Title of invention: Communication device, program, and communication method
Technical field
[0001]
　The present disclosure relates to a communication device, a program, and a communication method.
Background technology
[0002]
　In the IEEE 802.11 standard, access control of a large number of terminals is performed by CSMA/CA (Carrier Sense Multiple Access with Collision Aviation). Access control is performed by RTS/CTS frame exchange and the like, and during access control, time required for RTS/CTS frame exchange, waiting time before data transmission, and the like occur. The time required for access control can occupy most of the communication time, and can be a large overhead in communication. Further, since the frame used for access control is transmitted in a band narrower than that of the data frame, the frequency utilization efficiency is lowered due to the transmission of the control frame. Therefore, a technique has been developed that uses a channel different from the channel for transmitting data.
[0003]
　For example, Patent Document 1 discloses a method of using a channel for data transmission and a channel different from the channel for data transmission as tone channels. In the method of Patent Document 1, the tone channel confirms the usage status of the data channel by exchanging signals for confirming the response between the devices. Each terminal can determine whether a data channel is available by carrying out carrier sensing on this tone channel.
Prior art documents
Patent literature
[0004]
Patent Document 1: Japanese Patent Laid-Open No. 2006-246142
Summary of the invention
Problems to be Solved by the Invention
[0005]
　However, since the access control such as acquisition of the data transmission right described in Patent Document 1 is performed by the normal backoff control in the data channel and the RTS/CTS frame exchange, the overhead generated at the time of the access control. Has not been reduced.
[0006]
　Therefore, the present disclosure has been made in view of the above, and provides a new and improved communication device, program, and communication method capable of more efficiently performing wireless communication.
Means for solving the problems
[0007]
　According to the present disclosure, a first communication unit that uses the first channel to perform frame exchange with another communication device based on the IEEE 802.11 standard, and a first communication unit that has a frequency band different from that of the first channel. A second communication unit that performs data frame communication with the other communication device using two channels, and a control unit that controls communication of the data frame based on a result of the frame exchange. A device is provided.
[0008]
　Also, according to the present disclosure, the computer is different from the first communication unit that performs frame exchange based on the IEEE 802.11 standard with another communication device using the first channel, and the first channel is different. A second communication unit that performs data frame communication with the other communication device using a second channel that is a frequency band; and a control unit that controls communication of the data frame based on a result of the frame exchange. A program is provided to function as.
[0009]
　Further, according to the present disclosure, frame exchange based on the IEEE 802.11 standard is performed with another communication device using the first channel, and the second channel that is a frequency band different from the first channel is used. A communication method executed by a processor, comprising: performing communication of a data frame with the other communication device using a channel; and controlling communication of the data frame based on a result of the frame exchange. Will be provided.
Effect of the invention
[0010]
　As described above, according to the present disclosure, it is possible to perform wireless communication more efficiently.
[0011]
　Note that the above effects are not necessarily limited, and in addition to or in place of the above effects, any of the effects shown in this specification, or other effects that can be grasped from this specification. May be played.
Brief description of the drawings
[0012]
FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present disclosure.
FIG. 2 is a block diagram showing a functional configuration example of a communication device according to the same embodiment.
FIG. 3 is a block diagram showing a functional configuration example of a control unit according to the same embodiment.
FIG. 4 is a diagram showing an example of an RTS frame format according to the same embodiment.
FIG. 5 is a diagram showing an example of a format of a CTS frame according to the same embodiment.
FIG. 6 is a sequence diagram showing an operation example of the communication system according to the same embodiment.
FIG. 7 is a flowchart showing an operation example of the communication device on the transmission side according to the same embodiment.
FIG. 8 is a flowchart showing an operation example of the communication device on the receiving side according to the same embodiment.
FIG. 9 is a sequence diagram showing an operation example of a communication system in a modified example according to the same embodiment.
FIG. 10 is a flowchart showing an operation example of the communication device on the transmission side in the modified example of the embodiment.
FIG. 11 is a block diagram showing an example of a schematic configuration of a smartphone.
FIG. 12 is a block diagram showing an example of a schematic configuration of a car navigation device.
FIG. 13 is a block diagram showing an example of a schematic configuration of a wireless access point.
MODE FOR CARRYING OUT THE INVENTION
[0013]
　Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.
[0014]
　The description will be given in the following order.
　1. Overview of the communication system
　2. Embodiment
　　2-1 of the present disclosure Function outline
　　2-2. Functional configuration example
　　2-3. Information to be communicated
　　2-4. Operation example
　3. Modification
　4. Application example
　5. Summary
[0015]
　<1. Outline of Communication System>
　First, a configuration of a communication system according to an embodiment of the present disclosure will be described with reference to FIG. As illustrated in FIG. 1, a communication system according to the present disclosure is a wireless LAN system (for example, a wireless LAN system conforming to IEEE 802.11), and includes an AP (Access Point) 100 that is a base station of a communication device and a child. STA (Station) 200 which is a machine. In FIG. 1, the child device of AP100A is STA200A, and the child device of AP100B is STA200B.
[0016]
　The AP 100A is a communication device that functions as a base station in the wireless LAN system. For example, the AP 100A provides the STA 200A with communication with the external network by being connected to the external network. For example, the AP 100A is connected to the Internet, and provides communication between the STA 200A and a device on the Internet or a device connected via the Internet. The communication method, type, shape, etc. of the AP 100A are not particularly limited. The AP 100B has the same function as that of the AP 100A described above, and the description thereof will be omitted to avoid redundant description.
[0017]
　The STA 200A is a communication device that functions as a slave in the wireless LAN system and communicates with the AP 100A. For example, the STA 200A is an arbitrary device such as a display having a display function, a memory having a storage function, a keyboard and a mouse having an input function, a speaker having a sound output function, and a smartphone having a function of executing advanced calculation processing. May be. The A communication method, type, shape, etc. of the STA 200 are not particularly limited. The STA 200B has the same function as the STA 200B described above, and the description thereof will be omitted to avoid redundant description.
[0018]
　In addition, in the following, in a specific description of the embodiment of the present disclosure, for example, a relationship between a data transmission/reception process between the AP 100A and the STA 200A and a data transmission/reception process between the AP 100B and the STA 200B will be described.
