JP2017208580A - Radio communication system, on-vehicle radio communication system, and access point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement a mechanism in a system requiring monitoring of the existence of an interference signal prior to starting use of a frequency channel, the mechanism being capable of quickly starting communication and reducing power consumption in a battery.SOLUTION: There is provided an access point for operating so that the access point, after input of a first trigger signal, switches an interference monitoring unit from a stop mode to an interference monitoring mode to make the interference monitoring unit detect a frequency channel in which no interference signal exists; (2) when a second trigger signal is input subsequently to the first trigger signal, switches the interference monitoring unit from the interference monitoring mode to a communication mode and supplies power to a radio communication unit to make the radio communication unit start communication with a client; and (3) when a third trigger signal is input subsequently to the second trigger signal, switches the interference monitoring unit from the communication mode to the interference monitoring mode and stops power supply to the radio communication unit.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an access point that operates by receiving power sharing from a battery, and a wireless communication system realized by using the access point.

  With the development of wireless communication technology, available frequency bands are imminent. In particular, frequency bands that do not require a radio station license are already used by various radio communication systems. Therefore, when a new frequency band is released to a band that does not require a radio station license, it is a necessary condition that no interference is given to a radio system that uses the existing frequency band.

  For example, in recent years, the 5 GHz band has become available for wireless LAN. However, the band called W53 from 5.25 GHz to 5.35 GHz and the band called W56 from 5.47 GHz to 5.725 GHz are bands previously used by mobile radars for ships, aircraft, military, etc. and fixed radars for weather. is there. For this reason, there is a possibility of interference between these devices and newly available wireless devices.

  Therefore, in Non-Patent Document 1, as a method of avoiding interference with a conventional (primary) wireless device, the presence or absence of a radio wave (interference signal) output from the primary wireless device is monitored for a certain period of time before starting communication. It is stipulated that communication can be started on the corresponding frequency channel only when the radio wave does not exist.

"Broadband Mobile Access System (CSMA) Standard ARIB STD-T71 5.2 Edition", Radio Industry Association, July 2012, P.13-P.15

  For example, an access point used for a 5 GHz wireless LAN is obliged to perform the above-described interference signal monitoring for 60 seconds before the start of communication. In addition, the access point is obliged to stop wireless transmission on the corresponding frequency channel within a certain time when an interference signal is detected during operation.

  However, in this type of access point, the time from turning on the power switch that turns on all functions until communication is started (the time required to detect a frequency channel in which no interference signal is present) becomes longer. In order to start communication without waiting time, a method of operating all the functions of the access point in an on state even during a period when data communication is not performed is effective. However, with this method, power is always consumed in all functions of the access point. In particular, when the power source is a battery instead of an AC power source, operating the power switch while the power switch is turned on shortens the battery life.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. The present specification includes a plurality of means for solving the above-described problems. For example, the present specification includes one or a plurality of clients, an access point that operates by receiving power supply from a battery, and a frequency channel. In a wireless communication system that requires monitoring for the presence or absence of interference signals prior to the start of use, the access point mode controller (1) after the first trigger signal is input, the interference monitoring unit is monitored for interference from the stop mode. The mode is switched to detect a frequency channel in which no interference signal exists. (2) When the second trigger signal is input following the first trigger signal, the interference monitoring unit is switched from the interference monitoring mode to the communication mode. When power is supplied to the wireless communication unit to start communication with the client, and (3) when the third trigger signal is input following the second trigger signal, the interference monitoring unit It operates to stop the supply of power to the radio communication unit with switching from communication mode to the interference monitoring mode.

  According to the present invention, although the system requires interference monitoring before using the frequency channel, communication can be started without waiting time after the access point power switch is switched from the off state to the on state, and the battery can be started. A mechanism that consumes less power can be realized. Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

The figure which shows the structural example of the radio | wireless communications system which concerns on a 1st form example. The figure which shows the function structural example of an access point and a client. The figure which shows the other function structural example of an access point and a client. The figure explaining the mode transition of an access point. The flowchart explaining the operation | movement in interference monitoring mode. The flowchart explaining the transition operation from interference monitoring mode to communication mode. The flowchart explaining operation | movement of the client performed prior to the start of communication. The figure explaining the example of the protocol which enables a high-speed association. The chart explaining the relation between an external trigger signal and execution operation. The chart explaining other relations of an external trigger signal and execution operation. The figure explaining the change operation of the frequency channel at the time of interference detection. The figure explaining the example which carries out interference monitoring of the several frequency channel in parallel. The figure which shows the structural example of the radio | wireless communications system which concerns on a 2nd form example. The figure explaining the example of a time sequence of an access point. The figure which shows the structural example of the radio | wireless communications system which concerns on a 3rd form example. The figure explaining the example of a time sequence of an access point.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment of the present invention is not limited to the embodiments described later, and various modifications are possible within the scope of the technical idea.

