JP2012129655A - Communication apparatus and its control method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication apparatus which can reduce occurrence of packet losses even when power saving mode does not work as stipulated, and a control method therefor.SOLUTION: The communication apparatus has a power saving mode in which an active state for receiving data from some other communication apparatus and a snooze state for not receiving data from the other communication apparatus are switched over in a time-multiplexed manner as it communicates. In the power saving mode, if control information is received from the other communication apparatus and the received control information indicates that data to be acquired from the other communication apparatus exists, the communication apparatus requests data from the other communication apparatus. If a prescribed time elapses while the communication apparatus, after receiving control information indicating that data to be acquired exists, not receiving the data it requested from the other communication apparatus, the communication apparatus has its operation mode transitioned from the power saving mode to another mode in which the active state continues.

Description

  The present invention relates to a communication apparatus, a control method, and a program that can configure a wireless network.

  In recent years, products equipped with wireless communication typified by wireless LAN compliant with the IEEE802.11 series are rapidly spreading. Products equipped with a wireless LAN include portable devices such as cameras and PDAs (Personal Digital Assistants). Many portable devices are battery-powered, and power saving is one of the challenges for these devices.

  In response to this problem, the IEEE802.11 specification defines a power saving mode (power saving enabled) in addition to the normal mode (power saving disabled) in which the wireless interface is always enabled (active state) (non-patented). Reference 1). In the power saving mode, the wireless interface is switched between enabled and disabled (Doze state) by intermittent processing that performs transmission / reception only under specific conditions, realizing low power consumption.

  However, in order to use the power saving mode, there is a problem regarding data loss due to the transition of the power saving state (Active state, Doze state). In order to solve this problem, the following proposals are made in Patent Document 1 and Patent Document 2.

  Patent Document 1 discloses an example of a control method related to power saving in the ad hoc mode. In the IEEE802.11 specification, an infrastructure mode for communicating with other communication devices (stations) via a wireless LAN base station (access point) and an ad hoc mode for communicating between the stations are defined. In Patent Document 1, an ad hoc network is configured between stations, and when a new station joins the network, data is prevented from being lost by shifting from the power saving mode to the normal mode.

  Patent Document 2 discloses an example of a control method related to power saving in the infrastructure mode. In Patent Document 2, a station in a power saving mode transitions to an Active state in order to receive Beacon, which is periodic control information of a wireless LAN, from an access point according to the IEEE 802.11 specification. Next, the station transmits a data transmission request (PS-Poll) for the station to the access point. The access point transmits an acknowledgment (ACK) to PS-Poll to the station. When there is data for the station, a data frame including the data is transmitted to the station, and when there is no data for the station, a data frame without content (Null DATA) is transmitted to the station. By receiving the data frame requested by PS-Poll, the station can complete a series of frame exchange procedures, and when there is no data for the station at the access point, it can transition to the Doze state. .

JP 2006-135549 A JP 2008-048429 A

IEEE std 802.11

  However, in the communication device of Patent Document 1, data loss other than when a new station participates in a network configured in the power saving mode is not considered. In Patent Document 2, it is assumed that the access point transmits Null DATA that does not comply with IEEE 802.11, and it is difficult to implement without changing the existing access point. There are also access points (problem access points) that do not operate correctly according to the IEEE802.11 specification. As a result, there is a problem that even if there is no problem in the communication device, packet loss frequently occurs and the system does not operate correctly. FIG. 11 is a sequence diagram illustrating an example of a communication failure that occurs between an access point that does not operate correctly according to the IEEE802.11 specification and a conventional communication device.

  A communication device operating in the power saving mode transitions from the Dose state to the Active state in order to receive Beacon from the access point in accordance with the IEEE802.11 specification. Next, the communication apparatus receives Beacon (F1101). In Beacon, there is a TIM (Traffic Indication Map) field indicating whether data for the station is buffered in the access point. When the communication device recognizes that the data to the station is not buffered (OFF) by referring to the TIM field, the communication device transits to the Doze state. Next, the communication device operating in the power saving mode transitions from the Dose state to the Active state at the timing of receiving periodic Beacon, and receives Beacon from the access point (F1102). When the communication device refers to the TIM field and recognizes that the data to the station is buffered (ON) in the access point, it transmits PS-Poll to the access point (F1103). When the access point operates without problems according to the IEEE802.11 specification, the communication apparatus receives Data after F1103, but cannot receive it in this sequence diagram. The communication apparatus receives the next Beacon without receiving data (Data) (F1104). When the communication device recognizes that it is OFF with reference to this new Beacon TIM field, the communication device transitions to the Doze state. Next, it is assumed that the access point transmits the data (Data) requested in F1103 to the communication device (F1105). However, since the communication device is in the Doze state at this timing, data cannot be received and packet loss occurs.

