JP2016158026A - Retrieval radio communication device and radio communication device to be retrieved - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a retrieval radio communication device for improving the detection rate of a radio communication device to be retrieved while shortening a retrieval time in the case that a plurality of retrieval radio communication devices retrieve the radio communication device to be retrieved.SOLUTION: The retrieval radio communication device includes: a probe response offset time storage part 45 for storing time information which is added to a probe request transmitted from another retrieval radio communication device which retrieves a radio communication device to be retrieved and includes information of a standby time when the radio communication device to be retrieved transmits a probe response; and a retrieval message control part 44 for causing the transmission of a probe request from its own device to perform standby until a probe response waiting period termination of the another retrieval radio communication device in the case of determining that a probe response waiting period being a reception period of a probe response when the own device performs retrieval overlaps a probe response waiting period of the another retrieval radio communication device on the basis of the time information.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a search radio communication device and a search radio communication device that search for a search radio communication device.

  In the device search by the conventional wireless LAN (Local Area Network), the wireless communication apparatus broadcasts a probe request message (hereinafter referred to as a probe request) to an arbitrary channel, and the MinChannelTime period, which is the minimum standby period, It waits for a probe response message (hereinafter referred to as a probe response) from the device. The search target peripheral device that has received the probe request unicasts a probe response to the wireless communication apparatus. When the wireless communication apparatus receives a probe response during the MinChannelTime period, the wireless communication apparatus extends the probe response standby period to MaxChannelTime, which is the maximum standby period. When the wireless communication apparatus receives MinChannelTime or one or more probe responses, after the MaxChannelTime elapses, the wireless communication apparatus changes the channel and repeats the device search process, and performs the device search process on all available channels. Such a technique is disclosed in the following Non-Patent Document 1.

  Regarding other device search methods, in Non-Patent Document 2 below, the wireless communication apparatus sequentially issues probe requests to which probe channel offset time information indicating the start timing of MinChannelTime or MaxChannelTime and probe response reception channel information are added to all channels. A technique for transmitting is disclosed. The peripheral device that has received the probe request transmits the probe response through the designated probe response reception channel after the designated probe response offset time. The wireless communication apparatus can receive probe responses from peripheral devices collectively in a specific period, and can shorten the search time for peripheral devices as compared to Non-Patent Document 1.

  Further, in Patent Document 1 below, by controlling the transmission timing of a response signal to a response request signal for finding an unnecessary communication link, collision of response signals is avoided, and unnecessary communication links are released in a timely manner. Thus, a technique for effectively using the channel is disclosed.

JP 2010-239608 A

IEEE Computer Society, 802.11 (TM) -2012 -IEEE Standard for Information technology - Telecommunications and information exchange between systems Local and metropolitan area networks - Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer ( PHY) Specifications Fujikami et al. “Reduction of terminal detection time in inter-vehicle communication using wireless LAN” The Institute of Electronics, Information and Communication Engineers General Conference B-5-145 March 2014

  However, according to the above-described conventional technology, when a plurality of wireless communication apparatuses perform device search, the collision of messages increases due to an increase in probe requests transmitted from the wireless communication apparatuses and probe responses transmitted from peripheral devices. There was a problem that the packet arrival rate was lowered and the detection rate of peripheral devices was lowered.

  The present invention has been made in view of the above, and in the case where a plurality of search radio communication devices search for a search radio communication device, the search improves the detection rate of the search radio communication device while shortening the search time. An object is to obtain a wireless communication device.

  In order to solve the above-described problems and achieve the object, the search radio communication device according to the present invention is added to a probe request transmitted from another search radio communication device that searches for a search radio communication device, A time information storage unit is provided that stores time information including information on a waiting time when the searched wireless communication device transmits a probe response that is a response to the probe request. In addition, when the search wireless communication device receives a probe request from another search wireless communication device, the search wireless communication device stores the time information in the time information storage unit, and based on the time information, the probe response when the own device performs a search is stored. If it is determined that the probe response standby period, which is the reception period, overlaps with the probe response standby period of another search wireless communication device, the probe request transmission from the own device waits until the probe response standby period of the other search wireless communication device ends. A search message control unit.

  According to the present invention, when a plurality of search wireless communication devices search for a searched wireless communication device, the detection rate of the searched wireless communication device can be improved while reducing the search time.

The figure which shows the structural example of the radio | wireless communications system concerning Embodiment 1. FIG. The figure which shows an example of the frame format of "Vendor SpecificInfo" contained in the probe request frame concerning Embodiment 1. The figure which shows the example applied to the pedestrian search system of the radio | wireless communications system concerning Embodiment 1. FIG. FIG. 2 is a block diagram illustrating a configuration example of a search device and a search target device according to the first embodiment. FIG. 3 is a flowchart showing processing of a search operation in which the search device according to the first embodiment searches for a search target device; FIG. 10 is a flowchart showing processing of an operation of a search target device when the search device according to the first embodiment searches; The figure which shows the transmission / reception timing of the search message between the search device concerning Embodiment 1, and a to-be-searched device. 1 is a diagram illustrating a hardware configuration of a search device and a search target device that are wireless communication apparatuses according to a first embodiment; FIG. 3 is a block diagram illustrating a configuration example of a search device and a search target device according to the second embodiment. FIG. 9 is a flowchart illustrating processing of a search operation in which a search device according to the second embodiment searches for a search target device. The figure which shows the timing of transmission / reception of the search message between the search device concerning Embodiment 2, and a to-be-searched device. FIG. 7 is a block diagram illustrating a configuration example of a search device and a search target device according to the third embodiment. 10 is a flowchart showing processing of a search operation in which a search device according to the third embodiment searches for a search target device. FIG. 10 is a flowchart showing processing of an operation of a search target device when the search device according to the third embodiment searches. The figure which shows the transmission / reception timing of the search message between the search device concerning Embodiment 3, and a to-be-searched device.

  Hereinafter, a search radio communication device and a search radio communication device according to an embodiment of the present invention will be described in detail based on the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a radio communication system 100 according to the first embodiment of the present invention. The wireless communication system 100 includes a plurality of search devices 21 and 22 that are search wireless communication apparatuses and a plurality of search target devices 1, 2, 3, 4, 5, 6, 7, 8, and 9 that are search wireless communication apparatuses. , 10 and 11. The search devices 21 and 22 and the search target devices 1 to 11 perform wireless communication with each other.

  The search devices 21 and 22 transmit probe requests that are search request messages when searching for the search target devices 1 to 11. The search target devices 1 to 11 that have received the probe request transmit a probe response of a search response message that is a response to the probe request to the search device that is the transmission source of the probe request. The search devices 21 and 22 that have received the probe response transmit ACK (ACKnowledgement) indicating a delivery confirmation or a positive response, which is a response message to the probe response, to the search target devices 1 to 11 that have transmitted the probe response. In the following description, probe requests, probe responses, delivery confirmations, and ACKs transmitted and received between the search devices 21 and 22 and the search target devices 1 to 11 may be collectively referred to as a search message. Here, the frame format of the probe request, the probe response, and the delivery confirmation will be described. FIG. 2 is a diagram illustrating an example of a frame format of “Vendor Specific Info” included in the probe request frame according to the first embodiment. The frame format of probe request, probe response, and delivery confirmation is based on the wireless LAN standard. The delivery confirmation (ACK) is added because “Vendor Specific Info” is not defined. In FIG. 2, “Element ID” indicates the type of information about this frame, “Length” indicates the frame length of this frame, and “OUI (Organizationally Unique Identifier)” and “OUItype” are assigned to organizations such as IEEE. “Response Offset Time” indicates a probe response offset time, and “Response Channel” is a probe response reception channel. In addition, “information num” indicates the number of combinations of “information type” and “information”, “information type” indicates the type of information set in “information”, and “information” whose size is variable length Includes information to be shared between the search device and the search target device. A plurality of combinations of “information type” and “information” can be included. When there is no additional information, the probe request has a frame format after “information num”, that is, a frame format in which the information on the right side is deleted from “information num” in FIG. The probe response and the delivery confirmation have a frame format in which “Response Offset Time” and “Response Channel” are deleted from the frame format shown in FIG. In the following description, when the search devices 21 and 22 add information to be shared between the search device and the search target device to the probe request and the delivery confirmation, the search devices 1 to 11 search the probe response and When adding information desired to be shared between search target devices, areas of “information num”, “information type”, and “information” are used.

