JP2016213568A - Integrated circuit for wireless communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated circuit for wireless communication capable of ensuring uniform access among terminals in a system using CSMA/CA.SOLUTION: An integrated circuit for wireless communication in an embodiment has a baseband integrated circuit that, when no first information is set for identifying the own unit in a first field of a packet which includes at least one of the first field and a multiplied plural second field, extracts a frame from one of the plural second fields to control not to access to radio medium for a period of time represented by a value set in the frame.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an integrated circuit for wireless communication.

  A communication method called OFDMA (Orthogonal Frequency Division Multiple Access) that performs transmission to a plurality of wireless communication terminals (hereinafter referred to as terminals) or reception from a plurality of terminals simultaneously is known. OFDMA in which one or more subcarriers are allocated to a terminal as a resource block and transmission to a plurality of terminals or reception from a plurality of terminals is performed simultaneously on a resource block basis may be particularly referred to as resource block based OFDMA . Simultaneous transmission from a base station to a plurality of terminals corresponds to downlink OFDMA transmission, and simultaneous transmission from a plurality of terminals to a base station corresponds to uplink OFDMA transmission.

  In a wireless LAN system conforming to the IEEE 802.11 standard using CSMA / CA (Carrier Sense Multiple Access Carrier Aviation), when communication is performed using resource block-based OFDMA, terminals that are not subject to OFDMA exist in the system. Must be taken into account. A terminal that is not a target of OFDMA is a terminal that is not a target of OFDMA implemented this time.

  When OFDMA communication is performed in an environment where there is a terminal (non-target terminal) that is not subject to OFDMA, the non-target terminal does not normally receive a frame (more specifically, a physical packet including the frame) transmitted / received by OFDMA. Therefore, an error is detected at the physical layer or the MAC layer. For this reason, at the next access to the wireless medium, an extended interframe space (EIFS) time is started as a certain period for performing carrier sense in the MAC layer. The EIFS time is longer than DIFS / AIFS [AC], which is a fixed time of carrier sense performed during normal medium access. For this reason, an unfairness occurs between the non-target terminal and other terminals (for example, a terminal and a base station that have performed OFDMA communication) regarding the opportunity to acquire the access right.

US Application Publication No. 2013/0286959 JP 2013-243893 A

IEEE 11-13 / 0287r3 IEEE Std 802.11ac-2013

  An embodiment of the present invention aims to make fair the opportunity of access to a wireless medium between terminals in a system using CSMA / CA.

  According to another aspect of the present invention, there is provided an integrated circuit for wireless communication that identifies a device in the first field of a packet including a first field and at least one of a plurality of multiplexed second fields. When information is not set, a frame is extracted from one of the plurality of second fields, and access to the wireless medium is suppressed during a period indicated by a value set in the frame. A baseband integrated circuit to be controlled is provided.

The functional block diagram of the radio | wireless communication apparatus which concerns on embodiment of this invention. The figure for demonstrating allocation of OFDMA communication and a resource block. The figure which shows the radio | wireless communication group formed with a base station and a some terminal. The figure for demonstrating the unfairness of the access to the wireless medium which may arise by OFDMA communication. The figure which shows the schematic format example of a physical packet. The figure which shows the basic format example of a MAC frame. The figure which shows carrier sense time typically. The figure which shows the example of an operation | movement sequence which concerns on 1st Embodiment. The figure which shows the other example of the operation | movement sequence which concerns on 1st Embodiment. The figure which shows the flowchart of operation | movement of the base station which concerns on 1st Embodiment. The figure which shows the flowchart of operation | movement of the terminal which concerns on 1st Embodiment. The figure which shows the 1st example of the operation | movement sequence which concerns on 2nd Embodiment. The figure which shows the 2nd example of the operation | movement sequence which concerns on 2nd Embodiment. The figure which shows the flowchart of operation | movement of the base station corresponding to the operation | movement sequence example shown in FIG. The figure which shows the 1st example of the operation | movement sequence which concerns on 3rd Embodiment. The figure which shows the flowchart of operation | movement of the base station corresponding to the operation | movement sequence example shown in FIG. The figure which shows the 2nd example of the operation | movement sequence which concerns on 3rd Embodiment. The figure which shows the 3rd example of the operation | movement sequence which concerns on 3rd Embodiment. The figure which shows the flowchart of operation | movement of the base station corresponding to the operation | movement sequence example shown in FIG. The figure for demonstrating the unfairness of the access to the wireless medium which may arise by MU-MIMO communication. The figure which shows the 1st example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the 2nd example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the 3rd example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the 5th example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the 6th example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the 7th example of the operation | movement sequence which concerns on 4th Embodiment. The figure which shows the hardware structural example of the radio | wireless communication apparatus which concerns on embodiment of this invention. 1 is a perspective view of a wireless communication terminal according to an embodiment of the present invention. The figure which shows the memory card based on embodiment of this invention. The figure which shows an example of the frame exchange of a contention period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. IEEE Std 802.11 ^™ -2012 and IEEE Std 802.11ac ^™ -2013, which are known as wireless LAN standards, are all incorporated herein by reference (incorporated by reference).

(First embodiment)
FIG. 1 is a functional block diagram of the wireless communication apparatus according to the first embodiment. This wireless communication apparatus can be implemented in a wireless communication base station (hereinafter referred to as a base station) or a wireless communication terminal (hereinafter referred to as a terminal) that communicates with the wireless communication base station. The base station is different from the terminal mainly in that it has a relay function, and the rest has basically the same communication function as that of the terminal, so that it can be considered as a form of the terminal. In the following description, the term “terminal” may refer to a base station unless it is particularly necessary to distinguish between the two.

  In this embodiment, the base station allocates resource blocks (which may be called subchannels, resource units, and frequency blocks) each having one or a plurality of continuous subcarriers in a continuous frequency domain as terminals. Then, it is assumed that resource block-based OFDMA (Orthogonal Frequency Division Multiple Access) communication is performed in which simultaneous transmission to multiple terminals or simultaneous reception from multiple terminals is performed. Transmission from the base station to the plurality of terminals corresponds to downlink OFDMA transmission, and transmission from the plurality of terminals to the base station corresponds to uplink OFDMA transmission.

  FIG. 2 shows how a plurality of channels are arranged in the frequency domain. A guard band is provided between the channels. The bandwidth of one channel is 20 MHz, for example. Consider performing OFDMA communication using a continuous band of one of these channels (here, channel M). A plurality of subcarriers orthogonal to each other (for example, 52 in the case of the 20 MHz band) are arranged in a continuous band of the channel M (for example, 20 MHz wide band), and one or a plurality of continuous carriers are arranged based on these subcarriers. A resource block having one subcarrier as a unit is allocated to terminal 1, terminal 2,..., Terminal K (K is an integer of 2 or more). The bandwidth (or the number of subcarriers) for each resource block is common to each resource block, but the bandwidth (or the number of subcarriers) may be different for each resource block. The number of resource blocks allocated to each terminal is one resource block per terminal in the example of FIG. 2, but a plurality of resource blocks may be allocated to one terminal, and the number of resource blocks allocated to each terminal is May be different. When the resource block is composed of a plurality of subcarriers, the arrangement of subcarriers included in the resource block may or may not be continuous. It is also possible to assign a plurality of subcarriers arranged discontinuously as resource blocks to one wireless terminal.

  In the example of FIG. 2, at least one subcarrier is arranged as a guard subcarrier between resource blocks allocated to each terminal. The number of guard subcarriers arranged between resource blocks may be determined in advance by the system or specification, or may be determined arbitrarily. Moreover, it is not essential to arrange guard subcarriers between resource blocks, and it may be allowed not to arrange guard subcarriers between resource blocks.

  The number of channels used in OFDMA communication is not limited to one, and OFDMA communication can be performed using two or more channels. At this time, resource blocks may be allocated in each channel independently as described above. In this case, one terminal may be allowed to receive allocation of a plurality of resource blocks belonging to different channels. Further, instead of allocating resource blocks independently for each channel, a continuous frequency region in which a plurality of channels are combined may be defined, and resource blocks may be allocated in the combined frequency region. For example, a 40 MHz frequency region may be defined by combining two 20 MHz wide channels adjacent in frequency, and resource blocks may be allocated based on mutually orthogonal subcarrier groups within the 40 MHz frequency region. Similarly, four channels having a width of 20 MHz may be combined to define a frequency region of 80 MHz, and eight channels may be combined to define a frequency region of 160 MHz. In this case, resource blocks may be allocated based on subcarrier groups orthogonal to each other in each frequency domain.

  Note that the terminal according to the present embodiment has at least the basic channel width of the legacy terminal to be backward compatible (20 MHz channel width if the IEEE 802.11a / b / g / n / ac standard compatible terminal is a legacy terminal). A physical packet can be received and decoded (including decoding and demodulation of an error correction code). At this time, carrier sense is performed in units of channels. CCA (Clear Channel Assessment) busy / idle physical carrier sense (Physical Carrier Sense) and virtual carrier sense (Virtual Carrier Sense) based on the medium reservation time described in the received frame Both may be included. A mechanism for determining that a medium is virtually busy, such as the latter, or a period during which a medium is virtually busy is called a NAV (Network Allocation Vector). Carrier sense information based on CCA or NAV performed for each channel may be commonly applied to all resource blocks in the channel. For example, resource blocks belonging to a channel whose carrier sense information indicates idle may be processed as being idle by commonly applying the carrier sense information of the channel. Note that the terminal according to the present embodiment is not limited to performing carrier sense on a channel basis, and if the terminal implements a mechanism that performs carrier sense on a resource block basis, carrier sense (physical sense on a resource block basis) (Both manual and virtual) may be allowed to be performed.

  In the present embodiment, it is assumed that resource block-based OFDMA communication is performed between a base station and a plurality of terminals as described above. However, the present invention is not limited to resource block base, and even if channel-based OFDMA communication is allowed. Good. The OFDMA in this case may be particularly referred to as channel-based OFDMA or MU-MC (Multi-User Multi-Channel). In MU-MC, a base station assigns a plurality of channels to a plurality of terminals, and simultaneously uses the plurality of channels to simultaneously transmit to or receive from a plurality of terminals. In the description of the embodiments related to resource block-based OFDMA described below, channel-based OFDMA embodiments are also performed by performing necessary replacement in accordance with channel-based OFDMA, such as appropriately replacing resource blocks with channels. It is feasible.

  In the following description, a terminal having the capability of performing resource block-based OFDMA communication may be referred to as an OFDMA-compatible terminal, and a terminal not having the capability may be referred to as a legacy terminal. When the capability of performing OFDMA communication can be switched between enabled (disabled) and disabled (disabled), a terminal with the enabled capability may be considered as an OFDMA compatible terminal. Further, among OFDMA compatible terminals, a terminal designated as a base station for OFDMA communication this time corresponds to a target terminal for OFDMA, and a terminal not designated as a base station for OFDMA communication this time is an OFDMA terminal. Sometimes called non-target terminal.

  As shown in FIG. 1, a wireless communication device mounted on a terminal (a non-base station terminal and a base station) includes an upper processing unit 90, a MAC processing unit 10, a PHY (Physical) processing unit 50, a MAC / A PHY management unit 60, an analog processing unit 70 (analog processing units 1 to N), and an antenna 80 (antennas 1 to N) are included. N is an integer of 1 or more. In the figure, a pair of N analog processing units and N antennas are connected, but the present invention is not necessarily limited to this configuration. For example, the number of analog processing units may be one, and two or more antennas may be commonly connected to the analog processing unit.

  The MAC processing unit 10, the MAC / PHY management unit 60, and the PHY processing unit 50 correspond to one form of a communication processing device or a baseband integrated circuit that performs processing related to communication with other terminals (including base stations). The analog processing unit 70 corresponds to, for example, a form of a wireless communication unit or an RF (Radio Frequency) integrated circuit that transmits and receives signals via the antenna 80. The integrated circuit for wireless communication according to the present embodiment may include at least the former of the baseband integrated circuit (communication processing device) and the RF integrated circuit. The functions of the communication processing device or the baseband integrated circuit may be performed by software (program) that operates on a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware. May be. The software may be stored in a storage medium such as a ROM or RAM, a hard disk, or an SSD, read by a processor, and executed. The memory may be a volatile memory such as a DRAM or a non-volatile memory such as a NAND or MRAM.

  The upper processing unit 90 performs processing for the upper layer on the MAC (Medium Access Control) layer. The host processing unit 90 can exchange signals with the MAC processing unit 10. Typical examples of the upper layer include TCP / IP, UDP / IP, and an upper application layer. However, the present embodiment is not limited to this. The upper processing unit 90 may include a buffer for exchanging data between the MAC layer and the upper layer. You may connect with a wired infrastructure via the high-order process part 90. FIG. The buffer may be a memory, an SSD, a hard disk, or the like. When the buffer is a memory, the memory may be a volatile memory such as a DRAM or a nonvolatile memory such as a NAND or MRAM.

  The MAC processing unit 10 performs processing for the MAC layer. As described above, the MAC processing unit 10 can exchange signals with the host processing unit 90. Further, the MAC processing unit 10 can exchange signals with the PHY processing unit 50. The MAC processing unit 10 includes a MAC common processing unit 20, a transmission processing unit 30, and a reception processing unit 40.

  The MAC common processing unit 20 performs processing common to transmission / reception in the MAC layer. The MAC common processing unit 20 is connected to the host processing unit 90, the transmission processing unit 30, the reception processing unit 40, and the MAC / PHY management unit 60, and exchanges signals with each other.

  The transmission processing unit 30 and the reception processing unit 40 are connected to each other. The transmission processing unit 30 and the reception processing unit 40 are connected to the MAC common processing unit 20 and the PHY processing unit 50, respectively. The transmission processing unit 30 performs transmission processing at the MAC layer. The reception processing unit 40 performs reception processing at the MAC layer.

  The PHY processing unit 50 performs processing for the physical layer (PHY layer). As described above, the PHY processing unit 50 can exchange signals with the MAC processing unit 10. The PHY processing unit 50 is connected to the antenna 80 via the analog processing unit 70.

  The MAC / PHY management unit 60 is connected to each of the upper processing unit 90, the MAC processing unit 10 (more specifically, the MAC common processing unit 20), and the PHY processing unit 50. The MAC / PHY management unit 60 manages the MAC operation and the PHY operation in the wireless communication apparatus.

  The analog processing unit 70 includes an analog / digital and digital / analog (AD / DA) converter and an RF (Radio Frequency) circuit. The analog processing unit 70 converts the digital signal from the PHY processing unit 50 into an analog signal having a desired frequency. A high-frequency analog signal transmitted from the antenna 80 and received from the antenna 80 is converted into a digital signal. Here, AD / DA conversion is performed by the analog processing unit 70, but a configuration in which the PHY processing unit 50 is provided with an AD / DA conversion function is also possible.

  The wireless communication apparatus according to the present embodiment includes (integrates) the antenna 80 as a constituent element in one chip, so that the mounting area of the antenna 80 can be reduced. Further, in the wireless communication apparatus according to the present embodiment, as illustrated in FIG. 1, the transmission processing unit 30 and the reception processing unit 40 share N antennas 80. Since the transmission processing unit 30 and the reception processing unit 40 share the N antennas 80, the wireless communication apparatus in FIG. 1 can be reduced in size. Of course, the wireless communication apparatus according to the present embodiment may have a configuration different from that illustrated in FIG.

  When receiving a signal from the wireless medium, the analog processing unit 70 converts the analog signal received by the antenna 80 into a baseband signal that can be processed by the PHY processing unit 50 and further converts the signal into a digital signal. The PHY processing unit 50 receives a digital reception signal from the analog processing unit 70 and detects the reception level. The detected reception level is compared with the carrier sense level (threshold), and if the reception level is equal to or higher than the carrier sense level, the PHY processing unit 50 indicates that the medium (CCA: Clear Channel Assessment) is busy. Are output to the MAC processing unit 10 (more precisely, the reception processing unit 40). If the reception level is less than the carrier sense level, the PHY processing unit 50 outputs a signal indicating that the medium (CCA) is idle to the MAC processing unit 10 (more precisely, the reception processing unit 40). .

  The PHY processing unit 50 performs a decoding process (including decoding and demodulation of an error correction code) on the received signal, a process of removing a preamble and a PHY header, and the like to extract a payload. According to the IEEE 802.11 standard, this payload is called PSDU (physical layer convergence procedure (PLCP) service data unit) on the PHY side. The PHY processing unit 50 passes the extracted payload to the reception processing unit 40, and the reception processing unit 40 handles this as a MAC frame. In the IEEE802.11 standard, this MAC frame is called an MPDU (medium access control (MAC) protocol data unit). In addition, the PHY processing unit 50 notifies the reception processing unit 40 when reception of the reception signal is started, and notifies the reception processing unit 40 when reception of the reception signal is completed. In addition, when the received signal can be normally decoded as a physical packet (PHY packet) (if no error is detected), the PHY processing unit 50 notifies the reception end of the received signal and the medium is idle. Is sent to the reception processing unit 40. When an error is detected in the received signal, the PHY processing unit 50 notifies the reception processing unit 40 that an error has been detected with an appropriate error code corresponding to the error type. When the PHY processing unit 50 determines that the medium has become idle, the PHY processing unit 50 notifies the reception processing unit 40 of a signal indicating that the medium is idle.

  The MAC common processing unit 20 mediates transmission of transmission data from the upper processing unit 90 to the transmission processing unit 30 and transmission of received data from the reception processing unit 40 to the upper processing unit 90, respectively. In the IEEE 802.11 standard, data in the MAC data frame is called MSDU (medium access control (MAC) service data unit). The MAC common processing unit 20 once receives an instruction from the MAC / PHY management unit 60, converts the instruction into a suitable one for the transmission processing unit 30 and the reception processing unit 40, and outputs them.

  The MAC / PHY management unit 60 corresponds to, for example, SME (Station Management Entity) in the IEEE 802.11 standard. In this case, the interface between the MAC / PHY management unit 60 and the MAC common processing unit 20 corresponds to the MLME SAP (MAC subLayer Management Service Access Point) in the IEEE 802.11 standard, and the MAC / PHY management unit 60 and the PHY. The interface to the processing unit 50 corresponds to a physical layer management service access (PLME SAP) in an IEEE 802.11 wireless LAN (Local Area Network).

  In FIG. 1, the MAC / PHY management unit 60 is depicted as if the function unit for MAC management and the function unit for PHY management are integrated, but may be implemented separately. Good.