  The present invention has been made in view of the above problems, and an object thereof is to reduce the occurrence of packet loss.

In order to achieve the above object, a communication apparatus according to an aspect of the present invention has the following arrangement. That is,
Control information is received from the other communication device in a power saving mode in which the communication is switched between time-division between a start state in which data is received from another communication device and a nap state in which data is not received from the other communication device. Receiving means;
Requesting means for requesting data from the other communication device when the control information received by the receiving means indicates that there is data to be acquired from the other communication device;
When a predetermined time has passed without receiving the data corresponding to the request from the other communication device after the receiving means has received the control information indicating that there is data to be acquired, the power saving mode Transition means for shifting to another mode in which the startup state continues.

  According to the present invention, occurrence of packet loss can be reduced.

The block diagram of the communication apparatus by 1st embodiment. The communication sequence diagram by 1st embodiment. The flowchart explaining the electric power mode determination process by 1st embodiment. The flowchart explaining the electric power mode determination process by 1st embodiment. The flowchart explaining the electric power mode determination process by 1st embodiment. The block diagram of the communication apparatus by 2nd embodiment. The communication sequence diagram by 2nd embodiment. The block diagram of the communication apparatus by 3rd embodiment. The communication sequence diagram by 3rd embodiment. The communication sequence diagram by 3rd embodiment. The communication sequence diagram with a general communication apparatus and a malfunctioning access point. The flowchart which shows operation | movement of the power saving mode by embodiment.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the following, an example using a wireless LAN compliant with IEEE802.11 will be described. However, the communication form is not limited to this embodiment such as a wireless LAN or an infrastructure mode, and various communication methods can be used within the scope of the technical idea. It can be changed. In the following embodiments, the communication device can operate in two power modes, a normal mode and a power saving mode. In the normal mode, the wireless interface is always enabled (that is, activated state, hereinafter referred to as Active state) (power saving is disabled). Further, in the power saving mode, communication is performed by switching between an activation state in which data is received from another communication device and a nap state in which data is not received from the other communication device by time division. That is, in the power saving mode, the wireless interface is switched between valid and invalid (that is, a nap state, hereinafter referred to as Doze state) by intermittent processing in which transmission / reception is performed only under a specific condition (power saving is effective). In the Active state, data can be received because the wireless interface is valid. In the Doze state, data cannot be received because the wireless interface is invalid.

[First embodiment]
FIG. 1 is a block diagram illustrating an example of a configuration of a communication device 100 according to the first embodiment. The communication device 100 alternately repeats the activation state (Active state) and the nap state (Doze state), and switches the device to the activation state in synchronization with the transmission cycle of control information periodically transmitted from the partner device. It is possible to execute a power saving mode for performing communication. The input unit 110 receives various inputs from the user. The input unit 110 can also accept settings related to the wireless LAN. The control unit 120 controls various blocks. The control unit 120 can transmit / receive data to / from other devices via the communication unit 150 and the antenna 160, and can perform connection processing to the wireless LAN network. The power mode switching unit 121 switches the power mode of the communication unit 150 based on the communication parameters related to the power mode stored in the storage unit 140 and the determination result of the power mode determination unit 151. IEEE802.11 does not stipulate specifications for switching power modes in consideration of communication conditions such as packet loss. In the present embodiment, the connectivity is ensured and the packet loss is reduced by switching to another power mode that is not the power saving mode (in this embodiment, the normal mode in which the Active state continues) according to the communication status. The output unit 130 performs various outputs to the user by a display output such as an LCD or LED, or an audio output such as a speaker. The output unit 130 outputs, for example, settings related to the wireless LAN accepted by the input unit 110.

  The storage unit 140 stores various information such as a computer program executed by the control unit 120 and communication parameters. The communication unit 150 communicates with other devices. The communication unit 150 performs processing related to communication such as processing related to MAC (Media Access Control) with respect to control information and data received from the antenna 160. In the present embodiment, the control information is a Beacon transmitted by an access point or the like. In Beacon, there is a TIM field indicating whether data to the communication device is buffered in another device. The power mode determination unit 151 determines the power mode according to the communication status with other devices. The communication status can be judged from Beacon or data reception.

  FIG. 2 is a communication sequence diagram of the communication device 100 according to the first embodiment, and shows a communication sequence in the infrastructure mode in which another device (also called a partner device) as a communication partner serves as an access point. Note that FIG. 2 shows an operation from when the communication apparatus 100 joins the network formed by the access point and shifts to the power saving mode until it switches to another power mode according to the communication status. Note that the other power modes are modes in which the power saving mode is invalid so that the Active state continues (state without transition to the Doze state).