  The wireless communication system 100 can be applied, for example, as a pedestrian search system using a vehicle, to inter-pedestrian communication in which a wireless LAN function is installed in a device carried by a vehicle and a pedestrian to perform communication. FIG. 3 is a diagram illustrating an application example of the wireless communication system 100 according to the first embodiment to a pedestrian search system. In the pedestrian search system shown in FIG. 3, the search device 21 is fixed to the automobile 30, the searched devices 1 and 2 are brought into the automobile 30, and the searching device 21 and the searched devices 1 and 2 are connected to the outside of the vehicle. Wireless communication is performed with the search devices 3 to 5. The search device 21 fixed to the automobile 30 is a head unit of the automobile 30, a car navigation device, a car audio device, a rear seat monitor, or the like. The searched devices 1 and 2 are a tablet, a smartphone, a portable game device, a music player, a personal computer, and the like. Further, the searched devices 3 to 5 are a tablet, a smartphone, a portable game device, a public wireless LAN base station such as a hotspot base station or a relay station, a wireless LAN compatible digital signage, and the like.

  The search device 21 can search for a pedestrian carrying the search target devices 1 to 5 by searching the search target devices 1 to 5 outside the vehicle.

  Note that the wireless communication system 100 of the first embodiment is not limited to these exemplified configurations and operation methods, and in addition to inter-pedal communication, digital signage, smart meter, M2M (Machine-to-Machine), The present invention is applicable in an environment where many terminals communicate such as IoT (Internet of Things). In the first embodiment, the wireless communication system 100 will be described using a wireless LAN, but this is an example and the present invention is not limited to this.

  FIG. 4 is a block diagram of a configuration example of the search devices 21 and 22 that are the search wireless communication apparatuses according to the first embodiment and the search target devices 1 to 11 that are the search wireless communication apparatuses. The configuration shown in FIG. 4 is an example, and the present invention is not limited to this. In addition, here, the search devices 21 and 22 and the search target devices 1 to 11 have the same configuration, but this is an example and the present invention is not limited to this. For convenience, reference numeral 21 is given as the search device 21 in FIG.

  The search devices 21 and 22 and the devices to be searched 1 to 11 are communication circuits for wireless communication, have a transmission function compliant with IEEE (Institut of Electrical AND Electronics Engineers) 802.11, and MAC (Media Access Control). ) A transmission unit 41 that performs modulation processing of the wireless LAN frame notified from the control unit 43 and transmits it from the antenna, a communication circuit for wireless communication, has a reception function compliant with IEEE802.11, an antenna A receiving unit 42 that performs demodulation processing of the signal received from the receiver and notifies the MAC controller 43 of the wireless LAN frame, generates a MAC frame by MAC control including device search, notifies the transmitter 41, and receives Notified from the unit 42 Comprising from AC frame and MAC controller 43 notifies the searching message control unit 44 extracts the message associated with the device search, the. In addition, when the search devices 21 and 22 and the search target devices 1 to 11 operate as search devices that transmit a probe request to search for a search target device, the search device receives the probe response to be added to the probe request. Of probe response offset time, which is time information including probe response reception channel, which is channel information of the channel to be used, and waiting time information when the searched device transmits a probe response, which is a response to the probe request. When operating as a searched device that controls the parameters, receives the probe request, and transmits the probe response, controls the probe response transmission timing to notify the MAC control unit 43 of the parameters for generating the MAC frame, In addition, the probe request or the probe notified from the MAC control unit 43 The search message control unit 44 that performs processing for storing information necessary for control from the response and the probe request transmitted from another search device that searches for the search target device is a probe request. The probe response offset time, which is time information including information on the waiting time when transmitting a probe response that is a response to the request, and is added to the probe request transmitted from the surrounding search device is stored. A probe response offset time storage unit 45 which is a time information storage unit.

  Next, a search operation in which the search devices 21 and 22 in the first embodiment search for the search target devices 1 to 11 will be described. As an example, the search device 21 will be described, but the search device 22 performs a similar search operation.

  As described above for each configuration, in the search device 21, when transmitting a probe request or the like, the search message control unit 44 notifies the MAC control unit 43 of parameter information for generating a probe request frame. Then, the MAC control unit 43 generates a probe request message based on the notification from the search message control unit 44, and transmits the probe request message from the transmission unit 41 to the search target devices 1 to 11 via the antenna. In the search device 21, when receiving a probe response, when the reception unit 42 receives a probe response message via an antenna, the MAC control unit 43 controls a search message for a message related to the device search included in the probe response. The search message control unit 44 performs control to transmit a delivery confirmation.

  In the search device 21 according to the first embodiment, the subject of the characteristic operation is the search message control unit 44. Similarly, in the operation of the search target device 1 described later, the subject of the characteristic operation is the search message control unit 44. Therefore, in the following description, in order to clarify the difference between the search device and the search target device and simplify the description, “search device” and “search target device” will be mainly described, and the search message control unit 44 Only the portion related to the configuration other than will be described using each configuration such as the search message control unit 44 and the probe response offset time storage unit 45. The same applies to the following embodiments.

  FIG. 5 is a flowchart of a search operation process in which the search device 21 according to the first embodiment searches for the search target devices 1 to 11. In the search device that has received the probe request of the peripheral search device, the search message control unit 44 stores the probe response offset time information added to the probe request of the peripheral search device in the probe response offset time storage unit 45. I will let you.

  (Step S001) The search device 21 that searches for the search target devices 1 to 11 in the vicinity checks whether or not the probe request transmitted from the other search device 22 has been received. The search device 21 proceeds to the process of step S002 when receiving (step S001: Yes), and proceeds to the process of step S004 when not received (step S001: No).

  (Step S002) In the search device 21, when the probe request transmitted from the other search device 22 is received in the process of step S001, the search message control unit 44 is added to the probe request of the other search device 22. In addition, the probe response offset time storage unit 45 stores information on the probe response offset time indicating the start timing of MinChannelTime or MaxChannelTime. The search message control unit 44 of the search device 21 determines the other from the relationship between the probe response offset time added to the received probe request of the other search device 22 and the time for transmitting the probe request from the own device to all channels. It is determined whether or not the probe response standby period, which is the probe response reception period in the search device 22, overlaps with the own probe response standby period. Whether or not they overlap is determined to overlap if part of both probe response waiting periods overlap. The search message control unit 44 of the search device 21 starts the probe response standby period of another search device 22 after the probe response offset time, and, as described in the background art, the probe response that is the reception period of the probe response. Since the standby period is MinChannelTime or MaxChannelTime, the probe response standby period of the other search device 22 can be estimated based on the probe response offset time of the other search device 22. Specifically, the search message control unit 44 of the search device 21 estimates the MinChannelTime or MaxChannelTime period that starts after the probe response offset time of the other search device 22 as the probe response standby period of the other search device 22. When the search message control unit 44 of the search device 21 determines that there is a duplication (step S002: Yes), the process proceeds to step S003, and when it is determined that there is no overlap (step S002: No), the process proceeds to the process of step S004.

