JP2007081468A - Wireless communication device and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish wireless connection surely even if the wireless communication channel of a device becoming a communication partner is altered in a wireless network where a plurality of devices capable of wireless communication exist. <P>SOLUTION: When wireless communication is performed between a digital camera 1 and a printer 201 capable of wireless communication through a wireless network, searching is performed using the wireless communication channel of wireless setting parameter information of the printer 201 stored in the digital camera 1. If it is not the wireless communication channel set in the printer 201, searching is performed using a plurality of available wireless communication channels sequentially so that connection can be established through a new wireless communication channel set in the printer 201 even if the wireless communication channel set in the printer 201 is altered. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a communication control method, and more particularly to a wireless connection establishment technique in wireless communication.

  Conventionally, when electronic devices are connected to each other, it is common to wire-connect the electronic devices using various cables. In recent years, in order to connect more easily, there has been an increase in wireless connection between electronic devices.

  For example, there is a wireless communication system using a wireless LAN as an example in which electronic devices are communicably connected by wireless communication. There are an infrastructure mode and an ad hoc mode as a method of wirelessly connecting devices via a wireless LAN.

  Wireless connection in infrastructure mode consists of one basic base station and a terminal station that is within the radio wave reach of the base station. Used mainly. In addition, the wireless connection in the ad hoc mode does not require a base station and is configured such that terminal stations communicate directly with each other, and temporarily establishes a wireless connection between a digital camera and a peripheral device such as a printer. Used in cases.

  In order to establish a wireless connection between electronic devices by these methods, each device needs to have various common wireless communication parameters. One of the wireless communication parameters is setting of a frequency band (channel), and devices performing wireless communication must perform communication using the same channel.

  Usually, in the case of wireless connection in infrastructure mode, a base station always exists, and communication between devices is realized via that base station, so the wireless communication channel of the terminal station is set according to the base station Often done. On the other hand, in the case of wireless connection in the ad hoc mode, unlike the wireless connection in the infrastructure mode, since there is no base station to which the channel is matched, the wireless communication channel is determined between the respective terminal stations, There are many communications over that channel. In other words, in the wireless connection in the normal ad hoc mode, it is assumed that the wireless communication channels are matched in advance between electronic devices to be wirelessly communicated, and it is possible to continue using the channel once set as it is. There were many.

  However, in wireless communication, when other devices use the same channel or adjacent channels, radio wave interference may occur and normal communication may not be performed. In such a case, both devices performing wireless communication can perform normal communication again by changing a channel used for another new channel that can be used from a preset channel in synchronization (for example, (See Patent Document 1).

Japanese Patent No. 3376186

However, the above-described prior art has the following problems.
An example will be described in which a single wireless communication apparatus as shown in FIG. 5 includes a plurality of devices capable of wireless communication with a plurality of connection partners.

  In FIG. 5, a printer 51 and a plurality of digital cameras 52 and 53 are communicably connected via a wireless LAN, and the printer 51 and digital camera 52 and the printer 51 and digital camera 53 can communicate by wireless connection in an ad hoc mode. Suppose there is. Also, it is assumed that there are 1 to 14 wireless communication channels that can be allocated.

  If the channel is set to “3” as the wireless communication parameter of the printer 51, the digital cameras 52 and 53 also set the channel to “3” in advance. By setting the same channel in this way, the printer 51 and the digital cameras 52 and 53 can perform wireless communication by wireless connection in the ad hoc mode using the determined channel “3”.

  However, here, in order to avoid radio wave interference, the wireless communication channel is changed between the printer 51 and the digital camera 52, and both the printer 51 and the digital camera 52 change the wireless communication channel to “10”. When the printer 51 can hold only one wireless communication channel information, the wireless communication channel set in the printer 51 is “10”, and the wireless communication channel of the digital camera 53 is “3”. As a result, even if the printer 51 and the digital camera 53 try to perform wireless communication, wireless communication cannot be performed because the wireless communication channels are different.

  The present invention has been made in view of such a problem. In a wireless network in which a plurality of devices capable of wireless communication exist, even when the wireless communication channel of a device that is a communication partner is changed, wireless connection is achieved. The purpose is to ensure that it can be established.

