JP6884815B2 - Wireless communication device and wireless communication method - Google Patents

Description

Embodiments of the present invention relate to wireless communication devices and wireless communication methods.

In a wireless LAN network compliant with the next-generation wireless LAN standard IEEE 802.11ax, a large number of base stations (or access points (APs)) are arranged, that is, a large number of basic service units (Basic Service Set: BSS) are arranged. It is assumed that there is a large number of terminals (or stations (STA)) in a high-density environment. Multi-user transmission technology such as multi-user MIMO (Multi-user Multiple-Input Multi-Automat: MU-MIMO) or orthogonal frequency division multiple access (orthogonal frequency division access: OFDMA) to multiple terminals at the same time. It becomes possible to transmit a link (Uplink: UL). This is called uplink multi-user (UL-MU) transmission.

The terminal accesses the wireless medium based on the conventional enhanced distributed channel access (EDCA). In EDCA, parameters corresponding to each access category (AC) are prepared. Then, the back-off counter for each AC is reset when the transmission of the corresponding AC is successful, and the countdown is suspended for busy when the channel becomes busy while waiting for transmission. In IEEE 802.11ax, a plurality of terminals are allowed to access the uplink channel at the same time by using the trigger frame transmitted by the base station. During the UL-MU transmission period, it is considered to be treated as a "channel busy" case, but the frame backed off for transmission may be transmitted by the UL-MU. In such a scenario, it is necessary to consider how to handle the backoff counter. Further, the terminal capable of UL-MU transmission can also use the normal uplink single user (ULlink Single User: UL-SU) transmission in which the terminal itself acquires the access right to the wireless medium and transmits without uplink multiplexing. There is a problem of fairness that you will have more transmission opportunities.

There is a proposal to use two parameters as a method of handling EDCA parameters in UL-MU. In this proposal, the contention parameter of the terminal using UL-MU-MIMO is set to a value different from that of the terminal not using UL-MU-MIMO. It also proposes that the base station show a pruning value, and whether multiple terminals vie for channel access as a wildcard resource based on the pruning value. To determine.

Another method is to use a different EDCA parameter set on the terminal to which the resource unit (RU) is assigned in the trigger frame. By increasing the EDCA parameters CWmin and AIFSN as compared to the case where UL-MU transmission is not performed, the base station limits single user (SU) transmission using EDCA at these terminals. As a result, the contention can be reduced. However, the issue of fairness between terminals that can and cannot perform UL-MU transmission remains unsolved.

IEEE802.11_16 / 684r2 IEEE Std 802.11ac (TM) -2013 IEEE Std 802.11 (TM) -2012

Embodiments of the present invention allow the wireless medium to be used appropriately in an environment capable of uplink multi-user transmission.

The wireless communication device according to the embodiment of the present invention sets an upper limit of the time during which the wireless medium can be occupied according to the history of uplink multi-user transmission or the enabled or disabled state of the capability of uplink multi-user transmission. A control unit for changing the value of one parameter is provided.

The functional block diagram of the wireless communication apparatus which concerns on embodiment of this invention. The figure which shows the wireless communication system which includes a base station and a plurality of terminals. The figure which shows the basic format example of a MAC frame. The figure which shows the format example of an information element. The figure which shows the sequence example which concerns on the 1st operation example of embodiment of this invention. The figure which shows the format example of a physical packet. The figure which shows the example of the value of a plurality of EDCA parameters for each access category. The figure for demonstrating the change of the value of the back-off counter in a plurality of terminals. The figure which shows the flowchart of the operation example of the terminal which concerns on 1st operation example of embodiment of this invention. The figure which shows the sequence example which concerns on the 2nd operation example of embodiment of this invention. The explanatory view of the effect of the 2nd operation example. The figure which shows the flowchart of an example of the operation of the terminal which concerns on the 2nd operation example of embodiment of this invention. The figure which shows the flowchart of an example of the operation of the terminal which concerns on the 3rd operation example of the Embodiment of this invention. The figure which shows the sequence example which concerns on the 3rd operation example of embodiment of this invention. The figure which shows the other sequence example which concerns on the 3rd operation example of the Embodiment of this invention. The figure which shows still another sequence example which concerns on the 3rd operation example of embodiment of this invention. The figure which shows the format example of a trigger frame. Explanatory drawing of Multi-STA BA frame. The figure for demonstrating the concept of UL-MU-MIMO. The figure for demonstrating the preamble used in UL-MU-MIMO. The figure for demonstrating the allocation of a resource unit. The figure for demonstrating the form of a resource unit. The functional block diagram of the base station or the terminal which concerns on 2nd Embodiment. The figure which shows the whole configuration example of the terminal or the base station which concerns on 3rd Embodiment. The figure which shows the hardware configuration example of the wireless LAN module mounted on the terminal or the base station which concerns on 3rd Embodiment. The perspective view of the wireless communication terminal which concerns on embodiment of this invention. The figure which shows the memory card which concerns on embodiment of this invention. The figure which shows an example of frame exchange of a contention period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Specification framework documents for IEEE Std 802.11 (TM) -2012 and IEEE Std 802.11ac (TM) -2013, which are known as wireless LAN standards, and IEEE Std 802.11ax, the next generation wireless LAN standard. The IEEE 802.11-15 / 0132r17, uploaded on May 25, 2016, which is a Specialization Framework Document, shall be incorporated herein by reference in its entirety.