  (Step S003) The search message control unit 44 of the search device 21 waits for transmission of a probe request from its own device until the probe response waiting period of another search device 22 that has received the probe request ends. Since the search message control unit 44 of the search device 21 estimates the probe response standby period of the other search device 22 in step S002, the search message control unit 44 itself until the estimated probe response standby period of the other search device 22 ends. Do not send probe requests from the device.

  (Step S004) The search device 21 broadcasts a probe request while changing the operation channel for all available channels. Here, it is assumed that all usable channels are 11 channels of channels # 1 to # 11.

  (Step S005) The search device 21 performs carrier sense to confirm whether transmission is possible, and waits for a backoff time. As the back-off time, for example, a back-off time defined in IEEE 802.11 may be used, or a back-off time according to other specifications may be used. The search device 21 proceeds to step S006 after transmission is possible.

  (Step S006) The search device 21 transmits a probe request to which information on the probe response reception channel and the probe response offset time is added on the operation channel set in Step S004. The search device 21 sets an arbitrary channel as a probe response reception channel, and sets a probe response offset time longer than the time required for transmission processing from the start to completion of transmission of probe requests to all channels. Set. The search device 21 does not change the probe response reception channel during the loop processing in steps S004 to S006, and uses the same channel.

  (Step S007) When transmission of the probe request to channels # 1 to # 11 is completed in steps S004 to S006, the search device 21 changes its own operation channel to the probe response reception channel set in step S006.

  (Step S008) The search device 21 waits until the start of the probe response standby period, that is, until the probe response offset time added to the probe request first transmitted in Step S006 elapses.

  (Step S009) The search device 21 sets the end time of the probe response standby period to MinChannelTime.

  (Step S010) The search device 21 resets the elapsed time of the probe response waiting period to zero.

  (Step S011) When the elapsed time of the probe response standby period is within the end time of the probe response standby period, the search device 21 continues the probe response standby by the loop processing in steps S011 to S015.

  (Step S012) The search device 21 confirms whether or not a probe response has been received during the probe response standby period. When the search device 21 receives the probe response (step S012: Yes), the search device 21 proceeds to the process of step S013. When the search device 21 does not receive the probe response (step S012: No), the process of steps S013 to S015 is omitted.

  (Step S013) The search device 21 confirms whether or not the received probe response is the first probe response received within the MinChannelTime within the elapsed time of the probe response standby period. If the probe response is the first probe response received within MinChannelTime (step S013: Yes), the search device 21 proceeds to the process of step S014, and otherwise (step S013: No) proceeds to the process of step S015.

  (Step S014) The search device 21 extends the end time of the probe response standby period to MaxChannelTime.

  (Step S015) The search device 21 transmits ACK to the search target device that has transmitted the probe response. The search message control unit 44 of the search device 21 stores information on the search target device that has transmitted the probe response in the memory.

  (Step S016) After the elapsed time of the probe response standby period exceeds the end time of the probe response standby period, the search device 21 changes the changed operation channel of the own device to the original operation channel.

  In the flowchart of FIG. 5, the order of the processes in steps S007 and S008 may be interchanged.

  Next, operations of the devices to be searched 1 to 11 when the search devices 21 and 22 in the first embodiment search are described. As an example, the search target device 1 will be described, but the search target devices 2 to 11 perform the same search operation. FIG. 6 is a flowchart of an operation process of the search target device 1 when the search devices 21 and 22 according to the first embodiment search.

  (Step S501) The to-be-searched device 1 checks whether or not a probe request has been received from one or both of the searching devices 21 and 22. The searched device 1 proceeds to the process of step S502 when the probe request is received (step S501: Yes), and proceeds to the process of step S503 when not received (step S501: No).

  (Step S502) In the to-be-searched device 1, the search message control unit 44 stores information on the probe response reception channel and the probe response offset time added to the received probe request. The search message control unit 44 may store the information on the probe response reception channel and the probe response offset time in the probe response offset time storage unit 45 or may be stored in another storage unit (not shown).

  (Step S503) The to-be-searched device 1 confirms whether there is any probe response offset time stored in step S502 that has passed the period set by the probe response offset time. If there is a device to be searched 1 (step S503: Yes), the process proceeds to step S504. If there is no device to be searched (step S503: No), the process proceeds to step S501.

  (Step S504) The to-be-searched device 1 confirms whether there is an unprocessed probe request that has not returned a probe response among the probe requests in which the probe response reception channel and the probe response offset time information are stored in Step S502. To do. The searched device 1 proceeds to the process of step S505 when there is an unprocessed probe request (step S504: Yes), and proceeds to the process of step S511 when there is no unprocessed probe request (step S504: No).

  (Step S505) After the probe response offset time added to the probe request elapses, the searched device 1 changes its own operation channel to the probe response reception channel added to the probe request.

  (Step S506) The to-be-searched device 1 performs carrier sense similarly to the process of step S005 shown in FIG. 5, and waits for a back-off time. The search target device 1 proceeds to step S507 after transmission is enabled.

  (Step S507) The to-be-searched device 1 unicasts a probe response to the search device that has transmitted the probe request using the operation channel set in step S505.

  (Step S508) The to-be-searched device 1 confirms whether ACK was received from the searching device which transmitted the probe request. The searched device 1 proceeds to the process of step S504 when ACK is received (step S508: Yes), and proceeds to the process of step S509 when not received (step S508: No).

  (Step S509) The to-be-searched device 1 confirms whether or not an ACK reception timeout has occurred. The searched device 1 increments the number of times of retransmission when the ACK reception time-out occurs (step S509: Yes), and proceeds to the processing of step S510. If the time-out has not timed out (step S509: No), step S508 is performed. Continue to wait to receive ACK in the process.

  (Step S510) The to-be-searched device 1 checks whether or not the number of retransmissions of the probe response is equal to or less than a threshold for the number of retransmissions. If the search target device 1 is equal to or smaller than the threshold (step S510: Yes), the process proceeds to step S506, and the probe response is retransmitted. If the search target device 1 exceeds the threshold (step S510: No), the probe response transmission process to the corresponding search device is determined to have failed, and the process proceeds to step S504, where the probe request received from another search device is received. Continue processing.

  (Step S511) When there is no unprocessed probe request (step S504: No), the searchee device 1 changes the changed operation channel of the own device to the original operation channel.

  FIG. 7 is a diagram illustrating transmission / reception timings of search messages between the search devices 21 and 22 and the search target devices 1, 6, and 11 according to the first embodiment. The operation channel of the search device 21 is channel # 1, the operation channel of the search device 22 is channel # 6, and the operation channels of the search target devices 1 to 11 are channels # 1 to # 11 which are the same as the codes of the own device.

  The search devices 21 and 22 transmit probe requests in order from channel # 1 to channel # 11, and search for search target devices 1 to 11. First, when the search device 22 starts transmitting a probe request, the search request transmitted to the channel # 1 is also received by the search device 21. The search device 21 estimates the probe response standby period of the search device 22 from the probe response offset time added to the received probe request, and the probe response standby period set by the own device and the probe response of the search device 22 If it is determined that the standby periods overlap, the probe device waits for the probe response transmission period of the search device 22 to end. The searched devices 1 to 11 that have received the probe request change their own operation channel to the probe response reception channel added to the probe request after the probe response offset time set in the probe request, and perform carrier sense. The probe response is transmitted after the transmission becomes possible due to the back-off time waiting. When the search devices 21 and 22 receive one or more probe responses during MinChannelTime, the search devices 21 and 22 extend the probe response standby period to MaxChannelTime.