A wireless communication device according to the present invention is a wireless communication device capable of wireless communication with a communication partner device using an arbitrary wireless communication channel among a plurality of wireless communication channels, wherein the wireless communication device and the communication partner device are wirelessly connected. Communication means for performing communication, storage means for storing a wireless communication channel determined in advance for performing wireless communication with the communication partner apparatus by the communication means, and a wireless communication channel set for the communication partner apparatus. A search means for searching, wherein the search means performs a search using a wireless communication channel stored in the storage means, and the search means is not a wireless communication channel set in the communication partner apparatus. Is characterized in that the search is performed by sequentially using the plurality of wireless communication channels.
A wireless communication device according to the present invention is a first wireless communication device capable of wireless communication using an arbitrary wireless communication channel among a plurality of wireless communication channels, and wireless communication with the second wireless communication device. A communication means for performing communication, a determination means for determining whether or not a communication partner apparatus for performing wireless communication by the communication means exists on a wireless network, and a wireless communication channel used by the communication means for each communication partner in advance. Storage means for storing, when the communication means wirelessly communicates with the second wireless communication device, the determination means determines whether the second wireless communication device exists on the wireless network. Search with priority over other wireless communication channels using the wireless communication channel stored in the memory, and use a wireless communication channel different from the wireless communication channel stored in the storage means. When detecting a second radio communication apparatus, and changes to the wireless communication channel a wireless communication channel to the second wireless communication device is detected which is stored in the storage means.
A communication control method according to the present invention is a communication control method for a wireless communication apparatus capable of wirelessly communicating with a communication partner apparatus using an arbitrary wireless communication channel among a plurality of wireless communication channels. A communication step of performing wireless communication with the device, a storage step of storing in a storage means a wireless communication channel determined in advance to perform wireless communication with the communication partner device in the communication step, and a communication partner device A search step for searching for a set wireless communication channel, and in the search step, a search is performed using the wireless communication channel stored in the storage means, and this is set in the communication partner device. If the wireless communication channel is not set, the search is performed by sequentially using the plurality of wireless communication channels.
The program according to the present invention is a program for causing a computer to execute communication control of a wireless communication apparatus capable of wireless communication with a communication partner apparatus using an arbitrary wireless communication channel among a plurality of wireless communication channels. A communication step for performing wireless communication with the communication partner device, a storage step for storing in a storage means a wireless communication channel previously determined for wireless communication with the communication partner device in the communication step, and A search step of searching for a wireless communication channel set in a communication partner device, and performing a search using the wireless communication channel stored in the storage means in the search step, If it is determined that the wireless communication channel is not set to the communication partner device, the search is performed using the plurality of wireless communication channels sequentially. And wherein the Ukoto.
A computer-readable recording medium according to the present invention records the above program.

  According to the present invention, even when the settings relating to the wireless communication channel held by two devices communicating via a wireless network differ, one device searches for the channel set as the communication partner at the time of connection. Wireless connection can be established reliably.

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

FIG. 1 is a diagram illustrating a configuration example of a digital camera 1 according to an embodiment of the present invention. The digital camera 1 is a wireless communication device in the present embodiment. Note that the wireless communication device in the present embodiment is not limited to a digital camera, and may be replaced with another device. For example, the digital camera may be replaced with a device that operates as a digital camera such as a digital video camera or a mobile phone with a digital camera. In this embodiment, a digital camera and a device that operates as a digital camera are referred to as an imaging device.
In FIG. 1, 2 is a photographing lens, and 3 is a shutter having an aperture function. The image sensor 4 converts an optical image obtained by an optical system including the photographing lens 2 and the shutter 3 into an electric signal. The A / D converter 5 converts the analog signal output from the image sensor 4 into a digital signal.

  The timing generator 6 supplies a clock signal and a control signal to the image sensor 4, the A / D converter 5, and the D / A converter 7. The timing generator 6 is controlled by the memory controller 8 and the system controller 9. The D / A converter 7 converts the digital signal supplied from the memory control unit 8 into an analog signal.

