Patent Description:
In the IEEE802. <NUM> standard, access control of a number of terminals is performed according to CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). The access control is performed using RTS/CTS frame exchange and, at the time of performing the access control, some period of time is taken for the RTS/CTS frame exchange and some period of time is taken as the latency time prior to data transmission. The time taken by the access control sometimes accounts for the major portion of the communication time, and can be a significant overhead in the communication. Moreover, since the frames used in the access control are transmitted in a narrower band frequency than the band frequency used for transmitting data frames, the transmission of control frames results in a decline in the frequency usage efficiency. In that regard, a technology has been developed in which a channel that is different than the channel for data transmission is also used.

For example, in Patent Literature <NUM>, a method has been disclosed in which the channel for data transmission is used along with a tone channel representing the channel different than the channel for data transmission. In the method disclosed in Patent Literature <NUM>, as a result of transmitting and receiving signals meant for confirming responses among the devices, the tone channel confirms the usage status of the data channel. Each terminal performs carrier sensing with respect to the tone channel, and becomes able to determine whether the data channel is available.

Patent Literature <NUM>: <CIT>
<CIT> relates to an apparatus and a method for supporting access for multi users to perform communication through multi nodes by efficiently using multi channels in a communication system of a multi user environment having the multi nodes.

<CIT> is directed to a method and apparatus for performing channel aggregation to communicate over a non-contiguous spectrum, such as television white space (TVWS), using a plurality of aggregated channels including a primary channel and at least one non-primary channel.

However, since the access control for acquiring the data transmission right as disclosed in Patent Literature <NUM> is performed according to the normal back-off control via the data channel and according to the RTS/CTS frame exchange, there is no reduction in the overhead occurring during the access control.

In that regard, the application concerned is made in view of the issues mentioned above, and a communication device, a program, and a communication method in a new and improved form are provided that enable performing radio communication in a more efficient manner.

As explained above, according to the application concerned, it becomes possible to perform radio communication in a more efficient manner.

Meanwhile, the abovementioned effect is not necessarily limited in scope and, in place of or in addition to the abovementioned effect, any other effect indicated in the present written description or any other effect that may occur from the present written description can also be achieved.

A preferred embodiment of the application concerned is described below in detail with reference to the accompanying drawings. In the present written description and the drawings, the constituent elements having practically identical functional configuration are referred to by the same reference numerals, and the corresponding explanation is not given repeatedly.

The explanation is given in the following sequence.

Firstly, explained below with reference to <FIG> is a configuration of a communication system according to the embodiment of the application concerned. As illustrated in <FIG>, the communication system according to the application concerned is a wireless LAN system (for example, a wireless LAN system compatible to the IEEE802. <NUM> standard), and is configured with APs (Access Points) <NUM>, which represent the base stations of communication devices, and STAs (Stations) <NUM>, which represent child devices. With reference to <FIG>, an STA 200A represents the child device of an AP 100A, and an STA 200B represents the child device of an AP 100B.

The AP 100A is a communication device functioning as a base station in the wireless LAN system. For example, the AP 100A gets connected with an external network, and enables the STA 200A to communicate with that external network. For example, the AP 100A gets connected to the Internet, and enables the STA 200A to communicate with devices on the Internet or devices that get connected to the Internet. Herein, there is no particular restriction on the communication, the type, and the shape of the AP 100A. The AP 100B has identical functions to the functions of the AP 100A, and the explanation thereof is not given so as to avoid repetition.

The STA 200A functions as a child device in the wireless LAN system, and is a communication device that performs communication with the AP 100A. For example, the STA 200A can be an arbitrary device such as a display having the display function, a memory having the storage function, a keyboard and a mouse having the input function, a speaker having the sound output function, or a smartphone having the function of performing sophisticated calculations. Herein, there is no particular restriction on the communication method, the type, and the shape of the STA 200A. The STA 200B has identical functions to the functions of the STA 200B, and the explanation thereof is not given so as to avoid repetition.

In the following specific explanation of the embodiment of the application concerned, for example, the explanation is given about the relationship between the transmission and reception of data performed between the AP 100A and the STA 200A and the transmission and reception of data performed between the AP 100B and the STA 200B.

In the embodiment of the application concerned, at the time of transmitting data to another communication device, the concerned communication device performs frame exchange based on the IEEE802. <NUM> standard and accordingly determines whether or not to transmit data (data frames). More particularly, at the time of transmitting data frames to the STA <NUM>, the AP <NUM> performs RTS/CTS frame exchange with the STA <NUM>, and attempts to acquire the transmission right for transmitting data frames. Based on whether or not the transmission right for transmitting data frames could be acquired as a result of performing the RTS/CTS frame exchange, the AP <NUM> determines whether or not to transmit data frames to the STA <NUM>.

The RTS/CTS frame exchange implies exchanging RTS (Request to Send) frames and CTS (Clear to Send) frames between communication devices. As a result of performing the RTS/CTS frame exchange, it becomes possible for the communication devices to confirm the presence of each other, and to transmit and receive data frames in an appropriate manner. Particularly, the RTS/CTS frame exchange is used as a countermeasure against the hidden-terminal problem. An RTS frame is a frame (first-type frame) including transmission request information, and a CTS frame is a frame (second-type frame) including transmission permission information.

In the embodiment of the application concerned, at the time of performing frame exchange and data transmission, a communication device uses channels having different frequency bands. For example, at the time of performing the RTS/CTS frame exchange, the AP <NUM> uses the channel having the frequency band of <NUM> (a first channel) as the control channel. Moreover, at the time of transmitting data frames, the AP <NUM> uses the channel having the frequency band of <NUM> (a second channel) as the data channel.

