JP2020028019A - Communication device and computer program therefor - Google Patents

Abstract

To provide a technique for a communication device to properly establish a wireless connection with a target access point.SOLUTION: A communication device executes normal standby processing via a wireless interface that can use two or more channels. The normal standby processing is processing for standing ready to receive a beacon signal from a target access point by sequentially using each of two or more channels. When a beacon signal is received from a different access point by using a specific channel in the normal standby processing, the communication device executes additional standby processing in addition to the normal standby processing. The additional standby processing is processing for standing ready to receive a beacon signal from the target access point by using the specific channel for a second time. The communication device establishes a wireless connection with the target access point, when a beacon signal is received from the target access point in the standby processing.SELECTED DRAWING: Figure 6

Description

  This specification discloses a technology related to a communication device that establishes a wireless connection with an access point.

  Patent Literature 1 discloses an access point that can use a DFS (Dynamic Frequency Selection) channel. At startup, the access point executes CAC (abbreviation for Channel Availability Check) using the DFS channel and monitors whether or not to receive radar using the DFS channel. Performing CAC is defined by standards. The access point transmits a beacon when it does not receive radar in CAC. The client performs a passive scan of the DFS channel by sequentially switching channels and waiting for a beacon transmitted from the access point.

JP 2017-63408 A

IEEE Standards 802.11h 2003

  The above technique does not assume a situation in which a plurality of access points exist around a client. In such a situation, each of the plurality of access points may transmit a beacon using the same channel. In this case, the client may not be able to receive a beacon from the target access point to establish a wireless connection, and as a result, may not be able to establish a wireless connection with the target access point. In the present embodiment, a technique is provided for a communication apparatus to appropriately establish a wireless connection with a target access point.

  The communication device disclosed in this specification is a wireless interface that can use two or more channels, and a normal standby unit that executes a normal standby process via the wireless interface, wherein the normal standby process is Waiting for receiving a beacon signal from a target access point by sequentially using each of the two or more channels over a first time, wherein the target access point is The normal standby unit, which is a target access point to which a connection is to be established, and an access different from the target access point using the specific channel among the two or more channels in the normal standby process. When a beacon signal is received from a point, the additional standby unit performs an additional standby process in addition to the normal standby process. The additional standby process is a process of using the specific channel for a second time to wait for receiving a beacon signal from the target access point, the additional standby unit, An establishing unit configured to establish a wireless connection with the target access point via the wireless interface when a beacon signal is received from the target access point in the normal standby process or the additional standby process.

  According to such a configuration, in a normal standby process, the communication device executes an additional standby process when a beacon signal is received from an access point different from the target access point using a specific channel. . For this reason, the communication device can wait to receive a beacon signal from the target access point in an additional standby process in addition to the normal standby process. As a result, the probability of receiving a beacon signal from the target access point can be increased as compared to a configuration in which only a normal standby process is performed. As a result, a beacon signal can be appropriately received from the target access point. The wireless connection with the target access point can be appropriately established.

  A computer program for realizing the above communication device and a computer-readable recording medium for storing the computer program are also novel and useful. Further, the method executed by the above communication device is also new and useful.

1 shows a configuration of a communication system. 4 shows a flowchart of a connection process. 5 shows a flowchart of an active scan of W52. 5 shows a flowchart of a first passive scan of W53. 5 shows a flowchart of a second passive scan of W53 according to the first embodiment. FIG. 4 shows a sequence diagram of a specific case of the first embodiment. 13 shows a flowchart of a second passive scan of W53 according to the second embodiment. FIG. 8 shows a sequence diagram of a specific case of the second embodiment. 13 shows a flowchart of a second passive scan of W53 according to the third embodiment. FIG. 10 shows a sequence diagram of a specific case of the third embodiment.

(Configuration of communication system 2; FIG. 1)
As shown in FIG. 1, the communication system 2 includes a printer 10, two access points 100 and 200, and a terminal device 500. Each of the devices 10, 100, 200, and 500 can execute wireless communication according to the Wi-Fi scheme. In the following, the “access point” is referred to as “AP (short for Access Point)”. The terminal device 500 is a device such as a desktop PC (abbreviation of Personal Computer), a notebook PC, a tablet PC, a mobile terminal, and the like.

(Configuration of APs 100 and 200)
The AP 100 is a normal AP called a wireless AP, a wireless LAN router, or the like. The AP 100 performs wireless communication according to the Wi-Fi scheme. The Wi-Fi method is based on, for example, the 802.11 standard of IEEE (abbreviation of the Institute of Electrical and Electronics Engineers, Inc.) and the standard corresponding thereto (eg, 802.11a, 11b, 11g, 11n, etc.) This is a wireless communication method for executing wireless communication. In particular, the AP 100 can execute processing related to DFS (abbreviation of Dynamic Frequency Selection) defined by the standard of IEEE Standards 802.11h. This allows the AP 100 to use a carrier having a frequency of 5.0 GHz, particularly a carrier having the same frequency as that used for weather radar, military radar, and the like.

  The frequency of 5.0 GHz is classified into a plurality of frequency bands. Each frequency band is generally called a "channel." For example, a frequency of 5.150 GHz to 5.250 GHz is classified into four channels of 36 to 48 channels. Hereinafter, the “channel” may be described as “ch (abbreviation of Channel)”. In addition, frequencies from 5.250 GHz to 5.350 GHz are classified into four channels of 52 channels to 64 channels. Here, 36ch to 48ch are called "W52", and 52ch to 64ch are called "W53".