(1) Example 1
(1-1) System Configuration FIG. 1 shows a configuration example of a wireless communication system. The wireless communication system according to the present embodiment includes an access point 1, one or a plurality of clients 2, and a wireless network 3 that connects them. The wireless network 3 includes upstream communication transmitted from the client 2 to the access point 1 and downstream communication transmitted from the access point 1 to each client 2. The access point 1 and the client 2 have a so-called parent device and child device relationship, and the access point 1 controls communication with the client 2.

(1-2) Configuration of Access Point and Client FIG. 2 shows a functional configuration of the access point 1 and the client 2. The client 2 includes a communication wireless module 21, a processor (not shown), and electronic components and modules corresponding to the client 2. The access point 1 includes a processor 11, a communication wireless module 19, and an interference monitoring module 20. However, this configuration is merely an example for realizing the functions described below, and does not limit the means for realizing the present invention. The processor 11 can be configured by, for example, an FPGA or an ASIC, and a part of the function may be provided to the communication wireless module 19.

  The processor 11 includes a transmission / reception processing unit 12, a communication control unit 13, a time measurement unit 14, an interference recording unit 15, an interference monitoring unit 16, a mode control unit 17, and an interference monitoring control unit 18. The processor 11 is connected to an external trigger signal input line and a power line from a battery (not shown). The power line here is a constant power line. For this reason, as long as the battery is connected to the access point 1, power is supplied to the processor 11. However, the supply of power is different from the fact that all the functions of the processor 11 are effective. In the case of the present embodiment, the function related to communication is not effective unless a command for instructing execution of communication (data transmission / reception) or an external trigger signal associated with a state where communication is possible is given. As the external trigger signal, for example, a signal given from a real-time timer (external device), a signal generated in conjunction with the operation of switches, and other signals are assumed. The external trigger signal is used for switching the operation mode of the access point 1. The type and cause of the external trigger signal depends on the system environment to which it is applied. Note that one or more signal lines are used to input the external trigger signal. Only one state / command may be transmitted using one signal line, or a plurality of states (for example, ON and OFF) may be transmitted using one signal line.

  The communication wireless module 19 provides a function for wirelessly transmitting and receiving data to and from the client 2. The interference monitoring module 20 provides a function of monitoring whether or not an interference signal from another wireless device exists in the frequency channel set as a monitoring target. The other wireless device here is the primary device described above. For this reason, the interference monitoring module 20 has only a reception function. The transmission / reception processing unit 12 is a functional unit that processes data transmitted / received through the communication wireless module 19. The communication control unit 13 is a functional unit that controls wireless communication executed by the communication wireless module 19. Specifically, access control, frequency channel setting, and the like are controlled. The interference monitoring unit 16 is a functional unit that uses the interference monitoring module 20 to monitor interference with other wireless devices. The interference monitoring unit 16 passes the monitoring result to the time measuring unit 14 and the interference recording unit 15. The interference monitoring controller 18 is a functional unit that controls setting of a frequency channel in the interference monitoring module 20. The mode control unit 17 is a functional unit that performs mode control of the entire apparatus and accompanying power control in accordance with the external trigger signal, the data communication result, and the interference monitoring result. For example, power supply to the interference monitoring module 20 is controlled.

  FIG. 3 shows another functional configuration of the access point. In FIG. 3, parts corresponding to those in FIG. The difference between the access point 1 shown in FIG. 3 and the access point 1 shown in FIG. 2 is that the interference monitoring module 20 is not provided. The access point 1 shown in FIG. 3 implements the function of the interference monitoring module 20 through the communication wireless module 19. Below, based on the structure shown in FIG. 2, the function operation | movement of the access point 1 is demonstrated.

