Communication device, communication method, and program

Abstract

To surely receive a frame transmitted from the other communication apparatus.SOLUTION: A communication apparatus, which can operate in parallel a function that performs a communication by joining a first communication network and a function that performs a communication by joining a second communication network, controls whether or not to transfer from a first state to a second state on the basis of the time from the reception of a first frame to the reception of a second frame, when the second frame is received from a second other communication apparatus after a first frame is received from a first other communication apparatus in the first state, in the case of operating so as to transfer between the first state and the second state where a power consumption is smaller than that of the first state.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a communication device that performs wireless communication. [Background technology]

[0002] Conventionally, wireless communication devices that support the IEEE 802.11 standard and the Wi-Fi standard have been proposed that operate as a station (hereinafter referred to as STA) and an access point (hereinafter referred to as AP) in parallel. Here, IEEE stands for Institute of Electrical and Electronics Engineers. The communication device can establish a connection with an AP using the STA function and communicate with the STA, while also establishing a connection with the STA using the AP function and communicating with the STA.

[0003] Similarly, a communication device has been proposed that has multiple STA functions and is capable of operating a first STA function and a second STA function in parallel. For example, the communication device can establish a connection with an AP using the first STA function to perform communication, and in parallel, establish a connection with a Group Owner (GO) using the second STA function as a client function of the Wi-Fi Direct standard to perform communication.

[0004] The IEEE802.11 standard also includes a power saving function to reduce battery consumption of STAs. Patent Documents 1 and 2 propose techniques for controlling the power saving mode to enable communication with reduced power consumption. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-19607 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-206762 Summary of the Invention [Problem to be solved by the invention]

[0006] A communication device having the above-described multiple STA functionality can operate by transitioning between a first state and a second state that consumes less power than the first state in accordance with the IEEE 802.11 standard. However, in the case of a communication device having multiple STA functionality, for example, including a first STA and a second STA, the following problem occurs. That is, after receiving a frame from a first AP to which the first STA is connected and transitioning to the second state, a frame from the second AP to which the second STA is connected may arrive while the device is transitioning to the first state to receive a frame from the second AP. In the above-described situation, a communication device having multiple STA functionality, including a first STA and a second STA, may not be able to receive frames from the second AP, resulting in packet loss.

[0007] In view of the above-mentioned problems, an object of the present invention is to more reliably receive frames transmitted from other communication devices. [Means for solving the problem]

[0008] In order to achieve the above object, a communication device of the present invention is a communication device that can operate in parallel a function of participating in a first communication network and performing communication and a function of participating in a second communication network and performing communication, and includes a first Access Point (AP) periodically sent from No. a second frame for constructing the second communication network; AP a receiving means for receiving a second frame periodically transmitted from the first state when the communication device operates while transitioning between a first state and a second state having lower power consumption than the first state, and AP send vinegar After receiving the first frame transmitted by the first AP, AP transmits Receive the second frame Ma Time at is less than a given valueto 、 The first frame is received and the second frame is received. Transition to the second state Do not and a control means for controlling the [Effects of the Invention]

[0009] According to the present invention, it is possible to more reliably receive frames transmitted from other communication devices. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a network configuration according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a hardware configuration of a communication device 103. [Figure 3] 10 is a flowchart relating to processing of the communication device 103 of the first embodiment. [Figure 4] 10 is a flowchart relating to processing of a communication device 103 according to the second embodiment. [Figure 5] FIG. 10 is a diagram showing the state transition of STA 103 when APs 101 and 102 transmit Beacon frames. [Figure 6] 10 is a diagram showing an example of information that the STA 103 of the second embodiment notifies the user. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the embodiments described below are merely examples, and various devices, systems, methods, programs, media, and the like configured to realize the described functions are included in the scope of the present invention.

[0012] Fig. 1 shows the network configuration of a communication system according to this embodiment. In Fig. 1, communication devices 101 and 102 are APs (Access Points) that serve to establish a communication network, and communication device 103 is a STA (Station) that participates in the communication network established by the AP and performs communication. STA 103 is a personal computer (hereinafter referred to as PC). STA 103 is capable of operating two STA functions and can establish connections with two APs to perform communication.

