JP5731366B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method.

  In recent years, the IEEE802.11g standard, the IEEE802.11a standard, and the like are remarkable as high-speed wireless access systems using the 2.4 GHz band or the 5 GHz band. These systems use an Orthogonal Frequency Division Multiplexing (OFDM) modulation method, which is a technique for stabilizing characteristics in a multipath fading environment, and realize a physical layer transmission rate of 54 Mbps at the maximum. (For example, refer nonpatent literature 1).

  However, the transmission rate here is the transmission rate on the physical layer, and the transmission efficiency in the MAC (Medium Access Control) layer is actually about 50 to 70%, so the upper limit of the actual throughput is 30 Mbps. If the number of communication stations that intend to transmit information increases, this characteristic further deteriorates. On the other hand, in a wired LAN (Local Area Network), a 100 Mbps high-speed line has been introduced due to the widespread use of FTTH (Fiber to the home) using an optical fiber in each home, including the Ethernet (registered trademark) 100Base-T interface. Provision is widespread, and further increase in transmission speed is demanded in wireless LAN.

  As a technique for this purpose, a MIMO (Multiple Input Multiple Output) technique has been introduced as a spatial multiplexing transmission technique in the IEEE 802.11n standard. Furthermore, in IEEE802.11ac, a multi-user MIMO (MU-MIMO) transmission method to which space division multiple access (SDMA) is applied has been studied (for example, see Non-Patent Document 2).

  In the wireless LAN system compliant with IEEE802.11, each communication station adopts an access control procedure based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance), and each communication station detects a signal collision with another communication station. To avoid. A communication station that has made a transmission request first monitors the state of the wireless medium for a predetermined sensing period (DIFS: Distributed Inter-Frame Space), and if there is no transmission signal from another communication station during this period, a random back Do off. The communication station continues to monitor the wireless medium during the random back-off period, but when there is no transmission signal from another communication station during this period, the exclusive channel transmission right (TXOP) for a predetermined period of time. Get Transmission Opportunity). A communication station that has obtained a transmission right (TXOP) in this way is called a TXOP Holder (hereinafter referred to as a transmission right acquisition communication station). The communication station that has become the transmission right acquisition communication station can continuously transmit frames without performing CSMA / CA again within the TXOP period.

  As a method for solving the hidden terminal problem in wireless communication, “virtual carrier sense” can be cited. Specifically, when the communication station includes Duration (sustained use period) information for reserving a wireless medium in a received frame that is not addressed to the local station, the communication station is in the medium for the period corresponding to the Duration information. Is used (virtual carrier sense), and this period is set as a transmission stop period (NAV: Network Allocation Vector), so that frames are not transmitted during the NAV period. This guarantees exclusive use of the channel during the TXOP period.

  When the communication station receives the frame, the NAV is set as necessary as described above. At the same time, if the received frame is a frame that starts the TXOP period, the transmission source communication station of the received frame, a so-called transmission right acquisition communication station Is recorded (for example, non-patent document 3). When the TXOP period ends, the stored information for identifying the transmission right acquisition communication station is deleted. The frame that starts the TXOP period is not a special frame but a signal that reserves a channel for a certain period by transmitting the frame, such as an RTS (Request To Send) frame. . Therefore, information indicating that the TXOP period is explicitly started by the frame is not included.

When the communication station receives the frame again within the TXOP period, it checks whether the transmission source address of the received frame is the same as the MAC address stored as information for identifying the transmission right acquisition communication station. If they are the same, it is determined that the transmission source communication station of the received frame is a transmission right acquisition communication station, and a necessary reply frame is transmitted regardless of whether or not the NAV is set in the own station. As a result, the transmission right acquisition communication station can transmit and receive data to and from a plurality of different communication stations within the same TXOP period.
Hereinafter, an example of frame transmission / reception performed between communication stations will be described with reference to FIGS. 14 and 15.

  FIG. 14 is a time chart showing an example of the timing of transmitting a frame when the transmission right acquisition communication station transmits a plurality of data frames addressed to other communication stations in TXOP. In the figure, the horizontal axis indicates time. Here, a base station device AP (Access Point) 9 and wireless terminals WT (Wireless Terminal) 91 to WT93 are communication stations, and the base station device AP9 accommodates data addressed to the wireless terminals WT91 to WT93, and the wireless terminal WT91. In the example, data frames addressed to WT93 are transmitted within the same TXOP period. Base station apparatus AP9 acquires TXOP and first transmits data to wireless terminal WT91. When the base station apparatus AP9 finishes data communication with the wireless terminal WT91, it transmits data to the wireless terminal WT92, and finally transmits data to the wireless terminal WT93.

Hereinafter, operations of the base station device AP9 and the wireless terminals WT91 to WT93 will be described.
First, the base station apparatus AP9 performs CSMA / CA when data addressed to the wireless terminals WT91 to WT93 occurs, and detects a signal transmitted from another communication station over a predetermined sensing period and a random backoff time. Confirm that the transmission is not performed, and acquire the transmission right (TXOP). Since the base station apparatus AP9 has acquired the transmission right, it becomes a transmission right acquisition communication station (TXOP Holder) and transmits the frame. The base station device AP9 transmits an RTS frame as a start frame indicating the start of the frame sequence to the wireless terminal WT91 (time t ₉₁₁ ).
The wireless terminal WT91 returns a CTS (Clear To Send: transmission permission) frame to the base station apparatus AP9 because the destination of the received RTS frame is the local station and the transmission stop period is not set in the local station. (Time t ₉₁₂ ). As a result, the wireless terminal WT91 notifies the base station apparatus AP9 that it can receive data.
On the other hand, since the wireless terminal WT92 and the wireless terminal WT93, which are other communication stations that have received the RTS frame from the base station device AP9, are not addressed to the local station, the period indicated by the sustained use period information included in the RTS frame Is set to the NAV period (transmission stop period), and the frame is not transmitted within the corresponding NAV period. In addition, when the RTS frame is received from the base station apparatus AP9, it is detected that the TXOP period (utilization transmission right period) is started, and the wireless terminals WT91 to WT93 are connected to the transmission right acquisition communication station by the base station apparatus AP9. I remember that.
The base station apparatus AP9 receives the CTS frame from the wireless terminal WT91, transmits a data frame addressed to the wireless terminal WT91 (time _{t 913).}
When the wireless terminal WT91 correctly receives the data frame addressed to itself, the wireless terminal WT91 returns a BA (Block ACK) frame (or ACK (Acknowledgement) frame) to the base station device AP9 (time t ₉₁₄ ), Finish sending and receiving.

Then, the base station apparatus AP9, for sending data to the radio terminal WT92, transmits an RTS frame in which the destination wireless terminal WT92 (time _{t 915).} Here, since the wireless terminal WT92 has received the RTS frame from the base station apparatus AP9 which is a transmission right acquisition communication station, the wireless terminal WT92 returns a CTS frame to the transmission right acquisition communication station regardless of whether or not it is within the NAV period. (Time t ₉₁₆ ).
Since the wireless terminal WT91 and the wireless terminal WT93 have received the RTS frame that is not addressed to themselves, they set the NAV period. If the NAV period has already been set, the NAV value is updated.
When the base station apparatus AP9 correctly receives the CTS frame from the wireless terminal WT92, the base station apparatus AP9 transmits a data frame addressed to the wireless terminal WT92 (time t ₉₁₇ ).
When the wireless terminal WT92 correctly receives the data frame from the base station device AP9, the wireless terminal WT92 returns a BA frame (or ACK frame) to the base station device AP9 (time t ₉₁₈ ), and ends transmission / reception of the frame.