Herein, there is no particular restriction on the usage of the first channel and the second channel. For example, the AP <NUM> can use the first channel having the frequency band of <NUM> as the data channel, and can use the second channel having the frequency band of <NUM> as the control channel.

In the embodiment of the application concerned, the control channel having the frequency band of <NUM> has a narrow bandwidth (for example, <NUM>), and serves as the channel used by the communication devices to communicate control information. The data channel having the frequency band of <NUM> has a wide bandwidth (for example, <NUM>), and serves as the channel used by the communication devices to communicate data frames. However, the role of each channel is set by taking into account the usage efficiency of the frequency bands; and, depending on the usage status of the resources, there is no restriction on the roles of the channels. For example, if the usage status of the control channel indicates congestion, the communication devices can communicate the control information via the data channel. Moreover, there is no particular restriction on the bandwidths of the channels, and each channel can have an arbitrary bandwidth.

Till now, the explanation was given about the functional overview of the communication devices according to the embodiment of the application concerned. Given below is the explanation of a functional configuration example of the communication device according to the embodiment of the application concerned.

Explained below with reference to <FIG> is a functional configuration example of the communication device according to the embodiment. <FIG> is a block diagram illustrating a functional configuration example of the communication device. Herein, the communication device either implies the AP <NUM> as well as the STA <NUM>, or implies either one of the AP <NUM> and the STA <NUM>. Moreover, since the AP <NUM> and the STA <NUM> can have an identical functional configuration, the following explanation is given only about the functional configuration of the AP <NUM>, and the explanation of the functional configuration of the STA <NUM> is not given. Furthermore, since the explanation is only exemplary, the AP <NUM> and the STA <NUM> can have different functional configurations. For example, the AP <NUM> can separately have the function of controlling a plurality of STAs <NUM>.

As illustrated in <FIG>, the AP <NUM> includes a communication unit <NUM>, antennas <NUM>, a data processing unit <NUM>, a control unit <NUM>, a memory unit <NUM>, and a power supply unit <NUM>.

The communication unit <NUM> functions as a transmitting unit and a receiving unit; and has the function of transmitting RTS frames, CTS frames, and data frames to other communication devices, and receiving those frames from other communication devices. The communication unit <NUM> according to the embodiment of the application concerned includes amplifier units <NUM>, radio interface units <NUM>, a signal processing unit <NUM>, a channel estimating unit <NUM>, and a modulation/demodulation unit <NUM>. If one amplifier unit <NUM> and one radio interface unit <NUM> are treated as one set, the communication unit <NUM> can include two or more such sets (in the example illustrated in <FIG>, two or more sets are included). Alternatively, the functions of the amplifier units <NUM> can be included in the radio interface units <NUM>.

In the embodiment of the application concerned, the AP <NUM> includes at least two sets of configurations each including the antenna <NUM> along with the amplifier unit <NUM> and the radio interface unit <NUM> of the communication unit <NUM>. Moreover, for example, one set of the antenna <NUM>, the amplifier unit <NUM>, and the radio interface unit <NUM> is treated as the set used in the control channel (a first communication unit), and the other set is treated as the set used in the data channel (a second communication unit). When a communication device performs the RTS/CTS frame exchange with another communication device, the first or second communication units are used by the communication devices for transmitting and receiving RTS frames and CTS frames, dependent on a usage status of the control channel. Moreover, when a communication device transmits data frames to and receives data frames from another communication device, the second communication units are used by the communication devices for transmitting and receiving data frames.

Meanwhile, the communication unit <NUM> need not keep the first communication unit, which is used in the control channel, and the second communication unit, which is used in the data channel, operational on a constant basis; and can keep only one of the first communication unit and the second communication unit operational depending on the operations to be performed.

Each amplifier unit <NUM> performs signal amplification. More particularly, during reception, the amplifier unit <NUM> amplifies the received signals, which are input from the antenna <NUM>, up to a predetermined electrical power; and outputs the amplified signals to the corresponding radio interface unit <NUM> (described later). On the other hand, during transmission, the amplifier unit <NUM> amplifies the transmission signals, which are input from the radio interface unit <NUM>, up to a predetermined electrical power; and outputs the amplified signals to the corresponding antenna <NUM>. Meanwhile, it is alternatively possible to make the radio interface unit <NUM> implement these functions.

During reception, the radio interface unit <NUM> obtains baseband signals by down-converting the received signals, which are analog signals, provided from the corresponding amplifier unit <NUM>; generates reception symbol streams by performing a variety of processing, such as filtering and conversion into digital signals, with respect to the baseband signals; and outputs the reception symbol streams to the signal processing unit <NUM> (described later). On the other hand, during transmission, the radio interface unit <NUM> converts the input from the signal processing unit <NUM> into analog signals; performs filtering and up-conversion to carrier frequency bands; and outputs the processed signals to the amplifier unit <NUM>.

During reception, the signal processing unit <NUM> performs spatial processing with respect to the reception symbol streams provided from each radio interface unit <NUM>; obtains an independent data symbol stream for each reception symbol stream; and provides the data symbol streams to the modulation/demodulation unit <NUM> (described later). On the other hand, during transmission, the signal processing unit <NUM> performs spatial processing with respect to the data symbol streams input from the modulation/demodulation unit <NUM>, and provides one or more obtained transmission symbol streams to each radio interface unit <NUM>.

