Access point device and terminal device

Abstract

According to the present invention, prior to data transmission in a millimeter wave band, RTS is transmitted in a microwave band, and CTS is transmitted in the millimeter wave band. Thus, information relating to subsequent data transmission is provided in each frequency band.

Description

Access point device, terminal device

[0001] The present invention relates to an access point device and a terminal device. This application claims priority to Japanese Patent Application No. 2025-047659, filed in Japan on March 24, 2025, the contents of which are incorporated herein by reference.

[0002] The IEEE (The Institute of Electrical and Electronics Engineers Inc.) is continuously working on updating the IEEE 802.11 wireless LAN standard to increase the speed of wireless LAN (Local Area Network) communication and improve frequency utilization efficiency. Wireless LANs can perform wireless communication using frequency bands that do not require permission (licenses) from countries or regions (unlicensed bands). For personal use such as in homes, wireless internet access from within homes has become possible by including wireless LAN access point functionality in line termination equipment for connecting to WAN (Wide Area Network) lines to the internet, or by connecting wireless LAN APs (Access Points, also called base station equipment) to line termination equipment. As a result, wireless LAN STAs (Station, also called terminal equipment), such as smartphones and personal computers, can connect to wireless LAN APs and access the internet.

[0003] Amid the continuous specification updates as described above, the standard formulation of IEEE 802.11ax was completed in 2021, and wireless LAN devices conforming to this standard, as well as communication devices such as smartphones and personal computers equipped with such devices, have appeared on the market as Wi-Fi 6 (registered trademark, a designation for IEEE 802.11ax-compliant products certified by Wi-Fi Alliance) compatible products. Then, as a successor standard to IEEE 802.11ax, the formulation of the IEEE 802.11be standard was completed in 2024, and communication devices conforming thereto are certified as Wi-Fi 7 (registered trademark, a designation for IEEE 802.11be-compliant products certified by Wi-Fi Alliance) compatible products. Furthermore, discussions regarding its successor standard, IEEE 802.11bn, are currently ongoing.

[0004] The above-mentioned standards are for communication using frequency bands called so-called microwave bands, such as the 2.4 GHz band, 5 GHz band, and 6 GHz band. Separately from these, wireless LAN standards for communication using a higher frequency 60 GHz band, which is a so-called millimeter wave frequency band, have also been formulated. The first of these to be formulated was IEEE 802.11ad (formulated in 2013), and IEEE 802.11ay has also been formulated as its successor standard (formulated in 2021).

[0005] The millimeter-wave band exhibits greater absorption by oxygen and higher spatial propagation loss and directivity compared to the microwave band due to its shorter wavelength. However, both IEEE 802.11ad and IEEE 802.11ay utilize a very wide bandwidth of 2.16 GHz per channel, making them suitable standards for high-speed transmission. Furthermore, IEEE 802.11ay incorporates technologies to achieve higher speeds than IEEE 802.11ad, such as channel bonding, which combines and uses multiple channels simultaneously, and MIMO (Multi-Input Multi-Output), which transmits multiple streams simultaneously using multiple antennas. To ensure transmission characteristics in the millimeter-wave band, which has frequency characteristics such as large spatial propagation loss and high directivity, beamforming (sector selection) technology is incorporated in both IEEE 802.11ad and IEEE 802.11ay.

[0006] Furthermore, in addition to IEEE 802.11bn, which is currently under discussion for standardization as described above, consideration has also begun for a standard that uses millimeter-wave wireless transmission in conjunction with it. This standard, based on IEEE 802.11bn which uses the microwave band, will perform multilink transmission (transmission using multiple different frequency bands) in both the microwave and millimeter-wave bands, and is currently being considered by the IEEE Study Group (SG) called IMMW (Integrated MilliMeter Wave). The basic concept of IMMW is to use millimeter-wave wireless transmission in addition to IEEE 802.11bn, and within the IMMW SG, a proposal has been made to perform control for millimeter-wave transmission in the microwave band (Non-Patent Literature 1).

[0007] Non-Patent Document 1 deals with RTS (Request to Send) and CTS (Clear to Send), which are control signals that are typically transmitted and received prior to data transmission on a data transmission channel. By having surrounding STAs (Stationary Terminals) receive these control signals and recognize that data transmission is about to take place on the channel, it is possible to prevent data frame collisions (hidden terminal problem) that occur when surrounding STAs start data transmission separately during the data transmission. Regarding such RTS and CTS, Non-Patent Document 1 proposes a configuration in which RTS and CTS are transmitted and received in the microwave band prior to data transmission in the millimeter wave band (Figure 1).

[0008] Figure 1 shows the types of signal frames transmitted in each frequency band, with the microwave band denoted as Sub 7GHz and the millimeter-wave band as mmWave. However, the shaded NAV(RTS) 105 and NAV(CTS) 106 do not represent signal frames, but rather transmission prohibition periods called NAV (Network Allocation Vector). RTS and CTS each contain information about the planned channel occupancy time, and by setting the NAV in the surrounding STAs based on this planned occupancy time information and suspending communication using the same channel during that time, data frame collisions can be avoided. Here, NAV(RTS) 105 in Figure 1 represents the NAV set based on the information contained in RTS 101, and NAV(CTS) 106 represents the NAV set based on the information contained in CTS 102.

[0009] As shown in Figure 1, data frame 103 is a frame transmitted from AP to STA1 using the millimeter wave band, and BA 104 is a block acknowledgment transmitted from STA1, which has received data frame 103, to AP. RTS 101 and CTS 102, which are transmitted prior to these, would normally be transmitted in the same millimeter wave band as data frame 103 and BA 104, but Non-Patent Literature 1 describes a configuration in which these control signals are transmitted in the microwave band. This approach aims to avoid the hidden terminal problem by transmitting RTS 101 and CTS 102 in the microwave band, thereby delivering them to a wide range of STAs (Other STAs in Figure 1) while using beamforming technology to ensure the best possible transmission characteristics in millimeter-wave transmission. In this way, while RTS 101 and CTS 102 are transmitted in the microwave band, NAV(RTS) 105 and NAV(CTS) 106 are set in the millimeter-wave band, and data frames 103 and BA 104 are transmitted. This is made possible by including information in RTS 101 and CTS 102 indicating that the channels used for transmitting data and BA are millimeter-wave band channels.

[0010] IEEE802.11-24 / 0096r0, Jan. 2024

[0011] In the method described in Non-Patent Literature 1 shown in Figure 1, RTS and CTS for data transmission in the millimeter-wave band are transmitted in the microwave band. The channel used for transmitting these RTS and CTS in the microwave band is considered to be the primary channel in the microwave band of the relevant BSS (Basic Service Set). The primary channel is the channel used for transmitting all wireless frames in the relevant frequency band of the BSS. By using the primary channel in the microwave band, it is considered that RTS and CTS can be delivered to a wide range of surrounding STAs (such as Other STAs in Figure 1) that are not involved in data transmission within the relevant BSS.

[0012] However, since the primary channel is set for each BSS, in adjacent BSSs that have a communication area that overlaps with the BSS in question and have a different primary channel, there may be STAs that cannot receive the RTS and CTS transmitted by the BSS in question. In such cases, while a data frame is being transmitted in the BSS in question, an STA in an adjacent BSS that cannot receive the RTS and CTS from the BSS in question may transmit a data frame, resulting in a hidden terminal problem where data frames collide.

[0013] The access point device and terminal device according to the present invention, which solve the above-mentioned problems, are as follows.

[0014] (1) That is, a wireless access point device according to one aspect of the present invention is an access point device that performs wireless communication with a terminal device using at least a first frequency band and a second frequency band, wherein in a downlink transmission in which the access point device transmits a first data frame to the terminal device, prior to transmitting the first data frame, it transmits a request to transmit (RTS) frame in the first frequency band, receives a acknowledgment to transmit (CTS) frame in at least the second frequency band, and transmits the first data frame in the second frequency band.

[0015] (2) In addition, in an uplink transmission to receive a second data frame from a terminal device, a wireless access point device according to one aspect of the present invention receives a request to transmit (RTS) frame in the first frequency band prior to receiving the second data frame, transmits a acknowledgment to transmit (CTS) frame in at least the second frequency band, and receives the second data frame in the second frequency band from the terminal device.

[0016] (3) In addition, in a wireless access point device according to one aspect of the present invention, the first frequency band is 10 GHz or less, and the second frequency band is 30 GHz or more.

[0017] (4) Furthermore, a wireless access point device according to one aspect of the present invention includes in the first frequency transmission request (RTS) frame information indicating the second frequency band and the channel used in the second frequency band, and information indicating two occupancy times.

[0018] (5) Furthermore, a wireless access point device according to one aspect of the present invention includes in the received Transmit Request (RTS) frame information indicating the second frequency band and the channel used in the second frequency band, and information indicating two occupancy times.

[0019] (6) In addition, a wireless access point device according to one aspect of the present invention receives a transmit acknowledgment (CTS) frame in both the first frequency band and the second frequency band during downlink transmission.

[0020] (7) In addition, a wireless access point device according to one aspect of the present invention transmits a transmission acknowledgment (CTS) frame in both the first frequency band and the second frequency band during the uplink transmission.

[0021] (8) Another aspect of the present invention is a terminal device that performs wireless communication with an access point device using at least a first frequency band and a second frequency band, wherein in an uplink transmission in which the terminal device transmits a first data frame to the access point device, prior to transmitting the first data frame, it transmits a request to transmit (RTS) frame in the first frequency band, receives a acknowledgment to transmit (CTS) frame in at least the second frequency band, and transmits the first data frame in the second frequency band.