Next, in order to transmit data addressed to the wireless terminal WT93, the base station device AP9 transmits an RTS frame whose destination is the wireless terminal WT93 (time t ₉₁₉ ). Here, since the wireless terminal WT93 has received the RTS frame from the base station apparatus AP9 which is the transmission right acquisition communication station, the wireless terminal WT93 returns the CTS frame to the transmission right acquisition communication station regardless of whether or not it is within the NAV period. (Time t ₉₂₀ ).
On the other hand, since the wireless terminal WT91 and the wireless terminal WT92 have received the RTS frame that is not addressed to themselves, they set the NAV period. If the NAV period has already been set, the NAV value is updated.
The base station apparatus AP9 receives correctly a CTS frame from the wireless terminal WT93, transmits a data frame addressed to the wireless terminal WT93 (time _{t 921).}
When the wireless terminal WT93 correctly receives the data frame from the base station device AP9, the wireless terminal WT93 returns a BA frame (or ACK frame) to the base station device AP9 (time t ₉₂₂ ), and finishes transmission / reception of the frame.

  In IEEE 802.11n, an RD (Reverse Direction) protocol is introduced in order to further improve the efficiency of data transmission in TXOP. In the conventional technique, only one-way data transmission is performed in which the communication station that has acquired the TXOP transmits a data frame and receives a reply frame in response thereto. On the other hand, in the RD protocol, the communication station that acquired the TXOP permits “RDG (RD Grant) = 1” in a specific field in the MAC frame when transmitting data, that is, permits data transmission in the reverse direction. By transmitting information indicating that (reverse direction permission information), the data receiving station transmits a data frame in the reverse direction destined to the communication station (TXOP holder) that acquired the TXOP within the same TXOP. (For example, refer nonpatent literature 4).

FIG. 15 is a time chart showing an example of a frame when data transmission / reception is performed bidirectionally by applying the RD protocol in IEEE802.11n. In the figure, the horizontal axis indicates time. Here, an example is shown in which base station apparatus AP9 and wireless terminals WT91 to WT93 are communication stations, and base station apparatus AP9 mutually transmits and receives data with wireless terminal WT91 and wireless terminal WT93.
The base station apparatus AP9 is addressed to the wireless terminal WT91 obtains the transmission right transmits the RTS frame as a start frame (time _{t 931),} receives the CTS frame from the wireless terminal WT91 (time _{t 932),} the wireless terminal WT91 A data frame is transmitted to the address (time t ₉₃₃ ). At this time, base station apparatus AP9 notifies wireless terminal WT91 that transmission in RD (reverse direction) is possible by setting “1” in the RDG field in the MAC header included in the data frame. .
When receiving the data frame including the MAC header in which “1” is set in the RDG field, the wireless terminal WT91 detects that data can be transmitted to the base station device AP9, and sets “1” in the RDG field. The returned BA frame is returned (time t ₉₃₄ ). Thereby, the wireless terminal WT91 notifies the base station apparatus AP9 that there is data to be transmitted by RD.
Then, the wireless terminal WT91 transmits a data frame to the base station apparatus AP9 after SIFS (Short Inter-frame space) (time t ₉₃₅ ). Note that the wireless terminal WT 91 sets the RDG field in the MAC header included in the data frame to be transmitted to “0” to indicate that it is the last data frame to be transmitted, the base station that is the transmission right acquisition communication station The device AP9 is notified. The base station apparatus AP9 receives the data frame from the wireless terminal WT91, returns a BA frame (or ACK frame) to the wireless terminal WT91 (time _{t 936),} completing the communication with the radio terminal WT91.

Next, the base station device AP9 transmits an RTS frame whose destination is the wireless terminal WT93 (time t ₉₃₇ ). Here, since the wireless terminal WT93 has received the RTS frame from the base station apparatus AP9 that is the transmission right acquisition communication station, the wireless terminal WT93 returns the CTS frame to the transmission right acquisition communication station regardless of whether it is the NAV period (time). t ₉₃₈ ).
On the other hand, since the wireless terminal WT91 and the wireless terminal WT92 have received the RTS frame that is not addressed to themselves, they set the NAV period. If the NAV period is already set, the NVA period is updated.
The base station apparatus AP9 receives correctly a CTS frame from the wireless terminal WT93, transmits a data frame addressed to the wireless terminal WT93 (time _{t 939).} Here, the base station apparatus AP9 sets to “1” in the RDG field included in the transmitted data frame to indicate to the wireless terminal WT93 that transmission to the wireless terminal WT93 is possible in the reverse direction (RD). Notice.
When receiving the data frame in which “1” is set in the RDG field from the base station device AP9, the wireless terminal WT93 transmits the data frame together with the BA frame to the base station device AP9 (time t ₉₄₀ ).
When the base station apparatus AP9 correctly receives the data frame in which “0” is set in the RDG field from the wireless terminal WT93, the base station apparatus AP9 transmits a BA frame to the wireless terminal WT93 (time t ₉₄₁ ), and End communication.

Masahiro Morikura, supervised by Shuji Kubota, “802.11 High-Speed Wireless LAN Textbook”, revised third edition, Impress R & D Inc., April 11, 2008 IEEE, "Proposed specification framework for TGac," doc .: IEEE 802.11-09 / 0992r21, Jan. 2011. IEEE, "IEEE Std 802.11-2007" IEEE, "IEEE Std 802.11n-2009"

  Each communication station detects the communication station that started the frame sequence, that is, the so-called transmission right acquisition communication station, by correctly receiving the start frame of the frame sequence as in the examples shown in FIGS. Can be remembered. However, not all communication stations may be able to correctly receive the start frame of the frame sequence. Hereinafter, an example in which the start frame cannot be correctly received will be described with reference to FIGS. 16 and 17.

FIG. 16 is a time chart showing an example in which the wireless terminal WT93 cannot correctly receive the start frame. In the figure, the horizontal axis indicates time. Here, similarly to the example shown in FIG. 14, base station apparatus AP9 and wireless terminals WT91 to WT93 are communication stations, and base station apparatus AP9 accommodates data addressed to wireless terminals WT91 to WT93, and wireless terminal WT91. In this example, data frames addressed to WT93 are transmitted within the same TXOP. However, a case will be described in which radio terminal WT93 receives interference from a communication station (interference station) in an adjacent cell until time t ₉₅₄ and cannot correctly receive a signal from base station apparatus AP9.

First, the base station apparatus AP9 performs CSMA / CA when data addressed to the wireless terminals WT91 to WT93 occurs, and detects a signal transmitted from another communication station over a predetermined sensing period and a random backoff time. Confirm that the request is not made and acquire the transmission right. Since the base station apparatus AP9 has acquired the transmission right, it becomes a transmission right acquisition communication station and transmits a frame. The base station device AP9 transmits an RTS frame as a start frame to the wireless terminal WT91 (time t ₉₅₁ ).
At this time, when the radio terminal WT92 receives the RTS frame from the base station device AP9, the destination of the RTS frame is not its own station, and therefore sets the period indicated by the sustained use period information included in the RTS frame as the NAV period. Further, when the RTS frame as the start frame is received from the base station apparatus AP9, it is detected that the TXOP period has started, and the fact that the base station apparatus AP9 is a transmission right acquisition communication station is stored.
Since the wireless terminal WT93 is receiving interference from the interference station, the wireless terminal WT93 cannot receive the RTS frame from the base station device AP9, the TXOP period has started, and the base station device AP9 is a transmission right acquisition communication station. It cannot be detected.
When receiving the RTS frame addressed to itself from the base station device AP9, the wireless terminal WT91 stores that the base station device AP9 is a transmission right acquisition communication station and returns a CTS frame (time t ₉₅₂ ).