[0013] In addition, STA103 can establish a connection with an AP using the first STA function to perform communication, and in parallel can establish a connection with a GO (Group Owner) using the client function of the Wi-Fi Direct standard using the second STA function to perform communication.

[0014] The communication devices 101 to 103 are also capable of executing a power saving function that complies with the IEEE802.11 standard series. The STA 103 operating in power saving mode regularly transitions between an Awake state and a Doze state, which operates with lower power consumption than the Awake state. Here, the Awake state is a state in which power is supplied to the circuit and frames can be sent and received, while the Doze state is a state in which frames cannot be sent or received.

[0015] 2 shows the hardware configuration of the STA 103. The STA 103 is made up of a wireless transceiver 201, a beacon checker 202, a beacon predictor 203, a change calculator 204, a PS controller 205, a notifier 206, an input unit 207, a memory 208, and a controller 209.

[0016] The wireless transmission / reception unit 201 transmits and receives wireless signals such as Beacon frames, etc. When the STA 103 operates in a power save mode, the unit 201 turns on and off the power supply to the receiving circuit.

[0017] The Beacon confirmation unit 202 confirms the contents of the Beacon signal received by the wireless transceiver unit 201. A Beacon frame is a frame that periodically broadcasts network information. The Beacon frame includes information for communicating on the frequency channel that transmits the Beacon frame, such as the transmission interval of the Beacon frame and information on operable frequency channels, and information for time synchronization between the AP and the STA that establishes a connection.

[0018] In this embodiment, information regarding the DTIM (Delivery Traffic Indication Message) interval included in the Beacon is checked.

[0019] The Beacon prediction unit 203 predicts the timing of receiving a Beacon based on the confirmation by the Beacon confirmation unit 202. For Beacon signals received from the same AP, prediction is performed each time a Beacon is received, but prediction may be performed only the first time. Alternatively, prediction may be performed only if the confirmation result of the Beacon confirmation unit 202 indicates a change in a parameter related to power saving.

[0020] The change calculation unit 204 calculates the ON / OFF patterns of the receiving circuit, which differ depending on the APs to which connections have been established and the number of connections.

[0021] If the STA 103 operates in the power save mode based on information from each block, the PS control unit 205 sends an instruction to the wireless transceiver unit 201 to transition to the power save mode.

[0022] The notification unit 206 notifies the user. Here, the notification is made using characters or images on a liquid crystal panel, but it may also be made using LEDs with different light colors or patterns, or a buzzer with sound. It may also be made by displaying the information on a monitor screen, outputting audio or vibrations from a speaker, or the like.

[0023] The input unit 207 receives various operations from the user. The notification unit 206 outputs various types of information to the user via a monitor screen or a speaker. In this embodiment, the input unit 207 also functions as an interface used by the power save control unit 205 to make inquiries to the user. Here, since the STA 103 is a PC, the input unit 207 is a mouse, but it is sufficient if the user can input information. Note that both the input unit 207 and the notification unit 206 may be implemented in a single module, such as a touch panel. Furthermore, the input unit 207 and the notification unit 206 may be integrated with the STA 103 or may be separate units.

[0024] The storage unit 208 is configured with memories such as ROM and RAM, and stores programs for performing various processes described below and various types of information. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. In addition to memories such as ROM and RAM, storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs may also be used as the storage unit 208. Furthermore, the storage unit may include multiple memories.

[0025] The control unit 209 is configured with, for example, a processor such as a CPU or MPU, an ASIC, a DSP, an FPGA, etc. CPU stands for Central Processing Unit, MPU stands for Micro Processing Unit, and ASIC stands for Application Specific Integrated Circuit. DSP stands for Digital Signal Processor, and FPGA stands for Field Programmable Gate Array.

[0026] The control unit 209 controls the AP and the STA as a whole by executing the program stored in the storage unit 208. Note that the control unit 209 may control the AP and the STA as a whole in cooperation with the program stored in the storage unit 208 and an OS (Operating System).

