JP6006854B2 - 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 scheme, 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. The communication station that issued the transmission request first monitors the state of the wireless medium for a predetermined sensing period (DIFS: Distributed Inter-FrameSpace), and if there is no transmission signal from another communication station during this period, a random backoff is performed. I do. 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. 12 and 13. FIG. 12 is a time chart showing an example of timing for 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.

Next, 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 device AP9 has acquired the transmission right, it becomes a transmission right acquisition communication station (TXOP Holder) and transmits a 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 frames.

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 prior art, only one-way data transmission is performed in which a communication station that has acquired a 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 this (reverse direction permission information), the receiving station of the data 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. 13 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 NAV 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 example 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. 14 and 15.

FIG. 14 is a time chart illustrating 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. 12, the base station device AP9 and the wireless terminals WT91 to WT93 are communication stations, the base station device AP9 accommodates data addressed to the wireless terminals WT91 to WT93, and the 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 return CTS frame. 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. 15 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. 15, 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 return CTS frame. 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.

  In this way, if a start frame (for example, an RTS frame) is transmitted while the communication station is receiving interference from an adjacent cell or the like, any of the communication stations is a transmission right acquisition communication station. May not be detected. In such a case, there is a problem that the communication station does not respond to a 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 circumstances, and an object of the present invention is to provide a wireless communication apparatus and a wireless communication method capable of improving the throughput in wireless communication.

  One aspect of the present invention is a wireless communication apparatus that operates as the communication station when a plurality of communication stations perform wireless communication using the same frequency band, and identifies and specifies a communication station that has acquired a transmission right A transmission right acquisition communication station management means for holding information related to the communication station, and a response frame based on the information about the communication station that acquired the transmission right held in the transmission right acquisition communication station management means for a certain period of time. And a control unit that determines whether or not to perform transmission.

  In one aspect of the present invention, the transmission right acquisition communication station management unit determines that the transmission source communication station is a transmission right acquisition communication station if the received frame is a BAR frame, and if the received frame is a BA frame, Is a transmission right acquisition communication station, and in the case of a DATA frame or an RTS frame, the transmission source communication station determines that there is a possibility of a transmission right acquisition communication station. In the case of a CTS frame, the destination communication station determines that the transmission right acquisition communication It is determined that there is a possibility of a station.

  One aspect of the present invention is a wireless communication method performed by a wireless communication device that operates as the communication station when a plurality of communication stations perform wireless communication using the same frequency band, the communication station having acquired a transmission right A transmission right acquisition communication station management step for storing information relating to the specified communication station, and information relating to the communication station that acquired the transmission right held for a certain period by the transmission right acquisition communication station management. And a control step for determining whether to transmit a response frame based on the control frame.

  One aspect of the present invention is that the transmission right acquisition communication station operates as the communication station by applying an RD protocol that permits data transmission in the reverse direction when a plurality of communication stations perform wireless communication using the same frequency band. If the received frame is an RTS frame, it is determined whether or not the determination result information on the communication station is already held. Determines that there is a possibility of a transmission right acquisition communication station, holds the determination result information, and deletes the determination result information if it does not receive a frame within a predetermined period. When the original communication station is determined to be a transmission right acquisition communication station, the determination result information is retained only during the continuous use period of the frame, and any of the BAR frame, BA frame, DATA frame, and CTS frame It is determined whether or not determination result information about the communication station is already held, and if not, it is determined that the transmission source or destination communication station may be a transmission right acquisition communication station, The determination result information is retained only for the sustained use period of the frame. When the determination result information is retained, it is determined that the transmission source or destination communication station is a transmission right acquisition communication station, and the determination result information is stored in the frame duration. The communication station that acquired the transmission right by specifying only the period of use is specified, and the transmission right acquisition communication station management unit that holds the determination result information regarding the specified communication station, and the transmission right acquisition communication station management unit holds And a control unit that determines whether or not to transmit a response frame based on the determination result information regarding the communication station that has acquired the transmission right to be transmitted.