When receiving the CTS frame from the wireless terminal WT91, the base station device AP9 transmits a data frame addressed to the wireless terminal WT91 (time t ₉₅₃ ).
When the wireless terminal WT91 correctly receives the data frame addressed to itself, the wireless terminal WT91 returns a BA frame (or ACK frame) to the base station device AP9 (time t ₉₅₄ ), and ends transmission / reception of the frame. At this time, the wireless terminal WT93 receives the BA frame (or ACK frame) transmitted by the wireless terminal WT91 after receiving no interference from the adjacent cell, and indicates the period indicated by the sustained use period information included in the received frame. Set to NAV period.

Next, in order to transmit data addressed to the wireless terminal WT92, the base station device AP9 transmits an RTS frame whose destination is the wireless terminal WT92 (time t ₉₅₅ ). Here, since the wireless terminal WT92 has received the RTS frame from the base station apparatus AP9 which is a transmission right acquisition communication station, the wireless terminal WT92 returns a CTS frame to the transmission right acquisition communication station regardless of whether or not it is within the NAV period. (Time t ₉₅₆ ).
Since the wireless terminal WT91 and the wireless terminal WT93 have received the RTS frame that is not addressed to themselves, they set the NAV period. If the NAV period has already been set, the NAV value is updated.
The base station apparatus AP9 receives correctly a CTS frame from the wireless terminal WT92, transmits a data frame addressed to the wireless terminal WT92 (time _{t 957).}
When the wireless terminal WT92 correctly receives the data frame from the base station device AP9, the wireless terminal WT92 returns a BA frame (or ACK frame) to the base station device AP9 (time t ₉₅₈ ), and ends transmission / reception of the frame.

Then, the base station apparatus AP9, for sending data to the radio terminal WT93, transmits an RTS frame in which the destination wireless terminal WT93 (time _{t 959).}
Since the wireless terminal WT93 does not store which communication station is the transmission right acquisition communication station, the wireless terminal WT93 determines whether or not the received RTS frame is the RTS frame transmitted from the transmission right acquisition communication station. Cannot be set, and the NAV period is set.
The base station device AP9 cannot receive the CTS frame as a reply from the wireless terminal WT93, and retransmits the RTS frame addressed to the wireless terminal WT93 after the timeout.

FIG. 17 is a time chart showing an example in which the wireless terminal WT93 cannot correctly receive the start frame, as in FIG. In the example shown in FIG. 17, the wireless terminal WT93 receives from a communication station of the adjacent cell (interfering station) the interference to the time t _974, will be described when it is not possible to correctly receive the signal from the base station apparatus AP 9.
First, the base station apparatus AP9 performs CSMA / CA when data addressed to the wireless terminals WT91 to WT93 occurs, and signals transmitted from other communication stations are transmitted over a predetermined sensing period and random backoff time. Confirm that it is not detected and obtain access rights. Since the base station apparatus AP9 has acquired the access right, it becomes a transmission right acquisition communication pole and transmits a frame. The base station device AP9 transmits an RTS frame as a start frame to the wireless terminal WT91 (time t ₉₇₁ ).
At this time, when the radio terminal WT92 receives the RTS frame from the base station device AP9, the destination of the RTS frame is not its own station, and therefore sets the period indicated by the sustained use period information included in the RTS frame as the NAV period. Further, when the RTS frame as the start frame is received from the base station apparatus AP9, it is detected that the TXOP period has started, and the fact that the base station apparatus AP9 is a transmission right acquisition communication station is stored.
Since the wireless terminal WT93 is receiving interference from the interference station, the wireless terminal WT93 cannot receive the RTS frame from the base station device AP9, the TXOP period has started, and the base station device AP9 is a transmission right acquisition communication station. It cannot be detected.
When receiving the RTS frame addressed to itself from the base station device AP9, the wireless terminal WT91 stores that the base station device AP9 is a transmission right acquisition communication station, and transmits the CTS frame (time t ₉₇₂ ).

When the base station apparatus AP9 receives the CTS frame from the wireless terminal WT91, the base station apparatus AP9 transmits a data frame to the wireless terminal WT91 (time t ₉₇₃ ). At this time, the base station device AP9 notifies the wireless terminal WT91 that transmission by RD is possible by setting “1” in the RDG field in the MAC header included in the data frame.
When receiving the data frame including the MAC header in which “1” is set in the RDG field, the wireless terminal WT91 indicates that the data can be transmitted to the base station apparatus AP9 because the RDG field is “1”. It detects and returns a BA frame in which “1” is set in the RDG field (time t ₉₇₄ ). Thereby, the wireless terminal WT91 notifies the base station apparatus AP9 that there is data to be transmitted by RD.
Then, the wireless terminal WT91 transmits a frame addressed to the base station device AP9 after SIFS (time t ₉₇₅ ). The wireless terminal WT91 notifies the base station apparatus AP9, which is a transmission right acquisition communication station, that it is the last frame to be transmitted by setting “0” in the RDG field included in the data frame to be transmitted. . With this base station apparatus AP9 will return a BA frame (or ACK frame) to the wireless terminal WT91 (time _{t 976),} completing the communication with the radio terminal WT91.

Then, the base station apparatus AP9, for sending data to the radio terminal WT93, transmits an RTS frame in which the destination wireless terminal WT93 (time _{t 977).}
Since the wireless terminal WT93 does not store which communication station is the transmission right acquisition communication station, the wireless terminal WT93 determines whether or not the received RTS frame is the RTS frame transmitted from the transmission right acquisition communication station. Cannot be set, and the NAV period is set.
The base station device AP9 cannot receive the CTS frame as a response from the wireless terminal WT93, and retransmits the RTS frame addressed to the wireless terminal WT93 after the timeout.

  As shown in FIGS. 16 and 17, if a start frame (for example, an RTS frame) is transmitted while the communication station is receiving interference from an adjacent cell, the communication station May not be detected as a transmission right acquisition communication station. In such a case, there is a problem that the communication station does not respond to the request from the transmission right acquisition communication station, and retransmission processing is performed, resulting in a decrease in communication throughput.

  The present invention has been made in view of such a situation, and an object thereof is to provide a wireless communication apparatus and a wireless communication method that improve the throughput of wireless communication.

In order to solve the above problem, the present invention provides a plurality of wireless communication apparatuses that perform wireless communication with each other using the same frequency band, and detects a channel idle state by carrier sense within a predetermined period. A start frame generation unit that generates a start frame indicating that the channel is used over a period of time, and after the start frame is generated , the own apparatus performs a channel over the period for all frames transmitted within the period. A notification information generation unit that includes notification information indicating that it is a transmission right acquisition communication station that has a right to use a wireless communication unit that transmits a frame including the start frame and the notification information, A wireless communication device.
In addition, the present invention is a plurality of wireless communication apparatuses that perform wireless communication with each other using the same frequency band, and uses a channel for a predetermined period when it is detected by carrier sense that the channel is idle. A start frame generation unit for generating a start frame indicating that the frame is transmitted as the first frame to be transmitted to the destination of the frame among frames transmitted within the period after the start frame is generated. A notification information generating unit that generates a frame including notification information indicating that it is a transmission right acquisition communication station having a right to use a channel, and a wireless communication unit that transmits a frame including the start frame and the notification information And a wireless communication device.

  Also, in the present invention described above, the notification information generation unit generates the notification information as a part of control information included in a frame, and when the own apparatus is not the transmission right acquisition communication station, When the notification information is detected in the received frame, a transmission right acquisition communication station determination unit that determines that the wireless communication apparatus that is the transmission source of the received frame is the transmission right acquisition communication station is further provided.

