JP6616805B2 - Access point, wireless terminal, program and method for controlling beacon standby - Google Patents

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).

  FIG. 1 is a system configuration diagram including a wireless terminal and an access point.

  According to FIG. 1, the access point 1 is connected to the Internet via one access network and communicates with the wireless terminal 2 via the other. A wireless terminal 2 located in a wireless LAN area around the access point can connect to the Internet (upper network) via the access point 1. According to FIG. 1, the wireless terminal 2 is located at a place where it can communicate with the three access points 1. For example, the wireless terminal 2 discovers an access point AP2 for connection, and then tries to connect to the Internet via the access point AP2.

  A wireless LAN employs a MAC (Media Access Control) layer technique 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.

According to the infrastructure mode of IEEE802.11, there are two methods, “active scan method” and “passive scan method”, for a wireless terminal to discover an access point via a wireless LAN.
In the “active scan method”, a wireless terminal broadcasts a probe request toward an access point and receives a probe response from the access point, thereby discovering the access point.
In the “passive scan method”, an access point periodically broadcasts a beacon, and a wireless terminal receives the beacon, thereby discovering the access point.
Note that a beacon, a probe request, and a probe response are a type of management control signal exchanged between an access point and a wireless terminal.

  Generally, a wireless terminal is equipped with functions of both an active scan method and a passive scan method. A wireless terminal that has found an access point by one of these two methods executes a connection sequence for the access point to be connected.

  FIG. 2 is a sequence diagram based on the active scan method.

  According to FIG. 2, first, the wireless terminal 2 transmits a probe request in a broadcast manner. When transmitting such a frame, the power consumption of the wireless terminal 2 increases. The probe request transmitted by the wireless terminal 2 is received by all the access points 1 (AP1, AP2, AP3) that exist within the reachable range of the radio wave and operate on the same channel.

  On the other hand, each access point 1 returns a probe response to the wireless terminal 2. At this time, according to the technique of the wireless LAN MAC layer, the transmission timing of each access point 1 is controlled so that probe responses transmitted to each other do not collide. For example, according to wireless LAN, 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.

  On the other hand, the wireless terminal 2 waits for a probe response for a relatively short time with relatively small power consumption. When the wireless terminal 2 receives the probe response from the access point AP2 for connection within the standby time, the wireless terminal 2 executes a connection sequence for the access point AP2.

  FIG. 3 is a sequence diagram based on the passive scan method.

  According to FIG. 3, each access point 1 transmits a beacon periodically and in a broadcast manner. At this time, the wireless terminal 2 waits for a beacon with a relatively small power consumption and at least for a relatively long time equal to or longer than the beacon cycle time. When the wireless terminal 2 receives a beacon from the access point AP2 for connection within the standby time range, the wireless terminal 2 executes a connection sequence for the access point AP2.

The access point broadcasts a beacon at all times (for example, at intervals of about 100 ms) in the 2.4 GHz band, for example. The wireless terminal needs to sense (search) whether there is a notification of a beacon from an access point that is a partner to which each of the 2.4 GHz band, for example, 10 channels is connected. In this case, the wireless terminal needs to wait for a beacon for at least 100 ms in each channel. Then, at least about 1 second of standby time is required to sense all channels as follows.
100 msec x 10 channels = 1 sec
When the wireless terminal 2 is a mobile phone or a smartphone that operates on a battery, it is effective from the viewpoint of suppressing power consumption to shorten such a standby time as much as possible.

  As described above, the active scan method temporarily increases the power consumption for transmitting the probe request, but the probe response standby time is relatively short. On the other hand, although the passive scan method consumes relatively little power, the beacon standby time is relatively long. As a result, the active scan method that can find an access point in a relatively short time consumes less overall energy than the passive scan method. For this reason, the “active scan method” is generally used frequently in wireless terminals, which can detect an access point in a relatively short time with a relatively small amount of energy consumption. When the wireless terminal enters the area of the access point to be connected, the wireless terminal transmits a probe request in the active scan method and receives a probe response to the probe request, thereby discovering the access point.

  In addition, as a conventional technique, there is a technique of switching to either an active scan method or a passive scan method based on whether a wireless terminal is within or out of service in order to find an access point (see, for example, Patent Document 1).

JP 2005-12539 A

IEEE802.11-10 / 0922r2, "Achievable Gains in AP Discovery", [online], [Search May 13, 2013], Internet <URL: https://mentor.ieee.org/802.11/dcn/10 /11-10-0922-02-0fia-achievable-gains-in-ap-discovery.pptx>

  However, there is a problem that a wireless terminal needs a relatively long time to discover an access point via a wireless LAN (see Non-Patent Document 1, for example). In particular, an access point installed in a public area can be freely connected from a general user's wireless terminal. On the other hand, there are many cases where the wireless terminal cannot grasp the channel used and the installation location of the access point. Therefore, it is necessary for the wireless terminal to periodically search all channels that can be used and check whether or not there is an access point for connection. Such a sequence takes time.

  According to the “active scan method”, a wireless terminal generally transmits one probe request by broadcast without designating a network identifier of an access point for connection. The probe request is received by all access points located in the vicinity of the probe request, and probe responses are returned from all access points including those not intended for connection. On the other hand, the wireless terminal connects only to the access point that has returned the probe response including the network identifier of the access point to be connected. That is, the probe response transmitted by the access point other than the connection purpose is simply ignored, and the radio resource is merely wasted.