[0019]
　<2. Embodiment of the present disclosure>
　[2-1. Functional Outline] In
　the embodiment of the present disclosure, when a communication device transmits data to another communication device, frame exchange based on the IEEE 802.11 standard is performed, and data (data frame) is transmitted based on the result. Determine whether or not. Specifically, when the AP 100 transmits a data frame to the STA 200, the AP 100 exchanges an RTS/CTS frame with the STA 200 and tries to acquire the transmission right of the data frame. The AP 100 determines whether or not to transmit the data frame to the STA 200 based on whether or not the transmission right of the data frame has been acquired by the RTS/CTS frame exchange.
[0020]
　Here, the RTS/CTS frame exchange is an exchange of an RTS (Request to Send: transmission request) frame and a CTS (Clear to Send: transmission permission) frame between communication devices. By exchanging the RTS/CTS frame, the communication devices can confirm the existence of each other and can appropriately transmit and receive the data frame. In particular, RTS/CTS frame exchange is used as a countermeasure for the hidden terminal problem. The RTS frame is a frame including the transmission request information (first frame), and the CTS frame is a frame including the transmission permission information (second frame).
[0021]
　Further, in the embodiment of the present disclosure, the communication device performs channel exchange and data transmission using channels that are different frequency bands. For example, the AP 100 uses a channel (first channel) having a frequency band of 5 GHz as a control channel when exchanging RTS/CTS frames. Further, the AP 100 uses a channel (second channel) having a frequency band of 6 GHz as a data channel when transmitting a data frame.
[0022]
　The uses of the first channel and the second channel are not particularly limited. For example, the AP 100 may use the first channel having a frequency band of 5 GHz as a data channel and the second channel having a frequency band of 6 GHz as a control channel.
[0023]
　Further, in the embodiment of the present disclosure, the band of the control channel whose frequency band is 5 GHz is a narrow band (for example, 20 MHz), and the communication device serves as a channel for exchanging control information. Further, the band of the data channel whose frequency band is 6 GHz is a wide band (for example, 160 MHz), and the communication device has a role as a channel for exchanging data frames. However, the role of each channel described above is set in consideration of the usage efficiency of the frequency band, and the role of each channel is not limited depending on the resource usage status. For example, when the control channel is busy, the communication device may exchange control information on the data channel. The band of each channel is not particularly limited, and any band may be used for each channel.
[0024]
　The outline of the functions of the communication device according to the embodiment of the present disclosure has been described above. Next, a functional configuration example of the communication device according to the embodiment of the present disclosure will be described.
[0025]
　[2-2. Functional Configuration Example]
　Hereinafter, a functional configuration example of the communication device according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a functional configuration example of the communication device. In the following, the communication device refers to both or one of the AP 100 and the STA 200. Further, since each may have the same functional configuration, only the functional configuration of the AP 100 will be described below, and the description of the functional configuration of the STA 200 will be omitted. Moreover, this is merely an example, and thus the AP 100 and the STA 200 may have different functional configurations. For example, the AP 100 may separately have a function of controlling a plurality of STAs 200.
[0026]
　As shown in FIG. 2, the AP 100 includes a communication unit 110, an antenna 111, a data processing unit 130, a control unit 140, a storage unit 150, and a power supply unit 160.
[0027]
　　(1) Communication Unit 110 The
　communication unit 110 functions as a transmission unit and a reception unit, and has a function of transmitting and receiving an RTS frame, a CTS frame, and a data frame to another communication device. The communication unit 110 according to the embodiment of the present disclosure includes an amplifier unit 112, a wireless interface unit 114, a signal processing unit 116, a channel estimation unit 118, and a modulation/demodulation unit 120. The communication unit 110 may include two or more sets when the amplifier unit 112 and the wireless interface unit 114 are set as one set (in the figure, a case where two or more sets are provided is shown as an example. Exist). The function of the amplifier unit 112 may be included in the wireless interface unit 114.
[0028]
　In the embodiment of the present disclosure, the AP 100 has at least two sets of configurations each including the antenna 111, the amplifier unit 112 of the communication unit 110, and the wireless interface unit 114. Further, for example, one set of the antenna 111, the amplifier unit 112, and the wireless interface unit 114 is a set used for the control channel (first communication unit), and the other set is used for the data channel (second set). Communication section). The first communication unit is used for each communication device to transmit and receive the RTS frame and the CTS frame when the communication device exchanges the RTS/CTS frame with another communication device. The second communication unit is used for each communication device to transmit/receive a data frame when the communication device transmits/receives a data frame to/from another communication device.
[0029]
　Further, the communication unit 110 may not always operate both of the first communication unit used for the control channel and the second communication unit used for the data channel. Accordingly, only one of the first communication unit and the second communication unit may operate. For example, the communication unit 110 may operate only the first communication unit when performing the RTS/CTS frame exchange process, and may operate only the second communication unit when performing the data frame transmission/reception process. Further, for example, the communication unit 110 of the communication device on the data frame transmitting side keeps only the first communication unit constantly operating, and the second communication unit when the CTS frame is received from the communication device on the data frame receiving side. May run. Similarly, in the communication unit 110 of the communication device on the data frame receiving side, only the first communication unit is always operating, and when the CTS frame is transmitted to the communication device on the data frame transmitting side, the second communication unit is activated. You may operate. As described above, the communication device can reduce the power consumption by controlling the operation of the first communication unit and the second communication unit.
[0030]
　　(
　Amplifying Unit 112) The amplifying unit 112 performs signal amplification processing. More specifically, at the time of reception, the amplifier unit 112 amplifies the received signal input from the antenna 111 to a predetermined power and outputs it to the wireless interface unit 114 described later. In addition, at the time of transmission, the amplifier unit 112 amplifies the transmission signal input from the wireless interface unit 114 to a predetermined power and sends it to the antenna 111. Note that these functions may be realized by the wireless interface unit 114.
[0031]
　　(Wireless Interface Unit 114) During
　reception, the wireless interface unit 114 obtains a baseband signal by down-converting the received signal which is an analog signal provided from the amplifier unit 112, and acquires the baseband signal. A reception symbol stream is generated by performing various processes such as filtering and conversion into a digital signal, and outputs it to the signal processing unit 116 described later. In addition, at the time of transmission, the wireless interface unit 114 converts the input from the signal processing unit 116 into an analog signal, performs filtering and up-conversion to the carrier frequency band, and sends it to the amplifier unit 112.