  Further, according to the present invention, in the above-described invention, the notification information generation unit generates a frame including the notification information every time the wireless communication device that is the destination of the frame is changed, and the own device transmits the transmission right acquisition communication. The wireless communication apparatus further includes a transmission right acquisition communication station determination unit that determines that the wireless communication apparatus that is the transmission source of the received frame is the transmission right acquisition communication station when the frame is received when it is not a station.

In order to solve the above problem, the present invention is a wireless communication method in a plurality of wireless communication apparatuses that perform wireless communication with each other using the same frequency band, and the channel is idle due to carrier sense. A step of generating a start frame indicating that the channel is used for a predetermined period upon detection; and after generating the start frame, the self-apparatus is within the period for all frames transmitted within the period. Wireless communication, comprising: a step of including notification information indicating that the communication right acquisition communication station has a right to use a channel; and a step of transmitting a frame including the start frame and the notification information. Is the method.
The present invention is also a wireless communication method in a plurality of wireless communication devices that perform wireless communication with each other using the same frequency band, and when a channel is detected free by carrier sense, a predetermined period of time is detected. Generating a start frame indicating that the channel is to be used; and after generating the start frame, the own apparatus as the first frame to be transmitted to the destination of the frame among the frames transmitted within the period Generating a frame including notification information indicating a transmission right acquisition communication station having a right to use a channel over a period of time, and transmitting a frame including the start frame and the notification information A wireless communication method characterized by the above.

  According to the present invention, the wireless communication device that has become the transmission right acquisition communication station generates notification information indicating that the own device is the transmission right acquisition communication station even after generating the start frame. Thereby, even when the start frame cannot be correctly received due to the influence of interference or the like, by receiving the notification information, it is possible to grasp the wireless communication device that has become the transmission right acquisition communication station, and from the transmission right acquisition communication station It is possible to prevent the retransmission process from being performed without responding to the request. As a result, it is possible to improve the throughput by suppressing the occurrence of retransmission processing in the wireless communication system.

It is the schematic which shows the structural example of the radio | wireless communications system in 1st Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless communication apparatus (base station apparatus AP and radio | wireless terminal WT) in the embodiment. It is a figure which shows the structure of the flame | frame which the radio | wireless communication apparatus in the embodiment transmits. It is a flowchart which shows the transmission process of the radio | wireless communication apparatus in the embodiment. It is a flowchart which shows the reception process of the radio | wireless communication apparatus in the embodiment. It is a figure which shows the example of allocation in the case of providing a transmission right acquisition communication station field in the MAC header contained in a control frame. It is a figure which shows the example of allocation in the case of providing a transmission right acquisition communication station field in an HT-Data frame. It is a figure which shows the example of allocation in the case of providing a transmission right acquisition communication station field in a VHT-Data frame. 5 is a time chart showing an example of timing at which the transmission right acquisition communication station in the embodiment transmits a plurality of data frames to other communication devices. 4 is a time chart showing an example of a frame when bidirectional data transmission / reception is performed using the IEEE802.11n RD protocol in the embodiment. 6 is a flowchart illustrating a transmission process of a wireless communication device according to a second embodiment. It is a flowchart which shows the reception process of the radio | wireless communication apparatus in the embodiment. 5 is a time chart showing an example of timing at which the transmission right acquisition communication station in the embodiment transmits a plurality of data frames to other communication devices. It is the time chart which showed the example of the timing which transmits a frame when a transmission right acquisition communication station transmits two or more data frames addressed to other communication stations in TXOP. It is the time chart which showed the example of the frame at the time of applying the RD protocol in IEEE802.11n, and transmitting / receiving data bidirectionally. It is the 1st time chart which showed the example in which a radio terminal cannot receive a start frame correctly. It is the 2nd time chart which showed the example in which a radio | wireless terminal cannot receive a start frame correctly.

(Outline of the present invention)
A feature of the present invention is that the wireless communication apparatus that has become a transmission right acquisition communication station generates and transmits notification information indicating that the own apparatus is a transmission right acquisition communication station even after generating a start frame. is there. Hereinafter, a communication station apparatus and a wireless communication method according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration example of a wireless communication system according to the first embodiment. In the example shown in the figure, the wireless communication system includes two cells A and B. Each cell includes a base station device as a wireless communication device and a wireless terminal. The base station apparatus and the wireless communication terminal perform wireless communication with each other using the same predetermined frequency band. Cell A has one base station device AP1 and three wireless terminals WT11 to WT13. The cell B has one base station device AP2 and one wireless terminal WT21. Cell A and cell B transmit and receive data using the same frequency band. Hereinafter, the description will be made focusing on the cell A. A case where the base station apparatus AP2 and the wireless terminal WT21 included in the cell B are interference stations for the cell A will be described. Hereinafter, when one or both of the base station device AP1 and the base station device AP2 is shown, it is referred to as a base station device AP. Further, when any one or all of the wireless terminals WT11 to WT13 and the wireless terminal WT21 are shown, they are referred to as wireless terminals WT.
In addition, although this embodiment demonstrates the case where a radio | wireless communications system comprises two cells, you may have three or more cells.

FIG. 2 is a schematic block diagram showing the configuration of the wireless communication device (base station device AP and wireless terminal WT) in the present embodiment. As shown in the figure, the wireless communication apparatus includes a wireless communication unit 1, a transmission right acquisition unit 2, a transmission right management unit 3, and a control unit 4.
The wireless communication unit 1 transmits and receives frames to and from other wireless communication devices (base station device AP and wireless terminal WT) using a predetermined frequency band. The transmission right acquisition unit 2 requests the control unit 4 to acquire a transmission right (TXOP) when data to be transmitted to another wireless communication device occurs in the own device. The transmission right management unit 3 detects which communication device is the current transmission right acquisition communication station, and stores information indicating the detected transmission right acquisition communication station. The control unit 4 controls frame transmission / reception performed by the wireless communication unit 1 based on a request from the transmission right acquisition unit 2 and information indicating a transmission right acquisition communication station stored in the transmission right management unit 3.

FIG. 3 is a diagram illustrating a configuration of a frame transmitted by the wireless communication device (base station device AP and wireless terminal WT) in the present embodiment. As shown in the figure, the frame in this embodiment includes a MAC header as control information, a frame body as a payload, and an FCS (Frame Check Sequence) as error detection information. And is configured. The MAC header is provided with a 1-bit “TXOP_holder” field (transmission right acquisition communication station field) as notification information indicating the transmission right acquisition communication station in addition to information defined in the standard. The wireless communication apparatus that has become the transmission right acquisition communication station sets “1” in the transmission right acquisition communication station field in all frames transmitted within the TXOP period in which the apparatus has acquired the transmission right.
The base station device AP and the wireless terminal WT refer to the value of the transmission right acquisition communication station field in the MAC header in the received frame, and when the value is “1”, the wireless communication device that is the transmission source of the received frame Is identified as a transmission right acquisition communication station.