  The memory control unit 8 controls the A / D converter 5, the timing generation unit 6, the D / A converter 7, the image processing unit 10, the image display memory 11, and the memory 12. The system control unit 9 controls the entire digital camera 1. The image processing unit 10 performs predetermined pixel interpolation processing and color conversion processing on the data from the A / D converter 5 or the data from the memory control unit 8. Data output from the A / D converter 5 is written into the image display memory 11 or the memory 12 through the image processing unit 10 and the memory control unit 8 or directly through only the memory control unit 8.

  The memory 12 is a memory for storing captured still images and moving images, and has a storage capacity sufficient to store a predetermined number of still images and a moving image for a predetermined time. The image display unit 13 includes a display device such as a TFT or an LCD, and displays image data of a display image written in the image display memory 11 supplied via the D / A converter 7. In addition, it is possible to implement | achieve an electronic finder function by displaying the image data imaged using the image display part 13 sequentially.

  The exposure control unit 14 controls the shutter 3 having a diaphragm function, and realizes a flash light control function in cooperation with the flash 17. The distance measurement control unit 15 controls focusing of the photographic lens 2. The zoom control unit 16 controls zooming of the taking lens 2. The flash 17 has an AF auxiliary light projecting function and a flash light control function.

  The power supply control unit 18 includes a battery detection circuit, a DC-DC converter, a switch circuit that switches a block to be energized, and the like. The power supply control unit 18 detects the presence / absence of a battery, the type of battery, and the remaining battery level, controls the DC-DC converter based on the detection result and the instruction of the system control unit 9, and requires the necessary voltage It is supplied to each part including the recording medium for a long period. The power supply unit 19 includes a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd (nickel cadmium) battery, a NiMH (nickel manganese hydrogen) battery, or a Li (lithium) battery, an AC adapter, or the like.

  The memory 20 stores constants, variables, programs, and the like for the operation of the system control unit 9. The display unit 21 visually and / or audibly outputs an operation state, a message, and the like using characters, images, sounds, and the like according to execution of the program by the system control unit 9. The display unit 21 is installed in a single or a plurality of positions near the operation unit 25 of the digital camera 1 so as to be easily visible, and is configured by, for example, an LCD (liquid crystal display device), an LED (light emitting diode), a speaker, or a combination thereof.

  The nonvolatile memory 22 is an electrically erasable / recordable memory, and stores wireless setting information of the apparatus. The memory card interface 23 is for connecting a memory card which is an example of a removable storage medium. The memory card is a card-like storage medium having a nonvolatile memory. As the memory card, an SD memory card, CompactFlash (registered trademark), or the like can be used. The USB interface 24 is for connecting to an external device using a USB. The operation unit 25 is used to input various operation instructions of the system control unit 9, and is configured by a single or a combination of a switch, a dial, a touch panel, pointing by line-of-sight detection, a voice recognition device, and the like.

  The shutter switch 26 performs exposure processing for writing a signal read from the image sensor 4 to the memory 12 via the A / D converter 5 and the memory control unit 8, and calculation in the image processing unit 10 and the memory control unit 8. An instruction to start the operation of a series of processing called development processing is used. The wireless communication unit 27 is compliant with IEEE802.11a / b / g or the like, and controls wireless communication with the printer 201 by transmitting and receiving wireless signals. The antenna 28 is an antenna that the wireless communication unit 27 has. The wireless communication unit 27 may be built in the digital camera 1 or removable from the digital camera 1.

FIG. 2 is a diagram illustrating a configuration example of the printer 201 according to the embodiment of the present invention.
The print engine 202 has a function of printing an image on paper, and prints an image supplied from the digital camera 1 from the paper supply unit 213 onto the paper. The paper discharge unit 214 discharges the paper on which the image is printed. A print control unit 205 controls the operation of the print engine 202. The display unit 203 displays a reduced image of the image to be printed, displays a setting menu, displays a message related to the printer 201, and displays a status of wireless communication with the digital camera 1. A liquid crystal display or the like can be used for the display portion 203. The display control unit 206 controls the operation of the display unit 203 and generates information displayed on the display unit 203.