The channel estimating unit <NUM> calculates complex channel gain information of the propagation channel from the preamble part and the training signal part of the received signals provided from each radio interface unit <NUM>. The calculated complex channel gain information is used in the demodulation operation performed by the modulation/demodulation unit <NUM> and in the spatial processing performed by the signal processing unit <NUM>.

During reception, the modulation/demodulation unit <NUM> obtains received data by performing demodulation, deinterleaving, and decoding with respect to the data symbol streams provided from the signal processing unit <NUM>; and provides the received data to the data processing unit <NUM>. On the other hand, during transmission, with respect to the frames provided from the data processing unit <NUM>, the modulation/demodulation unit <NUM> performs encoding, interleaving, and modulation based on the coding and the modulation method set by the control unit <NUM> (described later), and generates data symbol streams; and provides them to the signal processing unit <NUM>.

Each antenna <NUM> includes one or more antenna elements; and has the function of outputting the received signals from other communication devices to the corresponding amplifier unit <NUM>; and has the function of transmitting the transmission signals, which are input from the corresponding amplifier unit <NUM>, to other communication devices.

During reception, with respect to the received data provided from the modulation/demodulation unit <NUM>, the data processing unit <NUM> has the function of analyzing the MAC header for the purpose of performing media access control (MAC) and has the function of detecting errors in the frames. On the other hand, during transmission, the data processing unit <NUM> generates transmission packets (data); generates transmission frames by performing operations such as adding the MAC header and the error detection code to the generated packets; and provides the transmission frames to the modulation/demodulation unit <NUM>.

Moreover, the data processing unit <NUM> provides the control unit <NUM> with information that, from among the received data, is required in the determination operation and the transmission control operation of the control unit <NUM>. Furthermore, the data processing unit <NUM> provides the memory unit <NUM> with information related to the data written in the RTS frames and the CTS frames.

The control unit <NUM> has the function of controlling the abovementioned constituent elements; and performs operations such as transferring information among the constituent elements, setting parameters, and scheduling operations. For example, the control unit <NUM> sets parameters in the modulation/demodulation unit <NUM> and the signal processing unit <NUM>, and performs scheduling of the packets in the data processing unit <NUM>. Moreover, for example, the control unit <NUM> sets parameters in the radio interface unit <NUM> and the amplifier unit <NUM>, and performs transmission power control.

Furthermore, in the application concerned, the control unit <NUM> performs a determination operation for controlling data communication and, based on the result of the determination operation, controls whether or not to perform transmission and reception of data frames.

In order to implement the functions mentioned above, the control unit <NUM> according to the embodiment of the application concerned includes a determining unit <NUM> and a transmission control unit <NUM> as illustrated in <FIG>.

The determining unit <NUM> has the function of performing a determination operation for controlling data communication. More particularly, based on the result of the RTS/CTS frame exchange performed by the communication unit <NUM> via the control channel, the determining unit <NUM> determines whether or not to make the communication unit <NUM> transmit data frames via the data channel to other communication devices.

For example, the AP <NUM> transmits an RTS frame from the communication unit <NUM> to the STA <NUM> via the control channel. The determining unit <NUM> confirms whether or not a CTS frame is received from the STA <NUM> before the elapse of a predetermined period of time (for example, the SIFS time). If a CTS frame is received from the STA <NUM> before the elapse of the SIFS time, then the determining unit <NUM> determines that the data can be transmitted to the STA <NUM>, and provides the determination result to the transmission control unit <NUM>.

Herein, the SIFS (Short Inter Frame Space) time implies the shortest latency time in the frame transmission interval. Meanwhile, the predetermined period of time is not limited to the SIFS, and can be set to an arbitrary period of time.

Meanwhile, if a CTS frame is not received from the STA <NUM> before the elapse of the SIFS time, then the determining unit <NUM> determines that data frames cannot be transmitted to the STA <NUM>, and provides the determination result to the transmission control unit <NUM>. Moreover, until the determination result is obtained which indicates that data frames can be transmitted to the STA <NUM>, the determining unit <NUM> makes the communication unit <NUM> perform the RTS frame transmission operation, and every time repeats the determination operation.

In the example given above, when the AP <NUM> and the STA <NUM> are successful in the RTS/CTS frame exchange, the AP <NUM> starts transmitting data frames. However, the determination condition for the AP <NUM> to start transmitting data frames is not limited to the example given above. Alternatively, for example, even if a CTS frame is not received before the elapse of the SIFS time since the transmission of the RTS frame, the AP <NUM> can start transmitting data frames. Moreover, even if an RTS frame is not yet received from the AP <NUM>, the STA <NUM> can transmit a CTS frame, in which the data transmission start timing is written, to the AP <NUM>; and thus can specify the data transmission start timing. Meanwhile, the frame used in specifying the data transmission start timing is not limited to an RTS/CTS frame. Alternatively, the STA <NUM> can specify the data transmission start timing using a trigger frame.

The transmission control unit <NUM> has the function of controlling the data communication. More particularly, the transmission control unit <NUM> has the function of controlling the channels to be used for transmitting RTS frames, CTS frames, and data frames. For example, in the embodiment of the application concerned, the transmission control unit <NUM> makes the communication unit <NUM> transmit RTS frames and CTS frames via the control channel, and transmit data frames via the data channel.

Moreover, the transmission control unit <NUM> also has the function of controlling, based on the determination result of the determining unit <NUM>, whether or not to make the communication unit <NUM> transmit data frames. For example, when the determination result is obtained which indicates that data frames are to be transmitted, the transmission control unit <NUM> makes the communication unit <NUM> transmit data frames via the data channel.