[0022] (9) Furthermore, in a downlink transmission to receive a second data frame from the access point device, the terminal device receives a request to transmit (RTS) frame in the first frequency band prior to receiving the second data frame, transmits a acknowledgment to transmit (CTS) frame in at least the second frequency band, and receives the second data frame in the second frequency band from the access point device.

[0023] (10) In addition, in a terminal device according to one aspect of the present invention, the first frequency band is 10 GHz or less, and the second frequency band is 30 GHz or more.

[0024] (11) Furthermore, a terminal device according to one aspect of the present invention includes in the transmitted request for transmission (RTS) frame information indicating the second frequency band and the channels used in the second frequency band, and information indicating two occupancy times.

[0025] (12) Furthermore, a terminal device according to one aspect of the present invention includes in the received Transmit Request (RTS) frame information indicating the second frequency band and the channel used in the second frequency band, and information indicating two occupancy times.

[0026] (13) In addition, a terminal device according to one aspect of the present invention receives a transmit acknowledgment (CTS) frame in both the first frequency band and the second frequency band during the uplink transmission.

[0027] (14) In addition, a terminal device according to one aspect of the present invention transmits a transmission acknowledgment (CTS) frame in both the first frequency band and the second frequency band during downlink transmission.

[0028] (15) Furthermore, a terminal device according to one aspect of the present invention is a terminal device that uses a first frequency band and a second frequency band, and when an access point device that does not directly communicate wirelessly with the terminal device and another terminal device communicate wirelessly, the access point device and the other terminal device each receive at least one frame of either a request to transmit (RTS) frame transmitted in the first frequency band or an acknowledgment to transmit (CTS) frame transmitted in the second frequency band, and based on information indicating the occupancy time contained in at least one of the received request to transmit (RTS) frames or acknowledgment to transmit (CTS) frames, they suspend their own transmission in the second frequency band for the duration of the occupancy time.

[0029] According to the access point device and terminal device of the present invention, in a wireless communication system that performs multilink transmission in the microwave band and millimeter wave band, the occurrence of hidden terminal problems caused by terminal devices in adjacent BSSs can be suppressed.

[0030] This figure shows an example of avoiding the hidden terminal problem using RTS and CTS in an IMMW system. This figure shows an example of the PPDU, RTS, and CTS configuration in a wireless LAN system. This figure shows an example of avoiding the hidden terminal problem using RTS and CTS in a wireless LAN system. This figure shows an example of the BSS and channel configuration in a wireless communication system according to one aspect of the present invention. This figure shows an example of avoiding the hidden terminal problem using RTS and CTS according to one aspect of the present invention. This figure shows an example of the RTS and CTS configuration according to one aspect of the present invention. This block diagram shows an example of the AP configuration according to one aspect of the present invention. This block diagram shows an example of the STA configuration according to one aspect of the present invention. This figure shows an example of the RTS configuration according to one aspect of the present invention. This figure shows an example of avoiding the hidden terminal problem using RTS and CTS according to one aspect of the present invention. This figure shows an example of the CTS configuration according to one aspect of the present invention.

[0031] In this embodiment, the wireless communication system uses millimeter-wave wireless transmission in addition to IEEE 802.11bn, and targets IMMW, which performs multilink transmission in the microwave and millimeter-wave bands. Therefore, the following explanation will use an example that assumes IEEE 802.11bn. However, since IEEE 802.11bn is currently under standardization, the examples of IEEE 802.11bn frame configurations shown in this embodiment are merely assumptions at this time.

[0032] The wireless communication system in this embodiment comprises an AP (Access Point, also referred to as a base station device) and one or more STAs (Station, also referred to as a terminal device). This is also called a Basic Service Set (BSS), and the APs and STAs within the BSS communicate based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance). Each device is capable of transmitting multiple types of frames (communication frames) with a common frame format and is also called a wireless communication device. The frame is defined by a physical (PHY) layer, a medium access control (MAC) layer, and a logical link control (LLC) layer.

[0033] The PHY layer frame is called a Physical Protocol Data Unit (PPDU), and in IEEE 802.11bn, a configuration like that shown in Figure 2(1) is assumed for the PPDU. L-STF, L-LTF, and L-SIG included in the format in Figure 2(1) are reference signals and control signals for signal detection and synchronization, acquisition of channel information for data demodulation, and acquisition of control information for data demodulation, respectively. These are called legacy preambles and are preambles used in IEEE 802.11 compliant devices prior to IEEE 802.11bn. Furthermore, the RL-SIG is a preamble used in IEEE 802.11ax and later, the U-SIG is a preamble used in IEEE 802.11be and later, and the UHR-SIG and subsequent signals are preambles and data used for IEEE 802.11bn. In addition, the legacy preamble, RL-SIG, U-SIG, and the subsequent STF and LTF signals are collectively called the PHY header.

[0034] A MAC layer frame is called a MAC Protocol Data Unit (MPDU, or MAC layer frame) and consists of a MAC header containing information for signal processing in the MAC layer, a MAC Service Data Unit (MSDU, also called a frame body) which is a data unit processed in the MAC layer, and a Frame Check Sequence (FCS) which checks whether the frame is error-free.

[0035] Frame types in the MAC layer are broadly classified into three categories: management frames, which manage the connection status between devices; control frames, which manage the communication status between devices; and data frames, which contain the actual transmitted data. Each of these categories is further classified into multiple subframe types. Management frames include beacon frames, probe request frames, probe response frames, authentication frames, association request frames, and association response frames. Control frames include acknowledgment (Ack or ACK) frames, block acknowledgment (BA or BlockAck) frames, request to send (RTS) frames, clear to send (CTS) frames, and trigger frames. BlockAck can send acknowledgments (reception completion notifications) to multiple MPDUs. Data frames include data frames and polling (CF-poll) frames. Each device can recognize the frame type and subframe type of a received frame by reading the contents of the frame control field included in the MAC header.

[0036] A beacon frame, which is one of the management frames, includes a field that indicates the beacon transmission period (Beacon interval) and the SSID. APs periodically broadcast beacon frames within the BSS, and STAs can recognize nearby APs by receiving these beacon frames. After receiving a beacon frame and recognizing an AP, STAs perform authentication and association procedures with the AP, and through these processes, they connect with the AP. After the connection is established, the AP and STAs then perform actual data transmission.

[0037] In IEEE 802.11 systems, Distributed Coordination Function (DCF), Point Coordination Function (PCF), and the extended Hybrid Coordination Function (HCF) are defined as media access methods. This document outlines the transmission operation based on DCF. In DCF, APs and STAs perform Carrier Sense (CS) to check the usage status of radio channels around their devices prior to communication. If a signal with a received power higher than a predetermined Clear Channel Assessment level (CCA level) is received on the radio channel, transmission of the frame on that radio channel is postponed. The state in which a signal with a received power of CCA level or higher is detected on the radio channel is called a Busy state, and the state in which no signal with a received power of CCA level or higher is detected is called an Idle state. During the carrier sense period, transmission is postponed if the state is Busy, and transmission proceeds if the state is Idle. However, a mechanism is in place to avoid frame collisions caused by other transmitting stations transmitting frames at the same time, by waiting for a randomly set random backoff time before transmission begins.

[0038] However, relying solely on the above transmission operation based on DCF can lead to a problem known as the hidden terminal problem, where communication devices that cannot detect each other's signals due to distance or other reasons simultaneously begin data transmission, resulting in data frame collisions. To avoid this hidden terminal problem, a mechanism is provided to transmit and receive RTS and CTS prior to data transmission. The configurations of the RTS and CTS MPDUs in standards up to IEEE 802.11bn are shown in Figures 2(2) and 2(3), respectively. However, while the MPDU configuration is shown here, in actual transmission, legacy preambles and other elements are added to transmit the data as a PHY layer frame. As shown in Figure 2(2), the RTS MPDU consists of Frame Control for frame control, Duration indicating the time required to transmit and receive the data frame, RA (Receiver Address) indicating the address of the receiving side, TA (Transmitter Address) indicating the address of the transmitting side, and FCS. Furthermore, as shown in Figure 2(3), the MPDU of the CTS consists of Frame Control for frame control, Duration which indicates the time required to send and receive data frames, RA (Receiver Address) which indicates the address of the receiving side, and FCS. Here, the part other than FCS is the MAC header.

[0039] Figure 3 shows the basic operation of avoiding the hidden terminal problem using RTS and CTS. In Figure 3, Source represents the data frame sender, Destination represents the data frame receiver, and Others represents other communication devices. In Figure 3, the sender (Source) first confirms that no other communication devices are transmitting, waits for a period called DIFS (DCF Inter Frame Space, DIFS 301-1), and then transmits RTS 302. The receiver (Destination), upon receiving RTS 302, understands from the RA and TA information contained in RTS 302 that the sender (Source) is transmitting data to it, waits for a period called SIFS (Short Inter Frame Space, SIFS 303-1), and then transmits CTS 303. The sender (Source), upon receiving CTS 303, waits for another SIFS before transmitting data frame 305. Then, the receiving side (Destination), having received the data frame 305 without error, waits only for SIFS and then sends Ack 306 back to the transmitting side (Source).