  The frequency band (that is, channel) classified as W53 includes a frequency used for a weather radar or the like. When using the channel of W53, the AP 100 executes CAC (abbreviation of Channel Availability Check) in accordance with the DFS standard. In CAC, when the channel of W53 is determined as a channel to be used, the AP 100 monitors, for 60 seconds, whether to detect a radar having a frequency included in the determined channel. Then, when the radar is not detected for 60 seconds, the AP 100 transmits a beacon signal using the determined channel to the broadcast. Thus, while avoiding interference between the radar and the carrier, a wireless LAN connection is established with the communication device (for example, the printer 10) that has received the beacon signal using the channel of W53, and the communication device is connected to the AP 100. Can participate in a wireless network formed by On the other hand, when the radar using the determined channel is detected, the AP 100 determines another channel as the channel to be used and executes the CAC again.

  The frequency band (that is, channel) classified as W52 is not used for weather radar and the like. Therefore, the AP 100 does not execute the CAC when using the channel of W52. Hereinafter, a channel classified as W53 is referred to as a “DFS channel”, and a channel classified as W52 is referred to as a “non-DFS channel”.

  In a situation where a wireless LAN connection using a certain DFS channel has been established with a communication device, the AP 100 detects a radar having the same frequency as the frequency included in the DFS channel being used. , The use of the DFS channel being used is stopped. Then, when stopping the use of the DFS channel being used, the AP 100 transmits a switching signal to the communication device, and starts a switching process for switching to a channel different from the DFS channel being used. The switching signal is a signal for notifying the communication device of switching from the DFS channel being used to a different channel. Note that the switching signal is also transmitted when another AP using the same channel as that used by the AP 100 is present around the AP 100. Specifically, the AP 100 sends a switching signal to the printer 10 when a number of beacon signals equal to or greater than the threshold are received by the AP 100 due to a plurality of other APs transmitting beacon signals. A switching process for switching to a channel different from the channel being used for transmission is started. By switching to a different channel, interference between wireless communication performed by the AP 100 and wireless communication performed by another AP (ie, line congestion) can be avoided.

  When the switched channel is the DFS channel, the timing at which the beacon signal using the switched channel is transmitted differs depending on the performance of the AP 100. For example, when the AP 100 is an AP that cannot simultaneously execute wireless communication and CAC, the AP 100 executes CAC after transmitting the switching signal. Then, the AP 100 performs a switching process after the CAC, and transmits a beacon signal. Therefore, the beacon signal is transmitted at least 60 seconds after the transmission of the switching signal. On the other hand, if the AP 100 is an AP that can simultaneously execute wireless communication and CAC, the AP 100 can execute CAC using the switched channel before radar detection. Therefore, the AP 100 can transmit the beacon signal before 60 seconds have elapsed since the transmission of the switching signal.

  Further, the AP 100 stores an SSID (abbreviation of Service Set Identifier) “XXX” for identifying a wireless network formed by the AP 100. Similarly, the AP 200 stores the SSID “YYY”.

(Configuration of Printer 10)
The printer 10 is a peripheral device that can execute a printing function (that is, a peripheral device such as the terminal device 500). The printer 10 includes a wireless LAN interface 14 and a control unit 20. Each of the units 14 to 20 is connected to a bus line (reference numerals are omitted). Hereinafter, the interface is described as “I / F”.

  The wireless LAN I / F 14 is an I / F for executing wireless communication according to the Wi-Fi method. The wireless LAN I / F 14 can execute wireless communication using channels W52 and W53. As shown in FIG. 1, the printer 10 establishes a wireless LAN connection with the AP 100 via the wireless LAN I / F 14 and participates in a wireless network formed by the AP 100. The terminal device 500 also participates in the wireless network formed by the AP 100. Thereby, the printer 10 can receive the print data from the terminal device 500 participating in the wireless network via the AP 100 and execute printing in accordance with the print data.

  The control unit 20 includes a CPU 22 and a memory 24. The CPU 22 executes various processes according to the program 30 stored in the memory 24. The memory 24 includes a volatile memory, a nonvolatile memory, and the like. The memory 24 further stores a flag table 32 and AP information 34. The AP information 34 includes an SSID “XXX” for identifying a wireless network in which the printer 10 is currently participating, and a password for participating in the wireless network.

  The flag table 32 is a table that stores, for each of the four channels of W53, a channel number indicating the channel, a flag, and the number information in association with each other. The flag is “1” indicating that a beacon signal including an SSID different from the SSID “XXX” in the AP information 34 has been received, and “0” indicating that a beacon signal including the different SSID has not been received. , Indicates one of the following values: The initial value of the flag is “0”. The flag is changed from “0” to “1” when another beacon signal including an SSID different from the SSID “XXX” in the AP information 34 is received in a second W53 passive scan (see FIG. 5) described later. Is changed to The flag is reset to “0” when the connection processing of FIG. 2 described later ends. The number information indicates the number of the other beacon signals.

(Connection process; Fig. 2)
With reference to FIG. 2, the contents of the connection processing executed by the CPU 22 of the printer 10 will be described. The connection process is started by receiving a switching signal from the AP 100 as a trigger in a situation where the printer 10 is participating in a wireless network formed by the AP 100.

  In S10, the CPU 22 determines whether print data is being received from the terminal device 500 via the AP 100 using the wireless LAN connection established with the AP 100. For example, when a part (for example, a packet) of the print data is received from the AP 100 and the remaining part is not received, the CPU 22 determines that the print data is being received. When determining that the print data is not being received (NO in S10), the CPU 22 proceeds to S12.

  In S12, the CPU 22 executes an active scan of W52 described later (see FIG. 3). The CPU 22 proceeds to S14 when the wireless LAN connection is not established in the active scan of W52, and ends the processing in FIG. 2 when the wireless LAN connection is established.

  In S14, the CPU 22 executes a first passive scan of W53 described later (see FIG. 4). When the wireless LAN connection is not established in the first passive scan of W53, the CPU 22 proceeds to S16, and when the wireless LAN connection is established, ends the processing in FIG.