  As described above, in the present embodiment, the wireless communication system can reduce the collision of search messages such as probe requests and probe responses and improve the device detection rate even in an environment where a plurality of search devices exist. .

  In FIG. 7, the search devices 21 and 22 transmit probe requests to the channel # 1 to channel # 11 in order, but the probe request transmission order may be random.

  In FIG. 7, the search device 21 transmits probe requests to all channels until the end of the probe response standby period of the peripheral search device 22 when the probe response standby periods of its own device and the peripheral search device 22 overlap. Waiting, but not limited to this. The search device 21 only transmits the probe request of the probe response reception channel used for receiving the probe response from the information of the probe response reception channel added to the probe request transmitted by the peripheral search device 22. It may be transmitted after the end of the probe response waiting period of 22 and other channels that are not used for receiving the probe response may be transmitted before the end of the probe response waiting period of the neighboring search device 22.

  In the processing of step S002 and step S003 shown in FIG. 5, the search device 21 determines from the own device based on the probe response offset time added to the received probe request and the time when the own device transmits the probe request to all channels. Although it is inferred whether the probe response standby periods of the other search devices 22 overlap, the other search devices 22 transmit to the probe request a probe response that is a response to the probe request by the searched device. The probe response waiting period information may be added as time information including the waiting time information. Accordingly, the search message control unit 44 of the search device 21 can accurately determine the probe response standby period of the other search device 22, and whether the probe response standby period of the own device and the other search device 22 overlaps. It is possible to improve the accuracy of determining whether or not.

  The search message control unit 44 of the search device 21 monitors the probe response transmitted from the search target devices 1 to 11 that is a response to the probe request transmitted from the other search device 22, for example, a probe response standby period. When the number of probe response transmissions within a period defined based on MinChannelTime or MaxChannelTime is equal to or greater than the probe response threshold for determining whether or not to transmit a probe request, it is determined that the surrounding search device 22 is in the probe response standby period. The transmission of the probe request from the own apparatus may be waited. As a result, even when the search device 21 fails to receive the probe request transmitted from the peripheral search device 22, the search device 21 can reduce the collision of messages related to the search by waiting for the probe request to be transmitted. .

  In addition, when the probe responses are retransmitted, the searched devices 1 to 11 may stop the probe response transmission when the set probe response waiting period is exceeded. Thereby, the devices to be searched 1 to 11 can avoid transmitting probe responses after MaxChannelTime and reduce unnecessary transmissions.

  Further, in the wireless communication system that notifies the position information to each other, the search devices 21 and 22 may add the position information of their own devices by the probe request and the searched devices 1 to 11 by the probe response.

  In the first embodiment, channels # 1 to # 11 are described for convenience. However, the channel number and the channel range are not limited. For example, IEEE802.11b / g operating in the 2.4 GHz band is used. It can be applied to all IEEE802.11 standards including IEEE802.11a / n / ac operating in the 5 GHz band, IEEE802.11ad operating in the 60 GHz band, and IEEE802.11ah operating in the 900 MHz band.

  Here, a hardware configuration that realizes the respective configurations of the search devices 21 and 22 and the search target devices 1 to 11 that are wireless communication apparatuses illustrated in FIG. 4 will be described. FIG. 8 is a diagram illustrating a hardware configuration of the search devices 21 and 22 and the devices to be searched 1 to 11 that are wireless communication apparatuses according to the first embodiment. The MAC control unit 43 and the search message control unit 44 are realized by the processor 51 executing a program for each component stored in the memory 52. The transmission unit 41 is realized by the processor 51 and the transmitter 51 executing a program for the transmission unit 41 stored in the memory 52 together with the transmitter 53. The receiver 42 is realized by the processor 51 and the receiver 54 executing a program for the receiver 42 stored in the memory 52 together with the receiver 54. The probe response offset time storage unit 45 is realized by the memory 52. The processor 51, the memory 52, the transmitter 53 and the receiver 54 are connected by a system bus 55. In search devices 21 and 22 and search target devices 1 to 11 which are wireless communication apparatuses, a plurality of processors 51 and a plurality of memories 52 may cooperate to execute the functions of the respective components shown in the block diagram of FIG. The search devices 21 and 22 and the search target devices 1 to 11 that are wireless communication apparatuses can be realized by the hardware configuration shown in FIG. 8, but can be implemented by either software or hardware. For example, the MAC control unit 43 is a control circuit that performs MAC control processing described in IEEE 802.11. The configurations of the search devices 21 and 22 and the devices to be searched 1 to 11 described in the following embodiments can also be realized by the hardware configuration shown in FIG.

  As described above, according to the present embodiment, when a search device receives a probe request from another search device, the search device calculates the other from the probe response offset time added to the probe request received from the other search device. The probe response standby period of the other search device is terminated if the probe response standby period of the local search device is estimated and it is determined that the probe response standby period of the local search device overlaps the probe response standby period of the other search device Until then, the probe request is not sent from the own device. Thereby, by suppressing the number of messages in the device search, it is possible to reduce the collision of messages, and to improve the detection rate while shortening the search time of the search device being searched.

Embodiment 2. FIG.
In the present embodiment, the search device changes its own probe response reception channel when the probe response reception channel is the same as other search devices. The radio communication system 100 and the application example according to the second embodiment are the same as those in FIGS. 1 and 3 of the first embodiment.

  FIG. 9 is a block diagram of a configuration example of the search devices 21 and 22 that are the search wireless communication apparatuses according to the second embodiment and the search target devices 1 to 11 that are the search wireless communication apparatuses. The configuration shown in FIG. 9 is an example, and the present invention is not limited to this. In addition, here, the search devices 21 and 22 and the search target devices 1 to 11 have the same configuration, but this is an example and the present invention is not limited to this. For convenience, reference numeral 21 is assigned to the search device 21 in FIG.

  The search devices 21 and 22 and the devices to be searched 1 to 11 have a probe response reception channel storage unit 46 added to the configuration of the first embodiment shown in FIG. The probe response reception channel storage unit 46 which is a channel information storage unit is information on the probe response reception channel added to the probe request transmitted by the peripheral search device 22, that is, the probe request transmitted from another search device. The channel information which is the information of the probe response reception channel of the channel used when another search device receives the probe response added to the is stored. In addition to the operation of the first embodiment, the search message control unit 44 stores the probe response reception channel information added to the probe request transmitted by the peripheral search device 22 in the probe response reception channel storage unit 46, Based on the time information, it is determined that the probe response standby period when the own device performs a search overlaps with the probe response standby period of another search device, and the probe response reception channel of the own device is determined based on the channel information. When the probe response reception channel of the other search device is the same, the probe response reception channel of the own device is changed.

  Next, a search operation in which the search devices 21 and 22 in the second embodiment search for the search target devices 1 to 11 will be described. As an example, the search device 21 will be described, but the search device 22 performs a similar search operation.

  FIG. 10 is a flowchart of a search operation process in which the search device 21 according to the second embodiment searches for the search target devices 1 to 11. In the search device that has received the probe request of the peripheral search device, the search message control unit 44 causes the probe response offset time storage unit 45 to store the probe response offset time information added to the probe request of the peripheral search device. The probe response reception channel storage unit 46 stores information on the probe response reception channel added to the probe request of the surrounding search device.