  In the communication device 100 operating in the power saving mode, the communication unit 150 periodically transitions to the Active state according to the Beacon reception timing, and receives the Beacon from the access point via the antenna 160 (F201). When the communication unit 150 refers to the TIM field of Beacon and recognizes that the data to the communication device is not buffered in the access point, the communication unit 150 transitions to the Doze state. Hereinafter, the fact that the TIM field indicates that there is no data to be transmitted to the communication apparatus 100 is expressed as “the TIM field is OFF”. When the next Beacon reception timing comes, the communication unit 150 transitions to the Active state again and receives Beacon from the access point (F202). Assume that the communication unit 150 refers to the TIM field and recognizes that data to the communication device is buffered at the access point. Hereinafter, the fact that the TIM field indicates that there is data to be transmitted to the communication apparatus 100 is expressed as “TIM field is ON”. When the TIM field is ON, the communication unit 150 transmits a data transmission request (PS-Poll) for the communication device to the access point (F203). If the access point operates without any problem according to the IEEE802.11 specification and there is data for the communication device, the communication unit 150 of the communication device receives the data after F203, but it cannot be received in this sequence diagram. .

  Since the Beacon is periodically transmitted, the communication unit 150 receives the next Beacon (F204). When Beacon is received, the communication unit 150 refers to the TIM field, recognizes that it is ON, and transmits PS-Poll to the access point (F205). However, as in F203, the communication unit 150 cannot receive data. The communication unit 150 further receives the next Beacon (F206). Here, the power mode determination unit 151 determines to change to the normal mode from the communication status so far (in this embodiment, data could not be received for two PS-Polls), and this The determination is notified to the power mode switching unit 121. The power mode switching unit 121 changes the parameter related to the power saving mode stored in the storage unit 140 to the normal mode and instructs the communication unit 150 to invalidate the power saving mode, and performs the subsequent processing. Operate in normal mode. Various processes can be considered for the process in which the power mode determination unit 151 determines the change from the power saving mode to the normal mode based on the communication status. Hereinafter, some of these processes will be described in detail.

<< Operation in power saving mode >>
When the power mode becomes the power saving mode, the communication unit 150 alternately repeats the Active state and the Doze state, and communicates by switching the device to the Active state in synchronization with the transmission cycle of Beacon periodically transmitted from the partner device. I do. FIG. 12 is a flowchart for explaining the operation in the power saving mode according to the present embodiment. When the communication device 100 shifts to the power saving mode by the power mode switching unit 121, the communication unit 150 first shifts the communication device 100 to the Doze state (S1201). Then, the communication unit 150 shifts the communication device 100 to the Active state at the transmission timing of Beacon periodically transmitted from the counterpart device (S1202, S1203). When receiving the Beacon signal in the Active state, the communication unit 150 checks the TIM field of the received Beacon signal and determines whether the partner apparatus has data to be transmitted to the communication apparatus 100 (S1204, S1205).

  If it is determined that there is received data, the communication unit 150 transmits a PS-Poll as a data request to the counterpart device and waits for data reception (S1205, S1206, S1207). When data is received from the counterpart device in response to the data request (PS-Poll), the communication unit 150 transmits an ACK signal to the counterpart device and shifts the communication device 100 to the Doze state (S1207, S1208, S1209). . If the Beacon reception timing comes again while waiting for data reception in S1207, the process returns to S1205, and the above-described process is repeated. When receiving a Beacon indicating that there is no data to be transmitted from the partner apparatus to the communication apparatus 100, the communication unit 150 shifts the communication apparatus 100 to the Doze state (NO in S1205, S1209). In the process of transitioning to the Doze state (S1201, S1209), if the next timing of receiving the Beacon from the counterpart device is shorter than the specific time, the process is continued without changing to the Doze state and in the Active state. Anyway.

  In the present embodiment, the communication unit 150 receives Beacon indicating that there is data to be acquired, and the specific time has passed without receiving data corresponding to the data request (PS-Poll) from the partner device. Based on this, the transition of the power mode is controlled. This control is executed by the power mode determination unit 151 and the power mode switching unit 121, and will be described in detail below with reference to the flowcharts of FIGS.

<< Disabling power saving mode when a specific time measured by the timer is exceeded >>
FIG. 3 is a flowchart showing an operation when determining the power mode of the communication apparatus 100 according to the first embodiment of the present invention. The process shown in the flowchart of FIG. 3 is performed every Beacon reception period after the communication apparatus 100 joins the network and shifts to the power saving mode.