  In S16, the CPU 22 determines whether a predetermined time (for example, 90 seconds) has elapsed after receiving the switching signal. When determining that the predetermined time has not elapsed (NO in S16), the CPU 22 returns to S12. In other words, the CPU 22 repeatedly executes the processing of S12 and S14 until a predetermined time has elapsed. On the other hand, if the CPU 22 determines that the wireless LAN connection has not been established in any of the active scan of W52 and the first passive scan of W53, and the predetermined time has elapsed (NO in S16), the process proceeds to S30.

  In S30, the CPU 22 displays an error screen on a display unit (not shown) of the printer 10. The error screen is a screen indicating that a wireless LAN connection with the AP 100 cannot be established. When S30 ends, the processing in FIG. 2 ends.

  When determining that print data is being received (YES in S10), the CPU 22 proceeds to S20. S20 is the same as S12. If the wireless LAN connection is not established in S20, the CPU 22 proceeds to S22, and if the wireless LAN connection is established, ends the processing in FIG.

  In S22, the CPU 22 executes a second passive scan of W53 described later (see FIG. 5). If the wireless LAN connection is not established in the second passive scan of W53, the CPU 22 proceeds to S24, and if the wireless LAN connection is established, ends the processing in FIG. S24 is the same as S16. When the CPU 22 determines that the wireless LAN connection has not been established in any of the active scan of W52 and the second passive scan of W53 and the predetermined time has elapsed (YES in S24), the process proceeds to S30.

(Active scan of W52; FIG. 3)
The contents of the active scan of W52 will be described with reference to FIG. In S50, the CPU 22 determines 36 channels from among the four channels of W52 (that is, 36 channels, 40 channels, 44 channels, and 48 channels) as channels to be scanned (hereinafter, referred to as “scan channels”).

  In S52, the CPU 22 transmits a probe request including the SSID “XXX” in the AP information 34 to the AP 100 via the wireless LAN I / F 14 using a scan channel. In S54, the CPU 22 determines whether a probe response to the probe request has been received from the AP 100. When determining that the probe response has been received from the AP 100 (YES in S54), the CPU 22 proceeds to S60. For example, when the AP 100 is waiting for a probe request to be received using the scan channel, the printer 10 receives a probe response from the AP 100.

  In S60, the CPU 22 communicates with the AP 100 various signals (for example, an Authentication signal, an Association signal, a 4-way handshake, etc.) for establishing a wireless LAN connection with the AP 100. In the course of communication of the various signals described above, authentication using the password in the AP information 34 is executed between the AP 100 and the printer 10. Thus, the CPU 22 establishes a wireless LAN connection with the AP 100. When S60 ends, the processing in FIG. 3 ends and the processing in FIG. 2 ends.

  If it is determined that a predetermined time (for example, several tens of msec) has elapsed without receiving a probe response from the AP 100 (NO in S54), the process proceeds to S56. For example, when the AP 100 is waiting to receive a probe request using a channel different from the scan channel, the printer 10 cannot receive a probe response from the AP 100. In S56, the CPU 22 determines whether all four channels of W52 have been used as scan channels. When the CPU 22 determines that there is a channel not used as a scan channel among the four channels of W52 (NO in S56), the process proceeds to S58.

  In S58, the CPU 22 changes the scan channel from 36ch to 40ch. The CPU 22 sequentially changes the scan channel and repeats the processing of S52 and S54 until all of the four channels of W52 are used as scan channels. When determining that all of the four channels of W52 have been used as scan channels (YES in S56), the CPU 22 ends the process of FIG. 3 and proceeds to S14 or S22 of FIG.

(First passive scan of W53; FIG. 4)
The contents of the first passive scan of W53 will be described with reference to FIG. In S70, the CPU 22 determines 52ch as a scan channel from the four channels of W53 (ie, 52ch, 56ch, 60ch, 64ch).

  In S74, the CPU 22 waits for a beacon signal to be received from the AP 100 via the wireless LAN I / F 14 using the scan channel for a standby time (for example, 100 msec). In other words, the CPU 22 performs a standby process of using the scan channel for a standby time to wait for an AP (for example, 100) to receive a beacon signal transmitted by broadcasting. Then, when one or more beacon signals are received during the execution of the standby process, the CPU 22 includes, in the received one or more beacon signals, an SSID that matches the SSID “XXX” in the AP information 34. If there is a beacon signal including a beacon signal, it is determined that a beacon signal has been received from the AP 100, otherwise, it is determined that a beacon signal has not been received from the AP 100. When determining that the beacon signal has been received from the AP 100 using the scan channel (YES in S74), the CPU 22 proceeds to S80.

  In S80, the CPU 22 transmits a probe request including the SSID “XXX” to the AP 100 via the wireless LAN I / F 14 using the scan channel. Then, when receiving a probe response to the probe request from the AP 100, the CPU 22 communicates with the AP 100 various signals (for example, an Authentication signal, an Association signal, a 4-way handshake, etc.) for establishing a wireless LAN connection. Thus, the CPU 22 establishes a wireless LAN connection with the AP 100. When S80 ends, the process in FIG. 4 ends and the process in FIG. 2 ends.

  When determining that the beacon signal has not been received from the AP 100 using the scan channel (NO in S74), the CPU 22 determines in S76 whether all four channels of W53 have been used as scan channels. Judge. When the CPU 22 determines that there is a channel not used as a scan channel among the four channels of W53 (NO in S76), the process proceeds to S78.

  In S78, the CPU 22 changes the scan channel from 52ch to 56ch. The CPU 22 sequentially changes the scan channels and repeats the processing of S74 until all of the four channels of W53 are used as scan channels. When determining that all of the four channels of W53 have been used as scan channels (YES in S76), the CPU 22 ends the process of FIG. 4 and proceeds to S16 of FIG.

