4 GHz band. .
(S605) If the wireless terminal 2 can receive a beacon signal on the channel m of the 2.4 GHz band, whether or not the SSID of the beacon signal is a connection purpose identifier stored in advance in the connection purpose identifier storage unit. Determine whether. If it is not the connection purpose identifier, the wireless terminal 2 proceeds to S607, and continues to monitor the channel m in the 2.4 GHz band.

(S606) When the SSID of the beacon signal is the connection purpose identifier, the wireless terminal 2 registers the SSID of the 2.4 GHz band beacon signal and the used channel information in the connection candidate list. At this time, communication quality is obtained from the beacon signal. This communication quality is also registered in the connection candidate list in association with the SSID and the used channel information.

(S607) The wireless terminal 2 loops with S602 until the monitor on the channel m has passed x milliseconds. Thereafter, when x milliseconds have elapsed, the process proceeds to S608, and monitoring of the next channel (m = m + 1) in the 2.4 GHz band is started.

(S608) The wireless terminal 2 loops between S601 until all the channels in the 2.4 GHz band (m = 1 to M) are monitored. When monitoring of all channels (m = 1 to M) is completed without receiving a beacon signal including a connection purpose identifier (SSID), the wireless terminal 2 is within a range where radio waves based on the connection purpose identifier reach. It is recognized that they are not located.

(S609) The wireless terminal 2 determines whether the connection candidate list includes channel information for 5 GHz band. When the use channel information of 5 GHz band is not included, the wireless terminal 2 proceeds to S614. In other words, only the used channel of the 2.4 GHz band that has already been received may be the connection target.

(S610) When 5 GHz band use channel information (N) is registered in the connection candidate list, the wireless terminal 2 repeats the process with S613 only for the 5 GHz band use channel.
(S611) The wireless terminal 2 senses a beacon signal in the use channel in the 5 GHz band notified from the access point 1 for y milliseconds. Here, according to the present invention, since sensing is performed only for the relevant channel in the 5 GHz band whose existence has been confirmed by the beacon signal in the 2.4 GHz band, it is not necessary to sense all the channels in the 5 GHz band.
(S612) With respect to the detected 5 GHz band beacon signal, the communication quality is acquired from the beacon signal, and is associated and registered in the connection candidate list. At the time when the use channel information is obtained by the 2.4 GHz band monitor, the use channel information of the 5 GHz band is already registered in the connection candidate list.
(S613) The wireless terminal 2 repeats monitoring of the next usable channel in the 5 GHz band with S610.

(S614) Finally, the wireless terminal 2 sets the SSID and the used channel number having the highest communication quality among the SSID (connection purpose identifier) and the used channel number registered in the connection candidate list as the connection channel.

  As shown in FIG. 6, the “connection candidate list” is a list in which the SSID, the channel number used (and the communication quality) are linked. According to FIG. 6, the connection purpose identifier “SSID1” is associated with CH21 in the 2.4 GHz band and CH51 in the 5 GHz band as the use channel numbers. The connection purpose identifier “SSID2” is associated with CH22 in the 2.4 GHz band and CH52 in the 5 GHz band as the use channel numbers. The channel number CHxx is used for simple explanation and is different from the channel number in the actual standard.

  According to S501 to S512 of FIG. 5 and S601 to S614 of FIG. 6 described above, when one access point has a plurality of wireless communication units, each wireless communication unit uses the same SSID. Explains. However, of course, for example, different SSIDs may be used for the 2.4 GHz band wireless communication unit and the 5 GHz band wireless communication unit. The wireless terminal cannot recognize these different SSIDs as being broadcast from the same access point, but if these SSIDs are held in the connection purpose identifier storage unit as connection purpose identifiers, these SSIDs are included in the connection candidate list. Can be a candidate for connection.

  FIG. 7 is a functional block diagram of an access point in the present invention.

  According to FIG. 7, the access point 1 for wireless LAN in the present invention includes a plurality of antennas and a wireless communication unit so as to communicate with the wireless terminal 2 in a plurality of different frequency bands. Specifically, the access point 1 includes a 2.4 GHz band modulation unit and demodulation unit, and a 5 GHz band modulation unit and demodulation unit. The antenna may be shared for the 2.4 GHz band and the 5 GHz band.

  The radio signal received by the 2.4 GHz band antenna is input to the 2.4 GHz band circulator. The circulator outputs the signal to the 2.4 GHz band demodulator. The demodulator demodulates the received signal at a predetermined carrier frequency and outputs a baseband signal in the MAC frame format to the received frame analyzer. The received frame analysis unit analyzes the MAC header in the baseband signal in the MAC frame format. The analyzed received frame is output to the path control unit and transmitted to the access network via the access network side communication interface. Note that the exchange of packets based on the connection sequence with the wireless terminal 2 is executed by the connection establishment unit. The connection establishment unit executes the connection sequence shown in FIG.

  Also, the transmission data received from the access network (or connection establishment unit) is transferred to the 2.4 GHz band transmission frame generation unit by the path control unit. The transmission frame generation unit generates transmission data into a transmission frame that can be transmitted wirelessly, and outputs the transmission frame to a 2.4 GHz band modulation unit. The modulation unit modulates the transmission frame at a predetermined carrier frequency and performs high-frequency conversion, and outputs the transmission signal to the circulator. The circulator outputs the signal to a 2.4 GHz band antenna, and is transmitted from the antenna to the wireless terminal 2 via the air.