Specifically, according to Non-Patent Document 1, it can be calculated as follows.
2.4 GHz active scan per channel = approx. 15 ms
5 GHz band passive scan per channel = approx. 100 ms
Search time for all 13 channels in the 2.4 GHz band and all 19 channels in the 5 GHz band
= (15ms x 13ch) + (100ms x 19ch) = 2,095ms

  On the other hand, according to the “passive scan method”, since it is not necessary to send a probe request from a wireless terminal, it is not necessary to receive a probe response from an access point other than the connection purpose, and wireless resources are wasted. There is no.

  However, as described above, the passive scan method needs to wait for a beacon for a long time, and has a problem that it is inferior from the viewpoint of the amount of energy consumption compared to the active scan method.

Specifically, for the active scan method (see FIG. 2), the “energy amount required for transmitting the probe request” is calculated as follows.
Signal transmission power at wireless terminal = 200mW (assumed)
Received signal power at wireless terminal = 40mW (assumed)
Probe request data size = 300 bytes (assumed)
Probe request data rate = 6 Mbps (assumed)
Time required for transmission = (300 bytes x 8 bits) / (6 x 106 bps) = 400 x 10-6 s
The amount of energy required to send a probe request
= 200mW x (time required for transmission)
= 200mW x (400 x 10-6s)
= 80 × 10-6 [J]
The “energy amount required for standby reception of the probe response” is calculated as follows.
Amount of energy required for standby reception of probe response
= 40mW × 15ms
= 600 × 10-6 [J]
Finally, according to the active scan method, the “energy amount per channel” is calculated as follows.
Energy amount per channel of active scan method
= 80 + 600
= 680 [μJ]

On the other hand, for the passive scanning method (see FIG. 3), “the amount of energy required for beacon standby reception” is calculated as follows.
Beacon standby time (per channel) = 100 ms
Energy required for beacon standby reception
= 40mW × 100ms
= 4000 [μJ]

  As a result, it can be understood that the energy amount 4000 [μJ] consumed in the passive scan method is larger than the energy amount 680 [μJ] consumed in the active scan method.

  According to Patent Document 1, a wireless terminal is generally active when it recognizes that it is located under an access point (or when operated by a user or when a data transmission / reception application requests). The scan method is executed and a probe request is transmitted. On the contrary, when it is recognized that it is not located under the access point, a passive scan is executed, and a beacon standby state is set.

  However, in an area under the access point, an active scan method that further consumes radio resources is executed in spite of having to save radio resources as much as possible. On the other hand, in a place where the waste of radio resources is not a problem and where the access point is not located, a passive scan method is executed in which the amount of energy consumption increases with a relatively long standby time. In the first place, the wireless terminal cannot know whether it is located under the access point.

  Therefore, the present invention provides an access point, a wireless terminal, a program, and a method capable of controlling a beacon standby so that a relatively small amount of energy is consumed and a relatively short standby time. Objective.

According to the present invention, in an access point that communicates with a plurality of wireless terminals via a wireless LAN (Local Area Network),
For each wireless terminal, a wireless LAN communication means for communication using each channel used in the first frequency band,
For each wireless terminal, time difference calculating means for calculating time difference information from the current time to the next beacon transmission time in the used channel;
Pointer signal generating means for generating a pointer signal including channel information and network identifier used in the first frequency band and time difference information for each wireless terminal ;
To a plurality of mobile stations, a pointer signal, and a pointer signal communication means to send using only one particular channel in the second frequency band,
Each wireless terminal is configured to wait for a beacon of the channel in use in the first frequency band at the timing when the time difference information has elapsed after receiving the pointer signal.

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

According to another embodiment of the access point of the present invention,
The pointer signal generation means includes a plurality of pairs of used channel information and network identifiers and time difference information in the pointer signal, and associates the time difference information with each set,
It is also preferable that the wireless terminal waits for the beacon of the use channel in order from the use channel with the shortest time difference information until the next beacon.

According to another embodiment of the access point of the present invention,
The pointer signal communication means preferably has a passive method for periodically transmitting a pointer signal or an active method for transmitting a pointer signal when a pointer request for the access point is received from a wireless terminal.

According to the present invention, in a wireless terminal that communicates with an access point via a wireless LAN,
Specific channel storage means for previously storing one specific channel of a pointer signal in the second frequency band for a plurality of access points ;
Wireless LAN communication means for communicating with an access point using a predetermined use channel in the first frequency band;
Using a specific channel of the second frequency band, a pointer signal including the used channel information and network identifier in the first frequency band and time difference information from the current time to the next beacon transmission time in the used channel is received. Pointer signal receiving means for
The wireless LAN communication means receives a signal from the access point for connection in the first frequency band based on the used channel information and the network identifier included in the pointer signal at the timing when the time difference information elapses after receiving the pointer signal. A probe response after transmitting a beacon or probe request is awaited.

According to another embodiment of the wireless terminal of the present invention,
The wireless LAN communication means preferably transitions to the sleep state based on the time difference information included in the pointer signal until the time difference elapses after reception of the pointer signal.

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

According to another embodiment of the wireless terminal of the present invention,
The pointer signal includes a plurality of pairs of used channel information and network identifiers and time difference information, and time difference information is associated with each set,
It is also preferable that the wireless LAN communication unit waits for the beacon of the use channel in order from the use channel with the shortest time difference information until the next beacon.

According to another embodiment of the wireless terminal of the present invention,
The pointer signal receiving means preferably has a passive method for waiting for a pointer signal or an active method for waiting for a pointer signal after transmitting a pointer request to an access point.