  First, the power mode determination unit 151 confirms whether a specific time has elapsed for a timer (this timer is started in S304 described later) (S301). The sequence shown in FIG. 2 corresponds to the case where this specific time is two Beacon cycles. If the specific time has not elapsed (in the case of No in S301), the communication unit 150 waits for Beacon reception from the access point and receives Beacon (S302). Then, the communication unit 150 refers to the TIM field to check whether there is data to be received by the communication device (whether data to the communication device is buffered in the access point). (S302). As a result of referring to the TIM field, when it is determined that there is no data to be received (the TIM field is OFF) (No in S302), the communication unit 150 ends the processing illustrated in FIG. 3 and next Beacon reception timing Wait until.

  If it is determined that there is data to be received (TIM field is ON) (Yes in S302), the communication unit 150 confirms whether timing by the timer has already started in S304 (S303). When the time measurement by the timer has not started yet (No in S303), the communication unit 150 starts the timer (S304). In step S305, the communication unit 150 transmits a PS-Poll, requests data from the access point, and waits for data reception. If the data requested by PS-Poll cannot be received from the access point by the next Beacon reception timing (No in S305), the communication unit 150 ends the processing shown in FIG. Wait until. On the other hand, if the data can be received (Yes in S305), the communication unit 150 stops the timer started in S304, resets it (S306), ends this processing, and waits for the next Beacon reception timing. .

  On the other hand, when it is determined in S301 that the specific time has elapsed (Yes in S301), the power mode determination unit 151 determines that the specific time data is present even though there is data to the communication device at the access point. Is not received. Then, the power mode determination unit 151 determines the power mode as a power mode other than the power saving mode (in this embodiment, the normal mode) and notifies the power mode switching unit 121 of the power mode. The power mode switching unit 121 changes the parameter related to the power saving mode stored in the storage unit 140 to the normal mode and instructs the communication unit 150 to invalidate the power saving mode, and performs the subsequent processing. Operate in the normal mode (S307).

  Note that the timer start, stop, reset, and switching from the power saving mode may be performed at any timing as long as the processing of the present invention can be performed.

<< Disabling the power saving mode based on the count value of Beacon (Part 1) >>
FIG. 4 is a flowchart showing processing for determining the power mode of the communication apparatus 100 according to the first embodiment. Similar to the processing of FIG. 3, this flowchart is performed every Beacon reception period after the communication apparatus 100 joins the network and shifts to the power saving mode.

  First, the power mode determination unit 151 checks whether or not the number of reception impossible counts (described later in S405) is equal to or greater than the number specified by the control unit 120 (S401). The unreceivable count is obtained by counting that the Beacon indicating that data to the communication apparatus exists in the TIM field has been received but the data could not be received by the next Beacon. Therefore, FIG. 2 corresponds to a sequence diagram when the designated number of times is two. If the unreceivable count is less than the specified number (No in S401), the communication unit 150 waits for and receives the Beacon from the access point. Then, the communication unit 150 refers to the TIM field to check whether there is data to be received by the communication device (whether data to the communication device is buffered in the access point). (S402). If there is no data to be received (No in S402), the communication unit 150 ends this processing and waits until the next Beacon reception timing.

  If there is data to be received (Yes in S402), the communication unit 150 transmits a PS-Poll and waits for reception of data from the access point (S403). When the data can be received from the access point by the next Beacon timing (Yes in S403), the power mode determination unit 151 resets the unreceivable count that holds the number of times the data cannot be received. Then, the communication unit 150 ends this processing and waits until the next Beacon reception timing. On the other hand, when data could not be received in S403 (No in S403), the power mode determination unit 151 increments the unreceivable count by one (S405). Then, the communication unit 150 ends this processing and waits until the next Beacon reception timing. Note that the internal memory of the communication unit 150 or the storage unit 140 may be used as the unreceivable count.

  On the other hand, when it is determined in S401 that the unreceivable count is the specified number of times (Yes in S401), the power mode determination unit 151 specifies the specified number of times even though there is data to the communication device at the access point. It is determined that data could not be received. Then, the power mode determination unit 151 determines the power mode to be a mode for invalidating power saving other than the power saving mode (normal mode in the present embodiment), and notifies the power mode switching unit 121 of the mode. The power mode switching unit 121 changes the parameter related to the power saving mode stored in the storage unit 140 to the normal mode and instructs the communication unit 150 to invalidate the power saving mode, and performs the subsequent processing. Operate in the normal mode (S406).

<< Disabling the power saving mode based on the count value of Beacon (Part 2) >>
FIG. 5 is a flowchart showing an operation when determining the power mode of the communication apparatus 100 according to the first embodiment. The processing shown in this flowchart is performed every Beacon reception period after the communication apparatus 100 joins the network and shifts to the power saving mode, similarly to the processing in FIGS. 3 and 4.

