JP4670457B2 - Wireless LAN terminal, wireless LAN system, and state transition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless LAN terminal the power consumption of which is reduced by shifting a state in response to timing when a beacon arrives. <P>SOLUTION: An arrival time estimate section 7 calculates a time difference between timing when a communication section 6 receives a beacon from an AP 1 and timing when the communication section 6 should receive the beacon, and estimates a beacon delay time denoting the delay time of the arrival of the beacon by using the calculated time difference. A wake time determining section 8 uses the beacon delay time to determine an Awake state time. A control section 9 is shifted to the Awake state at an interval of a prescribed time and shifted to a Doze state after a lapse of the Awake state time. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a wireless LAN terminal synchronized with a wireless LAN base station using a beacon, a wireless LAN system including such a wireless LAN terminal, and a state transition method in such a wireless LAN terminal.

  In order to synchronize communication with an access point that is a wireless LAN base station, such as a wireless LAN terminal in a wireless LAN system compatible with the IEEE 802.11 specification, the access point transmits at a constant time interval (for example, 100 ms interval). There is a wireless LAN terminal that receives a beacon.

  As operation modes in the wireless LAN terminal, there are a power saving mode (hereinafter also referred to as “Doze state”) that consumes little power and a full operation mode (hereinafter also referred to as “Awake state”) in which information can be transmitted and received. As a wireless LAN terminal, there is a wireless LAN terminal configured to transition from a Doze state to an Awake state or a power-on state in synchronization with a certain time interval at which a beacon is transmitted in order to save power consumption (for example, , See Patent Document 1 and Patent Document 2.)

JP 2004-264667 A (paragraphs 0007 to 0049, FIG. 1) Japanese Patent Laid-Open No. 9-162798 (paragraphs 0037 to 0073, FIG. 1)

  Consider a problem in a wireless LAN terminal in which the control state (operation mode) becomes an awake state at regular intervals. FIG. 5 is a timing diagram for explaining the state transition of the wireless LAN terminal in which the control state becomes the awake state at regular time intervals. The wireless LAN terminal cannot transmit / receive information in the Doze state. Due to the influence of surrounding radio wave conditions, the time for the beacon to reach the wireless LAN terminal may be delayed with respect to the scheduled reception time. FIG. 6 is a timing diagram for explaining a case where the beacon arrives at the wireless LAN terminal later than the scheduled reception time. In the example shown in FIG. 6, the first beacon is delayed by X1, the second beacon is delayed by X2, and the third beacon is delayed by X3. When the delay as shown in FIG. 6 occurs, there is a problem that the wireless LAN terminal that performs the state transition as shown in FIG. 5 cannot receive the beacon that arrives after the awake state ends. In order to solve such a problem, it is conceivable that the wireless LAN terminal is configured to continue the awake state until a beacon is received, and to change the control state from the awake state to the doze state when the beacon is received.

  However, with such a configuration, if the wireless LAN terminal cannot move and / or receive a beacon from the access point, the wireless LAN terminal transitions to the Doze state until the next beacon is received as shown in FIG. do not do. Therefore, there is a problem that the awake state is continued until the beacon is received and the power consumption increases. FIG. 7 is a timing chart for explaining state transition when the wireless LAN terminal cannot receive a beacon.

  In order to solve such a problem, it can be considered that the wireless LAN terminal is configured to continue the awake state for a relatively long predetermined time. However, even in such a configuration, a beacon that arrives after a predetermined time cannot be received as shown in FIG. Also, when the wireless LAN terminal moves out of the access point range, a predetermined time is always required to detect that the beacon cannot be received, that is, that the wireless LAN terminal has moved out of the access point range. As a result, power consumption increases. FIG. 8 is a timing chart for explaining state transitions when a beacon arrives after a predetermined time.

  Further, Patent Document 1 discloses that a time expected to receive a response to transmitted information has elapsed, scanning for confirming whether information can be transmitted / received to / from the access point is completed, A method is described in which when a beacon indicates that information to be transmitted to the wireless LAN terminal is not stored, a transition to the Doze state is performed.