[0032]
　　(Signal Processing Unit 116)
　Upon reception, the signal processing unit 116 performs spatial processing on the reception symbol stream provided from the wireless interface unit 114 to obtain an independent data symbol stream for each reception symbol stream. It is provided to the modulation/demodulation unit 120 described later. In addition, at the time of transmission, the signal processing unit 116 performs spatial processing on the data symbol stream input from the modulation/demodulation unit 120, and provides the obtained one or more transmission symbol streams to each wireless interface unit 114. ..
[0033]
　　(Channel Estimating Unit 118) The
　channel estimating unit 118 calculates the complex channel gain information of the propagation path from the preamble portion and the training signal portion of the received signal provided from each radio interface unit 114. The calculated complex channel gain information is used for demodulation processing in modulation/demodulation section 120 and spatial processing in signal processing section 116.
[0034]
　　(Modulation/Demodulation Unit 120)
　Upon reception, the modulation/demodulation unit 120 acquires reception data by performing demodulation, deinterleaving, and decoding on the data symbol stream provided from the signal processing unit 116, and converts the reception data into data. It is provided to the processing unit 130. Further, at the time of transmission, the modulation/demodulation unit 120 performs encoding, interleaving, and modulation on the frame provided from the data processing unit 130, based on the coding and modulation scheme set by the control unit 140 described later. To generate a data symbol stream and provide the stream to the signal processing unit 116.
[0035]
　　(2) Antenna 111 The
　antenna 111 has a single or a plurality of antenna elements, has a function of outputting a reception signal from another communication device to the amplifier unit 112, and a transmission signal input from the amplifier unit 112. It has a function of transmitting to the communication device.
[0036]
　　(3) Data Processing Unit 130
　At the time of reception, the data processing unit 130 analyzes the MAC header for media access control (MAC) for the received data provided from the modulation/demodulation unit 120, and analyzes the frame. It has a function to perform processing such as error detection inside. In addition, at the time of transmission, the data processing unit 130 generates a packet (data) for transmission and performs processing such as addition of a MAC header and error detection code on the packet to generate a frame for transmission. Then, the frame is provided to the modem unit 120.
[0037]
　In addition, the data processing unit 130 provides the control unit 140 with information necessary for the determination process and the transmission control process in the control unit 140 among the received data. Further, the data processing unit 130 also provides the storage unit 150 with information regarding the data described in the RTS frame and the CTS frame.
[0038]
　　(4) Control Unit 140 The
　control unit 140 has a function of controlling each of the above-described components, and performs processing such as information transfer between the above-described components, parameter setting, and process scheduling. For example, the control unit 140 performs parameter setting in the modulation/demodulation unit 120 and the signal processing unit 116, and packet scheduling in the data processing unit 130. Further, for example, the control unit 140 performs parameter setting and transmission power control in the wireless interface unit 114 and the amplifier unit 112.
[0039]
　Further, in the present disclosure, the control unit 140 performs a determination process for controlling data communication, and controls whether to perform a data frame transmission/reception process based on the result of the determination process.
[0040]
　In order to realize the above functions, the control unit 140 according to the embodiment of the present disclosure includes a determination unit 142 and a transmission control unit 144, as illustrated in FIG. 3.
[0041]
　　(Determination Unit 142) The
　determination unit 142 has a function of performing a determination process for controlling data communication. Specifically, the determination unit 142 causes the communication unit 110 to transmit a data frame to another communication device on the data channel based on the result of the RTS/CTS frame exchange with the other communication device on the control channel by the communication unit 110. Determine whether or not.
[0042]
　For example, the AP 100 transmits the RTS frame from the communication unit 110 to the STA 200 on the control channel. The determination unit 142 confirms whether or not the CTS frame has been received from the STA 200 before a predetermined time (for example, SIFS time) has elapsed. When the communication unit 110 receives the CTS frame before the SIFS time elapses, the determination unit 142 determines that the data can be transmitted to the STA 200, and provides the transmission control unit 144 with the determination result.
[0043]
　Here, the SIFS (Short Inter Frame Space) time is the shortest waiting time in the frame transmission interval. The predetermined time is not limited to SIFS, and any time may be set.
[0044]
　If the communication unit 110 does not receive the CTS frame before the SIFS time elapses, the determination unit 142 determines that the data frame cannot be transmitted to the STA 200 and provides the determination result to the transmission control unit 144. .. Further, the determination unit 142 causes the communication unit 110 to perform the RTS frame transmission process until the determination result that the data frame can be transmitted to the STA 200 is obtained, and repeats the determination process each time.
[0045]
　In the above example, when the AP 100 and the STA 200 succeed in exchanging the RTS/CTS frame, the AP 100 starts transmitting the data frame. However, the determination condition for the AP 100 to start transmitting the data frame is as described above. The example is not limited to. For example, the AP 100 may start transmitting the data frame even if the CTS frame is not received before the SIFS time elapses after transmitting the RTS frame. Even if the STA 200 has not received the RTS frame from the AP 100, the STA 200 may transmit the CTS frame in which the transmission start time of the data frame is described to the AP 100 and specify the transmission start time of the data frame. Further, the frame used by the STA 200 to specify the transmission start time of the data frame is not limited to the RTS/CTS frame, and the STA 200 may specify the transmission start time of the data frame using a Trigger frame or the like.
[0046]
　　(Transmission Control Unit 144) The
　transmission control unit 144 has a function of controlling data communication. Specifically, the transmission control unit 144 has a function of controlling which channel is used to transmit each of the RTS frame, the CTS frame, and the data frame. For example, in the embodiment of the present disclosure, the transmission control unit 144 causes the communication unit 110 to transmit the RTS frame and the CTS frame on the control channel and the data channel on the data channel.
[0047]
　The transmission control unit 144 also has a function of controlling whether or not to cause the communication unit 110 to transmit the data frame based on the determination result of the determination unit 142. For example, the transmission control unit 144 causes the communication unit 110 to transmit the data frame on the data channel when the determination result indicating that the data frame is transmitted is obtained.
[0048]
　　(5) Storage Unit 150 The
　storage unit 150 has a function of storing information regarding the data acquired by the data processing unit 130. Further, when the processing of the control unit 140 requires information regarding data, the storage unit 150 provides the information to the control unit 140 via the data processing unit.