  First, the communication unit 150 receives Beacon and refers to the TIM field to check whether or not the communication device can receive data (whether or not data to the communication device is buffered in the access point). (S501). When there is data to be received from the counterpart device (Yes in S501), the communication unit 150 transmits PS-Poll to the access point and waits for data reception from the access point until the next Beacon reception timing (S502). . When the data can be received (Yes in S502), the power mode determination unit 151 clears the data reception history (S504). On the other hand, if data could not be received by the next Beacon reception timing (in the case of No in S502), the fact that there was data to be received as the data reception history, but registered that the data could not be received (S503). . Note that the reception history may be stored in the internal memory of the communication unit 150 or may be stored in the storage unit 140. Here, the reception impossible count as described in FIG. 4 is used.

  If it is determined in S501 that there is no data to be received (No in S501), the process proceeds to S505. In step S <b> 505, the power mode determination unit 151 confirms that “the unreceivable count is equal to or greater than the number specified by the control unit 120” and “the TIM field of the received Beacon is OFF”. If YES is obtained in S505, it indicates that the data could not be received for the designated number of times and the Beacon TIM field has changed from ON to OFF. FIG. 2 corresponds to a sequence diagram when the specified number of times is 2 and the TIM field changes from ON to OFF in F206. If reception has not been performed for the specified number of times and the TIM field has not changed (No in S505), the communication unit 150 ends the process. The communication unit 150 receives a beacon indicating that there is data to be received for the specified number of times or more, but has not received the data (the unreceivable count is the specified number of times) and the TIM field has changed. (Yes in S505). In that case, the power mode determination unit 151 determines that the data addressed to the communication device of the access point has been aged, determines the power mode as the normal mode, and notifies the power mode switching unit 121 (S506). The power mode switching unit 121 changes the parameter related to the power saving mode stored in the storage unit 140 to the normal mode and instructs the communication unit 150 to invalidate the power saving mode, and performs the subsequent processing. Operate in normal mode.

  In the process of FIG. 5, the process ends as it is in the case of NO in S505. Therefore, receive a Beacon whose TIM field is ON with the unreceivable count being 0, and receive a Beacon whose TIM field is OFF (Beacon whose first TIM field is OFF) without receiving data. If this happens, the transition to the Doze state is performed as it is. After that, it is assumed that a Beacon whose TIM field is ON is received again, and that a Beacon whose TIM field is OFF (a Beacon whose second TIM field is OFF) is received without receiving data. When receiving a Beacon whose first TIM field is OFF, the reception impossible count is 1, and when receiving a Beacon whose second TIM field is OFF, the reception impossible count is 2. If the specified number of times is set to 2, the power mode is switched. In the case of NO in S505, the processing content may be changed within the scope of performing the processing of the present invention, such as clearing the data reception history. If the data reception history is cleared in the case of NO in S505, a situation where a beacon with the TIM field ON is received but no data can be received continuously occurs after a specified number of times, and then the TIM field is OFF Only when the Beacon is received, the power mode is switched.

  As described above, according to the first embodiment, the power mode is switched from the power saving mode to the normal mode according to the data reception state when the Beacon with the TIM field being ON is received. Therefore, even when the access point as the counterpart device does not operate according to the standard, it is possible to reduce data loss. In the above embodiment, in order to prevent data loss in the situation shown in FIG. 11, the specific time may be set to one Beacon cycle, or the specified number of times may be set to one.

[Second Embodiment]
FIG. 6 is a block diagram showing an example of the configuration of the communication apparatus 600 according to the second embodiment. A power mode control unit 622 is added to the control unit 120 with respect to the communication apparatus 100 illustrated in FIG. 6, parts having the same configuration as in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The power mode control unit 622
When the power mode switching unit 121 switches the power mode of the communication unit 150, device identification information including the switched power mode and information for identifying a network provided by another device is stored in the storage unit 140. And
When the communication device 600 leaves the network according to an instruction from the control unit 120 and rejoins the network, the device identification information in the storage unit 140 is referred to, and if there is a previously set power mode, the power mode is switched. The communication unit 150 is set via the unit 121.

  FIG. 7 is a sequence diagram for explaining the operation of the communication apparatus 600 according to the second embodiment. FIG. 7 shows an operation in the infrastructure mode in which another device as a communication partner is an access point. Before the communication device 600 joins the network, once it joins the network, leaves the network, joins the same network again, and then reflects the power mode when it last joined the network. Operation is shown.