  However, the method described in Patent Document 1 transitions to the Doze state when a time expected to receive a response to transmitted information elapses due to the influence of surrounding radio wave conditions and the like. Then, there is a problem that the wireless LAN terminal cannot receive a beacon.

  In addition, the mobile station described in Patent Document 2 cannot receive a beacon if the timing at which the beacon arrives at the mobile station shifts due to the influence of surrounding radio wave conditions and the like. There is.

  Accordingly, an object of the present invention is to provide a wireless LAN terminal, a wireless LAN system, and a state transition method that can reliably receive a beacon while suppressing power consumption.

The wireless LAN terminal according to the present invention includes a communication means for receiving information from a wireless LAN base station and transmitting information to the wireless LAN base station, and a control state from a power saving state at a timing at which a beacon should be received from the wireless LAN base station. A wireless LAN terminal comprising a state transition means for transitioning to a normal operation state, a delay time estimation means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from a wireless LAN base station The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means, and the delay time estimation means should receive a beacon from the wireless LAN base station. Calculate the maximum difference between the timing and the timing when the communication means received the beacon transmitted by the wireless LAN base station. And estimating the calculated maximum delay as the time.

A wireless LAN terminal according to another aspect of the present invention includes a communication unit that receives information from a wireless LAN base station and transmits information to the wireless LAN base station, and a control state at a timing at which a beacon is received from the wireless LAN base station. A wireless LAN terminal comprising a state transition means for transitioning from a power saving state to a normal operation state, and a delay for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from a wireless LAN base station A time estimation means, and the state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means, and the delay time estimation means is transmitted by the wireless LAN base station. The delay time is estimated based on the number of wireless LAN terminals belonging to the wireless LAN base station, which is information included in the beacon And wherein the door.

According to another aspect of the present invention, there is provided a wireless LAN terminal that is configured to receive information from a wireless LAN base station and transmit information to the wireless LAN base station, and to control a state in which a beacon should be received from the wireless LAN base station. A wireless LAN terminal comprising a state transition means for transitioning a power supply from a power saving state to a normal operation state, and estimating a delay time of an actual beacon reception timing with respect to a timing at which a beacon is to be received from a wireless LAN base station A delay time estimating means, and the state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means, and according to the delay time estimated by the delay time estimation means. And a normal operation state duration determination means for determining a normal operation time which is a time during which the normal operation state is continued. The transition of the control state from the normal operation state to the power saving state occurs after the normal operation time determined by the normal operation state duration determination means has elapsed since the control state was transitioned from the power saving state to the normal operation state. Features.

According to another aspect of the present invention, there is provided a wireless LAN terminal that is configured to receive information from a wireless LAN base station and transmit information to the wireless LAN base station, and to control a state in which a beacon should be received from the wireless LAN base station. A wireless LAN terminal comprising a state transition means for transitioning a power supply from a power saving state to a normal operation state, and estimating a delay time of an actual beacon reception timing with respect to a timing at which a beacon is to be received from a wireless LAN base station A delay time estimating means, wherein the state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means; The difference between the timing when a beacon should be received and the timing when the communication means receives the beacon transmitted by the wireless LAN base station Normal operation state duration time for calculating the average value, estimating the calculated average value as the delay time, and determining the normal operation time, which is the time for continuing the normal operation state, according to the delay time estimated by the delay time estimation means The state transition means includes a determination means, and when the normal operation time determined by the normal operation state duration determination means elapses after the control state is changed from the power saving state to the normal operation state, the control state is changed from the normal operation state. It is characterized by making a transition to a power saving state.

In accordance with the delay time estimated by the delay time estimation means, it includes a normal operation state duration determination means for determining a normal operation time that is a time for continuing the normal operation state, and the state transition means changes the control state from the power saving state. When the normal operation time determined by the normal operation state duration determination unit has elapsed after the transition to the normal operation state, the control state may be shifted from the normal operation state to the power saving state.

The normal operation state duration determination unit may determine a normal operation time by multiplying the delay time estimated by the delay time estimation unit by a predetermined value.

The normal operation state duration determination unit may determine a time obtained by adding a predetermined value to the delay time estimated by the delay time estimation unit as the normal operation time.

