JP2011146964A - Radio communication system, terminal device, repeater, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further save electrical power to be consumed in radio communication system utilizing repeaters. <P>SOLUTION: An access point 2 prepared as a repeater in radio communication includes: a controller 20; a timer 21; an RF circuit 22; and a radio communication controller 23. In the power saving mode, the radio communication controller 23 controls the RF circuit 22 to the ON state in each predetermined period responding to the signal from the timer 21 and meanwhile, suppresses power consumption in the RF circuit 22 by switching the RF circuit 22 to the OFF state from the ON state when the predetermined period has passed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for suppressing power consumed in wireless communication. More specifically, the present invention relates to a technique for suppressing power consumption of a relay device in wireless communication between the relay device and a terminal device.

  2. Description of the Related Art Conventionally, a wireless communication system in which a plurality of terminal devices perform information communication by wireless communication such as a wireless LAN via a relay device is known. On the other hand, various technologies have been proposed for power saving in a wireless communication system. For example, in Patent Document 1, in synchronization with a beacon signal from an access point, the wireless LAN device built in the host is turned on, and whether or not there is an incoming call for itself is checked. A technique is described in which the host power is turned on only when there is a problem. According to such a technique, the power supply of the host is always in the OFF state while there is no incoming call for itself, so that power consumption in the host can be suppressed.

JP 2004-180115 A

  However, the above-described conventional technique is a technique for suppressing power consumption in the host (terminal device), and there is a problem that consideration is not given to suppressing power consumption in the access point (relay device).

  The present invention has been made in view of the above problems, and an object of the present invention is to further reduce the power consumed in wireless communication using a relay.

  In order to solve the above-mentioned problem, the invention of claim 1 is a wireless communication system that performs wireless communication between a terminal device and a repeater, wherein the terminal device communicates with the repeater, and A first communication unit that performs wireless communication and transmits a request to start wireless communication; and the relay device includes second communication unit that performs wireless communication with the terminal device; A switching means for switching an operation mode of the relay between a normal mode and a power saving mode in which the power consumption of the relay is suppressed at least more than the power consumption in the normal mode; Are wirelessly connected to the first mode in which the second communication means can receive at least the start request transmitted from the terminal device and the second communication means in the power saving mode. And switches the second mode for prohibiting communication.

  A second aspect of the present invention is the wireless communication system according to the first aspect of the present invention, wherein the terminal device controls the first communication means to transmit the wireless communication start request a plurality of times. The control unit further includes a control unit, wherein the first control unit is configured to transmit a subsequent start request from two or more consecutive start requests until a later start request is transmitted. The first communication means is controlled so that the waiting time is shorter than the response time from the repeater to the previous start request.

  The invention of claim 3 is the radio communication system according to the invention of claim 1 or 2, wherein the switching means sends a start request transmitted from the terminal device to the second communication in the first mode. After the means receives, the power saving mode is switched to the normal mode.

  The invention of claim 4 is the radio communication system according to any one of claims 1 to 3, wherein, in the second mode, the second communication means transmits information transmitted from the terminal device. It is characterized in that monitoring about whether or not it has been received is stopped.

  The invention according to claim 5 is the wireless communication system according to any one of claims 1 to 4, wherein, in the second mode, the second communication means stops transmitting the beacon signal. Features.

  A sixth aspect of the present invention is the wireless communication system according to any one of the first to fifth aspects of the present invention, wherein the repeater switches the switching timing between the first mode and the second mode by the switching means. It further has the 2nd control means which controls.

  The invention according to claim 7 is the wireless communication system according to the invention of claim 6, wherein the second control means switches the switching so that the first mode and the second mode are periodically switched. It is characterized by controlling the timing.

  The invention according to claim 8 is a terminal device that performs wireless communication with a repeater, performs the wireless communication with the repeater, and requests to start the wireless communication. Communication means for transmitting, and control means for controlling the communication means so as to transmit the wireless communication start request a plurality of times, wherein the control means includes two consecutive start requests transmitted the plurality of times. For one start request, the waiting time from when the previous start request is transmitted until the subsequent start request is transmitted is shorter than the response time from the repeater to the previous start request. The first communication means is controlled.

  The invention according to claim 9 is a relay device that performs wireless communication with a terminal device, the communication unit that performs wireless communication with the terminal device, and an operation mode of the relay device. Switching means for switching between the normal mode and the power saving mode in which the power consumption of the repeater is suppressed at least than the power consumption in the normal mode, the switching means includes the power saving In the mode, switching between a first mode in which the communication unit can receive at least a start request transmitted from the terminal device and a second mode for prohibiting wireless communication with the communication unit, To do.

  The invention of claim 10 is a wireless communication method for realizing wireless communication between a terminal device and a repeater, wherein (a) the operation mode of the repeater is changed from a normal mode to at least the normal mode. A step of switching to a power saving mode in which the power consumption of the repeater is suppressed more than the power consumption in (b), the operation of the repeater when the operation mode of the repeater is the power saving mode A first mode in which the repeater can receive at least the wireless communication start request transmitted from the terminal device; and a second mode for prohibiting the repeater from performing the wireless communication And (c) a subsequent start request after the previous start request is transmitted for two consecutive start requests among the wireless communication start requests transmitted a plurality of times. And a step of transmitting the wireless communication start request a plurality of times so that a waiting time until the transmission is shorter than a response time from the repeater with respect to the previous start request. And

  According to the first to seventh aspects of the present invention, the repeater operates between the normal mode and the power saving mode in which the power consumption of the repeater is suppressed more than the power consumption in at least the normal mode. In the power saving mode, by switching between the first mode in which at least a start request transmitted from the terminal device can be received and the second mode in which wireless communication is prohibited, the first mode of the power saving mode is switched. In the 2 mode, since wireless communication is prohibited, the power consumption during that time is suppressed compared to the normal mode. Therefore, the power consumption of the repeater can be suppressed.