FIG. 4 is a flowchart showing a transmission process of the wireless communication device (base station device AP and wireless terminal WT) in the present embodiment.
In the wireless communication device, when data to be transmitted to another wireless communication device occurs, the transmission right acquisition unit 2 requests the control unit 4 to acquire the transmission right, and the control unit 4 transmits a predetermined value via the wireless communication unit 1. A signal transmitted from another wireless communication apparatus over the sensing period and the random backoff time is not detected, and it is confirmed that it is in an empty state, and a transmission right is acquired. Further, the control unit 4 causes the transmission right management unit 3 to store that the own device is a transmission right acquisition communication station (step S101).
The control unit 4 determines whether or not a reply from the destination wireless communication apparatus is necessary for the frame including the data to be transmitted (step S102). If no reply is necessary (step S102: NO), the control unit 4 proceeds to step S106. Proceed with the process. On the other hand, when a reply is required (step S102: YES), the control unit 4 determines whether or not the own device is a transmission right acquisition communication station (step S103).
When the own device is a transmission right acquisition communication station (step S103: YES), the control unit 4 sets “1” in the transmission right acquisition communication station field in the MAC header included in the frame to be transmitted (step S104). . On the other hand, when the own apparatus is not a transmission right acquisition communication station (step S103: NO), the control unit 4 sets “0” in the transmission right acquisition communication station field in the MAC header included in the frame to be transmitted (step S105). ).
The control unit 4 generates a frame from the MAC header, data to be transmitted, and a frame check sequence (FCS), and transmits the generated frame via the wireless communication unit 1 (step S106).
If no reply from the destination wireless communication device is required, “0” may be set in the transmission right acquisition communication station field.

FIG. 5 is a flowchart showing reception processing of the wireless communication device (base station device AP and wireless terminal WT) in the present embodiment.
In the wireless communication device, when the wireless communication unit 1 correctly receives a frame from another wireless communication device, the control unit 4 sets the value of the transmission right acquisition communication station field in the MAC header included in the received frame to “1”. It is determined whether or not there is (step S201). If the value is “0” (step S201: NO), the process proceeds to step S203. On the other hand, when the value is “1” (step S201: YES), the control unit 4 causes the transmission right management unit 3 to store that the transmission source of the received frame is a transmission right acquisition communication station (step S202).
The control unit 4 executes a necessary process for the received frame (step S203), and ends the reception process.
Here, the processes required for the received frame include, for example, processing for returning a BA frame (or ACK frame), determination of whether or not there is an error in the data included in the received frame, and determination For example, processing for requesting retransmission according to the result.

FIG. 6 is a diagram illustrating an allocation example in the case where a transmission right acquisition communication station field (TXOP_holder) is provided in a MAC header included in a control frame. When the transmission right acquisition communication station field is provided in the control frame, for example, the transmission right acquisition communication station field is assigned to the 10th bit (B10) of the FrameControl field in the MAC header. In the current standard, “0” is set in the “More Fragments” field in control frames such as an RTS frame, a CTS frame, a BAR frame, a BA frame, an ACK frame, and a CF-END frame. Therefore, by redefining the “More Fragments” field as a “More Fragments” field or a transmission right acquisition communication station field, the transmission right acquisition communication station can be identified when a control frame is received.
The use of the 10th bit field is handled as a transmission right acquisition communication station field when the frame is a control frame, and is treated as a “More Fragments” field when the frame is a data frame or a management frame.

FIG. 7 is a diagram illustrating an allocation example in the case where a transmission right acquisition communication station field (TXOP_holder) is provided in the HT-Data frame. When the transmission right acquisition communication station field is provided in the HT-Data frame, any one bit of the reserved area (Reserved) from the 25th bit to the 29th bit in the “HT Control” of 4 octets (32 bits) in the MAC header Is assigned to the transmission right acquisition communication station field. FIG. 7 shows an example in which a transmission right acquisition communication station field is assigned to the 29th bit.
FIG. 8 is a diagram illustrating an allocation example in the case where a transmission right acquisition communication station field (TXOP_holder) is provided in the VHT-Data frame. When assigning the transmission right acquisition communication station field to the VHT-Data frame, the transmission right acquisition communication station field is assigned to the reserved area (Reserved) of the second bit in “HT Control” of 4 octets in the MAC header.
In this way, a transmission right acquisition communication station field (TXOP holder) can be provided in a frame defined in the standard.

  Hereinafter, in the cell A illustrated in FIG. 1, a frame sequence indicating a communication operation of the cell A when the wireless terminal WT13 receives interference from the adjacent cell B will be described. Here, in cell A, an example in which base station apparatus AP1 accommodates data addressed to wireless terminals WT11 to WT13 and transmits data frames addressed to wireless terminals WT11 to WT13 within the same TXOP period. Also, when the base station apparatus AP1 transmits an RTS frame as a start frame, the wireless terminal WT13 is receiving interference, and the base station apparatus AP1 and the wireless terminal WT11 are communicating with each other while the wireless terminal WT13 is communicating. Shows an example where no interference occurs.

FIG. 9 is a time chart showing an example of timing at which the transmission right acquisition communication station (base station device AP1) transmits a plurality of data frames addressed to other communication devices in the present embodiment. In the figure, the horizontal axis indicates time.
First, the base station apparatus AP1 performs CSMA / CA (carrier sense) when data addressed to the wireless terminals WT11 to WT13 occurs, and performs other wireless communication apparatuses (wireless communication) over a predetermined sensing period and random backoff period. Confirm that the signals transmitted from the terminals WT11 to WT13) are not detected, and acquire the transmission right (TXOP). Since the base station apparatus AP1 has acquired the transmission right, it becomes a transmission right acquisition communication station and transmits a frame. The base station device AP1 transmits an RTS frame as a start frame to the wireless terminal WT11 (time t ₁₀₁ ). Here, the base station device AP1 sets “1” in the transmission right acquisition communication station field in the MAC header included in the RTS frame to be transmitted. Further, the RTS frame transmitted as the start frame includes sustained use period information, and other wireless communication apparatuses are notified that the right to use the channel has been acquired in the period indicated by the sustained use period information. The
In this case, when receiving the RTS frame from the base station apparatus AP1, the wireless terminal WT12 detects that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame. The transmission right management unit 3 records that the base station apparatus AP1 that is the transmission source of the RTS frame is a transmission right acquisition communication station. In addition, when the NAV period is not set in the own device, the wireless terminal WT12 receives the RTS frame not addressed to the own device, so that the period indicated by the sustained use period information included in the received RTS frame is The period is set so that the frame is not transmitted in the corresponding NAV period. In addition, the wireless terminal WT12 detects that the TXOP period is started by receiving the RTS frame as the start frame.

Since the wireless terminal WT13 receives interference from the interference station, it cannot receive the RTS frame from the base station device AP1, the TXOP period has started, and the base station device AP1 is a transmission right acquisition communication station. It cannot be detected.
Upon receiving the RTS frame from the base station device AP1, the wireless terminal WT11 detects that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame, and the RTS frame It records in the transmission right management unit 3 that the base station device AP1 as the transmission source is a transmission right acquisition communication station. Also, the wireless terminal WT11 detects that the destination of the received RTS frame is its own device, and returns the CTS frame to the base station device AP1 (time t ₁₀₂ ).
When receiving the CTS frame from the wireless terminal WT11, the base station apparatus AP1 transmits a data frame addressed to the wireless terminal WT11 (time t ₁₀₃ ). In this data frame, “1” is set in the transmission right acquisition communication station field in the MAC header. While the base station device AP1 is transmitting a data frame addressed to the wireless terminal WT11, the wireless terminal WT13 does not receive interference.
When the wireless terminal WT11 correctly receives the data frame addressed to itself from the base station device AP1, the wireless terminal WT11 transmits a BA frame (or ACK frame) to the base station device AP1 (time t ₁₀₄ ), and finishes transmission / reception of the frame. At this time, the wireless terminal WT13 receives the BA frame (or ACK frame) transmitted by the wireless terminal WT11, and sets the period indicated by the sustained use period information included in the received frame as the NAV period.