  When the input unit 110 receives an operation for allowing the communication device 600 to join the network from the user, the control unit 120 issues an instruction to the communication unit 150, so that the communication device 600 joins the network provided by the access point (F701). After receiving the instruction to operate in the power saving mode from the input unit 110 after joining the network, the power mode switching unit 121 of the communication device 600 sends an instruction for enabling the power saving mode to the communication unit 150. Do. Thus, thereafter, the communication apparatus 600 is operated in the power saving mode (F702). Thereafter, the communication device 600 communicates with the access point. As described in the first embodiment, the power mode determination unit 151 determines whether or not to change to the normal mode in view of the communication status. When the power mode determination unit 151 determines to set the normal mode, the power mode determination unit 151 notifies the power mode switching unit 121 of this. The power mode switching unit 121 changes the parameter related to the power saving mode stored in the storage unit 140 to the normal mode and instructs the communication unit 150 to invalidate the power saving mode, and performs the subsequent processing. Operate in the normal mode (F703). The power mode control unit 622 stores the device identification information in the storage unit 140 when the power mode is determined to be the normal mode according to the communication status (F704). This device identification information is composed of information indicating the normal mode and SSID (Service Set Identifier) which is information for identifying a network provided by another device (a network in which the device is currently participating). Is done. The information for identifying the network provided by the other device in the device identification information may be the MAC address of the other device instead of the SSID.

  When the input unit 110 receives an operation from the user to leave the communication device 600 from the currently participating network, the control unit 120 instructs the communication unit 150 to send the communication device 600 from the network provided by the access point. Leave (F705). Thereafter, when the input unit 110 receives an operation from the user to join the communication device 600 to the same network as the previous time, the control unit 120 instructs the communication unit 150 to send the communication device 600 to the network provided by the access point. Let them participate (F706). The power mode control unit 622 refers to the device identification information stored in the storage unit 140 to confirm whether there is a power mode set before leaving for the participating network. Here, the device identification information stored in F704 is found, and the power mode control unit 622 changes the power mode of the communication unit 150 to the normal mode via the power mode switching unit 121 (F707).

  As described above, according to the second embodiment, when rejoining the network that was previously joined, the previous mode (power saving mode or normal mode) is automatically set and the mode is changed. Accordingly, when participating in a network formed by an access point that does not operate according to the standard, the operation in the power saving mode is immediately prohibited from the second time onward, and data can be more effectively prevented from being lost.

[Third embodiment]
FIG. 8 is a block diagram showing an example of the configuration of the communication apparatus 800 according to the third embodiment. The power mode switching unit 121 and the power mode determination unit 151 are eliminated from the communication device 100 illustrated in FIG. 1, and a power state switching unit 851 and a power state determination unit 852 are added to the communication unit 150. 8, portions having the same configuration as in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The power state switching unit 851 switches the power state of the communication unit 150 based on the power state transition defined by IEEE802.11 and the determination result of the power state determination unit 852. The power state switching unit 851 normally follows the power state transition defined by IEEE802.11. However, when there is an instruction from the power state determination unit 852, the determination result of the power state determination unit 852 is given priority. The power state determination unit 852 determines the power state according to the communication status with other devices. The communication status is judged from Beacon and data reception. In the first embodiment, the Active state is maintained by switching from the power saving mode to the normal mode. On the other hand, in the third embodiment, after receiving Beacon a specified number of times under specific conditions, the active state is maintained until the transition to the Doze state after the elapse of a specific time, thereby ensuring communication connectivity. To do.

  FIG. 9 is a sequence diagram showing an operation of the communication apparatus 800 according to the third embodiment. FIG. 9 shows the case of the infrastructure mode in which another device as a communication partner is an access point. The communication device 800 joins the network configured by the access point, shifts to the power saving mode, and repeats the Active state and the Doze state. FIG. 9 shows an operation from the transition to the Active state to the transition to the Doze state after a specific time elapses after the Beacon is received a specified number of times, after matching the specific condition. The specific condition in FIG. 9 is a condition in which a beacon whose TIM field is ON is received but data cannot be received.

  In the communication apparatus 800 operating in the power saving mode, the power state switching unit 851 switches the communication unit 150 to the Active state at the Beacon reception timing in accordance with the power state transition defined by IEEE802.11. In this state, the communication unit 150 receives Beacon from the access point via the antenna 160 (F901). When the communication unit 150 recognizes that the Beacon TIM field is OFF, the power state switching unit 851 transitions the communication unit 150 to the Doze state in accordance with the power state transition defined by IEEE802.11. At the next Beacon reception timing, the power state switching unit 851 switches the communication unit 150 to the Active state in accordance with the power state transition defined by IEEE802.11. And the communication part 150 receives Beacon from an access point via the antenna 160 (F902). When recognizing that the TIM field of Beacon is ON, the communication unit 150 transmits PS-Poll to the access point (F903). However, as in F203 (FIG. 2), the communication unit 150 cannot receive data. The communication unit 150 further receives the next Beacon (F904). Here, when the control unit 120 specifies the Beacon reception designation count to 1 to the communication unit 150, the communication unit 150 starts a timer for a specific time. The communication unit 150 refers to the Beacon TIM field and recognizes that it is OFF. When the TIM field of Beacon is OFF, after that, when the timer for a specific time is completed, the power state determination unit 852 determines to shift to the Doze state and notifies the power state switching unit 851. The power state switching unit 851 switches the communication unit 150 to the Doze state.