  According to a fourth aspect of the present invention, in the second mode, the second communication means confirms the presence or absence of received information by stopping monitoring whether or not the information transmitted from the terminal device has been received. Necessary power can be suppressed.

  According to the fifth aspect of the present invention, in the second mode, the second communication means can suppress the power required for transmitting the beacon signal by stopping the transmission of the beacon signal.

  According to the sixth aspect of the present invention, it is possible to perform flexible and efficient switching by further including second control means for controlling switching timing between the first mode and the second mode by the switching means.

  According to the seventh aspect of the present invention, the switching timing can be easily controlled by controlling the switching timing so that the first mode and the second mode are periodically switched.

  In the invention according to claim 8, for two continuous start requests among the start requests transmitted a plurality of times, the waiting time from when the previous start request is transmitted to when the subsequent start request is transmitted is: By setting the time shorter than the response time from the repeater to the previous start request, the power consumption of the repeater serving as the communication partner can be suppressed.

  According to the ninth aspect of the present invention, the communication means for performing wireless communication with the terminal device, the operation mode of the repeater, the normal mode, and at least the power consumption of the repeater than the power consumption in the normal mode Switching means for switching between the power saving modes in which the power is suppressed, and the switching means is in a state in which the communication means can receive at least a start request transmitted from the terminal device in the power saving mode. By switching between the mode and the second mode for prohibiting wireless communication with the communication means, wireless communication by the communication means is prohibited in the second mode of the power saving mode. Power is suppressed compared to the normal mode. Therefore, the power consumption of the repeater can be suppressed.

  According to a tenth aspect of the present invention, there is provided a step of switching the operation mode of the repeater from the normal mode to the power saving mode in which the power consumption of the repeater is suppressed at least more than the power consumption in the normal mode; When the operation mode is the power saving mode, the repeater operation mode is set to the first mode in which the repeater can receive at least a wireless communication start request transmitted from the terminal device, and the repeater Switching between the second mode for prohibiting wireless communication and two consecutive start requests among the wireless communication start requests transmitted a plurality of times, after the previous start request is transmitted, The wireless communication start request is duplicated so that the waiting time until the request is transmitted is shorter than the response time from the repeater to the previous start request. By a step of sending times, in the second mode of the power saving mode, since the communication by the wireless by the relay apparatus is prohibited, the power consumption in between the repeater can be suppressed as compared to the normal mode. Therefore, the power consumption of the repeater can be suppressed.

It is a figure which shows the radio | wireless communications system which concerns on this invention. It is a block diagram of the access point comprised as a relay machine based on this invention. It is a block diagram of the terminal device concerning the present invention. It is a flowchart which shows operation | movement of the terminal device in the radio | wireless communication method which concerns on this invention. 5 is a flowchart showing an operation of an access point in the wireless communication method according to the present invention. It is a flowchart which shows the radio | wireless communication process in a power saving mode. It is a figure which shows the communication sequence when the access point in power saving mode transfers to normal mode.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

<1. Embodiment>
FIG. 1 is a diagram showing a wireless communication system 1 according to the present invention. The wireless communication system 1 according to the present embodiment includes an access point 2 and a terminal device 3, and is configured as a system that performs wireless communication (for example, a wireless LAN) between the access point 2 and the terminal device 3. In the present embodiment, an example of adopting a WiFi (Wireless Fidelity) standard as wireless communication between the access point 2 and the terminal device 3 will be described. Of course, the wireless method is not limited to this. Absent.

  As shown in FIG. 1, a communication cable 9 is connected to the access point 2 and is connected in a state where wired communication is possible with an external device or a network (not shown). However, the wireless communication system 1 does not necessarily need to be connected to the communication cable 9 and may be configured as a system that realizes wireless communication between at least the access point 2 and the terminal device 3. That is, the access point 2 does not necessarily have to be a device that relays communication between the terminal device 3 and another device, and the access point 2 has a configuration and a function as a final communication partner of the terminal device 3. May be.

  FIG. 2 is a block diagram of the access point 2 configured as a repeater according to the present invention. The access point 2 in the present embodiment includes a control unit 20, a timer 21, an RF circuit 22, a wireless communication control unit 23, and an interface 24.

  The access point 2 provides various types of information to the operation unit (keys, buttons, and the like) that allows various information to be input to the access point 2 when operated by the operator. An output unit (LED, lamp, liquid crystal panel, speaker, or the like) may be provided.

  As will be described in detail later, the operation mode of the access point 2 is defined as a normal mode and a power saving mode in which the power consumption of the access point 2 is suppressed at least more than the power consumption in the normal mode. .

  Although not shown in FIG. 2, the control unit 20 is mainly composed of an arithmetic device and a storage device. Note that the arithmetic device provided in the control unit 20 is not limited to one device, and a plurality of devices may operate in cooperation in parallel. The storage device is configured from various storage media such as a ROM, a RAM, a hard disk, and a buffer as necessary, and a program, data, etc. (for example, BIOS, OS, etc.) necessary for realizing the function of the access point 2 Application program, setting data, etc.).