  (Steps S101 to S102) Since this is the same as the processing in steps S001 to S002 of the first embodiment shown in FIG.

  (Step S <b> 103) In the search device 21, the search message control unit 44 causes the probe response reception channel storage unit 46 to store information on the probe response reception channel added to the probe request of the other search device 22. The search message control unit 44 of the search device 21 confirms whether or not the probe response reception channel set by the own device is the same as the probe response reception channel of another search device 22 having a duplicate probe response standby period. When the probe response reception channel is the same (step S103: Yes), the search device 21 proceeds to the process of step S104, and when the probe response reception channel is different (step S103: No), the search device 21 proceeds to the process of step S105.

  (Step S104) The search message control unit 44 of the search device 21 changes the probe response reception channel of its own device from the channels that can be used by its own device to the probe response reception channel of another search device 22 in which the probe response standby period overlaps. Change to any channel except. If there is no selectable channel, the search message control unit 44 of the search device 21 sets an arbitrary channel that is least used by other search devices as the probe response reception channel of the own device.

  (Steps S105 to S117) Since this is the same as the processing in steps S004 to S016 of the first embodiment shown in FIG.

  The processing of the devices to be searched 1 to 11 in the second embodiment is the same as the processing of the flowchart of the first embodiment shown in FIG.

  FIG. 11 is a diagram illustrating transmission / reception timings of search messages between the search devices 21 and 22 and the search target devices 1, 6, and 11 according to the second embodiment. The operation channel of the search device 21 is channel # 1, the operation channel of the search device 22 is channel # 6, and the operation channels of the search target devices 1 to 11 are channels # 1 to # 11 which are the same as the codes of the own device.

  The search devices 21 and 22 transmit probe requests in order from channel # 1 to channel # 11, and search for search target devices 1 to 11. First, the search device 22 sets channel # 6 to the probe response reception channel and starts transmitting probe requests in order from channel # 1. The search device 21 receives the probe request transmitted from the search device 22 to the channel # 6.

  Since the search device 21 determines from the probe response offset time added to the received probe request that the probe response standby period set by the own device and the probe response standby period of the search device 22 overlap, the search device 21 further Confirms that the probe response reception channel set by and the probe response reception channel of the search device 22 overlap. The search device 21 recognizes that the channel # 6 of the probe response reception channel set by the own device overlaps with the channel # 6 of the probe response reception channel of the search device 22. The search device 21 changes the probe response reception channel from channel # 6 to channel # 1 and transmits a probe request.

  That is, in the search device 21, the search message control unit 44 determines that the probe response standby period when the device itself performs a search overlaps with the probe response standby period of another search wireless device 22 based on the probe response offset time. In addition, based on the channel information, when the probe response reception channel of the own device and the probe response reception channel of the other search device 22 are the same, the probe response reception channel of the own device is changed. The subsequent processing is the same as the processing of the first embodiment shown in FIG.

  As described above, in the present embodiment, the wireless communication system can reduce the collision of search messages such as probe requests and probe responses and improve the device detection rate even in an environment where a plurality of search devices exist. . Furthermore, in the wireless communication system, an effect of shortening the search time can be obtained by avoiding duplication of the peripheral search device and the probe response reception channel.

  In FIG. 11, the search devices 21 and 22 transmit probe requests to channel # 1 to channel # 11 in order, but the probe request transmission order may be random.

  Further, in the flowchart shown in FIG. 10, the search device 21 overlaps the probe response waiting periods of the own device and the other search device 22 in step S102, and the probe response of the own device and the other search device 22 in step S103. Only when the reception channel is the same, the probe response reception channel of the own apparatus is changed, but the process of step S102 may be omitted.

  In addition, when the search devices 21 and 22 receive the probe request of the other search device after transmitting the probe request from the own device, the search devices 21 and 22 receive the probe response of the other search device added to the probe request of the other search device. Channel information may be held, and when the device itself transmits a probe request next time, a channel other than that used by another search device may be selected. That is, when the search message control unit 44 next searches for the devices to be searched 1 to 11, based on the channel information stored in the probe response reception channel information storage unit 46, the probe response reception of the other search devices 22 is performed. A probe response reception channel different from the channel is set. Thereby, the search message control unit 44 can reduce the probability that the probe response reception channels overlap.

  In addition, the search devices 21 and 22 periodically monitor the communication status of each channel, that is, the usage status of each channel, and reduce the priority of a channel with a high usage status. You may change it. That is, the search message control unit 44 monitors the usage status of each channel, and sets the probe response reception channel of the own device based on the usage status of each channel. Thereby, the search message control unit 44 can lower the collision probability in the channel.

  Further, the search devices 21 and 22 may change the priority when selecting the probe response reception channel by weighting each channel based on the information of the probe response reception channel added to the probe request received in the past. That is, when the search message control unit 44 holds the probe response reception channel information of other search devices received during the period specified in the probe response reception channel storage unit 46, the search message control unit 44 sets the probe response reception channel for each channel. The probe response reception channel of the own apparatus is set based on the number of times used. Thereby, the search message control unit 44 can reduce the overlap probability of the probe response reception channel.

  In the second embodiment, channels # 1 to # 11 are described for convenience. However, the channel number and the channel range are not limited. For example, IEEE802.11b / g operating in the 2.4 GHz band is used. It can be applied to all IEEE802.11 standards including IEEE802.11a / n / ac operating in the 5 GHz band, IEEE802.11ad operating in the 60 GHz band, and IEEE802.11ah operating in the 900 MHz band.

  As described above, according to the present embodiment, a search device receives a probe request from another search device, and the probe response standby period of its own search device and the probe response standby period of another search device are If it is determined that there is a duplication, the probe response reception channel of its own device and the probe response reception channel of the other search device are confirmed to be the same. If they are the same, the probe response reception channel of its own device is changed. . As a result, the same effect as in the first embodiment can be obtained, and further, the effect of shortening the search time can be obtained by avoiding the overlap between the surrounding search device and the probe response reception channel.

Embodiment 3 FIG.
In the present embodiment, a method for reducing the number of probe responses transmitted by the devices to be searched 1 to 11 and confirmation messages transmitted by the search devices 21 and 22 will be described. The radio communication system and the application example according to the third embodiment are the same as those in FIGS. 1 and 3 of the first embodiment.

  FIG. 12 is a block diagram of a configuration example of the search devices 21 and 22 and the devices to be searched 1 to 11 that are wireless communication apparatuses according to the third embodiment. The configuration shown in FIG. 12 is an example, and the present invention is not limited to this. In addition, here, the search devices 21 and 22 and the search target devices 1 to 11 have the same configuration, but this is an example and the present invention is not limited to this. For convenience, reference numeral 21 is assigned to the search device 21 in FIG.

  The search devices 21 and 22 and the devices to be searched 1 to 11 add a probe response reception storage unit 47 to the wireless communication apparatus of the second embodiment shown in FIG. The probe response reception storage unit 47, which is a response reception storage unit, stores the identification information of the search target device that is the source of the probe response received during the probe response reception period when the search device is a search device. The identification information of the search device to which the probe response transmitted by the apparatus has arrived, that is, the information on the transmission source of the probe response received by the search device that is the transmission confirmation transmission source, If the information is added, the information of the search device that is the transmission source of the delivery confirmation is stored.