A wireless LAN system according to the present invention includes a wireless LAN base station that transmits beacons at regular time intervals, a communication unit that receives information from the wireless LAN base station and transmits information to the wireless LAN base station, and a wireless LAN base station. A wireless LAN system including a wireless LAN terminal including state transition means for transitioning a control state from a power saving state to a normal operation state at a timing when a beacon is to be received, wherein the wireless LAN terminal receives a beacon from a wireless LAN base station. Delay time estimation means for estimating the delay time of the timing for actually receiving the beacon with respect to the timing to be received is provided, and the state transition means changes the control state from the normal operation state according to the delay time estimated by the delay time estimation means. Transition to power saving state, delay time estimation means should receive beacon from wireless LAN base station And timing, calculates the maximum value of the difference between the timing at which the wireless LAN base station receives the communication means beacons transmitted, and estimates the maximum value calculated delay as the time.

A state transition method according to the present invention is a state transition method in a wireless LAN terminal that changes a control state from a power saving state to a normal operation state at a timing when a beacon is to be received from a wireless LAN base station. And the maximum difference between the timing when the communication means receives the beacon transmitted by the wireless LAN base station and the calculated maximum value with respect to the timing when the beacon is received from the wireless LAN base station. It is estimated as a delay time of the timing of actually receiving a beacon, and the control state is changed from the normal operation state to the power saving state according to the estimated delay time.

A state transition method according to another aspect of the present invention is a state transition method in a wireless LAN terminal for transitioning a control state from a power saving state to a normal operation state at a timing at which a beacon is to be received from a wireless LAN base station. Calculate the average value of the difference between the timing when the beacon should be received from the base station and the timing when the communication means received the beacon transmitted by the wireless LAN base station, and receive the calculated average value from the wireless LAN base station. Estimated as the delay time of the actual beacon reception timing with respect to the timing to be determined, determine the normal operation time, which is the time to continue the normal operation state, according to the estimated delay time, and change the control state from the power saving state to normal After the transition to the operation state, when the determined normal operation time elapses, the control state is changed from the normal operation state to the power saving state. And wherein the causing the transfer.

  According to the present invention, since the control state is shifted from the normal operation state to the power saving state according to the delay time of the timing for actually receiving the beacon with respect to the timing for receiving the beacon from the wireless LAN base station, the power consumption is further reduced. It can be effectively saved.

  The delay time estimating means is configured to estimate the delay time based on a difference between a timing at which a beacon should be received from the wireless LAN base station and a timing at which the communication means has received a beacon transmitted by the wireless LAN base station. In the case of being present, the delay time can be estimated according to the timing at which the communication means actually receives the beacon, so the delay time can be estimated according to the actual radio wave condition or the like.

  The timing at which the wireless LAN base station transmits a beacon depends on the number of wireless LAN terminals to which the wireless LAN base station belongs. Therefore, the delay time estimating means calculates the delay time based on the number of wireless LAN terminals belonging to the wireless LAN base station. When configured to estimate, the delay time can be estimated according to the timing at which the wireless LAN base station transmits a beacon.

  The normal operation state duration determination means determines the normal operation time according to the estimated delay time, and the state transition means transitions from the power saving state to the normal operation state after the normal operation time elapses. When the control state is configured to transition from the normal operation state to the power saving state, the normal operation state is continued until the normal operation time corresponding to the estimated delay time elapses. Leakage can be prevented.

Embodiment 1 FIG.
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a configuration example of a first embodiment of a wireless LAN system according to the present invention.

  The embodiment of the present invention includes an AP (access point) 1 that is a wireless LAN base station, and a wireless LAN terminal 2, a wireless LAN terminal 3, and a wireless LAN terminal 4 that exchange information with the AP 1.