The memory unit <NUM> has the function of storing information related to the data obtained by the data processing unit <NUM>. Moreover, when the information related to the data is required in the operations of the control unit <NUM>, the memory unit <NUM> provides the information to the control unit <NUM> via the data processing unit.

The power supply unit <NUM> is configured with a battery power supply or a fixed power supply, and has the function of supplying electrical power to the communication device.

Explained below with reference to <FIG> and <FIG> is an example of the information communicated by the AP <NUM> and the STA <NUM>.

In the embodiment of the application concerned, the information communicated between communication devices is in the form of RTS frames, CTS frames, and data frames. The RTS frames represent, for example, the information transmitted by the AP <NUM> to the STA <NUM> via the control channel. The CTS frames represent the information transmitted by the STA <NUM> to the AP <NUM> via the control channel. The data frames represent the information transmitted by the AP <NUM> to the STA <NUM> via the data channel. Given below is the specific explanation of the configuration of each type of frames.

Explained below with reference to <FIG> is an example of the format of an RTS frame. In the normal configuration of an RTS frame, from among the fields illustrated in <FIG>, for example, the fields "Frame Control", "Duration", "RA", "TA", and "FCS" are included.

An RTS frame according to the embodiment of the application concerned includes a field of additional information related to the data that is normally written in data frames. The additional information corresponds to, for example, the following fields: "Format of Data", "BSS Color of Data", "Spatial Reuse of Data", "Bandwidth of Data", and "Duration of Data". Meanwhile, this frame format is only exemplary. Given below is the explanation of each field of an RTS frame.

The "Frame Control" field includes information related to the type of frame, the transmission direction, and the frame attributes. Herein, the information indicating RTS frame as the type of frame corresponds to transmission request information. The "Duration" field includes information related to the scheduled period of using the radio link. The "RA" field includes information related to the receiving-station MAC address (RA: Receiver Address). The "TA" field includes information related to the transmitting-station MAC address (TA: Transmitter Address).

The "Format of Data" field includes format information. The "BSS Color of Data" field includes BSS identification information. The "Spatial Reuse of Data" field includes spatial reuse information.

The "Bandwidth of Data" field includes bandwidth information. The "Duration of Data" field includes transmission duration information. The "FCS" field is meant for performing error detection in the frame (FCS: Frame Check Sequence).

As a result of having the additional information related to data written in an RTS frame, the communication device at the transmitting side can provide the communication device at the receiving side with the detailed information of the data to be transmitted. Moreover, the transmission information at the receiving side becomes able to know in advance the additional information related to the data, thereby enabling achieving reduction in the overhead in the data frames in the data channel.

Explained below with reference to <FIG> is an example of the format of a CTS frame. In the normal configuration of a CTS frame, from among the fields illustrated in <FIG>, for example, the fields "Frame Control", "RA", and "FCS" are included. In the embodiment of the application concerned, a CTS frame additionally includes a "Transmit Start Time of Data" field and a "Duration of Data" field as the fields of the information related to the data transmission start timing and the data transmission end timing. Meanwhile, this frame format is only exemplary. Given below is the explanation of each field of a CTS frame.

The "Frame Control" field includes information related to the type of frame, the transmission control, and the frame attributes. Herein, the information indicating CTS frame as the type of frame corresponds to transmission permission information. The "RA" field includes information related to the receiving-station MAC address (RA: Receiver Address).

The "Transmit Start Time of Data" field includes information related to the data transmission start timing. The "Duration of Data" field includes information related to the data transmission period. The "FCS" field is meant for performing error detection in the frame (FCS: Frame Check Sequence). Meanwhile, the data transmission end timing can be calculated from the data transmission start timing and the data transmission period.

A data frame is a frame including the data transmitted and received by communication devices, and including additional information related to the data. In the embodiment of the application concerned, the additional information is not written in a data frame, but is written in an RTS frame. The specific fields of the additional information are same as the details explained above in (<NUM>) RTS frame. Thus, that explanation is not given again so as to avoid repetition. Although the additional information written in RTS frames is not written in data frames; the AP <NUM> writes, in the data frames, a "Training" field that required in the demodulation of the data frames received by the STA <NUM>, and then transmits the data frames.

Meanwhile, the frames in which additional information related to the data is written are not limited to RTS frames, and alternatively the additional information can be written in arbitrary frames. For example, additional information related to the data can be written in CTS frames. If additional information related to the data is written in CTS frames, the communication device at the receiving side becomes able to instruct the communication device at the transmitting side to transmit the data specified in the additional information.

Explained above with reference to <FIG> and <FIG> is an example of the information communicated between the AP <NUM> and the STA <NUM> according to the embodiment of the application concerned. Given below is the explanation of an operation example of the communication system according to the embodiment of the application concerned.

The explanation is given about an operation example of the communication system according to the embodiment of the application concerned. Explained below with reference to <FIG> is an operation example of the communication system.

Explained below with reference to <FIG> is an overall operation example of the communication system according to the embodiment of the application concerned. <FIG> is a sequence diagram illustrating the operation example of the communication system. In the embodiment of the application concerned, the operation for acquiring the data frame transmission right, which is required in the determination operation for controlling the communication of data frames, is performed using only the control channel. According to the independent claims, this is the case when usage status of the control channel allows for it. Moreover, the operation of communicating data frames is assumed to be performed using only the data channel.