  One aspect of the present invention is that the transmission right acquisition communication station operates as the communication station by applying an RD protocol that permits data transmission in the reverse direction when a plurality of communication stations perform wireless communication using the same frequency band. If the received frame is an RTS frame, it is determined whether or not the determination result information regarding the communication station is already held. It is determined that the transmission source communication station may be a transmission right acquisition communication station, holds the determination result information, and deletes and holds the determination result information if a frame is not received within a predetermined period. In this case, it is determined that the transmission source communication station is a transmission right acquisition communication station, and the determination result information is retained only during the continuous use period of the frame, and the BAR frame, BA frame, DATA frame, CTS frame is retained. In any of the cases, it is determined whether or not the determination result information about the communication station is already held. If not, the transmission source or destination communication station may be a transmission right acquisition communication station. It is determined that the determination result information is retained only for the sustained use period of the frame, and if it is retained, it is determined that the source or destination communication station is a transmission right acquisition communication station, and the determination result A transmission right acquisition communication station managing step for identifying a communication station that has acquired a transmission right by holding information only for the duration of use of the frame, and holding the determination result information regarding the specified communication station, and the transmission right acquisition A control step for determining whether or not to transmit a response frame based on the determination result information regarding the communication station that has acquired the transmission right held by the communication station management step. It is a wireless communication method for.

  According to the present invention, even when the start frame cannot be correctly received due to the influence of interference or the like, it is possible to grasp the wireless communication apparatus that has become the transmission right acquisition communication station by estimating or specifying the transmission right acquisition communication station. It is possible to suppress retransmission processing without responding to a request from the transmission right acquisition communication station. 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. 4 is a flowchart showing an outline of a process for estimating or determining a transmission right acquisition communication station of the wireless communication apparatus in the embodiment. It is a flowchart which shows a transmission right acquisition communication station of a radio | wireless communication apparatus in a system in which the RD method in the same embodiment is invalid, or a judgment process. It is the time chart which showed the example in the case of estimating and specifying a transmission-right acquisition communication station using a BA (ACK) frame with the system in which the RD method in the same embodiment is invalid. It is the time chart which showed the example in the case of estimating and specifying a transmission right acquisition communication station using a BAR frame in the system where the RD method in the embodiment is invalid. It is the time chart which showed the example in the case of estimating and specifying a transmission-right acquisition communication station using a DATA frame with the system in which the RD method in the same embodiment is invalid. It is the time chart which showed the example in the case of estimating and specifying a transmission right acquisition communication station using a BAR frame in the system where the RD method in the embodiment is invalid. It is the time chart which showed the example in the case of estimating and specifying a transmission right acquisition communication station using an RTS frame in the system where the RD method in the embodiment is invalid. 4 is a flowchart showing a transmission process of a wireless communication apparatus in which the IEEE 802.11n RD method is effective in the embodiment. 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. 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.

  Hereinafter, a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration example of a wireless communication system according to the embodiment. The feature of this embodiment is that a communication station that has not correctly received the TXOP start frame estimates and specifies the transmission right acquisition communication station using the frame that is correctly received. In the example illustrated in FIG. 1, the wireless communication system includes two cells A and B. Each cell A and B has a base station apparatus 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 device includes a wireless communication unit 1, a control unit 2, and a transmission right acquisition communication station management unit 3 that performs a process of estimating / specifying a transmission right acquisition communication station (TXOP Holder). I have. 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 communication station management unit 3 performs estimation or determination processing of the transmission right acquisition communication station. The control unit 2 controls frame transmission / reception performed by the wireless communication unit 1 based on information indicating the transmission right acquisition communication station stored in the transmission right acquisition communication station management unit 3.

  FIG. 3 is a flowchart showing a processing operation for estimating or determining a transmission right acquisition communication station of the wireless communication devices (base station device AP and wireless terminal WT) in the present embodiment. First, when the wireless communication apparatus receives a frame (step S101), the control unit 2 determines whether the Duration value of the received frame is 0 (step S102). When the Duration value is 0 (step S102: YES), the TXOP period is ended, so that it is not necessary to perform estimation / determination of the transmission right acquisition communication station, and necessary processing (step S103) is performed on the received frame.

  On the other hand, if the Duration value of the received frame is not 0 (step S102: NO), the control unit 2 refers to the information of the transmission right acquisition communication station management unit 3 that estimates and determines the transmission right acquisition communication station. In the transmission right acquisition communication station management unit 3, if there is already information related to the transmission right acquisition communication station, that is, information that can identify the transmission right acquisition communication station (step S104: YES), necessary processing for the received frame based on that information The control unit 2 is instructed to proceed.