  A circulator is a passive circuit element having three or more ports, and has a characteristic that a high-frequency signal input to the first port is output only to the second port. For example, by connecting a matched load to a three-port circulator (Y-junction type), a signal is transmitted only in one direction between the remaining two ports. Specifically, an input signal from port A is output to port B, and an input signal from port B is output to port C.

  Similarly to the 2.4 GHz band in the 5 GHz band, the radio signal received by the antenna is demodulated by the demodulation unit of the 5 GHz band, the MAC header is analyzed by the reception frame analysis unit, and transmitted to the access network. Transmission data received from the access network is generated into a transmission frame by the transmission frame generation unit, modulated into a transmission signal by the modulation unit, and transmitted from the antenna.

  Here, according to the access point 1 of the present invention, the transmission frame generation unit has a beacon signal transmission function. The beacon signal transmission function generates a beacon signal including at least usage channel information indicating whether or not the second wireless communication unit is used together with the network identifier. The generated beacon signal is based on FIG. 4 described above. This used channel information is acquired from the used channel information storage unit. The generated beacon signal is output to the 2.4 GHz band modulation unit in the same manner as the transmission data.

  FIG. 8 is a functional configuration diagram of the wireless terminal in the present invention.

  According to the wireless terminal 2, the received signal received from the access point 1 is input to the 2.4 GHz bandpass filter and the 5 GHz bandpass filter. Each received signal that has passed through the filter is input to each circulator for each frequency band. The received signal output from the circulator is input to each demodulator for each frequency band. The demodulator demodulates the received signal into a received frame, and outputs the received frame to the received frame analyzer. The received frame analysis unit analyzes the MAC header of the received frame and also analyzes whether or not it is the beacon signal of FIG. 4 described above. If it is a beacon signal, the used channel information included therein is also acquired.

  The connection purpose identifier storage unit stores in advance a network identifier serving as a connection purpose. This is set by the user or an application for connection.

  The connection purpose identifier determination unit determines whether or not the network identifier included in the received beacon signal is stored in the connection purpose identifier storage unit. Here, only when it is determined to be true, the 5 GHz band demodulator (first frequency band) starts to sense the beacon signal in the 5 GHz band (second frequency band) based on the used channel information included in the beacon signal. 2 demodulator).

  According to the wireless terminal 2, transmission data to the access point 1 is input to the transmission frame generation unit and is generated into a transmission frame. Then, the transmission frame is output to the modulation unit of the selected frequency band. The modulation unit modulates the transmission frame at a predetermined carrier frequency and performs high-frequency conversion, and outputs the transmission signal to the circulator. The circulator outputs the signal to the antenna and transmits the signal from the antenna to the access point 1 through the air. Note that when the transmission signal is present on the wireless LAN, the modulation unit suppresses transmission of the wireless signal from the antenna to avoid a collision based on the CSMA / CA scheme.

  As described above in detail, according to the wireless LAN access point, wireless terminal and program of the present invention, the search time for a plurality of wireless communication bands can be shortened as much as possible.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

1 Access point 2 Wireless terminal

Claims (9)

In an access point for a wireless LAN (Local Area Network) having a first wireless communication unit communicating in a first frequency band and a second wireless communication unit communicating in a second frequency band,
An access point, wherein the beacon signal transmitted from the first wireless communication unit includes at least usage channel information indicating whether or not the second wireless communication unit is used, together with a network identifier. The first frequency band is a 2.4 GHz band or a 5 GHz band based on IEEE802.11.
The access point according to claim 1, wherein the second frequency band is a 5 GHz band or a 2.4 GHz band based on IEEE802.11.   3. The access point according to claim 1, wherein the use channel information included in the beacon signal is represented by a bit set / reset with respect to a use channel number of a second wireless communication unit that can be used. 4. . A wireless terminal that communicates with the access point according to any one of claims 1 to 3,
When the beacon signal is received from the access point in the first frequency band, sensing of the beacon signal in the second frequency band is started based on the used channel information included in the beacon signal. Wireless terminal. A connection purpose identifier storage means for storing a network identifier as a connection purpose in advance;
A connection purpose identifier determining means for determining whether or not a network identifier included in the received beacon signal is stored in the connection purpose identifier storage means;
The sensing of the beacon signal in the second frequency band is started based on the use channel information included in the beacon signal only when it is determined to be true by the connection purpose identifier determination unit. 4. A wireless terminal according to 4. In a program for causing a computer mounted on an access point for a wireless LAN having a first wireless communication unit communicating in a first frequency band and a second wireless communication unit communicating in a second frequency band to function,
The beacon signal transmitted from the first wireless communication unit causes the computer to function so as to include at least used channel information indicating whether or not the second wireless communication unit is used together with the network identifier. program. A program for causing a computer mounted on a wireless terminal that communicates with the access point according to any one of claims 1 to 3 to function,
When receiving the beacon signal in the first frequency band from the access point, the computer is configured to start sensing the beacon signal in the second frequency band based on the used channel information included in the beacon signal. A program for a wireless terminal characterized by functioning. In a method for transmitting a beacon signal of a wireless LAN access point having a first wireless communication unit communicating in a first frequency band and a second wireless communication unit communicating in a second frequency band,
The beacon signal transmitted from the first wireless communication unit includes at least usage channel information indicating whether or not the second wireless communication unit is used together with a network identifier. A beacon signal receiving method for a wireless terminal that communicates with the access point according to any one of claims 1 to 3,
When the beacon signal is received from the access point in the first frequency band, sensing of the beacon signal in the second frequency band is started based on the used channel information included in the beacon signal. Beacon signal reception method for a wireless terminal.

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