(1-3) Mode Control Operation FIG. 4 shows an example of mode control of the access point 1.
First, when a battery (power source) (not shown) is connected to the constant power line of the access point 1 or when an external trigger signal indicating power-on is input to the processor 11, the mode control unit 17 operates in the interference monitoring mode. Enter C1. However, the external trigger signal here is a signal for operating only a part of functions other than the communication function (data transmission / reception function) of the access point 1. Therefore, in the configuration of FIG. 2, the transmission / reception processing unit 12, the communication control unit 13, and the communication wireless module 19 remain in a stopped state. In the configuration of FIG. 3, the transmission / reception processing unit 12, the communication control unit 13 remains stopped. Therefore, the external trigger signal here is close to a signal notifying connection of the battery to the access point 1. As the external trigger signal, the power itself supplied by the battery connection or the detection signal thereof can be used as the external trigger signal.

  In the interference monitoring mode C1, power is normally supplied only to functional parts necessary for interference monitoring (that is, only a part of the processing unit constituting the processor 11 and the interference monitoring module 20), and wasteful power consumption is consumed. It can be suppressed. In the case of the present embodiment, power is supplied to the time measuring unit 14, the interference recording unit 15, the interference monitoring unit 16, and the interference monitoring control unit 18 among the processing units constituting the processor 11. Therefore, in the interference monitoring mode C1, no power is supplied to the communication wireless module 19 (in the case of the configuration shown in FIG. 2), and the transmission / reception processing unit 12 and the communication control unit 13 involved in communication remain in a stopped state.

  In the interference monitoring mode C1, when an external trigger signal indicating communication on is input, the mode control unit 17 transitions to the communication mode C2. When transitioning to the communication mode C2, all the elements and functional units constituting the access point 1 are in an operating state. That is, power is supplied to the communication wireless module 19, and the transmission / reception processing unit 12 and the communication control unit 13 involved in communication are also effective. In the communication mode C2, when an external trigger signal indicating communication off is input, the mode control unit 17 transitions to the interference monitoring mode C1 again.

(1-4) Operation in Interference Monitoring Mode FIG. 5 shows the operation of the access point 1 in the interference monitoring mode C1. As described above, after the connection of the battery (power supply) or the input of an external trigger signal indicating power-on, the mode control unit 17 transitions to the interference monitoring mode C1. At this time, the interference monitoring unit 16 monitors the interference signal using the interference monitoring module 20 (S1). At the same time, the time measuring unit 14 measures the monitoring time for the frequency channel that is actually performing interference monitoring. In the radio communication system assumed in the present embodiment, the interference signal is present on the order of 60 seconds to several hours or more for one frequency channel. The interference recording unit 15 records information (channel information) and channel monitoring time of the frequency channel that is actually performing interference monitoring (S2). The recording here may always be executed only for the frequency channel that is actually being monitored for interference (that is, overwrite recording), or it may be an additional recording that leaves a history of all frequency channels that are monitored.

  Next, when interference is detected by the interference monitoring unit 16 (Yes in S3), the interference monitoring control unit 18 controls the interference monitoring unit 16 and the interference monitoring module 20 to monitor the interference signal. The channel is changed (S4). Thereafter, the interference monitoring unit 16 returns to S1 and continues the interference monitoring for the new frequency channel. On the other hand, when no interference is detected by the interference monitoring unit 16 (No in S3), the interference monitoring unit 16 continues to monitor the interference signal for the same frequency channel.

  FIG. 6 shows the operation of the access point 1 when an external trigger signal indicating communication ON is input during the interference monitoring mode C1. In this case, the mode control unit 17 executes a processing operation for changing the operation mode from the interference monitoring mode C1 to the communication mode C2. First, the mode control unit 17 controls to turn on the power of function units (generically referred to as “communication module”) necessary for wireless communication including the communication wireless module 19 (S11). Next, the mode control unit 17 refers to the information recorded in the interference recording unit 15 (S12), and determines whether or not there is a frequency channel having no interference signal for a predetermined time or longer (for example, 60 seconds or longer). (S13). When there is no frequency channel with no interference signal for a certain time or more (in the case of No), the mode control unit 17 continues to refer to the information in the interference recording unit 15. This is because even during this determination, the time measuring unit 14 continues to measure the monitoring time, and the recorded information by the interference recording unit 15 is also continuously updated. When there is a frequency channel without an interference signal for a certain time or more (in the case of Yes), the mode control unit 17 sets the detected frequency channel as a frequency channel used for communication by the communication wireless module 19 (S14). Then, the communication mode is changed (S15). As described above, since the mechanism can be switched to the communication mode only in the case of Yes in S13, it is possible to avoid in advance the possibility of interference with other systems after the start of communication.