  In the transmission right acquisition communication station management unit 3, if there is no information about the transmission right acquisition communication station, that is, information that can identify the transmission right acquisition communication station (step S104: NO), it is based on the transmission / reception transmission device address of the received frame. It is determined whether or not the transmission right acquisition communication station can be specified (step S105). If the transmission right acquisition communication station can be specified (step S105: YES), the transmission right acquisition communication station is specified by storing the information (step S106), and the necessary processing for the received frame is advanced (step S103). .

  On the other hand, if the transmission right acquisition communication station cannot be specified (step S105: NO), it is determined whether a transmission right acquisition communication station candidate can be estimated (step S107). If the candidate for the transmission right acquisition communication station can be estimated in step S107, the information is stored (step S108), and the necessary processing for the received frame is advanced (step S103). If the candidate for the transmission right acquisition communication station cannot be estimated in step S107, the necessary processing for the received frame is advanced (step S103).

  FIG. 4 is a flowchart showing a processing operation for estimating or determining a transmission right acquisition communication station of the wireless communication apparatus in a system in which the RD technique in the embodiment is invalid. First, in the wireless communication apparatus, when a frame is received (step S201), it is determined whether the Duration value of the received frame is 0 (step S202). When the Duration value is 0, the TXOP period ends, so that it is not necessary to perform estimation / determination of the transmission right acquisition communication station, and a necessary process for the received frame is performed (step S203).

On the other hand, if the Duration value of the received frame is not 0, the control unit 2 refers to the information of the transmission right acquisition communication station management unit that estimates and determines the transmission right acquisition communication station (step S204).
In the transmission right acquisition communication station management unit 3, if there is already information related to the transmission right acquisition communication station, that is, information that can determine the transmission right acquisition communication station, the control unit 2 proceeds with necessary processing for the received frame based on that information. Is instructed (step S203). In the transmission right acquisition communication station management unit 3, if there is no information about the transmission right acquisition communication station, that is, information that can identify the transmission right acquisition communication station (step S204: NO), the transmission right acquisition is performed according to the type of the received frame. It is determined whether a communication station can be specified.

  A specific transmission right acquisition communication station determination method is as follows. If the received frame is an ACK (BA) frame (step S205: YES), it can be considered that a reply frame to the DATA frame has been received, so that the destination communication station of the received frame can be determined to be a transmission right acquisition communication station (step S206). This determination information is held only for the duration period of the received frame (step S207). When the duration period ends, the transmission right acquisition communication station information is deleted from the memory.

  Next, if the received frame is CTS (step S208: YES), it is confirmed whether or not information on transmission right acquisition communication station candidates is already held in the memory (step S209). If the destination communication station of the received CTS frame is already stored in the memory as a candidate for a transmission right acquisition communication station (step S210), it is determined that the destination communication station of the CTS frame is a transmission right acquisition communication station (step S210). S206).

  On the other hand, if the destination communication station of the CTS frame is not stored in the memory as a transmission right acquisition communication station candidate in the memory, the destination communication station of the CTS frame is a transmission right acquisition communication station candidate. Store in the memory (step S211). If no frame is received within the period T, the stored information is deleted (step S212).

  Next, if the received frame is RTS (step S213: YES), it is confirmed whether or not the information regarding the candidate for the transmission right acquisition communication station is already held in the memory (step S214). If the transmission source communication station of the received RTS frame is already stored in the memory as a candidate for the transmission right acquisition communication station (step S215: YES), the transmission source communication station of the RTS frame is a transmission right acquisition communication station. It is determined (step S220). On the other hand, if the transmission source communication station of the RTS frame is not stored in the memory as a transmission right acquisition communication station candidate in the memory, the transmission source communication station of the RTS frame is a transmission right acquisition communication station candidate. And stored in the memory (step S216). If no frame is received within the period T, the stored information is deleted (step S217).