[0027] <Embodiment 1> 3 is a flowchart showing the flow of processing performed by the control unit 209 executing a program stored in the storage unit 208 of the communication device 103. This flowchart shows the flow of state transition processing of the STA 103 when receiving Beacon frames from multiple APs.

[0028] This flowchart starts when the communication device 103 is powered on, or when the wireless LAN function of the communication device 103 is turned on, or when the user operates the input unit 207 to select the SSID of the AP to connect to. In this embodiment, the SSIDs (Service Set IDs) of two APs are input.

[0029] In S301, it is confirmed whether or not the power saving (hereinafter referred to as PS) function of the STA 103 is enabled. If it is determined in S301 that the PS function is disabled, the connection sequence is started (S308) without performing PS control, and this flowchart ends.

[0030] If the STA 103 determines in S301 that the PS function is enabled, it determines whether or not it has received the Beacon signals transmitted by the two APs input by the user (S302). If the Beacon signals cannot be received even after waiting for a certain period of time in S302, it may be configured to cancel the process and start over from the user input.

[0031] If it is determined in S302 that a Beacon signal transmitted by the AP selected by the user has been received, a prediction calculation of the Beacon transmission timing is performed (S303). As a method of predicting and calculating the Beacon transmission timing, first, the Beacon confirmation unit 202 acquires the SSID, MAC address, timestamp when the Beacon signal is received, Beacon period, and DTIM interval, and stores them in the storage unit 208. Then, the Beacon prediction unit 203 performs calculations by acquiring the parameters stored in the storage unit 208.

[0032] In S303, when the prediction of the transmission timing of the Beacon signal is completed, the state transition for receiving the Beacon frame from AP 101 and the state transition for receiving the Beacon frame from AP 102 are combined. According to the combined result, the PS control unit 205 sets the Beacon reception timing of the communication device 103 (S304) and instructs the wireless transceiver unit 201.

[0033] Figures 5(A) to (D) show the timing of receiving Beacon frames from AP 101 and AP 102 and the state transitions of STA 103. As shown in Figure 5, STA 103 regularly transitions between a "receiving possible" state and a "receiving impossible" state. Here, the "receiving possible" state is the Awake state, and STA 103 transitions to the Awake state in order to receive Beacon frames transmitted from AP 101 or AP 102. The "receiving impossible" state refers to the Doze state, which operates in a state with lower power consumption than the Awake state. When the PS function of STA 103 is enabled, STA 103 operates by regularly transitioning between the Awake state and the Doze state.

[0034] Figure 5(A) shows an example in which the Beacon transmission timings of AP 101 and AP 102 are relatively close. Figure 5(A) shows an example in which a Beacon frame can be received from AP 102 when STA 103 is in an Awake state to receive a Beacon frame from AP 101. In Figure 5(A), since a Beacon frame from AP 102 can be received when STA 103 is in an Awake state to receive a frame from AP 101, there is no need to correct the state transition of STA 103.

[0035] In S305, the state transition of STA 103 for receiving a Beacon frame from AP 101 and the state transition of STA 103 for receiving a Beacon frame from AP 102 are referenced. Specifically, in the state transition of STA 103 for AP 101 and the state transition of STA 103 for AP 102, it is determined whether a transition from the Awake state to the Doze state or a transition from the Doze state to the Awake state occurs within a certain time. The determination in S305 is made by the PS control unit 205. Specifically, the time from receiving a Beacon frame from AP 101 in the Awake state to receiving a Beacon frame from AP 102 is measured, and it is determined whether the time is greater than a predetermined value. Here, in FIG. 5A, no transition occurs within the certain time, so in S308, AP 101 and STA 103 establish a connection, and then AP 102 and STA 103 establish a connection, and this flowchart ends.

[0036] 5B shows an example in which the Beacon transmission timings of AP 101 and AP 102 are far apart. In S305, the PS control unit 205 determines that a transition has occurred within a certain time period in the portion indicated by a circle in the figure. That is, in S306, the state transition of STA 103 is corrected as shown in FIG. 5C. In other words, if the time between receiving a Beacon frame from AP 101 and receiving a Beacon frame from AP 102 is equal to or less than a predetermined value, a correction is made to prevent frequent state transitions between the Awake state and the Doze state. In this embodiment, the state of STA 103 is controlled so that it remains in the Awake state even when it is actually time to transition to the Doze state.