(First Embodiment)
FIG. 1 shows a functional block diagram of the wireless communication device according to the first embodiment. This wireless communication device can be applied to a wireless communication base station (hereinafter, base station or access point) or a wireless communication terminal (hereinafter, terminal) that communicates with the base station. A base station is a form of a terminal because it basically has the same communication function as a terminal except that it mainly has a relay function. The operation of the functional block is basically the same for both, but there are some differences between the terminals of the base station and the terminals of the non-base station. In the following description, the term terminal may refer to a base station unless it is necessary to distinguish between the two.

As shown in FIG. 1, the wireless communication devices mounted on the terminals (terminals of non-base stations and base stations) include a higher-level processing unit 90, a MAC processing unit 10, a PHY (Physical) processing unit 50, and a MAC /. It includes a PHY management unit 60, an analog processing unit 70 (analog processing units 1 to N), and an antenna 80 (antennas 1 to N). N is an integer greater than or equal to 1. In the figure, N analog processing units and N antennas are connected in pairs, but the configuration is not necessarily limited to this. For example, the number of analog processing units is 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 a form of a control unit that controls communication with other terminals (including a base station). The analog processing unit 70 corresponds to, for example, a form of a wireless communication unit (transmitting unit and receiving unit) that transmits and receives signals via the antenna 80. The function of the control unit may be performed by software (program) operating on a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware. The software may be stored in a memory such as a ROM or RAM, a storage medium such as a hard disk, or an SSD, read by a processor, and executed. The memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The upper processing unit 90 performs processing for the upper layer on the MAC (Medium Access Control) layer. The upper processing unit 90 can exchange signals with the MAC processing unit 10. Typical examples of the upper layer include, but are not limited to, TCP / IP, UDP / IP, and an application layer above it. The upper processing unit 90 may include a buffer for exchanging data between the MAC layer and the upper layer. It may be connected to the wired infrastructure via the upper processing unit 90. 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 SRAM or DRAM, or a non-volatile memory such as 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 higher-level 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. Further, 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 on the MAC layer. The reception processing unit 40 performs reception processing on 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 the higher-level processing unit 90, the MAC processing unit 10 (more specifically, the MAC common processing unit 20), and the PHY processing unit 50, respectively. The MAC / PHY management unit 60 manages the MAC operation and the PHY operation in the wireless communication device.

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

The wireless communication device according to the present embodiment includes (integrates) the antenna 80 as a component in one chip, so that the mounting area of the antenna 80 can be suppressed to a small size. Further, in the wireless communication device according to the present embodiment, as shown in FIG. 1, the transmission processing unit 30 and the reception processing unit 40 share N antennas 80. By sharing the N antennas 80 between the transmission processing unit 30 and the reception processing unit 40, the wireless communication device of FIG. 1 can be miniaturized. Of course, the wireless communication device according to the present embodiment may have a configuration different from that illustrated in FIG.

When receiving a signal from a 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 it 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 thereof. The detected reception level is compared with the carrier sense level (threshold value), 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. Is output to the MAC processing unit 10 (more accurately, the receiving 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 accurately, the receiving processing unit 40). ..