  The AP 1 transmits a beacon every time a predetermined time (beacon transmission time interval) elapses in order to synchronize the timing of transmitting and receiving information with the wireless LAN terminals 2 to 4. The operation modes of the wireless LAN terminals 2 to 4 are two states: an Awake state that is a normal operation state in which information can be transmitted / received to / from AP1, and a Doze state that is a state in which information is not transmitted / received to / from AP1 and almost no power is consumed. There is a state. The wireless LAN terminals 2 to 4 can receive a beacon in the Awake state, but cannot receive a beacon in the Doze state. The wireless LAN terminals 2 to 4 change the operation mode from the Doze state to the Awake state at the time when the beacon transmitted by the AP 1 is expected to arrive at the wireless LAN terminals 2 to 4 (reception scheduled time). Note that the Awake state is defined as a state in which only reception is possible, and a transmission / reception enabled state different from the Awake state may be defined. However, here, it is assumed that the awake state is a state in which both transmission and reception are possible. Further, the present invention can be applied even when the awake state is defined as a state in which transmission is not possible and only reception is possible.

  FIG. 2 is a block diagram illustrating a configuration example of the wireless LAN terminal 2 according to the embodiment of this invention. The wireless LAN terminal 2 according to the embodiment of the present invention uses a communication unit (communication means) 6 that receives information from the AP 1 using the antenna 5 and transmits information to the wireless LAN base station. Based on the difference between the arrival time of the received beacon and the scheduled reception time, a beacon delay time estimation unit that estimates a beacon delay time that is a delay time of the actual beacon reception timing with respect to the timing at which the beacon is received from AP1 Delay time estimation means) 7, Awake time determination section (normal operation state duration means) that determines the Awake state time, which is the duration of the Awake state, based on the arrival delay time of the beacon estimated by the beacon delay time estimation section 7 8 and a control unit (state transition means) 9 for controlling each unit.

  The beacon delay time estimation unit 7, the awake time determination unit 8, and the control unit 9 are realized by a CPU that executes processing according to program control.

  When the communication unit 6 receives a beacon, the beacon delay time estimation unit 7 receives a beacon scheduled reception time (timing to receive a beacon from AP1) and a time when the communication unit 6 actually receives a beacon (AP1 transmitted). The time difference from the timing of receiving the beacon is calculated, and the beacon delay time is estimated based on the calculation result. Specifically, referring to the example shown in FIG. 6, three of X1, X2, and X3 are calculated, and the beacon delay time is estimated based on the calculation result.

  Note that the beacon delay time estimation unit 7 estimates the beacon delay time based on the three calculation results. You may estimate beacon delay time based on the calculation result of other frequency | counts, such as the past 10 times.

  Specifically, the beacon delay time estimation unit 7 estimates, for example, that the average time of the calculated time difference or the maximum time is the beacon delay time. That is, the beacon delay time estimation unit 7 estimates the beacon delay time X as X = Max (X1, X2, X3) or estimates as X = Avg (X1, X2, X3). Here, setting X to the maximum value among X1, X2, X3,..., Xn is expressed as X = Max (X1, X2, X3,..., Xn). Moreover, letting X be the average value of X1, X2, X3,..., Xn is expressed as X = Avg (X1, X2, X3,..., Xn).

  When the beacon transmission time interval is information included in the beacon, the control unit 9 obtains the beacon transmission time interval from the beacon received via the communication unit 6, and the beacon is transmitted at the time when the beacon is actually received. The time when the transmission time interval is added can be set as the reception time of the next beacon. In addition, the control unit 9 calculates a beacon transmission time interval from a plurality of beacons received via the communication unit 6, and adds the calculated beacon transmission time interval to the time when the beacon is actually received. It can be the scheduled reception time of the beacon.

  The awake time determination unit 8 determines the product or sum of the beacon delay time calculated by the beacon delay time estimation unit 7 and a predetermined safety constant as the awake state time. That is, the awake time determination unit 8 determines the awake state time T = safety constant A × beacon delay time X or the awake state time T = safety constant A + beacon delay time X. The predetermined safety constant is a value larger than 1 when multiplied by the beacon delay time X. When added to the beacon delay time X, the predetermined safety constant can be determined based on the beacon transmission time interval, and may be a fraction of the beacon transmission time interval, for example. In this embodiment, the safety constant A is considered when determining the Awake state time T. However, the beacon delay time X may be used as it is as the Awake state time T.