  The MAC / PHY management unit 60 holds a management information base (MIB). The MIB holds various information such as whether the capability and various functions of the terminal itself are valid or invalid. For example, whether or not the own terminal is an OFDMA compatible terminal, and information on the on / off of the function of the ability to implement OFDMA in the case of the OFDMA compatible terminal may be held. The memory for holding and managing the MIB may be included in the MAC / PHY management unit 60, or may be provided separately without being included in the MAC / PHY management unit 60. When a memory for holding and managing the MIB is provided separately from the MAC / PHY management unit 60, the MAC / PHY management unit 60 can refer to the other memory and rewrites rewritable parameters in the memory. It can be performed. The memory may be a volatile memory such as a DRAM or a non-volatile memory such as a NAND or MRAM. Further, not a memory but a storage device such as an SSD or a hard disk may be used. In the base station, these pieces of information of other terminals as non-base stations can also be acquired by notification from the terminals. In that case, the MAC / PHY management unit 60 can refer to and rewrite information on other terminals. Or you may make it hold | maintain and manage the memory for memorize | storing the information regarding these other terminals separately from MIB. In that case, the MAC / PHY management unit 60 or the MAC common processing unit 20 can refer to / rewrite the other memory. Further, the MAC / PHY management unit 60 of the base station selects terminals that simultaneously allocate resource blocks for OFDMA communication based on various information related to the terminals as non-base stations or requests from the terminals in OFDMA communication (that is, It may also have a grouping function (selecting a terminal subject to OFDMA this time). Further, the MAC / PHY management unit 60 or the MAC processing unit 10 may manage the transmission rate applied to the MAC frame to be transmitted and the physical header. The MAC / PHY management unit 60 of the base station may define a support rate set that is a rate set supported by the base station. The support rate set may include a rate required to be supported by a terminal connected to the own station and an optional rate.

  The MAC processing unit 10 handles three types of MAC frames, a data frame, a control frame, and a management frame, and performs various processes defined in the MAC layer. Here, three types of MAC frames will be described.

  The management frame is used for management of communication links with other terminals. An example of the management frame is a beacon frame that broadcasts group attributes and synchronization information to form a wireless communication group that is a Basic Service Set (BSS) in the IEEE 802.11 standard. There are also frames exchanged for authentication or for establishing a communication link. Here, a state in which a certain terminal has exchanged information necessary for performing wireless communication with another terminal is expressed as an established communication link. Necessary information exchange includes, for example, notification of functions supported by the terminal itself (for example, support of the OFDMA system and various capabilities described later), negotiation on setting of the system, and the like. The management frame is generated based on an instruction received by the transmission processing unit 30 from the MAC / PHY management unit 60 via the MAC common processing unit 20.

  In relation to the management frame, the transmission processing unit 30 includes notification means for notifying other terminals of various information via the management frame. The notification means of the terminal as a non-base station transmits information indicating whether it is compatible with an OFDMA compatible terminal, an IEEE 802.11n compatible terminal, or an IEEE 802.11ac compatible terminal in a management frame to the base station. The type of the terminal itself may be notified. As this management frame, for example, there is an Association Request frame used in an association process, which is one of procedures for a terminal to authenticate with a base station, or a Reassociation Request frame used in a rear association process. The notification means of the base station may notify the non-base station terminal of the availability of support for OFDMA communication via a management frame. Examples of the management frame used for this include a Beacon frame and a Probe Response frame that is a response to a Probe Request frame transmitted by a non-base station terminal. The base station may have a function of grouping terminal groups connected to its own device. The above notification means of the base station may notify the group ID of each group assigned to each terminal via a management frame. An example of this management frame is a Group ID Management frame. The group ID may be, for example, a group ID defined in IEEE Std 802.11ac-2013. Further, when performing OFDMA communication in units of groups, the base station may notify information necessary for specifying resource blocks used by terminals belonging to the group via an arbitrary management frame.

  The reception processing unit 40 includes a reception unit that receives various types of information from other terminals via a management frame. As an example, the receiving unit of the base station may receive information on availability of support for OFDMA communication from a terminal as a non-base station. In addition, information on a channel width (maximum usable channel width) that can be handled when the terminal is a legacy terminal (IEEE802.11n compatible terminal, IEEE802.11ac compatible terminal) may be received. The receiving unit of the terminal may receive information on availability of support for OFDMA communication from the base station.

  The example of the information transmitted / received via the management frame described above is only an example, and various other information can be transmitted / received between terminals (including base stations) via the management frame. For example, an OFDMA-compatible terminal uses a resource block and / or channel that it desires to use in OFDMA communication, a non-interfering channel or non-interfering resource block that is carrier-sensed, or both You may choose from. Then, information regarding the selected resource block and / or channel may be notified to the base station. In this case, the base station may perform resource block allocation for OFDMA communication to each OFDMA compatible terminal based on the information. Note that the channels used in OFDMA communication may be all channels that can be used as a wireless communication system or some (one or more) channels.

  The data frame is used to transmit data to the other terminal in a state where a communication link is established with the other terminal. For example, data is generated in the terminal by a user's application operation, and the data is carried by a data frame. Specifically, the generated data is passed from the upper processing unit 90 to the transmission processing unit 30 via the MAC common processing unit 20, and the transmission processing unit 30 puts the data in the frame body field and adds a MAC header. A data frame is generated. The PHY processing unit 50 adds a physical header to the data frame to generate a physical packet, and the physical packet is transmitted via the analog processing unit 70 and the antenna 80. When the physical packet is received by the PHY processing unit 50, the physical layer is processed based on the physical header to extract a MAC frame (in this case, a data frame), and the data frame is passed to the reception processing unit 40. When receiving the data frame (when it is determined that the received MAC frame is a data frame), the reception processing unit 40 extracts the information of the frame body field as data, and the extracted data is passed through the MAC common processing unit 20. To the host processor 90. As a result, application operations such as data writing and reproduction occur.

  The control frame is used for control when a management frame and a data frame are transmitted / received (exchanged) with another wireless communication apparatus. As the control frame, for example, before starting the exchange of the management frame and the data frame, an RTS (Request to Send) frame exchanged with another wireless communication device to reserve a wireless medium, a CTS (Clear to Send) frame. As another control frame, there is a delivery confirmation response frame for confirming delivery of the received management frame and data frame. Examples of the delivery confirmation response frame include an ACK (Acknowledgement) frame and a BA (BlockACK) frame. Since the CTS frame is also transmitted as a response to the RTS frame, it can be said that the CTS frame represents a delivery confirmation response. The CF-End frame is also one of the control frames. The CF-End frame is a frame that announces the end of CFP (Contents Free Period), that is, a frame that permits access to the wireless medium. These control frames are generated by the transmission processing unit 30. Regarding the control frame (CTS frame, ACK frame, BA frame, etc.) transmitted as a response to the received MAC frame, the reception processing unit 40 determines whether the response frame (control frame) needs to be transmitted and generates a frame. Necessary information (control frame type, information set in the RA field, etc.) is output to the transmission processing unit 30 together with a transmission instruction. The transmission processing unit 30 generates an appropriate control frame based on information necessary for generating the frame and a transmission instruction.

  When the MAC processing unit 10 transmits a MAC frame based on CSMA / CA (Carrier Sense Multiple Access with Carrier Avidance), it is necessary to acquire an access right (transmission right) on the wireless medium. The transmission processing unit 30 measures transmission timing based on the carrier sense information from the reception processing unit 40. The transmission processing unit 30 gives a transmission instruction to the PHY processing unit 50 according to the transmission timing, and passes the MAC frame. In addition to the transmission instruction, the transmission processing unit 30 may instruct the modulation scheme and the encoding scheme used for transmission together. In addition to these, the transmission processing unit 30 may instruct transmission power. After obtaining the access right (transmission right), the MAC processing unit 10 is able to occupy the medium (Transmission Opportunity; TXOP). MAC frames can be exchanged continuously with the device. In TXOP, for example, a wireless communication device transmits a predetermined frame (for example, an RTS frame) based on CSMA / CA (Carrier Sense Multiple Access Carrier Avoidance), and a response frame (for example, a CTS frame) is correctly transmitted from another wireless communication device. Earned when received. When the predetermined frame is received by the other wireless communication device, the other wireless communication device transmits the response frame after a minimum frame interval (SIFS). In addition, as a method of acquiring TXOP without using an RTS frame, for example, a data frame that directly requests transmission of a delivery confirmation response frame by unicast (a frame having a shape in which frames are concatenated as described later, or a payload is concatenated). A management frame may be transmitted, and a delivery acknowledgment response frame (ACK frame or BlockACK frame) may be received correctly. Alternatively, it is a frame that does not request transmission of a delivery confirmation response frame from another wireless communication device, and a duration longer than the time required for transmission of the frame is set in the Duration / ID field (hereinafter, Duration field) of the frame. When a frame is transmitted, it may be interpreted that the TXOP of the period described in the Duration field has been acquired from the stage of transmitting the frame.

  The reception processing unit 40 manages the carrier sense information described above. The carrier sense information is managed for each channel, for example. This carrier sense information is based on the physical carrier sense information related to busy / idle of the medium (CCA) input from the PHY processing unit 50 and the medium reservation time described in the received frame. Both virtual carrier sense (Virtual Carrier Sense) information is included. If any one of the carrier sense information indicates busy, the medium is considered busy and transmission is prohibited during that time. In the IEEE 802.11 standard, the medium reservation time is described in the Duration field in the MAC header. When the MAC processing unit 10 receives a MAC frame addressed to another wireless communication device (not addressed to itself), the medium is virtually busy from the end of the physical packet including the MAC frame to the medium reservation time. Judge that there is. Such a mechanism for virtually determining that a medium is busy, or a period during which a medium is virtually busy is called a NAV (Network Allocation Vector). It can be said that the medium reservation time represents the length of a period for instructing suppression of access to the wireless medium, that is, the length of the period for delaying access to the wireless medium.

  Here, the data frame may be configured to connect a plurality of MAC frames or payload portions of a plurality of MAC frames. The former is called A (Aggregated) -MPDU in the IEEE 802.11 standard, and the latter is called A (Aggregated) -MSDU (MAC service data unit). In the case of A-MPDU, a plurality of MPDUs are connected in the PSDU. In addition to data frames, management frames and control frames are also subject to concatenation. In the case of A-MSDU, a plurality of data payloads MSDU are concatenated in the frame body of one MPDU. For both A-MPDU and A-MSDU, delimiter information (length information, etc.) is stored in the data frame so that the concatenation of a plurality of MPDUs and the concatenation of a plurality of MSDIs can be appropriately separated at the receiving terminal. Has been. Both A-MPDU and A-MSDU may be used in combination. In addition, the A-MPDU may target only one MAC frame instead of a plurality of MAC frames. In this case, the delimiter information is stored in the data frame. When the data frame is an A-MPDU or the like, responses for a plurality of MAC frames are transmitted together. In this case, a BA (BlockACK) frame is used instead of an ACK frame. In the following description and figures, the MPDU notation may be used, but this includes not only a single MAC frame but also the above-described A-MPDU or A-MSDU.

  According to the IEEE802.11 standard, a non-base station terminal joins a BSS (this is called an infrastructure BSS) formed mainly by a base station, and data frames can be exchanged within the BSS. A plurality of procedures are defined in stages. For example, there is a procedure called association, and an association request (Association Request) frame is transmitted from a terminal of a non-base station to a base station to which the terminal requests connection. The base station transmits an ACK frame for the association request frame, and then transmits an association response frame that is a response to the association request frame.

  The terminal stores the capability of its own terminal in the association request frame, and can notify the base station of the capability of its own terminal by transmitting it. For example, the terminal may transmit the association request frame with information for specifying a channel and / or resource block that can be supported by the terminal, or both, and a standard that the terminal supports. This information may also be included in a frame that is transmitted in a procedure called reassociation for reconnection to another base station. In this procedure, the terminal transmits a reassociation request frame to another base station that requests reconnection. The other base station transmits an ACK frame for the re-association request frame, and then transmits a re-association response frame that is a response to the re-association request frame.

  In addition to the association request frame and the reassociation request frame, a beacon frame, a probe response (Probe Response) frame, or the like may be used as the management frame. The beacon frame is basically transmitted by the base station, and can store a parameter indicating the BSS attribute and a parameter notifying the base station itself. Therefore, the base station may add information indicating whether or not the base station can support OFDMA communication as a parameter for notifying the capability of the base station itself. Moreover, you may notify the information of the support rate (Supported Rate) of a base station as another parameter. The support rate may include a mandatory rate and an optional rate. The probe response frame is a frame that is transmitted in response to reception of a probe request frame from a terminal that transmits a beacon frame. Since the probe response frame basically notifies the same content as the beacon frame, even if the probe response frame is used, the base station transmits its capability (OFDMA communication) to the terminal that transmitted the probe request frame. Supportability, support rate, etc.). By making this notification to the OFDMA-compatible terminal, the terminal can also enable, for example, the OFDMA communication function of the terminal itself.

  In addition, a terminal may notify information on a rate that can be executed by the terminal among the support rates of the base station as information to notify the base station of the capability of the terminal. However, with regard to an indispensable rate among the support rates, it is assumed that a terminal connected to the base station has an ability to execute the indispensable rate. Note that the base station may not define the support rate, and in this case, the terminal can execute an essential rate set according to the type of the physical layer.

  In addition, notification of other information can be omitted from the information handled above if the information becomes indispensable. For example, if a capability corresponding to a certain new standard or specification is defined, and if it corresponds to that, it is an OFDMA-compatible terminal, it is not necessary to explicitly notify that it is an IFDMA-compatible terminal. .

  FIG. 3 shows a wireless communication system according to the present embodiment. This system includes a base station (AP: Access Point) 100 and a plurality of terminals (STA: STATION) 1 to 8. The base station 100 and subordinate terminals 1 to 8 form a BSS (Basic Service Set) 1. This system is a wireless LAN system conforming to the IEEE 802.11 standard using CSMA / CA (Carrier Sense Multiple Access with Carrier Avidance). An OFDMA compatible terminal and a legacy terminal coexist, and as an example, terminals 1 to 6 are OFDMA compatible terminals, and terminals 7 and 8 are legacy terminals. This will be described below assuming this.

  In the system of FIG. 3, when performing resource block-based OFDMA communication, OFDMA is performed between a non-target terminal of OFDMA (a terminal not designated as a target for this OFDMA communication), a target terminal, and a base station. It is necessary to consider the fairness of medium access opportunities after communication. When a non-target terminal receives a frame (more specifically, a physical packet including a frame) simultaneously transmitted from a base station or another group of terminals by OFDMA, it normally decodes only up to a common preamble in the header of the physical packet. There may be a case where it is not performed (for example, when it is determined from the contents of the common preamble that a frame addressed to the terminal itself is not included in the physical packet). In this case, an error is detected in the physical layer, and the error is notified to the MAC layer via the SAP (Service Access Point). Due to this, at the next medium access, the MAC layer activates an extended interface space (EIFS) time as a fixed period of carrier sense performed before backoff. Since the EIFS time is longer than the fixed period (DIFS / AIFS [AC]) of carrier sense performed during normal medium access, the non-target terminal that activates the EIFS time and the normal DIFS / AIFS [AC] during the next access. Unfairness occurs with terminals that start time (such as OFDMA target terminals and base stations).

  Current EIFS time activation conditions include a case in which the PLCP (physical layer convergence procedure) reception process could not be completed normally and an error detected in the FCS check of the MAC frame. If the PLCP reception process could not be completed normally, PHY-RXEND. An error notification is sent to the MAC layer by indication, and the MAC layer is controlled to activate the EIFS time. The PLCP reception process could not be terminated normally and PHY-RXEND. As an example of notification of an error in indication, it is incompatible with MCS (Modulation and Coding Scheme) notified in the physical header (Unsupported Rate), format violation (Format Violation), carrier lost (Carrier Lost) and so on. The case where the above-mentioned non-target terminal of OFDMA performs decoding only halfway through the header of the physical packet corresponds to the case where the PLCP reception process could not be completed normally, and PHY-RXEND. It is considered that error notification is sent to the MAC layer by indication.

  Hereinafter, it will be specifically described with reference to FIG. 4 that unfairness of access to a wireless medium occurs between an OFDMA target terminal and base station and an OFDMA non-target terminal after OFDMA communication. FIG. 4 shows an example of an operation sequence when OFDMA communication is performed between the base station (AP) 101 and the terminals (STA) 1 to (STA) 4. However, for the sake of explanation here, although the terminals 1 to 4 and the non-target terminals 5 and 6 have the capability of performing OFDMA communication and the capability is enabled, there are problems related to the features of this embodiment. It is assumed that there is no function to cancel fairness. An example of operation of terminals 5 and 6 that are non-target terminals of OFDMA is also shown below FIG.

  In this sequence example, the base station 101 and the terminals 1 to 4 perform OFDMA communication (both downlink transmission and uplink transmission) using a continuous frequency band of 20 MHz width of one channel. In the base station, one or a plurality of continuous subcarriers are allocated to each terminal as resource blocks based on subcarrier groups orthogonally arranged in the 20 MHz width band. In this example, it is assumed that four resource blocks 1, 2, 3, 4 are set in one channel, and resource blocks 1 to 4 are assigned to terminals 1 to 4 in order from the higher frequency side. If it demonstrates according to the example shown previously in FIG. 2, it is equivalent to the case where K = 4 and four resource blocks set in the channel M are assigned to the terminals 1 to 4 in order from the higher frequency side. To do.

  The base station 101 simultaneously transmits MAC frames (downlink OFDMA transmission) to the terminals 1 to 4 using the resource blocks 1 to 4 in the channel. More specifically, a physical packet including a frame addressed to the terminals 1 to 4 is transmitted by the resource blocks 1 to 4 based on the access right on the medium for one frame acquired in advance by carrier sense of the channel. In the example of FIG. 4, the frame length of each MAC frame included in the physical packet is the same.

  FIG. 5A shows a schematic format example of a physical packet according to the present embodiment. This format includes a physical header and a data field. L-STF, L-LTF, and L-SIG fields are arranged on the head side of the physical header, followed by the preamble 1 and preamble 2 fields according to the present embodiment. Preamble 1 and preamble 2 may be newly defined fields, or may be extended fields after L-STF, L-LTF, and L-SIG in existing standards. For example, as an existing standard, VHT-SIG-A in the IEEE802.11ac physical packet format may be expanded as preamble 1, and VHT-SIG-B may be expanded as preamble 2. There may be other fields between Preamble 1 and Preamble 2, at least one before Preamble 1 and after Preamble 2. For example, STF and LTF fields may be arranged in this order between preamble 1 and preamble 2. The STF and LTF fields may be newly defined fields, may be extensions of existing standard VHT-STFs and VHT-LTFs, or may be the same fields as these.

  L-STF, L-LTF, and L-SIG are fields that can be recognized by legacy terminals such as IEEE802.11a (the leading “L” indicates legacy), and signal detection, frequency correction, and transmission rate (or MCS). ) Etc. are stored. L-STF, L-LTF, and L-SIG need to be transmitted in a channel width band (20 MHz) so that legacy terminals can receive and decode them. For this reason, when OFDMA transmission is performed to a plurality of terminals using a plurality of resource blocks in one channel, the contents of the L-STF, L-LTF, and L-SIG of the physical packet transmitted to each terminal must be the same. . Thereby, even a legacy terminal can receive and decode L-STF, L-LTF, and L-SIG common to these physical packets. Note that L-STF, L-LTF, and L-SIG may be collectively referred to as a legacy field. In FIG. 4, in order to express that the legacy field is transmitted in the channel width band (20 MHz), the legacy field is described by a rectangle extending over four resource blocks.