(1-5) Operation in Communication Mode The communication mode is a mode in which data communication is possible at all times. However, depending on the system, authentication and / or association may be required prior to the start of data communication. A procedure for performing authentication or association with the access point 1 from the client 2 side will be described with reference to FIG. The client 2 also controls to turn on the power after inputting some external trigger signal (S21), and searches for a beacon signal transmitted from the access point 1 (S22). As will be described later, the access point 1 that has transitioned to the communication mode C2 transmits a beacon signal.

  When the beacon signal is detected, the client 2 transmits a request to the access point 1 that is the transmission source of the detected beacon signal, and performs authentication and / or association (S23). After this, data communication is possible anytime (S24). By the way, it may take time to execute authentication and / or association. In order to perform authentication and / or association, the client 2 needs to receive a beacon signal transmitted from the access point 1. Therefore, it is necessary to scan available frequency channels, which may take time. In addition, since beacon signals are normally transmitted at regular intervals, at least a certain amount of time is required to confirm one channel.

  Therefore, in this embodiment, in order to speed up the detection process of the beacon signal, the transmission timing of the beacon signal by the access point 1 is controlled as shown in FIG. Specifically, the beacon signal immediately after the transition to the communication mode C2 is transmitted at intervals, so that the client 2 can quickly find the beacon signal. For example, a beacon signal is transmitted at intervals of 20 ms (milliseconds). On the other hand, after the association with the client 2 ends, the beacon signal is transmitted at a longer interval (for example, at an interval of 100 ms (milliseconds)). ) Or stop transmission itself. As a result, high-speed association by the client 2 becomes possible.

(1-6) Relationship between External Trigger Signal Type and Mode Transition FIGS. 9 and 10 show the relationship between the external trigger signal type and the corresponding mode transition. FIG. 9 shows an example of three types of external trigger signals, and FIG. 10 shows an example of four types of external trigger signals. 9 and 10, the operation executed immediately after the first external trigger signal is input (preferably immediately after the battery is connected) is the same. That is, the access point 1 transits to the interference monitoring mode C1, but the client 2 remains powered off. Since operations after the input of the second external trigger signal are different, each figure will be described below.

  In the case of FIG. 9, after inputting the second external trigger signal, the access point 1 sets a frequency channel in which no interference signal exists as a communication channel, and then starts a communication mode C2. Here, the access point 1 starts transmission of a beacon signal according to the protocol shown in FIG. 8 and performs authentication and / or association according to a request from the client 2. Further, the access point 1 starts communication with the client 2 that has been authenticated and / or associated. On the other hand, the client 2 transitions to a power-on state in response to the input of the second external trigger signal, and performs authentication and / or association with the access point 1. After the authentication or association is completed, data communication is started between the access point 1 and the client 2. Thereafter, when the third external trigger signal is input, the access point 1 again transitions to the interference monitoring mode C1, and the client 2 returns to the power-off state.

  On the other hand, in the case of FIG. 10, after inputting the second external trigger signal, the access point 1 sets a frequency channel in which no interference signal exists as a communication channel, and then starts a communication mode C2. Further, the access point 1 starts transmission of a beacon signal according to the protocol shown in FIG. 8 and performs authentication and / or association in response to a request from the client 2. One client 2 transitions to a power-on state in response to the input of the second external trigger signal, and performs authentication and / or association with the access point 1. The difference from FIG. 9 is that actual data communication is not automatically started even after execution of authentication and / or association.

  In the case of FIG. 10, the communication between the access point 1 and the client 2 is started after the input of the fourth external trigger signal. As described above, since the processing necessary for communication is performed before the input of the fourth external trigger signal instructing the start of communication in the method of FIG. 10, the actual communication is started from the input of the fourth external trigger signal. 9 can be shortened compared to the method of FIG. Also in the case of FIG. 10, when the third external trigger signal is input after the start of communication, the access point 1 again transitions to the interference monitoring mode C1, and the client 2 returns to the power-off state.