According to the present invention, in a program for causing a computer mounted on an access point to communicate with a plurality of wireless terminals via a wireless LAN,
For each wireless terminal, a wireless LAN communication means for communication using each channel used in the first frequency band,
For each wireless terminal, time difference calculating means for calculating time difference information from the current time to the next beacon transmission time in the used channel;
Pointer signal generating means for generating a pointer signal including channel information and network identifier used in the first frequency band and time difference information for each wireless terminal ;
To a plurality of mobile stations, a pointer signal, cause the computer to function as a pointer signal communication means to send using only one particular channel in the second frequency band,
Each wireless terminal is configured to wait for a beacon of the channel in use in the first frequency band at the timing when the time difference information has elapsed after receiving the pointer signal.

According to the present invention, in a program for causing a computer mounted on a wireless terminal communicating with an access point via a wireless LAN to function,
Specific channel storage means for previously storing one specific channel of a pointer signal in the second frequency band for a plurality of access points ;
Wireless LAN communication means for communicating with an access point using a predetermined use channel in the first frequency band;
Using a specific channel of the second frequency band, a pointer signal including the used channel information and network identifier in the first frequency band and time difference information from the current time to the next beacon transmission time in the used channel is received. The computer functions as a pointer signal receiving means to
The wireless LAN communication means receives a signal from the access point for connection in the first frequency band based on the used channel information and the network identifier included in the pointer signal at the timing when the time difference information elapses after receiving the pointer signal. The computer is made to function so as to wait for a probe response after transmitting a beacon or a probe request.

According to the present invention, in an access point discovery method in which a wireless terminal discovers an access point via a wireless LAN,
The plurality of wireless terminals and the plurality of access points store one specific channel of the pointer signal in the second frequency band in advance,
Each and each wireless terminal and the access point, which communicates with a predetermined channel used in the first frequency band,
The access point includes the use channel information and network identifier in the first frequency band using the specific channel in the second frequency band, and time difference information from the current time to the next beacon transmission time in the use channel. A first step of transmitting a pointer signal to the wireless terminal;
The wireless terminal has a second step of waiting for a beacon of the channel in use in the first frequency band at the timing when the time difference information has elapsed after receiving the pointer signal in the second frequency band. To do.

  According to the access point, the wireless terminal, the program, and the method of the present invention, it is possible to control the beacon standby so that the standby time is relatively short with relatively small power consumption.

1 is a system configuration diagram including a wireless terminal and an access point. It is a sequence diagram based on an active scan system. It is a sequence diagram based on a passive scan system. It is a sequence diagram in the present invention. It is a 1st function block diagram of the access point in this invention. It is a 2nd function block diagram of the access point in this invention. It is a function block diagram of the radio | wireless terminal in this invention. It is a sequence diagram between a some access point and a radio | wireless terminal. It is a system block diagram which further has a pointer management server and a base station for wireless WAN communication. It is a function block diagram of the access point which can change a specific channel. It is a system block diagram which inquires about a specific channel using the identifier of the base station for wireless WAN communication. It is a system block diagram which recognizes a specific channel using the control signal from the base station for wireless WAN communication. It is a system block diagram showing the update of the specific channel based on movement of a radio | wireless terminal. It is a functional block diagram of the radio | wireless terminal updated automatically by inquiring a specific channel via radio | wireless WAN communication.

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

  FIG. 4 is a sequence diagram in the present invention.

  According to FIG. 4, the access point 1 and the wireless terminal 2 communicate with each other via radio. Here, at least two frequency bands are used between the access point 1 and the wireless terminal 2. At least one frequency band (first frequency band) is based on a wireless LAN (infrastructure mode) based on IEEE802.11, and a use channel for transmitting and receiving user data is established. The other frequency band (second frequency band) transmits and receives the “pointer signal” of the present invention, and may or may not be based on a wireless LAN.

  The “pointer signal” is a control signal including “used channel information” and “SSID (Service Set ID, network identifier)” in the first frequency band. The wireless terminal 2 can immediately know the channel used in the first frequency band by receiving the pointer signal via the second frequency band.

  FIG. 4A shows an application of the active scan method as in FIG. 2 described above. The access point 1 always broadcasts a pointer signal using the second frequency band. The wireless terminal 2 that has received the pointer signal here knows the used channel information and the SSID in the first frequency band. After that, it is the same as the existing active scan method. The wireless terminal 2 transmits a probe request using the first frequency band and receives a probe response from the access point 1. As a result, the wireless terminal 2 can find the access point 1 for connection in the first frequency band and execute a connection sequence with the access point 1.

  FIG. 4B shows an application of the passive scan method as in FIG. 3 described above. The access point 1 always broadcasts a pointer signal using the second frequency band. The wireless terminal 2 that has received the pointer signal here knows the used channel information and the SSID in the first frequency band. After that, it is the same as the existing passive scan method. The wireless terminal 2 waits for reception of a beacon using the first frequency band. By receiving the beacon from the access point 1, the wireless terminal 2 can discover the access point 1 for connection in the first frequency band and execute a connection sequence with the access point 1.

  FIG. 5 is a first functional configuration diagram of the access point in the present invention.

  The access point 1 includes, as hardware, two antennas 121 and 122 that wirelessly communicate with the wireless terminal 2, a first modem unit 131 connected to the antenna 121, and a second modem unit 132 connected to the antenna 122. And an access network side communication interface 14. The antenna 121 and the first modulation / demodulation unit 131 correspond to the first frequency band, and are based on at least the IEEE802.11 communication method. The antenna 122 and the second modulation / demodulation unit 132 correspond to the second frequency band, and may be based on the IEEE802.11 communication method or not. The first modem unit 131 and the second modem unit 132 may share one antenna by separating two frequency bands using a bandpass filter or the like.