[0040] Here, other communication devices (Others) besides the transmitting (Source) and receiving (Destination) devices first receive the RTS 302. Based on the RA and TA information contained in the RTS 302, they can understand that a data frame destined for a different communication device is being transmitted. Therefore, based on the Duration information also contained in the RTS 302, they set NAV 307-1 only for the duration specified, and refrain from transmitting data frames from themselves. Similarly, the CTS 303 also contains Duration information, so based on this information, they set NAV 307-2 only for the duration specified, and refrain from transmitting data frames from themselves. Furthermore, since the data frame 305 also contains frame length information, it is also possible to set NAV 307-3 after receiving this information. These NAVs remain set until the transmission of Ack306 is completed. This prevents the problem of other communication devices (Others) starting data transmission between the end of RTS302 transmission and the end of Ack306 transmission, which could cause collisions with the frames of the transmitting (Source) and receiving (Destination) devices. Once the transmission of Ack306 is completed and the series of data transmissions is finished, the NAVs set in the other communication devices (Others) are also released. After the period of DIFS301-2 has elapsed, and then the device that has acquired the right to transmit waits for a random waiting period called the Contention Window (CW308) before the device that acquired the right to transmit can transmit a signal. Since this behavior of refraining from transmission is similar to when the radio channel is determined to be busy by physical carrier sense, communication control by NAV is also called virtual carrier sense (virtual CS). The Duration values ​​included in RTS302 and CTS303 are different.

[0041] In this embodiment, the control using the above-described RTS and CTS is applied to IMMW (Integrated MilliMeter Wave), and a configuration is shown in which the RTS and CTS are transmitted in different frequency bands, particularly the microwave band and the millimeter wave band, in an IMMW that uses the millimeter wave band in addition to the microwave band. Here, an example of the BSS targeted in this embodiment is shown in Figure 4(1). In Figure 4(1), 401-1 and 401-2 represent APs, and 402-1, 402-2, 402-3, and 402-4 represent STAs, and an example is shown in which AP 401-1 and STAs 402-1 and 402-2 constitute one BSS (BSS 403-1), and AP 401-2 and STAs 402-3 and 402-4 constitute another BSS (BSS 403-2).

[0042] Figure 4(2) shows the relationship between the frequency bands used in BSS403-1 and BSS403-2, and the channels in each frequency band. The left side of Figure 4(2) represents the microwave band, and the right side represents the millimeter-wave band. The upper part of Figure 4(2) represents the frequency bands and channels used in BSS403-1, and the lower part represents the frequency bands and channels used in BSS403-2. In other words, BSS403-1 uses four channels in the microwave band, 404-1 to 404-4, and two channels in the millimeter-wave band, 405-1 to 405-2. BSS403-2 uses two channels in the microwave band, 406-1 to 406-2, and one channel in the millimeter-wave band, 407-1. In Figure 4(2), separate channel numbers are assigned for the sake of simplicity, but channels 404-3 and 406-1, channels 404-4 and 406-2, and channels 405-1 and 407-1 are the same channel. Thus, in BSS403-1 and BSS403-2, some channels are used in the microwave band and millimeter wave band, respectively. If simultaneous transmission occurs on the overlapping channels, the transmission frames will collide, resulting in the problem of incorrect reception. Such adjacent BSSs that use overlapping channels are sometimes called OBSS (Overlapping BSS). Here, channel 404-1 is the primary channel in the microwave band of BSS403-1, and channel 406-1 is the primary channel in the microwave band of BSS403-2. The primary channel is a channel determined for each BSS on which management frames such as beacons are transmitted, and each BSS's STA is configured to always transmit and receive on its own BSS's primary channel. In this embodiment, the microwave band refers to the frequency band of 10 GHz or less, and the millimeter wave band refers to the frequency band of 30 GHz or more. More specifically, the microwave band may be the 5 GHz or 6 GHz band, and the millimeter wave band may be the 60 GHz band.

[0043] Since IMMW is a system that additionally uses the millimeter wave band in addition to the microwave band, it is assumed that respective authentication procedures, connection procedures and the like are performed in the microwave band in BSS 403-1 and BSS 403-2, and more specifically, these procedures are performed on respective primary channels (channels 404-1, 406-1) of the microwave band. However, although beamforming (sector selection) is used in the millimeter wave band, beamforming (sector selection) using beacon frames is performed in both IEEE 802.11ad and IEEE 802.11ay. Although the primary channel is not described in the millimeter wave band of FIG. 4(2), in the present embodiment, it is assumed that optimal beamforming (sector selection) is performed on both the transmitting side and the receiving side by the mechanism used in IEEE 802.11ad and IEEE 802.11ay. After the beamforming (sector selection), transmission of data frames and the like is performed by using the formed beam or the selected sector on the transmitting side and the receiving side, respectively.

[0044] FIG. 5 is a diagram showing an example of frame transmission / reception and operations in the wireless communication system according to the present embodiment. In FIG. 5, the microwave band is denoted as Sub 7 GHz and the millimeter wave band is denoted as mmWave, respectively. An example of transmission frames and operations in respective frequency bands when downlink data transmission from AP 401-1 of BSS 403-1 to STA 402-1 is performed in the millimeter wave band is shown. However, NAV (RTS) 508-1 and NAV (CTS) 508-2 indicated by hatching are not signal frames, but represent NAV setting periods. Also, CW 505-1, 505-2, and 505-3 indicated by parallelograms are not signal frames, but represent contention windows indicating random waiting time until acquisition of the next transmission right.

[0045] As shown in Figure 5, when performing downlink transmission in the wireless communication system according to this embodiment, AP401-1 first confirms that no other communication devices are transmitting, waits for the duration of DIFS501-1, and then transmits RTS502 on channel 404-1 (Figure 4(2)), which is the primary channel of BSS403-1 among the microwave band channels. This transmission of RTS502 is performed using an omnidirectional antenna. Here, the configuration of the MPDU of RTS502 is shown in Figure 6(1)-1. As shown in Figure 6(1)-1, the RTS502 in this embodiment has a configuration in which frequency band and channel information (Band, Ch Info) is added to the RTS shown in Figure 2(2). This frequency band and channel information (Band, Ch Info) indicates the frequency band in which the subsequent data transmission will take place and the channels actually used for data transmission within that frequency band. In this embodiment, the frequency band information includes the millimeter-wave band, and the channel information includes channels 405-1 and 405-2 (Figure 4(2)). In addition, the Duration in Figure 6(1)-1 contains information indicating the period from the end of RTS 502 to the end of BA 507 in Figure 5, RA contains the address information of STA 402-1, and TA contains the address information of AP 401-1. By receiving this RTS 502, it can be determined that the subsequent data transmission will be performed from AP 401-1 to STA 402-1 using millimeter-wave channels 405-1 and 405-2 between the end of RTS 502 and the end of BA 507.

[0046] Furthermore, the MPDU of the RTS502 may have the configuration shown in Figure 6(1)-2. This configuration is the same as the MPDU shown in Figure 6(1)-1 but with the frequency band information removed. If all channels in the microwave and millimeter-wave bands are assigned channel numbers that allow them to be distinguished, then the frequency band information is not necessary, and it may be possible to reduce the amount of control information. Also, in both Figure 6(1)-1 and Figure 6(1)-2, the newly added control information, which is frequency band / channel information (Band, Ch Info) or channel information (Ch Info), is, for example, added immediately after frame control. However, it is not limited to this configuration, and may be added at any point between frame control and FCS. This is, for example, the configuration shown in Figure 6(1)-3. In the configuration shown in Figure 6(1)-3, the configuration from Frame Control to TA is the same as the RTS shown in Figure 2(2). Therefore, the information can be received by STAs other than the STA targeting IMMW in this embodiment, such as existing system STAs like IEEE 802.11ax and IEEE 802.11be. Thus, with the RTS configuration shown in Figure 6(1)-3, the RTS frame can be received by existing systems such as IEEE 802.11ax and IEEE 802.11be, albeit only up to a certain point, and the necessary information can be obtained.

[0047] Upon receiving the RTS 502, STA 402-1 understands that AP 401-1 will transmit data to itself using millimeter-wave channels 405-1 and 405-2 between the end of RTS 502 and the end of BA 507. Therefore, as shown in Figure 5, STA 402-1 waits only during SIFS 503-1 before sending back the CTS 504. However, since the CTS 504 is transmitted using millimeter-wave channels 405-1 and 405-2 specified in RTS 502, and is transmitted in the millimeter-wave band, it is transmitted using a beam or selected sector that has been formed in advance with AP 401-1, and AP 401-1 also receives it using a beam or selected sector that has been formed in advance. The same CTS 504 will be transmitted on both channels 405-1 and 405-2. The configuration of the MPDU for CTS 504 is shown in Figure 6(2). As shown in Figure 6(2), the CTS 504 in this embodiment has the same configuration as the CTS shown in Figure 2(3). The Duration of the CTS 504 contains information indicating the period from the end of the CTS 504 in Figure 5 to the end of the BA 507, and the RA contains the address information of STA 402-1. By receiving the CTS 504 transmitted on millimeter-wave channels 405-1 and 405-2, AP 401-1 can determine that STA 402-1 is capable of receiving data transmission on channels 405-1 and 405-2, and then proceeds to data transmission. Another STA receiving the CTS 504 can determine that data transmission to STA 402-1 will occur on millimeter-wave channels 405-1 and 405-2 between the end of the CTS 504 and the end of the BA 507.

[0048] In AP 401-1 that has received CTS 504, as shown in FIG. 5, after waiting only for SIFS 503-2, it transmits a data frame 506 addressed to STA 402-1. At this time, the data frame 506 is transmitted on millimeter-wave band channels 405-1 and 405-2, and it is assumed that the frame has a configuration as shown in, for example, FIG. 2(1). For the sake of simplifying the drawing, only one data frame 506 is illustrated in FIG. 5. In practice, however, different data (the Data portion in FIG. 2(1)) will be transmitted on each of channels 405-1 and 405-2. Furthermore, since the transmission is performed in the millimeter-wave band, similar to the case of CTS 504, the data frame 506 is also transmitted using a pre-formed beam or a selected sector between AP 401-1 and STA 402-1, and STA 402-1 also receives the data frame 506 using a pre-formed beam or a selected sector. Then, in STA 402-1 that has received the data frame 506, demodulation and decoding of the received signal are performed, and if the data is correctly received, after waiting only for SIFS 503-3, it returns a block acknowledgment BA 507 addressed to AP 401-1.