  The preamble 1 transmitted by the base station stores information that can be commonly understood by OFDMA-compatible terminals. As information set in the preamble 1 of the header of a physical packet to be OFDMA transmitted from a base station to a plurality of terminals, there is information for specifying a plurality of terminals (target terminals) that are transmission targets in OFDMA, for example. The information for identifying a plurality of terminals may be information (identifier) for individually identifying these terminals, or may be a group ID of a group shared by the plurality of terminals. The group ID is assigned by the base station and notified to the terminal when the terminal joins the BSS of the base station (that is, during the association process) or after joining. The base station can generate and manage a plurality of groups, and grasps a group of terminals belonging to each group. The same terminal may belong to a plurality of groups. When the group to which the terminal belongs is changed, the changed group ID is notified to the terminal. Examples of information for identifying individual terminals include an association ID (AID) given from the base station at the time of association with the base station, a MAC address of the terminal, or both. The information for individually identifying the terminal is not limited to the example described here as long as the terminal can be identified.

  Further, as another example of information set in the preamble 1, there is information for specifying resource blocks used by OFDMA target terminals. For example, when the terminals 1 to 4 are designated as the target terminals, information for designating the resource blocks 1 to 4 may be set for the terminals 1 to 4, respectively. Specifically, a plurality of fields for specifying the number of resource blocks are provided, and the resource block to be used can be specified from the number of resource blocks specified in the position field for the terminal itself (sometimes referred to as a user position). Good. In this case, the position of the field for the own terminal is notified in advance at the time of association or at an arbitrary timing thereafter. The allocated number of resource blocks may be allocated from terminals having higher field position priorities. At this time, the allocation order is determined for the plurality of resource blocks, and the resource blocks are allocated in this order. In the case of the above example, 1 is set as the number of resource blocks in the fields for terminals 1 to 4, respectively. In this case, it is determined in advance that the allocation is performed in the order of the resource blocks 1 to 4.

  In addition, when identifiers for individually identifying resource blocks are defined, resource block identifiers may be arranged in the field position (user position) for each terminal in the preamble 1 by the number of resource blocks to be used. Good. Alternatively, correspondence information between an identifier such as an AID of a terminal and an identifier of a resource block used by the terminal can be set in the preamble 1.

  In addition, the preamble 1 may include information on an error correction code scheme (LDPC (Low Density Parity Check), convolution, etc.) used in at least one of the preamble 2 and the data field.

  The preamble 1 may include the total number of resource blocks used in OFDMA. For example, when resource blocks used in a channel are specified according to the total number of resource blocks used in one channel width band (for example, the total number from the higher or lower frequency side), the total number Thus, a resource block used in OFDMA communication can be specified. Alternatively, when the arrangement of resource blocks (correspondence between resource blocks and subcarriers) varies according to the total number, the resource block used in OFDMA communication may be specified from the total number.

  In addition, the preamble 1 may include information on the interval between resource blocks (the number of subcarriers existing between adjacent resource blocks). For example, if there are multiple allocation patterns of resource blocks used in OFDMA in the channel and the interval between resource blocks differs in each allocation pattern, identify the resource block used in OFDMA communication from the information related to the interval It is possible to do.

  Each terminal may grasp the correspondence between each of the plurality of resource blocks and the subcarrier group belonging to the resource block. This correspondence may be predefined in the system or specification, or the base station sets the correspondence, and at the time of association with the terminal or at any other timing, a beacon frame, an association response frame, or a new It may be notified by a frame defined in the above, an arbitrary management frame, or the like. As described above, the correspondence between resource blocks and subcarriers may change depending on the number of resource blocks used. The resource block used by the terminal may be determined in advance, and in this case, setting of information for specifying the resource block used by the terminal in the preamble 1 may be omitted. Note that information that can be understood by the base station (such as information for specifying the base station) is stored in the preamble 1 that is uplink transmitted from the terminal to the base station.

  The preamble 1 is transmitted in the channel width band (20 MHz) as in the legacy field. For this reason, when a physical packet is OFDMA transmitted to a plurality of terminals using a plurality of resource blocks in one channel, the contents of the print 1 of the physical packet transmitted to each terminal must be the same. The OFDMA compatible terminal that has received the preamble 1 receives and decodes a signal in the channel width band. In FIG. 4, in order to express that the preamble 1 is transmitted in the channel width band (20 MHz), the preamble 1 is described as a rectangle that straddles four resource blocks. L-STF, L-LTF, L-SIG, and preamble 1 may be collectively referred to as a common preamble.

  The preamble 2 stores information necessary for decoding the data field for each corresponding resource block. For example, a modulation and coding scheme (MCS) necessary for decoding a MAC frame in a data field transmitted by the resource block is stored. The preamble 2 is transmitted for each target terminal in a band for each resource block instead of one channel width band. That is, the preamble 2 is frequency multiplexed. The target terminal of OFDMA determines that its own terminal is specified in preamble 1, then receives preamble 2 in the resource block specified in preamble 1 or specified in advance, and decodes preamble 2 to obtain data. Information such as MCS necessary for decoding the field (MAC frame) is acquired. The preamble 2 is transmitted for each terminal in a band for each resource block, and may have different contents. However, there is no problem even if the contents of each preamble 2 are the same. Since the preamble 2 and the data field are common in that each resource block is transmitted, it may be considered that there is a field including the preamble 2 and the data field. In this case, the field includes the preamble 2 and the data field, and may include other fields as long as the field is transmitted in the same resource block. In FIG. 4, in order to express that the preamble 2 is transmitted in a band for each resource block, the preamble 2 is described as a rectangle separated between resource blocks. The numbers described in the rectangle representing the preamble 2 represent the number of the destination terminal for convenience. For example, a rectangular preamble 2 in which the numeral 1 is entered means that information addressed to the terminal 1 is included. It does not necessarily mean that information specifying a terminal is included in the preamble 2 (of course, information specifying a terminal may be included).

  A MAC frame is stored in the data field. Similar to the preamble 2, the MAC frame is transmitted for each terminal in the band for each resource block. That is, the data field is transmitted by frequency multiplexing. The MAC frame transmitted in each resource block is a frame addressed to a corresponding terminal, and the contents of those MAC frames may be different or the same. The MAC frame transmitted in each resource block may be a data frame, a management frame, or a control frame, or a combination thereof. Further, the data frame may be not only a single MAC frame but also an aggregation frame (A-MPDU) obtained by aggregating a plurality of MAC frames. In the example of FIG. 4, a data frame is set in the data field of a physical packet transmitted from the base station in downlink OFDMA. This is described as “MPDU (Data)” in the figure. As described above, “MPDU” may refer not only to a single MAC frame but also to an aggregation frame (A-MPDU) or the like. In the present embodiment, it is assumed that the frame is an aggregation frame. In FIG. 4, in order to express that a MAC frame (data frame) is transmitted in a band for each resource block, the MAC frame is described in a rectangle separated between resource blocks as in the preamble 2. The numbers written in each rectangle represent the destination terminal number for convenience. For example, a rectangular MAC frame in which the numeral 1 is entered means that the frame is addressed to the terminal 1 (for example, the RA address is the MAC address of the terminal 1).

  The format of each field of the physical header has been described mainly assuming the case of downlink OFDMA communication. However, when other communication is performed, the field (preamble 1 or preamble 2 or 2) is selected according to the type of communication. The format of both of these may be different.

  As described above, in the physical packet transmitted from the base station by OFDMA, the legacy field and preamble 1 are transmitted with the channel bandwidth, and the preamble 2 and data field are transmitted for each resource block. That is, in this case, as shown in FIG. 5B, the physical packet transmitted from the base station by OFDMA includes a legacy field and preamble 1 common to each target terminal, a plurality of preambles 2 and a plurality of data for each terminal. Field. The physical header includes a legacy field and preamble 1 common to each target terminal, and a plurality of preambles 2 for each terminal.

  FIG. 6 shows a basic format example of the MAC frame. The data frame, management frame, and control frame basically have such a frame format. This frame format includes fields of a MAC header, a frame body, and an FCS. The MAC header includes Frame Control, Duration, Address 1, Address 2, Address 3, Sequence Control, QoS Control, and HT (High Throughput) control fields. All of these fields need not be present, and some fields may not be present. There may also be other fields not shown in FIG. For example, an Address4 field may further exist. The Address 1 field contains the destination address (Receiver Address; RA), the Address 2 field contains the source address (Transmitter Address; TA), and the Address 3 field contains the BSSID that is the identifier of the BSS depending on the use of the frame. (Basic Service Set IDentifier) (in some cases, a wildcard BSSID that targets all BSSIDs by putting 1 in all bits) or TA is entered. In the Frame Control field, two fields of Type and Subtype are set as described above. Data frames, management frames, and control frames are roughly classified in the Type field, and detailed classification among the roughly classified frames, for example, identification of BA frames, BAR frames, and Beacon frames in management frames is performed. This is done in the Subtype field. The Duration field describes the medium reservation time as described above. When a MAC frame addressed to another terminal is received, the medium is virtually busy from the end of the physical packet including the MAC frame over the medium reservation time. It is determined that Such a mechanism for virtually determining that a medium is busy, or a period during which a medium is virtually busy, is referred to as NAV (Network Allocation Vector) as described above. The QoS field is used for performing QoS control in which transmission is performed in consideration of frame priority. In the management frame, an information element (Information element; IE) to which a unique Element ID (IDentifier) is assigned can be set in the Frame Body field, and one or a plurality of information elements can be set. The information element is identified by an Element ID, and has an Element ID field, a Length field, and an Information (Information) field. The information field stores the content of information to be notified, and the Length field stores length information of the information field. In the FCS field, FCS (Frame Check Sequence) information is set as a checksum code used for frame error detection on the receiving side. Examples of FCS information include CRC (Cyclic Redundancy Code).

  In the sequence of FIG. 4, the terminals 1 to 4 receive and decode physical packets transmitted from the base station 101 using a plurality of resource blocks, and obtain MAC frames of resource blocks assigned to the own terminal. An error check is performed based on the FCS of the acquired MAC frame. If there is no error, the header and frame body field (data body) of the MAC frame are processed. For example, if it is a data frame, the data stored in the frame body field is output to the upper layer, and if it is a management frame or a control frame, an operation for management or control according to the information stored in the frame body field I do. Here, it is assumed that the MAC frame is an aggregation frame including a plurality of data frames.

  The terminals 1 to 4 generate a delivery confirmation response frame including bitmap information indicating whether or not each data frame has been successfully received based on an error check result of each data frame in the aggregation frame. Then, the terminals 1 to 4 transmit physical packets including a BA frame (Block ACK frame), which is a delivery confirmation response frame after SIFS time from the completion of frame reception from the base station, in the same resource block as the MAC frame is received. To do. Thereby, uplink OFDMA transmission from the terminals 1 to 4 to the base station 101 is performed. It is assumed that the BA frame length transmitted by each terminal is the same. SIFS time is an example, and other time may be used as long as it is a fixed time. In the following description, all references to SIFS time follow this. As for the legacy field and preamble 1 of the header of the physical packet including the BA frame, the preamble is a field after the preamble 1 and is transmitted in the channel width band (20 MHz width band) in the same manner as the physical packet transmitted by the base station by OFDMA. 2 and the MAC frame are transmitted in the band of each resource block. In order to express these, in FIG. 4, the legacy field and preamble 1 in the header of the physical packet transmitted by each terminal are described in a rectangle across four resource blocks, and the following preamble 2 and MAC frame are respectively It is described in a rectangle included only in the resource block. “AP” described in the rectangle representing the MAC frame means that the destination of the MAC frame is the base station (for example, the RA address is the BSSID or the MAC address of the base station).

  Here, the physical packet OFDMA transmitted from the base station in the resource blocks 1 to 4 is also received by terminals other than the terminals 1 to 4 as long as they are terminals that can receive signals from the base station. For example, a physical packet is also received by non-target terminals (here, terminals 5 and 6). At this time, if the non-target terminal is normal (when it does not have the function of the present embodiment), the decoding of the preamble 1 in the header of the physical packet does not perform decoding of the field after that, It is considered that an error is detected on the assumption that the packet has not been received normally. In this case, as described above, the non-target terminal activates the EIFS time by carrier sense at the next channel access. For example, when the downlink OFDMA transmission of the physical packet from the base station of FIG. 4 is completed, the CCA becomes idle, and when the non-target terminal of OFDMA performs carrier sense to acquire the channel access right, before the backoff The EIFS time is activated as the carrier sense for a certain time (see “EIFS activation 1” in FIG. 4). Similarly, when a plurality of physical packets are OFDMA transmitted from a plurality of target terminals to the base station, the non-target terminal cannot normally receive the physical packet or the MAC frame in the physical packet, resulting in a reception error. For example, as a result of decoding the legacy field and the preamble P1, it is determined that the physical packet is irrelevant to the own terminal, and the reception error is detected assuming that the subsequent field is not decoded. Even if the preamble 2 or MAC frame in the subsequent field is received, it cannot be normally decoded because a signal in which signals of a plurality of terminals overlap is decoded, and any reception error is detected. As a result, the EIFS time is activated as a carrier sense for a fixed time before backoff by carrier sense at the next channel access. For example, as shown in FIG. 4, when uplink OFDMA transmission of physical packets from a plurality of target terminals is completed, the CCA becomes idle, and when carrier sense is performed in order to acquire channel access rights, The EIFS time is activated as carrier sense for a certain time (see “EIFS activation 2” in FIG. 4). Regarding the reception error, in addition to the examples described here, there may be the above-described examples, for example, MCS non-compliant (Unsupported Rate), loss of carrier (Carrier Lost), and the like.

Here, the EIFS time (EIFS period) will be described. As an example, the EIFS time is defined as a sum of the SIFS time, the ACK frame time length (the length of time required to transmit an ACK frame), and the DIFS / AIFS [AC] time.
That is,
EIFS time = SIFS time + ACK frame time length + DIFS / AIFS [AC] time.

  AIFS is an IFS determined by adding the concept of QoS (Quality of Service) to DIFS. “AC” in AIFS [AC] is an access category, and an AIFS value is set according to a priority (access category) determined according to the type of data to be transmitted. The higher the priority, the smaller the value of AIFS (the setting of the back-off time may also be advantageous).

  When OFDMA target terminals and base stations perform carrier sense to acquire channel access rights after OFDMA communication, unless there are special circumstances such as reception errors, etc. As carrier sense, a normal time, ie, DIFS / AIFS [AC] time is activated. Here, “DIFFS / AIFS [AC] time” means one time of DIFS and AIFS [AC]. When the QoS of the data is not considered, the DIFS time is indicated, and when the QoS is considered, the AIFS [AC] time determined according to the type of data to be transmitted is indicated. From the relational expression of the EIFS time described above, the EIFS time is larger than the DIFS / AIFS [AC] time, so that a terminal that detects a reception error is more disadvantageous in acquiring access right on the medium than a terminal that does not. . This is schematically shown in FIG. 7A shows the carrier sense time when EIFS time is activated (addition of EIFS time and back-off time), and FIG. 7B shows the carrier sense time when DIFS / AIFS [AC] time is activated ( (DIFS / AIFS [AC] time and backoff time) are schematically shown. Since the EIFS time is longer than the DIFS / AIFS [AC] time, it can be seen that a terminal that has detected a reception error has a longer standby time in acquiring the access right, which is disadvantageous. Note that the values of the back-off time following the EIFS time and the DIFS / AIFS [AC] time are determined randomly, and carrier sense is continuously performed during the back-off time (back-off). Note that backoff may be omitted.

  In order to eliminate the above-mentioned unfairness, one of the features of the OFDMA compatible terminal according to this embodiment is to perform the following operation. When an OFDMA-compatible terminal according to the present embodiment receives a physical packet transmitted from a base station through downlink OFDMA, if the terminal is not designated as an OFDMA target terminal in preamble 1, that is, a non-target terminal In this case, at least one resource block among the plurality of resource blocks is specified, and the MAC frame is extracted from the data field of the specified resource block. In order to extract the MAC frame, the data field may be decoded using information (such as MCS information) set in the preamble 2 arranged before the MAC frame. The non-target terminal that has extracted the MAC frame, based on the value set in the Duration field of the header (value related to the length of the period during which access to the medium is suppressed), the length of the value from the completion of reception of the MAC frame Only set the NAV. That is, the non-target terminal determines that the RA address of the extracted MAC frame is not the MAC address of the terminal, that is, is not the MAC frame addressed to the own terminal, so that only the length of the value set in the Duration field is obtained. Set the NAV. The band for which the NAV is set is the channel width band in which the physical packet is transmitted.

  Here, which resource block of the plurality of resource blocks the non-target terminal specifies may be determined in advance. For example, when a resource block to be used when the terminal is designated as an object of OFDMA communication is determined in advance, the resource block may be selected. Alternatively, any resource block may be selected as long as any of the plurality of resource blocks can be received and decoded. Further, when the resource block used by the base station for OFDMA transmission is variable, it is possible to decode the preamble 1 to grasp the resource block used and select a resource block from the grasped resource blocks. Good. In addition, in the case of a non-target terminal in which a compatible MCS is restricted among a plurality of MCSs that can be used in the BSS1, the preamble 2 of each resource block is decoded, and an MCS resource block that can be supported by the terminal is obtained. The MAC frame may be acquired by specifying and decoding the data field of the specified resource block by the MCS.

  FIG. 8 shows an example of an operation sequence when the terminals 5 and 6 that are non-target terminals set NAV based on the value described in the Duration field of the acquired MAC frame. Except for the operation in which the terminals 5 and 6 set the NAV, the operation is the same as in FIG. It is assumed that the downlink MAC frames (data frames) have the same length (time length), and the uplink MAC frames (BA frames) have the same length. The terminals 5 and 6 decode the data field based on the preamble 2 included in one of the plurality of resource blocks in the physical packet transmitted by the base station 101 and transmitted by OFDMA, and obtain the MAC frame. Then, based on the value of the Duration field of the MAC frame header, the NAV is set from the end of the MAC frame. The value of the Duration field is set according to the end of the MAC frame transmitted from the terminals 1 to 4 by uplink OFDMA. In the example of FIG. 8, the end time of the MAC frame for uplink OFDMA transmission is the same, so the end of the NAV period is also the same. During the NAV, the EIFS time is controlled not to be activated even if the cause of the reception error as described above occurs. Therefore, even if an uplink physical packet is received from another terminal group during the NAV, the EIFS time activation problem does not occur. Note that the time at the end of the NAV period may be a time after or before the end of the uplink MAC frame. When set to the previous time, it should be at least the time after the timing when the non-target terminal cannot recognize that it is the reception of the physical packet (or the reception of the MAC frame) transmitted in the uplink and can only recognize it as busy. desirable. For example, at least a time after the beginning of the legacy field is set.