[0049]
　　(6) Power Supply Unit 160 The
　power supply unit 160 is composed of a battery power supply or a fixed power supply and has a function of supplying power to the communication device.
[0050]
　[2-3. Information Communicated]
　Next, an example of information communicated by the AP 100 and the STA 200 will be described with reference to FIGS. 4 and 5.
[0051]
　In the embodiment of the present disclosure, the information communicated between the communication devices is an RTS frame, a CTS frame, and a data frame. The RTS frame is, for example, information transmitted by the AP 100 to the STA 200 on the control channel. The CTS frame is information that the STA 200 transmits to the AP 100 on the control channel. The data frame is information transmitted by the AP 100 to the STA 200 on the data channel. The configuration of each frame will be specifically described below.
[0052]
　　(1) RTS Frame
　An example of the format of the RTS frame will be described with reference to FIG. The structure of a normal RTS frame is a structure having, for example, "Frame Control", "Duration", "RA", "TA", and "FCS" fields among the fields shown in FIG.
[0053]
　Further, the RTS frame according to the embodiment of the present disclosure usually includes a field of additional information regarding data described in the data frame. The additional information is, for example, “Format of Data”, “BSS Color of Data”, “Spatial Reuse of Data”, “Bandwidth of Data”, and “Duration of Data” fields. Note that the format of the frame is just an example. Each field of the RTS frame will be described below.
[0054]
　The Frame Control field has information about the type of frame, the transmission direction, the frame attribute, and the like. Information indicating the RTS frame as the type of frame corresponds to the transmission request information. The Duration field has information about a scheduled period for using the wireless line. The RA field has information about the receiving station MAC address (RA: Receiver Address). The TA field has information about a transmitting station MAC address (TA: Transmitter Address).
[0055]
　The Format of Data field has Format information. The BSS Color of Data field has BSS identification information. The Spatial Reuse of Data field has spatial reuse information.
[0056]
　The Bandwidth of Data field has band information. The Duration of Data field has transmission time information. The FCS field is a field for performing frame error detection (FCS: Frame Check Sequence).
[0057]
　The additional information related to the data can be described in the RTS frame so that the communication device on the transmission side can indicate detailed information of the data to be transmitted to the communication device on the reception side. Further, the communication device on the receiving side can know the additional information regarding the data in advance, and can reduce the overhead in the data frame on the data channel.
[0058]
　　(2) CTS Frame
　Next, an example of the format of the CTS frame will be described with reference to FIG. The configuration of a normal CTS frame is a configuration having, for example, the "Frame Control", "RA", and "FCS" fields in the information shown in FIG. In the embodiment of the present disclosure, the CTS frame additionally includes, for example, a “Transmit Start Time of Data” field and a “Duration of Data” field as fields of information regarding a data transmission start time and a data transmission end time. Note that the format of the frame is just an example. Each field of the CTS frame will be described below.
[0059]
　The Frame Control field has information about the type of frame, the transmission direction, the frame attribute, and the like. Information indicating the CTS frame as the type of frame corresponds to the transmission permission information. The RA field has information about the receiving station MAC address (RA: Receiver Address).
[0060]
　The Transmit Start Time of Data field has information on the transmission start time of data. The Duration of Data field has information on the transmission time of data. The FCS field is a field for performing frame error detection (FCS: Frame Check Sequence). The transmission end time can be calculated from the data transmission start time and the data transmission time.
[0061]
　　(3) Data frame A
　data frame is a frame having data to be transmitted and received by the communication device and additional information regarding the data. In the embodiment of the present disclosure, the additional information is described in the RTS frame, not in the data frame. The specific field of the additional information is the same as the content described in (1) RTS frame, and the description thereof is omitted to avoid redundant description. Note that the AP 100 does not describe the additional information described in the RTS frame in the data frame, but describes the Training Field necessary for demodulating the data frame received by the STA 200 in the data frame and transmits it.
[0062]
　Further, the frame in which the additional information regarding the data is described is not limited to the RTS frame, and may be described in any frame. For example, the additional information regarding the data may be described in the CTS frame. When the additional information related to the data is described in the CTS frame, the communication device on the reception side can instruct the communication device on the transmission side to transmit the data described in the additional information.
[0063]
　The example of the information communicated by the AP 100 and the STA 200 according to the embodiment of the present disclosure has been described above with reference to FIGS. Next, an operation example of the communication system according to an embodiment of the present disclosure will be described.
[0064]
　[2-4. Operation Example]
　An operation example of the communication system according to an embodiment of the present disclosure will be described. Hereinafter, an operation example of the communication system will be described with reference to FIGS.
[0065]
　　(1) Operation Example of Communication System An operation example of the
　entire communication system according to the embodiment of the present disclosure will be described with reference to FIG. 6. FIG. 6 is a sequence diagram showing an operation example of the communication system. In the embodiment of the present disclosure, the process of acquiring the transmission right of the data frame necessary for the determination process for controlling the communication of the data frame is performed only by the control channel. In addition, the communication processing of the data frame is performed only in the data channel.
[0066]
　As shown in FIG. 6, the AP 100A first transmits the RTS frame 308 to the STA 200A on the control channel after the backoff time 300 has elapsed (time T 1 ). Upon receiving the RTS frame 308, the STA 200A transmits the CTS frame 312 to the AP 100A and the STA 200A via the control channel (time T 2 ).
[0067]
　At this time, since the AP 100B uses the data channel for transmitting the Data 304, the AP 100A and the STA 200A cannot use the data channel. Therefore, the STA 200A describes the information of the time T 3 at which the AP 100B completes the transmission of the data frame on the data channel in the Transmit Start Time of Data field of the CTS frame as the transmission start time, and transmits the CTS frame on the control channel. This transmission start time is information for the AP 100A, which is scheduled to transmit the next data frame.
[0068]
　Further, the STA 200A also describes the transmission time information of the data frame described in the Duration of Data field of the RTS frame received from the AP 100A on the control channel, in the Duration of Data field of the CTS frame. This transmission time information is information for the STA 200B that may receive the data frame next to the STA 200A. For example, it is assumed that the STA 200B receives the RTS frame from the AP 100B while the STA 200A is receiving the data frame. The STA 200B can describe the transmission time information previously described in the CTS frame received from the STA 200A in the Duration of Data field of the CTS frame and transmit it to the AP 100B.