  The above process can be realized by setting S406 shown in FIG. 4 as a process of “transitioning to the Doze state after a predetermined time has elapsed” and the power state determination unit 852 executing the process. 3 described in the first embodiment (S307 is “determined to shift to the Doze state after a predetermined time has elapsed (delayed by a predetermined time)”) and FIG. 5 (S506 is “after a predetermined time has elapsed (predetermined time) The process of “transition to Doze state”) may be applied. In the above description, data cannot be received after PS-Poll transmission. However, when data can be received, the state may be changed to the Doze state according to the IEEE802.11 specification.

  FIG. 10 is a sequence diagram illustrating an operation performed by the communication apparatus 800 according to the third embodiment. FIG. 10 shows a case of an infrastructure mode in which another device as a communication partner is an access point. In FIG. 10, after the communication device 800 joins the network configured by the access point and shifts to the power saving mode, the communication device 800 matches the specific condition, receives the Beacon for the specified number of times, and then enters the Doze state after the specific time has elapsed. The operation until the transition is shown. Note that the specific condition in FIG. 10 is a condition that after receiving data from another device by PS-Poll, a Beacon that cannot receive data (a Beacon whose TIM field is OFF) is received.

  In the communication apparatus 800 operating in the power saving mode, the power state switching unit 851 switches the communication unit 150 to the Active state at the Beacon reception timing in accordance with the power state transition defined by IEEE802.11. The communication unit 150 receives Beacon from the access point via the antenna 160 (F1001). When the communication unit 150 refers to the Beacon TIM field and recognizes that it is OFF, the power state switching unit 851 transitions the communication unit 150 to the Doze state in accordance with the power state transition defined in IEEE802.11. . Next, the power state switching unit 851 switches the communication unit 150 to the Active state at the next Beacon reception timing in accordance with the power state transition defined by IEEE802.11. The communication unit 150 receives Beacon from the access point via the antenna 160 (F1002). When the communication unit 150 refers to the TIM field of Beacon and recognizes that it is ON, the communication unit 150 transmits PS-Poll to the access point (F1003). The communication unit 150 receives data from the access point via the antenna 160 (F1004). The communication unit 150 maintains the Active state, and receives the next Beacon from the access point via the antenna 160 (F1005). Here, when the control unit 120 specifies the Beacon reception designation count to 1 to the communication unit 150, the communication unit 150 starts a timer for a specific time. Thereafter, when the timer for the specific time is completed, the power state determination unit 852 determines to shift to the Doze state, and notifies the power state switching unit 851. The power state switching unit 851 switches the communication unit 150 to the Doze state.

  In this case, after transmitting the PS-Poll, the Active state is always maintained until data is received. The effects produced by such control are as follows. When data is received from another device (AP) by PS-Poll, if the other device has data (continuous data) addressed to itself, the more data bit in the control control field of the data frame (F1004) is set to 1. It is specified by IEEE802.11 to set the more data bit to 0 when there is no data. Here, the IEEE802.11 specification stipulates that the transition to the Doze state may be made if the more data bit becomes 0 or the Beacon TIM is turned OFF. However, some access points in the market do not correctly set the more data bits and send data after a certain period of time. Therefore, in the communication apparatus of this embodiment, in order to minimize data loss even when communicating with such an access point, the value of the more data bit is not trusted (not referred to), and the communication unit 150 is in the active state. To keep data from being lost until the next Beacon. Further, the IEEE802.11 specification stipulates that if the TIM is OFF, a transition to the Doze state can be made without elapse of a specific time. On the other hand, in the communication apparatus of this embodiment, even if the next Beacon TIM is OFF, data loss is further prevented by intentionally continuing the Active state for a specific time.