  The access point 1 includes a wireless LAN communication unit 101, a probe response reply unit 102, a beacon transmission unit 103, a pointer signal communication unit 111, a pointer signal generation unit 112, and a time difference calculation unit 113. These functional components are realized by executing a program that causes a computer mounted on the access point to function.

[Wireless LAN communication unit 101]
The wireless LAN communication unit 101 executes protocol control based on IEEE802.11 between the first modem unit 131 and the access network side communication interface 14. That is, the wireless LAN communication unit 101 communicates with the wireless terminal 2 using a predetermined use channel in the first frequency band of the wireless LAN. When the wireless LAN communication unit 101 detects a probe request based on the active scan method, the wireless LAN communication unit 101 outputs a message to that effect to the probe response reply unit 102. Further, the wireless LAN communication unit 101 transmits the probe response output from the probe response return unit 102 and the beacon output from the beacon transmission unit 103 to the wireless terminal 2.

  When the probe response reply unit 102 receives a probe request based on the active scan method, the probe response reply unit 102 outputs the probe response to the wireless LAN communication unit 101 so as to return a probe response to the wireless terminal 2. Specifically, the MAC address of the wireless terminal 2 that is the source of the probe request is included as the destination MAC address of the probe response. The probe response reply unit 102 returns a probe response when the connection-target SSID included in the received probe request matches the SSID of the access point 1. Even if the received probe request does not include an SSID, a probe response is returned. The probe response includes the SSID of the access point 1 concerned. The probe response is transmitted from the antenna 121 via the wireless LAN communication unit 101 and the first modulation / demodulation unit 131 by CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance).

  The beacon transmission unit 103 broadcasts a beacon based on the passive scan method. The beacon includes at least the SSID of the access point 1. The beacon is periodically transmitted from the antenna 121 via the wireless LAN communication unit 101 and the first modulation / demodulation unit 131 by the CSMA / CA method about every 100 ms.

[Pointer signal generator 112]
The pointer signal generation unit 112 generates a pointer signal including used channel information and SSID in the first frequency band. The pointer signal is not limited to the use channel and SSID of the access point itself, but may include use channel information and SSID of other access points. The generated pointer signal is output to the pointer signal communication unit 111.

[Pointer signal communication unit 111]
The pointer signal communication unit 111 transmits the pointer signal to the wireless terminal 2 via the second modulation / demodulation unit 132 and the antenna 122 using a specific channel in the second frequency band. Similarly to the beacon, the pointer signal is also transmitted by the CSMA / CA method periodically about every 100 ms.

[Time difference calculation unit 113]
The access point 1 may optionally further include a time difference calculation unit 113. The time difference calculation unit 113 calculates time difference information from the current time to the next beacon transmission time in the used channel. The calculated time difference information is output to the pointer signal generation unit 112. When the point signal generation unit 112 includes the time difference information in the pointer signal, the time difference information is transmitted to the wireless terminal 2. Thereby, the wireless terminal 2 can know the timing to wait for the next beacon reception in the used channel.

  FIG. 6 is a second functional configuration diagram of the access point in the present invention.

  According to FIG. 6, compared with FIG. 5, two frequency bands in the wireless LAN are used. The first frequency band is a 5 GHz band (or 2.4 GHz band) based on IEEE 802.11, and the second frequency band is a 2.4 GHz band (or 5 GHz band) based on IEEE 802.11. Therefore, it is not necessary to use a separate radio carrier for transmitting the pointer signal. According to FIG. 6, the pointer signal generation unit 112 transmits the pointer signal to the wireless terminal 2 via the second wireless LAN communication unit. Of course, the pointer signal generation unit 112 may transmit the pointer signal to the wireless terminal 2 by another communication method for transmitting and receiving user data.

  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. According to FIG. 6, the access point 1 transmits a pointer signal to the wireless terminal 2 in the 2.4 GHz band, so that the wireless terminal 2 can recognize the channel used in the 5 GHz band. As a result, it is possible to shorten the time until the wireless terminal 2 executes the connection sequence using the 5 GHz band use channel in the access point 1.

  According to FIG. 6, the access point 1 includes two wireless LAN communication units, but may of course include three or more. At this time, the pointer signal may include used channel information and SSID (and time difference information) for each wireless LAN communication unit.

  5 and 6, the pointer signal generation unit 112 has been described as transmitting the pointer signal to the wireless terminal 2 periodically. However, as with the active scan method in the wireless LAN, the pointer signal generation unit 112 transmits the pointer signal from the wireless terminal 2. When a pointer request is received, a pointer signal may be transmitted. That is, the access point 1 periodically transmits a pointer signal or transmits a pointer signal when a pointer request for the access point 1 is received from the wireless terminal 2. On the other hand, the wireless terminal 2 always waits for reception of a pointer signal or waits for reception of a pointer signal after transmitting a pointer request to the access point 1.

  FIG. 7 is a functional configuration diagram of the wireless terminal according to the present invention.

  According to FIG. 7, the wireless terminal 2 includes, as hardware, two antennas 221 and 222 that wirelessly communicate with the access point 1, a first modulation / demodulation unit 231 that is connected to the antenna 221, and a second antenna that is connected to the antenna 222. 2 modulation / demodulation units 232. The antenna 221 and the first modem unit 231 correspond to the first frequency band of the access point 1, and the antenna 222 and the second modem unit 232 correspond to the second frequency band of the access point 1. Is. The first modem 231 and the second modem 232 may share one antenna by separating two frequency bands using a bandpass filter or the like.

  Further, the wireless terminal 2 includes a wireless LAN communication unit 201, a probe request transmission unit 202, a beacon standby unit 203, a pointer signal communication unit 211, a specific channel storage unit 212, a reception standby control unit 213, data And a transmission / reception application 24. These functional components are realized by executing a program that causes a computer installed in the wireless terminal to function.