Next, if the received frame is a DATA frame (step S218: YES), and if the frame length is larger than RTS_Threshold (step S219: YES), the transmission source communication station is a transmission right acquisition communication station. It is determined (step S220).
In the IEEE802.11 protocol, when transmitting a Data frame larger than RTS_Threshold, it is necessary to exchange RTS / CTS in advance. Therefore, if a Data frame larger than RTS_Threshold is received, the above RTS / CTS exchange is correctly performed. Can be judged. Therefore, if a Data frame larger than RTS_Threshold is received, it can be determined that the transmission source communication station is a transmission right acquisition communication station.

  On the other hand, if the frame length of the received data is smaller than the RTS_Threshold, it is confirmed whether or not the information regarding the transmission right acquisition communication station candidate is already held in the memory as in the case of receiving the RTS frame (step S214). If the transmission source communication station of the received Data frame is already stored in the memory as a candidate for the transmission right acquisition communication station, it is determined that the transmission source communication station of the Data frame is a transmission right acquisition communication station (step S220). . Then, the information of the transmission right acquisition communication station is held only for the duration period of the received frame (step S221). On the other hand, if the transmission source communication station of the Data frame is not stored in the memory as a candidate for the transmission right acquisition communication station in the memory, the transmission source communication station of the Data frame is a candidate for the transmission right acquisition communication station. And stored in the memory (step S216).

  Next, if the received frame is a BAR (BA Request) frame (step S222: YES), it is determined that the transmission source transmission station of the received frame is a transmission right acquisition communication station (step S223).

  Next, a frame sequence indicating the communication operation of cell A when radio terminal WT13 is receiving interference from adjacent cell B in cell A shown in FIG. 1 will be described. Here, an example will be described in which cell station A1 accommodates data addressed to wireless terminals WT11-WT13 and transmits data frames addressed to wireless terminals WT11-WT13 within the same TXOP period in cell A. 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. An example where no interference is received will be described.

FIG. 5 is a time chart showing timings 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 ).

  When receiving the RTS frame from the base station device AP1, the wireless terminal WT12 records in the transmission right acquisition communication station management unit 3 that the base station device 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. When receiving the RTS frame from the base station apparatus AP1, the wireless terminal WT11 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 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 ). 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. Also, the wireless terminal WT11 records in the transmission right management unit 3 that the base station apparatus AP1 that is the destination of the received BA frame is a transmission right acquisition communication station.

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 ). At this time, 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 detected result, the wireless 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.

  6 to 8 are time charts showing timings when a transmission right acquisition communication station is estimated and specified by receiving a BAR frame, a DATA frame, and a CTS frame, respectively. The detailed operation shown in FIGS. 6 to 8 is the same as the operation shown in FIG.

FIG. 9 is a time chart showing the 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 ).

  When receiving the RTS frame from the base station device AP1, the wireless terminal WT12 records in the transmission right acquisition communication station management unit 3 that the base station device 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. When receiving the RTS frame from the base station apparatus AP1, the wireless terminal WT11 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 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 ). 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. While the wireless terminal WT11 is transmitting the BA frame addressed to the base station device AP1, the wireless terminal WT13 does not receive interference.

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 ). At this time, 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. In addition, the wireless terminal WT13 records in the transmission right management unit 3 that the base station device AP1 is a candidate for a transmission right acquisition communication station. Then, the timer is moved with T as the period for holding this information. Since the received frame is RTS, the length of the timer T is set as SIFS + CTS length + SIFS 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 ).

If wireless terminal WT13 can correctly receive the CTS frame of WT12, wireless terminal WT13 determines that destination terminal AP1 of the CTS frame is a transmission right acquisition communication station. Even if the wireless terminal WT13 cannot receive the CTS frame of the WT12 due to, for example, the WT13 and the WT12 being located at a distance where the carrier cannot be sensed with each other, the wireless terminal WT13 again receives the transmission right acquisition communication station candidate AP1 within the timer T. When the frame is received, it is determined that AP1 is a transmission right acquisition communication station. 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 ). At this time, 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 flowchart showing a processing operation for estimating or determining the transmission right acquisition communication station of the wireless communication apparatus in the system in which the RD method in the embodiment is effective. When the wireless communication apparatus receives a frame (step S301), it determines whether the Duration value of the received frame is 0 (step S302). When the Duration value is 0, the TXOP period ends, so that it is not necessary to perform estimation / determination of the transmission right acquisition communication station, and the necessary processing for the received frame is performed (step S303).