Next, in order to transmit data addressed to the wireless terminal WT12, the base station device AP1 transmits an RTS frame with the destination being the wireless terminal WT12 (time t ₁₀₅ ). Here, the base station device AP1 sets “1” in the transmission right acquisition communication station field in the MAC header included in the RTS frame to be transmitted.
At this time, the wireless terminal WT11 and the wireless terminal WT13 detect that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame, and are the transmission sources of the RTS frame. The transmission right management unit 3 records that the base station device AP1 is a transmission right acquisition communication station. Further, the wireless terminal WT11 and the wireless terminal WT13 set the period indicated by the sustained use period information included in the received RTS frame as the NAV period.
The wireless terminal WT12 detects that the destination of the received RTS frame is its own device, and confirms that the transmission source of the RTS frame matches the transmission right acquisition communication station stored in the transmission right management unit 3. To detect. Based on this detection result, the wireless terminal WT12 returns a CTS frame to the base station apparatus AP1 regardless of whether it is the NAV period (time t ₁₀₆ ).
When the base station apparatus AP1 correctly receives the CTS frame from the wireless terminal WT12, the base station apparatus AP1 transmits a data frame addressed to the wireless terminal WT12 (time t ₁₀₇ ).
When the wireless terminal WT12 correctly receives the data frame from the base station apparatus AP1, the wireless terminal WT12 returns a BA frame (or ACK frame) to the base station apparatus AP1 (time t ₁₀₈ ), and finishes transmission / reception of the frame.

Next, the base station device AP1 transmits an RTS frame as the destination wireless terminal WT13 in order to transmit data addressed to the wireless terminal WT13 (time t ₁₀₉ ). Here, the base station apparatus AP1, as in the RTS frame transmitted at time _{t 101} and time _{t 105,} and sets "1" to the transmission right acquisition communication station field in the MAC header included in RTS frame transmitted.
At this time, the wireless terminal WT11 and the wireless terminal WT12 detect that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame, and are the transmission sources of the RTS frame. The transmission right management unit 3 records that the base station device AP1 is a transmission right acquisition communication station. Also, the wireless terminal WT11 and the wireless terminal WT12 set the period indicated by the sustained use period information included in the received RTS frame as the NAV period.
The wireless terminal WT13 detects that the destination of the received RTS frame is its own device, and confirms that the transmission source of the RTS frame matches the transmission right acquisition communication station stored in the transmission right management unit 3. To detect. Based on this detection result, the radio terminal WT13 is to whether or a NAV period, returns a CTS frame to the base station apparatus AP1 (time _{t 110).}
When the base station apparatus AP1 correctly receives the CTS frame from the wireless terminal WT13, the base station apparatus AP1 transmits a data frame addressed to the wireless terminal WT13 (time t ₁₁₁ ).
When the wireless terminal WT13 correctly receives the data frame from the base station device AP1, the wireless terminal WT13 returns a BA frame (or ACK frame) to the base station device AP1 (time t ₁₁₂ ), and finishes transmission / reception of the frame.

FIG. 10 is a time chart showing an example of a frame when bidirectional data transmission / reception is performed using the IEEE802.11n RD protocol in the present embodiment. In the figure, the horizontal axis indicates time. Here, an example is shown in which the base station device AP1 transmits and receives data to and from the wireless terminal WT91 and the wireless terminal WT13.
The base station device AP1 performs CSMA / CA when data addressed to the wireless terminals WT11 and WT13 occurs, and signals transmitted from other communication devices are not detected over a predetermined sensing period and random backoff period. Confirm that you have the right to send. Since the base station apparatus AP1 has acquired the transmission right, it becomes a transmission right acquisition communication station and transmits a frame. The base station device AP1 transmits an RTS frame as a start frame to the wireless terminal WT11 (time t ₁₂₁ ). Here, the base station device AP1 sets “1” in the transmission right acquisition communication station field in the MAC header included in the RTS frame to be transmitted.
At this time, when the wireless terminal WT12 receives an RTS frame not addressed to itself from the base station device AP1, “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame. And records in the transmission right management unit 3 that the base station apparatus AP1 that is the transmission source of the RTS frame is a transmission right acquisition communication station. Also, the wireless terminal WT12 sets the period indicated by the sustained use period information included in the received RTS frame as the NAV period, and does not transmit the frame in the corresponding NAV period. In addition, the wireless terminal WT12 detects that the TXOP period is started by receiving the RTS frame as the start frame.

Since the wireless terminal WT13 receives interference from the interference station, it cannot receive the RTS frame from the base station device AP1, the TXOP period has started, and the base station device AP1 is a transmission right acquisition communication station. It cannot be detected.
Upon receiving the RTS frame from the base station device AP1, the wireless terminal WT11 detects that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame, and the RTS frame It records in the transmission right management unit 3 that the base station device AP1 as the transmission source is a transmission right acquisition communication station. Also, the wireless terminal WT11 detects that the destination of the received RTS frame is its own device, and returns the CTS frame to the base station device AP1 (time t ₁₂₂ ).

When receiving the CTS frame from the wireless terminal WT11, the base station device AP1 transmits a data frame addressed to the wireless terminal WT11 (time t ₁₂₃ ). At this time, the base station device AP1 notifies the wireless terminal WT11 that transmission in RD (reverse direction) is possible by setting “1” in the RDG field in the MAC header included in the data frame. .
When receiving the data frame including the MAC header in which “1” is set in the RDG field from the base station apparatus AP1, the wireless terminal WT11 detects that the data can be transmitted to the base station apparatus AP1, and includes the MAC header. A BA frame (or ACK frame) in which “1” is set in the RDG field is returned to the base station apparatus AP1 (time t ₁₂₄ ). Thereby, the radio terminal WT11 notifies the base station apparatus AP1 that there is data to be transmitted by RD.

Then, the wireless terminal WT11 transmits a data frame to the base station device AP1 after SIFS (time t ₁₂₅ ). The wireless terminal WT11 sets “0” in the RDG field of the data frame to be transmitted, thereby notifying the base station apparatus AP1 that is a transmission right acquisition communication station that it is the last data frame to be transmitted. At this time, the wireless terminal WT13 receives the data frame addressed to the wireless terminal WT11 and detects that “1” is set in the transmission right acquisition communication station field (TXOP_Holder) in the MAC header of the received data frame. Then, it is determined that the base station device AP1 that has transmitted the data frame is a transmission detection communication station, and records in the transmission right management unit 3 that the base station device AP1 is a transmission right acquisition communication station.
When the base station device AP1 receives the data frame from the wireless terminal WT11, the base station device AP1 returns a BA frame (or ACK frame) to the wireless terminal WT11 (time t ₁₂₆ ), and ends the communication with the wireless terminal WT11.

Next, the base station device AP1 transmits an RTS frame whose destination is the wireless terminal WT13 (time t ₁₂₇ ). At this time, the base station device AP1 sets “1” in the transmission right acquisition communication station field in the MAC header included in the RTS frame to be transmitted.
The wireless terminal WT11 and the wireless terminal WT12 detect that “1” is set in the transmission right acquisition communication station field in the MAC header included in the RTS frame received from the base station device AP1, and transmit the source of the RTS frame. Is recorded in the transmission right management unit 3 that the base station apparatus AP1 is a transmission right acquisition communication station. Further, when the wireless terminal WT11 and the wireless terminal WT12 detect that the received RTS frame is not addressed to their own devices, the wireless terminal WT11 and the wireless terminal WT12 set the period indicated by the sustained use period information included in the received RTS frame as the NAV period.
The wireless terminal WT13 indicates that the RTS frame received from the base station device AP1 is addressed to itself, and that “1” is set in the transmission right acquisition communication station field in the MAC header included in the received RTS frame. Is detected, the CTS frame is transmitted to the base station apparatus AP1 regardless of whether it is the NAV period (time t ₁₂₈ ).