  The wireless LAN communication unit 201 executes protocol control based on IEEE802.11 between the first modem unit 231 and the application 24. The probe request transmission unit 202 transmits a probe request based on the active scan method and receives a probe response from the wireless terminal 2 by the wireless LAN communication unit 101. The beacon standby unit 203 controls to wait for a beacon based on the passive scan method.

[Specific channel storage unit 212]
The specific channel storage unit 212 stores a specific channel of the pointer signal in advance. That is, the frequency channel of the pointer signal is known to the wireless terminal 2. The specific channel storage unit 212 preferably stores an expiration date for each specific channel information.

[Pointer signal communication unit 211]
The pointer signal communication unit 211 receives the pointer signal via the specific channel in the second frequency band stored in the specific channel storage unit 212. The pointer signal communication unit 211 does not receive a pointer signal in a specific channel for which the expiration date has passed.

  The wireless terminal 2 only needs to detect a pointer signal transmitted only on a specific channel. This is because the access point 1 periodically transmits a pointer signal through the specific channel. The wireless terminal of the prior art has to search for access points in all frequency channels because it is unknown which frequency channel the access point can connect to. That is, the wireless terminal needs to search while switching the channel used by the wireless LAN communication unit. On the other hand, the wireless terminal 2 of the present invention does not require such processing.

[Reception standby control unit 213]
The reception standby control unit 213 controls to wait for a beacon from a connection target access point in the first frequency band or a probe response after transmitting a probe request based on the used channel information and the SSID included in the pointer signal. To do.

  Further, when receiving the pointer signal, the reception standby control unit 213 can know the used channel information and the SSID, so that it can determine whether the wireless terminal 2 is the SSID that is the connection purpose. If the SSID is not for connection, the pointer signal is ignored and discarded. If the SSID is intended for connection, the beacon reception can be awaited by switching the wireless LAN communication unit and modulation / demodulation unit to the channel used. Alternatively, the probe request can be transmitted to the access point 1 through the use channel and the probe response can be received.

  Furthermore, if the reception standby control unit 213 waits for a pointer signal through a specific channel for a predetermined time and cannot receive the pointer signal, the reception standby control unit 213 suppresses the energy consumption by shifting to the sleep mode. You can also Further, after a predetermined time elapses, it is possible to return from the sleep mode and operate again to wait for a pointer signal.

  Further, when the time difference information is included in the pointer signal, the reception standby control unit 213 waits for the beacon sense of the used channel at the timing when the time difference elapses after the pointer signal is received (described later). (See FIG. 8). Other than the timing, the amount of energy consumption can be reduced by shifting the wireless terminal 2 to the sleep state.

  Further, the reception standby control unit 213 includes the shortest time difference information until the next beacon when the pointer signal includes a plurality of sets of used channel information and SSID and time difference information is associated with each set. In order from the used channel, control is performed to wait for the sense of the beacon of the used channel (see FIG. 8 described later). As a result, even if there are a plurality of connection-purpose access points, all beacons can be received as efficiently as possible in the shortest possible time.

  Furthermore, the reception standby control unit 213 performs control so that beacons of all channels in the first frequency band are sensed when the expiration date of the specific channel information in the area has elapsed.

[Time until discovery of access point for connection]
Transmission cycle of pointer signal from access point = every 100 ms. Transmission cycle of beacon from access point = every 100 ms. According to the prior art, the calculation is performed as follows.
Search time for all used channels = maximum 2,095 ms
Average time to find an access point for connection = 2,095 ms ÷ 2 = 1047.5 ms
On the other hand, according to the present invention, the calculation is as follows.
Maximum time to find an access point for connection = 100 ms + 100 ms = 200 ms
In the present invention, when a pointer request and a probe request are used, if each response is made in 5 ms from the access point, 5 ms + 5 ms = 10 ms.

[Time until connection point cannot be found]
According to the prior art, the time for searching all the used channels (maximum 2,095 ms) has to keep the wireless LAN communication function activated.
On the other hand, according to the present invention, when the pointer signal communication unit is activated for 100 ms and the pointer signal cannot be received from the access point to be connected during that time, the mode can be shifted to the sleep mode. Alternatively, the wireless terminal can receive a pointer signal by transmitting a pointer request to the access point, and in this case as well, can shift to the sleep mode in about 15 ms. This is also effective from the viewpoint of energy consumption in the wireless terminal.

  Further, when the wireless terminal 2 cannot receive the pointer signal from the access point 1 of the SSID to be connected, the probe request is not transmitted thereafter. Further, since the wireless terminal 2 transmits the probe request only on the channel used in the access point 1 for connection in the received pointer signal, the wireless terminal 2 is prevented from congesting the wireless environment due to useless probe requests and probe responses. Is done.

[Specific channel setting for pointer signal]
In the 2.4 GHz band in the wireless LAN, for example, setting from 1 channel to 13 channels is possible. However, if setting is made so as not to cause interchannel interference, only three channels such as channels 1, 6, and 11 can be set. Therefore, according to the present invention, when the 2.4 GHz band is used for the specific channel of the pointer signal, for example, any one of channels 1, 6, and 11 is used. Since the pointer signal includes use channel information and SSID in the 5 GHz band, the wireless terminal 2 receives the pointer signal only in the 1, 6, and 11 channels of the 2.4 GHz band, thereby enabling the 5 GHz band. The channel used by the access point can be known.