  Thereby, the control part 20 has a function which controls each structure with which the access point 2 is provided, when an arithmetic unit operate | moves according to the program stored in the memory | storage device. That is, the control unit 20 has a configuration and a function as a general computer. The operation of the control unit 20 will be described later sequentially.

  The timer 21 includes an oscillation circuit (not shown) and the like, measures the time indicated by the timer value based on the timer value set by the control signal from the control unit 20, and sends a signal to the wireless communication control unit 23. introduce. The signal output from the timer 21 is mainly used to notify the wireless communication control unit 23 of the timing for switching the operation mode of the access point 2, and details will be described later.

  Although not shown in detail, the RF circuit 22 is an antenna that converts a signal into a radio wave and converts a received radio wave into a signal, a detection circuit that detects a radio wave received by the antenna, a circuit that converts a radio signal into information, A circuit for amplifying the signal is provided, and a function of performing wireless communication with the terminal device 3 is provided.

  Specifically, the RF circuit 22 transmits the information to the terminal device 3 by emitting radio waves from the antenna described above in accordance with the information transmitted from the wireless communication control unit 23. Further, the radio wave emitted from the terminal device 3 is received by the above-described antenna, and the received radio wave signal is appropriately converted into information and transmitted to the wireless communication control unit 23.

  The RF circuit 22 is turned on / off in response to a signal from the wireless communication control unit 23. Hereinafter, in order to turn on / off the RF circuit 22, signals transmitted from the wireless communication control unit 23 are collectively referred to as “ON / OFF signal”. Further, an ON / OFF signal for switching the RF circuit 22 to the ON state (starting state) is simply referred to as an “ON signal”, and an ON / OFF signal for switching the RF circuit 22 to the OFF state (stopping state) is simply “ This is referred to as an “OFF signal”.

  When the RF circuit 22 is in the ON state (activated state), the access point 2 is in a state where at least information can be received wirelessly. On the other hand, when the RF circuit 22 is in the OFF state, the RF circuit 22 is in a state in which wireless communication is impossible, and not only can wirelessly transmit but also cannot receive information.

  In other words, when the RF circuit 22 is turned off, the RF circuit 22 stops monitoring whether or not any information is received from the terminal device 3. Therefore, for example, the detection circuit for detecting the radio wave transmitted by the terminal device 3 is stopped. Thereby, it is possible to suppress the power (power consumption of the detection circuit) necessary for confirming the presence or absence of reception information.

  In addition, when the RF circuit 22 is in the OFF state, the RF circuit 22 stops transmitting information (for example, a beacon signal transmitted periodically). Thereby, the power required for transmitting information (for example, power consumed to transmit radio waves) can be suppressed. Therefore, when the RF circuit 22 is in the OFF state, the power consumption at the access point 2 is suppressed compared to at least when the RF circuit 22 is in the ON state.

  In the access point 2 according to the present embodiment, the RF circuit 22 is not turned off in the normal operation mode of the operating mode, and the RF circuit 22 is turned off only in the power saving mode. Therefore, in the power saving mode, power consumption is suppressed compared to when the RF circuit 22 is in the ON state at least during the period in which the RF circuit 22 is in the OFF state. Electric power is suppressed.

  In other words, in the present invention, there may be no difference in power consumption between the normal mode and the power saving mode at a certain moment (for example, when the RF circuit 22 is in the ON state in the power saving mode). Therefore, in the power saving mode, “at least the power consumption of the access point 2 is suppressed compared to the power consumption in the normal mode” means that the power consumption in all states in the normal mode for all periods in the power saving mode. It is not meant to limit to “becomes a state where power consumption is suppressed”. For example, the average power consumption per unit time includes the case where the power saving mode is “suppressed” than the normal mode.

  The wireless communication control unit 23 has a function of switching the operation mode of the access point 2 and controlling the RF circuit 22 according to information (signals) transmitted from the control unit 20, the timer 21, and the RF circuit 22. Yes. In addition, when information to be transmitted from the control unit 20 to the terminal device 3 is acquired, the RF circuit 22 transmits the information, but also has a function of transmitting information received by the RF circuit 22 to the control unit 20. is doing.

  In the access point 2 in the present embodiment, the RF circuit 22 and the wireless communication control unit 23 constitute a so-called communication module (WiFi module).

  The interface 24 is a connector or a terminal for connecting the communication cable 9 to the access point 2. As a result, the access point 2 can perform wired communication and has a function of relaying communication between the external device connected to the communication cable 9 and the terminal device 3.

  FIG. 3 is a block diagram of the terminal device 3 according to the present invention. As illustrated in FIG. 3, the terminal device 3 includes a control unit 30, a timer 31, an RF circuit 32, a wireless communication control unit 33, an operation unit 34, and a display unit 35. Although details will be described below, the terminal device 3 is configured as a computer capable of wireless communication with the access point 2.

  Although not shown in detail, the control unit 30 is mainly composed of an arithmetic device and a storage device. Note that the arithmetic device provided in the control unit 30 is not limited to one device, and a plurality of devices may operate in cooperation in parallel. The storage device is configured from various storage media such as a ROM, a RAM, a hard disk, and a buffer as required, and programs and data necessary for realizing the functions of the terminal device 3 (for example, BIOS, OS, Application programs, setting data, etc.) are stored.

  The control unit 30 has a function of controlling each component included in the terminal device 3 when the arithmetic device operates according to a program stored in the storage device. The operation of the control unit 30 will be described later sequentially.