[0049] Through such an operation, between AP 401-1 and STA 402-1, RTS is exchanged in the microwave band and CTS is exchanged in the millimeter-wave band respectively, whereby transmission of a data frame from AP 401-1 and return of an acknowledgment from STA 402-1 in response to the data frame can both be performed in the millimeter-wave band respectively.

[0050] Next, we will show the operation of other STAs, etc., that are not involved in the transmission and reception of data frames, based on Figure 5. STA402-2 is an STA within BSS403-1, and as described above, RTS502 is transmitted using an omnidirectional antenna on microwave band channel 404-1, which is the primary channel in BSS403-1, so STA402-2 can also receive this RTS502. Based on the information from RTS502, STA402-2 can understand that the subsequent transmission between AP401-1 and STA402-1 will take place in the millimeter wave band, and therefore sets up NAV on millimeter wave band channels 405-1 and 405-2 for the period indicated as the Duration of RTS502. This is NAV508-1. After the end of the NAV508-1 period, that is, after the transmission between AP401-1 and STA402-1 is completed, the system waits for the duration of DIFS501-3, then enters the contention window CW505-2 period, which involves waiting for a random amount of time, before moving on to the next operation to acquire the right to transmit.

[0051] Thus, in the wireless communication system according to this embodiment, STA 402-2, which is located within BSS 403-1 where data transmission takes place but is not involved in the immediate data transmission, can set NAV 508-1 using RTS 502 transmitted by an omnidirectional antenna on the microwave primary channel 404-1 from AP 401-1 within BSS 403-1. This prevents STA 402-2 from starting separate transmissions while AP 401-1 and STA 402-1 are communicating. Of course, if STA 402-2 can receive the CTS 504 transmitted by STA 402-1, it is also possible to set NAV based on CTS 504. However, since CTS 504 is transmitted in the millimeter-wave band using a pre-formed beam or selected sector, it is difficult for all STAs widely scattered within the BSS to receive CTS 504. Therefore, setting NAV based on RTS on the microwave primary channel is more effective.

[0052] On the other hand, STAs (STA402-3, 402-4) located within BSS403-2, adjacent to BSS403-1 which performs data transmission, and which do not use the primary channel 404-1 in BSS403-1, cannot receive RTS502. Therefore, as shown in BSS403-2 in Figure 5, it is not possible to set up NAV (RTS) based on RTS502. Here, BSS403-2 in Figure 4(2) is configured not to use channels 404-1 and 404-2 used in BSS403-1, but this is not the only case. Even if BSS403-2 uses the same channels as BSS403-1, if their primary channels are different, it is not guaranteed that the RTS502 transmitted from AP401-1 of BSS403-1 can be received by the STAs located within BSS403-2, which can lead to the problem of not being able to set up NAV (RTS) based on RTS502. In contrast, since CTS 504 is transmitted in the millimeter-wave band using a pre-formed beam or selected sector, it does not reach all of the widely scattered STAs. However, because it is transmitted on millimeter-wave channels 405-1 and 405-2, it can be received by STAs in BSS 403-2 that use the same channel as channel 405-1 as channel 407-1. For example, STAs located in the direction from STA 402-1 to AP 401-1 or in the vicinity along its extension in Figure 4 (e.g., STAs 402-3 and 402-4) are in a positional relationship where CTS 504 can be received. These STAs can then understand from the information of CTS 504 that subsequent transmission between AP 401-1 and STA 402-1 will take place in the millimeter-wave band, and therefore set up NAV on millimeter-wave channel 407-1 for the period indicated as the Duration of CTS 504. This is NAV 508-2. After the end of the NAV508-2 period, that is, after the transmission between AP401-1 and STA402-1 is completed, the system waits for the duration of DIFS501-3, then enters the contention window CW505-3 period, which involves waiting for a random amount of time, before moving on to the next operation to acquire the right to transmit.

[0053] Thus, in the wireless communication system according to this embodiment, in STA 402-3 and 402-3 within BSS 403-2, which is adjacent to BSS 403-1 where data transmission takes place and uses a different primary channel than BSS 403-1, it is possible to set up NAV 508-2 based on CTS 504 transmitted in the millimeter wave band. This makes it possible to avoid situations where STA 402-3 and 402-3 start transmitting separately while AP 401-1 and STA 402-1 are communicating. Of course, if BSS 403-1 and BSS 403-2 use the same primary channel, it may be possible to receive RTS 502 within BSS 403-2 as well, and it will be possible to set up NAV (RTS) based on RTS 502. However, the primary channel is set for each BSS, and adjacent BSSs do not necessarily use the same primary channel. In such cases, even if the RTS is transmitted in the microwave band, setting the NAV based on the RTS transmitted in the adjacent BSS is difficult, and it can be said that setting the NAV based on the CTS transmitted in the millimeter-wave band channel used for actual data transmission is more effective.

[0054] Through the operations described above, in the downlink transmission of the wireless communication system according to this embodiment, RTS can be transmitted in the microwave band primarily for the purpose of setting NAV in STAs within its own BSS, and CTS can be transmitted in the millimeter-wave band primarily for the purpose of setting NAV in STAs within adjacent BSSs. By receiving either RTS or CTS at the target STAs, the appropriate NAV can be set at each STA. As a result, when data transmission is performed in the millimeter-wave band in IMMW, either RTS or CTS can be received by surrounding STAs, including STAs within adjacent BSSs, thereby preventing the occurrence of the hidden terminal problem.

[0055] Here, Figure 7 shows the configuration of the AP constituting the wireless communication system according to this embodiment. As shown in Figure 7, the AP constituting the wireless communication system according to this embodiment consists of an upper layer 701, a communication control unit 702, wireless communication units 703 and 704, and antenna units 705 and 706. Of these, the communication control unit 702 consists of a MAC frame generation unit 707, a MAC control unit 708, a frequency band / channel control unit 709, and a MAC frame receiving unit 710. The MAC frame generation unit 707 consists of a data acquisition unit 711, a control information generation unit 712, a frequency band / channel information generation unit 713, and a duration information calculation unit 714. The MAC frame receiving unit consists of a data acquisition unit 715, a control information acquisition unit 716, a frequency band / channel information acquisition unit 717, and a duration information acquisition unit 718. In this embodiment of the wireless communication system, since it targets IMMW, the AP is configured to transmit and receive signals in both the microwave and millimeter-wave frequency bands. Therefore, the wireless communication unit and antenna unit are configured to have two each for microwave and millimeter-wave transmission / reception. In the AP shown in Figure 7, the wireless communication unit 703 and antenna unit 705 are for microwave transmission and reception, and the wireless communication unit 704 and antenna unit 706 are for millimeter-wave transmission and reception. Of these, the wireless communication unit 703 consists of a physical frame generation unit 719, a wireless transmission unit 720, a physical frame receiving unit 721, and a wireless receiving unit 722. The wireless communication unit 704, which uses the same configuration as the wireless communication unit 703 but operates in a different frequency band, consists of a physical frame generation unit 723, a wireless transmission unit 724, a physical frame receiving unit 725, and a wireless receiving unit 726. Note that the AP shown in Figure 7 is shown as AP401-1 in Figure 5.

[0056] The operation of each part of the AP shown in Figure 7 will be explained based on the transmission and reception of frames in Figure 5. In the AP shown in Figure 7, first, carrier sensing is performed to check the usage status of wireless channels around the device and to confirm that no other communication devices are transmitting. In this embodiment, this operation is performed in the microwave band and is carried out by the antenna unit 705 and the wireless receiver unit 722. The electric field strength of the received signal received by the antenna unit 705 is measured by the wireless receiver unit 722. If the electric field strength exceeds a predetermined clear channel evaluation level, transmission is refrained from as it is assumed that another communication device is transmitting. If it does not exceed the predetermined clear channel evaluation level, it is assumed that no other communication devices are transmitting and the device waits for approximately the DIFS 501-1 period.

[0057] If carrier sensing determines that no other communication devices are transmitting, the AP shown in Figure 7 will transmit RTS 502 after the DIFS 501-1 period shown in Figure 5. In this case, RTS 502 is generated by the MAC frame generation unit 707. Specifically, the frame shown in Figure 6(1)-1 or (1)-2 is generated by the MAC frame generation unit 707, while Frame Control is generated by the control information generation unit 712, frequency band and channel information (Band, Ch Info) is generated by the frequency band and channel information generation unit 713, and Duration is generated by the Duration information calculation unit 714. In addition, RA contains the address information of the receiving side (STA402-1 in Figure 5), and TA contains the address information of the AP itself (AP401-1). These are generated from address information held in advance by the control information generation unit. Here, the frequency band and channel information (Band, Ch Info) generated by the frequency band and channel information generation unit 713 represents the frequency band and channel to which the CTS 504 and data frame 506 shown in Figure 5 are transmitted. In this embodiment, the frequency band information is millimeter wave band, and the channel information is channels 405-1 and 405-2 (Figure 4(2)). The duration information calculation unit 714 calculates the period from the end of RTS 502 to the end of BA 507 in Figure 5, and generates information indicating that period. Specifically, this period is calculated as the length of SIFS + CTS (CTS 504) + SIFS + data frame (data frame 506) + SIFS + BA (BA 507).