(Second passive scan of W53; FIG. 5)
The contents of the second passive scan of W53 will be described with reference to FIG. The second passive scan of W53 corresponds to a process in which the processes of S102 to S106, S122, and S124 described later are added to the first passive scan of W53 in FIG.

  Step S100 is the same as step S70 in FIG. In S102, the CPU 22 specifies information (ie, flag and number information) corresponding to the scan channel from the flag table 32. Then, the CPU 22 determines whether or not the specified flag indicates “1”. When determining that the specified flag indicates “0” (NO in S102), the CPU 22 determines the standby time to be 100 msec in S104. The standby time is a time for waiting for reception of a beacon signal in S120 described later.

  When determining that the specified flag indicates “1” (YES in S102), the CPU 22 determines the standby time to be 200 msec or 300 msec in S106. When the number indicated by the specified number information is less than the threshold value of two (that is, one), the CPU 22 determines the standby time to be 200 msec, and the number indicated by the specified number information is two. In the case described above, the standby time is determined to be 300 msec. In the modification, the threshold value may be a value indicating three or more.

  Step S120 is the same as step S74 in FIG. 4 except that the scan channel is used over the standby time corresponding to the processing of steps S102 to S106. When determining that the beacon signal has been received from the AP 100 using the scan channel (YES in S120), the CPU 22 proceeds to S150. Step S150 is the same as step S80 in FIG. When S150 ends, the process in FIG. 5 ends and the process in FIG. 2 ends.

  When the standby time has elapsed without receiving a beacon signal from the AP 100 using the scan channel (NO in S120), the CPU 22 uses the scan channel in S122 to change the AP (for example, the AP 200) using the scan channel. It is determined whether a beacon signal has been received from. Specifically, when one or more beacon signals are received in the process of S120, the CPU 22 does not match the SSID “XXX” in the AP information 34 in the received one or more beacon signals. If there is a beacon signal including the SSID, it is determined that a beacon signal has been received from a different AP. On the other hand, when no beacon signal has been received in S120, the CPU 22 determines that a beacon signal has not been received from a different AP. When determining that the beacon signal has not been received from a different AP using the scan channel (NO in S122), the CPU 22 skips S124 and proceeds to S126. On the other hand, when determining that the beacon signal has been received from a different AP using the scan channel (YES in S120), the CPU 22 proceeds to S124.

  In S124, the CPU 22 changes the flag corresponding to the scan channel in the flag table 32 from “0” to “1”. When the corresponding flag indicates “1”, the flag is maintained at “1”. Further, the CPU 22 stores the number of one or more beacon signals received in S120 in the flag table 32 as number information corresponding to the scan channel.

  Steps S126 and S128 are the same as steps S76 and S78 in FIG. When determining that all of the four channels of W53 have been used as scan channels (YES in S126), the CPU 22 ends the process of FIG. 5 and proceeds to S24 of FIG.

(Specific case; Fig. 6)
A specific case realized by the second passive scan of W53 in FIG. 5 will be described with reference to FIG. In this case, a wireless LAN connection using 52 channels is established between the printer 10 and the AP 100. A wireless LAN connection using 52 channels is established between the terminal device 500 and the AP 100.

  In T100, the printer 10 receives print data from the terminal device 500 via the AP 100. Here, while transmitting the print data received from the terminal device 500 to the printer 10, the AP 100 detects a radar having the same frequency as the frequency included in the 52ch. In this case, the AP 100 transmits a switching signal to the printer 10 at T102, and thereafter stops using the 52ch. Thereby, the wireless LAN connection between the printer 10 and the AP 100 is disconnected. The switching signal is also transmitted to the terminal device 500, and the wireless LAN connection between the terminal device 500 and the AP 100 is disconnected.

  In T104, the AP 100 starts switching processing for switching from 52ch to 60ch. In this case, the AP 100 has already performed CAC using 60 ch before detecting a radar. In T106, the AP 100 completes the switching to the 60ch, and starts broadcasting a beacon signal using the 60ch.

  Further, when the printer 10 receives the switching signal from the AP 100 during the reception of the print data at T102, the printer 10 determines that the print data is being received (YES in S10 of FIG. 2) and performs an active scan of W53 (see FIG. 3). ) And the second passive scan of W53 (see FIG. 5) are repeatedly executed (S20, S22 in FIG. 2).

  As shown in FIG. 6, the printer 10 scans four channels of W52 and four channels of W53 (that is, 52 channels, 56 channels, 60 channels, and 64 channels) in the first process among the repetitive processes. Execute In FIG. 6, illustration of the processing of each of the four channels of W52 is omitted. In the first process, each flag corresponding to each channel of W53 indicates “0”, so the standby time of each channel of W53 is 100 msec (NO in S102 of FIG. 5, S104). In the first process, the APs 100 and 200 do not execute the broadcast transmission of the beacon signal. Since the printer 10 cannot receive the beacon signal from the AP 100 in the first processing (NO in S120 in FIG. 5, YES in S126), the printer 10 executes the second processing (NO in S24 in FIG. 2).

  While the second process is being executed, the AP 200 starts broadcasting a beacon signal using the 60ch. Therefore, the printer 10 receives a beacon signal including the SSID “YYY” from the AP 200 in the standby process using the 60 ch in the second process. Further, while the second process is being executed, the AP 100 starts broadcasting a beacon signal using the 60ch at T106. However, due to the reception of the beacon signal from the AP 200, the printer 10 fails to receive the beacon signal from the AP 100 in the standby process using the channel 60 (NO in S120 in FIG. 5).