[0037] If a connection is established with each of AP 101 and AP 102 after correction as shown in Figure 5(C), the STA 103 will spend a lot of time in the Awake state, which will reduce PS efficiency. Therefore, in S307, the user is notified that PS efficiency will be reduced. After the user is notified in S307, AP 101 and STA 103 establish a connection, and then AP 102 and STA 103 establish a connection (S308). The notification is made before the connection is established with AP 101, but it may also be made before the connection is established with the second AP or after the wireless connection with the second AP is established.

[0038] In this embodiment, the second AP has been described with a DTIM interval of 1, but Fig. 5(D) shows the timing when AP 102 has a DTIM interval of 2. Also, instead of correcting the reception timing every time a Beacon frame is received, correction may be made only at the relevant location.

[0039] According to this embodiment, when a STA having multiple STA functions operates in PS mode and establishes connections with multiple APs, it is possible to prevent a situation in which Beacon frames cannot be received by preventing the STA from transitioning to the Doze state depending on the situation. Also, it is possible to improve usability by notifying the user that PS efficiency will decrease if the STA remains in the Awake state.

[0040] <Embodiment 2> In the first embodiment, an example is shown in which a user is notified that power saving efficiency will decrease if the Awake state is continued depending on the situation. In the present embodiment, an example is shown in which a notification is made to inquire whether or not to establish connections with multiple APs even if the power saving efficiency decreases when the Awake state is continued when the user is notified that power saving efficiency will decrease if the Awake state is continued.

[0041] 4 is a flowchart showing the flow of processing performed by control unit 209 executing a program stored in storage unit 208 of communication device 103. This flowchart shows the flow of state transition processing when communication device 103 receives Beacon frames from multiple APs.

[0042] S401 to S405 are the same as S301 to S305 in FIG. 3 and will not be described further.

[0043] In S406, the user is queried as to whether to establish a connection with two APs as input by the user, or to establish a connection with only one of the APs. The query in S406 is, for example, a query as to whether to prioritize power saving, since establishing a connection with two APs reduces power saving efficiency. Here, in S406, the connection itself may be canceled.

[0044] If the user selects either AP 101 or AP 102 in S406, that is, if the user prioritizes the power saving mode, then in S407 a wireless connection is established only with AP 102. Here, the user may be queried only about the number of APs to establish a connection with, and a connection may be established with the AP with the strongest radio wave.

[0045] If the user desires to connect to two APs in S406, i.e., if the power saving mode is not prioritized, an inquiry is made as to whether to keep PS control enabled or to switch to disabled PS control (S408). If the user selects to keep PS control enabled in S408, the state transition of STA 103 is corrected in S409 to receive Beacon frames from the two APs, and then the connection to the two APs is established, and this flowchart ends.

[0046] If the user selects to disable the PS control in S408, the PS control is disabled and wireless connections are established with the two APs (S410).

[0047] In addition, in S406 or S408, the notification unit 206 may notify the Beacon reception timing as shown in Fig. 6. Fig. 6 shows an example of the state of PS when connected to AP 101 and when connections are established with both APs, AP 101 and AP 102, and the change calculation unit 204 calculates the state of PS and difference information.

[0048] In addition, in S408, the PS control may be executed depending on whether the STA 103 is battery-powered or powered, without making an inquiry about the PS control. In this case, the PS control is enabled when the STA 103 is battery-powered, and disabled when the STA 103 is powered by the power supply. In addition, although the present embodiment illustrates a case where two APs are connected, the present invention is not limited to this, and a configuration with two or more APs is also possible.

[0049] According to this embodiment, when a STA having multiple STA functions operates in PS mode and establishes connections with multiple APs, it is possible to prevent failure to receive Beacon frames by preventing the STA from transitioning to the Doze state depending on the situation. In addition, the user is notified that the PS efficiency will decrease if the STA continues to remain in the Awake state. Furthermore, if the user does not want to decrease the PS efficiency, for example, the user can choose not to establish connections with multiple APs, thereby improving usability.