  In addition to the operation of the second embodiment, the search message control unit 44, in the case of a search device, when receiving a probe response during the probe response reception period, stores information on the search target device that is the source of the probe response. 47, when transmitting a delivery confirmation that is a response to the received probe response addressed to the own apparatus, the information on the search target device stored in the probe response reception storage unit 47 is added to the delivery confirmation. In addition, the search message control unit 44, in the case of the searched device, confirms the transmission source information of the probe response received by the searching device that is the transmission confirmation transmission source in the confirmation of the delivery addressed to the other searched device received. When the information is added, the information of the search device that is the transmission confirmation transmission source is stored in the probe response reception storage unit 47. When the probe request is received from the search device, the information is stored in the probe response reception storage unit 47. A probe response is transmitted to the search device except the search device that is the transmission source of the delivery confirmation.

  Next, a search operation in which the search devices 21 and 22 in the third embodiment search for the search target devices 1 to 11 will be described. As an example, the search device 21 will be described, but the search device 22 performs a similar search operation.

  FIG. 13 is a flowchart of a search operation process in which the search device 21 according to the third embodiment searches for the search target devices 1 to 11. In the search device that has received the probe request of the peripheral search device, the search message control unit 44 causes the probe response offset time storage unit 45 to store the probe response offset time information added to the probe request of the peripheral search device. The probe response reception channel storage unit 46 stores information on the probe response reception channel added to the probe request of the surrounding search device.

  (Step S <b> 201) The search device 21 that searches for nearby search target devices 1 to 11 determines whether or not the own device starts the search. When the search device 21 starts the search (step S201: Yes), the search device 21 proceeds to step S202. When the search device 21 does not start the search (step S201: No), the search device 21 proceeds to step S206.

  (Step S202) The search device 21 changes the operation channel to the channel for starting the search for the search target device defined in the wireless communication system 100, here, the channel # 1.

  (Step S203) The search device 21 performs carrier sense similar to the process in step S005 of the first embodiment, and waits for the back-off time.

  (Step S204) The search device 21 confirms whether or not the probe request of another search device 22 has been received during the carrier sense and the back-off period of Step S203. When the search device 21 receives a probe request from another search device 22 (step S204: Yes), the search device 21 proceeds to the process of step S208, and does not receive a probe request from another search device 22 (step S204: No). ) Proceeds to the process of step S205. When the search device 21 receives a probe request transmitted from another search device 22, the search message control unit 44 uses the probe response offset time information added to the probe request of the other search device 22. Information on the probe response reception channel stored in the probe response offset time storage unit 45 and added to the probe request of the other search device 22 is stored in the probe response reception channel storage unit 46.

  (Step S205) The search device 21 broadcasts a probe request to which the probe response reception channel and the probe response offset time are added using the operation channel changed in Step S202 of the own device. Here, in the search device 21, when the search message control unit 44 has not received a probe request from another search device 22 before transmitting a probe request from its own device, the search message control unit 44 is directed to an arbitrary probe response reception channel and all channels. The probe response offset time after the time to complete the probe request transmission is set. Further, in the search device 21, when the search message control unit 44 receives a probe request from another search device 22 before transmitting a probe request from the own device, the probe response offset to be added to the probe request transmitted from the own device. The probe response offset time added to the probe request of the other search device 22 received first, which is stored in the probe response offset time storage unit 45, and the probe response reception channel storage unit 46. The probe response reception channel added to the probe request of the other search device 22 received first is stored.

  (Step S <b> 206) When the search device 21 does not start a search, the search device 21 waits until a probe request from another search device 22 is received.

  (Step S207) Upon receiving a probe request from another search device 22, the search device 21 specifies a channel for starting a search for a device to be searched, which is defined by the wireless communication system 100, here, channel # 1 Change to In the search device 21, when the probe request transmitted from the other search device 22 is received, the search message control unit 44 is added to the probe request of the other search device 22 as in the process of step S204. The probe response offset time information is stored in the probe response offset time storage unit 45, and the probe response reception channel information added to the probe request of the other search device 22 is stored in the probe response reception channel storage unit 46.

  (Step S208) In the channel # 1 changed in step S202 or step S207, the search device 21 waits until the transmission ends when another search device 22 is transmitting a probe request.

  (Step S209) The search device 21 performs carrier sense similar to step S005 in the first embodiment, and waits for the backoff time.

  (Step S210) Since the search device 21 can transmit after the process of Step S209, the shortest probe set by the other search device 22 added to the probe request first received in the current search cycle. It is determined whether or not the probe request of the own apparatus can be transmitted to all channels by the response offset time. When the search device 21 determines that the transmission can be completed (step S210: Yes), the search device 21 proceeds to step S205. When the search device 21 determines that the transmission cannot be completed (step S210: No), the search device 21 proceeds to step S211.

  (Step S211) The search device 21 waits until the end of the probe response waiting period of the other search devices 22. The search device 21 estimates the probe request standby period of the other search device 22 from the offset time of the probe response included in the probe request of the other search device 22 and the time required for receiving the probe response. The process of estimating the probe request waiting period of another search device 22 in the search device 21 is the same as the method described in the process of step S002 of the flowchart shown in FIG.

  (Step S212) Similar to the process of step S004 of the first embodiment, the search device 21 broadcasts a probe request to all available channels while changing the operation channel. Here, it is assumed that all usable channels are 11 channels of channels # 1 to # 11. The search device 21 broadcasts a probe request by changing the operation channel in the prescribed channel order. Note that the search device 21 omits the transmission processing of the channel for which the probe request has already been transmitted in step S205 in the channel changed in step S202.

  (Step S213) The search device 21 performs carrier sense similar to the process in step S005 of the first embodiment, and waits for the backoff time. The search device 21 proceeds to the process of step S214 after transmission is possible.

  (Step S214) The search device 21 performs a probe request transmission process similar to the process of step S205 described above.

  (Step S215) The search device 21 sets the operation channel in steps S205 and S214 when the search for channels # 1 to # 11 is completed in steps S205 and S212 to S214, as in the process of step S007 of the first embodiment. Change to the received probe response channel.

  (Steps S216 to S219) Since this is the same as the processing in steps S008 to S011 of the first embodiment, the description thereof is omitted.

  (Step S220) The search device 21 confirms whether or not a probe response has been received during the probe response standby period, as in the process of step S012 of the first embodiment. When the search device 21 receives the probe response (step S220: Yes), the search device 21 proceeds to the process of step S221. When the search device 21 does not receive the probe response (step S220: No), the process of steps S221 to S225 is omitted.

  (Step S221) In the search device 21 that has received the probe response, the search message control unit 44 causes the probe response reception storage unit 47 to store the identifier information of the probe response transmission device, that is, the search target device that is the probe response transmission source. . The identifier may be any identifier that can identify the searched device such as a MAC address.

  (Step S222) The search device 21 confirms the destination information added to the probe response and confirms whether or not the probe response is addressed to itself. When the probe device 21 is a probe response addressed to the own device (step S222: Yes), the search device 21 proceeds to the process of step S223, and when it is not a probe response addressed to the own device (step S222: No), the probe device 21 continues the probe response reception process. .

  (Step S223) The search device 21 confirms whether or not the received probe response is the first probe response received within the MinChannelTime within the probe response standby period, as in the process of step S013 of the first embodiment. . If the probe response is the first probe response received within MinChannelTime (step S223: Yes), the search device 21 proceeds to the process of step S224. Otherwise (step S223: No), the search device 21 proceeds to the process of step S225.

  (Step S224) Since this is the same as the process of Step S014 of Embodiment 1, the description thereof is omitted.