[Reduction of energy consumption]
According to the prior art, it is assumed that the wireless terminal performs active scan on all 13 channels in the 2.4 GHz band and passive scan on all 19 channels in the 5 GHz band with respect to the access point. In this case, the amount of energy consumed in scanning of all channels is calculated as follows.
680μJ × 13ch + 4,000μJ × 19ch = 84,840μJ
On the other hand, according to the present invention, since it takes 100 ms for standby reception of the pointer and 100 ms for standby reception of the beacon, the energy consumption amount is calculated as follows.
40mW × 200ms = 8,000μJ
When thinking so, the amount of energy consumption of the present invention is one-tenth compared with the prior art.

Further, when the wireless terminal waits for a pointer signal in the active method, the calculation is performed as follows.
Pointer request data size = 300 bytes (assumed: same as probe request)
Pointer signal standby time = 15 ms
In this case, only the energy amount 680 μJ per channel of the active method is further consumed. It can be understood that when there is no access point of SSID for connection purpose and all channels are scanned, the energy consumption is extremely reduced as compared with the amount of energy consumption of 84,840 μJ in the prior art.

  FIG. 8 is a sequence diagram between a plurality of access points and wireless terminals.

According to FIG. 8, it is assumed that there are three access points AP1, AP2, AP3 around the wireless terminal 2, for example. Each access point transmits a pointer signal every 100 ms via the specific channel CH-X. In this case, even if the wireless terminal 2 waits for the channel CH-X pointer signal at an arbitrary timing, the wireless terminal 2 can receive pointer signals from all access points of AP1, AP2, and AP3 at a time interval of 100 ms. .
(Access point) (Channel used) (SSID)
AP1 CH-A ID-AP1
AP2 CH-B ID-AP2
AP3 CH-C ID-AP3
Further, it is assumed that the SSIDs of the access points to be connected to the wireless terminal 2 are ID-AP2 and ID-AP3. At this time, the wireless terminal 2 can receive beacons from the access points AP2 and AP3 by switching the frequency channel and receiving signals as shown in FIG. The reception waiting time of the pointer signal is 100 ms for each of the frequency channels CH-B and CH-C. However, at the timing when the beacon is received, it is possible to switch to the standby for the beacon in the next used channel. Since the beacon is transmitted every 100 ms, the total signal reception waiting time in the channels CH-X, CH-B, and CH-C is 300 ms at maximum.

  Here, when the pointer signal includes “time difference information” up to the next beacon transmission time, it is also preferable to change the switching order of the used channels from beacons with shorter time difference information. For example, according to FIG. 8, it means that the time difference information of the CH-B beacon is shorter than the time difference information of the CH-C beacon. Conversely, if the CH-C beacon time difference information is shorter than the CH-B beacon time difference information, reception of the CH-C beacon is waited first.

Thus, according to the present invention, even when the passive method is used, the search for an access point can be completed in a maximum of 200 ms as follows.
Pointer signal reception waiting time = 100 ms
Beacon reception waiting time = 100 ms
100ms + 100ms = 200ms
When there is a time difference (up to 100 ms) until the beacon transmission timing from the access point, the amount of energy consumption can be reduced by shifting to the sleep mode during that time. Further, by applying the active method to the pointer signal (pointer request transmission) and the probe response (probe request transmission), the access point search time can be further shortened.

[Recognition of specific channel of pointer signal in wireless terminal]
The wireless terminal stores in advance a specific channel of the pointer signal. For example, the specific channel of the pointer signal may be uniquely determined by the communication carrier that has installed the access point and set in each wireless terminal 2. For example, it can be set by the user himself or by a control signal from the carrier.

  However, the access point may have to change the specific channel of the pointer signal. In such a case, since the wireless terminal 2 cannot receive a pointer signal depending on a predetermined specific channel, the wireless terminal 2 recognizes that there is no access point for connection in the vicinity. In order to prevent this, the wireless terminal 2 shifts to the normal scan operation when the pointer signal cannot be received even after waiting for the reception of the pointer signal continuously for a predetermined number of times (N times).

  Assuming that the wireless terminal 2 shifts to such a normal scan, the access point sends a second frequency to the beacon or probe response transmitted using each channel used in the first frequency band of the wireless LAN. It is also preferable to include specific channel information of the pointer signal in the band. When the wireless terminal 2 fails to receive the pointer signal of the specific channel for a predetermined number of times or for a predetermined time, the wireless terminal 2 shifts from the pointer signal scan to the normal scan and senses the beacons of all the channels in the first frequency band.

  When the wireless terminal 2 finds an access point for connection, the wireless terminal 2 updates the specific channel storage unit with the specific channel information included in the beacon received from the access point or the probe response after transmitting the probe request. Thus, from the next time, it is possible to immediately search for an access point to be connected by a pointer signal scan. Note that if a connection-purpose access point cannot be found, the previously stored specific channel is not updated.

  Thus, even if the pointer signal scan fails N times, the pointer signal scan succeeds again after executing the normal scan.

  FIG. 9 is a system configuration diagram further including a pointer management server and a wireless WAN communication base station.

  According to the system of FIG. 9, the pointer management server 3 that can communicate with the access point 1 and the wireless terminal 2 via the network is further arranged. The “pointer management server” 3 stores position information and a specific channel for each access point.

  Here, the access point 1 may detect a state where the specific channel cannot be used. According to the wireless LAN 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, the wireless terminal 2 cannot use active scan as a method for confirming the presence of the access point 1. As a result, in order to connect to the access point, the wireless terminal 2 must monitor the frequency channel and search for a beacon for all the channels transmitted from the access point 1, which takes time. There was a problem. Therefore, when the pointer signal is transmitted on a specific channel in the 5 GHz band, the access point 1 detects the interference wave from the radar or the like in order to change the specific channel to another specific channel. Transmit to the management server 3.