As illustrated in <FIG>, firstly, after the elapse of a back-off period <NUM>, the AP 100A transmits an RTS frame <NUM> to the STA 200A via the control channel (a timing T<NUM>). Upon receiving the RTS frame <NUM>, the STA 200A transmits a CTS frame <NUM> to the AP 100A and the STA 200A via the control channel (a timing T<NUM>).

At that time, since the AP 100B is using the data channel for transmitting Data <NUM>, the AP 100A and the STA 200A cannot use the data channel. Hence, the STA 200A writes, as the transmission start time in the "Transmit Start Time of Data" field of the CTS frame, information about a timing T<NUM> at which the AP 100B would complete the transmission of data frames via the data channel; and transmits the CTS frame via the control channel. This transmission start time represents the information intended for the AP 100A that is scheduled next to transmit data frames.

Moreover, the STA 200A also writes, in the "Duration of Data" field of the CTS frame, the transmission duration information written in the "Duration of Data" field of the RTS frame received via the control channel from the AP 100A. The transmission duration information represents the information intended for the STA 200B that is likely to receive the data frames after the STA 200A. For example, assume that the STA 200B receives an RTS frame from the AP 100B while the STA 200A is receiving data frames. Then, the STA 200B can write the transmission duration information, which was written in the CTS frame received earlier from the STA 200A, in the "Duration of Data" field of a CTS frame, and transmit that CTS frame to the AP 100B.

After the AP 100B has completed the transmission of the Data <NUM> via the data channel (the timing T<NUM>), the AP 100A starts transmitting Data <NUM> to the STA 200A via the data channel (the timing T<NUM>). After the elapse of a back-off period <NUM> since the completion of transmission of the Data <NUM>, the AP 100B sends an RTS frame <NUM> to the STA 200B via the control channel for the purpose of again transmitting data frames (a timing T<NUM>). Upon receiving the RTS frame <NUM> via the control channel; the STA 200A writes, in a CTS frame <NUM>, information that is identical to the information written when the STA 200A transmitted the CTS frame <NUM> via the control channel, and transmits the CTS frame <NUM> to the AP 100B and the STA 200A via the control channel (a timing T<NUM>). Subsequently, after the AP 100A has completed the transmission of the Data <NUM> via the data channel (a timing T<NUM>), the AP 100B transmits Data <NUM> to the STA 200B via the data channel (the timing T<NUM> to a timing T<NUM>).

Explained below with reference to <FIG> is the specific RTS/CTS frame exchange operation performed in the communication device at the data frame transmitting side. In the following explanation, for example, the AP <NUM> is assumed to be the communication device at the transmitting side, and the STA <NUM> is assumed to be the communication device at the receiving side. Firstly, before starting the data frame transmission operation, the AP <NUM> transmits an RTS frame to the STA 200A via the control channel (Step S1000). After transmitting the RTS frame, the AP <NUM> confirms whether or not a CTS frame is received via the control channel before the elapse of the SIFS period (Step S1004). If a CTS frame is received (Yes at Step S1004), then the AP <NUM> transmits data frames to the STA <NUM> via the data channel at the transmission start timing written in the received CTS frame (Step S1008). On the other hand, if a CTS frame is not received (No at Step S1004), then the AP <NUM> repeatedly performs the operation of transmitting an RTS frame via the control channel and the determination operation until a CTS frame is received.

Explained below with reference to <FIG> is the specific RTS/CTS frame exchange operation performed in the communication device at the data frame receiving side. In the following example, for example, in an identical manner to the explanation with reference to <FIG>, the STA <NUM> is assumed to be the communication device at the receiving side, and the AP <NUM> is assumed to be the communication device at the transmitting side. Firstly, the STA <NUM> receives an RTS frame via the control channel (Step S1100). Then, the STA <NUM> stores, in the memory unit <NUM>, the additional information related to the data as written in the received RTS frame (Step S1104). Subsequently, the STA <NUM> confirms whether the data frames that are already reserved for transmission are present in the data channel (Step S1108). Then, the STA <NUM> decides, as the transmission start timing for transmitting data frames, the timing at which the transmission of all data frames already reserved for transmission is completed (Step S1112). After deciding on the transmission start timing, the STA <NUM> writes, in a CTS frame, the transmission start timing representing the timing at which the AP <NUM> would start transmitting data frames via the data channel (Step S1116), and transmits the CTS frame to the AP <NUM> via the control channel (Step S1120).

Till now, the embodiment of the application concerned was explained with reference to <FIG>. Given below is the explanation of a modification example of the embodiment of the application concerned.

Given below is the explanation of the modification example of the embodiment of the application concerned. The modification example explained below can be applied, either individually or in combination, in the embodiment of the application concerned. Moreover, the modification example can be applied as a substitute to or in addition to the configuration explained in the embodiment of the application concerned.

In the embodiment of the application concerned, the explanation was given for the example in which the operation of acquiring the data frame transmission right is performed using the control channel. However, and according to the appended independent claims, the operation of acquiring the data frame transmission right can be performed using the data channel according to a different method than the method for performing the operation using the control channel. For example, before starting the transmission of data frames, the AP <NUM> confirms the usage status of the data channel and the control channel. Then, according to the usage status of each channel, the AP <NUM> can select the channel to be used and perform the operation of acquiring the data frame transmission right according to the method corresponding to the selected channel. Explained below with reference to <FIG> and <FIG> is an example of specific operations.