  The control unit 9 controls the control state (operation mode). That is, the operation mode is changed from the Doze state to the Awake state in synchronization with the beacon transmission time interval. Specifically, when the scheduled reception time corresponding to the timing at which a beacon is to be received from AP1, the operation mode is changed from the Doze state to the Awake state. More specifically, the control unit 9 makes a transition from the Doze state to the Awake state immediately before the scheduled reception time. In addition, after the transition from the Doze state to the Awake state, the Awake state is continued until the Awake state time determined by the Awake time determination unit 8 has elapsed unless a beacon is received. When the awake state time elapses or when a beacon is received before the awake state time elapses, the operation mode is changed to the doze state. In the Awake state, the control unit 9 supplies power to a circuit such as an IC that implements the communication unit 6. And the control part 9 stops supply of electric power to circuits, such as IC which implement | achieves the communication part 6, in a Doze state, and reduces electric power consumption.

Next, the operation of the first exemplary embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a flowchart showing the operation of the wireless LAN terminal 2. The configuration and operation of the wireless LAN terminal 3 and the wireless LAN terminal 4 are the same as the configuration and operation of the wireless LAN terminal 2.
If the received beacon includes data indicating that there is a message addressed to the terminal itself, the wireless LAN terminal 2 requests a message by continuing the awake state and transmitting a polling frame to AP1. To do. Then, after receiving a message from AP1, the state transits to the Doze state. However, FIG. 3 shows an operation only when the beacon does not include data indicating that there is a message addressed to the own terminal.

  First, the control unit 9 sets the operation mode to the Doze state (step S101). When the scheduled reception time is reached (step S102), the operation mode is changed to the awake state (step S103). If the scheduled reception time is unknown immediately after the wireless LAN terminal 2 starts operating, the operation mode is set to the Awake state until the first beacon is received.

  In the awake state, when the awake state time has elapsed without the communication unit 6 receiving a beacon, the control unit 9 changes the operation mode from the awake state to the doze state (steps S104 and S101). When the communication unit 6 receives a beacon in the awake state (step S105), the control unit 9 determines the time at that time, that is, the time when the beacon is actually received and the scheduled reception time, the beacon delay time estimation unit 7 Notify The beacon delay time estimation unit 7 estimates the beacon delay time by the method described above. The beacon delay time is notified to the awake time determination unit 8. The awake time determination unit 8 determines the awake state time by the method described above (step S106).

  As described above, according to this embodiment, the communication unit 6 changes the communication mode from the awake state to the doze state according to the beacon delay time. Therefore, the wireless LAN terminal 2 can reliably receive a beacon and reduce power consumption.

  The beacon delay time estimation unit 7 estimates the beacon delay time every time the communication unit 6 receives a beacon, and the awake time determination unit 8 determines the awake state time based on the estimated beacon delay time. Therefore, the Awake state time can be dynamically changed to an appropriate value in accordance with changes in surrounding radio wave conditions. As a result, it is always possible to reliably receive a beacon and maintain power consumption.

Embodiment 2. FIG.
In the first embodiment, the wireless LAN terminals 2 to 4 estimate the beacon delay time from the time difference between the timing at which the beacon is received from AP1 and the timing at which the beacon transmitted by AP1 is received. The beacon delay time may be estimated by In the second embodiment, the beacon delay time is estimated based on information included in the beacon.

  The beacon delay transmitted by AP1 tends to monotonously increase as the number of belonging wireless LAN terminals, that is, the number of wireless LAN terminals communicating with AP1 increases. Therefore, the awake time determination unit 8 can estimate the beacon delay time based on the number of wireless LAN terminals belonging to AP1. In this embodiment, the AP 1 includes information indicating the number of belonging wireless LAN terminals in the beacon.

  FIG. 4 is a flowchart showing the operation of the wireless LAN terminal 2 that estimates the beacon delay time based on the number of belonging wireless LAN terminals. The configuration and operation of the wireless LAN terminal 3 and the wireless LAN terminal 4 are the same as the configuration and operation of the wireless LAN terminal 2. The hardware configuration of the wireless LAN terminals 2 to 4 is the same as that shown in FIG.