(1-7) Frequency Channel Change at the Time of Interference Detection FIG. 11 shows how the frequency channel is changed when an interference signal is detected in the interference monitoring mode C1. This process corresponds to the processing operation shown in S4 of FIG. When interference is detected in the frequency channel currently being monitored, there is a possibility that an interference signal exists in the next frequency channel. In that case, it becomes necessary to change the frequency channel again (see FIG. 5), and it takes time until an available frequency channel is detected. Therefore, the interference monitoring control unit 18 sets a frequency channel at a position away from the assumed bandwidth of the interference signal as the next frequency channel to be monitored for interference with respect to the frequency channel currently being monitored. In FIG. 11, a state in which frequency channels that are not separated by the assumed bandwidth are excluded (skipped) from the interference monitoring target is indicated by a broken line. Thereby, it is possible to eliminate the possibility that an interference signal arriving from at least the same interference signal source is detected for the changed frequency channel. The interference monitoring control unit 18 selects the changed frequency channel based on the recording information of the interference recording unit 15 or information set in advance.

(1-8) Parallel and simultaneous monitoring of a plurality of frequency channels Next, functions suitable for the access point 1 to execute in the interference monitoring mode C1 will be described. In the above description, the access point 1 monitors the interference signal only for one frequency channel at a time in the interference monitoring mode C1. Here, as shown in FIG. 12, an example in which a plurality of frequency channels are monitored in a time division manner at a time will be described. The operation is realized by the interference monitoring control unit 18 controlling the interference monitoring module 20. In the case of the method shown in FIG. 12, even when an interference signal is detected for one frequency channel, communication can be started immediately using the frequency channel if no interference signal is detected for another frequency channel.

(1-9) Summary of Embodiment 1 By mounting the functional configuration described in this embodiment on the access point 1, even in a wireless communication system that requires frequency channel interference monitoring before the start of wireless communication, it is possible to Since a frequency channel in which no interference signal exists is detected, wireless communication can be started immediately after requesting wireless communication. Moreover, in the case of this embodiment, the frequency channel detection operation in which no interference signal exists is only the function monitoring unit 20 of the processor 11 related to interference monitoring and the interference monitoring module 20 that exclusively receives the signal of the monitoring target channel. Therefore, power consumption can be suppressed as compared with the case where all functions of the access point 1 are maintained in the on state. As a result, the access point 1 according to the present embodiment can extend the battery life as compared with the conventional method.

(2) Example 2
Below, the case where the radio | wireless communications system demonstrated in the example 1 of a form is applied to a vehicle-mounted system is demonstrated.

(2-1) System Configuration FIG. 13 shows a configuration example of a wireless communication system according to this embodiment. In FIG. 13, the same reference numerals are given to the portions corresponding to FIG. In the case of this embodiment, it is assumed that a display device 32 as a rear view monitor or an in-vehicle monitor is connected to the access point 1 and a camera 33 as a rear view camera is mounted on the client 2. That is, a system will be described in which a video signal behind the vehicle captured by the rear view camera is wirelessly transmitted in real time and displayed on the in-vehicle monitor at the same time when the shift enters the back gear. However, the use in the in-vehicle system is not limited to the rear view camera, and can be applied to, for example, wireless multimedia transmission (audio, video, TV signal).

  The access point 1 shown in FIG. 13 is different from the configuration of the access point of the first embodiment (FIG. 2) in that the video processing unit 31 is mounted on the processor 11 and the output of the video processing unit 31 is output to the display device 32. Connected to the processor 11 is a constant power line that is always supplied with electric power from the onboard battery, and connected to the processor 11 is an IG (ignition) power line that switches from low level to high level when the engine starts. It is different in point. The potential that always appears on the power supply line (becomes high level when the on-vehicle battery is connected) and the potential that appears on the IG power supply line (becomes high level when the engine is started) correspond to the external trigger signal described in the first embodiment.

  The client 2 shown in FIG. 13 is equipped with a camera 33 as compared with the client configuration of the first embodiment (FIG. 2), and the video signal captured by the camera 33 is an access point through the communication wireless module 21. The camera 33 is connected to a REV (back gear) power line that goes high when the shift enters the back gear, and the communication wireless module 21 has an IG power line. It is different in that it is connected. The potential appearing on the REV (back gear) power line (high level when the shift enters the back gear) and the potential appearing on the IG power line (high level when the engine starts) are the external trigger described in the first embodiment. Corresponds to the signal.