Firstly, explained with reference to <FIG> is an example of specific operations performed in the communication system according to the modification example. Firstly, before transmitting data frames to the STA 200A, the AP 100A confirms the usage status of the data channel and the control channel. Since the confirmation result indicates that the data channel not in use, the AP 100A attempts to acquire the data frame transmission right in the data channel by performing back-off control <NUM> (a timing T<NUM>). If the data frame transmission right is acquired as a result of the back-off control <NUM>, the AP 100A transmits Data <NUM> to the STA 200A via the data channel (a timing T<NUM> to a timing T<NUM>). Meanwhile, when the data channel transmission right is acquired, the AP <NUM> and the STA 200A does not perform the RTS/CTS frame exchange, and thus the AP <NUM> does not send the additional information to the STA 200A. Hence, the AP <NUM> can write the additional information in the data frames.

While the AP 100A is transmitting the data frames via the data channel; with the aim of attempting transmission of data frames, the AP 100B confirms the usage status of the data channel and the control channel before starting transmission of data frames. The confirmation result enables the AP 100B to know that the data channel is being used by some other communication device. At the same time, the AP 100B gets to know that the control channel is not in use and, after the elapse of a back-off period <NUM>, transmits an RTS frame <NUM> to the STA 200B via the control channel (the timing T<NUM>). Then, based on the information written in the received RTS frame <NUM>, the STA 200B transmits a CTS frame <NUM> to the AP 100B via the control channel (the timing T<NUM>). Based on the information written in the received CTS frame <NUM>, after the AP 100A has completed the transmission of the Data <NUM> via the data channel (the timing T<NUM>), the AP 100B transmits Data <NUM> to the STA 200B via the data channel (the timing T<NUM> to a timing T<NUM>).

Explained below with reference to <FIG> is the specific data transmission operation performed in the communication device at the data frame transmitting side according to the modification example. In the following example, for example, the AP <NUM> is assumed to be the communication device at the transmitting side. Firstly, before starting the data frame transmission operation, the AP <NUM> confirms the usage status of the data channel and the control channel (Step S2000). If the data channel is not in use (Yes at Step S2004), then the AP <NUM> acquires the data frame transmission right in the data channel by performing back-off control (Step S2008). After acquiring the data frame transmission right, the AP <NUM> transmits data frames in the data channel (Step S2012).

Meanwhile, if the data channel is in use (No at Step S2004), the AP <NUM> confirms the usage status of the control channel (Step S2016). If the control channel is not in use (Yes at Step S2016), then the AP <NUM> transmits an RTS frame via the control channel (Step S2020). Subsequently, before the elapse of the SIFS period since the transmission of the RTS frame, if a CTS frame is received via the control channel (Yes at Step S2024); then the AP <NUM> transmits data frames. More particularly, the AP <NUM> transmits data frames via the data channel at the transmission start timing written in the received CTS frame (Step S2028). On the other hand, before the elapse of the SIFS period since the transmission of the RTS frame, if a CTS frame is not received via the control channel (No at Step S2024); then the AP <NUM> again transmits an RTS frame via the control channel (Step S2020).

If the control channel too is in use (No at Step S2016), then the AP <NUM> waits until either the data channel or the control channel is no more in use (Step S2032).

This example is not covered by the independent claims.

The operation example of the communication device at the data frame transmitting side according to the modification example is identical to the operation example of the communication device at the data frame transmitting side, and the explanation thereof is not given so as to avoid repetition.

Till now, the explanation with reference to <FIG> and <FIG> was given about the modification example of the application concerned. Given below is the explanation of the application examples according to the embodiment of the application concerned.

The technology according to the application concerned is applicable in various products. For example, each STA <NUM> can be implemented as a mobile device such as a smartphone, a tablet PC (Personal Computer), a note PC, a portable game terminal, or a digital camera; or can be implemented as a fixed terminal such as a television receiver, a printer, a digital scanner, or a network storage; or can be implemented as an in-vehicle terminal such as a car navigation device. Alternatively, the STAs <NUM> can be implemented as terminals performing M2M (Machine To Machine) communication (also called MTC (Machine Type Communication) terminals), such as smart meters, automatic vending machines, remote supervision devices, or POS (Point Of Sale) terminals. Still alternatively, the STAs <NUM> can be radio communication modules (for example, integrated circuit modules configured using a single die) installed on such terminals.

On the other hand, for example, each AP <NUM> can be implemented as a wireless LAN access point (also called a wireless base station) that may or may not have the routing function. Alternatively, the APs <NUM> can be implemented as mobile wireless LAN routers. Still alternatively, the APs <NUM> can be radio communication modules (for example, integrated circuit modules configured using a single die) installed on such devices.

<FIG> is a block diagram illustrating an example of a schematic configuration of a smartphone <NUM> in which the technology disclosed in the application concerned is applicable. The smartphone <NUM> includes a processor <NUM>, a memory <NUM>, a storage <NUM>, an external connection interface <NUM>, a camera <NUM>, a sensor <NUM>, a microphone <NUM>, an input device <NUM>, a display device <NUM>, a speaker <NUM>, a radio communication interface <NUM>, an antenna switch <NUM>, an antenna <NUM>, a bus <NUM>, a battery <NUM>, and an auxiliary controller <NUM>.

The processor <NUM> can be, for example, a CPU (Central Processing Unit) or an SoC (System on Chip), and controls the functions of the application layer and the other layers of the smartphone <NUM>. The memory <NUM> includes a RAM (Random Access Memory) and a ROM (Read Only Memory), and is used to store the programs executed by the processor <NUM> and to store data. The storage <NUM> can include a memory medium such as a semiconductor memory or a hard disk. The external connection interface <NUM> is an interface for connecting an external device, such as a memory card or a USB (Universal Serial Bus) device, to the smartphone <NUM>.