The PHY processing unit 50 is a multi-user MIMO (Multi-user Multi-Import Multi-Automat: MU-MIMO) or orthogonal frequency division multiple access (Orthogonal Frequency) communication as uplink multi-user (UL-MU: Uplink Multiuser) communication.
Performs processing related to Multiplexing Access: OFDMA). Uplink MU-MIMO is described as UL-MU-MIMO, and uplink OFDMA is described as UL-OFDMA. The downlink MU-MIMO is described as DL-MU-MIMO, and the downlink OFDMA is described as DL-OFDMA.

In UL-MU-MIMO, a base station simultaneously receives frames transmitted by spatial multiplexing (simultaneously in the same frequency band) from a plurality of terminals with a plurality of antennas, and MIMO demodulates the received signals. This is a communication method that separates into the frame of the terminal. Using the preamble signal added to the beginning of the frame transmitted from each terminal, the base station estimates the propagation path response of the uplink. The preamble signals are orthogonal to each other between the terminals. The base station can correctly spatially separate (decode) the fields after the preamble signal by using the propagation path response. The printable signal corresponds to an example of the resource according to the present embodiment.

OFDMA is a method in which a plurality of resource units including one or a plurality of subcarriers are assigned to a plurality of terminals, and transmission / reception is simultaneously performed between a base station and a plurality of terminals. The resource unit is a frequency component that is the minimum unit of the resource for communication, and corresponds to an example of the resource according to the present embodiment.

Further details of UL-MU-MIMO and OFDMA will be described later. The PHY processing unit 50 may perform processing related to a method in which UL-MU-MIMO and UL-OFDMA are combined.

The PHY processing unit 50 extracts the payload by performing decoding (including demodulation and decoding of the error correction code) processing, processing for removing the physical header (PHY header) including the preamble, and the like on the received signal. According to the IEEE802.11 standard, this payload is used on the PHY side as a PSDU (physical layer concern process).
(PLCP) service data unit) is called. The PHY processing unit 50 passes the extracted payload to the reception processing unit 40, and the reception processing unit 40 treats this as a MAC frame. According to the IEEE802.11 standard, this MAC frame is referred to as an MPDU (medium access protocol (MAC) protocol data).
It is called unit). In addition, the PHY processing unit 50 notifies the reception processing unit 40 to that effect when the signal reception is started, and notifies the reception processing unit 40 to that effect when the signal reception is completed. Further, 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 end of signal reception and indicates that the medium is idle. The indicated signal is passed to the reception processing unit 40. When the PHY processing unit 50 detects an error in the received signal, the PHY processing unit 50 notifies the receiving processing unit 40 that the error has been detected with an appropriate error code corresponding to the error type. Further, when the PHY processing unit 50 determines that the medium is 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 the transfer of transmission data from the upper processing unit 90 to the transmission processing unit 30 and the transfer of received data from the reception processing unit 40 to the upper processing unit 90, respectively. In the IEEE 802.11 standard, this data in a MAC data frame is called MSDU (medium access control (MAC) service data unit). Further, the MAC common processing unit 20 once receives an instruction from the MAC / PHY management unit 60, converts the instruction into a transmission processing unit 30 and a reception processing unit 40, and outputs the instruction to the transmission processing unit 30 and the reception processing unit 40, respectively.

The MAC / PHY management unit 60 corresponds to, for example, SME (Station Management Entertainment) in the IEEE802.11 standard. In that case, the interface between the MAC / PHY management unit 60 and the MAC common processing unit 20 is the MLME SAP (MAC subLayer Management) in the IEEE802.11 standard.
The interface between the MAC / PHY management unit 60 and the PHY processing unit 50 corresponds to the Entry Service Access Point), and the interface between the MAC / PHY management unit 60 and the PHY processing unit 50 is the PLME SAP (Physical Layer Management Facility) in the IEEE802.11 wireless LAN (Local Area Network). Equivalent to.

In FIG. 1, the MAC / PHY management unit 60 is drawn as if the functional unit for MAC management and the functional unit for PHY management are integrated, but even if they are implemented separately. Good.