  (Step S225) The search device 21 adds to the destination information the identifier of the search target device that is the source of the probe response stored in the probe response reception storage unit 47. The identifier of the search target device that is the transmission source of all received probe responses is added, and the delivery confirmation is broadcast.

  (Step S226) Since this is the same as the processing in step S016 of the first embodiment, description thereof is omitted.

  In the flowchart of FIG. 13, the order of steps S215 and S216 may be interchanged.

  Next, operations of the devices to be searched 1 to 11 when the search devices 21 and 22 in the third embodiment search are described. As an example, the search target device 1 will be described, but the search target devices 2 to 11 perform the same search operation. FIG. 14 is a flowchart of an operation process of the search target device 1 when the search devices 21 and 22 according to the third embodiment search.

  (Steps S601 to S604) Since they are the same as the processing of Steps S501 to S503 and S505 of the first embodiment, the description thereof is omitted.

  (Step S605) The probed device 1 has an unprocessed probe request that does not return a probe response among the probe requests in which the probe response reception channel and the probe response offset time are stored in Step S602, or in Step S607 described later. It is confirmed whether or not there is an unprocessed probe request for which the arrival of the probe response of the own device has not been confirmed in the processing. The searched device 1 proceeds to the process of step S606 when there is an unprocessed probe request (step S605: Yes), and proceeds to the process of step S614 when there is no unprocessed probe request (step S605: No).

  (Step S606) The to-be-searched device 1 confirms whether the destination has been added with the identifier of another to-be-searched device, that is, whether or not a delivery confirmation addressed to another to-be-searched device has been received. When the search target device 1 receives a delivery confirmation addressed to another search target device (step S606: Yes), the process proceeds to the process of step S607, and a search confirmation addressed to another search target device has not been received (step S606). In step S606: No), the process proceeds to step S608.

  (Step S607) In the search target device 1, the search message control unit 44 adds the source response of all probe responses received by the search device that is added to the received delivery confirmation and that is the source device of the delivery confirmation. Check the identifier of the discovery device. When the identifier of the own device is included, the search message control unit 44 causes the probe response reception storage unit 47 to store information on the search device that is the transmission source of the delivery confirmation. The to-be-searched device 1 determines that the search device stored in the probe response reception storage unit 47 has received the probe response transmitted by itself or another search device, and is stored in the probe response reception storage unit 47. The probe response to the searching device is omitted.

  (Step S608) The to-be-searched device 1 performs carrier sense by the process similar to step S005 of Embodiment 1, and waits for a back-off time. The search target device 1 proceeds to step S609 after transmission is enabled.

  (Step S609) The to-be-searched device 1 is the source of any probe request except for the search device of the delivery confirmation transmitting device stored in the process of step S607 among the search devices of the source of the probe request received in step S601. A probe response with the search device added as a destination is broadcast. The search target device 1 broadcasts the destination field of the MAC header, for example, the Address 1 field of Non-Patent Document 1, and the MAC address of the search device that is the transmission source of the probe request that is the destination is another field or field of the MAC header. Add and add.

  (Step S610) The to-be-searched device 1 confirms whether or not the device itself has been added to the destination, that is, whether or not a delivery confirmation addressed to the device itself has been received. When the search target device 1 receives a delivery confirmation addressed to itself (step S610: Yes), the process proceeds to step S611. If not received (step S610: NO), the search target apparatus 1 proceeds to step S612.

  (Step S611) In the searched device 1, the search message control unit 44 sets the search device that is the transmission source of the delivery confirmation as the search device that has completed the processing for the probe request, and probes the information on the search device that is the transmission source of the delivery confirmation. The response reception storage unit 47 stores the response.

  (Step S612) The to-be-searched device 1 confirms whether or not a delivery confirmation reception timeout has occurred. The searched device 1 increments the number of times of retransmission when the delivery confirmation reception timeout is reached (step S612: Yes), and proceeds to the process of step S613. When the delivery confirmation reception timeout is not reached (step S612: No) ) Continues to wait for receipt of delivery confirmation in the process of step S610.

  (Step S613) The to-be-searched device 1 checks whether or not the number of retransmissions of the probe response is equal to or less than a threshold value of the number of retransmissions. If the search target device 1 is equal to or less than the threshold value (step S613: Yes), the process proceeds to step S608, and the probe response is retransmitted. If the search target device 1 exceeds the threshold value (step S613: No), the probe response transmission process to the corresponding search device is determined to have failed, and the process proceeds to step S605 to receive the probe request received from another search device. Continue processing.

  (Step S614) Since this is the same as the processing of Step S511 of Embodiment 1, the description thereof is omitted.

  FIG. 15 is a diagram illustrating transmission / reception timings of search messages between the search devices 21 and 22 and the search target devices 1, 6, and 11 according to the third embodiment. The operation channel of the search device 21 is channel # 1, the operation channel of the search device 22 is channel # 6, and the operation channels of the search target devices 1 to 11 are channels # 1 to # 11 which are the same as the codes of the own device.

  The search devices 21 and 22 transmit probe requests in order from channel # 1 to channel # 11, and search for search target devices 1 to 11.

  First, the search device 21 that transmits a probe request at the beginning of the search cycle transmits a probe request to which a channel # 1 that is a probe response reception channel and a probe response offset time are added. At this time, the search device 22 and the searched devices 1 to 11 that have received the probe request of the search device 21 store the probe response reception channel and the probe response offset time.

  Next, the search device 22 that transmits the probe request transmits the probe request to which the probe response reception channel set by the search device 21 and the probe response offset time at which the probe response reception start is the same time are added.

  After the probe response offset time, the search devices 21 and 22 and the searched devices 1 to 11 change the operation channel to the probe response reception channel.

  The to-be-searched devices 1 to 11 that have received the probe request transmit the probe response after the probe response offset time becomes possible due to carrier sense and back-off time waiting at an arbitrary timing. In the process of FIG. 7 shown in the first embodiment, when the search target device 1 broadcasts the probe response (1) destined for the search device 21, the search device 21 and the search device 22 receive the broadcast response. The search device 21 as the destination transmits an acknowledgment (2) to which the identifiers of all the pedestrians that have received the probe response during the probe response reception period, in this case, the identifier of the searched device 1 are added. The searched devices 1, 6 and 11 receive the delivery confirmation (2) transmitted from the search device 21.

  Next, the search target device 6 broadcasts a probe response (3) destined for the search device 22. The search device 22 transmits a delivery confirmation (4) to which the identifiers of all the pedestrians that have received the probe response, here, the identifiers of the search target devices 1 and 6 are added. The searched devices 1 and 11 receive the delivery confirmation (4) transmitted from the searching device 22.

  The to-be-searched device 1 determines that the probe response of its own device has already reached the search device 22 from the identifier of its own device included in the delivery confirmation (4), and omits the probe response transmission to the search device 22. Similarly, the search target device 6 omits the probe response transmission to the search device 21 by the delivery confirmation (6) from the search target device 11 to the search device 21 to the probe response (5). The searched device 11 has not received the delivery confirmation to which the identifier of the own device has been added from the searching device 22. Therefore, the searched device 11 transmits a probe response (7) to the searching device 22, and the searching device 22 transmits a delivery confirmation (8).

  Specifically, in the probe response (1) from the search device 1, the search device 22 cannot actually confirm whether or not the search device 1 has received the probe request transmitted from its own device. However, since the search device 22 has acquired the information necessary for the device search from the search target device 1 by the probe response (1), it is not necessary to transmit the probe response from the search target device 1 again. Therefore, the search device 22 adds information on the search target device 1 to the delivery confirmation (4). Thereby, the searchee device 1 can omit the transmission of the probe response to the search device 22.