  The timer 31 includes an oscillation circuit (not shown) and the like, is activated according to a control signal from the wireless communication control unit 33, measures a necessary time, and transmits a signal to the wireless communication control unit 33. The wireless communication control unit 33 according to the present embodiment sets the timer value t1 and the timer value t2 to time when the timer 31 is started.

  The timer value t1 is a parameter indicating a time interval at which the activated timer 31 sends a request transmission signal to the wireless communication control unit 33. As will be described in detail later, a signal transmitted from the timer 31 to the wireless communication control unit 33 for each timer value t1 is transmitted from the RF circuit 32 to the access point 2 as a wireless communication start request (hereinafter referred to as “probe request”). Is used to determine the timing of transmission. In the following description, a signal transmitted from the timer 31 to the wireless communication control unit 33 every time the timer value t1 elapses in order to determine the timing for transmitting the probe request is referred to as a “request transmission signal”.

  The timer value t2 is a parameter indicating the maximum time that the timer 31 is continuously activated. Although details will be described later, a signal transmitted from the timer 31 to the wireless communication control unit 33 for each timer value t2 is used to determine the timing to stop monitoring for one communication channel. In the following description, in order to determine the timing to stop monitoring for one communication channel, a signal transmitted from the timer 31 to the wireless communication control unit 33 when the timer value t2 has elapsed is referred to as a “monitoring stop signal”. Called.

  As a result, when the wireless communication control unit 33 activates the timer 31, the activated timer 31 has the timer value t1 until the elapsed time from the activation reaches the timer value t2, unless stopped. Each time it passes (that is, at period t1), a request transmission signal is output. Then, when the elapsed time after activation reaches the timer value t2, the timer 31 outputs a monitoring stop signal to the wireless communication control unit 33 to stop activation. The timer value t1 and the timer value t2 can be stored in advance in the storage device as setting data.

  The RF circuit 32 has a configuration equivalent to that of the RF circuit 32 of the access point 2, and has a function of performing wireless communication with the access point 2. Specifically, the RF circuit 32 transmits the information toward the access point 2 by emitting a radio wave from an antenna (not shown) according to the information transmitted from the wireless communication control unit 33. Further, the radio wave emitted from the access point 2 is received by the above-described antenna, and the received radio wave signal is converted into information and transmitted to the wireless communication control unit 33.

  The wireless communication control unit 33 has a function of controlling the RF circuit 32 in accordance with information (signal) transmitted from the control unit 30 and the timer 31. In addition, when information to be transmitted from the control unit 30 toward the access point 2 is acquired, the RF circuit 32 transmits the information, and at the same time, the information received by the RF circuit 32 is transmitted to the control unit 30. is doing.

  In particular, the wireless communication control unit 33 in the present embodiment causes the RF circuit 32 to transmit a probe request to the access point 2 every time a request transmission signal is input from the timer 31.

  The operation unit 34 corresponds to, for example, various buttons, a keyboard, a mouse, a controller, a joystick, and the like, and is used when an operator inputs some information to the terminal device 3. The operation unit 34 is not limited to these. For example, when information is input by an image, an imaging camera, a scanner, or the like also functions as the operation unit 34.

  The display unit 35 corresponds to, for example, a liquid crystal panel, a liquid crystal display, a CRT, an LED, a lamp, and the like, and has a function of providing various information to the operator.

  The above is description of the structure and function of the radio | wireless communications system 1 in this Embodiment. Next, a wireless communication method performed between the access point 2 and the terminal device 3 of the wireless communication system 1 will be described.

  FIG. 4 is a flowchart showing the operation of the terminal device 3 in the wireless communication method according to the present invention. In FIG. 4, only the operation in which the terminal device 3 transmits information to the access point 2 is illustrated, and the operation in which the terminal device 3 receives information and the operation to execute other applications are omitted. In the present embodiment, after the transmission of specific information is completed by the RF circuit 32 of the terminal device 3, a response to the specific information transmitted by the access point 2 that has received the specific information is a terminal device. 3 is referred to as a “response time T”.

  First, when the control unit 30 of the terminal device 3 needs to transmit information (transmission information) toward the access point 2 during operation (Yes in step S1), the control unit 30 transmits the transmission information to the wireless communication control unit 33. To communicate.

  At this time, when a link is established with the access point 2 (negotiation regarding WiFi communication is established) (Yes in step S2), the wireless communication control unit 33 is transmitted from the control unit 30. Transmission information is transmitted to the RF circuit 32. Thereby, the RF circuit 32 transmits the transmission information toward the access point 2 (step S3).

  When step S2 is executed, if the link between the terminal device 3 and the access point 2 is disconnected (No in step S2), the wireless communication control unit 33 starts the timer 31 and sets the timer value t1, t2 is set (step S4). In parallel with this, the wireless communication control unit 33 causes the RF circuit 32 to transmit an initial probe request (step S5).

  When step S5 is executed, the wireless communication control unit 33 monitors the response from the access point 2 (step S9) while monitoring the monitoring stop signal and the request transmission signal from the timer 31 (steps S6 and S7). More specifically, the state waits for an interrupt signal from the timer 31 (a signal notifying that timer values t1 and t2 have elapsed) and a reception interrupt signal from the RF circuit 32.

  A request transmission signal (that is, a signal for notifying that the timer value t1 has elapsed) is input from the timer 31 until a monitoring stop signal (a signal for informing that the timer value t2 has elapsed) is input. Then, the wireless communication control unit 33 determines Yes in step S7. Then, the radio communication control unit 33 controls the RF circuit 32 so as to transmit a probe request toward the access point 2 in accordance with the timing when the request transmission signal is input. Thereby, the RF circuit 32 transmits the probe request toward the access point 2 (step S8).