  After the NAV period elapses, the terminals 5 and 6 perform carrier sense in order to acquire the access right on the medium. Since NAV is set during uplink OFDMA communication and activation of the EIFS time is suppressed, the DIFS / AIFS [AC] time is activated as usual. On the other hand, when the base station 101 and the terminals 1 to 4 start carrier sense after uplink OFDMA transmission in order to acquire the access right on the medium, the DIFS / AIFS [AC] time is similarly activated. Therefore, the unfairness of the opportunity to acquire the access right between the target terminal and the base station and the non-target terminal is solved.

  When the length of each downlink MAC frame from the base station is different, padding data may be added to the end of the short MAC frame to adjust the length to be the same. Alternatively, when considering the case where the length of each uplink MAC frame (BA frame) as a response is different, the following may be performed. That is, for each MAC frame transmitted from the base station in the downlink OFDMA, the length of the NAV period is set so that the end of the NAV period set corresponding to each MAC frame is the same time. Thereby, for example, even when the end of the uplink MAC frame (BA frame) as a response is different, the fairness among at least non-target terminals can be maintained by aligning the end of the NAV period. Further, by making the end time coincide with the end of the longest MAC frame among uplink MAC frames, fairness can be maintained among all terminals including the non-target terminal, the target terminal, and the base station.

  When the base station transmits a plurality of frames to a plurality of terminals (when transmitting a plurality of frames to terminals 1 to 4 by downlink OFDMA in the example of FIG. 8), the plurality of frames to be transmitted are the same. It may be different or different. As a general expression, when it is expressed that a base station transmits or receives a plurality of frames or a plurality of Xth frames, these frames or the Xth frames may be the same or different. X can be set to any value depending on the situation.

  In the above-described operation sequence example, when an OFDMA non-target terminal has a power save mode function, the operation may be changed depending on whether or not the power save operation is performed. For example, a power save mode activated parameter is provided. If the value of this parameter is true (1), the power save mode operation is performed, and if it is false (0), the power save mode operation is not performed. At this time, when the parameter is false (0), the non-target terminal specifies at least one of the resource blocks and decodes the MAC frame to set the NAV, and if true, specifies the resource block and decodes the MAC frame. You may not do it. Or, it has a parameter of power management mode, and if the value of the parameter is active (1), it is not in the power save mode, and if it is in power save (2), it is in the power save mode. In this case, when the value of the parameter is active (1), the non-target terminal specifies at least one of the resource blocks and decodes the MAC frame to set the NAV. If the parameter value is power save (2), Block identification and MAC frame decoding may not be performed. Or, regardless of power saving, the terminal has a parameter related to whether or not the operation related to the present embodiment is executed, the value of the parameter indicates execution (1), and the terminal is designated as an OFDMA target. If not, the NAV is set by identifying at least one of the resource blocks and decoding the MAC frame. On the other hand, if execution is not performed (0) and the terminal is not designated as an OFDMA target, the resource block identification and the MAC frame decoding may not be performed. Thereby, power consumption can be saved. At this time, even if the resource block is not specified and the MAC frame is not decoded, it is not handled as a physical layer reception error, and control may be performed so that EIFS time is not activated internally. The parameter value may be set by user input or may be switched according to the remaining battery level of the terminal. For example, in a state where power saving is required, such as when the remaining battery level is equal to or less than a threshold value, the parameter value may be set to no execution (0). The parameter value switching may be performed by the MAC / PHY management unit 60 or the MAC processing unit 10.

  In addition, in order to prevent activation of the EIFS time after the end of OFDMA communication (completion of transmission of BA frame by each target terminal), BA frames are not transmitted from each target terminal in order of legacy formats (existing standards). A configuration in which the BA frame is transmitted in the format) is also conceivable. In this case, the non-target terminal (and also the legacy terminal) can normally receive the BA frame (it is also expected to set the NAV) and prevent activation of the EIFS time. However, in this configuration, since the BA frame cannot be transmitted simultaneously, the efficiency is lowered. On the other hand, in the present embodiment, even when the BA frame is OFDMA transmitted as shown in FIG. 8, the activation of the EIFS time of the non-target terminal can be prevented, so that the efficiency can be prevented from decreasing.

  As described above, in this embodiment, an OFDMA non-target terminal also extracts a MAC frame addressed to another terminal using at least one resource block, and sets the NAV by interpreting the Duration field. Whether or not it has the ability to set such NAV is set as Capability, and the OFDMA compatible terminal according to the present embodiment may notify the base station. The notification may be performed by, for example, an association request frame or the like at the time of the association process, or may be performed by a notification by a management frame or the like at an arbitrary timing after the association. The base station may control the execution of the OFDMA communication based on the notified capability. For example, when the ratio of the number of terminals having the above capabilities among the terminals connected to the own station is equal to or less than a threshold value, it may be determined that the OFDMA communication is not performed or limited. Alternatively, it may be determined that the OFDMA communication is executed only when the ratio is larger than the threshold value. Determinations and controls other than those described here may be performed.

  In this embodiment, in the received physical packet, the MAC frame of the resource block identified as described above (the MAC frame not addressed to the own terminal) is extracted, and the NAV is set according to the value set in the Duration field. As a result, the activation of the EIFS time is prevented, and after the OFDMA communication, the opportunity for acquiring the access right can be set to the same conditions as those of the target terminal and the base station of the OFDAM.

  In the above-described sequence, the data field length (MAC frame length) of each resource block transmitted by OFDMA from the base station is the same (if the data length transmitted from each terminal is different, it is adjusted by padding data). As another example, as shown in FIG. 8A, the present embodiment can also be applied to cases where the data field length (PSDU length) of each resource block is different, and three examples of methods in this case are shown below.

  As a first method, the value of each NAV (Duration field value) is adjusted and set so that the end of the NAV for each terminal is the same time. In this case, if the PSDU length (or MPDU length) of each resource block is different, the value set in the Duration field of each MAC frame also differs accordingly. Thereby, the end of the NAV can be matched, and for example, the end of each NAV can be matched with the end of the physical packet transmitted in the uplink OFDMA. Also by this, the same effect as the sequence of FIG. 8 can be obtained. The OFDMA target terminal completes the reception of the MAC frame at different timings, but the SIFS time is measured from the time when the carrier sense is performed with the channel width and becomes idle, or the MAC that completes the reception is the latest. The end of the frame (more specifically, the end of the physical packet) may be calculated by an arbitrary method (for example, the following second method), and the SIFS time may be measured from that point. Thereby, the timing of uplink transmission of each target terminal can be matched.

  As a second method, information for calculating the length of a physical packet to be transmitted in downlink OFDMA (the length up to the end of the longest PSDU when viewing PSDUs addressed to a plurality of terminals as one) is physically used. Set in the L-SIG field or another field of the header. The terminal (non-target terminal) calculates the length (occupation time) of the physical packet from the information in the field, and sets the NAV after the occupation time. The length (occupation time) of the physical packet is T2-T1 in the example of FIG. 8A. A common NAV value is set in the Duration field of each MAC frame. At this time, the end of the NAV is the time of the end of each BA frame (more specifically, a physical packet) transmitted in uplink OFDMA (in FIG. 8A). Match with T3). Note that the target terminal of OFDMA can match the timing for uplink transmission in the same manner as in the first method. Here, as an example of setting information for calculating the length (occupation time) of the physical packet, the Rate field and Length field (defined in the IEEE 802.11 standard) of the L-SIG field may be used. . For example, the base station calculates a physical packet length (occupation time) based on a plurality of PSDUs (MAC frames or the like) addressed to a plurality of terminals, that is, a time length required for receiving the physical packet at an actual rate (for example, 72 Mbps) calculate. The base station determines the values of the Rate field and the Length field so that the physical packet length can be calculated from the values of the Rate field (rate field) and the Length field (length field). For example, a value representing 6 Mbps is set in the Rate field. In the Length field, when a physical packet is received at 6 Mbps, a data length (which may be the number of octets or another unit) that matches the physical packet length calculated above is set. (Note that since the actual reception rate is higher than 6 Mbps, the value of the Length field is considered to be shorter than the actual packet length. The actual rate is specified from, for example, preamble 2). The non-target terminal calculates the physical packet occupation time (PPDU occupation time) from the values of the Rate field and Length field of the L-SIG field, and reads from any one MAC frame after the calculated occupation time. The NAV is set according to the value of the Duration field (the NAV value of each MAC frame is common as described above). No matter which resource block is decoded, the NAV end time is the same. Note that the value set in the Rate field is not limited to 6 Mbps, and may be another value.

  As a third method, before the base station starts downlink OFDMA, the terminal always sets the maximum time length (T2-T1 length) as the end time (that is, packet length) of the physical packet (PPDU) for downlink transmission. )) Is assumed. In this case, the base station sets the same NAV value for each MAC frame transmitted in the downlink. This is a configuration that assumes a case in which the terminal has a configuration for receiving the entire PPDU, not the resource block for the terminal itself. That is, the terminal does not determine the end of the PSDU only for the resource block for the terminal itself, but performs the reception process for the entire PPDU. In this case, the end of the longest PSDU is determined. Even when a non-target terminal receives a physical packet transmitted in downlink, the entire PPDU is received, the end of the PPDU (the end of the longest PSDU) is determined, and the NAV is set therefrom. What is necessary is just to acquire the length of NAV from the Duration field of the MAC frame of arbitrary resource blocks.

  In the first to third methods described above, the length of the BA frame transmitted from each target terminal is the same, but when the length of the BA frame is different (see FIG. 12 described later) NAV may be adjusted as appropriate. For example, the value of each NAV may be determined within the framework of the first to third methods so that the end of each NAV matches the end of the BA frame whose transmission completion of the BA frame is the slowest. Further, as will be described later with reference to FIG. 15 or FIG. 17, the base station may transmit a BAR frame after downlink OFDMA transmission, and cause the target terminal to transmit a BA frame using uplink OFDMA as a response. Good. 8 and 8A described above, one frame exchange (transmission / reception) is performed between the downlink OFDMA transmission from the base station and the uplink OFDMA transmission from the target terminal. The same frame exchange may be performed once or a plurality of times. The type of frame to be transmitted / received is not limited to the combination of the data frame and the BA frame.

  FIG. 9 shows a flowchart of an example of the operation of the base station according to the present embodiment. The base station determines a plurality of terminals to be subjected to OFDMA, and determines the length of the period related to NAV for each terminal (S11). Specifically, from the length of each of the plurality of MAC frames transmitted to the plurality of terminals and the BA frame length (more specifically, the physical packet length including the BA frame) responded from each terminal, the end of the period of each NAV The length of each NAV period is determined so that the times of At this time, for example, the time at the end of the NAV period is set to the end of the BA frame responded from each terminal (or the end of the BA frame that is most slowly received when the end of each BA frame is different). When the lengths of a plurality of MAC frames transmitted to a plurality of terminals are different, padding data may be added to the end of a short MAC frame so that the lengths are the same. The base station generates, for each terminal, a MAC frame in which a value relating to the determined length of the NAV period is set in each Duration field (S12). The base station stores each of these MAC frames in the data field and adds a physical header to generate a physical packet (S12). The physical header includes a legacy field, a preamble 1 including information (group ID and the like) for specifying a plurality of terminals, and a preamble 2 for each terminal including information for decoding a MAC frame.

  The base station transmits the legacy field and preamble 1 of the physical packet in the channel width band, and then transmits the preamble 2 and the data field (MAC frame) by OFDMA (S13).

  The base station receives a physical packet including an acknowledgment frame (BA frame) including information regarding the success or failure of reception of the MAC frame from the plurality of terminals by OFDMA after SIFS time from the transmission of the plurality of MAC frames (S14). .

  FIG. 10 is a flowchart of the operation when the terminal (OFDM compatible terminal) according to the present embodiment receives a physical packet transmitted from the base station by OFDMA.

  The terminal that has received the physical packet determines whether or not the terminal is designated as an OFDMA target terminal (S101, S102). When the information for specifying the own terminal or the group ID of the group to which the own terminal belongs is set in the preamble 1, it is determined that it is designated.

  If the terminal is not designated as an OFDMA target, the terminal identifies at least one resource block among the plurality of resource blocks, and extracts the MAC frame of the identified resource block (S103). Based on the value set in the Duration field of the header of the MAC frame, the NAV is set from the completion of reception of the physical packet (more specifically, reception of the MAC frame in the identified resource block) (S104). When the access right on the medium is acquired after the NAV period elapses, a normal time (DIFS / AIFS [AC] time) is activated as a carrier sense for a certain time before the backoff, and during that time, carrier sense is performed. In addition, carrier sense is performed during the back-off time determined at random.

  On the other hand, when the terminal is designated as the target of OFDMA, the terminal identifies the resource block for the terminal and extracts the MAC frame of the resource block (S105). The MAC frame header is analyzed, and an operation according to the analysis result is performed. If the MAC frame is a data frame (including an aggregation frame), a delivery confirmation response frame (more specifically, a physical packet including a delivery confirmation response) is transmitted by the resource block after SIFS time from completion of reception of the MAC frame. (S106). At this time, a physical packet including an acknowledgment frame is simultaneously transmitted from other terminals designated as OFDMA targets, thereby performing uplink OFDMA transmission.

  In this embodiment, an OFDMA non-target terminal decodes a data field of at least one resource block among a plurality of resource blocks. Here, when the data field of two or more resource blocks can be decoded, that is, when the terminal supports the modulation and coding scheme in preamble 2 of two or more resource blocks, the modulation code satisfying a predetermined condition is satisfied. The resource block of the allocating method may be selected. For example, the most robust modulation and coding resource block may be selected. The most robust modulation and coding scheme may be, for example, a modulation and coding scheme having the lowest transmission rate or a modulation and coding scheme having the lowest coding rate. As another condition, a resource block of a modulation and coding scheme that is below a certain transmission rate or below a certain coding rate may be selected. As a result, the possibility that an error is detected in the FCS of the frame is reduced, and thus the possibility that the NAV can be set is increased.

  Even if the group ID of the group to which the own terminal belongs is set in the preamble 1, as a result of analyzing the MAC frame acquired from the resource block for the own terminal, the MAC frame may not be destined for the own terminal ( RA address is not the address of own terminal). In this case, the NAV may be set based on the value described in the Duration field of the acquired MAC frame.

  In the above-described embodiment, the NAV is set based on the value of the Duration field. However, the length value of the period for setting the NAV is set in the preamble 1 or the plurality of preambles 2 of the physical header or both of them. Also good. At this time, the value of the length of the NAV period may be determined so that the end of the NAV period is the same time for each MAC frame. The terminal extracts the value from one of the preamble 1 and the plurality of preambles 2, and outputs the NAV after the time at the end of the data field or the MAC frame in the corresponding resource block for the period indicated by the value. You only have to set it.

  As described above, according to the present embodiment, when a terminal (non-target terminal) that is not designated as an OFDMA target receives a physical packet group that is OFDMA-transmitted from a base station, at least one of a plurality of resource blocks The MAC frame of the resource block (MAC frame addressed to another terminal) is decoded, and the NAV is set based on the medium reservation time set in the Duration field of the header. That is, the same operation as when a MAC frame addressed to another terminal is normally received is performed. This prevents the occurrence of errors in the PLCP reception process in the non-target terminal and the MAC frame inspection error (FCS error), and during the carrier sense performed when acquiring the access right thereafter, the EIFS time It can be prevented from being activated.

(Second Embodiment)
In the first embodiment, the mode of maintaining the fairness of the access right acquisition opportunity between the non-target terminal of OFDMA and the target terminal and the base station has been mainly shown. A mode is shown in which fairness of access right acquisition opportunities can be maintained for legacy terminals as well as non-target terminals.

  FIG. 11 shows a first example of an operation sequence according to the second embodiment. Description will be made centering on differences from the operation sequence example of FIG. 8 in the first embodiment. As in the first embodiment, the terminals 1 to 6 are OFDMA compatible terminals, the terminals 1 to 4 are OFDMA target terminals, and the terminals 5 and 6 are OFDMA non-target terminals. Terminals 7 and 8 are legacy terminals.

  Similar to the first embodiment, the base station 101 simultaneously transmits physical packets including MAC frames addressed to the terminals 1 to 4 to the terminals 1 to 4 using the resource blocks 1 to 4 in the channel (downlink OFDMA). Send. Terminals 1 to 4 simultaneously transmit physical packets including a delivery confirmation response frame using resource blocks 1 to 4 (uplink OFDMA transmission) after SIFS time from completion of reception of the physical packet, respectively. More specifically, the legacy field and preamble 1 are transmitted in the channel width band, and the preamble 2 and data field (delivery acknowledgment frame) are transmitted in resource blocks. In the operation sequence of FIG. 8 of the first embodiment, the terminals 5 and 6 which are non-target terminals of OFDMA specify at least one resource block and transmit a MAC frame during downlink OFDMA transmission from the base station. Although the NAV is set based on the value extracted and described in the Duration field of the header, such an operation may not be performed in this sequence. Therefore, the terminals 5 and 6 activate the EIFS time when the access right is to be acquired at the end of the downlink OFDMA transmission, at the end of the uplink OFDMA transmission, or after both (see FIG. 11 lower part). (See “EIFS Activation 1” and “EIFS Activation 2”). In a similar case, the legacy terminals 7 and 8 also activate the EIFS time. However, the terminals 5 and 6 may operate similarly to the first embodiment to set the NAV.

  The base station 101 transmits the CF-End frame after SIFS time after the completion of reception of the BA frame transmitted from the terminals 1 to 4 in the uplink OFDMA. The CF-End frame is a frame for announcing the end of CFP (Contents Free Period). That is, the frame permits access to the wireless medium. In the present embodiment, the CF-End frame is transmitted even in a situation where CFP is not started. Usually, a broadcast address is set in the RA field of the CF-End frame. “Bc” in FIG. 11 means that the destination address of the CF-End frame is a broadcast address. However, the destination address of the CF-End frame may be allowed to be a multicast address or a plurality of unicast addresses. In the Duration field of the header of the CF-End frame, 0 is set as the medium reservation time.

  The header of the physical packet including the CF-End frame includes a legacy field and does not include preamble 1 and preamble 2. A physical packet including a CF-End frame is transmitted in one channel width band, and the physical packet is normally received by the terminals 1 to 8. The terminals 1 to 8 are allowed to access the medium after completing the reception of the CF-End frame, and activate the normal DIFS / AIFS [AC] time when trying to acquire the access right (lower part of FIG. 11). (See “Resolving EIFS Activation”).