[0058] In this way, the information constituting the RTS 502, generated by the control information generation unit 712, the frequency band / channel information generation unit 713, and the duration information calculation unit 714, respectively, is arranged in the order shown in Figure 6(1) by the MAC frame generation unit 707, and an FCS is added to form a frame, which is then sent to the wireless communication unit via the MAC control unit 708. At this time, since the RTS 502 is a frame transmitted in the microwave band, the frequency band / channel control unit 709 controls it to transmit in the microwave band, and the RTS 502 is sent from the MAC control unit 708 to the wireless communication unit 703.

[0059] In the physical frame generation unit 719 within the wireless communication unit 703, the MAC frame sent from the communication control unit 702 is encoded, modulated, and OFDM signals are generated, a PHY header is added, and a physical frame is formed. This is then sent to the wireless transmission unit 720, where D / A conversion and frequency conversion for wireless transmission are performed, and the frame is transmitted wirelessly from the antenna unit 705. With this configuration, the AP401-1, which is compatible with IMMW, can transmit RTS frames in the microwave band as shown in Figure 6(1).

[0060] As shown in Figure 5, in response to the RTS 502 transmitted from AP 401-1, the CTS 504 is sent back from STA 402-1 in the millimeter-wave band. This CTS 504 is received by the antenna unit 706 in AP (Figure 7) and sent to the wireless communication unit 704. This received signal is converted into a digital signal by frequency conversion and A / D conversion in the wireless receiving unit 726 within the wireless communication unit 704. Then, demodulation and decoding are performed in the physical frame receiving unit 725 to extract the MAC frame of the CTS 504 as shown in Figure 6(2). This MAC frame of the CTS 504 is sent from the physical frame receiving unit 725 to the communication control unit 702, and then to the MAC frame receiving unit 710 within the communication control unit. Within the MAC frame receiving unit 710, in the configuration shown in Figure 6(2), Frame Control and RA are sent to the control information acquisition unit 716, and Duration is sent to the Duration information acquisition unit 718, and the respective information is acquired. In this embodiment, the CTS 504 is transmitted on millimeter-wave channels 405-1 and 405-2 (Figure 4(2)), and information indicating the frequency band and channel from which the CTS 504 was transmitted is sent to the frequency band / channel information acquisition unit 717. Based on this information, it can be determined that the STA 402-1 is capable of receiving data transmission on channels 405-1 and 405-2. Information on the channels that the STA 402-1 can receive is also sent to the frequency band / channel control unit 709 via the MAC control unit 708 and used for control during the next data frame transmission. In this embodiment, when transmitting and receiving in the millimeter-wave band, a pre-formed beam or selected sector is used. The operation of beam formation and sector selection will not be explained here, but in this embodiment, when transmitting and receiving in the millimeter-wave band in the AP 401-1, transmission and reception are performed using a pre-formed beam or selected sector.

[0061] Upon receiving the CTS 504, the AP (AP401-1) shown in Figure 7 then proceeds to data transmission to STA402-1. The data destined for STA402-1 is sent from the upper layer 701 to the data acquisition unit 711 of the MAC frame generation unit 707. Control information for constructing the MAC frame is generated in the control information generation unit 712, and the MAC frame generation unit 707 generates the MAC frame destined for STA402-1. This MAC frame is sent to the MAC control unit 708 and then to the wireless communication unit. The frequency band / channel control unit 709, which is aware of the frequency band and channel used for this data transmission, controls the transmission of the MAC frame to the wireless communication unit 704, which is the millimeter-wave wireless communication unit of the two wireless communication units. Then, the physical frame generation unit 723 within the wireless communication unit 704 performs encoding, modulation, and OFDM signal generation, adds a PHY header, and forms the physical frame. The signal is then sent to the wireless transmission unit 724, where D / A conversion and frequency conversion are performed for wireless transmission, and the signal is then transmitted wirelessly from the antenna unit 706.

[0062] After the transmission of this data frame, AP (AP401-1) shown in Figure 7 receives BA507, which is returned from STA402-1. Since BA507 is transmitted in the millimeter-wave band, it is received by the antenna unit 706, demodulated and decoded by the wireless communication unit 704, and acknowledgment information is sent to the MAC frame receiver. This acknowledgment information confirms that the data frame transmitted from AP401-1 was received correctly by STA402-1. With this AP configuration, it is possible to transmit RTS in the microwave band, receive CTS returned in the millimeter-wave band, and transmit data frames in the millimeter-wave band, enabling the operation shown in Figure 5.

[0063] On the other hand, the STA in this embodiment is represented by the configuration shown in Figure 8. As shown in Figure 8, the STA in this embodiment consists of an upper layer 801, a communication control unit 802, wireless communication units 803 and 804, and antenna units 805 and 806. The communication control unit 802 consists of a MAC frame generation unit 807, a MAC control unit 808, a frequency band / channel control unit 809, and a MAC frame receiving unit 810. The MAC frame generation unit 807 consists of a data acquisition unit 811, a control information generation unit 812, and a duration information calculation unit 813. The MAC frame receiving unit consists of a data acquisition unit 814, a control information acquisition unit 815, a frequency band / channel information acquisition unit 816, and a duration information acquisition unit 817. In the wireless communication system according to this embodiment, since it targets IMMW, the STA is configured to transmit and receive signals in both the microwave band and the millimeter-wave band. Therefore, the wireless communication unit and antenna unit are configured to have two each for microwave band transmission / reception and millimeter-wave band transmission / reception. In the STA shown in Figure 8, the wireless communication unit 803 and antenna unit 805 are for microwave band transmission / reception, and the wireless communication unit 804 and antenna unit 806 are for millimeter-wave band transmission / reception. Of these, the wireless communication unit 803 consists of a physical frame generation unit 818, a wireless transmission unit 819, a physical frame reception unit 820, and a wireless reception unit 821. The wireless communication unit 804, which uses the same configuration as the wireless communication unit 803 but operates in a different frequency band, consists of a physical frame generation unit 822, a wireless transmission unit 823, a physical frame reception unit 824, and a wireless reception unit 825. Furthermore, the configuration shown in Figure 8 is common to the STAs in STA402-1, 402-2, and BSS403-2 in Figure 5.

[0064] The operation of each part of the STA shown in Figure 8 will be explained based on the transmission and reception of frames in Figure 5, but first, the operation of STA 402-1 will be explained. In STA 402-1, first, the RTS 502 transmitted from AP 401-1 is received. Since this RTS 502 is transmitted in the microwave band, it is received by the antenna unit 805 and sent to the wireless communication unit 803. This received signal is converted into a digital signal by frequency conversion and A / D conversion in the wireless receiving unit 821 within the wireless communication unit 803, and then demodulated and decoded in the physical frame receiving unit 820 to extract, for example, the MAC frame of RTS 502 as shown in Figure 6(1)-1. This MAC frame of RTS 502 is sent from the physical frame receiving unit 820 to the communication control unit 802, and then to the MAC frame receiving unit 810 within the communication control unit. Within the MAC frame receiving unit 810, in the configuration shown in Figure 6(1)-1, Frame Control, RA, and TA are sent to the control information acquisition unit 8015, frequency band and channel information (Band, Ch Info) is sent to the frequency band and channel information acquisition unit 816, and Duration is sent to the Duration information acquisition unit 817, where the respective information is acquired. Based on this information, it can be understood that AP401-1 is attempting to transmit data to itself, and that it is requesting CTS transmission to this RTS 502 using the frequency band and channel indicated by the frequency band and channel information (Band, Ch Info). Of this information, the information regarding TA is also sent to the control information generation unit 812 of the MAC frame generation unit 807 via the MAC control unit 808 and is used for control during CTS transmission. Furthermore, frequency band and channel information (Band, Ch Info) is sent to the frequency band and channel control unit 809 via the MAC control unit 808, and information regarding duration is also sent to the duration information calculation unit 813 via the MAC control unit 808.

[0065] Upon receiving the RTS 502 in this manner, the STA 402-1 then proceeds to transmit the CTS. The CTS in this embodiment has a MAC frame as shown in Figure 6(2), and this MAC frame is generated by the MAC frame generation unit 807. Specifically, the Frame Control in Figure 6(2) is generated by the control information generation unit 812, and the Duration is generated by the Duration information calculation unit 813. The RA contains the address information of the STA 402-1 itself, which is generated from address information held in advance by the control information generation unit. The Duration information calculation unit 8013 calculates the period from the end of the CTS 504 in Figure 5 to the end of the BA 507, and generates information indicating that period. This period is specifically calculated as the length of SIFS + data frame (data frame 506) + SIFS + BA (BA 507), but the length of data frame (data frame 506) is determined from the Duration information obtained from RTS 502.

[0066] Thus, the information constituting the CTS 504, generated by the control information generation unit 812 and the Duration information calculation unit 813 respectively, is arranged in the order shown in Figure 6(2) by the MAC frame generation unit 807, and an FCS is added to form a frame, which is then sent to the wireless communication unit via the MAC control unit 88. However, based on the frequency band and channel information (Band, Ch Info) obtained from the RTS 502 and sent to the frequency band and channel control unit 809, the CTS 504 will be transmitted on millimeter-wave band channels 405-1 and 405-2. Therefore, based on the information from the frequency band and channel control unit 809, the CTS 504 is duplicated in the MAC control unit 808, and two CTS 504s are sent to the wireless communication unit 804.