  As described above, according to the first embodiment, in the communication device having the power saving function, the power mode is automatically switched according to the communication status with other devices. Furthermore, according to the second embodiment, the result of the automatic switching is retained, and communication is performed in the switched power mode at the next network participation. Further, according to the third embodiment, in a communication device that operates in the power saving mode, the validity / invalidity of the wireless interface is switched according to the communication status with other devices. According to each of the embodiments as described above, packet loss can be achieved even at an access point compliant with only IEEE802.11 in consideration of data loss except when a new station joins a network configured in the power saving mode. It is possible to realize the transition of the power saving state in consideration of the above. Furthermore, since the connectivity can be ensured even when the communication partner of the communication device is a defective access point, the chance of encountering a problem such as a user being unable to communicate can be reduced.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (10)

A communication device,
Control information is received from the other communication device in a power saving mode in which the communication is switched between time-division between a start state in which data is received from another communication device and a nap state in which data is not received from the other communication device. Receiving means;
Requesting means for requesting data from the other communication device when the control information received by the receiving means indicates that there is data to be acquired from the other communication device;
When a predetermined time has passed without receiving the data corresponding to the request from the other communication device after the receiving means has received the control information indicating that there is data to be acquired, the power saving mode A transition means for transitioning from one mode to another mode in which the startup state continues,
A communication apparatus comprising: Timer means started when the receiving means receives the control information indicating that there is data to be acquired;
The communication apparatus according to claim 1, wherein the transition unit determines that the predetermined time has elapsed based on the time measured by the timer unit. After receiving the control information indicating that there is data to be acquired by the receiving unit, the receiving unit further includes a counting unit that counts the number of times the control information is received,
The communication apparatus according to claim 1, wherein the transition unit determines that the predetermined time has elapsed when the counting unit counts the designated number of times.   The shift means receives the control information indicating that there is no data to be acquired after the predetermined time has passed without receiving data corresponding to the request from the other communication device. 4. The communication apparatus according to claim 1, wherein the communication apparatus shifts from the power saving mode to the other mode.   Control means for causing the communication device to operate in the other mode when the transfer device leaves the network formed by the other communication device after being transferred to the other mode and rejoins the network. The communication apparatus according to any one of claims 1 to 4, further comprising: And further comprising storage means for storing identification information for identifying the currently participating network and that the mode has been shifted from the power saving mode to the other mode,
The control means, when leaving the network and joining the network, if the identification information of the joined network matches the identification information stored in the storage means, The communication apparatus according to claim 5, wherein the communication apparatus is operated in a mode. A communication device that operates in a power saving mode in which communication is performed by alternately switching between an activated state and a nap state and switching the device to the activated state in synchronization with a transmission period of control information periodically transmitted from the partner device. There,
Receiving means for receiving control information from the counterpart device;
A transmission means for transmitting a data request to the counterpart apparatus when the control information received by the reception means indicates that there is data to be acquired from the counterpart apparatus;
The nap from the activated state based on the reception of control information indicating that data has been received from the counterpart device in response to the data request or that there is no data to be acquired from the counterpart device. Power state switching means for switching to a state,
The power state switching means, when the receiving means receives control information indicating that there is data to be acquired, and when a specific time has passed without receiving data corresponding to the data request from the counterpart device Is a communication apparatus characterized in that after the specific time has elapsed, the receiving means delays by a predetermined time after receiving the control information to put the communication apparatus in a nap state. A communication device that operates in a power saving mode in which communication is performed by alternately switching between an activated state and a nap state and switching the device to the activated state in synchronization with a transmission period of control information periodically transmitted from the partner device. There,
Receiving means for receiving control information from the counterpart device;
A transmission means for transmitting a data request to the counterpart apparatus when the control information received by the reception means indicates that there is data to be acquired from the counterpart apparatus;
The nap from the activated state based on the reception of control information indicating that data has been received from the counterpart device in response to the data request or that there is no data to be acquired from the counterpart device. Power state switching means for switching to a state,
The power state switching means obtains from the counterpart apparatus after receiving data corresponding to the data request from the counterpart apparatus after the reception means has received control information indicating that there is data to be acquired. A communication apparatus characterized by putting the communication apparatus into a nap state by delaying a predetermined time after receiving the control information indicating that no data should be present. One of the power modes is a power saving mode in which communication is performed by alternately switching between an activated state and a nap state and switching the device to the activated state in synchronization with a transmission period of control information periodically transmitted from the partner device. A communication device control method executable as
A receiving step for receiving control information from the counterpart device in the power saving mode;
A transmitting step for transmitting a data request to the counterpart device when the control information received in the reception step indicates that there is data to be acquired from the counterpart device; and
Based on the fact that the mode control means has received the control information indicating that there is data to be acquired in the reception step and has not received the data corresponding to the data request from the counterpart device after a specific time has passed. And a mode control step of shifting the power mode from the power saving mode to another mode in which the activation state continues.   A program that causes a computer to function as each unit of the communication device according to any one of claims 1 to 8.

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