  In the wireless LAN terminal 2, when the beacon is received, the beacon delay time estimation unit 7 sets a time corresponding to the number of wireless LAN terminals included in the beacon as a beacon delay time. For example, in the beacon delay time estimation unit 7, the relationship between the number of wireless LAN terminals and the beacon delay time is set in a table format in advance. The beacon delay time estimation unit 7 extracts a time corresponding to the number of wireless LAN terminals from the table. Then, the extracted time is estimated as the beacon delay time. The Awake time determination unit 8 determines the Awake state time from the safety constant A and the beacon delay time X, as in the case of the first embodiment. The above process is executed in step S108.

  Note that in FIG. 4, considering the existence of an AP that does not include information indicating the number of belonging wireless LAN terminals in the beacon, the program installed in the wireless LAN terminal 2 includes steps S107 and S107. It is shown that a program part for executing the process of S106 is also included. However, in this embodiment, the processing of steps S106 and S107 may not be performed.

  In this embodiment, the relationship between the number of wireless LAN terminals and the beacon delay time is set in a table format in the wireless LAN terminal 2, but such a table may be mounted on the AP1 side. In this case, the AP 1 transmits beacons including information indicating the beacon delay time to the wireless LAN terminals 2 to 4 instead of the information indicating the number of belonging wireless LAN terminals. In the wireless LAN terminals 2 to 4, the wake time determination unit 8 determines the wake state time from the safety constant A and the beacon delay time included in the beacon received by the communication unit 6.

  As described above, in this embodiment, since the wireless LAN terminals 2 to 4 estimate the delay time based on the information indicating the number of wireless LAN terminals belonging to AP1, the delay time estimation process is simplified. Is done.

It is a block diagram which shows the structural example of the wireless LAN system by this invention. It is a block diagram which shows the structural example of the wireless LAN terminal of embodiment of this invention. 4 is a flowchart illustrating an operation of the wireless LAN terminal according to the first embodiment. 6 is a flowchart illustrating an operation of a wireless LAN terminal according to the second embodiment. It is a timing diagram for demonstrating the transition of the state of the conventional wireless LAN terminal. It is a timing diagram for explaining a case where the beacon arrives at the wireless LAN terminal later than the scheduled reception time. FIG. 6 is a timing diagram for explaining state transition when a wireless LAN terminal fails to receive a beacon. It is a timing diagram for explaining a state transition when a beacon arrives after a predetermined time.

Explanation of symbols

1 AP
2, 3, 4 Wireless LAN terminal 5 Antenna 6 Communication unit 7 Beacon delay time estimation unit 8 Awake time determination unit 9 Control unit

Claims (10)