  The operation unit 204 is an operation unit for inputting various operation instructions configured by a single or a plurality of combinations such as a switch, a dial, a touch panel, pointing by line-of-sight detection, and a voice recognition device via the system control unit 207. .

  The non-volatile memory 208 is an electrically erasable / recordable memory, and stores device wireless setting information. The memory 209 stores constants, variables, programs, and the like for the operation of the printer 201. The wireless communication unit 210 conforms to IEEE802.11a / b / g or the like, and controls wireless communication with the digital camera 1 by transmitting and receiving wireless signals. The antenna 215 is an antenna that the wireless communication unit 210 has. The wireless communication unit 210 may be built in the printer 201 or detachable from the printer 201. The USB interface 211 is for connecting to an external device using USB, and the interface 212 is for connecting to an external device such as a personal computer using parallel communication.

Next, an operation when wireless communication is requested between the digital camera 1 and the printer 201 described above will be described. In the following description, the wireless communication channels that can be assigned to the wireless communication between the digital camera 1 and the printer 201 are 1 to 14 channels.
FIG. 3 is a flowchart showing the operation of the digital camera 1 until establishing a wireless connection between the digital camera 1 and the printer 201 in the present embodiment.

  In the digital camera 1, the system control unit 9 requests the wireless communication unit 27 to start a wireless connection with the printer 201 in response to a request from the user (step S301). In wireless communication between the digital camera 1 and the printer 201, wireless parameters such as SSID (Service Set Identifier) which is network identification information used in a general wireless LAN, a wireless communication channel, and an encryption key are required. . As for these pieces of information, it is assumed that the printer 201 and the digital camera 1 previously hold common information. Note that the present embodiment does not depend on the method for holding this common information.

In step S301, the system control unit 9 reads the wireless setting parameter information of the connection partner from the non-volatile memory 22, and tries to connect using the wireless setting parameter common to the connection partner.
Next, the system control unit 9 sets an arbitrary timer value, and then performs the following operation (step S302). The set timer starts operation immediately after setting.

  The system control unit 9 checks whether or not the timer set in step S302 has expired, that is, whether or not it has timed out (step S303). As a result, if the timer has expired, the system control unit 9 notifies the user through the display unit 21 that the connection partner device has not been found (step S310), and ends the process. .

  On the other hand, if the timer has not expired, the system control unit 9 performs a search operation (scanning) of the device of the connection partner using the wireless communication channel of the wireless setting parameter information read in step S301 (step S304). ). Here, the scanning operation will be described.

  In wireless communication, a beacon signal is used to notify peripheral devices of information necessary for communication, and communication synchronization processing is performed. Here, the function of searching for a wireless network when a wireless terminal receives a beacon signal is called scanning, and there are two types of scanning: passive scanning and active scanning.

  When passive scanning is used when performing scanning in this embodiment, the digital camera 1 monitors and receives a beacon signal in a set channel according to wireless setting parameter information with a printer 201 set in advance. To do. When the beacon signal is received here, the system control unit 9 checks the SSID set in the beacon signal and determines whether or not it matches the SSID set as the wireless setting parameter information with the printer 201. . If the SSIDs match, it is determined that a beacon has been found, and the scanning operation is successful.

When using active scanning, the digital camera 1 transmits a frame called Probe Request to the set channel using the wireless setting parameter information with the printer 201 set in advance. The SSID of the wireless setting parameter information with the printer 201 set in advance is set in the contents of Probe Request. Thereafter, the digital camera 1 receives a frame called Probe Response from the printer 201. Upon receiving this probe response frame, the system control unit 9 determines that a beacon signal has been found, and the scanning operation is successful.
In the present embodiment, either scanning method may be used.

  Next, the system control unit 9 determines the result of the scanning operation in step S304 (step S305). As a result, when the scanning operation is successful, the same wireless channel as that set in the digital camera 1 is set in the printer 201 as the connection partner. Therefore, the system control unit 9 performs the wireless connection operation with the connection partner as it is (step S309), and ends the process.