[0067] In the physical frame generation unit 822 within the wireless communication unit 804, encoding, modulation, and OFDM signal generation are performed on the MAC frame sent from the communication control unit 802, and a PHY header is added to form a physical frame. This is then sent to the wireless transmission unit 823, where D / A conversion and frequency conversion for wireless transmission are performed, and the frame is transmitted wirelessly from the antenna unit 806. With this configuration, in an IMMW-compatible system, the CTS 504 frame for the RTS 502 received from AP 401-1 can be transmitted in the millimeter wave band. In this embodiment, when transmitting and receiving in the millimeter wave band, a pre-formed beam or selected sector is used. The operation of beam formation and sector selection will not be explained here, but in this embodiment, when transmitting and receiving in the millimeter wave band in STA 402-1, a pre-formed beam or selected sector is used for transmission and reception.

[0068] After the transmission of the CTS 504, the data frame 506 is transmitted from AP 401-1 on millimeter-wave channels 405-1 and 405-2, and the data frame 506 is received by STA 402-1. The data frame reception operation in STA 402-1 is basically the same as the reception operation of RTS 502, but since the data frame 506 is transmitted in the millimeter-wave band, it is received by the antenna unit 806 shown in Figure 8 and sent to the wireless reception unit 825 and the physical frame reception unit 824. The data extracted by demodulation and decoding in the physical frame reception unit 824 is sent to the data acquisition unit 814, and further sent to the upper layer 801 via the MAC control unit 808.

[0069] After receiving such a data frame 506, STA 402-1 sends back BA 507 to AP 401-1 as an acknowledgment, notifying AP 401-1 that the data frame 506 has been received without error. This BA 507, like the CTS 504 and data frame 506, is transmitted in the millimeter-wave band. It is generated by the control information generation unit 812, sent to the wireless communication unit 804 via the MAC control unit 808, and transmitted from the antenna unit 806. With this configuration of the STA, it is possible to receive RTS in the microwave band, send back CTS in the millimeter-wave band, and receive data frames and transmit acknowledgments in the millimeter-wave band, enabling the operation shown in Figure 5.

[0070] Furthermore, the STA shown in Figure 8 can also operate as STA402-2. When operating as STA402-2, STA402-2 can receive RTS502, but the reception operation of RTS502 is the same as the reception operation of STA402-1. However, since it can be determined from the information contained in RTS502 that the subsequent transmission between AP401-1 and STA402-1 will be carried out in the millimeter wave band, the MAC control unit 808 controls the setting of NAV in the millimeter wave band for the duration of the Duration acquired by the Duration information acquisition unit 817. In other words, during this time, STA402-2 does not perform any transmission in the millimeter wave band, and after the NAV period ends, it waits for the duration of the DIFS, then enters a contention window period where it waits for a random waiting time, and then the MAC control unit 808 controls it to move on to the operation to acquire the next transmission right.

[0071] Furthermore, the STA shown in Figure 8 can also operate as an STA within BSS403-2, for example, STA402-3. When operating as STA402-3, STA402-3 cannot receive RTS502 transmitted on channel 404-1, but it can receive CTS504 transmitted on channel 407-1 (the same channel as 405-1) in the millimeter wave band. This CTS504 is received by the antenna unit 806 in Figure 8, and the MAC frame of CTS504 is sent to the MAC frame receiving unit 8010 via the wireless communication unit 804. Of the MAC frame of TS504, Frame Control is sent to the control information acquisition unit 815, and Duration is sent to the Duration information acquisition unit 817, and the respective information is acquired. In addition, information indicating the frequency band and channel of channel 407-1 (the same channel as 405-1) is sent to the frequency band / channel information acquisition unit 816. Based on this information, it can be determined that STA402-1 is attempting to receive data transmission via channel 407-1 (the same channel as 405-1). Therefore, the MAC control unit 808 controls the setting of NAV in the millimeter wave band for the duration of the Duration acquired by the Duration information acquisition unit 817. In other words, during this time, STA402-3 does not perform any transmission in the millimeter wave band. After the NAV period ends, it waits for the duration of the DIFS period, then enters a contention window period where it waits for a random waiting time, and then moves on to operations aimed at acquiring the next transmission right. This control is performed by the MAC control unit 808.

[0072] By configuring the AP and STA as described above, in downlink transmission in this embodiment, the AP can transmit RTS in the microwave band with the main purpose of setting NAV in the STA within its own BSS, and the STA can transmit CTS in the millimeter-wave band with the main purpose of setting NAV in the STA within the adjacent BSS. When either RTS or CTS is received at the target STA, the appropriate NAV can be set at each STA. As a result, when data transmission is performed in the millimeter-wave band in IMMW, either RTS or CTS can be received by surrounding STAs, including STAs within adjacent BSSs, thus preventing the occurrence of the hidden terminal problem.

[0073] In this embodiment, we have focused on IMMW, which uses the millimeter-wave band in addition to the microwave band, and have shown a method to avoid the hidden terminal problem for data transmission in the millimeter-wave band. However, there is also a possibility of coexistence with existing systems that use the millimeter-wave band, such as IEEE 802.11ad and IEEE 802.11ay. In IEEE 802.11ad and IEEE 802.11ay, single-carrier transmission is a required function, and multi-carrier (OFDM) transmission is optional. Therefore, it may not be possible to correctly receive the multi-carrier (OFDM) signals used in IMMW. However, if the optional multi-carrier transmission function is implemented in IEEE 802.11ad or IEEE 802.11ay, it may be possible to receive the CTS in this embodiment. In such cases, based on the Duration and RA information included in the CTS, it is possible to determine that data transmission is taking place in the millimeter-wave band, and to set appropriate NAVs in IEEE 802.11ad and IEEE 802.11ay systems. This makes it possible to avoid hidden terminal problems caused by nearby IEEE 802.11ad and IEEE 802.11ay systems, and enables coexistence with those systems.

[0074] Furthermore, it is possible to effectively coexist not only with existing systems using the millimeter-wave band, but also with existing systems using the microwave band. In this embodiment, the RTS is transmitted in the microwave band and the CTS is transmitted in the millimeter-wave band. Therefore, in order to coexist with existing systems using the microwave band, it is necessary for those existing systems to correctly receive at least a part of the RTS, and the RTS configuration for this purpose is shown in Figure 6(1)-3. When an RTS having the configuration shown in Figure 6(1)-3 is received by an existing system such as IEEE 802.11ax or IEEE 802.11be, it is possible to demodulate from Frame Control to TA and receive it correctly. However, the channel information (Ch Info) included in this RTS (which may also be frequency band / channel information (Band, Ch Info)) indicates that subsequent CTS and data frames will be transmitted in the millimeter-wave band. However, existing systems do not include such channel information (Ch Info) in their RTS, so they cannot correctly receive the channel information (Ch Info) of the RTS shown in Figure 6(1)-3. The Duration of the RTS shown in Figure 6(1)-3 indicates a series of periods related to data transmission in the millimeter-wave band channel indicated by the channel information (Ch Info). However, in existing systems that cannot correctly receive the channel information (Ch Info), Duration will be recognized as information indicating a series of periods related to data transmission in the microwave band channel. In this case, an existing system that receives the RTS shown in Figure 6(1)-3 will set NAV for the period indicated by Duration and suspend communication using the microwave band channel during that time. In contrast, in this embodiment, data transmission actually takes place on millimeter-wave channels, and the NAV set in the microwave band in existing systems becomes a wasted period. Since data transmission cannot be performed during that period, it leads to a decrease in frequency utilization efficiency.

[0075] As described above, the RTS shown in Figure 6(1)-3 can be received by existing systems such as IEEE 802.11ax and IEEE 802.11be, with some exceptions. However, as a result of this reception, unnecessary NAV settings are set in the microwave band, leading to a decrease in frequency utilization efficiency. Therefore, Figure 9 shows a modified version of the RTS in this embodiment, which avoids setting NAV settings that lead to such a decrease in frequency utilization efficiency and enables the effective coexistence of the IMMW system in this embodiment with existing systems such as IEEE 802.11ax and IEEE 802.11be.

[0076] The RTS shown in Figure 9 has almost the same configuration as the RTS shown in Figure 6(1)-3, but it has two Duration information components: Duration 1 immediately after Frame Control, and Duration 2 after the frequency band and channel information (Band, Ch Info). In the system targeting IMMW in this embodiment, the entirety of this configuration can be received, but existing systems can only receive the portion from Frame Control to TA. In this configuration, by setting the period indicated by Duration 1 to a very short period, the NAV period set in the microwave band in existing systems can be made very short. Here, the period indicated by Duration 1 may be, for example, the length of one SIFS period, or it may be zero. Duration 1 can be received by the IMMW system in this embodiment, but Duration 2 can also be received. Therefore, the period indicated by Duration 2 is set as the period that should be set in the millimeter-wave band, and by updating the information of Duration 1 with the information of Duration 2 on the receiving side, it is possible to set an appropriate NAV period in the millimeter-wave channel indicated by the frequency band and channel information (Band, Ch Info). In other words, Duration 1 is positioned as dummy information in the IMMW system in this embodiment, and in existing systems that receive this RTS, it is information for setting a very short NAV in the microwave band. In addition, Duration 2 correctly notifies the IMMW system in this embodiment of the period of NAV that should be set in the millimeter-wave band, making it possible to achieve efficient coexistence between the IMMW system in this embodiment and existing systems.