  Thus, in the present embodiment, in the wireless communication system, the number of transmitted / received packets in the probe response reception period can be reduced, and the search target device detection rate can be improved. In the wireless communication system, in particular, when the number of search devices increases, the effect of reducing the number of transmitted / received packets increases.

  Note that the probe response transmission timing by the device to be searched is set arbitrarily by carrier sense and back-off time standby, but is not limited to this. In the search device that transmits the probe request, the search message control unit 44 adjusts the probe response offset time for each channel, shifts the probe response reception timing for each channel by changing the probe response offset time for each channel, Collisions caused by backoff can also be reduced.

  In the third embodiment, channels # 1 to # 11 are described for convenience. However, the channel number and the channel range are not limited. For example, IEEE802.11b / g operating in the 2.4 GHz band is used. It is possible to apply to all IEEE802.11 standards including IEEE802.11a / n / ac that operates in the / n, 5 GHz band, IEEE802.11ad that operates in the 60 GHz band, and IEEE802.11ah that operates in the 900 MHz band.

  As described above, according to the present embodiment, the search device adds the information of the search target device that is the source of the received probe response to the delivery confirmation and transmits it, and the search target device transmits another search target device. When the delivery confirmation addressed to the device is received and the information of the own device is added to the delivery confirmation, the transmission of the probe response is omitted. Thereby, even when the number of search devices is large, the number of messages transmitted and received between the search device and the search target device can be reduced, and the detection rate of the search target device can be improved.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  1,2,3,4,5,6,7,8,9,10,11 Searched device, 21,22 Search device, 30 Car, 41 Transmitter, 42 Receiver, 43 MAC controller, 44 Search message Control unit, 45 probe response offset time storage unit, 46 probe response reception channel storage unit, 47 probe response reception storage unit.

Claims (13)

A waiting time that is added to a probe request transmitted from another searching wireless communication device that searches for a searched wireless communication device and when the searched wireless communication device transmits a probe response that is a response to the probe request. A time information storage unit for storing time information including the information of
When the probe request is received from the other search wireless communication device, the time information is stored in the time information storage unit,
Based on the time information, when it is determined that the probe response standby period, which is the reception period of the probe response when the own apparatus searches, overlaps with the probe response standby period of the other search wireless communication apparatus, A search message control unit that waits until the probe response waiting period of the other search wireless communication device ends transmission of the probe request;
A search wireless communication apparatus comprising: A waiting time that is added to a probe request transmitted from another searching wireless communication device that searches for a searched wireless communication device and when the searched wireless communication device transmits a probe response that is a response to the probe request. A time information storage unit for storing time information including the information of
Channel information which is added to the probe request transmitted from the other search radio communication device and is information of the probe response reception channel of the channel used when the other search radio communication device receives the probe response. A channel information storage unit for storing;
When the probe request is received from the other search radio communication device, the time information is stored in the time information storage unit, the channel information is stored in the channel information storage unit,
Based on the time information, it is determined that the probe response standby period when the own device performs a search overlaps with the probe response standby period of the other search wireless communication device, and based on the channel information, When the probe response reception channel and the probe response reception channel of the other search radio communication device are the same, a search message control unit that changes the probe response reception channel of the own device;
A search wireless communication apparatus comprising: The search message control unit, based on a probe response offset time of a waiting time until the searched wireless communication device transmits a probe response, which is the time information, and a reception period for receiving the probe response, Estimating the probe response standby period of the search radio communication device, and determining whether the estimated probe response standby period of the other search radio communication device and the probe response standby period of the own device overlap,
The search wireless communication apparatus according to claim 1 or 2, wherein The search message control unit determines whether the probe response standby period of the other search wireless communication device that is the time information overlaps with the probe response standby period of the own device,
The search wireless communication apparatus according to claim 1 or 2, wherein The search message control unit monitors the probe response transmitted from the searched radio communication device, which is a response to the probe request transmitted from the other search radio communication device, and within a specified period. If the number of probe response transmissions is greater than or equal to the probe response threshold for determining whether or not to transmit a probe request, the probe request transmission from its own device is waited.
The search radio communication apparatus according to claim 1, wherein When the search message control unit next searches for the searched radio communication device, the search message control unit is different from the probe response reception channel of the other search radio communication device based on the channel information stored in the channel information storage unit. Set the probe response reception channel,
The search radio communication apparatus according to claim 2. The search message control unit monitors the usage status of each channel, and sets the probe response reception channel of its own device based on the usage status of each channel.
The search wireless communication apparatus according to claim 2 or 6, wherein When holding the channel information of the other search radio communication device received in the period specified in the channel information storage unit,
The search message control unit sets its own probe response reception channel based on the number of times used for the probe response reception channel for each channel.
The search wireless communication device according to claim 2, 6 or 7. A waiting time that is added to a probe request transmitted from another searching wireless communication device that searches for a searched wireless communication device and when the searched wireless communication device transmits a probe response that is a response to the probe request. A time information storage unit for storing information of the probe response offset time,
Channel information which is added to the probe request transmitted from the other search radio communication device and is information of the probe response reception channel of the channel used when the other search radio communication device receives the probe response. A channel information storage unit for storing;
A response reception storage unit that stores information of the searched wireless communication device that is the transmission source of the received probe response;
When the probe request is received from the other search radio communication device, the time information is stored in the time information storage unit, the channel information is stored in the channel information storage unit, and the probe response is received Store the information of the searched wireless communication device of the probe response transmission source in the response reception storage unit,
When transmitting a delivery confirmation that is a response to the received probe response addressed to the own device, a search message control unit that adds information on the searched wireless communication device stored in the response reception storage unit to the delivery confirmation;
A search wireless communication apparatus comprising: The search message control unit transmits the probe request in the order of defined channels.
The search radio | wireless communication apparatus of Claim 9 characterized by the above-mentioned. The search message control unit receives a probe response offset time and a probe response to be added to the probe request transmitted from the own device when the probe request is received from the other searching radio communication device before transmitting the probe request from the own device. The channel is received for the first time stored in the channel information storage unit, and the probe response offset time added to the probe request of the other search radio communication device received first stored in the time information storage unit To the probe response reception channel added to the probe request of the other search wireless communication device.
The search wireless communication apparatus according to claim 9 or 10, characterized in that The search message control unit has a different probe response offset time for each channel,
The search wireless communication apparatus according to claim 9, 10 or 11. The searching wireless communication device transmits a probe request when searching for the searched wireless communication device, and the searched wireless communication device receiving the probe request transmits a probe response to the searching wireless communication device and receives the probe response. When the search wireless communication device transmits a delivery confirmation to the searched wireless communication device that transmitted the probe response,
In the delivery confirmation addressed to another searched radio communication device, if the information of the own device is added to the source information of the probe response received by the search radio communication device of the delivery confirmation transmission source, the delivery confirmation A response reception storage unit that stores information of the search wireless communication device of the transmission source of
When the information of the own device is added to the source information of the probe response received by the search wireless communication device that is the transmission source of the delivery confirmation, in the received delivery confirmation addressed to the other searched wireless communication device, Storing the information of the search wireless communication device of the transmission source of the delivery confirmation in the response reception storage unit,
Search message control for transmitting a probe response to a search radio communication device excluding a search radio communication device that is a transmission source of the delivery confirmation stored in the response reception storage unit when a probe request is received from the search radio communication device And
A searched wireless communication apparatus comprising:

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