  On the other hand, when receiving the change of the specific channel from the access point 1, the pointer management server 3 instructs the access point located within a predetermined range from the access point to change to another specific channel. . That is, the specific channel of the pointer signal is set in common in a predetermined range area. According to FIG. 9, a plurality of access points located in a predetermined range are instructed to change the specific channel from CH-X to CH-Y.

  Further, according to FIG. 9, the wireless terminal 2 sends an “inquiry request” (request) including the network identifier of the access point to be connected to the pointer management server 3 in order to acquire a specific channel for receiving the pointer signal. Send to. In response to this, the pointer management server 3 returns an “inquiry response” (response) including specific channel information of the pointer signal of the access point corresponding to the network identifier to the wireless terminal 2. Thereby, the wireless terminal 2 can know the specific channel in which the pointer signal is updated.

  FIG. 10 is a functional configuration diagram of an access point capable of changing a specific channel.

  10 includes a specific channel change detection unit 114 and a specific channel change reception unit 115, as compared with FIG. When the specific channel change detection unit 114 detects an interference wave for the specific channel of the second modem unit 132, the specific channel change detection unit 114 transmits the specific channel to the pointer management server 3 to change the specific channel to another specific channel. The specific channel change receiving unit 115 sets the updated specific channel received from the pointer management server 3 in the second modem unit 132.

  FIG. 11 is a system configuration diagram in which a specific channel is inquired using an identifier of a base station of a wireless WAN communication network.

  11, compared with FIG. 9, the base station 4 of the wireless WAN communication network is arranged, and the wireless terminal 2 can communicate with the base station 4 via the wireless WAN (Wide Area Network). . The wireless WAN may be 3G, WiMAX, or LTE, for example. Further, the base station 4 includes its own base station ID (identifier) in the “control signal” and broadcasts it to the wireless terminal 2.

  The wireless terminal 2 transmits an inquiry request (request) including the base station ID to the pointer management server 3 via the base station 4. On the other hand, the pointer management server 3 returns an inquiry response (response) including the specific channel information of the pointer signal of the access point around the base station corresponding to the base station ID to the wireless terminal 2. The wireless terminal 2 makes an inquiry request (request) only when the specific channel information is not stored in the specific channel storage unit 212 or when the specific channel information is stored but the expiration date has expired. May be transmitted to the pointer management server 3.

  FIG. 12 is a system configuration diagram for recognizing a specific channel using a control signal from a base station of a wireless WAN communication network.

  According to FIG. 12, compared with FIG. 11, the base station 4 acquires specific channel information of the pointer signal of the access point around the base station corresponding to the base station identifier from the pointer management server 3. Then, the base station 4 broadcasts the specific channel information included in the “control signal”. The wireless terminal 2 that has received the control signal can know a specific channel from the access point 1 in the vicinity. According to FIG. 12, the wireless terminal 2 can automatically update the specific channel information in the specific channel storage unit 212 by a control signal that is always broadcast from the base station 4 without inquiring about the specific channel information. .

  FIG. 13 is a system configuration diagram illustrating updating of a specific channel based on movement of a wireless terminal.

  According to FIG. 13, it is assumed that the specific channel storage unit 212 of the wireless terminal 2 further stores the specific channel information in association with the base station ID. In this case, when the wireless terminal 2 moves and the base station ID included in the control signal broadcast from the base station 4 in the area changes, the specific channel storage unit 212 is referred to, and the base station 4 The specific channel information associated with the base station ID is referred to. When the specific channel information associated with the base station ID of the base station 4 does not exist in the specific channel storage unit 212, an inquiry request (request) including the base station ID is transmitted to the pointer management server 3. On the other hand, the pointer management server 3 returns an inquiry response (response) including the specific channel information of the pointer signal of the access point around the base station corresponding to the base station ID to the wireless terminal 2. As a result, the specific channel is also automatically updated. When the base station 4 broadcasts the specific channel information included in the control signal, the specific channel information stored in the specific channel storage unit 212 may be updated without making an inquiry request to the pointer management server 3. preferable.

  FIG. 14 is a functional configuration diagram of a wireless terminal that automatically updates a specific channel.

  14, the wireless WAN antenna 223 and the third modem 233, the specific channel inquiry unit 214, and the wireless WAN communication unit 215 are further provided as compared with FIG. The specific channel inquiry unit 214 transmits an inquiry request (request) including a base station identifier to the pointer management server 3 via the wireless WAN communication unit 215, and receives an inquiry response (response) including specific channel information. Can do. In addition, when the control signal received from the base station 4 includes specific channel information, the wireless WAN communication unit 215 outputs the specific channel information to the specific channel inquiry unit 214. The specific channel information acquired by the specific channel inquiry unit 214 is output to the specific channel storage unit 212.

  As described above in detail, according to the access point, the wireless terminal, the program, and the method of the present invention, the beacon standby is controlled so that the power consumption is relatively small and the standby time is relatively short. can do. In addition, since a useless signal is not transmitted, it can be expected to reduce congestion in the wireless environment.

  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.