[0069]
　After AP 100B completes the transmission of Data 304 on the data channel (time T 3 ), AP 100 A starts transmitting Data 316 on the data channel to STA 200 A (time T 3 ). The AP 100B transmits the RTS frame 324 on the control channel to the STA 200B in order to transmit the data frame again after the transmission of the Data 304 is completed and the backoff time 320 has elapsed (time T 4 ). Upon receiving the RTS frame 324 on the control channel, the STA 200B describes the same information as in the CTS frame 328 when the STA 200A transmitted the CTS frame 312 on the control channel, and transmits the CTS frame 328 to the AP 100B and the STA 200A on the control channel. (Time T 5 ). Then, after the AP 100A completes transmitting Data 316 on the data channel (time T 6 ), the AP 100B transmits Data 332 on the data channel to the STA 200 B (time T 6 -time T 7 ).
[0070]
　　(2) Example of Operation of Communication Device on Data Frame Transmission Side
　Next, a specific RTS/CTS frame exchange process in the communication device on the data frame transmission side will be described with reference to FIG. 7. In the following, for example, the communication device on the transmission side is the AP 100 and the communication device on the reception side is the STA 200. First, the AP 100 transmits an RTS frame on the control channel to the STA 200A before starting the data frame transmission process (step S1000). After transmitting the RTS frame, the AP 100 confirms whether or not the CTS frame is received on the control channel before the SIFS time elapses (step S1004). When the CTS frame is received (step S1004/YES), the AP 100 transmits the data frame to the STA 200 via the data channel at the transmission start time described in the received CTS frame (step S1008). When the CTS frame cannot be received (step S1004/NO), the AP 100 repeats the RTS frame transmission process and the determination process on the control channel until the CTS frame can be received.
[0071]
　　(3) Operation Example of Communication Device on Data Frame Reception Side
　Next, with reference to FIG. 8, a specific RTS/CTS frame exchange process in the communication device on the data frame reception side will be described. Hereinafter, for example, similarly to the description of FIG. 7, it is assumed that the communication device on the reception side is the STA 200 and the communication device on the transmission side is the AP 100. First, the STA 200 receives the RTS frame on the control channel (step S1100). The STA 200 holds the additional information regarding the data described in the received RTS frame in the storage unit 150 (step S1104). The STA 200 confirms whether a data frame reserved for transmission exists in the data channel (step S1108). The STA 200 determines the time when the transmission of all data frames reserved for transmission is completed as the transmission start time of the data frame (step S1112). After determining the transmission start time, the STA 200 writes the transmission start time, which is the time when the AP 100 starts transmitting the data frame on the data channel, in the CTS frame (step S1116), and transmits the CTS frame to the AP 100 on the control channel ( Step S1120).
[0072]
　The embodiments of the present disclosure have been described above with reference to FIGS. 2 to 8. Subsequently, a modified example according to the embodiment of the present disclosure will be described.
[0073]
　<3. Modified Example>
　Hereinafter, a modified example of the embodiment of the present disclosure will be described. Note that the modified examples described below may be applied to the embodiment of the present disclosure alone, or may be applied to the embodiment of the present disclosure in combination. Further, the modified example may be applied instead of the configuration described in the embodiment of the present disclosure, or may be additionally applied to the configuration described in the embodiment of the present disclosure.
[0074]
　In the embodiment of the present disclosure, the example in which the acquisition processing of the transmission right of the data frame is performed in the control channel has been described. However, the process of acquiring the transmission right of the data frame may be performed in the data channel by a method different from the method performed in the control channel. For example, the AP 100 confirms the usage status of the data channel and the control channel before starting the transmission of the data frame. The AP 100 may select a channel to be used according to the usage status of each channel, and may perform a process of acquiring a transmission right of a data frame by a method according to the selected channel. Hereinafter, an example of a specific process will be described with reference to FIGS. 9 and 10.
[0075]
　　(1) Operation Example of Communication System in Modification Example
　First, an example of a specific operation of the communication system in the modification example will be described with reference to FIG. 9. First, the AP 100A confirms the usage status of the data channel and the control channel before transmitting the data frame to the STA 200A. As a result of the confirmation, since the data channel is in the unused state, the AP 100A tries to acquire the transmission right of the data frame by the backoff control 400 on the data channel (time T 11 ). When the AP 100A can acquire the transmission right of the data frame by the backoff control 400, the AP 100A transmits the Data 404 to the STA 200A through the data channel (time T 12 -time T 15 ). Note that when the transmission right is acquired through the data channel, the AP 100 and the STA 200A do not exchange the RTS/CTS frame, so the AP 100 does not transmit the additional information to the STA 200A. Therefore, the AP 100 may describe the additional information in the data frame.
[0076]
　While the AP 100A is transmitting a data frame on the data channel, if the AP 100B tries to transmit the data frame, the usage statuses of the data channel and the control channel are confirmed before starting the transmission of the data frame. As a result of the confirmation, it was found that the AP 100B was using the data channel by another communication device. At the same time, since the AP 100B has also found that the control channel is in the unused state, the AP 100B transmits the RTS frame 412 on the control channel to the STA 200B after the backoff time 408 has elapsed (time T 13 ). The STA 200B transmits the CTS frame 416 on the control channel to the AP 100B based on the information described in the received RTS frame 412 (time T 14 ). Based on the information described in the received CTS frame 416, the AP 100B transmits Data 420 on the data channel to the STA 200B after the AP 100A completes transmitting Data 404 on the data channel (time T 15 ) (time T 15 -time T 16 ). ).
[0077]
　　(2) Operation Example of Communication Device on Data Frame Transmission Side in Modification Example
　Next, with reference to FIG. 10, a specific data transmission process in the communication device on the data frame transmission side in the modification example will be described. In the following, it is assumed that the communication device on the transmission side is the AP 100, for example. First, the AP 100 confirms the usage status of the data channel and the control channel before starting the data frame transmission process (step S2000). If the data channel is unused (step S2004/YES), the AP 100 acquires the transmission right of the data frame by backoff control on the data channel (step S2008). After acquiring the transmission right of the data frame, the AP 100 transmits the data frame on the data channel (step S2012).