When receiving the CTS frame from the wireless terminal WT13, the base station device AP1 transmits a data frame addressed to the wireless terminal WT13 (time t ₁₂₉ ). At this time, the base station device AP1 notifies the wireless terminal WT13 that transmission by RD is possible by setting “1” in the RDG field in the MAC header included in the data frame.
When the wireless terminal WT13 receives from the base station device AP1 a data frame addressed to itself whose RDG field in the MAC header is set to “1”, the wireless terminal WT13 detects that data can be transmitted by the RD, and the DA frame At the same time, the data frame is transmitted to the base station apparatus AP1 (time _t130 ). At this time, the wireless terminal WT13 sets “0” in the RDG field in the MAC header included in the data frame to notify that there is no data to be transmitted.
When the base station device AP1 receives the BA frame and the data frame from the wireless terminal WT13, the base station device AP1 returns the BA frame to the wireless terminal WT13 (time t ₁₃₁ ) and ends the communication with the wireless terminal WT13.

As described with reference to FIG. 9 and FIG. 10, the transmission right acquisition communication station field is provided in each frame, and the wireless communication apparatus that has become the transmission right acquisition communication station (TXOP Holder) A frame including information indicating that the own apparatus is a transmission right acquisition communication station is transmitted. As a result, the base station device AP1 and the wireless terminals WT11 to WT13 (wireless communication devices) cannot receive the start frame indicating the start of the TXOP period due to interference or the like, and cannot grasp the transmission right acquisition communication station. By receiving a frame transmitted by the transmission right acquisition communication station after no interference is received, it is possible to detect which wireless communication device is the transmission right acquisition communication station.
In this way, even if the start frame cannot be correctly received, it is possible to determine which wireless communication device the transmission right acquisition communication station is, so that the retransmission process can be performed without responding to a request from the transmission right acquisition communication station. Can be suppressed. As a result, it is possible to improve the throughput by suppressing the occurrence of retransmission processing in the wireless communication system.

(Second Embodiment)
In the second embodiment, the transmission right acquisition communication station is notified without providing new information (transmission right acquisition communication station field) in the MAC header included in the frame. Specifically, the communication station apparatus is notified using a new frame (notification frame) for notifying the transmission right acquisition communication station. This notification frame has a data structure different from the RTS frame, the CTS frame, the data frame, and the like. That is, it is a frame that includes a transmission source address of the notification frame and information indicating that the frame is transmitted by the transmission right acquisition communication station. Note that the configuration of the wireless communication device (base station device AP1 and wireless terminals WT11 to WT13) is the same as that of the first embodiment, and thus the description of the configuration of the wireless communication device is omitted.

FIG. 11 is a flowchart illustrating a transmission process of the wireless communication device (base station device AP and wireless terminal WT) in the second embodiment.
In the wireless communication device, when data to be transmitted to another wireless communication device occurs, the transmission right acquisition unit 2 requests the control unit 4 to acquire the transmission right, and the control unit 4 transmits a predetermined value via the wireless communication unit 1. A transmission right is acquired after confirming that a signal transmitted from another wireless communication apparatus is not detected over the sensing period and the random back-off time. Further, the control unit 4 causes the transmission right management unit 3 to store that the own device is a transmission right acquisition communication station (step S301).
The control unit 4 determines whether or not a reply from the destination wireless communication apparatus is necessary for a frame including data to be transmitted (step S302), and when a reply is not necessary (step S302: NO), The process proceeds to step S306. On the other hand, when a reply is necessary (step S302: YES), the control unit 4 determines whether or not the own apparatus is a transmission right acquisition communication station (step S303).

If the own device is not a transmission right acquisition communication station (step S302: NO), the control unit 4 advances the process to step S306. On the other hand, when the own apparatus is a transmission right acquisition communication station (step S302: YES), the control unit 4 does not transmit the first frame in the current TXOP period, and the destination of the frame to be transmitted from now on. It is determined whether or not the first frame is transmitted to the wireless communication device (step S304).
When the frame to be transmitted is not the transmission of the first frame in the TXOP period and is the transmission of the first frame to the wireless communication device that is the destination of the frame (step S304: YES), the control unit 4 transmits the frame. A notification frame indicating the right acquisition communication station is transmitted via the wireless communication unit 1 (step S305). Note that the destination address of the notification frame may be a wireless communication device that is a destination of a frame to be transmitted, or may be a broadcast address.
On the other hand, if the frame to be transmitted is not the transmission of the first frame in the TXOP period, or is not the transmission of the first frame to the wireless communication device that is the destination of the frame (step S304: NO), the control unit 4 performs the process. Proceed to step S306.
The control unit 4 generates a frame from the MAC header, data to be transmitted, and a frame check sequence (FCS), and transmits the generated frame via the wireless communication unit 1 (step S306).

FIG. 12 is a flowchart showing reception processing of the wireless communication device (base station device AP and wireless terminal WT) in the present embodiment.
In the wireless communication device, when the wireless communication unit 1 correctly receives a frame from another wireless communication device, the control unit 4 determines whether or not the received frame is a notification frame (step S401). If it is not a notification frame (step S401: NO), the process proceeds to step S403. On the other hand, when the received frame is a notification frame (step S401: YES), the control unit 4 stores in the transmission right management unit 3 that the wireless communication device that has transmitted the received frame is a transmission right acquisition communication station. (Step S402).
The control unit 4 executes a necessary process for the received frame (step S403) and ends the reception process.
Here, the process necessary for the received frame is included in the process of returning a BA frame (or ACK frame) or the like, as in the reception process (FIG. 5) in the first embodiment. For example, a determination of whether or not there is an error in the data to be transmitted, and a process of requesting retransmission according to the determination result.

  FIG. 13 is a time chart showing an example of timing at which the transmission right acquisition communication station (base station device AP1) transmits a plurality of data frames addressed to other communication devices in the present embodiment. In the figure, the horizontal axis indicates time. Here, an example is shown in which base station apparatus AP1 accommodates data addressed to wireless terminals WT11-WT13 and transmits data frames addressed to wireless terminals WT11-WT13 within the same TXOP period. Also, when the base station apparatus AP1 transmits an RTS frame as a start frame, the wireless terminal WT13 is receiving interference, and the base station apparatus AP1 and the wireless terminal WT11 are communicating with each other while the wireless terminal WT13 is communicating. Shows an example where no interference occurs.

The base station device AP1 performs CSMA / CA when data addressed to the wireless terminals WT11 to WT13 occurs, and from other wireless communication devices (wireless terminals WT11 to WT13) over a predetermined sensing period and random backoff period. After confirming that the transmitted signal is not detected, the transmission right (TXOP is acquired. The base station apparatus AP1 becomes the transmission right acquisition communication station (TXOP Holder) because the transmission right is acquired, and transmits the frame. The station device AP1 transmits an RTS frame as a start frame to the wireless terminal WT11 (time t ₂₀₁ ).
At this time, when receiving the RTS frame from the base station device AP1, the wireless terminal WT12 determines that the base station device AP1 is a transmission right acquisition communication station because the NAV period is not set in the own device, and the base station It records in the transmission right management unit 3 that the device AP1 is a transmission right acquisition communication station. Also, the wireless terminal WT12 sets the period indicated by the sustained use period information included in the received RTS frame as the NAV period. Since the wireless terminal WT13 is receiving interference, it cannot receive the RTS frame and cannot determine which device the transmission right acquisition communication station is.
When receiving the RTS frame from the base station device AP1, the wireless terminal WT11 determines that the base station device AP1 is a transmission right acquisition communication station because the NAV period is not set in the own device. Also, the wireless terminal WT11 transmits the CTS frame to the base station device AP1 because the received RTS frame is addressed to the own device and the NAV period is not set in the own device (time t ₂₀₂ ).
When the base station apparatus AP1 receives the CTS frame from the wireless terminal WT11, the base station apparatus AP1 transmits a data frame addressed to the wireless terminal WT11 (time t ₂₀₃ ).
When the wireless terminal WT11 correctly receives the data frame addressed to itself, the wireless terminal WT11 returns a BA frame (or ACK frame) to the base station device AP1 (time _t204 ), and ends transmission / reception of the frame.