  The transmission of the CF-End frame is an example, and other frames may be transmitted as a physical packet in the legacy format as long as the frame has a function of permitting the receiving terminal to access the wireless medium. At this time, a value related to the length of the period for instructing suppression of access to the wireless medium may be set in the Duration field or the like in the frame. The length of the period may be set to 0 or a value greater than 0. Even when such a frame is transmitted, since each terminal normally receives a physical packet including the frame, activation of the EIFS time is prevented. Further, by setting the length of the period to 0, each terminal can start an operation for medium access from the time when the end time of the frame has elapsed. When a value greater than 0 is set, the terminals 1 to 8 can start an operation for medium access after the time indicated by the value has elapsed since the completion of reception of the frame.

  In this way, activation of the EIFS time by the non-target terminals 5 and 6 and the legacy terminals 7 and 8 of OFDMA is prevented by the CF-End frame or a frame having a similar function. Therefore, the fairness of the opportunity to acquire the access right can be maintained among all of the terminals 1 to 8 and the base station. In addition, as described above, at the end of the downlink OFDMA transmission, or at the end of the uplink OFDMA transmission, or after both, the terminals 5 to 8 can start the EIFS time. Since other communication continues at the SIFS interval at the time of, it can be said that the access right cannot be acquired in the first place, and that the problem of unfairness does not occur.

  FIG. 12 shows a second example of the operation sequence according to the second embodiment. The description will focus on differences from the operation sequence example of FIG.

  Unlike the operation sequence example of FIG. 11, the lengths of MAC frames (in this case, BA frames) transmitted by uplink OFDMA from terminals 1 to 4 are different. The length of the MAC frame transmitted by the terminals 2 and 4 is shorter than that of the terminals 1 and 3. It is assumed that the physical header length is fixed. This is because even if the size of the MAC frame itself is the same for each terminal, the frame time length (that is, the time required for frame transmission) differs depending on the transmission rate or modulation and coding scheme (MCS) applied. As a method for determining the transmission rate or MCS of the BA frame transmitted uplink from the terminals 1 to 4, the response frame (BA frame) is transmitted according to the transmission rate or MCS of the MAC frame transmitted from the base station to the terminal. A rate or MCS may be determined. For example, a response is made at the maximum transmission rate among the transmission rates supported by the own terminal among the transmission rates below the transmission rate of the MAC frame received from the base station. In such a case, depending on the transmission rate or MCS of the MAC frame transmitted from the base station to the terminals 1 to 4, the response frame transmission rate or MCS may also vary from terminal to terminal, resulting in the MAC frame time. The length also varies from terminal to terminal.

  In such a case, the base station 101 compares the packet lengths of the physical packets received from the terminals 1 to 4 and transmits a CF-End frame after SIFS time from completion of reception of the largest physical packet. When the PHY header length is fixed, the base station 101 compares the frame lengths of the MAC frames included in the physical packets received from the terminals 1 to 4, and the CF-End after SIFS time after the completion of reception of the largest MAC frame. A frame may be transmitted. The terminals 1 to 4 set the packet length of the physical packet or the MAC frame length or both of them in the PHY header (legacy field), and the base station 101 reads and compares the value set therein, so that the physical packet length The longest value or the longest value of the MAC frame length or both of them may be specified.

  In the sequence example of FIG. 12, the downlink OFDMA transmission and the uplink OFDMA transmission as a response thereto are performed only once, and then the CF-End frame is transmitted. However, before the CF-End frame is transmitted, The sequence may be repeated. At this time, the start timing when the base station 101 measures the SIFS time after receiving the physical packet transmitted by the uplink OFDMA is the same as the above when the reception of the physical packet having the longest packet length is completed. That's fine. When the repetition of the sequence ends, the CF-End frame may be transmitted at the timing determined in the same manner as described above.

  In the sequence example of FIG. 12, the value of the Ack policy subfield of the QoS control field in the header of the MAC frame in the physical packet transmitted from the base station by OFDMA is set to a value indicating “Normal Ack”. Thus, the terminals 1 to 4 that have received the data frame (aggregation frame) operate so as to return the BA frame after SIFS time from the reception of the data frame without receiving the BA request (Block Ack Request) frame from the base station. To do. The Ack policy in this case is particularly called “Implicit Block Ack Request”.

  FIG. 13 shows a flowchart of the operation of the base station corresponding to the operation sequence example shown in FIG. The base station determines a plurality of terminals to be subjected to OFDMA, and generates a plurality of MAC frames to be transmitted to the plurality of terminals (S201). The base station stores each of these in the data field and adds a physical header to generate a physical packet (S201). The physical header includes a legacy field, a preamble 1 including information for specifying a plurality of terminals, and a preamble 2 for each terminal including information for decoding a MAC frame.

  The base station transmits the legacy field and preamble 1 of the physical packet in the channel width band, and then transmits the preamble 2 and the data field (MAC frame) by OFDMA (S202).

  The base station receives a physical packet including a delivery confirmation response frame including information regarding the success or failure of reception of the MAC frame from a plurality of terminals after SIFS time from the transmission of the plurality of MAC frames (S203).

  A physical packet including a CF-End frame is transmitted as a frame that does not require transmission of a delivery confirmation response after SIFS time from completion of reception of the physical packet that is completed with the latest reception among the physical packets (S204).

  As described above, in the case of uplink OFDMA transmission, the length of a physical packet including a delivery confirmation response frame or a response, such as when the modulation and coding scheme (MCS) or the transmission rate is different for each destination terminal (Time length) may be different. Therefore, in the sequence example of FIG. 12, the base station specifies the physical packet having the longest packet length among the physical packets for each terminal, and sets the end of the physical packet as the starting point of the SIFS time before the transmission of the CF-End frame. It was.

  Here, as a third example of the operation sequence according to the second embodiment, MCS applied in response to a physical packet transmitted by the base station using OFDMA so that the physical packet length transmitted by each terminal becomes equal. Alternatively, the transmission rate information is notified. For example, the base station sets information indicating the MCS or transmission rate to be applied in response to the preamble 1, preamble 2, or legacy field. Alternatively, a new field may be defined for each resource block in the physical header, and MCS or transmission rate information may be set in the new field. Alternatively, MCS or transmission rate information applied at the time of response may be set in a reserved area of an arbitrary field of the header of each MAC frame or a field newly defined in the header of the MAC frame. Of course, you may specify the information of MCS or the transmission rate applied at the time of a response by methods other than what was described here. If the size of the acknowledgment frame (BA frame or ACK frame, etc.) is fixed, the length of the response frame (BA frame) or the physical packet including it is specified by specifying the same MCS or transmission rate for each terminal. Can be the same. Therefore, the base station does not need to specify a physical packet having the longest packet length from the physical packet received for each terminal.

  Here, instead of explicitly specifying the MAC or transmission rate information used in response to each terminal, the terminal 1 to 4 is a transmission rate that can implicitly specify the transmission rate applied to the transmission of the BA frame. The MAC frame may be transmitted in downlink OFDMA to each terminal. That is, by controlling the transmission rate or MCS of a MAC frame transmitted in downlink OFDMA, the time length of a response frame (BA frame) returned from each terminal can be controlled. As described above, each terminal may determine the transmission rate or MCS of a response frame (BA frame) according to the transmission rate or MCS of the MAC frame addressed to itself by the base station or OFDMA. For example, it responds at the maximum transmission rate among the transmission rates supported by the own terminal among the transmission rates below the transmission rate of the MAC frame transmitted from the base station. In the case of this rule, the base station determines the MAC frame transmission rate or MCS of each terminal that performs downlink OFDMA transmission so that the transmission rate applied to the response frame returned from each terminal is the same.

  As a specific example, a rate defined by the base station as a supported rate (Supported Rate) and notified to each terminal is assumed to be rates 1 to 10. Assume that rates 1, 2, 3,... 10 increase in order, rate 1 is the lowest, and rate 10 is the highest. Terminal 1 has rates 1 to 10 (rate 1, rate 4, rate 7), terminal 2 (rate 1, rate 4, rate 8), terminal 3 (rate 1, rate 4, rate 9), It is assumed that the terminal 4 supports (Rate 1, Rate 4, Rate 8). At this time, the base station identifies one rate that each terminal supports in common, and sets a minimum rate for each terminal that is greater than the identified rate (referred to as a common rate) and greater than the common rate. To be specific. Then, a rate equal to or higher than the common rate and lower than the minimum rate is determined for each terminal, and the determined rate is used as a transmission rate and applied to the MAC frame transmitted to the terminal.

  For example, rate 4 is specified as the common rate. The terminal 1 has a rate 7 as the minimum rate among the rates larger than the rate 4. Therefore, the base station determines a transmission rate from a rate of 4 or more and less than 7 or rates 4 to 6. Similarly, the terminal determines the transmission rate from the rates 4 to 7, the terminal 3 determines the transmission rate from the rates 4 to 8, and the terminal 4 determines the transmission rate from the rates 4 to 7. decide. The transmission rate determined in this way is applied to the MAC frame transmitted to each terminal. Thereby, the transmission rate of the response frame of each terminal can be unified to rate 4. When downlink OFDMA transmission is completed early from the base station, the highest transmission rate may be determined for each terminal.

  Here, in order to make the MAC frame length transmitted to each terminal the same (assuming that the PHY header length is the same), the base station considers the transmission rate determined for each terminal and transmits the MAC frame. May be determined (the size of the data field). As a modified example, the MAC frame length (time length) difference due to the transmission rate being different while the size of the MAC frame transmitted by each terminal is the same is the last padding data for a MAC frame shorter than the longest MAC frame length. You may adjust by transmitting. Thereby, the transmission completion timing to each terminal can be aligned, and the transmission start timing of the response frame (BA frame) can also be aligned.

  Note that the base station may not explicitly define the support rate. In that case, it is assumed that each terminal responds by selecting the transmission rate according to the same rule as described above from the rate set that the base station is required to support according to the physical layer. The transmission rate or MCS to be applied to the MAC frame (aggregation frame) to be performed may be determined.

  It is assumed that the transmission rate or MCS applied to the physical header of the physical packet is fixed. However, when considering the situation where each terminal can apply a different transmission rate or MCS, the following is performed. For example, the transmission rate or MCS information that is commonly applied to the physical header is set in the preamble 1, preamble 2, legacy field of the PHY header of the physical packet transmitted by the base station, or any plurality of these fields. . If the transmission rate or MCS of some of the fields in the physical header is fixed, it may be determined for the remaining fields. For example, when the transmission rate or MCS of preamble 2 existing for each resource block is determined in advance, the transmission rate or MCS for the common preamble (preamble 1 and legacy field) is the same value for each terminal. May be specified.

(Third embodiment)
In the sequence shown in FIG. 11 or FIG. 12 of the second embodiment, since the MAC frame length (more specifically, the total length of the preamble 2 and the MAC frame) for downlink OFDMA transmission is the same, each terminal (terminal 1 to 4) were able to synchronize the transmission start timing of each terminal if a response physical packet was transmitted after SIFS time from the completion of reception of the resource block for the terminal itself. However, when the MAC frame length for downlink OFDMA transmission is different, this method may cause a problem that the response transmission timing is shifted for each terminal. If the transmission timing is shifted, there is a possibility that the common preamble (legacy field and preamble 1) received from each terminal in the channel width band at the base station cannot be decoded normally depending on the shift width. Therefore, in this embodiment, even in such a case, the fairness of the access right acquisition opportunity is maintained while synchronizing the transmission timing of the response physical packet transmitted from each terminal.

  FIG. 14 shows a first example of an operation sequence according to the third embodiment. Description will be made centering on differences from the operation sequence example of FIG. 11 in the second embodiment.

  Similar to the sequence of FIG. 11 in the second embodiment, the base station 101 transmits physical packets including MAC frames addressed to the terminals 1 to 4 using the resource blocks 1 to 4 in the channel (downlink OFDMA transmission). To do. However, the lengths (time lengths) of the MAC frames of the terminals 1 to 4 are not the same. In the example of the figure, the MAC frame lengths transmitted by the terminals 1 and 3 are the same, but the MAC frame length of the terminal 4 is shorter than these, and the MAC frame length of the terminal 2 is further shorter. A value indicating “Block Ack” is set in the Ack policy field of the QoS control field in the header of the MAC frame addressed to the terminals 1 to 4. Thereby, even if the terminals 1 to 4 receive physical packets, they operate so as not to return a delivery confirmation response frame (BA frame) after the SIFS time.

  The base station specifies the transmission completion timing of the longest MAC frame in the physical packet transmitted to the terminals 1 to 4, and after that, after the SIFS time, the BAR (Block Ack Request) frame is transmitted in the channel width band (for example, 20 MHz width band). Send. The physical header of the BAR frame includes a legacy field and does not include preambles 1 and 2. The RA address of the BAR frame is a multicast address of the group to which the terminals 1 to 4 belong. “Mc” in the figure means that the RA address of the BAR frame is a multicast address. It is also conceivable to set a broadcast address instead of a multicast address. The BAR frame can also be normally received by terminals 5 and 6 which are non-target terminals of OFDMA and terminals 7 and 8 which are legacy terminals. Therefore, when the terminals 5 to 8 normally receive the BAR frame, the activation of the EIFS time is temporarily canceled (refer to “EIFS activation cancellation 1” in FIG. 14).

  When the terminals 1 to 4 receive the physical packet including the BAR frame transmitted from the base station in the downlink OFDMA, the RA address is the multicast address of the group to which the terminal belongs, and thus the physical including the BA frame after the SIFS time elapses. Send the packet. The BAR frame is a control frame, and the type and subtype of the MAC header are set to values indicating “control” and “BAR”, respectively. The BA frame transmission and subsequent sequences are the same as in FIG. When the RA address of a BAR frame is set as a broadcast address, a rule may be adopted that a terminal that has received a MAC frame by the previous downlink OFDMA transmission becomes a target of the BAR frame.

  As described above, in the sequence example of FIG. 14, the physical packet including the BAR frame is transmitted after SIFS time after the completion of the transmission of the MAC packet having the longest packet length (long time) among the physical packets transmitted by the base station in downlink OFDMA. To do. Thereby, the transmission timing of the BA frame transmitted by each terminal can be synchronized.

  FIG. 15 shows a flowchart of the operation of the base station corresponding to the first example of the operation sequence according to the third embodiment shown in FIG. The base station determines a plurality of terminals to be subjected to OFDMA (S301), and generates a plurality of MAC frames to be transmitted to the plurality of terminals. The base station stores each of these in the data field and adds a physical header to generate a physical packet (S301). The physical header includes a legacy field, a preamble 1 including information for specifying a plurality of terminals, and a preamble 2 for each terminal including information for decoding a MAC frame.

  The base station transmits the legacy field and preamble 1 of the physical packet in the channel width band, and then transmits the preamble 2 and the data field (MAC frame) by OFDMA (S302).

  The base station generates a BAR frame for requesting transmission of the BA frame as a frame including information on the success or failure of reception of the MAC frame (S303), and the physical packet including the BAR frame is transmitted as the latest data among the data fields. Transmission is performed after SIFS time from the field transmission completion time (S303).

  The base station receives a physical packet including the BA frame from a plurality of terminals by OFDMA after a predetermined time from the transmission of the BAR frame (S304). The base station transmits a physical packet including a CF-End frame after a certain time such as SIFS after receiving the physical packet from a plurality of terminals (S305).

  In the sequence example of FIG. 14, the lengths of the MAC frames transmitted by the base station in the downlink OFDMA are not the same, but these frame lengths are the same as in the sequence example of FIG. 11 in the second embodiment. In some cases, the transmission timing of the BA frame can be synchronized by transmitting the BAR frame. A sequence example in this case is shown in FIG. 16 as a second example of the operation sequence according to the third embodiment. As shown in FIG. 16, the data field length (MAC frame length) of the physical packet transmitted to the terminals 1 to 4 is the same. Since the description of the operation of FIG. 16 is self-evident from the description of FIG. 14 and FIG. Also, the operation of the base station in this case only needs to replace step 304 in FIG. 15 according to the above difference.

  FIG. 17 shows a third example of the operation sequence according to the third embodiment. The description will focus on differences from the operation sequence example of FIG.

  In the sequence examples of FIGS. 14 and 16 described above, a BA frame (more specifically, a physical packet including a BA frame) is transmitted from the OFDMA target terminals (terminals 1 to 4) to the base station by OFDMA. In the sequence example of FIG. 17, the terminals 1 to 4 do not transmit the physical packet including the BA frame by OFDMA, but shift the SIFS time in order and return the physical packet to the base station. A physical packet including a BA frame has a legacy format (no preambles 1 and 2 etc.), and each terminal transmits the physical packet with a channel bandwidth (for example, 20 MHz bandwidth).

  In order to realize this, the base station applies information for specifying the timing for returning the BA frame to the OFDMA target terminal in the BAR frame transmitted after SIFS time from the completion of the downlink OFDMA transmission, and the BA frame transmission. Information specifying the MCS (or transmission rate) to be included. For this purpose, an existing standard BAR frame may be extended. For this purpose, for example, in the body field of the format of the existing BAR frame, for example, after or before or elsewhere in the BAR Information field (a field for setting the sequence number of the first MAC frame requested in the BAR frame, etc.) Even if a field for specifying the transmission timing of the BA frame (referred to as transmission timing field) and a field for specifying the MCS (or transmission rate) applied to the BA frame (referred to as transmission rate field) are added. Good. Alternatively, these fields may be added in the header of the BAR frame. The non-target terminal receives the physical packet including the BAR frame having the legacy format, so that the startup problem of the EIFS time is solved. Thereafter, the non-target terminal can also normally receive the physical packet including the BA frame transmitted in order from each terminal (the physical packet including the BA frame has a legacy format and is normally received), and the EIFS No time startup problems occur. Therefore, after the BA frame is transmitted from the terminal that transmits the BA frame lastly, when the access right to the wireless medium is to be acquired, the fairness of the opportunity to acquire the access right is maintained between the terminals.

  As a method other than adding the transmission timing field and the transmission rate field to the body field of the BAR frame, these fields may be added to the preamble 1 of the physical packet transmitted by the base station in the downlink OFDMA, or for each source block. May be added to the preamble 2. Alternatively, it may be added to the header or body field of each MAC frame in a physical packet to be transmitted by downlink OFDMA. In addition to the method described here, information for specifying the transmission timing and information for specifying the MCS (or) transmission rate may be notified.

  As described above, the transmission timing and transmission rate specified for the terminals 1 to 4 are set so that the interval between the physical packets transmitted from the terminals 1 to 4 is increased by SIFS intervals. For example, as shown in FIG. 17, when physical packets including BA frames are transmitted in the order of terminal 1, terminal 2, terminal 3, and terminal 4, terminal 1 has a timing after SIFS time from completion of transmission of the BAR frame. specify. The terminal 2 is designated with a timing after the SIFS time, the BA frame time length of the terminal 1 (more precisely, the time length of the physical packet including the BA frame), and the SIFS time after the completion of transmission of the BAR frame. (Ie, 2 × SIFS time + BA frame time length of terminal 1). Similarly, the terminal 3 is designated by 3 × SIFS time + BA frame time length of the terminal 1 + BA frame time length of the terminal 2 later. The terminal 4 is designated by 4 × SIFS time + BA frame time length of the terminal 1 + BA frame time length of the terminal 2 + BA frame time length of the terminal 3 later.