[0078]
　When the data channel is in use (step S2004/NO), the AP 100 confirms the use state of the control channel (step S2016). When the control channel is unused (step S2016/YES), the AP 100 transmits the RTS frame on the control channel (step S2020). When the AP 100 receives the CTS frame on the control channel before the SIFS time elapses after the RTS frame is transmitted (step S2024/YES), the AP 100 transmits the data frame. Specifically, the AP 100 transmits the data frame on the data channel at the transmission start time described in the received CTS frame (step S2028). If the AP 100 does not receive the CTS frame on the control channel after the RTS frame is transmitted and before the SIFS time elapses (step S2024/NO), the AP 100 transmits the RTS frame on the control channel again (step S2020). ).
[0079]
　When the control channel is also in use (step S2016/NO), the AP 100 waits until either the data channel or the control channel becomes unused (step S2032).
[0080]
　　(3) Operation Example of Communication Device on Data Frame Receiving Side in
　Modification Example An operation example of the communication device on the data frame transmitting side in the modification example is the same as the operation example of the communication device on the data frame transmitting side in the embodiment of the present disclosure. Therefore, the description thereof will be omitted to avoid a duplicated description.
[0081]
　The modification according to the embodiment of the present disclosure has been described above with reference to FIGS. 9 and 10. Subsequently, an application example of the technology according to the embodiment of the present disclosure will be described.
[0082]
　<4. Application Example>
　The technology according to the present disclosure can be applied to various products. For example, the STA 200 is a smartphone, a tablet PC (Personal Computer), a notebook PC, a mobile terminal such as a portable game terminal or a digital camera, a fixed terminal such as a television receiver, a printer, a digital scanner or a network storage, or a car navigation device. May be realized as an in-vehicle terminal such as. In addition, the STA 200 is realized as a terminal (also referred to as an MTC (Machine Type Communication) terminal) that performs M2M (Machine To Machine) communication, such as a smart meter, a vending machine, a remote monitoring device, or a POS (Point Of Sale) terminal. May be. Further, the STA 200 may be a wireless communication module mounted on these terminals (for example, an integrated circuit module configured by one die).
[0083]
　On the other hand, for example, the AP 100 may be realized as a wireless LAN access point (also referred to as a wireless base station) having a router function or not having a router function. Further, the AP 100 may be realized as a mobile wireless LAN router. Further, the AP 100 may be a wireless communication module mounted on these devices (for example, an integrated circuit module configured by one die).
[0084]
　[4-1. First Application Example]
　FIG. 11 is a block diagram showing an example of a schematic configuration of a smartphone 900 to which the technology according to the present disclosure can be applied. The smartphone 900 includes a processor 901, a memory 902, a storage 903, an external connection interface 904, a camera 906, a sensor 907, a microphone 908, an input device 909, a display device 910, a speaker 911, a wireless communication interface 913, an antenna switch 914, an antenna 915, A bus 917, a battery 918 and an auxiliary controller 919 are provided.
[0085]
　The processor 901 may be, for example, a CPU (Central Processing Unit) or a SoC (System on Chip), and controls the functions of the application layer and other layers of the smartphone 900. The memory 902 includes a RAM (Random Access Memory) and a ROM (Read Only Memory), and stores programs and data executed by the processor 901. The storage 903 may include a storage medium such as a semiconductor memory or a hard disk. The external connection interface 904 is an interface for connecting an external device such as a memory card or a USB (Universal Serial Bus) device to the smartphone 900.
[0086]
　The camera 906 has, for example, an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and generates a captured image. The sensor 907 may include a sensor group such as a positioning sensor, a gyro sensor, a geomagnetic sensor, and an acceleration sensor, for example. The microphone 908 converts a voice input to the smartphone 900 into a voice signal. The input device 909 includes, for example, a touch sensor that detects a touch on the screen of the display device 910, a keypad, a keyboard, a button or a switch, and receives an operation or information input from a user. The display device 910 has a screen such as a liquid crystal display (LCD) or an organic light emitting diode (OLED) display, and displays the output image of the smartphone 900. The speaker 911 converts the audio signal output from the smartphone 900 into audio.
[0087]
　The wireless communication interface 913 supports one or more of wireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and 11ad, and executes wireless communication. The wireless communication interface 913 can communicate with another device via a wireless LAN access point in the infrastructure mode. Further, the wireless communication interface 913 can directly communicate with another device in an ad hoc mode or a direct communication mode such as Wi-Fi Direct (registered trademark). In Wi-Fi Direct, one of the two terminals operates as an access point, unlike the ad hoc mode, but communication is performed directly between the terminals. The wireless communication interface 913 can typically include a baseband processor, an RF (Radio Frequency) circuit, a power amplifier, and the like. The wireless communication interface 913 may be a one-chip module in which a memory that stores a communication control program, a processor that executes the program, and related circuits are integrated. The wireless communication interface 913 may support other types of wireless communication systems such as a short-range wireless communication system, a proximity wireless communication system, and a cellular communication system in addition to the wireless LAN system. The antenna switch 914 switches the connection destination of the antenna 915 among a plurality of circuits included in the wireless communication interface 913 (for example, circuits for different wireless communication systems). The antenna 915 has a single or a plurality of antenna elements (for example, a plurality of antenna elements forming a MIMO antenna), and is used for transmitting and receiving a radio signal by the radio communication interface 913.
[0088]
　Note that the smartphone 900 is not limited to the example of FIG. 11, and may include a plurality of antennas (for example, an antenna for a wireless LAN and an antenna for a close proximity wireless transfer method). In that case, the antenna switch 914 may be omitted from the configuration of the smartphone 900.
[0089]
　The bus 917 connects the processor 901, the memory 902, the storage 903, the external connection interface 904, the camera 906, the sensor 907, the microphone 908, the input device 909, the display device 910, the speaker 911, the wireless communication interface 913, and the auxiliary controller 919 to each other. .. The battery 918 supplies power to each block of the smartphone 900 shown in FIG. 11 via a power supply line partially shown by a broken line in the figure. The auxiliary controller 919 operates the minimum necessary functions of the smartphone 900 in the sleep mode, for example.
[0090]
　Note that the smartphone 900 may operate as a wireless access point (software AP) by the processor 901 executing the access point function at the application level. Further, the wireless communication interface 913 may have a wireless access point function.