  On the other hand, if the Duration value of the received frame is not 0 (step S302: NO), the control unit 2 refers to the information of the transmission right acquisition communication station management unit that estimates and determines the transmission right acquisition communication station. In the transmission right acquisition communication station management unit 3, if there is already information related to the transmission right acquisition communication station, that is, information that can determine the transmission right acquisition communication station, the control unit 2 proceeds with necessary processing for the received frame based on that information. To give instructions. If the transmission right acquisition communication station management unit 3 does not already have information on the transmission right acquisition communication station, that is, information that can identify the transmission right acquisition communication station, can the transmission right acquisition communication station be identified according to the type of received frame? It is determined whether or not (step S304).

  A specific transmission right acquisition communication station determination method is as follows. If the received frame is RTS (step S305: YES), it is confirmed whether or not the information regarding the candidate for the transmission right acquisition communication station is already held in the memory (step S306). If the transmission source communication station of the received RTS frame is already stored in the memory as a candidate for the transmission right acquisition communication station (step S307: YES), the transmission source communication station of the RTS frame is a transmission right acquisition communication station. It is determined (step S308). This determination information is held only for the duration period of the received frame (step S309).

  On the other hand, if the transmission source communication station of the RTS frame is not stored in the memory as a candidate for the transmission right acquisition communication station in the memory (step S307: NO), the transmission source communication station of the RTS frame acquires the transmission right. The communication station candidate is stored in the memory (step S310). If no frame is received within the period T, the stored information is deleted (step S311).

  Next, when the received frame is any one of DATA, BA (ACK), BAR, and CTS frame (step S312: YES), whether or not information related to a candidate for a transmission right acquisition communication station is already held in the memory. Is confirmed (step S313). If already stored in the memory as a transmission right acquisition communication station candidate (step S313: YES), either the transmission source communication station or the destination communication station of the received frame that matches the stored communication station information is transmitted. It is inferred that it is an acquisition communication station (step S314).

  Next, if the source information or the destination communication station is included in the retained information (step S315: YES), if the RD method is valid, the transmission right acquisition communication station is determined only by receiving the one frame. Since it is difficult, both the communication stations are registered as potential candidates for the transmission right acquisition communication station (step S316). This determination information is held only for the duration period of the received frame (step S317). It is assumed that a response is made to a call that has a call within the same TXOP section from a promising candidate of the transmission right acquisition communication station.

  FIG. 11 is a time chart showing 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 ). At this time, when the radio terminal WT12 receives an RTS frame that is not addressed to itself from the base station apparatus AP1, the radio station WT12 determines that the base station apparatus AP1 that is the transmission source of the RTS frame is a transmission right acquisition communication station. Record in part 3. 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. When receiving the RTS frame from the base station device AP1, the wireless terminal WT11 records in the transmission right acquisition communication station management unit 3 that the base station device AP1 that is the transmission source of the RTS frame 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. The wireless terminal WT13 can correctly receive the data frame transmitted from the wireless terminal WT11 to the base station device AP1.

The wireless terminal WT13 sets the period indicated by the sustained use period information included in the received frame as the NAV period, and does not transmit the frame in the corresponding NAV period.
Further, the wireless terminal WT11 and the base station device AP1 record in the transmission right acquisition communication station management unit 3 that they are candidates for the 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. At this time, the wireless terminal WT13 knows that the transmission source communication station and the destination communication station of the received BA (or ACK) frame are candidates for the transmission right acquisition communication station in the wireless terminal WT13, and the wireless terminal WT11 And base station apparatus AP1 records in the transmission right acquisition communication station management part 3 as an influential candidate of a transmission right acquisition communication station. If there is a call from an influential candidate of the transmission right acquisition communication station in the same TXOP section, it responds to it. Thus, even if two or more communication stations are registered as potential candidates for a transmission right acquisition communication station, for example, WT11 already knows that AP1 is a transmission right acquisition communication station. This is because it is unlikely that there is a call from WT 11 within the same TXOP section.