  The printer 10 receives the beacon signal including the SSID “YYY” that does not match the SSID “XXX” in the AP information 34 in the standby process using the 60 ch in the second process. It is determined that it has been received (YES in S122 of FIG. 5). Then, the printer 10 changes the flag corresponding to 60ch to “1” (S124). As described above, since the printer 10 cannot receive the beacon signal from the AP 100 in the second processing (NO in S120 in FIG. 5, YES in S126), the printer 10 executes the third processing (NO in S24 in FIG. 2). .

  In the third process, when the printer 10 determines 60ch as the scan channel (S128 in FIG. 5), the flag corresponding to 60ch indicates “1”, so the printer 10 determines the standby time to be 200 msec (YES in S102, S106). ). Then, the printer 10 waits for a beacon signal to be received from the AP 100 using the 60 ch for 200 msec. In other words, in the third process, the printer 10 uses the channel 60 for 100 msec in addition to the standby process of waiting for the beacon signal to be received from the AP 100 using the channel 60 for 100 msec. And performs an additional standby process of waiting for a beacon signal from the AP 100 to be received.

  In this case, the printer 10 receives a beacon signal including the SSID “YYY” from the AP 200 in the previous standby process, and receives a beacon signal including the SSID “XXX” from the AP 100 in the additional standby process. Therefore, in the third process, the printer 10 determines that a beacon signal has been received from the AP 100 (YES in S120 of FIG. 5), and establishes a wireless LAN connection using the 60ch with the AP 100 at T120. (S150). After receiving the switching signal, the terminal device 500 executes a scan using W52 and W53. When receiving a beacon signal using the 60ch from the AP 100, the terminal device 500 establishes a wireless LAN connection using the 60ch with the AP100.

  When a wireless LAN connection using 60ch is established between the printer 10 and the AP 100 and between the terminal device 500 and the AP 100, the printer 10 again receives print data from the terminal device 500 via the AP 100. I do. Thereby, the printer 10 can execute printing according to the print data.

(Effects of the present embodiment)
According to the above configuration, when a beacon signal is received from a different AP 200 in the second processing, the printer 10 executes the standby processing using the 60 ch for 200 msec in the third processing. In other words, the printer 10 performs an additional standby process using the 60 ch for 100 msec in addition to the standby process using the 60 ch for 100 msec. For this reason, the probability that the printer 10 receives a beacon signal from the AP 100 can be increased as compared with the configuration in which only the standby process is executed. By increasing the probability of receiving a beacon signal, a wireless LAN connection with the AP 100 can be established early. In the above case, the printer 10 can receive a beacon signal using the 60ch from the AP 100 in the additional standby processing, and can quickly establish a wireless LAN connection using the 60ch with the AP 100. (T120).

  Also, for example, in the third process, a standby process of using the 60 ch for 100 msec, another standby process of using the 64 ch for 100 msec, and an additional standby process of using the 60 ch for 100 msec Are performed in this order. In this comparative example, the channel is changed twice before execution of the additional standby processing. On the other hand, according to the configuration of the present embodiment, in the third process, after the previous standby process is performed, an additional standby process is performed subsequent to the previous standby process. That is, there is no need to change the channel. Therefore, as compared with the above-described comparative example, the number of times of changing the channel can be reduced, and the load on the CPU 22 of the printer 10 can be reduced.

  Further, according to the configuration of the present embodiment, the printer 10 executes the second passive scan of W53 when print data is being received from the terminal device 500 (S22 in FIG. 2). If print data is not being received, the first passive scan of W53 is executed (S14). That is, when the print data is not being received from the terminal device 500, the printer 10 does not execute the processes for executing the additional standby process (that is, S102 to S106, S122, and 124 in FIG. 5). In a situation where print data is not being received from the terminal device 500, it is less necessary to establish a wireless LAN connection with the AP 100 early. According to the configuration of the present embodiment, compared to a configuration in which the process of S10 in FIG. 2 is not performed and only the processes of S20 to S30 are performed, the printer 10 Of the CPU 22 can be reduced.

  Further, according to the configuration of the present embodiment, when the number indicated by the number information is two or more, the printer 10 determines the standby time to be 300 msec longer than 200 msec (S106 in FIG. 5). As the number of APs different from the AP 100 increases and the number of beacon signals transmitted by the different APs increases, the probability of receiving a beacon signal from the AP 100 decreases. According to the above configuration, the standby time becomes longer as the number of beacon signals increases, so that it is possible to suppress a decrease in the probability of receiving a beacon signal from the AP 100.

(Correspondence)
The printer 10, the wireless LAN I / F 14, and the memory 24 are examples of a “communication device”, a “wireless interface”, and a “memory”, respectively. The AP 100 and the AP 200 are examples of a “target access point” and a “different access point”, respectively. The four channels of W53 are an example of “two or more channels”. The standby process using the 60ch in the second process of FIG. 6 is an example of “normal standby process (and the K-th normal standby process)”. The additional standby processing using the 60 ch of the third processing in FIG. 6 includes the “(K + 1) -th normal standby processing”, It is an example of "additional standby processing". 100 msec is an example of “first time (and second time)”. The flag “1” is an example of “predetermined information”. The wireless LAN connection using 52ch in FIG. 6 is an example of “specific wireless connection”. The two, 200 msec, and 300 msec in S <b> 106 in FIG. 5 are examples of the “predetermined threshold”, the “first value”, and the “second value”, respectively. The SSID “XXX” is an example of “specific information”.

  S120 in FIG. 5 when the standby time is 100 msec is an example of processing realized by the “normal standby unit”. S120 of FIG. 5 in a case where the standby time is 200 msec is an example of processing realized by the “additional standby unit”. S150 in FIG. 5 is an example of a process realized by the “establishing unit”.

(Second embodiment)
(Second passive scan of W53; FIG. 7)
The second embodiment is the same as the first embodiment except that a part of the second passive scan of W53 is different. With reference to FIG. 7, a description will be given of the second passive scan of W53 of the present embodiment.