On the other hand, if the scanning operation fails, the wireless communication function of the printer 201 that is the connection partner is not valid, or the wireless communication channel set in advance between the printer 201 and the digital camera 1 is changed on the printer 201 side. It may have been done.
If the scanning operation in step S304 fails, the system control unit 9 performs the scanning operation for a channel other than the wireless communication channel of the wireless setting parameter information read in step S301 (step S306).

The scanning operation for another wireless communication channel performed in step S306 will be described with reference to FIG.
First, in step S401, the system control unit 9 sets a wireless communication channel to be scanned (hereinafter referred to as “scan channel”) to “1”. Next, the system control unit 9 performs a scanning operation using the set scan channel (step S402).

  Subsequently, the system control unit 9 determines the result of the scanning operation in step S402 (step S403). As a result, if the scan is successful, the system control unit 9 ends the operation assuming that the scanning operation is successful. On the other hand, if the scan has failed, the process proceeds to step S404.

  In the wireless LAN according to the present embodiment, since the usable wireless channels are 1 to 14, the system control unit 9 checks whether or not the scan channel is “14” (step S404). When the scan channel is “14”, the system control unit 9 ends the operation assuming that the scanning operation has failed because no connection partner device has been found in all available wireless communication channels. On the other hand, if the scan channel is not “14”, the system control unit 9 increments the scan channel by 1 (step S405) and returns to step S402. Thereafter, this operation is repeated.

  Returning to FIG. 3, the system control unit 9 determines the result of the scanning operation in step S306 (step S307). As a result, when the scanning operation fails, the system control unit 9 returns to step S303 and repeats the process. If no timeout has occurred here, the search operation is performed again for the preset channel in step S304.

  As described above, the search operation is repeatedly and preferentially performed for a preset channel, so that, for example, when the wireless communication function of the connection partner printer 201 is activated after the digital camera 1, the printer 201 can be quickly operated. Detection and connection can be established quickly. That is, when the printer 201 operates on a channel preset in the digital camera 1, the digital camera 1 performs an operation for searching for a connection partner at a high frequency for the preset channel. It can be detected quickly.

  Further, when a scanning operation is performed on a preset channel in step S304, this scanning operation may be made longer in time than the scanning operation on other channels. For example, if you are performing passive scanning on a preset channel, you can increase the monitoring time of other beacon signals, and if you are performing active scanning, increase the time to wait for Probe Response. That's fine. By doing so, the operation of detecting the printer 201 in a preset channel is lengthened, so that when the wireless of the printer 201 is activated, it is possible to quickly detect and establish a connection quickly.

  If the result of determination in step S307 is that the scanning operation has been successful, processing proceeds to step S308. In step S307, the system control unit 9 determines in which channel the scanning operation has been successful, and if it is different from the current wireless communication channel information, updates the channel information of the stored wireless setting parameters (step S307). S308). Then, the system control unit 9 performs a connection operation with the connection partner using the channel (step S309), and ends the process.

  As described above, according to the present embodiment, when wireless communication between the digital camera 1 and the printer 201 capable of wireless communication on a wireless network such as a wireless LAN is performed, the wireless connection between the digital camera 1 and the printer 201 is established. It can be established reliably. Even if the wireless communication channel of the printer 201 is changed from the wireless communication channel expected by the digital camera 1 and is different from the wireless communication channel expected by the digital camera 1, it is not necessary to perform another user operation on the digital camera 1. A new wireless communication channel connection can be established. In addition, since the digital camera 1 preferentially performs the search operation of the device of the connection partner with respect to the wireless communication channel previously held as the set value, the time required for the search can be shortened and the connection can be quickly established. it can.

(Other embodiments)
The above-described embodiments can also be realized by a computer program that can be executed by a computer (or CPU, MPU, etc.) in the apparatus or system. In this case, the computer program is supplied to the apparatus or system via a computer-readable recording medium. As the computer-readable recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
Further, by executing the computer program supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) or other application software in which the computer program is running on the computer, etc. Needless to say, such a computer program is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with the embodiment.
Further, after the supplied computer program is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or function expansion unit based on the instructions of the computer program Needless to say, the present invention includes a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