  As described above, in the terminal device 3 in the present embodiment, the request transmission signal is input to the wireless communication control 33 for each timer value t1 while the timer 31 is activated. Therefore, as long as the timer 31 is activated, a probe request is transmitted from the terminal device 3 at the cycle t1.

  In such a configuration, the terminal device 3 must complete the transmission of the previous probe request before transmitting a new probe request. Therefore, it is necessary to determine the cycle t1 so that the cycle t1 is longer than the time required to complete transmission of one probe request (hereinafter referred to as “sending time st”).

  That is, the timer value t1 is determined in advance according to the information amount of the probe request, the communication speed, and the like so that “st <t1”. In the following description, the time from the completion of transmission of a probe request to the start of transmission of the next probe request is referred to as “transmission waiting time wt”. That is, in the present embodiment, the relationship t1 = st + wt is established, and it is preferable that wt ≠ 0 in order to reliably complete the transmission of the probe request during the period t1.

  When a reception interrupt signal (that is, a signal for notifying that a response from the access point 2 has been received) is input from the RF circuit 32 before the monitoring stop signal is input, the wireless communication control unit 33 It determines with Yes in step S9. Then, the wireless communication control unit 33 notifies the control unit 30 that there has been a response from the access point 2, and the control unit 30 stops starting the timer 31 (step S10). That is, when step S10 is executed, the timer 31 is stopped from being started before the timer value t2 elapses after being started by executing step S4.

  In parallel with the process of step S10, the wireless communication control unit 33 performs communication negotiation with the access point 2 according to a normal procedure of WiFi communication (step S13), and establishes a link with the access point 2. Thereby, when the link between the terminal device 3 and the access point 2 is established, the above-described step S3 is executed. That is, transmission information is transmitted from the wireless communication control unit 33 to the RF circuit 32, and the transmission information is transmitted toward the access point 2.

  On the other hand, when a monitoring stop signal is input from the timer 31, the wireless communication control unit 33 determines Yes in step S6. At this time, the timer 31 stops starting when the timer value t2 has elapsed (step S11).

  Next, the wireless communication control unit 33 determines whether or not there is a response from the access point 2 to the probe request (step S12).

  And if it determines with Yes in step S10, the radio | wireless communication control part 33 will open the link between the access points 2 by performing above-mentioned step S13. Thereby, when the link between the terminal device 3 and the access point 2 is established, the above-described step S3 is executed. That is, transmission information is transmitted from the wireless communication control unit 33 to the RF circuit 32, and the transmission information is transmitted toward the access point 2.

  When step S12 is executed and there is no response from the access point 2 (No in step S12), the wireless communication control unit 33 determines that the communication channel that has not received a response from the access point 2 (the probe request so far) Is switched to another communication channel (step S14). And the radio | wireless communication control part 33 returns to step S4, and repeats a process. That is, the timer 31 is started again (step S4), and a probe request is transmitted using a new communication channel (step S5).

  Although not shown in FIG. 4, the wireless communication control unit 33 determines that the elapsed time after completing the transmission of the last probe request in step S12 is a sufficient time with respect to the response time T. Until it becomes, it is determined No after waiting for a response from the access point 2. Hereinafter, the time during which the wireless communication control unit 33 waits for a response in step S12 is referred to as “response waiting time WT”.

  Thus, in a situation where a link with the access point 2 is not secured, the wireless communication control unit 33 causes the RF circuit 32 to transmit a plurality of probe requests by executing steps S6 to S9. And transmission of such a probe request is continued for the timer value t2, and when there is no response to this, the wireless communication control unit 33 sequentially scans while switching communication channels.

  The above is mainly the operation of the terminal device 3 in the wireless communication method. Next, the operation of the access point 2 in the wireless communication method will be described.

  FIG. 5 is a flowchart showing the operation of the access point 2 in the wireless communication method according to the present invention. In FIG. 5, the operation for requesting access from the access point 2 to the terminal device 3 is omitted.

  First, when the power of the access point 2 is turned on, the control unit 20 executes a predetermined initial setting (not shown). In parallel with this process, the wireless communication control unit 23 switches the operation mode of the access point 2 to the power saving mode (step S21), and further switches the operation mode to the second mode of the power saving modes (step S22). ). The second mode is an operation mode for prohibiting wireless communication with the RF circuit 22 in the power saving mode.

  In step S <b> 22, the wireless communication control unit 23 outputs an OFF signal to the RF circuit 22 to turn off the RF circuit 22, thereby prohibiting communication of the RF circuit 22. Thereafter, power consumption in the RF circuit 22 is suppressed until the RF circuit 22 is turned on.

  When step S22 is executed and the operation mode is set to the second mode of the power saving mode, the control unit 20 starts the timer 21 and sets the timer value t3 in the timer 21 (step S23).

  Next, it is determined whether or not the operation mode of the access point 2 is the power saving mode (step S24). If the operation mode is the power saving mode, wireless communication processing in the power saving mode is executed (step S25).

  FIG. 6 is a flowchart showing wireless communication processing in the power saving mode. In the power saving mode, the wireless communication control unit 23 monitors the interrupt signal from the timer 21 and the probe request reception interrupt signal from the RF circuit 22 (steps S31, S34, and S37).