S200 is the same as S100 in FIG. S220 is the same as S120 in FIG. 5 except that the standby time is 100 msec. Step S222 is the same as step S122 in FIG. When determining that the beacon signal has not been received from a different AP using the scan channel (NO in S222), the CPU 22 skips S224 and proceeds to S226. On the other hand, when determining that the beacon signal has been received from a different AP using the scan channel (YES in S220), the CPU 22 proceeds to S224. Step S224 is the same as step S220. In other words, when a beacon signal is received from a different AP using the scan channel, the CPU 22 executes an additional standby process of S224 in addition to the standby process of S220.

  Steps S226 and S228 are the same as steps S126 and S128 in FIG. When determining that the beacon signal has been received from the AP 100 using the scan channel (YES in S220 or YES in S224), the CPU 22 proceeds to S250. Step S250 is the same as step S150 in FIG. When S250 ends, the process in FIG. 7 ends and the process in FIG. 2 ends.

(Specific case; FIG. 8)
A specific case realized by the second passive scan of W53 in FIG. 7 will be described with reference to FIG. In this case, a wireless LAN connection using 52 channels is established between the printer 10 and the AP 100 and between the terminal device 500 and the AP 100, as in the case of FIG.

  T200 to T206 are the same as T100 to T106 in FIG. When the printer 10 receives the switching signal from the AP 100 during the reception of the print data at T202, the printer 10 determines that the print data is being received (YES in S10 of FIG. 2), and performs an active scan of W53 (see FIG. 3). The second passive scan of W53 (see FIG. 7) is repeatedly executed (S20 and S22 in FIG. 2).

  The first processing in this case is the same as the first processing in the case of FIG. Since the printer 10 cannot receive the beacon signal from the AP 100 in the first process (NO in S220 in FIG. 7, YES in S226), the printer 10 executes the second process (NO in S24 in FIG. 2).

  While the second process is being executed, the AP 200 starts broadcasting a beacon signal using the 60ch. For this reason, the printer 10 receives a beacon signal including the SSID “YYY” from the AP 200 in the previous standby process using the channel 60 in the second process. Also, while the second process is being executed, the AP 100 starts broadcasting a beacon signal using the 60ch at T206. However, the printer 10 fails to receive the beacon signal from the AP 100 in the previous standby processing due to the reception of the beacon signal from the AP 200 in the previous standby processing (NO in S220 in FIG. 7).

  In this case, since the printer 10 receives the beacon signal including the SSID “YYY” from the AP 200 in the previous standby process, it determines that a beacon signal has been received from a different AP 200 (YES in S222 of FIG. 7). Then, the printer 10 executes an additional standby process using the 60ch (S224). In this case, the printer 10 receives a beacon signal including the SSID “XXX” from the AP 100 in the additional standby processing. Therefore, the printer 10 determines that a beacon signal has been received from the AP 100 in the additional standby process (YES in S224), and establishes a wireless LAN connection using the 60ch with the AP 100 in T220 (S250). .

  According to the configuration of the present embodiment, when a beacon signal using 60 ch is received from a different AP 200 in the second processing, the printer 10 additionally uses the 60 ch for 100 msec in the second processing. Execute the standby process of. Thereby, similarly to the first embodiment, it is possible to increase the probability of receiving a beacon signal from the AP 100.

  Also, for example, in the second processing, a standby processing of using the 60 ch for 100 msec, another standby processing of using the 64 ch for 100 msec, and an additional standby processing of using the 60 ch for 100 msec Are performed in this order. In this comparative example, the channel is changed twice before execution of the additional standby processing. On the other hand, according to the configuration of the present embodiment, in the second process, after the previous standby process is performed, an additional standby process is performed subsequent to the previous standby process. That is, there is no need to change the channel. Therefore, as compared with the above comparative example, the number of times of changing the channel can be reduced, and the processing load on the printer 10 can be reduced.

(Correspondence)
The standby process using the 60 ch in the second process of FIG. 8 is an example of the “normal standby process”. The additional standby processing using the 60ch in the second processing in FIG. 8 is an example of “additional standby processing”.

(Third embodiment)
(Second passive scan of W53; FIG. 9)
The third embodiment is the same as the first embodiment except that a part of the second passive scan of W53 is different. With reference to FIG. 9, a description will be given of the second passive scan of W53 of the present embodiment.

  S300 is the same as S100 of FIG. S320 is the same as S120 in FIG. 5 except that the standby time is 100 msec. Step S322 is the same as step S122 in FIG. In S324, the CPU 22 changes the flag corresponding to the scan channel in the flag table 32 from “0” to “1”. In this embodiment, the flag is reset to “0” when the processing in FIG. 9 ends.

  Steps S326 and S328 are the same as steps S126 and S128 in FIG. If the CPU 22 determines that all of the four channels of W53 have been used as scan channels (YES in S326), the process proceeds to S330.

  S330 is the same as S300. In S332, the flag corresponding to the scan channel is specified from the flag table 32, and it is determined whether or not the specified flag indicates “1”. When determining that the specified flag indicates “0” (NO in S332), the CPU 22 skips S340 and proceeds to S346. On the other hand, when determining that the specified flag indicates “1” (YES in S332), the CPU 22 proceeds to S340. Step S340 is the same as step S320. When determining that the beacon signal has been received from the AP 100 using the scan channel (YES in S340), the CPU 22 proceeds to S350. Note that the process of S350 is also executed when YES is determined in S320. Step S350 is the same as step S150 in FIG. When S350 ends, the processing in FIG. 9 ends and the processing in FIG. 2 ends.