Communication means for receiving information from the wireless LAN base station and transmitting information to the wireless LAN base station, and state transition for transitioning the control state from the power saving state to the normal operation state at the timing when the beacon should be received from the wireless LAN base station In a wireless LAN terminal comprising means,
A delay time estimating means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from the wireless LAN base station;
The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means ,
The delay time estimating means calculates a maximum value of a difference between a timing at which a beacon is received from a wireless LAN base station and a timing at which a communication means receives a beacon transmitted by the wireless LAN base station, and calculates the maximum A wireless LAN terminal that estimates a value as a delay time . Communication means for receiving information from the wireless LAN base station and transmitting information to the wireless LAN base station, and state transition for transitioning the control state from the power saving state to the normal operation state at the timing when the beacon should be received from the wireless LAN base station In a wireless LAN terminal comprising means,
A delay time estimating means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from the wireless LAN base station;
The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means,
The delay time estimation means estimates the delay time based on the number of wireless LAN terminals belonging to the wireless LAN base station, which is information included in the beacon transmitted by the wireless LAN base station.
A wireless LAN terminal characterized by the above. Communication means for receiving information from the wireless LAN base station and transmitting information to the wireless LAN base station, and state transition for transitioning the control state from the power saving state to the normal operation state at the timing when the beacon should be received from the wireless LAN base station In a wireless LAN terminal comprising means,
A delay time estimating means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from the wireless LAN base station;
The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means,
In accordance with the delay time estimated by the delay time estimation means, normal operation state duration determination means for determining a normal operation time that is a time for continuing the normal operation state,
The state transition means transitions the control state from the power saving state to the normal operation state, and when the normal operation time determined by the normal operation state duration determination means has elapsed, the control state is changed from the normal operation state to the power saving state. Transition to
A wireless LAN terminal characterized by the above. Communication means for receiving information from the wireless LAN base station and transmitting information to the wireless LAN base station, and state transition for transitioning the control state from the power saving state to the normal operation state at the timing when the beacon should be received from the wireless LAN base station In a wireless LAN terminal comprising means,
A delay time estimating means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from the wireless LAN base station;
The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means,
The delay time estimating means calculates an average value of a difference between a timing at which a beacon is received from a wireless LAN base station and a timing at which a communication means receives a beacon transmitted by the wireless LAN base station, and calculates the average Estimate the value as delay time,
In accordance with the delay time estimated by the delay time estimation means, normal operation state duration determination means for determining a normal operation time that is a time for continuing the normal operation state,
The state transition means transitions the control state from the power saving state to the normal operation state, and when the normal operation time determined by the normal operation state duration determination means has elapsed, the control state is changed from the normal operation state to the power saving state. Transition to
A wireless LAN terminal characterized by the above. Normal operation state duration determination means for determining a normal operation time, which is a time for continuing the normal operation state, according to the delay time estimated by the delay time estimation means,
The state transition means changes the control state from the normal operation state to the power saving state when the normal operation time determined by the normal operation state duration determination means elapses after the control state is changed from the power saving state to the normal operation state. The wireless LAN terminal according to claim 1 or 2, wherein a transition is made. The wireless LAN according to any one of claims 3 to 5, wherein the normal operation state duration determination unit determines a time obtained by multiplying the delay time estimated by the delay time estimation unit by a predetermined value as a normal operation time. Terminal. The wireless LAN according to any one of claims 3 to 5, wherein the normal operation state duration determination unit determines a time obtained by adding a predetermined value to the delay time estimated by the delay time estimation unit as the normal operation time. Terminal. A wireless LAN base station that transmits beacons at regular time intervals;
Communication means for receiving information from the wireless LAN base station and transmitting information to the wireless LAN base station, and state transition for transitioning the control state from the power saving state to the normal operation state at the timing when the beacon should be received from the wireless LAN base station In a wireless LAN system including a wireless LAN terminal including means,
The wireless LAN terminal is
A delay time estimating means for estimating a delay time of a timing for actually receiving a beacon with respect to a timing for receiving a beacon from the wireless LAN base station;
The state transition means transitions the control state from the normal operation state to the power saving state according to the delay time estimated by the delay time estimation means ,
The delay time estimating means calculates a maximum value of a difference between a timing at which a beacon is received from a wireless LAN base station and a timing at which a communication means receives a beacon transmitted by the wireless LAN base station, and calculates the maximum Estimate value as delay time
A wireless LAN system characterized by the above. A state transition method in a wireless LAN terminal that transitions a control state from a power saving state to a normal operation state at a timing at which a beacon should be received from a wireless LAN base station,
A maximum value of a difference between a timing at which a beacon is received from a wireless LAN base station and a timing at which a communication unit receives a beacon transmitted from the wireless LAN base station is calculated, and the calculated maximum value is calculated as the wireless LAN base Estimated as the delay time of the actual reception of the beacon relative to the timing of receiving the beacon from the station,
A state transition method characterized by transitioning a control state from a normal operation state to a power saving state according to an estimated delay time. A state transition method in a wireless LAN terminal that transitions a control state from a power saving state to a normal operation state at a timing at which a beacon should be received from a wireless LAN base station,
An average value of a difference between a timing at which a beacon is received from a wireless LAN base station and a timing at which a communication unit receives a beacon transmitted by the wireless LAN base station is calculated, and the calculated average value is calculated as the wireless LAN base. Estimated as the delay time of the actual reception of the beacon relative to the timing of receiving the beacon from the station,
According to the estimated delay time, determine the normal operation time, which is the time to continue the normal operation state,
When the determined normal operation time elapses after the control state is changed from the power saving state to the normal operation state, the control state is changed from the normal operation state to the power saving state.
A state transition method characterized by that.

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