(2-2) Time Sequence FIG. 14 shows a time sequence executed by the access point 1 according to this embodiment. In the case of this embodiment, when the on-vehicle battery is connected to the constant power line or the access point 1 is connected to the constant power line, the high level external trigger signal is detected by the mode control unit 17. The mode control unit 17 transitions to the interference monitoring mode C1 by detecting the external trigger signal. This mode continues until the engine starts. When the engine starts, the IG power line goes high. By detecting the external trigger signal, the mode control unit 17 transitions to the communication mode C2 and executes authentication and / or association. Note that when the client 2 is a back view camera as in the present embodiment, even if the access point 1 transitions to the communication mode C2, data transmission is not started immediately (see FIG. 10).

  Thereafter, when the shift enters the back gear, the client 2 transmits the video signal captured by the camera 33 to the access point 1 in real time through a frequency channel in which no interference signal exists. The access point 1 displays the received video signal on the display device 32 after processing the received video signal by the video processing unit 31. When the shift is released from the back gear, the transmission of the video signal captured by the camera 33 ends. Note that the mode control unit 17 maintains the communication mode C2. Thereafter, when the engine is stopped, the potential of the IG power supply line changes to a low level. The mode control unit 17 that has detected this change as an external trigger signal enters the interference monitoring mode C1. This interference monitoring mode C1 continues until the battery is removed from the constant power line or until it is removed from the access point 1 from the constant power line.

(2-3) Summary of Embodiment 2 By mounting the functional configuration described in this embodiment on the access point 1 and the client 2, the image behind the vehicle immediately after the driver puts the shift into the back gear is displayed on the access point. 1 can be wirelessly transmitted and displayed on the display device 32 without waiting time. Further, as described in the first embodiment, in this embodiment, only the processing unit related to the interference monitoring functions at the access point 1 while the engine is off, and the consumption of the on-vehicle battery is minimized. It can be suppressed to the limit.

(3) Example 3
(3-1) System Configuration FIG. 15 shows a configuration example of a radio communication system according to this embodiment. In FIG. 15, the same reference numerals are given to the portions corresponding to FIG. In this embodiment as well, as in Embodiment 2, a system will be described in which a video signal behind the vehicle imaged by the rear view camera is wirelessly transmitted in real time and displayed on the in-vehicle monitor at the same time as the shift enters the back gear.

  The difference from Embodiment 2 described above is that the power line connected to the access point 1 is connected via the switch 42. The switch 42 is configured such that when an input signal from another system is detected, the potential of the output signal is switched to a high level. In the case of this embodiment, the other system is a keyless entry system 41. Here, the keyless entry system 41 is a system that detects whether or not a driver's key exists around the vehicle. The switch 42 is an external trigger supplied to the access point 1 when a signal indicating key detection is input from the keyless entry system 41 or when the power line is constantly at a high level due to key detection by the keyless entry system 41. It operates to switch the signal potential to high level. On the other hand, the switch 42 operates to switch the potential of the output signal to a low level when a signal indicating that a key is not detected is input from the keyless entry system 41 or when the power supply line is always at a low level.

(3-2) Time Sequence FIG. 16 shows a time sequence executed by the access point 1 according to this embodiment. In the case of this embodiment, when the keyless entry system 41 detects a key around the vehicle, or when the switch 42 detects that the power supply line is always at a high level by the detection, the mode control unit 17 Enter interference monitoring mode. This mode continues until the engine starts. When the engine starts, the IG power line goes high. By detecting the external trigger signal, the mode control unit 17 transitions to the communication mode C2 and executes authentication and / or association. Note that when the client 2 is a back view camera as in the present embodiment, even if the access point 2 transitions to the communication mode C2, data transmission is not started immediately (see FIG. 10).