  In the power saving mode, when a signal notifying that the timer value t3 has elapsed from the timer 21 is input, the wireless communication control unit 23 determines Yes in step S31 and switches the operation mode to the first mode (step S32). ).

  The first mode is an operation mode in which the RF circuit 22 can receive at least a probe request transmitted from the terminal device 3 in the power saving mode. In the first mode, it is not always necessary to restore all the functions of the RF circuit 22, as long as at least a probe request is received and the wireless communication control unit 23 can be notified of this.

  In step S <b> 32, the wireless communication control unit 23 outputs an ON signal to the RF circuit 22 and activates the RF circuit 22. Thereby, the access point 2 transits to a state in which at least a probe request from the terminal device 3 can be received.

  When step S32 is executed, the control unit 20 sets a timer value t4 for the timer 21 (step S33). Thus, when the operation mode is switched to the first mode, the timer 21 starts measuring the timer value t4.

  The control unit 20 resets the timer 21 instead of stopping the timer value t3 when the steps S32 and S33 are executed. Therefore, a signal notifying that the timer value t3 has passed periodically is input from the timer 21 to the wireless communication control unit 23 until step S40 described later is executed. That is, the timer value t3 is a parameter indicating a cycle for switching the second mode to the first mode in the power saving mode.

  In the power saving mode, when a signal notifying that the timer value t4 has elapsed from the timer 21 is input, the wireless communication control unit 23 determines Yes in step S34 and switches the operation mode to the second mode (step S35). ). In step S35, the wireless communication control unit 23 outputs an OFF signal to the RF circuit 22 in the same manner as in step S22, thereby turning off the RF circuit 22. Thereby, the communication of the RF circuit 22 is prohibited again.

  When step S35 is executed, the control unit 20 causes the timer 21 to stop measuring the timer value t4 (step S36).

  As described above, in the access point 2 according to the present embodiment, when the operation mode is switched to the first mode in step S32, the timer value t4 is started to be measured in step S33. When the timer value t4 has elapsed (Yes in step S34), the operation mode is switched to the second mode in step S35, and the time measurement of the timer value t4 is stopped in step S36. That is, the timer value t4 is a parameter indicating the duration of the first mode (a mode in which a probe request can be received) in the power saving mode.

  As described above, in the second mode in the power saving mode, the RF circuit 22 is in an OFF state and cannot receive a probe request from the terminal device 3. Therefore, the case where the RF circuit 22 receives the probe request is limited to when the operation mode is the first mode.

  In other words, in the power saving mode, the access point 2 periodically switches between the first mode and the second mode, and only during the timer period t4 (the duration of the first mode) during that one cycle. The probe request cannot be received. Therefore, in order to reliably receive the probe request during the duration of the first mode, the terminal device 3 transmits the probe request at least once during the duration of the first mode at the access point 2. It is preferable to determine the probe request transmission interval (timer value t1). That is, it is preferable that timer value t1 <timer value t4.

  When the RF circuit 22 receives a probe request from the terminal device 3 in the power saving mode, the RF circuit 22 transmits the probe request to the wireless communication control unit 23 as in the case of other received information. If the information transmitted from the RF circuit 22 is a probe request, the wireless communication control unit 23 determines Yes in step S37 accordingly, and switches the operation mode to the normal mode (step S38). Further, the wireless communication control unit 23 controls the RF circuit 22 so as to transmit a response (ACK) to the probe request. Thereby, the RF circuit 22 transmits a response toward the terminal device 3, and communication negotiation is started (step S39).

  When step S39 is executed in the access point 2, the terminal device 3 receives the response transmitted from the access point 2 and thereby determines Yes in step S9 (or step S12), and step S13 (communication negotiation) is performed. Executed. Thereby, the link between the access point 2 and the terminal device 3 is established.

  In parallel with the process of step S39, the control unit 20 causes the timer 21 to stop measuring the timer values t3 and t4 and to start measuring the timer value t5 (step S40).

  The above is the description of step S25 (wireless communication processing in the power saving mode) shown in FIG. Once the operation mode of the access point 2 is set to the power saving mode, step S38 is executed, the operation mode is switched to the normal mode, and the processes in steps S24 and S25 are performed until it is determined No in step S24. Repeated.

  On the other hand, when the operation mode is switched to the normal mode, the wireless communication control unit 23 determines No in step S24, and executes wireless communication processing in the normal mode (step S26). Note that the wireless communication process in the normal mode can be executed as, for example, a normal process in the WiFi standard, and thus description thereof is omitted.

  However, the access point 2 monitors whether information is transmitted to and received from the terminal device 3 by the RF circuit 22 in the normal mode (step S27). If any information is transmitted / received, it is determined as Yes in step S27, and the control unit 20 resets the timer value t5 to the timer 21 (step S28). That is, every time step S28 is executed, the timer 21 starts measuring the timer value t5 from that point.

  Further, in the normal mode, the wireless communication control unit 23 monitors a signal for notifying the elapse of the timer value t5 from the timer 21 (step S29). Then, when the signal is input (Yes in step S29), the wireless communication control unit 23 transmits the fact to the control unit 20. As a result, the control unit 20 causes the timer 21 to stop measuring the timer value t5 (step S30).

  In parallel with the process of step S30, the wireless communication control unit 23 disconnects the link with the terminal device 3, and the access point 2 returns to step S21 and repeats the process. That is, step S21 is executed, and the operation mode is switched to the power saving mode by the wireless communication control unit 23.