The camera <NUM> includes an imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and generates captured images. The sensor <NUM> can include a group of sensors such as a positioning sensor, a gyro sensor, a geomagnetic sensor, and an acceleration sensor. The microphone <NUM> converts the sound input to the smartphone <NUM> into sound signals. The input device <NUM> includes, for example, a touch sensor for detecting a touch on the screen of the display device <NUM>, or a keypad, or a keyboard, or buttons or switches; and receives operations and information input from the user. The display device <NUM> has a screen such as a liquid crystal display (LCD) or an organic light emitting diode (OLED) display, and displays output images of the smartphone <NUM>. The speaker <NUM> converts the sound signals, which are output from the smartphone <NUM>, into sound.

The radio communication interface <NUM> supports one or more wireless LAN standards such as the IEEE802.11a standard, the IEEE802.11b standard, the IEEE802. <NUM> standard, the IEEE802.11n standard, the IEEE802.11ac standard, and the IEEE802.11ad standard; and implements radio communication. In the infrastructure mode, the radio communication interface <NUM> can perform communication with other devices via wireless LAN access points. Moreover, in a direct communication mode such as the ad hoc mode or the Wi-Fi Direct (registered trademark), the radio communication interface <NUM> can directly perform communication with other devices. Moreover, in the Wi-Fi Direct, unlike in the ad hoc mode, although one of the two terminals functions as an access point, the communication between those two terminals is performed in a direct manner. Typically, the radio communication interface <NUM> can include a baseband processor, an RF (Radio Frequency) circuit, and a power amplifier. Meanwhile, the radio communication interface <NUM> can be a one-chip module in which a memory for storing a communication control program, a processor for executing that program, and related circuits are integrated. Moreover, in addition to supporting the wireless LAN method, the radio communication interface <NUM> can also support other types of radio communication methods such as the near field communication method, the proximity radio communication method, and the cellular communication method. The antenna switch <NUM> switches the connection destinations of the antenna <NUM> among a plurality of circuits included in the radio communication interface <NUM> (for example, the circuits meant for different radio communication methods). The antenna <NUM> includes one or more antenna elements (for example, a plurality of antenna elements constituting a MIMO antenna), and is used by the radio communication interface <NUM> in transmitting and receiving radio signals.

Meanwhile, the smartphone <NUM> is not limited to have the configuration illustrated in the example in <FIG>, and can alternatively include a plurality of antennas (for example, an antenna for the wireless LAN and an antenna for the proximity radio communication method). In that case, the antenna switch <NUM> can be omitted from the configuration of the smartphone <NUM>.

The bus <NUM> connects the processor <NUM>, the memory <NUM>, the storage <NUM>, the external connection interface <NUM>, the camera <NUM>, the sensor <NUM>, the microphone <NUM>, the input device <NUM>, the display device <NUM>, the speaker <NUM>, the radio communication interface <NUM>, and the auxiliary controller <NUM> to each other. The battery <NUM> supplies electrical power to each block of the smartphone <NUM>, which is illustrated in <FIG>, via a power supply line that is partially illustrated in <FIG> using dashed lines. The auxiliary controller <NUM> implements the minimum required functions of the smartphone <NUM> in, for example, the sleep mode.

Meanwhile, in the smartphone <NUM>, the processor <NUM> can execute the access point function at the application level, so that the smartphone <NUM> can operate as a wireless access point (software AP). Moreover, the radio communication interface <NUM> can also have the wireless access point function.

<FIG> is a block diagram illustrating an example of a schematic configuration of a car navigation device <NUM> in which the technology disclosed in the application concerned is applicable. The car navigation device <NUM> includes a processor <NUM>, a memory <NUM>, a GPS (Global Positioning System) module <NUM>, a sensor <NUM>, a data interface <NUM>, a content player <NUM>, a memory medium interface <NUM>, an input device <NUM>, a display device <NUM>, a speaker <NUM>, a radio communication interface <NUM>, an antenna switch <NUM>, an antenna <NUM>, and a battery <NUM>.

The processor <NUM> can be, for example, a CPU or an SoC, and controls the navigation function and the other functions of the car navigation device <NUM>. The memory <NUM> includes a RAM and a ROM, and is used to store the programs executed by the processor <NUM> and to store data.

The GPS module <NUM> uses GPS signals received from GPS satellites, and measures the location (for example, the latitude, the longitude, and the altitude) of the car navigation device <NUM>. The sensor <NUM> can include a group of sensors such as a gyro sensor, a geomagnetic sensor, and a pressure sensor. The data interface <NUM> is connected to, for example, an in-vehicle network <NUM> via a terminal (not illustrated), and obtains data such as vehicle speed data generated in the vehicle.

The content player <NUM> reproduces the contents stored in a memory medium (such as a CD or a DVD) that is inserted in the memory medium interface <NUM>. The input device <NUM> includes a touch sensor for detecting a touch on the screen of the display device <NUM>, or includes buttons, or includes switches; and receives operations and information input from the user. The display device <NUM> has a screen such as an LCD or an OLED display, and displays the navigation functions or images of the reproduced contents. The speaker <NUM> converts the sounds of the navigation functions or the sounds of the reproduced contents.