  In order to calculate the BA frame time length of the terminals 1 to 3, it is necessary that the transmission rate applied to the transmission of the BA frame by the terminals 1 to 3 is determined (assuming the sizes of the BA frames are the same). For this reason, the base station also determines and designates a transmission rate to be applied to the terminals 1 to 3 and calculates the BA frame time length based on this transmission rate. Note that since there is no terminal that transmits a BA frame after the terminal 4, it is not always necessary to specify a transmission rate for the terminal 4, but here it is assumed that the transmission rate is also specified for the terminal 4.

  When receiving the physical packet including the BAR frame transmitted from the base station, the terminals 1 to 4 extract information for specifying the transmission rate and transmission timing applied to the transmission of the BA frame. A BA frame is generated according to the extracted transmission rate, and a physical packet including the BA frame is generated. Then, the physical packet is transmitted according to the extracted transmission timing. The physical packets transmitted from the terminals 1 to 4 are transmitted with a SIFS time difference, and are received in turn by the base station.

  It is assumed that the transmission rate or MCS applied to the physical header of the physical packet is fixed. However, when considering the situation where each terminal can apply a different transmission rate or MCS, the following is performed. For example, the transmission rate or MCS information that is commonly applied to the physical header is set to preamble 1, preamble 2, legacy field, or any plural number of these in the PHY header of the physical packet transmitted by the base station. If the transmission rate or MCS of some of the fields in the physical header is fixed, it may be determined for the remaining fields. For example, when the transmission rate or MCS of preamble 2 existing for each resource block is determined in advance, the transmission rate or MCS for the common preamble (preamble 1 and legacy field) is the same value for each terminal. May be specified.

  In the example described above, the base station explicitly notifies the transmission rates to be applied to the terminals 1 to 4 to the terminals 1 to 4, but the transmission rates applied to the transmission of the BA frame by the terminals 1 to 4 are implied. The BAR frame may be transmitted at a transmission rate that can be specified. As described in the description of the second embodiment, each terminal transmits a response frame (BA frame) transmission rate or MCS according to the MAC frame transmission rate or MCS addressed to the base station or the OFDMA-transmitted terminal. May be determined. For example, in the rate set supported by the terminal itself, the response is made at the maximum rate among the rates below the transmission rate of the MAC frame transmitted from the base station. Therefore, the base station can specify the transmission rate applied to the response by each terminal from the transmission rate applied to the MAC frame transmitted to each terminal.

  Note that the base station may not define a support rate. In this case, it may be assumed that each terminal responds by selecting a transmission rate according to the same rule as described above from a rate set that the base station must support according to the physical layer.

  In the example of FIG. 17, the order in which each terminal responds with BA frames is the order of terminal 1, terminal 2, terminal 3, and terminal 4. However, the order in which each terminal responds is not limited to this. The base station may determine the response order of each terminal based on a predetermined rule, or may arbitrarily determine the response order. For example, the response order of each terminal may be determined according to a rule that the frequency of the allocated resource block is made to respond to each terminal in the order of low, high, or other criteria. When responding in order from the highest frequency, as in the example of FIG. 17, the order is terminal 1, terminal 2, terminal 3, and terminal 4. When responding in order from the lowest frequency, terminal 4, terminal 3, terminal 2, and terminal 1 are used. It becomes the order of. In addition, the order of responses of the terminals may be determined in the order of association ID (AID) or MAC address in descending order, in ascending order, or based on other criteria. Alternatively, when there is a terminal having a power save mode, the terminal may be preferentially responded.

  FIG. 18 shows a flowchart of the operation of the base station corresponding to the third example of the operation sequence according to the third embodiment shown in FIG. The base station determines a plurality of terminals to be subjected to OFDMA, and determines the transmission timing of a physical packet including a BA frame that is a response frame to a BAR frame transmitted from the base station for each terminal (S401). The transmission timing is determined so that the physical packet including the BA frame is not received at the overlapping timing. As an example, the transmission timing is determined so that the reception interval of physical packets is increased by SIFS time. The base station generates a plurality of MAC frames for transmission to a plurality of terminals. The base station stores each of these in the data field and adds a physical header to generate a physical packet (S402). The physical header includes a legacy field, a preamble 1 including information for specifying a plurality of terminals, and a preamble 2 for each terminal including information for decoding a MAC frame. In addition, at least one of the preamble 1, the preamble 2, and the MAC frame includes information designating transmission timing determined for each terminal.

  The base station transmits the legacy field and preamble 1 of the physical packet in the channel width band, and then transmits the preamble 2 and the data field (MAC frame) by OFDMA (S403).

  The base station generates a BAR frame requesting transmission of the BA frame (S404), and transmits a physical packet including the BAR frame after SIFS time from completion of transmission of the data field whose transmission completion is the slowest among the data fields (same as above). S404).

  After transmitting the BAR frame, the base station receives a physical packet including a BA frame transmitted from each of the plurality of terminals at a designated transmission timing (S405).

  In the above flow, the base station may determine a modulation and coding scheme or a transmission rate applied to the transmission of the BA frame by a plurality of terminals so that the reception of the BAR frame received from each terminal does not overlap. In this case, at least one of the preamble 1, the preamble 2, and the MAC frame includes information specifying the determined modulation and coding scheme or transmission rate. Further, the base station employs a rule for determining a modulation and coding scheme or transmission rate applied to the BA frame according to the modulation and coding scheme or transmission rate applied to the BAR frame by a plurality of terminals. When the rule is recognized, the modulation and coding scheme or transmission rate applied to the BAR frame may be determined so that reception of the BAR frame received from each terminal does not overlap.

(Fourth embodiment)
In the first to third embodiments, an access right on a medium between terminals (that is, between an OFDMA target terminal, an OFDMA non-target terminal, and a base station) is acquired when OFDMA is transmitted from a base station to a plurality of terminals. Showed a mechanism to keep fair opportunities. On the other hand, in the case where multi-user MIMO (Multi-User Multiple Input: MU-MIMO) transmission is performed from a base station to a plurality of terminals, unfairness may occur in the opportunity to acquire access rights on the medium. MU-MIMO transmission from a base station to a plurality of terminals may be particularly referred to as downlink MU-MIMO (downlink MU-MIMO). Also, MU-MIMO transmission from a plurality of terminals to a base station may be referred to as uplink MU-MIMO. In the present embodiment, a terminal that performs at least downlink MU-MIMO communication among downlink MU-MIMO and uplink MU-MIMO is referred to as a MU-MIMO compatible terminal.

  In downlink MU-MIMO transmission, a technique called beam forming is used to form radio waves (beams) having directivities that minimize or reduce mutual interference with a plurality of terminals. A data stream is transmitted to each terminal using the beam formed with each terminal. This enables simultaneous transmission, that is, spatial multiplexing transmission, from the base station to a plurality of terminals in the same frequency band. In the fourth embodiment, it is assumed that a channel width band (for example, a 20 MHz width band) is used as a frequency band for MU-MIMO communication.

  The mechanism for preventing unfairness at the time of access right acquisition shown in the first to third embodiments can be similarly applied to the case where MU-MIMO transmission is performed from a base station to a plurality of terminals. As a result, among the MU-MIMO compatible terminals, the terminal (MU-MIMO target terminal) designated as the target of the current MU-MIMO transmission and the base station were not designated as the target of the current MU-MIMO transmission. Opportunities for acquiring access rights can be made equitable with terminals (non-target terminals of MU-MIMO). In addition, the opportunity for acquiring access rights including legacy terminals can be made fair.

  Hereinafter, the fourth embodiment will be described in detail. The differences from the first to third embodiments will be mainly described, and various derivations such as modifications, expansions, substitutions, additions, and exceptions described in the first to third embodiments are the same in the present embodiment. Applicable to Examples such as modifications, expansions, substitutions, additions, and exceptions that are obvious from the description of the first to third embodiments will not be described here again. In addition, the block diagram of the wireless communication apparatus mounted on each of the base station and the terminal according to the present embodiment is the same as that in FIG. 1, and the difference in the function of each block unit is also changed from OFDMA to MU-MIMO. The description of the block diagram is basically applicable by replacing OFDMA with MU-MIMO and resource blocks with streams.

  With reference to FIG. 19, it will be described that access unfairness may occur between a non-target terminal of MU-MIMO and a MU-MIMO target terminal and a base station. FIG. 19 shows an example of an operation sequence when MU-MIMO communication is performed between the base station (AP) 101 and MU-MIMO target terminals (STA) 1 to 4. However, for the sake of explanation here, although the terminals 1 to 4 and the terminals 5 and 6 have the capability of performing MU-MIMO communication and the capability is effective, there is no problem related to the feature of this embodiment. It is assumed that there is no function to cancel fairness. In the lower part of FIG. 4, an operation example of terminals 5 and 6 which are non-target terminals of MU-MIMO is shown. The horizontal axis represents time, and the vertical axis represents space.

  In this sequence example, the base station 101 and the terminals 1 to 4 perform MU-MIMO communication (both downlink transmission and uplink transmission) using the 20 MHz bandwidth of one channel. Note that the base station 101 may receive a packet including channel response information estimated by each terminal by transmitting a measurement packet or an arbitrary packet from each antenna to each terminal in advance. Thereby, the downlink channel response information between the plurality of antennas of the base station 101 and one or more antennas of each terminal may be acquired. You may acquire propagation path response information by methods other than what was described here. The base station 101 generates a physical packet including a MAC frame addressed to each terminal, and generates one or more streams for each terminal using downlink propagation path response information for each terminal based on the generated physical packet. Then, the stream is transmitted to the terminals 1 to 4.

  In the format example of the physical packet according to the present embodiment, legacy fields (L-STF, L-LTF, L-SIG) are arranged on the top side of the physical header, as in the first to third embodiments. The fields of preamble 1 and preamble 2 according to the present embodiment are arranged behind the field. A data field is placed after the physical header. The preamble 1 and the preamble 2 use the same names as those in the first to third embodiments, but the information to be set in the preamble 1 and the preamble 2 is set to different information depending on the difference between OFDMA and MU-MIMO. In OFDMA communication, resource blocks are allocated to terminals, but in MU-MIMO, resource blocks correspond to streams, and different information is set according to the difference.

  Information that can be commonly understood by MU-MIMO compatible terminals is stored in the preamble 1 of the physical packet transmitted by the base station and transmitted by MU-MIMO. As an example of information set in the preamble 1, there is information for specifying a plurality of terminals (target terminals) that are transmission targets in MU-MIMO. The information for specifying a plurality of terminals may be information for individually identifying these terminals, or a group ID of a group shared by the plurality of terminals may be set.

  Further, as another example of information set in the preamble 1, there may be information for specifying a stream received by each MU-MIMO target terminal. For example, when the terminals 1 to 4 are designated as the target terminals, information for designating the number of streams received by the terminals 1 to 4 may be set. For example, a plurality of fields for designating the number of streams may be provided, and the number of streams of the own terminal may be specified from the number of streams designated in the position field for the own terminal (sometimes referred to as user position). In this case, the position of the field for the own terminal is notified in advance at the time of association or at an arbitrary timing thereafter. In the case of the above example, 1 is set as the number of resource blocks in the fields for terminals 1 to 4, respectively. Also, information on the total number of streams used in MU-MIMO transmission may be set in the preamble 1. This method is also possible when the stream used by each terminal or the number of streams can be identified from the total number of streams.

  The decoding of the stream may be performed using downlink propagation path information. The downlink propagation path information with the base station acquired in advance before the MU-MIMO communication may be used, or the physical header part of the physical packet received this time (for example, the field of the estimation LTF when there is an estimation LTF) ) May be used to acquire propagation path information. In the latter case, when there are a plurality of streams to be transmitted to the terminal, for example, the base station side assigns a code (for example, a bit string of 1 and 0) of a pattern orthogonal to each stream to each symbol in the estimation LTF for each stream. May be transmitted. At this time, the terminal receives in advance the number of streams allocated from the base station according to the above-described field position. The terminal may extract the LTF part signals of a plurality of streams that match the pattern of the terminal from the calculation of the received signal and the pattern, and estimate the propagation path information for each stream. Then, the subsequent field may be acquired for each stream by using the propagation path information for each stream. In addition, information that can be understood by the base station is stored in the preamble 1 transmitted from each terminal to the base station by MU-MIMO.

  Along with the legacy field and preamble 1, transmit in the channel width band (non-MIMO). In FIG. 19, in order to express that the legacy field and the preamble 1 are transmitted in non-MIMO (that is, omni transmission that does not have directivity in a specific direction), each is described as one rectangular block. L-STF, L-LTF, L-SIG, and preamble 1 may be collectively referred to as a common preamble.

  The preamble 2 stores information (such as MCS) necessary for decoding the MAC frame for each corresponding stream. The preamble 2 is transmitted by spatial multiplexing (MU-MIMO transmission). The target terminal of MU-MIMO receives preamble 2 (and subsequent MAC frame) included in the stream for its own terminal, decodes preamble 2 to acquire information such as MCS, and based on MCS The data field is decoded to obtain a MAC frame. In FIG. 19, in order to express that preamble 2 is transmitted in MU-MIMO, preamble 2 is described as a rectangle separated for each stream in the spatial direction. The numbers described in the rectangle representing the preamble 2 represent the number of the destination terminal for convenience.

  A MAC frame is stored in the data field. The MAC frame is transmitted by spatial multiplexing (MU-MIMO transmission). The MAC frame is a data frame, a management frame, or a control frame. Further, the data frame may be not only a single data frame but also an aggregation frame (A-MPDU) in which a plurality of data frames are aggregated. In FIG. 19, in order to express that the MAC frame is transmitted by MU-MIMO, the MAC frame is described in a rectangle separated in the spatial direction for each stream.

  The terminals 1 to 4 receive and decode the legacy field, the preamble 1, the preamble 2 for the own terminal, and the data field in the physical packet transmitted from the base station 101, further decode the stream for the own terminal, and Get the frame. Unlike the downlink OFDMA transmission described in the first to third embodiments, in downlink MU-MIMO transmission, transmission is performed to each terminal by beam forming. It is considered that the stream (preamble 2, data field) is not received.

  The terminals 1 to 4 generate a delivery confirmation response frame including bitmap information indicating whether or not each data frame has been successfully received based on the error check result of each data frame in the aggregation frame. Then, the terminals 1 to 4 receive the physical packet including the BA frame (Block ACK frame), which is a delivery confirmation response frame, after the SIFS time from the completion of reception of the physical packet from the base station (MAC frame reception completion). Send with. When the terminals 1 to 4 transmit two or more streams, the legacy field and preamble 1 of the header of the physical packet including the BA frame are normally transmitted (omni transmission), and the preamble 2 and the MAC frame after the preamble 1 are transmitted. Forms a directional beam based on uplink propagation path response information (uplink propagation path response information between a plurality of antennas of a terminal and a plurality of antennas of a base station) for a base station acquired in advance. Stream transmission.

  Here, the physical packet beam-transmitted from the base station to the terminals 1 to 4 by downlink MU-MIMO may be received by terminals other than the terminals 1 to 4. For example, a beam directed to the terminal 1 may be received because a non-target terminal (here, the terminals 5 and 6) of MU-MIMO is near the terminal 1. At this time, the non-target terminal of MU-MIMO decodes preamble 1 of the header of the physical packet, and as a result, determines that its own terminal is not specified, does not perform subsequent decoding, and detects a reception error. To do. In this case, as described above, the non-target terminal activates the EIFS time by carrier sense at the next channel access (see “EIFS activation 1” in FIG. 19). Similarly, when a physical packet transmitted by MU-MIMO to a base station is received from a plurality of target terminals, a reception error is similarly detected, and the EIFS time is activated by carrier sense at the next channel access (see “ EIFS activation 2 ”).

  A terminal (such as a target terminal or a base station) that does not detect the above-described reception error starts the DIFS / AIFS [AC] time as usual, and thus causes unfairness with non-target terminals.

  Therefore, in order to eliminate the above-mentioned unfairness, the MU-MIMO compatible terminal according to the present embodiment performs the following operation. When the MU-MIMO compatible terminal receives a physical packet transmitted from the base station and transmits MU-MIMO, if the terminal is not designated as a target of MU-MIMO (in the case of a non-target terminal), Obtain a MAC frame in the received stream. In order to decode the MAC frame, the data field may be decoded using information such as MCS set in the preamble 2 arranged in front of the MAC frame. Here, in downlink MU-MIMO transmission, beam transmission is performed to the MU-MIMO target terminals (terminals 1 to 4), so that the non-compliant terminal can receive the physical packet preamble 2 and subsequent terminals. It is considered that this is a case where the user is in a position where the beam addressed to the terminals 1 to 4 can be received.

  Based on the value set in the Duration field of the header, the terminal that has decoded the MAC frame sets the NAV from the completion of reception of the MAC frame. By determining that the RA address of the MAC frame is not the MAC address of the own terminal, the NAV is set. An example of an operation sequence when the non-target terminals (terminals 5 and 6 or both) set the NAV is shown in FIG. 20 as a first example of the operation sequence according to the fourth embodiment. Except for the operation in which the non-target terminal sets the NAV, it is the same as FIG. The non-target terminal receives the physical packet transmitted from the base station 101, and sets the NAV from the end of the MAC frame based on the value of the Duration field of the header of the MAC frame in the stream. The NAV period is set, for example, until the completion of uplink MU-MIMO transmission. After the NAV period, when the non-target terminals 5 and 6 perform carrier sense for acquiring the access right on the medium, the DIFS / AIFS [AC] time is started as usual. Similarly, the base station 101 and the terminals 1 to 4 start the DIFS / AIFS [AC] time when trying to acquire the access right. Therefore, the unfairness of the opportunity to acquire the access right between the non-target terminal of MU-MIMO and the target terminal and the base station is eliminated.

  Note that the terminals 1 to 4 may normally transmit (omni transmission) BA frames in the legacy format (not including the preambles 1 and 2) in order, instead of uplink MU-MIMO transmission. According to this, since the non-target terminal (and the legacy terminal) normally receives the physical packet transmitted in the uplink and sets the NAV, it is possible to prevent activation of the EIFS time. However, compared with the case where the BA frame is transmitted in uplink MU-MIMO, more time is required until all the BA frames are received, and the efficiency is lowered. In addition, in order for each terminal to transmit the BA frame in order, as described in the previous embodiment, control may be performed so that the physical packet including the BA frame is transmitted from each terminal with a shift of SIFS time. desirable.