Then, the base station apparatus AP1, for sending data to the radio terminal WT12, transmits a notification frame (time _{t 205),} further, it transmits the RTS frame addressed to the wireless terminal WT12 (time _{t 206).}
Upon receiving the notification frame from the base station device AP1, the wireless terminal WT11 and the wireless terminal WT13 determine that the base station device AP1 that is the transmission source of the notification frame is a transmission right acquisition communication station, and the base station device AP1 It records in the transmission right management unit 3 that it is an acquired communication station. Also, the wireless terminal WT11 and the wireless terminal WT13 set the period indicated by the sustained use period information included in the received notification frame as the NAV period.
When the wireless terminal WT12 receives the RTS frame addressed to itself from the base station device AP1, the transmission source of the RTS frame matches the wireless communication device stored in the transmission right management unit 3, and therefore the NAV period is set. The CTS frame is returned to the base station apparatus AP1, which is a transmission right acquisition communication station, regardless of whether or not it is transmitted (time t ₂₀₇ ).
When the base station apparatus AP1 receives the CTS frame from the wireless terminal WT12, the base station apparatus AP1 transmits a data frame addressed to the wireless terminal WT12 (time t ₂₀₈ ).
When the wireless terminal WT12 correctly receives the data frame addressed to itself, the wireless terminal WT12 returns a BA frame (or ACK frame) to the base station device AP1 (time t ₂₀₉ ), and ends transmission / reception of the frame.

Next, the base station device AP1 transmits a notification frame to transmit data addressed to the wireless terminal WT13 (time t ₂₁₀ ), and further transmits an RTS frame addressed to the wireless terminal WT 13 (time t ₂₁₁ ).
Upon receiving the notification frame from the base station device AP1, the wireless terminal WT11 and the wireless terminal WT12 determine that the base station device AP1 that is the transmission source of the notification frame is a transmission right acquisition communication station, and the base station device AP1 It records in the transmission right management unit 3 that it is an acquired communication station. Further, the wireless terminal WT11 and the wireless terminal WT12 set the period indicated by the sustained use period information included in the received notification frame as the NAV period.
When the wireless terminal WT13 receives the RTS frame addressed to itself from the base station device AP1, the wireless terminal WT13 is located at the transmission source of the RTS frame and the wireless communication device stored in the transmission right management unit 3, so the NAV period is set. The CTS frame is returned to the base station apparatus AP1, which is a transmission right acquisition communication station, regardless of whether or not it is transmitted (time t ₂₁₂ ).
The base station apparatus AP1 receives the CTS frame from the wireless terminal WT13, transmits a data frame addressed to the wireless terminal WT13 (time _{t 213).}
When the wireless terminal WT13 correctly receives the data frame addressed to itself, the wireless terminal WT13 returns a BA frame (or ACK frame) to the base station apparatus AP1 (time t ₂₁₄ ), and finishes transmission / reception of the frame.

In this way, the wireless communication device that has become the transmission right acquisition communication station (TXOP Holder) is the transmission right acquisition communication station before changing the frame destination and transmitting the RTS frame in the TXOP period. A notification frame indicating that is transmitted. As a result, the base station device AP1 and the wireless terminals WT11 to WT13 (wireless communication devices) cannot receive the start frame indicating the start of the TXOP period due to interference or the like, and cannot grasp the transmission right acquisition communication station. By receiving the notification frame after receiving no interference, it is possible to detect which wireless communication device is a transmission right acquisition communication station.
Even if the wireless communication device cannot correctly receive the start frame, it can determine which wireless communication device the transmission right acquisition communication station is, so it can retransmit without responding to the request from the transmission right acquisition communication station. It can suppress that a process will be performed. As a result, it is possible to improve the throughput by suppressing the occurrence of retransmission processing in the wireless communication system.

  In the above-described first and second embodiments, the time chart when the base station apparatus AP1 is a transmission right acquisition communication station has been shown and described, but the wireless terminals WT11 to WT13 are not limited to this, and It may be a transmission right acquisition communication station.

  Note that a program for realizing the function of the wireless communication apparatus according to the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by a computer system and executed to perform transmission processing and A reception process may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

AP1, AP2, AP9, AP ... base station devices WT11, WT12, WT13, WT21, WT91, WT92, WT93, WT ... wireless terminal 1 ... wireless communication unit 2 ... transmission right acquisition unit 3 ... transmission right management unit 4 ... control unit (Start frame generation unit, notification information generation unit, transmission right acquisition communication station determination unit)

Claims (6)

A plurality of wireless communication devices that perform wireless communication with each other using the same frequency band,
A start frame generation unit that generates a start frame indicating that the channel is used for a predetermined period when it is detected by carrier sense that the channel is idle;
After generating the start frame, for all frames transmitted within the period, notification information indicating that the own apparatus is a transmission right acquisition communication station having a right to use the channel over the period is included. A notification information generation unit;
A wireless communication unit for transmitting a frame including the start frame and the notification information;
A wireless communication apparatus comprising: A plurality of wireless communication devices that perform wireless communication with each other using the same frequency band,
A start frame generation unit that generates a start frame indicating that the channel is used for a predetermined period when it is detected by carrier sense that the channel is idle;
After generating the start frame, transmission right acquisition communication in which the own apparatus has a right to use the channel over the period as a frame to be transmitted first to a destination of the frame among frames transmitted within the period A notification information generating unit that generates a frame including notification information indicating a station;
A wireless communication unit for transmitting a frame including the start frame and the notification information;
A wireless communication apparatus comprising: A wireless communication device according to any one of claims 1 and 2 ,
The notification information generation unit generates the notification information as part of control information included in a frame,
When the own apparatus is not the transmission right acquisition communication station, the transmission right acquisition communication station determines that the wireless communication apparatus that is the transmission source of the received frame is the transmission right acquisition communication station when the notification information is detected in the received frame A wireless communication apparatus further comprising a determination unit. A wireless communication device according to any one of claims 1 and 2 ,
The notification information generation unit generates a frame including the notification information every time the wireless communication device of the frame destination is changed,
A transmission right acquisition communication station determination unit that determines, when receiving the frame when the own apparatus is not the transmission right acquisition communication station, that the wireless communication apparatus that is the transmission source of the received frame is the transmission right acquisition communication station; A wireless communication device comprising: A wireless communication method in a plurality of wireless communication devices that perform wireless communication with each other using the same frequency band,
Generating a start frame indicating that the channel is used for a predetermined period of time when detecting that the channel is idle by carrier sense;
After generating the start frame, for all frames transmitted within the period, notification information indicating that the own apparatus is a transmission right acquisition communication station having a right to use the channel over the period is included. Steps,
And a step of transmitting a frame including the start frame and the notification information. A wireless communication method in a plurality of wireless communication devices that perform wireless communication with each other using the same frequency band,
Generating a start frame indicating that the channel is used for a predetermined period of time when detecting that the channel is idle by carrier sense;
After generating the start frame, transmission right acquisition communication in which the own apparatus has a right to use the channel over the period as a frame to be transmitted first to a destination of the frame among frames transmitted within the period Generating a frame including notification information indicating a station;
And a step of transmitting a frame including the start frame and the notification information.

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