  When determining that the beacon signal has not been received from the AP 100 using the scan channel (NO in S340), the CPU 22 proceeds to S346. Steps S346 and S348 are the same as steps S326 and S328. When determining that all of the four channels of W53 have been used as scan channels (YES in S346), the CPU 22 ends the process of FIG. 9 and proceeds to S24 of FIG.

(Specific case; FIG. 10)
A specific case realized by the second passive scan of W53 in FIG. 9 will be described with reference to FIG. In this case, a wireless LAN connection using 52 channels is established between the printer 10 and the AP 100 and between the terminal device 500 and the AP 100, as in the case of FIG.

  T300 to T306 are the same as T100 to T106 in FIG. When the printer 10 receives the switching signal from the AP 100 during the reception of the print data at T302, the printer 10 determines that the print data is being received (YES in S10 of FIG. 2), and performs the active scan of W53 (see FIG. 3). The second passive scan of W53 (see FIG. 9) is repeatedly executed (S20 and S22 in FIG. 2).

  The first processing in this case is the same as the first processing in the case of FIG. Since the printer 10 cannot receive a beacon signal from the AP 100 and a different AP (for example, the AP 200) in the first processing (NO in S320, YES in S326, NO in S340, YES in S346 in FIG. 9), the second processing is performed. Execute (NO in S24 of FIG. 2).

  While the second process is being executed, the AP 200 starts broadcasting a beacon signal using the 60ch. For this reason, the printer 10 receives a beacon signal including the SSID “YYY” from the AP 200 in the previous standby process using the channel 60 in the second process. In addition, while the second process is being executed, the AP 100 starts broadcasting a beacon signal using the 60ch at T306. However, the printer 10 fails to receive the beacon signal from the AP 100 in the previous standby processing due to the reception of the beacon signal from the AP 200 in the previous standby processing (NO in S320 of FIG. 9).

  In this case, since the printer 10 receives the beacon signal including the SSID “YYY” from the AP 200 in the previous standby process, it determines that a beacon signal has been received from a different AP 200 (YES in S322 of FIG. 9). The printer 10 changes the flag corresponding to 60ch to “1” (S324 in FIG. 9). Then, after using all of the four channels of W53 as the scan channels (YES in S326 of FIG. 9), the printer 10 determines 60ch as the scan channel (S330 of FIG. 9). Since the flag corresponding to 60ch indicates “1” (YES in S332 of FIG. 9), the CPU 22 executes an additional standby process using 60ch (S340 of FIG. 9). In this case, the printer 10 receives a beacon signal including the SSID “XXX” from the AP 100 in the additional standby processing. Therefore, the printer 10 determines that a beacon signal has been received from the AP 100 in the additional standby process (YES in S340 of FIG. 5), and establishes a wireless LAN connection using the 60ch with the AP 100 at T320. (S350).

  According to the configuration of the present embodiment, when a beacon signal using 60 ch is received from a different AP 200 in the second processing, the printer 10 additionally uses the 60 ch for 100 msec in the second processing. Execute the standby process of. Thereby, similarly to the first embodiment, it is possible to increase the probability of receiving a beacon signal from the AP 100.

(Correspondence)
The previous standby process using the 60ch in the second process of FIG. 10 is an example of “normal standby process”. The additional standby processing using the 60ch in the second processing in FIG. 10 is an example of “additional standby processing”.

  As described above, the specific examples of the present invention have been described in detail. However, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Modifications of the above embodiment are listed below.

  (Modification 1) The “communication device” may not be the printer 10, but may be, for example, a scanner, a multi-function device, a server, or another terminal device different from the terminal device 500.

  (Modification 2) In each of the above embodiments, the wireless LAN I / F 14 can execute wireless communication using W53. Instead, the wireless LAN I / F 14 may be capable of executing wireless communication using another DFS channel (for example, W56). W56 is eleven channels from 100 ch to 140 ch, and the channels from 100 ch to 140 ch are channels that classify frequencies from 5.470 GHz to 5.725 GHz. In the present modification, 100 ch to 140 ch are examples of “two or more channels”. Further, the wireless LAN I / F 14 may be capable of executing wireless communication using W53 and W56. In this modification, four channels of W53 and 11 channels of W56 are examples of “two or more channels”.

  (Modification 3) In each of the above embodiments, the standby process using the 60 ch for 100 msec is executed as an additional standby process (see FIG. 6). Instead, a standby process using the 60ch for a time different from 100 msec (for example, a time longer than 100 msec or a time shorter than 100 msec) may be executed as an additional standby process. Generally speaking, the “second time” may be the same time as the first time or may be a different time.

  (Modification 4) In the first embodiment, when the number indicated by the number information is two or more, the printer 10 determines the standby time to be 300 msec longer than 200 msec (S106 in FIG. 5). The present invention is not limited to this, and the printer 10 may determine the standby time to be 300 msec when the number indicated by the number information is M or more. The above M is, for example, a value of 3 or more. In the present modified example, the above M is an example of the “predetermined threshold”.

  (Modification 5) The beacon signal is not limited to the SSID “XXX” and may include, for example, a specific MAC address for identifying the AP 100. Then, when a beacon signal including a MAC address not matching the specific MAC address is received, the printer 10 may determine that a beacon signal has been received from a different AP (see S122 in FIG. 5). In the present modification, the specific MAC address is an example of “specific information”.

  (Modification 6) In each of the above embodiments, when a switching signal is received from the AP 100, the processing of S20 to S24 in FIG. 2 is executed. Instead, when the SSID “XXX” and the password of the AP 100 are input by the user via the operation panel of the printer 10, the processing of S20 to S24 may be executed. Generally speaking, the “communication device” need not receive the “switch signal”.

  (Modification 7) The process of S10 in FIG. 2 may not be executed. In the present modified example, the “judgment unit” can be omitted.