  Note that the terminals 1 to 4 may normally transmit (omni transmission) BA frames in the legacy format (not including the preambles 1 and 2) in order, instead of uplink MU-MIMO transmission. According to this, since the non-target terminal (and the legacy terminal) normally receives the physical packet transmitted in the uplink and sets the NAV, it is possible to prevent activation of the EIFS time. However, compared with the case where the BA frame is transmitted in uplink MU-MIMO, more time is required until all the BA frames are received, and the efficiency is lowered. In addition, in order for each terminal to transmit the BA frame in order, as described in the previous embodiment, control may be performed so that the physical packet including the BA frame is transmitted from each terminal with a shift of SIFS time. desirable.

  FIG. 21 shows a second example of the operation sequence according to the fourth embodiment. This operation sequence example corresponds to the operation sequence example of FIG. 11 of the second embodiment. Terminals 1 to 6 are MU-MIMO compatible terminals, of which terminals 1 to 4 are MU-MIMO target terminals, and terminals 5 and 6 are MU-MIMO non-target terminals. Terminals 7 and 8 are legacy terminals.

  The base station 101 transmits a physical packet including a MAC frame addressed to the terminals 1 to 4 by spatial multiplexing (downlink MU-MIMO transmission). Terminals 1 to 4 transmit a physical packet including a delivery confirmation response frame by spatial multiplexing (uplink MU-MIMO transmission) after SIFS time from completion of reception of the MAC frame. The terminals 5 to 8 can receive either a physical packet transmitted to the terminals 1 to 4 or a physical packet transmitted from the terminals 1 to 4 to the base station depending on the position where the terminals 5 to 8 exist. When any physical packet is received, for example, the terminals 5 and 6 determine that the preamble 1 does not contain information for identifying the own terminal, and detect a reception error. The terminals 7 and 8 detect a reception error due to a format error or the like such that the preamble 1 cannot be interpreted. When an access right is to be acquired at the end of the downlink MU-MIMO transmission, at the end of the uplink MU-MIMO transmission, or both, the EIFS time is activated (“EIFS activation at the bottom of FIG. 21). 1 ”and“ EIFS activation 2 ”).

  The base station 101 transmits a CF-End frame (omni transmission) after SIFS time after completion of reception of the BA frame transmitted from the terminals 1 to 4 in uplink MU-MIMO. The physical packet including the CF-End frame is normally received by the terminals 1-8. Accordingly, the terminals 1 to 8 are allowed to access the medium after completing the reception of the CF-End frame, and activate the normal DIFS / AIFS [AC] time when trying to acquire the access right (FIG. 21). (See “Resolving EIFS Activation” below).

  Thus, the activation of the EIFS time in the terminals 5 to 8 is prevented by the CF-End frame. Therefore, the fairness of the opportunity to acquire the access right can be maintained among all of the terminals 1 to 8 and the base station. As described above, another frame that does not require transmission of a delivery confirmation response may be transmitted instead of the CF-End frame. The same applies to the following description.

  FIG. 22 shows a third example of the operation sequence according to the fourth embodiment. This operation sequence example corresponds to the operation sequence example of FIG. 12 of the second embodiment.

  The lengths of MAC frames (in this case, BA frames) transmitted from the terminals 1 to 4 in uplink MU-MIMO are different. The length of the MAC frame transmitted by the terminals 2 and 4 is shorter than that of the terminals 1 and 3. The base station 101 transmits a CF-End frame after SIFS time from completion of reception of the physical packet having the longest physical packet length received from the terminals 1 to 4. When the PHY header length is fixed, the CF-End frame may be transmitted after SIFS time after the completion of reception of the MAC frame having the longest MAC frame length.

  As a fourth example of the operation sequence according to the fourth embodiment, the physical packet transmitted by the base station in downlink MU-MIMO is applied at the time of response so that the physical packet length transmitted by each terminal becomes equal. You may notify the information of MCS or a transmission rate. This eliminates the need for the base station to specify the longest physical packet among the physical packets for each terminal. Note that, as described in the previous embodiment, the transmission that the terminals 1 to 4 apply to the transmission of the BA frame, rather than explicitly designating the MAC or transmission rate information to be used for the response to each terminal. You may transmit a MAC frame to each terminal in downlink MU-MIMO with the transmission rate which can specify a rate implicitly.

  FIG. 23 shows a fifth example of the operation sequence according to the fourth embodiment. This operation sequence example corresponds to the operation sequence example of FIG. 14 in the third embodiment.

  The base station 101 transmits a physical packet including a MAC frame addressed to the terminals 1 to 4 by spatial multiplexing (downlink MU-MIMO transmission). However, the MAC frame length transmitted to the terminals 1 to 4 is not the same. The base station transmits (omni transmission) a BAR (Block Ack Request) frame after SIFS time from the time of the longest packet length in the physical packet transmitted to the terminals 1 to 4. The BAR frame is a legacy format. The RA address of the BAR frame is a multicast address of the group to which the terminals 1 to 4 belong. It is also conceivable to set a broadcast address instead of a multicast address. The BAR frame is not only normally received by the terminals 1 to 4 but also normally received by the terminals 5 to 8. Therefore, when the terminals 5 to 8 normally receive the physical packet including the BAR frame, the activation of the EIFS time is canceled (refer to “EIFS activation cancellation 1” in FIG. 14).

  When receiving the BAR frame transmitted from the base station, the terminals 1 to 4 transmit the physical packets each including the BA frame by spatial multiplexing (uplink MU-MIMO transmission) after the SIFS time has elapsed. When the terminals 5 to 8 fail to receive the physical packet, the EIFS time is activated again (“EIFS activation 2” in FIG. 23). However, after this, the CF-End frame is transmitted from the base station, and the terminals 5 to 8 normally receive this, whereby the activation of the EIFS time is canceled. That is, after this, when the non-target terminal, the target terminal, and the base station try to access the wireless medium, the DIFS / AIFC [AC] time is started as usual.

  In the example of the operation sequence of FIG. 23, the packet length of each physical packet transmitted by the base station in the downlink MU-MIMO is not the same. However, when these packet lengths are the same, the BAR frame The transmission timing of the BA frame can be synchronized by transmission. FIG. 24 shows a sequence example in this case as a sixth example of the operation sequence according to the fourth embodiment. This sequence example corresponds to the operation sequence example of FIG. 16 in the third embodiment.

  FIG. 25 shows a seventh example of the operation sequence according to the fourth embodiment. This operation sequence example corresponds to the operation sequence example of FIG. 17 in the third embodiment.

  In this sequence example, the terminals 1 to 4 do not perform uplink MU-MIMO transmission of the BA frame to the BAR frame received from the base station, but sequentially shift the physical packets each including the BA frame by SIFS time. To the base station (omni transmission). A physical packet including a BA frame has a legacy format (no preambles 1, 2 etc.).

  The base station transmits a BAR frame (omni transmission) after SIFS time after completion of downlink MU-MIMO transmission. The BAR frame includes information for specifying the timing for returning the BA frame to the target terminal of MU-MIMO and information for specifying the MCS (or transmission rate) applied to the transmission of the BA frame. Details are as described in the previous embodiment. When the terminals 5 to 8 normally receive the physical packet including the BAR frame (the NAV is set according to the value of the Duration field), the startup problem of the EIFS time is solved. Since then, physical packets including BA frames transmitted in order from each terminal can be normally received, so that an event that causes activation of the EIFS time does not occur. Therefore, after the terminal 4 that transmits the BA frame last transmits the BA frame, each terminal and the base station start the DIFS / AIFS [AC] time as usual when they try to access the wireless medium, Fairness between terminals is maintained.

  The transmission timing and transmission rate specified for the terminals 1 to 4 may be set so that the physical packet intervals transmitted by each of the terminals 1 to 4 are increased by SIFS intervals in the same manner as described in the previous embodiment. The base station does not explicitly notify the terminals 1 to 4 of the transmission rate to be applied to the terminals 1 to 4, but is a transmission rate at which the terminals 1 to 4 can implicitly specify the transmission rate to be applied to the transmission of the BA frame. A BAR frame may be transmitted. Details have been described in the previous embodiment. In the example of FIG. 17, the order in which each terminal responds with BA frames is the order of terminal 1, terminal 2, terminal 3, and terminal 4. However, the order in which each terminal responds is not limited to this.

  In the present embodiment, when a multi-user MIMO (Multi-User Multiple Input: MU-MIMO) transmission is performed from a base station to a plurality of terminals, an opportunity for acquiring an access right on the medium is shown as fair. However, the form similar to the first to fourth embodiments can be implemented for a communication system (referred to as OFDMA & MU-MIMO) combining OFDMA and MU-MIMO. In this communication method, each of a plurality of resource blocks is assigned to a plurality of terminals, and MU-MIMO transmission is performed in units of resource blocks simultaneously with the plurality of resource blocks. Combining the fourth embodiment and any one of the first to third embodiments realizes a form for imparting the right to acquire access rights on the medium even for this communication method. it can.

(Fifth embodiment)
FIG. 26 shows an example of the hardware configuration of a wireless communication device mounted on a terminal (including a base station) according to the fifth embodiment. This hardware configuration is an example, and the hardware configuration can be variously changed. Since the basic operation of the wireless communication apparatus shown in FIG. 26 is the same as that of the wireless communication apparatus described above with reference to FIG. 1, the following description will focus on differences in hardware configuration, and detailed operations will be described. Description is omitted.

  The wireless communication apparatus includes a baseband unit 111, an RF unit 121, and antennas 1 to N (N is an integer of 1 or more).

  The baseband unit 111 includes a control circuit 112, a transmission processing circuit 113, a reception processing circuit 114, DA conversion circuits 115 and 116, and AD conversion circuits 117 and 118. The RF unit 121 and the baseband unit 111 may be configured as a single chip IC (Integrated Circuit) or may be configured as separate chips.

  As an example, the baseband unit 111 is a baseband LSI or a baseband IC. Alternatively, the baseband unit 111 may include an IC 132 and an IC 131 as indicated by a dotted frame shown in the figure. At this time, the IC 132 may include the control circuit 112, the transmission processing circuit 113, and the reception processing circuit 114, and the IC 131 may be divided into the respective ICs so as to include the DA conversion circuits 115 and 116 and the AD conversion circuits 117 and 118. .

  The integrated circuit according to this embodiment includes all or part of the processing of the baseband unit 111, that is, the control circuit 112, the transmission processing circuit 113, the reception processing circuit 114, the DA conversion circuits 115 and 116, and the AD conversion circuits 117 and 118. A processor that performs all or part of the processing may be provided. The integrated circuit according to the present embodiment may correspond to a communication processing device that controls communication.

  The control circuit 112 mainly executes the functions of the MAC processing unit 10 and the MAC / PHY management unit 60. The function of the upper processing unit 90 may be included in the control circuit 112. The transmission processing circuit 113 corresponds to a part that performs processing on the transmission side of the PHY processing unit 50 shown in FIG. That is, the transmission processing circuit 113 performs processing such as addition, encoding, and modulation (may include MIMO modulation) of a PHY header, for example, two types of digital baseband signals (hereinafter, digital I signal and digital Q signal). Is generated. In the case of MIMO transmission, two types of digital baseband signals are generated for each stream. 1 is included in the transmission processing circuit 113, the function of the reception processing unit 40 is included in the reception processing circuit 114, and the functions of the MAC common processing unit 20 and the MAC / PHY management unit 60 are controlled. A configuration included in the circuit 112 is also possible.

  The communication processing apparatus of the present embodiment corresponds to, for example, the control circuit 112, the transmission processing circuit 113, and the reception processing circuit 114. The communication processing apparatus according to the present embodiment includes both a one-chip IC form and a plurality of chip IC forms.

  The DA conversion circuits 115 and 116 correspond to a portion that performs DA conversion of the analog processing unit 70 shown in FIG. The DA conversion circuits 115 and 116 DA convert the signal input from the transmission processing circuit 113. More specifically, the DA conversion circuit 115 converts the digital I signal into an analog I signal, and the DA conversion circuit 116 converts the digital Q signal into an analog Q signal. Note that there may be a case where the signal is transmitted as it is without a quadrature modulation. In this case, only one DA conversion circuit may be provided. Further, in the case where one or a plurality of transmission signals are distributed and transmitted by the number of antennas, a number of DA conversion circuits corresponding to the number of antennas may be provided.

  For example, the RF unit 121 is an RF analog IC or a high-frequency IC. The transmission circuit 122 in the RF unit 121 corresponds to a part that performs processing at the time of transmission after DA conversion in the analog processing unit 70 shown in FIG. The transmission circuit 122 is a transmission filter that extracts a signal in a desired band from a signal of a frame (more specifically, a physical packet including the frame) DA-converted by the DA conversion circuits 115 and 116, and has a constant frequency supplied from the oscillation device. It includes a mixer that uses the signal to upconvert the filtered signal to a radio frequency, and a preamplifier (PA) that amplifies the signal after the upconversion.

  The reception circuit 123 in the RF unit 121 corresponds to a part that performs processing at the time of reception before AD conversion in the analog processing unit 70 illustrated in FIG. 1. The receiving circuit 123 includes an LNA (low noise amplifier) that amplifies the signal received by the antenna, a mixer that downconverts the amplified signal to baseband using a signal of a constant frequency supplied from the oscillation device, A reception filter that extracts a signal in a desired band from the signal after the conversion is included. More specifically, the receiving circuit 123 performs quadrature demodulation on the received signal amplified by a low noise amplification unit (not shown) using a carrier wave that is 90 ° out of phase with each other to obtain I (In− phase) signal and a Q (Quad-phase) signal whose phase is delayed by 90 ° therefrom. These I and Q signals are output from the receiving circuit 123 after the gain is adjusted.

  The control circuit 112 may control the operations of the transmission filter of the transmission circuit 122 and the reception filter of the reception circuit 123. There may be another control unit that controls the transmission circuit 122 and the reception circuit 123, and the same control may be performed by the control circuit 112 issuing an instruction to the control unit.

  The AD conversion circuits 117 and 118 in the baseband unit 111 correspond to a part that performs DA conversion of the analog processing unit 70 shown in FIG. The AD conversion circuits 117 and 118 AD convert the input signal from the reception circuit 123. More specifically, the AD conversion circuit 117 converts the I signal into a digital I signal, and the AD conversion circuit 118 converts the Q signal into a digital Q signal. There may be a case where only one system signal is received without performing quadrature demodulation. In this case, only one AD conversion circuit is required. In the case where a plurality of antennas are provided, the number of AD conversion circuits corresponding to the number of antennas may be provided. The reception processing circuit 114 corresponds to a part that performs processing on the reception signal side of the PHY processing unit 50 shown in FIG. That is, the reception processing circuit 114 performs demodulation processing of the signal after AD conversion (which may include MIMO demodulation), processing for removing the preamble and the PHY header, and passes the processed frame to the control circuit 112.

  Note that a switch for switching the antennas 1 to N to either the transmission circuit 122 or the reception circuit 123 may be arranged in the RF unit. By controlling the switch, the antennas 1 to N may be connected to the transmission circuit 122 during transmission, and the antennas 1 to N may be connected to the reception circuit 123 during reception.

  In FIG. 26, the DA conversion circuits 115 and 116 and the AD conversion circuits 117 and 118 are disposed on the baseband unit 111 side, but may be configured to be disposed on the RF unit 121 side.

  Note that a wireless communication unit may be formed by the transmission circuit 122 and the reception circuit 123. The transmission circuit 122 and the reception circuit 123 may further include DA conversion circuits 115 and 116 and AD conversion circuits 117 and 118 to form a wireless communication unit. Further, in addition to these, a wireless communication unit may be formed including the PHY processing portions of the transmission processing circuit 113 and the reception processing circuit 114.

(Sixth embodiment)
FIGS. 27A and 27B are perspective views of a wireless communication terminal according to the sixth embodiment, respectively. The wireless communication terminal in FIG. 27A is a notebook PC 301, and the wireless communication terminal in FIG. 27B is a mobile terminal 321. Each corresponds to one form of a terminal (including a base station). The notebook PC 301 and the mobile terminal 321 are equipped with wireless communication devices 305 and 315, respectively. As the wireless communication devices 305 and 315, the wireless communication devices mounted on the terminals (including base stations) described so far can be used. A wireless communication terminal equipped with a wireless communication device is not limited to a notebook PC or a mobile terminal. For example, TV, digital camera, wearable device, tablet, smartphone, game device, network storage device, monitor, digital audio player, web camera, video camera, project, navigation system, external adapter, internal adapter, set top box, gateway, It can also be installed in printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, and the like.

  In addition, the wireless communication device mounted on the terminal (including the base station) can be mounted on the memory card. FIG. 28 shows an example in which the wireless communication device is mounted on a memory card. The memory card 331 includes a wireless communication device 355 and a memory card main body 332. The memory card 331 uses a wireless communication device 335 for wireless communication with an external device (such as a wireless communication terminal and / or base station). In FIG. 28, description of other elements (for example, a memory) in the memory card 331 is omitted.

(Seventh embodiment)
In the seventh embodiment, in addition to the configuration of the wireless communication apparatus according to any one of the first to sixth embodiments, a bus, a processor unit, and an external interface unit are provided. The processor unit and the external interface unit are connected to the buffer via the bus. Firmware operates in the processor unit. As described above, by configuring the firmware to be included in the wireless communication device, it is possible to easily change the function of the wireless communication device by rewriting the firmware. The processor unit on which the firmware operates may be a processor that performs processing of the communication processing device or the control unit according to the present embodiment, or may be another processor that performs processing related to function expansion or change of the processing. Also good. The base station and / or the wireless communication terminal according to the present embodiment may include a processor unit on which firmware operates. Alternatively, the processor unit may be provided in an integrated circuit in a wireless communication device mounted on a base station or an integrated circuit in a wireless communication device mounted on a wireless communication terminal.

(Eighth embodiment)
In the eighth embodiment, in addition to the configuration of the wireless communication apparatus according to any one of the first to sixth embodiments, a clock generation unit is provided. The clock generation unit generates a clock and outputs the clock from the output terminal to the outside of the wireless communication device. Thus, the host side and the wireless communication apparatus side can be operated in synchronization by outputting the clock generated inside the wireless communication apparatus to the outside and operating the host side with the clock output to the outside. It becomes possible.

(Ninth embodiment)
In the ninth embodiment, in addition to the configuration of the wireless communication device according to any one of the first to sixth embodiments, a power supply unit, a power supply control unit, and a wireless power supply unit are included. The power supply control unit is connected to the power supply unit and the wireless power supply unit, and performs control to select a power supply to be supplied to the wireless communication device. As described above, by providing the wireless communication apparatus with the power supply, it is possible to perform a low power consumption operation by controlling the power supply.

(Tenth embodiment)
The tenth embodiment includes a SIM card in addition to the configuration of the wireless communication apparatus according to the ninth embodiment. The SIM card is connected to, for example, the MAC processing unit 10, the MAC / PHY management unit 60, or the control unit 112 in the wireless communication apparatus. As described above, by adopting a configuration in which the SIM card is provided in the wireless communication device, authentication processing can be easily performed.