Next, the base station device AP1 transmits an RTS frame whose destination is the wireless terminal WT13 (time t ₁₂₇ ). 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 detects that the RTS frame received from the base station device AP1 is addressed to itself and that the AP1 is a strong candidate for the transmission right acquisition communication station, regardless of whether or not it is in the NAV period. The CTS frame is transmitted to the base station device AP1 (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 above, even when the device itself is not involved in frame transmission / reception, the transmission right acquisition communication station can be specified based on the type of reception frame and the transmission / reception communication station of the reception frame. In some cases, the transmission right acquisition communication station can be specified when one frame is correctly received. In some cases, it may be necessary to receive more than one frame. By estimating and specifying the transmission right acquisition communication station in this way, 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, Even if the transmission right acquisition communication station cannot be grasped, it is possible to guess which wireless communication device is the transmission right acquisition communication station after the interference is not received.

  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.

  In the above-described embodiment, the time chart when the base station device AP1 becomes a transmission right acquisition communication station has been shown and described. However, the present invention is not limited to this, and the wireless terminals WT11 to WT13 become transmission right acquisition communication stations. May be.

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.

  As mentioned above, although embodiment of this invention has been described with reference to drawings, the said embodiment is only the illustration of this invention, and it is clear that this invention is not limited to the said embodiment. is there. Accordingly, additions, omissions, substitutions, and other changes of the components may be made without departing from the technical idea and scope of the present invention.

  The present invention can be applied to applications in which it is indispensable to suppress retransmission processing without responding to a request from a transmission right acquisition communication station.

AP1, AP2, AP ... base station device, WT11, WT12, WT13, WT21, WT
... wireless terminal, 1 ... wireless communication unit, 2 ... control unit, 3 ... transmission right acquisition communication management unit, 4 ... control unit

Claims (2)

A wireless communication device that operates as the communication station by applying an RD protocol that permits a transmission right acquisition communication station to transmit data in the reverse direction when a plurality of communication stations perform wireless communication using the same frequency band. ,
The received frame is
In the case of an RTS frame, it is determined whether or not determination result information about the communication station is already held. If not, it is determined that the transmission source communication station may be a transmission right acquisition communication station. If the determination result information is retained and the determination result information is deleted and retained if no frame is received within a predetermined period, the transmission source communication station is a transmission right acquisition communication station. Determining, and holding the determination result information only for the sustained use period of the frame,
In any of the BAR frame, the BA frame, the DATA frame, and the CTS frame, it is determined whether or not the determination result information about the communication station is already held. The station determines that there is a possibility of a transmission right acquisition communication station, and if the determination result information is held only for the duration of the frame, and the transmission source or destination communication station acquires the transmission right. A transmission right for determining a communication station, specifying the communication station that acquired the transmission right by holding the determination result information only for the period of continuous use of the frame, and holding the determination result information regarding the specified communication station Acquired communication station management department,
A control unit that determines whether or not to transmit a response frame based on the determination result information related to the communication station that has acquired the transmission right held in the transmission right acquisition communication station management unit. Communication device. When a plurality of communication stations perform wireless communication using the same frequency band, the wireless communication apparatus that operates as the communication station applies a RD protocol that allows the transmission right acquisition communication station to transmit data in the reverse direction. A communication method,
The received frame is
In the case of an RTS frame, it is determined whether or not determination result information about the communication station is already held. If not, it is determined that the transmission source communication station may be a transmission right acquisition communication station. If the determination result information is retained and the determination result information is deleted and retained if no frame is received within a predetermined period, the transmission source communication station is a transmission right acquisition communication station. Determining, and holding the determination result information only for the sustained use period of the frame,
In any of the BAR frame, the BA frame, the DATA frame, and the CTS frame, it is determined whether or not the determination result information about the communication station is already held. The station determines that there is a possibility of a transmission right acquisition communication station, and if the determination result information is held only for the duration of the frame, and the transmission source or destination communication station acquires the transmission right. A transmission right for determining a communication station, specifying the communication station that acquired the transmission right by holding the determination result information only for the period of continuous use of the frame, and holding the determination result information regarding the specified communication station Acquisition communication station administrative step,
A control step of determining whether or not to transmit a response frame based on the determination result information regarding the communication station that has acquired the transmission right held by the transmission right acquisition communication station management step. Communication method.

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