[0091]
　[4-2. Second Application Example]
　FIG. 12 is a block diagram showing an example of a schematic configuration of a car navigation device 920 to which the technology according to the present disclosure can be applied. The car navigation device 920 includes a processor 921, a memory 922, a GPS (Global Positioning System) module 924, a sensor 925, a data interface 926, a content player 927, a storage medium interface 928, an input device 929, a display device 930, a speaker 931 and wireless communication. An interface 933, an antenna switch 934, an antenna 935, and a battery 938 are provided.
[0092]
　The processor 921 may be, for example, a CPU or a SoC, and controls the navigation function and other functions of the car navigation device 920. The memory 922 includes RAM and ROM and stores programs and data executed by the processor 921.
[0093]
　The GPS module 924 measures the position (eg, latitude, longitude, and altitude) of the car navigation device 920 using GPS signals received from GPS satellites. The sensor 925 may include a sensor group such as a gyro sensor, a geomagnetic sensor, and an atmospheric pressure sensor, for example. The data interface 926 is connected to the vehicle-mounted network 941 via, for example, a terminal (not shown) and acquires data generated on the vehicle side such as vehicle speed data.
[0094]
　The content player 927 reproduces the content stored in the storage medium (eg, CD or DVD) inserted in the storage medium interface 928. The input device 929 includes, for example, a touch sensor, a button, or a switch that detects a touch on the screen of the display device 930, and receives an operation or information input from the user. The display device 930 has a screen such as an LCD or an OLED display, and displays a navigation function or an image of content to be reproduced. The speaker 931 outputs the navigation function or the sound of the reproduced content.
[0095]
　The wireless communication interface 933 supports one or more of wireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and 11ad, and executes wireless communication. The wireless communication interface 933 can communicate with another device via a wireless LAN access point in the infrastructure mode. Further, the wireless communication interface 933 can directly communicate with another device in an ad hoc mode or a direct communication mode such as Wi-Fi Direct. The wireless communication interface 933 may typically include a baseband processor, an RF circuit, a power amplifier, and the like. The wireless communication interface 933 may be a one-chip module in which a memory that stores a communication control program, a processor that executes the program, and related circuits are integrated. The wireless communication interface 933 may support other types of wireless communication systems such as a short-range wireless communication system, a close proximity wireless communication system, and a cellular communication system in addition to the wireless LAN system. The antenna switch 934 switches a connection destination of the antenna 935 among a plurality of circuits included in the wireless communication interface 933. The antenna 935 has a single or a plurality of antenna elements and is used for transmitting and receiving a radio signal by the radio communication interface 933.
[0096]
　Note that the car navigation device 920 is not limited to the example of FIG. 12, and may include a plurality of antennas. In that case, the antenna switch 934 may be omitted from the configuration of the car navigation device 920.
[0097]
　The battery 938 supplies electric power to each block of the car navigation device 920 shown in FIG. 12 via a power supply line partially shown by a broken line in the figure. Further, the battery 938 stores electric power supplied from the vehicle side.
[0098]
　The wireless communication interface 933 may operate as the above-described AP 100 and provide a wireless connection to a terminal owned by a user in a vehicle.
[0099]
　The technology according to the present disclosure may be implemented as an in-vehicle system (or vehicle) 940 including one or more blocks of the car navigation device 920 described above, an in-vehicle network 941, and a vehicle-side module 942. The vehicle-side module 942 generates vehicle-side data such as vehicle speed, engine speed, or failure information, and outputs the generated data to the vehicle-mounted network 941.
[0100]
　[4-3. Third Application Example]
　FIG. 13 is a block diagram showing an example of a schematic configuration of a wireless access point 950 to which the technology according to the present disclosure can be applied. The wireless access point 950 includes a controller 951, a memory 952, an input device 954, a display device 955, a network interface 957, a wireless communication interface 963, an antenna switch 964, and an antenna 965.
[0101]
　The controller 951 may be, for example, a CPU or a DSP (Digital Signal Processor), and has various functions (for example, access restriction, routing, encryption, and firewall) of the IP (Internet Protocol) layer and higher layers of the wireless access point 950. And log management). The memory 952 includes a RAM and a ROM, and stores a program executed by the controller 951 and various control data (for example, a terminal list, a routing table, an encryption key, a security setting and a log).
[0102]
　The input device 954 includes, for example, a button or a switch, and receives an operation from the user. The display device 955 includes an LED lamp or the like, and displays the operation status of the wireless access point 950.
[0103]
　The network interface 957 is a wired communication interface for the wireless access point 950 to connect to the wired communication network 958. The network interface 957 may have a plurality of connection terminals. The wired communication network 958 may be a LAN such as Ethernet (registered trademark) or may be a WAN (Wide Area Network).
[0104]
　The wireless communication interface 963 supports one or more of wireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and 11ad, and provides a wireless connection as an access point to nearby terminals. The wireless communication interface 963 may typically include a baseband processor, an RF circuit, a power amplifier, and the like. The wireless communication interface 963 may be a one-chip module in which a memory that stores a communication control program, a processor that executes the program, and a related circuit are integrated. The antenna switch 964 switches the connection destination of the antenna 965 among a plurality of circuits included in the wireless communication interface 963. The antenna 965 has a single or a plurality of antenna elements and is used for transmitting and receiving a radio signal by the radio communication interface 963.
[0105]
　<5. Conclusion> From the
　above description, the communication device according to the present disclosure can perform RTS/CTS frame exchange using a control channel, and can perform data frame communication processing on a data channel that is a frequency band different from the control channel. Is. As described above, it is possible to provide a new and improved communication device, program, and communication method capable of more efficiently performing wireless communication.
[0106]
　The preferred embodiments of the present disclosure have been described above in detail with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that the invention also belongs to the technical scope of the present disclosure.
[0107]
　The series of processes performed by each device described in the present specification may be realized using any of software, hardware, and a combination of software and hardware. The program configuring the software is stored in advance in a recording medium (non-transitory medium: non-transmission media) provided inside or outside each device, for example. Then, each program is read into the RAM at the time of execution by a computer and executed by a processor such as a CPU.
[0108]
　Further, the processes described by using the flowcharts and the sequence diagrams in this specification do not necessarily have to be executed in the illustrated order. Some processing steps may be performed in parallel. In addition, additional processing steps may be adopted, and some processing steps may be omitted.