(Eleventh embodiment)
In the eleventh embodiment, in addition to the configuration of the wireless communication apparatus according to the ninth embodiment, a moving image compression / decompression unit is included. The moving image compression / decompression unit is connected to the bus. As described above, by providing the wireless communication device with the moving image compression / decompression unit, it is possible to easily transmit the compressed moving image and expand the received compressed moving image.

(Twelfth embodiment)
In the twelfth embodiment, in addition to the configuration of the wireless communication apparatus according to any one of the first to sixth embodiments, an LED unit is included. The LED unit is connected to, for example, at least one of the MAC processing unit 10, the MAC / PHY management unit 60, the transmission processing circuit 113, the reception processing circuit 114, and the control unit 112. As described above, by providing the wireless communication device with the LED unit, it is possible to easily notify the user of the operation state of the wireless communication device.

(13th Embodiment)
In the thirteenth embodiment, in addition to the configuration of the wireless communication device according to any one of the first to sixth embodiments, a vibrator unit is included. The vibrator unit is connected to, for example, at least one of the MAC processing unit 10, the MAC / PHY management unit 60, the transmission processing circuit 113, the reception processing circuit 114, and the control unit 112. As described above, by providing the radio communication device with the vibrator unit, it is possible to easily notify the user of the operation state of the radio communication device.

(Fourteenth embodiment)
In the fourteenth embodiment, in addition to the configuration of the wireless communication device according to any one of the first to sixth embodiments (a wireless communication device of a base station or a wireless communication device of a wireless communication terminal, or both), Includes a display. The display may be connected to the MAC processing unit of the wireless communication device via a bus (not shown). Thus, it is possible to easily notify the user of the operation state of the wireless communication device by providing the display and displaying the operation state of the wireless communication device on the display.

(Fifteenth embodiment)
In this embodiment, [1] a frame type in a wireless communication system, [2] a method of disconnecting connections between wireless communication apparatuses, [3] an access method of a wireless LAN system, and [4] a frame interval of the wireless LAN will be described.
[1] Frame type in communication system Generally, as described above, the frames handled on the radio access protocol in the radio communication system are roughly divided into three: data frame, management frame, and control frame. Divided into types. These types are usually indicated by a header portion provided in common between frames. As a display method of the frame type, three types may be distinguished by one field, or may be distinguished by a combination of two fields. In the IEEE 802.11 standard, the frame type is identified by two fields, Type and Subtype, in the Frame Control field in the frame header portion of the MAC frame. A data frame, a management frame, or a control frame is roughly classified in the Type field, and a detailed type in the roughly classified frame, for example, a Beacon frame in the management frame is identified in the Subtype field.

  The management frame is a frame used for managing a physical communication link with another wireless communication apparatus. For example, there are a frame used for setting communication with another wireless communication device, a frame for releasing a communication link (that is, disconnecting), and a frame related to a power saving operation in the wireless communication device. .

  The data frame is a frame for transmitting data generated inside the wireless communication device to the other wireless communication device after establishing a physical communication link with the other wireless communication device. Data is generated in an upper layer of the present embodiment, for example, generated by a user operation.

  The control frame is a frame used for control when a data frame is transmitted / received (exchanged) to / from another wireless communication apparatus. When the wireless communication apparatus receives a data frame or a management frame, the response frame transmitted for confirmation of delivery belongs to the control frame. The response frame is, for example, an ACK frame or a BlockACK frame. RTS frames and CTS frames are also control frames.

  These three types of frames are sent out via the antenna as physical packets after undergoing processing as required in the physical layer. Note that in the IEEE 802.11 standard (including the above-mentioned extended standard such as IEEE Std 802.11ac-2013), there is an association process as one of the procedures for establishing a connection, and an Association Request frame used in the process. Since the Association Response frame is a management frame, and the Association Request frame and the Association Response frame are unicast management frames, the receiving wireless communication terminal is requested to transmit an ACK frame that is a response frame. Is a control frame.

[2] Connection disconnection method between wireless communication devices There are an explicit method and an implicit method for disconnection (release) of a connection. As an explicit method, one of the wireless communication apparatuses that have established a connection transmits a frame for disconnection. In the IEEE 802.11 standard, a deauthentication frame is classified as a management frame. Normally, when a wireless communication device that transmits a frame for disconnecting a connection transmits the frame, the wireless communication device that receives a frame for disconnecting a connection disconnects the connection when the frame is received. judge. After that, if it is a non-base station wireless communication terminal, it returns to the initial state in the communication phase, for example, the state of searching for a connected BSS. When the connection between a wireless communication base station and a certain wireless communication terminal is disconnected, for example, if the wireless communication base station has a connection management table for managing the wireless communication terminal that subscribes to its own BSS, the connection management Delete information related to the wireless communication terminal from the table. For example, when assigning an AID to a wireless communication terminal that joins the BSS in the association process at the stage where the wireless communication base station has permitted the connection, the holding information associated with the AID of the wireless communication terminal that has disconnected the connection. May be deleted, and the AID may be released and assigned to another newly joined wireless communication terminal.

  On the other hand, as an implicit method, a frame transmission (transmission of a data frame and a management frame, or transmission of a response frame to a frame transmitted by the device itself) is detected from a wireless communication device of a connection partner with which a connection has been established. If not, it is determined whether the connection is disconnected. There is such a method in the situation where it is determined that the connection is disconnected as described above, such that the communication distance is away from the connection-destination wireless communication device, and the wireless signal cannot be received or decoded. This is because a wireless link cannot be secured. That is, it is impossible to expect reception of a frame for disconnecting the connection.

  As a specific example of determining the disconnection by an implicit method, a timer is used. For example, when transmitting a data frame requesting a delivery confirmation response frame, a first timer (for example, a retransmission timer for a data frame) that limits a retransmission period of the frame is started, and until the first timer expires (that is, If a delivery confirmation response frame is not received (until the desired retransmission period elapses), retransmission is performed. The first timer is stopped when a delivery confirmation response frame to the frame is received.

  On the other hand, when the first timer expires without receiving the delivery confirmation response frame, for example, it is confirmed whether the other party's wireless communication device still exists (within the communication range) (in other words, the wireless link can be secured). And a second timer for limiting the retransmission period of the frame (for example, a retransmission timer for the management frame) is started at the same time. Similar to the first timer, the second timer also performs retransmission if it does not receive an acknowledgment frame for the frame until the second timer expires, and determines that the connection has been disconnected when the second timer expires. . When it is determined that the connection has been disconnected, a frame for disconnecting the connection may be transmitted.

    Alternatively, when a frame is received from the connection partner wireless communication device, the third timer is started. Whenever a new frame is received from the connection partner wireless communication device, the third timer is stopped and started again from the initial value. When the third timer expires, a management frame is transmitted to confirm whether the other party's wireless communication device still exists (within the communication range) (in other words, whether the wireless link has been secured) as described above. At the same time, a second timer (for example, a retransmission timer for management frames) that limits the retransmission period of the frame is started. Also in this case, if the acknowledgment response frame to the frame is not received until the second timer expires, retransmission is performed, and if the second timer expires, it is determined that the connection has been disconnected. In this case as well, a frame for disconnecting the connection may be transmitted when it is determined that the connection has been disconnected. The latter management frame for confirming whether the wireless communication apparatus of the connection partner still exists may be different from the management frame in the former case. In the latter case, the timer for limiting the retransmission of the management frame is the same as that in the former case as the second timer, but a different timer may be used.

[3] Access method of wireless LAN system For example, there is a wireless LAN system that is assumed to communicate or compete with a plurality of wireless communication devices. The IEEE 802.11 wireless LAN uses CSMA / CA (Carrier Sense Multiple Access with Carrier Avoidance) as a basic access method. In the method of grasping the transmission of a certain wireless communication device and performing transmission after a fixed time from the end of the transmission, the transmission is performed simultaneously by a plurality of wireless communication devices grasping the transmission of the wireless communication device, and as a result The radio signal collides and frame transmission fails. By grasping the transmission of a certain wireless communication device and waiting for a random time from the end of the transmission, the transmissions by a plurality of wireless communication devices that grasp the transmission of the wireless communication device are stochastically dispersed. Therefore, if there is one wireless communication device that has drawn the earliest time in the random time, the frame transmission of the wireless communication device is successful, and frame collision can be prevented. Since acquisition of transmission rights is fair among a plurality of wireless communication devices based on a random value, the method employing Carrier Aviation is a method suitable for sharing a wireless medium between a plurality of wireless communication devices. be able to.

[4] Wireless LAN Frame Interval The IEEE 802.11 wireless LAN frame interval will be described. The frame interval used in the IEEE 802.11 wireless LAN is as follows: distributed coordination function inter frame space (DIFS), arbitration inter frame space (AIFS), point coordination function intra interface space interface (IFS). There are six types, reduced interface space (RIFS).

  In the IEEE802.11 wireless LAN, the frame interval is defined as a continuous period to be opened after confirming carrier sense idle before transmission, and a strict period from the previous frame is not discussed. Therefore, in the description of the IEEE802.11 wireless LAN system here, the definition follows. In the IEEE802.11 wireless LAN, the waiting time for random access based on CSMA / CA is the sum of a fixed time and a random time, and it can be said that such a definition is used to clarify the fixed time.

  DIFS and AIFS are frame intervals used when attempting to start frame exchange during a contention period competing with other wireless communication devices based on CSMA / CA. The DIFS is used when priority according to the traffic type (Traffic Identifier: TID) is provided when there is no distinction of the priority according to the traffic type.

  Since operations related to DIFS and AIFS are similar, the following description will be mainly given using AIFS. In the IEEE802.11 wireless LAN, access control including the start of frame exchange is performed in the MAC layer. Further, when QoS (Quality of Service) is supported when data is passed from an upper layer, the traffic type is notified together with the data, and the data is classified according to the priority at the time of access based on the traffic type. This class at the time of access is called an access category (AC). Therefore, an AIFS value is provided for each access category.

  The PIFS is a frame interval for enabling access with priority over other competing wireless communication apparatuses, and has a shorter period than any value of DIFS and AIFS. SIFS is a frame interval that can be used when transmitting a control frame of a response system or when frame exchange is continued in a burst after acquiring an access right once. The EIFS is a frame interval that is activated when frame reception fails (it is determined that the received frame is an error).

    The RIFS is a frame interval that can be used when a plurality of frames are continuously transmitted to the same wireless communication device in bursts after acquiring the access right once. Do not request a response frame.

  Here, FIG. 29 shows an example of a frame exchange in a contention period based on random access in the IEEE 802.11 wireless LAN.

  It is assumed that when a transmission request for a data frame (W_DATA1) is generated in a certain wireless communication apparatus, the medium is recognized as busy as a result of carrier sense. In this case, a fixed time AIFS is released from the point when the carrier sense becomes idle, and then a data frame W_DATA1 is transmitted to the communication partner when a random time (random backoff) is available. As a result of carrier sense, when the medium is not busy, that is, it is recognized that the medium is idle, a fixed time AIFS is released from the time when carrier sense is started, and the data frame W_DATA1 is transferred to the communication partner. Send to.

  The random time is obtained by multiplying a pseudo-random integer derived from a uniform distribution between a contention window (Content Window: CW) given by an integer from 0 to a slot time. Here, CW multiplied by slot time is referred to as CW time width. The initial value of CW is given by CWmin, and every time retransmission is performed, the value of CW is increased until it reaches CWmax. Both CWmin and CWmax have values for each access category, similar to AIFS. In the wireless communication apparatus that is the transmission destination of W_DATA1, if the data frame is successfully received and the data frame is a frame that requests transmission of a response frame, the occupation of the physical packet that includes the data frame on the wireless medium is completed. A response frame (W_ACK1) is transmitted after SIFS time from the time. The wireless communication apparatus that has transmitted W_DATA1 transmits the next frame (for example, W_DATA2) after SIFS time from the end of occupation of the physical packet containing W_ACK1 on the wireless medium if it is within the transmission burst time limit when W_ACK1 is received. can do.

  AIFS, DIFS, PIFS, and EIFS are functions of SIFS and slot time. SIFS and slot time are defined for each physical layer. Also, parameters such as AIFS, CWmin, and CWmax that can be set for each access category can be set for each communication group (Basic Service Set (BSS) in the IEEE802.11 wireless LAN), but default values are set. .

  For example, in the 802.11ac standard formulation, the SIFS is 16 μs and the slot time is 9 μs. Accordingly, the PIFS is 25 μs, the DIFS is 34 μs, and the frame interval of the access category BACKGROUND (AC_BK) in AIFS is 79 μs by default. The frame interval of BEST EFFORT (AC_BE) has a default value of 43 μs, the frame interval of VIDEO (AC_VI) and VOICE (AC_VO) has a default value of 34 μs, and the default values of CWmin and CWmax are 31 and 1023 for AC_BK and AC_BE, respectively. , AC_VI is 15 and 31, and AC_VO is 7 and 15. Note that the EIFS is basically the sum of the time lengths of response frames in the case of transmission at SIFS and DIFS at the slowest required physical rate. Note that in a wireless communication apparatus capable of efficiently taking EIFS, the occupation time length of a physical packet carrying a response frame to the physical packet that activated EIFS is estimated, and the sum of SIFS, DIFS, and the estimated time may be used. it can.

  The terms used in this embodiment should be interpreted widely. For example, the term “processor” may include general purpose processors, central processing units (CPUs), microprocessors, digital signal processors (DSPs), controllers, microcontrollers, state machines, and the like. In some situations, a “processor” may refer to an application specific integrated circuit, a field programmable gate array (FPGA), a programmable logic circuit (PLD), or the like. “Processor” may refer to a combination of processing devices such as a plurality of microprocessors, a combination of a DSP and a microprocessor, and one or more microprocessors that cooperate with a DSP core.

  As another example, the term “memory” may encompass any electronic component capable of storing electronic information. “Memory” means random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), non-volatile It may refer to random access memory (NVRAM), flash memory, magnetic or optical data storage, which can be read by the processor. If the processor reads and / or writes information to the memory, the memory can be said to be in electrical communication with the processor. The memory may be integrated into the processor, which again can be said to be in electrical communication with the processor.

  Note that the frame described in each embodiment may refer to not only a frame called in the IEEE 802.11 standard, but also a packet called a packet such as a Null Data Packet.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

10: MAC processing unit 20: MAC common processing unit 30: transmission processing unit 40: reception processing unit 50: PHY processing unit 60: MAC / PHY management unit 70: analog processing unit (analog processing units 1 to N)
80: Antenna (antenna 1 to N)
90: Host processing unit 111: Baseband unit 121: RF unit 122: Transmission circuit 123: Reception circuit 112: Control circuit 113: Transmission processing circuit 114: Reception processing circuits 115, 116, 215, 216: DA conversion circuits 117, 118 217, 218: AD conversion circuit 301: Notebook PC
305, 315, 355: Wireless communication device 321: Mobile terminal 331: Memory card 332: Memory card body

Claims (17)

When the first information for identifying the device is not set in the first field of the packet including the first field and at least one of the multiplexed second fields, the plurality of second fields Extract a frame from one of the fields,
An integrated circuit for wireless communication, comprising: a baseband integrated circuit that controls to suppress access to a wireless medium during a period indicated by a value set in the frame. The integrated circuit for wireless communication according to claim 1, wherein the multiplexing is at least one of frequency multiplexing and spatial multiplexing. The first field is a field common to a plurality of wireless communication terminals,
The plurality of second fields are individual fields of the plurality of wireless communication terminals,
The integrated circuit for wireless communication according to claim 1 or 2. 4. The integrated circuit for wireless communication according to claim 1, wherein the first field includes second information for decoding each of the plurality of second fields. 5. The plurality of second fields are transmitted by OFDMA (Orthogonal Frequency Division Multiple Access),
The second information is:
Information about error correction code schemes,
The integrated circuit for wireless communication according to claim 4, comprising at least one of information for specifying a plurality of resource blocks used for transmission of the plurality of second fields. The information for identifying the plurality of resource blocks includes at least one of information on the number of the plurality of resource blocks, information on a subcarrier interval between the plurality of resource blocks, and individual identifiers of the plurality of resource blocks. The integrated circuit for wireless communication according to claim 5, comprising one. The plurality of second fields are transmitted by multi-user MIMO (Multiple Input Multiple Output),
The second information is:
Information about error correction code schemes,
The integrated circuit for wireless communication according to claim 4, comprising at least one of information on the number of streams. Each of the plurality of second fields includes a third field and a fourth field;
The baseband integrated circuit acquires third information from the third field of one of the plurality of second fields when the first information is not set in the first field, and the third field The integrated circuit for wireless communication according to claim 1, wherein the frame is extracted from the fourth field by decoding the fourth field based on information. The third information includes information on a modulation and coding scheme applied to the frame,
The baseband integrated circuit identifies a third field in which a modulation and coding scheme that can be supported by the device is set, and the fourth band based on the modulation and coding scheme set in the identified third field. The integrated circuit for wireless communication according to claim 8, wherein the frame is obtained by decoding a field. The baseband integrated circuit, when there are a plurality of the third fields in which a modulation and coding scheme that can be supported by the device itself is present, is a modulation and coding scheme in which a coding rate or a transmission rate satisfies a predetermined condition 10. The wireless communication according to claim 9, wherein the third field in which the frame is set is identified, and the frame is obtained by decoding the fourth field based on a modulation and coding scheme set in the identified third field. Integrated circuit. When the first information specifying the device is not set in the first field and the parameter value is the first value, the baseband integrated circuit is one of the plurality of second fields. The wireless communication according to any one of Claims 1 to 9, wherein a frame is obtained by decoding the frame, and when the parameter value is a second value, none of the plurality of second fields is decoded. Integrated circuit. Each of the plurality of second fields includes a third field in which the frame is set and a fourth field in which a value is set.
Instead of extracting the value from the frame, the baseband integrated circuit extracts the value from one of the fourth fields,
The integrated circuit for wireless communication according to claim 1, wherein the baseband integrated circuit controls to suppress access to the wireless medium during a period indicated by a value extracted by the first processing unit. In the baseband integrated circuit, a value for each frame is set in the first field,
Instead of extracting the value from the frame, the baseband integrated circuit extracts one of the values for each frame from the first field;
The integrated circuit for wireless communication according to claim 1, wherein the baseband integrated circuit controls to suppress access to the wireless medium during a period indicated by a value extracted by the first processing unit. The integrated circuit for wireless communication according to any one of claims 1 to 13, wherein the baseband integrated circuit controls communication according to an IEEE 802.11 standard. The integrated circuit for wireless communication according to claim 5 or 6, wherein the resource block includes one or a plurality of subcarriers. Further comprising an RF integrated circuit;
The baseband integrated circuit receives the packet via the RF integrated circuit;
The RF integrated circuit downconverts the packet to a baseband frequency;
The wireless communication integrated circuit according to any one of claims 1 to 15, wherein the baseband integrated circuit AD converts the down-converted packet. The wireless communication integrated circuit according to claim 16, wherein the baseband integrated circuit and the RF integrated circuit are configured by one integrated circuit.

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