[0077] Up to this point, we have described downlink transmission, where data is transmitted from AP to STA, as shown in Figure 5. However, the system targeting IMMW in this embodiment can also support uplink transmission, where data is transmitted from STA to AP. In this case, for example, this can be achieved by swapping the operations of AP401-1 and STA402-1 shown in Figure 5. The STA transmits RTS in the microwave band, and the AP transmits CTS in the millimeter-wave band. Based on this information, the surrounding STAs, including the STAs within the OBSS, can be instructed to set an appropriate NAV in the millimeter-wave band for a suitable period. Then, with the appropriate NAV set in the surrounding STAs, data can be transmitted from STA to AP in the millimeter-wave band. In this case, the STA can be configured as shown in Figure 7, and the AP as shown in Figure 8. In other words, the configurations shown in Figure 7 and Figure 8 can be swapped. Thus, in the uplink transmission of the wireless communication system according to this embodiment, similar to downlink transmission, RTS can be transmitted in the microwave band primarily for the purpose of setting NAV in STAs within its own BSS, and CTS can be transmitted in the millimeter-wave band primarily for the purpose of setting NAV in STAs within adjacent BSSs. By receiving either RTS or CTS at the target STAs, the appropriate NAV can be set at each STA. As a result, when data transmission is performed in the millimeter-wave band in IMMW, either RTS or CTS can be received by surrounding STAs, including STAs within adjacent BSSs, thereby preventing the occurrence of the hidden terminal problem.

[0078] In the embodiments described so far, we have discussed the case where RTS and CTS transmission in different frequency bands is applied to the uplink. In this case, the STA transmits the RTS in the microwave band, and the AP transmits the CTS in the millimeter-wave band. Normally, the AP can transmit over a wider area within the BSS than the STA, but when applied to the uplink, the CTS transmitted by the AP is transmitted in the millimeter-wave band, making it difficult to deliver the CTS over a wide area, and potentially increasing the likelihood of hidden terminal problems compared to when applied to the downring. Therefore, as a modification, we will show an embodiment that can further suppress the occurrence of hidden terminal problems.

[0079] Figure 10 shows an example of frame transmission, reception, and operation in a modified wireless communication system. In Figure 10, Sub 7GHz and mmWave are defined the same as in Figure 5. Figure 10 shows an example of frames transmitted in the microwave band represented by Sub 7GHz and the millimeter wave band represented by mmWave, respectively, and their transmission and reception operations, when uplink data transmission from STA402-1 of BSS403-1 to AP401-1 is performed in the millimeter wave band. The definitions of NAV and CW are also the same as in Figure 5.

[0080] As shown in Figure 10, a modified example shows a configuration in which the CTS is also transmitted in the microwave band. As described in the previous embodiment, by having the STA transmit the RTS in the microwave band and the AP transmit the CTS in the millimeter-wave band, the surrounding STAs, including the STA in the OBSS, can set an appropriate NAV in the millimeter-wave band, and data transmission from the STA to the AP can be performed in the millimeter-wave band. In this case, the RTS in the microwave band is shown as RTS1002 in Figure 10, the CTS in the millimeter-wave band as CTS1004, and the data in the millimeter-wave band as 1006. In the modified example, in addition to this, the AP transmits CTS1009 as the CTS in the microwave band.

[0081] Furthermore, the CTS 1004 in the millimeter-wave band is transmitted on the same millimeter-wave channel as the subsequent data transmission (for example, channels 405-1 and 405-2 in Figure 4), and the CTS 1009 in the microwave band is transmitted on the same microwave band channel as the RTS 1002 (the primary channel of the target BSS, for example, channel 404-1 in Figure 4). Also, as shown in Figure 10, the CTS 1004 and CTS 1009 are transmitted simultaneously. Aside from the addition of the CTS 1009 transmitted in the microwave band, the modified version has basically the same configuration and operation as the previous embodiment. Furthermore, the device configurations of the STA and AP can also be the same as in the previous embodiment. With this configuration, in the modified version, the CTS can also be transmitted in the microwave band from the AP, thereby enabling the CTS to be delivered to a wider area and preventing the occurrence of the hidden terminal problem.

[0082] Here, the RTS 1002 in Figure 10 can have the same configuration as the RTS shown in Figures 6 and 9, and the CTS 1009 in Figure 10 can have the same configuration as the CTS shown in Figure 6, but may have other configurations. Also, information such as Duration may be the same as the information described in the previous embodiment. However, in the modified example, since both RTS and CTS are transmitted in the microwave band, the Duration 1 information when the RTS configuration shown in Figure 9 is used can be set to indicate the end of CTS 1009 or the end of SIFS 1003-2. This makes it possible to protect the transmission of CTS 1009 while ensuring efficient coexistence without requiring existing systems such as IEEE 802.11ax and IEEE 802.11be that use the microwave band to set unnecessarily long NAVs. Furthermore, the CTS 1009 in Figure 10 may have a different configuration from the CTS shown in Figure 6 in order to ensure efficient coexistence with existing systems such as IEEE 802.11ax and IEEE 802.11be that use the microwave band, and an example of this is shown in Figure 11.

[0083] As shown in Figure 11, a modified version of the CTS 1009 has a new configuration that includes frequency band and channel information (Band, Ch Info) and two types of duration information, Duration 1 and Duration 2. In this configuration, as with the RTS shown in Figure 9, existing systems can only correctly demodulate up to a certain point in the frame, and in the case of the CTS shown in Figure 11, it can only correctly demodulate up to RA. Therefore, by setting Duration 1 as the duration for existing systems and setting the period indicated by Duration 1 to the end of SIFS 1003-2, it is possible to prevent the setting of unnecessarily long NAVs for existing systems such as IEEE 802.11ax and IEEE 802.11be that use the microwave band. Furthermore, by setting the frequency band and channel information (Band, Ch Info) that the IMMW system can demodulate to indicate that the channel actually transmitting the data frame is a millimeter-wave channel, and by setting the period indicated by Duration 2 to the end of BA1007, it becomes possible to protect data frame 1006 in an IMMW system using the millimeter-wave band. With this configuration, even when transmitting CTS from the AP in the microwave band in the modified example, it is possible to deliver CTS to a wider area while efficiently coexisting with existing systems such as IEEE 802.11ax and IEEE 802.11be that use the microwave band without requiring unnecessarily long NAV settings.

[0084] Here, the configuration of CTS1009 can be as shown in Figure 11, and the configuration of CTS1004 can be as shown in Figure 6. However, in this case, the lengths of the CTS will not be the same, and as a result, the end timing of the NAV, which is set based on the Duration information shown by these CTS, will not be the same. To prevent this, it is preferable that the Duration information included in CTS1009 and CTS1004, specifically Duration 2 in Figure 11 and the Duration of the CTS in Figure 6, are not the same, but rather Duration information that takes into account the difference in the lengths of the configurations of the CTS shown in Figure 11 and Figure 6, respectively. More specifically, the CTS shown in Figures 11 and 6 differ only in the length of the frequency band / channel information (Band, Ch Info) and Duration 2. Therefore, the length indicated by Duration in the CTS shown in Figure 6 (CTS 1004) is set to be longer than the length indicated by Duration in the CTS shown in Figure 11 (CTS 1009) by the length of the frequency band / channel information (Band, Ch Info) plus Duration 2. By setting it in this way, the end timing of the NAV set based on CTS 1009 and the NAV set based on CTS 1004 can be synchronized.

[0085] Furthermore, in the configuration shown in Figure 10, the CTS 1004 in the millimeter-wave band is transmitted on the same millimeter-wave channel as the subsequent data transmission (for example, channels 405-1 and 405-2 in Figure 4), and the CTS 1009 in the microwave band is transmitted on the same microwave band channel as the RTS 1002 (the primary channel of the target BSS, for example, channel 404-1 in Figure 4). However, it is conceivable that the millimeter-wave channel to which the CTS 1004 and the subsequent data frame 1006 are transmitted may be busy, preventing the transmission of the CTS 1004. In such a case, the CTS 1009 in the microwave band may also be controlled not to be transmitted, meaning that in this case, the CTS will not be transmitted in either the millimeter-wave or microwave band. Alternatively, the CTS in the microwave band may be controlled to be transmitted even if the millimeter-wave channel is busy. This is an STA that receives RTS1002 in the microwave band and sets NAV1008-1 based on it. In cases where there is an STA that has difficulty receiving millimeter-wave frames regardless of whether or not millimeter-wave CTS is transmitted, it is conceivable to maintain NAV1008-1 as is, regardless of whether or not millimeter-wave CTS is transmitted. However, it is possible to perform an operation that cancels this NAV1008-1 using the microwave band CTS. To achieve this, for example, in the configuration shown in Figure 11, it is possible to notify that the millimeter-wave channel used for data transmission is busy by setting the frequency band / channel information (Band, Ch Info) to blank, or to channel information that does not exist in the relevant BSS, or by setting the length indicated by Duration 2 to zero, thereby making it possible to set the length of NAV1008-2 to zero. Furthermore, even if an STA has already set NAV1008-1, it can cancel the NAV1008-1 setting based on this information, enabling efficient frequency utilization without setting an unnecessarily long NAV even when data transmission in the millimeter-wave band is not possible.

[0086] Here, we have described uplink transmission, where data is transmitted from STA to AP, as shown in Figure 10. However, downlink transmission, where data is transmitted from AP to STA, is also possible. In this case, for example, this can be achieved by swapping the operations of AP401-1 and STA402-1 shown in Figure 10. The AP transmits RTS in the microwave band, and the STA transmits CTS in the microwave band and millimeter-wave band. Based on this information, the surrounding STAs, including the STAs within OBSS, can be instructed to set an appropriate NAV in the millimeter-wave band for an appropriate period. Then, with the appropriate NAV set in the surrounding STAs, data transmission from AP to STA can be performed in the millimeter-wave band.