DESCRIPTION OF SYMBOLS 1 Access point 101 Wireless LAN communication part 102 Probe response reply part 103 Beacon transmission part 111 Pointer signal communication part 112 Pointer signal generation part 113 Time difference calculation part 114 Specific channel change detection part 115 Specific channel change reception part 121,122 Antenna 131,132 Modulation / demodulation unit 14 Access network side communication interface 2 Wireless terminal 201 Wireless LAN communication unit 202 Probe request transmission unit 203 Beacon standby unit 211 Pointer signal communication unit 212 Specific channel storage unit 213 Reception standby control unit 214 Specific channel inquiry unit 215 Wireless WAN communication Units 221, 222, 223 Antennas 231, 232, 233 Modulator / Demodulator 3 Pointer management server 4 Base station

Claims (12)

In an access point that communicates with a plurality of wireless terminals via a wireless LAN (Local Area Network),
For each wireless terminal, a wireless LAN communication means for communication using each channel used in the first frequency band,
For each wireless terminal, time difference calculating means for calculating time difference information from the current time to the next beacon transmission time in the used channel;
Pointer signal generating means for generating a pointer signal including channel information and network identifier used in the first frequency band and the time difference information for each wireless terminal ;
To a plurality of mobile stations, said pointer signals, and a pointer signal communication means to send using only one particular channel in the second frequency band,
An access point that causes each wireless terminal to wait for a beacon of the channel in use in the first frequency band at a timing when the time of the time difference information elapses after receiving the pointer signal. The first frequency band is a 5 GHz band or a 2.4 GHz band based on IEEE802.11.
The access point according to claim 1, wherein the second frequency band is a 2.4 GHz band or a 5 GHz band based on IEEE802.11. The pointer signal generation means includes a plurality of sets of used channel information and network identifiers and the time difference information in the pointer signal, and associates time difference information with each set,
3. The access point according to claim 1, wherein the wireless terminal is made to wait for a beacon of the use channel in order from the use channel with the shortest time difference information until the next beacon. The pointer signal communication means has a passive method for periodically transmitting the pointer signal or an active method for transmitting the pointer signal when a pointer request for the access point is received from the wireless terminal. The access point according to any one of claims 1 to 3. In a wireless terminal that communicates with an access point via a wireless LAN,
Specific channel storage means for previously storing one specific channel of a pointer signal in the second frequency band for a plurality of access points ;
Wireless LAN communication means for communicating with an access point using a predetermined use channel in the first frequency band;
Using the specific channel of the second frequency band, a pointer signal including the used channel information and network identifier in the first frequency band, and time difference information from the current time to the next beacon transmission time in the used channel Pointer signal receiving means for receiving
The wireless LAN communication means, at the timing when the time difference information has elapsed after the reception of the pointer signal, based on the used channel information and the network identifier included in the pointer signal, for the purpose of connection in the first frequency band A wireless terminal that waits for a beacon from an access point or a probe response after transmitting a probe request.   6. The wireless LAN communication unit shifts to a sleep state based on the time difference information included in the pointer signal until the time difference elapses after reception of the pointer signal. Wireless terminal. The first frequency band is a 5 GHz band or a 2.4 GHz band based on IEEE802.11.
The wireless terminal according to claim 5 or 6, wherein the second frequency band is a 2.4 GHz band or a 5 GHz band based on IEEE802.11. The pointer signal includes a plurality of sets of channel information and network identifiers and time difference information, and time difference information is associated with each set,
The wireless terminal according to any one of claims 5 to 7, wherein the wireless LAN communication unit waits for a beacon of the use channel in order from the use channel with the shortest time difference information until the next beacon. 9. The pointer signal receiving unit according to claim 5, wherein the pointer signal receiving unit has a passive system that waits for the pointer signal or an active system that waits for the pointer signal after transmitting a pointer request to the access point. The wireless terminal according to item 1. In a program for causing a computer mounted on an access point to communicate with a plurality of wireless terminals via a wireless LAN,
For each wireless terminal, a wireless LAN communication means for communication using each channel used in the first frequency band,
For each wireless terminal, time difference calculating means for calculating time difference information from the current time to the next beacon transmission time in the used channel;
Pointer signal generating means for generating a pointer signal including channel information and network identifier used in the first frequency band and the time difference information for each wireless terminal ;
To a plurality of mobile stations, said pointer signals, cause the computer to function as a pointer signal communication means to send using only one particular channel in the second frequency band,
A program for an access point, which causes each wireless terminal to wait for a beacon of the channel in use in the first frequency band at a timing when the time difference information passes after receiving the pointer signal. In a program for functioning a computer mounted on a wireless terminal that communicates with an access point via a wireless LAN,
Specific channel storage means for previously storing one specific channel of a pointer signal in the second frequency band for a plurality of access points ;
Wireless LAN communication means for communicating with an access point using a predetermined use channel in the first frequency band;
Using the specific channel of the second frequency band, a pointer signal including the used channel information and network identifier in the first frequency band, and time difference information from the current time to the next beacon transmission time in the used channel The computer functions as a pointer signal receiving means for receiving
The wireless LAN communication means, at the timing when the time difference information has elapsed after the reception of the pointer signal, based on the used channel information and the network identifier included in the pointer signal, for the purpose of connection in the first frequency band A program for a wireless terminal, which causes a computer to wait for a beacon from an access point or a probe response after transmitting a probe request. In an access point discovery method in which a wireless terminal discovers an access point via a wireless LAN,
The plurality of wireless terminals and the plurality of access points store one specific channel of the pointer signal in the second frequency band in advance,
Each and each wireless terminal and the access point, which communicates with a predetermined channel used in the first frequency band,
Using the specific channel of the second frequency band, the access point uses channel information and network identifier in the first frequency band, and time difference information from the current time to the next beacon transmission time in the used channel A first step of transmitting a pointer signal including: to the wireless terminal;
A second step of waiting for a beacon of the channel in use in the first frequency band at a timing when the time difference information has elapsed after receiving the pointer signal in the second frequency band; An access point discovery method characterized by:

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