  Thereafter, when the shift enters the back gear, the client 2 transmits the video signal captured by the camera 33 to the access point 1 in real time through a frequency channel in which no interference signal exists. The access point 1 displays the received video signal on the display device 32 after processing the received video signal by the video processing unit 31. When the shift is released from the back gear, the transmission of the video signal captured by the camera 33 ends. Note that the mode control unit 17 maintains the communication mode C2. Thereafter, when the engine is stopped, the potential of the IG power supply line changes to a low level. The mode control unit 17 that has detected this change as an external trigger signal enters the interference monitoring mode C1. The interference monitoring mode C1 is continued until the driver's key is no longer detected from around the vehicle by the keyless entry system 41. When the key is no longer detected, the mode control unit 17 ends the interference monitoring mode C1 and transitions to a power-off state (stopped state).

(3-3) Summary of Embodiment 3 Also in this embodiment, as in Embodiment 2, the video behind the vehicle can be wirelessly transmitted to the access point 2 immediately after the driver puts the shift into the back gear. It can be displayed on the display device 32 without time. Moreover, in the case of this embodiment, interference monitoring is executed only when the driver is present around the vehicle, and interference monitoring is not executed when the driver is not present around the vehicle. The battery consumption can be further suppressed.

(4) Other Embodiments The present invention is not limited to the configuration of the embodiment described above, and includes various modifications. For example, in order to explain the present invention in an easy-to-understand manner, some of the above-described embodiments are described in detail for some embodiments, and it is not necessary to include all the configurations described. Moreover, it is possible to replace a part of a certain form example with the structure of another form example, and it is also possible to add the structure of another form example to the structure of a certain form example. It is also possible to add other configurations to the configuration of each embodiment, replace some configurations of each embodiment with other configurations, or delete some configurations of each embodiment.

  Moreover, you may implement | achieve some or all of each structure, a function, a process part, a process means, etc. which were mentioned above as an integrated circuit or other hardware, for example. Each of the above-described configurations, functions, and the like may be realized by a processor interpreting and executing a program that realizes each function. That is, each configuration may be realized by software. In this case, information such as programs, tables, and files for realizing each function can be stored in a memory, a hard disk, a storage device such as an SSD (Solid State Drive), or a storage medium such as an IC card, an SD card, or a DVD. . Control lines and information lines indicate what is considered necessary for the description, and do not represent all control lines and information lines necessary for the product. In practice, it can be considered that almost all components are connected to each other.

  DESCRIPTION OF SYMBOLS 1 ... Access point, 2 ... Client, 11 ... Processor, 12 ... Transmission / reception processing part, 13 ... Communication control part, 14 ... Time measurement part, 15 ... Interference recording part, 16 ... Interference monitoring part, 17 ... Mode control part, 18 ... Interference monitoring control unit, 19 ... Communication wireless module, 20 ... Interference monitoring module, 21 ... Communication wireless module, 31 ... Video processing unit, 32 ... Display device, 33 ... Camera, 41 ... Keyless entry system, 42 ... switch.

Claims (15)