It is a block diagram which shows the structural example of the digital camera in one Embodiment of this invention. 1 is a block diagram illustrating a configuration example of a printer according to an embodiment of the present invention. It is a flowchart which shows the process sequence of the digital camera in this embodiment. It is a flowchart which shows the process sequence of search operation | movement with the digital camera in this embodiment. 1 is a diagram illustrating a wireless communication system in which a plurality of devices are wirelessly connected.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 9 System control part 22 Non-volatile memory 27 Wireless communication part 28 Antenna 201 Printer 207 System control part 208 Non-volatile memory 210 Wireless communication part 215 Antenna

Claims (9)

A wireless communication device capable of wireless communication with a communication partner device using an arbitrary wireless communication channel among a plurality of wireless communication channels,
A communication means for performing wireless communication with the communication partner device;
Storage means for storing a predetermined wireless communication channel for wireless communication with the communication partner device by the communication means;
Search means for searching for a wireless communication channel set in the communication partner device,
The search means performs a search using a wireless communication channel stored in the storage means, and if the search means is not a wireless communication channel set in the communication partner device, the plurality of wireless communication channels A wireless communication apparatus for performing a search using the information sequentially.   When the wireless communication channel set in the communication partner device searched by the search means is different from the wireless communication channel stored in the storage means, the wireless communication channel stored in the storage means is searched. The wireless communication apparatus according to claim 1, wherein the wireless communication channel is updated to a wireless communication channel searched by the means.   If the search means cannot search for the wireless communication channel set in the communication partner device as a result of sequentially searching using the plurality of wireless communication channels, the search means is stored in the storage means. The wireless communication apparatus according to claim 1, wherein the search is performed again using a wireless communication channel that is connected. A first wireless communication apparatus capable of wireless communication using an arbitrary wireless communication channel among a plurality of wireless communication channels,
A communication means for performing wireless communication with the second wireless communication device;
A determination means for determining whether or not a communication partner apparatus for performing wireless communication by the communication means exists on a wireless network;
Storage means for storing in advance the wireless communication channel used by the communication means for each communication partner;
A wireless communication channel in which whether or not the second wireless communication device exists on a wireless network is stored in the storage device by the determination device when wirelessly communicating with the second wireless communication device by the communication device Use to search for other wireless communication channels in preference,
When the second wireless communication device is detected by a wireless communication channel different from the wireless communication channel stored in the storage means, the wireless communication channel stored in the storage means is changed to the second wireless communication device. A wireless communication apparatus, wherein the wireless communication channel is changed to a detected wireless communication channel.   Whether or not the second wireless communication device exists on the wireless network is searched first for the wireless communication channel stored in the storage means, and the second wireless communication device is not detected. 5. The wireless communication apparatus according to claim 4, wherein the search is performed using a wireless communication channel different from the searched wireless communication channel.   6. The search time using a wireless communication channel stored in the storage means is set longer than the search time using a wireless communication channel different from the wireless communication channel. Item 1. A wireless communication device according to item 1. A communication control method for a wireless communication device capable of wireless communication with a communication partner device using an arbitrary wireless communication channel among a plurality of wireless communication channels,
A communication step of performing wireless communication with the communication partner device;
A storage step of storing, in a storage unit, a wireless communication channel determined in advance for performing wireless communication with the communication partner device in the communication step;
A search step of searching for a wireless communication channel set in the communication partner device,
In the search step, a search is performed using the wireless communication channels stored in the storage means, and when the search is not a wireless communication channel set in the communication partner device, the plurality of wireless communication channels A communication control method characterized by performing a search by sequentially using. A program for causing a computer to execute communication control of a wireless communication device capable of wireless communication with a communication partner device using an arbitrary wireless communication channel among a plurality of wireless communication channels,
A communication step for performing wireless communication with the communication partner device;
A storage step of storing in the storage means a wireless communication channel determined in advance to perform wireless communication with the communication partner device in the communication step;
A search step of searching for a wireless communication channel set in the communication partner device,
In the search step, if the search is performed using the wireless communication channel stored in the storage means and it is determined that the search is not a wireless communication channel set in the communication partner device, the plurality of A program for performing a search by sequentially using wireless communication channels.   9. A computer-readable recording medium on which the program according to claim 8 is recorded.

Images