  Thus, if the transmission / reception of information with the terminal device 3 is not performed for the time indicated by the timer value t5, the access point 2 in the present embodiment executes step S21 and ends the normal mode. Switch the operation mode to power saving mode.

  When the transmission information cannot be prepared for the terminal device 3 during the timer value t5 in the execution of the application program (for example, when a link is to be secured even after the timer value t5 elapses), the access point 2 The control unit 20 may be configured to reset the timer value t5 with respect to the timer 21 as appropriate. On the other hand, if the terminal device 3 wants to secure a link, if the terminal point 3 transmits some information (link maintenance request information) to the access point 2 before the timer value t5 elapses, the access point 2 The timer value t5 is reset by receiving.

  The above is mainly the operation of the access point 2 in the wireless communication method. Next, a communication sequence when the access point 2 in the power saving mode is activated in the normal mode in the wireless communication method according to the present invention will be described.

  FIG. 7 is a diagram showing a communication sequence when the access point 2 in the power saving mode shifts to the normal mode. In addition, the horizontal axis in FIG. Also, the information amount of the probe request is 49 [bytes], the wireless communication speed is 6 [Mbps], st = 65.3 [μsec], wt = 27.6 [μsec], t1 = 92.9 [μsec], A case where t2 = t3 = 100 [msec] and t4 = 100 [μsec] is illustrated.

  In FIG. 7, each part indicated by a sandy hatch indicates a period during which the terminal device 3 transmits each probe request (transmission time st). The probe request PR1 and the probe request PR2 illustrated in FIG. 7 are two consecutive probe requests among probe requests (probe requests PR1 to PRn) transmitted a plurality of times. For the continuous probe requests PR1 and PR2, the waiting time from when the probe request PR1 that is the previous start request is transmitted until the probe request PR2 that is the subsequent start request is transmitted is as described above. The waiting time is wt.

  In FIG. 7, a hatched portion indicates a period during which information can be received at the access point 2. As already described, the access point 2 is in the first mode only during the timer value t4 at the period t3 in the power saving mode, and becomes a period in which information can be received.

  In a state where the link between the access point 2 and the terminal device 3 is not established (power saving mode), the synchronization between the access point 2 and the terminal device 3 is not maintained. That is, the state of the access point 2 at the time when the terminal device 3 starts transmitting the probe request is undefined.

  The probe requests PR1 and PR2 shown in FIG. 7 are transmitted during the second mode in which the operation mode at the access point 2 is the power saving mode. The probe requests PR1 and PR2 transmitted at such timing are not received by the access point 2, and no response is returned from the access point 2. Therefore, depending on these probe requests, the operation mode is not switched to the normal mode, and the communication negotiation between the access point 2 and the terminal device 3 is not started.

  On the other hand, the probe request PRn transmitted during the first mode of the power saving mode is normally received by the access point 2. Thereby, as shown in FIG. 7, the power saving mode is switched to the normal mode. After the operation mode is switched to the normal mode, the timer values t3 and t4 in the timer 21 are stopped, so that the first mode is not switched to the second mode during the normal mode, and the probe request The RF circuit 22 that is receiving PRn is not switched to the OFF state (the reception enabled state is continued).

  As is apparent from FIG. 7, in the access point 2 according to the present embodiment, in the power saving mode, the RF circuit 22 is activated only during t4 = 100 [μsec] during t3 = 100 [msec]. That is, the startup time of the RF circuit 22 is approximately 0.1% during the power saving mode, and power consumption is suppressed.

  Thus, in the access point 2 of the wireless communication system 1, the power consumption is suppressed as the timer value t4 is smaller than the timer value t3. However, as already described, since it is necessary that st <t1 <t4, the timer value t4 is infinitely small due to the probe request sending time st determined according to the communication speed and the amount of probe request information. I can't do it. On the other hand, when the timer value t4 is made as small as possible, the sending time st is fixed, so that the value of the transmission waiting time wt becomes small.

  In the present embodiment, as is clear from FIG. 7, wt <T. The response time T shown in FIG. 7 indicates the response time of the access point 2 with respect to the probe request PRn. However, this response time is almost constant for any probe request, and the response time for all probe requests can be said to be the response time T.

  As described above, in the terminal device 3 according to the present embodiment, for the two consecutive probe requests among the probe requests transmitted a plurality of times, after the probe request transmitted first is transmitted, the subsequent probe request is transmitted. The RF circuit 32 is controlled so that the transmission waiting time wt until the transmission is completed is shorter than the response time T from the access point 2 to the previously transmitted probe request.

  Note that the relationship of wt <T is satisfied for the transmission waiting time wt in all probe requests other than the probe request PRn that is transmitted last. This means that the next probe request is continuously transmitted without waiting for a response to.

  As already described, when the access point 2 is in the power saving mode, the access point 2 and the terminal device 3 are not synchronized. Therefore, when the first probe request PR1 is transmitted, the operation mode of the access point 2 is naturally the first mode. In this case, a response to the probe request PR1 is transmitted from the access point 2, and this response is received after the terminal device 3 transmits at least the probe request PR2.

  As described above, the wireless communication system 1 according to the present embodiment is a system that performs wireless communication between the terminal device 3 and the access point (relay unit) 2, and the terminal device 3 is connected to the access point 2. And an RF circuit 32 that transmits a probe request, which is a request for starting wireless communication, and the access point 2 is an RF circuit that performs wireless communication with the terminal device 3. 22 and a wireless communication control unit 23 that switches an operation mode of the access point 2 between a normal mode and a power saving mode in which the power consumption of the access point 2 is suppressed more than the power consumption in at least the normal mode; The wireless communication control unit 23 transmits at least a probe request transmitted from the terminal device 3 in the power saving mode to the RF circuit 22. A first mode in which a receivable state, switches the second mode for prohibiting communication by the wireless to the RF circuit 22. Thereby, in the second mode of the power saving mode, wireless communication by the RF circuit 22 is prohibited, so that power consumption in the RF circuit 22 during that period is suppressed compared to the normal mode. Therefore, the power consumption of the access point 2 can be suppressed.