[0050] The STA 103 described in this embodiment may be a printer having a printing means. When operating as a printer, it is possible to print data acquired by communicating with a partner device, for example.

[0051] Furthermore, the STA 103 described in this embodiment may be a camera having an image capturing means. When operating as a camera, it is possible to transmit captured image data by communicating with a partner device, for example.

[0052] It is also possible to provide a system or device with a recording medium storing software program code for implementing the above-described functions, and have the computer (CPU, MPU) of the system or device read and execute the program code stored in the recording medium. In this case, the program code itself read from the recording medium will implement the functions of the above-described embodiments, and the recording medium storing the program code will constitute the above-described device.

[0053] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

[0054] In addition, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0055] Furthermore, the program code read from the storage medium may be written to a memory provided on a function expansion board inserted into a computer or a function expansion unit connected to the computer, and a CPU provided on the function expansion board or function expansion unit may then perform some or all of the actual processing based on the instructions of the program code to realize the above-mentioned functions.

[0056] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0057] 201 Radio transmitter / receiver 202 Beacon Verification Department 203 Beacon Prediction Department 204 Change calculation unit 205 PS control unit 206 Notification Department 207 Input section 208 Storage section 209 Control Unit

Claims

1. A communication device capable of concurrently operating a function of participating in a first communication network and performing communication and a function of participating in a second communication network and performing communication, a receiving means for receiving a first frame periodically transmitted from a first access point (AP) that constitutes the first communication network and a second frame periodically transmitted from a second AP that constitutes the second communication network; a control means for controlling the communication device not to transition to the second state during the period from receiving the first frame to receiving the second frame when the communication device operates while transitioning between a first state and a second state having lower power consumption than the first state and, after receiving the first frame transmitted by the first AP in the first state, if a time period from receiving the first frame transmitted by the first AP to receiving the second frame transmitted by the second AP is shorter than a predetermined value; A communication device comprising:

2. 2. The communication device according to claim 1, further comprising a notification unit that notifies a user that power saving efficiency will decrease if the first state is continued by the control unit.

3. 3. The communication device according to claim 2, wherein the notification means notifies the second AP when a connection is established with the second AP.

4. 4. The communication device according to claim 2, wherein the notification unit notifies information about a power saving state when a connection is established between the first AP and the second AP.

5. the communication device further comprises a receiving means for receiving an input from a user; The communication device according to any one of claims 2 to 4, characterized in that the notification means allows the user to select, via the reception means, whether to establish a connection with both the first AP and the second AP, or to establish a connection with either the first AP or the second AP.

6. 6. The communication device according to claim 1, wherein the first frame and the second frame are beacon frames conforming to the IEEE 802.11 standard.

7. 7. The communication device according to claim 1, wherein the interval between the first frames and the interval between the second frames is a DTIM (Delivery Traffic Indication Message) interval conforming to the IEEE 802.11 standard.

8. 8. The communication device according to claim 1, wherein the communication device operates in a power save mode conforming to the IEEE 802.11 standard.

9. 9. The communication device according to claim 1, wherein the first AP and the second AP operate as APs conforming to the IEEE 802.11 standard series.

10. A communication method for a communication device capable of concurrently operating a function of participating in a first communication network and performing communication and a function of participating in a second communication network and performing communication, comprising: a receiving step of receiving a first frame periodically transmitted from a first access point (AP) constituting the first communication network and a second frame periodically transmitted from a second AP constituting the second communication network; a control step of controlling the communication device not to transition to the second state during the period from receiving the first frame to receiving the second frame when the communication device operates while transitioning between a first state and a second state having lower power consumption than the first state and, after receiving the first frame from the first AP in the first state, the communication device does not transition to the second state during the period from receiving the first frame to receiving the second frame when a time period from receiving the first frame from the first AP to receiving the second frame from the second AP is shorter than a predetermined value; A communication method for a communication device, comprising:

11. A program for causing a computer to function as each of the means of the communication device according to any one of claims 1 to 9.

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