[0087] Furthermore, while the RTS in the microwave band in the previous embodiment, and the RTS and CTS in the modified embodiment, have been configured to be transmitted on the primary channel of the BSS to which they belong, the configuration is not limited to this, and they may also be transmitted on a different channel in the microwave band. For example, APs of adjacent BSSs may cooperate to acquire information on each other's primary channels in the microwave band, and based on that information, they may transmit the RTS in the microwave band in the previous embodiment, and the RTS and CTS in the modified embodiment, on the primary channel of the OBSS in the microwave band. By adopting such a configuration, it becomes possible to deliver the RTS and CTS in the microwave band to STAs belonging to the OBSS with a higher probability, and it becomes possible to set an appropriate NAV period in the millimeter wave band for STAs within the OBSS. This makes it possible to avoid the hidden terminal problem caused by the OBSS for data transmission in the millimeter wave band.

[0088] The wireless communication device according to the present invention can communicate in frequency bands (frequency spectrums) known as unlicensed bands, which do not require permission from a country or region for use, but the usable frequency bands are not limited to these. The wireless communication device according to the present invention can also be effective in frequency bands known as white bands, which are not actually used for purposes such as preventing interference between frequencies, even though permission for use has been granted by a country or region for use in specific services (for example, frequency bands allocated for television broadcasting but not used in some regions), as well as in shared spectrums (shared frequency bands) that are expected to be shared by multiple operators.

[0089] The program that operates in the wireless communication device according to the present invention is a program that controls the CPU and other components (a program that makes the computer function) in order to realize the functions of the earlier embodiments related to the present invention. The information handled by these devices is temporarily stored in RAM during processing, and then stored in various ROMs or HDDs, and read, modified, and written by the CPU as needed. The recording medium for storing the program may be any of the following: semiconductor media (e.g., ROM, non-volatile memory card, etc.), optical recording medium (e.g., DVD, MO, MD, CD, BD, etc.), magnetic recording medium (e.g., magnetic tape, flexible disk, etc.). Furthermore, in addition to realizing the functions of the above embodiments by executing the loaded program, the functions of the present invention may also be realized by processing in cooperation with the operating system or other application programs based on the instructions of the program.

[0090] Furthermore, when distributing the program to the market, it can be stored on a portable recording medium and distributed, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. In addition, some or all of the wireless communication device in the above-described embodiment may be implemented as an LSI, which is typically an integrated circuit. Each functional block of the wireless communication device may be individually chipped, or some or all of them may be integrated into a single chip. When each functional block is implemented as an integrated circuit, an integrated circuit control unit is added to control them. Needless to say, the present invention also includes cases where programs and configuration information are downloaded from a server computer in order to implement at least some of the functions of the above-described embodiment.

[0091] Furthermore, the method of implementing integrated circuits is not limited to LSIs; it may also be implemented using dedicated circuits or general-purpose processors. Additionally, if advancements in semiconductor technology lead to the emergence of integrated circuit technologies that can replace LSIs, it is possible to use integrated circuits based on those technologies.

[0092] It should be noted that the present invention is not limited to the embodiments described above. The wireless communication device of the present invention is not limited to application to portable devices, but can also be applied to stationary or non-movable electronic devices installed indoors or outdoors, such as AV equipment, kitchen appliances, cleaning and washing machines, air conditioning equipment, office equipment, vending machines, and other household appliances.

[0093] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and designs that do not depart from the spirit of this invention are also included in the claims.

[0094] The present invention is suitable for use in access point devices and terminal devices.

[0095] 101 RTS frame 102 CTS frame 103 Data frame 104 BA (Block Ack) frame 105, 106 NAV (based on RTS and CTS respectively) 301-1, 301-2 DIFS period 302 RTS frame 303-1, 303-2, 303-3 SIFS period 304 CTS frame 305 Data frame 306 Ack frame 307-1, 307-2, 307-3 NAV (based on RTS, CTS, and data frame respectively) 308 Contention window 401-1, 401-2 AP device 402-1, 402-2, 402-3, 402-4 STA device 403-1, 403-2 BSS 404-1, 404-2, 404-3, 404-4 Microwave channels in BSS403-1 405-1, 405-2 Millimeter-wave channels in BSS403-1 406-1, 406-2 Microwave channels in BSS403-2 407-1 Millimeter-wave channels in BSS403-2 501-1, 501-2, 501-3 DIFS period 502 RTS frame 503-1, 503-2, 503-3 SIFS period 504 CTS frame 505-1, 505-2, 505-3 Contention window 506 Data frame 507 BA (Block Ack) frame 508-1, 508-2 NAV (based on RTS and CTS respectively) 701 Upper layer 702 Communication control unit 703, 704 Wireless communication unit 705, 706 Antenna unit 707 MAC frame generation unit 708 MAC control unit 709 Frequency band / channel control unit 710 MAC frame reception unit 711, 715 Data acquisition unit 712 Control information generation unit 713 Frequency band / channel information generation unit 714 Duration information calculation unit 716 Control information acquisition unit 717 Frequency band / channel information acquisition unit 718 Duration information acquisition unit 719, 723 Physical frame generation unit 720, 724 Wireless transmission unit 721, 725 Physical frame reception unit 722, 726 Wireless reception unit 801 Upper layer 802 Communication control unit 803, 804 Wireless communication unit 805, 806 Antenna unit 807 MAC frame generation unit 808 MAC control unit 809 Frequency band / channel control unit810 MAC frame receiving unit 811, 814 Data acquisition unit 812 Control information generation unit 813 Duration information calculation unit 815 Control information acquisition unit 816 Frequency band / channel information acquisition unit 817 Duration information acquisition unit 818, 822 Physical frame generation unit 819, 823 Wireless transmission unit 820, 824 Physical frame receiving unit 821, 825 Wireless receiving unit 1001-1, 1001-2, 1001-3 DIFS period 1002 RTS frame 1003-1, 1003-2, 1003-3 SIFS period 1004 CTS frame 1005-1, 1005-2, 1005-3 Contention window 1006 Data frame 1007 BA (Block Ack) frame 1008-1, 1008-2 NAV (based on RTS and CTS respectively) 1009 CTS frame

Claims

1. An access point device that performs wireless communication with a terminal device using at least a first frequency band and a second frequency band, characterized in that, in a downlink transmission in which the access point device transmits a first data frame to the terminal device, prior to transmitting the first data frame, it transmits a request to transmit (RTS) frame in the first frequency band, receives a acknowledgment to transmit (CTS) frame in at least the second frequency band, and transmits the first data frame in the second frequency band.

2. The access point device according to claim 1, characterized in that, in an uplink transmission for receiving a second data frame from the terminal device, prior to receiving the second data frame, it receives a request to transmit (RTS) frame in the first frequency band, transmits a acknowledgment (CTS) frame in at least the second frequency band, and receives the second data frame from the terminal device in the second frequency band.

3. The access point device according to claim 1, characterized in that the first frequency band is 10 GHz or less and the second frequency band is 30 GHz or more.

4. The access point device according to claim 1, characterized in that the transmitted request to transmit (RTS) frame includes information indicating the second frequency band and the channels used in the second frequency band, and information indicating two occupancy times.

5. The access point device according to claim 2, characterized in that the received request to transmit (RTS) frame includes information indicating the second frequency band and the channel used in the second frequency band, and information indicating two occupancy times.

6. The access point device according to claim 1, characterized in that, in the downlink transmission, it receives a transmit acknowledgment (CTS) frame in both the first frequency band and the second frequency band.

7. The access point device according to claim 2, characterized in that, in the uplink transmission, a transmit acknowledgment (CTS) frame is transmitted in both the first frequency band and the second frequency band.

8. A terminal device that performs wireless communication with an access point device using at least a first frequency band and a second frequency band, wherein in an uplink transmission in which the terminal device transmits a first data frame to the access point device, the terminal device transmits a request to transmit (RTS) frame in the first frequency band prior to transmitting the first data frame, receives a acknowledgment to transmit (CTS) frame in at least the second frequency band, and transmits the first data frame in the second frequency band.

9. The terminal device according to claim 8, characterized in that, in a downlink transmission for receiving a second data frame from the access point device, prior to receiving the second data frame, it receives a request to transmit (RTS) frame in the first frequency band, transmits a acknowledgment (CTS) frame in at least the second frequency band, and receives the second data frame from the access point device in the second frequency band.

10. The terminal device according to claim 8, characterized in that the first frequency band is 10 GHz or less and the second frequency band is 30 GHz or more.

11. The terminal device according to claim 8, characterized in that the transmitted request to transmit (RTS) frame includes information indicating the second frequency band and the channels used in the second frequency band, and information indicating two occupancy times.

12. The terminal device according to claim 9, characterized in that the received request to transmit (RTS) frame includes information indicating the second frequency band and the channels used in the second frequency band, and information indicating two occupancy times.

13. The terminal device according to claim 8, characterized in that, in the uplink transmission, it receives a transmit acknowledgment (CTS) frame in both the first frequency band and the second frequency band.

14. The terminal device according to claim 9, characterized in that, in the downlink transmission, a transmission acknowledgment (CTS) frame is transmitted in both the first frequency band and the second frequency band.

15. A terminal device that uses a first frequency band and a second frequency band, wherein when an access point device that does not directly communicate wirelessly with the terminal device and another terminal device communicate wirelessly, the access point device and the other terminal device each receive at least one frame of either a request to transmit (RTS) frame transmitted in the first frequency band or an acknowledgment to transmit (CTS) frame transmitted in the second frequency band, and based on information indicating the occupancy time contained in at least one of the received request to transmit (RTS) frames or acknowledgment to transmit (CTS) frames, the terminal device suspends its own transmission in the second frequency band for the duration of the occupancy time.

Images