  In the second mode, the RF circuit 22 can suppress the power required to confirm the presence / absence of received information by stopping monitoring whether or not the information transmitted from the terminal device 3 has been received.

  Further, in the second mode, the RF circuit 22 can suppress power necessary for transmitting the beacon signal by stopping the transmission of the beacon signal.

<2. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above-described embodiment, the control unit 20 and the wireless communication control unit 23 of the access point 2 are described as separate configurations, and an example in which the RF circuit 22 and the wireless communication control unit 23 configure a so-called communication module has been described. . However, the control unit 20 may have the configuration and function of the wireless communication control unit 23. Alternatively, the wireless communication control unit 23 may be configured to have a part of the function of the control unit 20 and, for example, the timer 21 may be controlled.

  In addition, the terminal device 3 in the above embodiment has a constant timer value t1, whereby the probe request is transmitted at the period t1, and the probe request is transmitted almost completely periodically. However, the timer value t1 is not necessarily constant, and is appropriately controlled (for example, the timer value t1 is periodically changed) by the wireless communication control unit 33 so that the probe request is efficiently received by the access point 2. May be controlled).

  Moreover, each process shown in the said embodiment is an illustration to the last, and if the same effect is acquired, it may be changed suitably.

DESCRIPTION OF SYMBOLS 1 Wireless communication system 2 Access point 20,30 Control part 21,31 Timer 22,32 RF circuit 23,33 Wireless communication control part 3 Terminal device 9 Communication cable

Claims (10)

A wireless communication system that performs wireless communication between a terminal device and a repeater,
The terminal device
The first communication means for performing the wireless communication with the repeater and transmitting a request for starting the wireless communication,
The repeater is
Second communication means for performing wireless communication with the terminal device;
Switching means for switching the operation mode of the repeater between a normal mode and a power saving mode in which the power consumption of the repeater is suppressed at least than the power consumption in the normal mode;
With
The switching means performs wireless communication with the second communication means in a first mode in which the second communication means can receive at least a start request transmitted from the terminal device in the power saving mode. A wireless communication system, characterized by switching between a second mode to be prohibited. The wireless communication system according to claim 1,
The terminal device further includes first control means for controlling the first communication means to transmit the wireless communication start request a plurality of times,
The first control means, for two consecutive start requests among the start requests transmitted a plurality of times, a waiting time from when a previous start request is transmitted until a subsequent start request is transmitted, A wireless communication system, characterized in that the first communication means is controlled so that a time shorter than a response time from the repeater with respect to a previous start request is obtained. The wireless communication system according to claim 1 or 2,
In the first mode, the switching unit switches the power saving mode to the normal mode after the second communication unit receives a start request transmitted from the terminal device. A wireless communication system according to any one of claims 1 to 3,
In the second mode, the second communication unit stops monitoring whether or not information transmitted from the terminal device has been received. A wireless communication system according to any one of claims 1 to 4,
In the second mode, the second communication means stops transmitting a beacon signal. A wireless communication system according to any one of claims 1 to 5,
The wireless communication system, wherein the repeater further includes second control means for controlling a switching timing between the first mode and the second mode by the switching means. The wireless communication system according to claim 6,
The wireless communication system, wherein the second control means controls the switching timing so that the first mode and the second mode are periodically switched. A terminal device that performs wireless communication with a repeater,
A communication means for performing the wireless communication with the repeater and transmitting a request for starting the wireless communication;
Control means for controlling the communication means to transmit the wireless communication start request multiple times;
With
The control means, for the two consecutive start requests among the start requests transmitted a plurality of times, the waiting time from when the previous start request is transmitted until the subsequent start request is transmitted is A terminal device, characterized in that the communication means is controlled so that a time shorter than a response time from the repeater to a start request is obtained. A relay that performs wireless communication with a terminal device,
Communication means for performing wireless communication with the terminal device;
Switching means for switching the operation mode of the repeater between a normal mode and a power saving mode in which the power consumption of the repeater is suppressed at least than the power consumption in the normal mode;
With
In the power saving mode, the switching means includes a first mode in which the communication means can receive at least the wireless communication start request transmitted from the terminal device, and wireless communication with the communication means. A repeater that switches to a second mode that prohibits the operation. A wireless communication method for realizing wireless communication between a terminal device and a repeater,
(a) switching the operation mode of the repeater from the normal mode to a power saving mode in which the power consumption of the repeater is suppressed more than the power consumption in at least the normal mode;
(b) When the operation mode of the relay device is the power saving mode, the operation mode of the relay device is a state in which the relay device can receive at least the wireless communication start request transmitted from the terminal device. A step of switching between a first mode that becomes and a second mode that prohibits the wireless communication to the repeater;
(c) For two consecutive start requests among the wireless communication start requests transmitted a plurality of times, the waiting time from when the previous start request is transmitted until the subsequent start request is transmitted is A step of transmitting the wireless communication start request a plurality of times so as to be shorter than the response time from the repeater to the previous start request;
A wireless communication method comprising:

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