The radio communication interface <NUM> supports one or more wireless LAN standards such as the IEEE802.11a standard, the IEEE802.11b standard, the IEEE802. <NUM> standard, the IEEE802.11n standard, the IEEE802.11ac standard, and the IEEE802.11ad standard; and implements radio communication. In the infrastructure mode, the radio communication interface <NUM> can perform communication with other devices via wireless LAN access points. Moreover, in a direct communication mode such as the ad hoc mode or the Wi-Fi Direct, the radio communication interface <NUM> can directly perform communication with other devices. Typically, the radio communication interface <NUM> can include a baseband processor, an RF circuit, and a power amplifier. Meanwhile, the radio communication interface <NUM> can be a one-chip module in which a memory for storing a communication control program, a processor for executing that program, and related circuits are integrated. Moreover, in addition to supporting the wireless LAN method, the radio communication interface <NUM> can also support other types of radio communication methods such as the near field communication method, the proximity radio communication method, and the cellular communication method. The antenna switch <NUM> switches the connection destinations of the antenna <NUM> among a plurality of circuits included in the radio communication interface <NUM>. The antenna <NUM> includes one or more antenna elements, and is used by the radio communication interface <NUM> in transmitting and receiving radio signals.

Meanwhile, the car navigation device <NUM> is not limited to have the configuration illustrated in the example in <FIG>, and can alternatively include a plurality of antennas. In that case, the antenna switch <NUM> can be omitted from the configuration of the car navigation device <NUM>.

The battery <NUM> supplies electrical power to each block of the car navigation device <NUM>, which is illustrated in <FIG>, via a power supply line that is partially illustrated in <FIG> using dashed lines. Moreover, the battery <NUM> stores the electrical power supplied from the vehicle.

Meanwhile, the radio communication interface <NUM> can operate as the AP <NUM>, and can provide wireless connection to the terminal of the user who is riding in the vehicle.

Moreover, the technology disclosed in the application concerned can be implemented as an in-vehicle system (or a vehicle) <NUM> that includes one or more blocks of the car navigation device <NUM>; the in-vehicle network <NUM>; and a vehicle-side module <NUM>. The vehicle-side module <NUM> generates vehicle data such as the vehicle speed, the engine rotation count, and breakdown information; and outputs the generated data to the in-vehicle network <NUM>.

<FIG> is a block diagram illustrating an example of a schematic configuration of a wireless access point <NUM> in which the technology disclosed in the application concerned is applicable. The wireless access point <NUM> includes a controller <NUM>, a memory <NUM>, an input device <NUM>, a display device <NUM>, a network interface <NUM>, a radio communication interface <NUM>, an antenna switch <NUM>, and an antenna <NUM>.

The controller <NUM> can be, for example, a CPU or a DSP (Digital Signal Processor), and implements various functions (for example, access restriction, routing, encryption, firewall, and log management) of the IP (Internet Protocol) layer and the still higher-level layers. The memory <NUM> includes a RAM and a ROM, and is used to store the programs executed by the controller <NUM> and to store a variety of control data (for example, a terminal list, a routing table, an encryption key, security setting, and a log).

The input device <NUM> includes, for example, buttons or switches, and receives operations from the user. The display device <NUM> includes an LED lamp, and displays the operation status of the wireless access point <NUM>.

The network interface <NUM> is a wired communication interface meant for enabling the wireless access point <NUM> to get connected to a wired communication network <NUM>. The network interface <NUM> can include a plurality of connection terminals. The wired communication network <NUM> can be a LAN such as Ethernet (registered trademark), or can be a WAN (Wide Area Network).

The radio communication interface <NUM> supports one or more wireless LAN standards such as the IEEE802.11a standard, the IEEE802.11b standard, the IEEE802. <NUM> standard, the IEEE802.11n standard, the IEEE802.11ac standard, and the IEEE802.11ad standard; and provides wireless connection as an access point to nearby terminals. Typically, the radio communication interface <NUM> can include a baseband processor, an RF circuit, and a power amplifier. Meanwhile, the radio communication interface <NUM> can be a one-chip module in which a memory for storing a communication control program, a processor for executing that program, and related circuits are integrated. The antenna switch <NUM> switches the connection destinations of the antenna <NUM> among a plurality of circuits included in the radio communication interface <NUM>. The antenna <NUM> includes one or more antenna elements, and is used by the radio communication interface <NUM> in transmitting and receiving radio signals.

As described above, the communication devices according to the application concerned can perform the RTS/CTS frame exchange via the control channel, and can communicate data frames via the data channel that has a different frequency band than the control channel. As a result, it is possible to provide a communication device, a program, and a communication method in a new and improved form for enabling radio communication in a more efficient manner.

Although the application concerned is described above in detail in the form of a preferred embodiment with reference to the accompanying drawings; the technical scope of the application concerned is not limited to the embodiment described above.

Meanwhile, the series of operations performed by each device described in the present written description can be implemented using either software, or hardware, or a combination of software and hardware. The computer programs constituting software are, for example, stored in advance in the concerned device or in an external recording medium (non-transitory media). Then, for example, during execution in the computer, each program is read into the RAM and is executed by the processor such as the CPU.

Claim 1:
A communication device (<NUM>) comprising:
a first communication unit (<NUM>) adapted to perform frame exchange with another communication device (<NUM>) using either a control channel or a data channel within a wireless LAN communication system dependent on a usage status of the control channel;
a second communication unit (<NUM>) adapted to perform communication of a data frame with the other communication device using the data channel, wherein the data channel has a different frequency band and a different bandwidth than the control channel; and
a control unit (<NUM>) adapted to control communication of the data frame based on result of the frame exchange.