[0109]
　Further, the effects described in the present specification are merely illustrative or exemplary, and are not limitative. That is, the technique according to the present disclosure may have other effects that are obvious to those skilled in the art from the description of the present specification, in addition to or instead of the above effects.
[0110]
　The following configurations also belong to the technical scope of the present disclosure.
(1)
　A first communication unit that uses the first channel to exchange frames with another communication device based on the IEEE 802.11 standard, and a second
　channel that is a frequency band different from the first channel. A communication device, comprising: a second communication unit that performs data frame communication with the other communication device using; and
　a control unit that controls communication of the data frame based on a result of the frame exchange
　.
(2)
　The first communication unit transmits and receives a first frame, which is a frame including transmission request information, and a second frame, which is a frame including transmission permission information, to and from the other communication device. The communication device according to 1).
(3)
　The communication device according to (2), wherein the first frame includes additional information regarding the data frame.
(4) The
　additional information is information included in at least one of a Format of Data field, a BSS Color of Data field, a Spatial Reuse of Data field, a Bandwidth of Data field, or a Duration of Data field. The communication device according to 3).
(5)
　The communication device according to (2), wherein the second frame includes a transmission start time when the data frame is transmitted from the second communication unit to the other communication device.
(6)
　When the control unit determines that the data frame can be transmitted to the other communication device based on the result of the frame exchange in the first communication unit, the control unit transmits the data frame to the second communication unit. The communication device according to any one of (1) to (5), which is transmitted to the other communication device.
(7) The
　control unit receives the second frame from another communication device within a predetermined time after the first communication unit transmits the first frame to the other communication device, The communication device according to (6), which causes the second communication unit to transmit the data frame to the other communication device.
(8)
　When the first communication unit receives the first frame from another communication device, the control unit determines a transmission start time, and determines a second frame including the transmission start time as the other frame. The communication device according to (6), which causes the communication device to transmit the first communication unit.
(9)
　The second communication unit receives the data frame transmitted from the other communication device, and transmits the data frame to the other communication device based on an instruction from the control unit. The communication device according to any one of 1) to (8).
(10)
　The communication device according to (9), wherein the second communication unit transmits the data frame that does not include additional information.
(11)
　The communication device according to any one of (1) to (10), wherein the first communication unit performs frame exchange with another communication device by RTS/CTS frame exchange.
(12) A
　computer is provided with a
　first communication unit that performs frame exchange based on the IEEE 802.11 standard with another communication device using the first channel, and a first communication unit
　that has a frequency band different from that of the first channel. with 2 channels, and a second communication unit for communicating the other communication device and the data frame,
　based on the result of the frame exchange, and a control unit for controlling the communication of the data frame,
　to function as Of the program.
(13)
　Performing frame exchange based on the IEEE 802.11 standard with another communication device using the first channel, and using a
　second channel that is a frequency band different from the first channel, A 　communication method executed by a processor ,
　comprising: performing communication of a data frame with the other communication device; and controlling communication of the data frame based on a result of the frame exchange
.
Explanation of symbols
[0111]
　100 AP
　110 communication unit
　111 antenna
　112 amplifier unit
　114 wireless interface unit
　116 signal processing unit
　118 channel estimation unit
　120 modulation/demodulation unit
　130 data processing unit
　140 control unit
　142 determination unit
　144 transmission control unit
　150 storage unit
　160 power supply unit
　200 STA
The scope of the claims
[Claim 1]
　A first communication unit that uses the first channel to exchange frames with another communication device based on the IEEE 802.11 standard, and a second
　channel that is a frequency band different from the first channel are used. A communication device, comprising: a second communication unit that performs data frame communication with the other communication device; and
　a control unit that controls communication of the data frame based on a result of the frame exchange
　.
[Claim 2]
　The said 1st communication part transmits/receives the 1st frame which is a frame containing transmission request information, and the 2nd frame which is a frame containing transmission permission information with the said other communication apparatus. Communication device.
[Claim 3]
　The communication device according to claim 2, wherein the first frame includes additional information regarding the data frame.
[Claim 4]
　The additional information is information included in at least one of a Format of Data field, a BSS Color of Data field, a Spatial Reuse of Data field, a Bandwidth of Data field, or a Duration of Data field. Communication device.
[Claim 5]
　The communication device according to claim 2, wherein the second frame includes a transmission start time when the data frame is transmitted from the second communication unit to the other communication device.
[Claim 6]
　When the control unit determines that the data frame can be transmitted to the other communication device based on the result of the frame exchange in the first communication unit, the second communication unit transmits the data frame to the other data frame. The communication device according to claim 1, which is transmitted to the communication device.
[Claim 7]
　When the first communication unit receives the second frame from the other communication device within a predetermined time after the first communication unit transmits the first frame to the other communication device, the control unit determines the second The communication device according to claim 6, wherein the communication unit is configured to transmit the data frame to the other communication device.
[Claim 8]
　When the first communication unit receives the first frame from another communication device, the control unit determines a transmission start time and sends a second frame including the transmission start time to the other communication device. The communication device according to claim 6, which is transmitted to the first communication unit.
[Claim 9]
　The second communication unit receives the data frame transmitted from the other communication device, and transmits the data frame to the other communication device based on an instruction from the control unit. Communication device.
[Claim 10]
　The communication device according to claim 9, wherein the second communication unit transmits the data frame that does not include additional information.
[Claim 11]
　The communication device according to claim 1, wherein the first communication unit performs frame exchange with another communication device by RTS/CTS frame exchange.
[Claim 12]
　The computer includes a
　first communication unit that uses the first channel to exchange frames with another communication device based on the IEEE 802.11 standard, and a second
　channel that is a frequency band different from the first channel. using said another communication apparatus and a second communication unit for communicating data frames,
　based on the result of the frame exchange, and a control unit for controlling the communication of the data frame
　to function as a program ..
[Claim 13]
　The first channel is used to perform frame exchange based on the IEEE 802.11 standard with another communication device, and
　the second channel, which is a frequency band different from the first channel, is used to perform the other exchange . A communication 　method executed by a processor, comprising:
　communicating a data frame with a communication device; and controlling communication of the data frame based on a result of the frame exchange