  (Modification 8) The memory 24 does not have to store the flag table 32. Then, in S106 of FIG. 5, the printer 10 may determine the standby time to be 200 msec regardless of the number of received beacon signals. In this modification, the “predetermined threshold value” can be omitted.

  (Modification 9) In each of the above embodiments, the active scan of W52 is executed in S12 and S20 of FIG. Instead, a passive scan of W52 may be executed in S12 and S20.

  (Modification 10) As described above, the “switching signal” is transmitted even when a plurality of APs using the same channel as the channel used by the AP 100 are present around the AP 100. . Then, the printer 10 may execute the processing in FIG. 2 when the switching signal due to the above-described reason is received.

  (Variation 11) The “two or more channels” are not limited to the DFS channels, but may be, for example, W52 which is a non-DFS channel, or a channel (for example, 1 ch to 14ch). For example, as described above, in the configuration in which the AP 100 transmits the switching signal due to the mixture of the lines, the printer 10 executes the second passive scan (see S22 in FIG. 2) for the non-DFS channel W52. May be.

  (Modification 12) In each of the above-described embodiments, the processing in FIGS. 2 to 10 is realized by the CPU 22 of the printer 10 executing the program 30 (that is, software). Alternatively, any of the processes may be realized by hardware such as a logic circuit.

2: communication system, 10: printer, 14: wireless LAN I / F, 20: control unit, 22: CPU, 24: memory, 30: program, 32: flag table, 34: AP information, 100: access point, 200: Access point, 500: terminal device

Claims (10)

A communication device,
A wireless interface that can use two or more channels;
A normal standby unit that executes a normal standby process via the wireless interface, wherein the normal standby process sequentially uses each of the two or more channels over a first time, and It is a process of waiting to receive a beacon signal from an access point, the target access point is an access point of the communication device to establish a wireless connection, the normal standby unit,
In the normal standby processing, when a beacon signal is received from an access point different from the target access point using a specific channel among the two or more channels, the normal standby processing is performed in addition to the normal standby processing. An additional standby unit that performs an additional standby process, wherein the additional standby process uses the specific channel for a second time to receive a beacon signal from the target access point. The additional waiting unit, which is a process of waiting,
In the normal standby process or the additional standby process, when a beacon signal is received from the target access point, via the wireless interface, an establishing unit that establishes a wireless connection with the target access point,
A communication device comprising: The communication device may further include:
In the normal standby process, using the specific channel, when a beacon signal is received from the different access point, a storage control unit that stores predetermined information in a memory, the beacon from the different access point When it is determined that the signal has not been received, the predetermined information is not stored in the memory, comprising the storage control unit,
The communication device according to claim 1, wherein the additional standby unit executes the additional standby processing when the predetermined information is stored in the memory. The normal standby unit repeatedly executes the normal standby process,
In the K-th normal standby process (where K is an integer of 1 or more), the additional standby unit uses the specific channel and receives a beacon signal from the different access point when the beacon signal is received. The communication device according to claim 1, wherein after the end of the normal standby process for the first time, the additional standby process is executed in addition to the (K + 1) th normal standby process.   The additional standby unit, in the normal standby process, when the beacon signal is received from the different access point while the specific channel is used over the first time, the specific channel Executing the additional standby process using the specific channel for the second time after the first channel has been used for the second time, following the use for the first time. The communication device according to claim 1, wherein: The normal standby unit, in a situation where a specific wireless connection with the target access point is established, when a switching signal is received from the target access point, executes the normal standby process,
The communication device according to any one of claims 1 to 4, wherein the switching signal is a signal that notifies the communication device of switching to a channel different from a channel used for the specific wireless connection. The communication device may further include:
When the switching signal is received from the target access point, comprising a determination unit that determines whether or not performing communication using the specific wireless connection,
When it is determined that the communication using the specific wireless connection is being executed,
The normal standby unit executes the normal standby process,
The additional standby unit, in the normal standby process, using the specific channel, when a beacon signal is received from the different access point, executes the additional standby process,
When it is determined that communication using the specific wireless connection is not being executed,
The normal standby unit executes the normal standby process,
The communication device according to claim 5, wherein the additional standby unit does not execute the additional standby processing. The additional standby unit,
In the normal standby processing, when a beacon signal is received from a number of the different access points less than a predetermined threshold using the specific channel, a first value is determined as the second time. ,
In the normal standby processing, when a beacon signal is received from the different access points equal to or more than the predetermined threshold using the specific channel, a second value larger than the first value is set to a second value. The communication device according to claim 1, wherein the communication device determines the second time. The beacon signal received from the target access point includes identification information for identifying the target access point,
The additional standby unit executes the additional standby process when a beacon signal not including the specific information is received from the different access point using the specific channel in the normal standby process. The communication device according to any one of claims 1 to 7.   The communication device according to claim 1, wherein the two or more channels include a DFS (Dynamic Frequency Selection) channel. A computer program for a communication device,
The computer of the communication device is configured by the following units:
A normal standby unit that executes a normal standby process via a wireless interface that can use two or more channels, wherein the normal standby process includes setting each of the two or more channels to a first time. A process of waiting for receiving a beacon signal from a target access point, wherein the target access point is a target access point to which the communication device should establish a wireless connection. Department and
In the normal standby processing, when a beacon signal is received from an access point different from the target access point using a specific channel among the two or more channels, the normal standby processing is performed in addition to the normal standby processing. An additional standby unit that performs an additional standby process, wherein the additional standby process uses the specific channel for a second time to receive a beacon signal from the target access point. The additional waiting unit, which is a process of waiting,
In the normal standby process or the additional standby process, when a beacon signal is received from the target access point, via the wireless interface, an establishing unit that establishes a wireless connection with the target access point,
A computer program that functions as a computer.

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