In a wireless communication system having one or a plurality of clients and an access point that operates by receiving power from a battery and needs to monitor the presence or absence of an interference signal prior to the start of use of a frequency channel,
The access point is
A wireless communication unit that wirelessly communicates with the client;
An interference monitoring unit that monitors the presence or absence of an interference signal for the set frequency channel;
After the input of the first trigger signal, the interference monitoring unit is switched from the stop mode to the interference monitoring mode to detect a frequency channel in which no interference signal exists, and the second trigger signal is input following the first trigger signal. Then, the interference monitoring unit is switched from the interference monitoring mode to the communication mode, and power is supplied to the wireless communication unit to start communication with the client, following the second trigger signal, A wireless communication system comprising: a mode control unit that switches the interference monitoring unit from the communication mode to the interference monitoring mode and stops supplying power to the wireless communication unit when a trigger signal is input. The wireless communication system according to claim 1, wherein
In the interference monitoring mode, when an interference signal is detected in the frequency channel being monitored, the mode control unit changes the monitoring target to another frequency channel and continues to monitor the interference signal, and the second trigger The wireless communication system is characterized by switching to the communication mode only when a frequency channel in which an interference signal does not exist for a predetermined time or more is detected when a signal is input. The wireless communication system according to claim 2,
When the interference signal is detected in the frequency channel being monitored, the mode control unit sets the frequency channel to be monitored next to the bandwidth of the expected interference signal with respect to the frequency channel being monitored. A wireless communication system, characterized in that it is set to a frequency channel having a frequency difference of. The wireless communication system according to claim 1, wherein
In the interference monitoring mode, the mode control unit supplies power only to a circuit part necessary for interference monitoring, and does not supply power to other circuit parts. The wireless communication system according to claim 1, wherein
The client requests authentication and / or association to the access point after inputting the second trigger signal, and starts communication with the access point after completion of the authentication and / or association. A wireless communication system characterized by the above. The wireless communication system according to claim 1, wherein
The mode control unit transmits a beacon signal at an interval of X seconds to a frequency channel in which an interference signal does not exist for a predetermined time or more after the transition to the communication mode, and performs authentication and / or association with the client that has received the beacon signal. A wireless communication system, comprising: transmitting a beacon signal at an interval of Y seconds (where X <Y) to a frequency channel in which the interference signal does not exist for a certain period of time after the end of the operation. The wireless communication system according to claim 1, wherein
The mode control unit monitors a plurality of frequency channels in a time division manner in the interference monitoring mode. It has one or a plurality of clients used in the vehicle and an access point that operates by receiving power from an in-vehicle battery, and it is necessary to monitor the presence or absence of an interference signal before starting to use the frequency channel. In an in-vehicle wireless communication system,
The access point is
A wireless communication unit that wirelessly communicates with the client;
An interference monitoring unit that monitors the presence or absence of an interference signal for the set frequency channel;
After the input of the first trigger signal, the interference monitoring unit is switched from the stop mode to the interference monitoring mode to detect a frequency channel in which no interference signal exists, and the second trigger signal is input following the first trigger signal. Then, the interference monitoring unit is switched from the interference monitoring mode to the communication mode, and power is supplied to the wireless communication unit to start communication with the client, following the second trigger signal, An in-vehicle wireless communication system comprising: a mode control unit that switches the interference monitoring unit from the communication mode to the interference monitoring mode and stops power supply to the wireless communication unit when a trigger signal is input . The in-vehicle wireless communication system according to claim 8,
In the interference monitoring mode, when an interference signal is detected in the frequency channel being monitored, the mode control unit changes the monitoring target to another frequency channel and continues to monitor the interference signal, and the second trigger The in-vehicle wireless communication system, which is switched to the communication mode only when a frequency channel in which an interference signal does not exist for a predetermined time or more is detected when a signal is input. The in-vehicle wireless communication system according to claim 8,
The in-vehicle wireless communication system, wherein the mode control unit supplies power only to a circuit part necessary for interference monitoring and does not supply power to other circuit parts in the interference monitoring mode. The in-vehicle wireless communication system according to claim 8,
The client requests authentication and / or association to the access point after inputting the second trigger signal, and starts communication with the access point after completion of the authentication and / or association. An in-vehicle wireless communication system characterized by the above. The in-vehicle wireless communication system according to claim 8,
The first trigger signal is a potential appearing on a constant power line directly connected to the in-vehicle battery or a detection signal thereof, and the second trigger signal appears on an IG (ignition) power line when the engine is started. An in-vehicle wireless communication system characterized by being an electric potential or a detection signal thereof. The in-vehicle wireless communication system according to claim 8,
The first trigger signal is a signal that is input when a keyless entry system detects a peripheral key, and the second trigger signal is a potential that appears on an IG (ignition) power line at the start of the engine or its An in-vehicle wireless communication system characterized by being a detection signal. The in-vehicle wireless communication system according to claim 8,
The in-vehicle wireless communication system, wherein communication with the client in the communication mode is executed after a potential that appears when a shift is changed to a back gear is detected. In an access point that operates by receiving power from a battery and needs to monitor the presence or absence of an interference signal before starting to use the frequency channel,
A wireless communication unit that wirelessly communicates with one or more clients;
An interference monitoring unit that monitors the presence or absence of an interference signal for the set frequency channel;
After the input of the first trigger signal, the interference monitoring unit is switched from the stop mode to the interference monitoring mode to detect a frequency channel in which no interference signal exists, and the second trigger signal is input following the first trigger signal. Then, the interference monitoring unit is switched from the interference monitoring mode to the communication mode, and power is supplied to the wireless communication unit to start communication with the client, following the second trigger signal, An access point comprising: a mode control unit that switches the interference monitoring unit from the communication mode to the interference monitoring mode and stops supplying power to the wireless communication unit when a trigger signal is input.

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