The MAC / PHY management unit 60 holds a management information base (MIB). The MIB holds various information such as the ability of the own terminal and whether various functions are valid or invalid. For example, whether or not the own terminal supports UL-MU (UL-MU-MIMO or UL-OFDMA), and if it supports UL-MU, whether the UL-MU capability is enabled (on) / disabled (off). Information may also be retained. 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 the 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 rewrite the rewritable parameters in the memory. It can be performed. The memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM. Further, instead of the memory, a storage device such as an SSD or a hard disk may be used. In the base station, such information of another terminal as a non-base station can also be acquired by the notification from the terminal. In that case, the MAC / PHY management unit 60 can refer to and rewrite information about other terminals. Alternatively, the memory for storing information about these other terminals may be retained and managed separately from the MIB. In that case, the MAC / PHY management unit 60 or the MAC common processing unit 20 makes it possible to refer to and rewrite the other memory. Further, the MAC / PHY management unit 60 of the base station selects a terminal to which resources for UL-MU are simultaneously allocated based on various information about the terminal as a non-base station or a request from the terminal when implementing UL-MU. It may also have a selection function. 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. Further, the MAC / PHY management unit 60 of the base station may define and manage a support rate set which is a rate set supported by the base station. The support rate set may include a rate that the terminal connected to the base station must support 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 managing communication links with other terminals. As a management frame, for example, there is a beacon frame for notifying the attributes and synchronization information of the group in order to form a wireless communication group which is a Basic Service Set (BSS) in the IEEE802.11 standard. There are also frames that are exchanged for authentication or for establishing communication links. Here, it is expressed that a communication link has been established in a state in which one terminal has exchanged information necessary for carrying out wireless communication with another terminal. As necessary information exchange, for example, there is notification of the function supported by the own terminal (for example, whether or not the UL-MU is supported, information on turning on / off the UL-MU capability, etc.), and negotiation regarding the setting of the method. The management frame is generated by the transmission processing unit 30 based on an instruction received 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 has a notification means for notifying other terminals of various information via the management frame. Examples of this management frame include an Association Request frame used in an association process, which is one of the procedures for a terminal to authenticate with a base station, and a Response Request frame used in a rear association process. The base station may notify the terminal of the non-base station via the management frame, such as whether or not the UL-MU is supported and information on turning on / off the UL-MU capability. Examples of the management frame used for this include a Beacon frame and a Probe Response frame which is a response to a Probe Request frame transmitted by a non-base station terminal. The base station may have a function of grouping a group of terminals connected to its own device. The above-mentioned notification means of the base station may notify the group ID, which is the group identifier of the group to which each terminal belongs, via the management frame. As this management frame, for example, there is a Group ID Management frame. The group ID is, for example, the group ID (6 bits) defined for downlink MU-MIMO (Multi-User Multi-Input Multi-Automat) (DL-MU-MIMO) in IEEE Std 802.11ac-2013. -The case of MU may be extended to include the case, or a group ID defined by another method may be used.

Here, the association ID (AID) will be described. AID is an association process for connecting a terminal to a base station and allowing BSS under the base station to exchange data frames, and is a terminal identifier (terminal identifier) assigned by the base station. Specifically, the association process transmits an Association Request frame from the terminal to the base station, transmits an Association Response frame from the base station to the terminal, and the terminal Status Code field in the Association Response frame is "0", that is, access. Is a successful process. Both the Association Request frame and the Association Response frame contain the communication capability (Capacity) of the transmitting terminal, so that both receiving parties can grasp the communication capability of the other party. When the terminal Status Code field in the Association Response frame is "0", that is, success, the AID is extracted from the AID field (16 bits) in the same frame and used as the AID of the destination terminal of the frame. That is, at this point, the AID is assigned from the base station to the terminal, and the AID is valid as the terminal. In a state where the base station is associated with the terminal, the AID of the terminal is valid. On the other hand, when the base station transmits a Dissociation frame to the terminal and the terminal receives it, or when the terminal transmits a Dissociation frame to the base station, the AID of the terminal becomes invalid (null). Naturally, AID is invalid for terminals that have not undergone the association process with any base station. The state in which the AID is invalid can also be said to be the state in which the AID is not specified.

The reception processing unit 40 has a receiving means for receiving various information from another terminal via a management frame. As an example, the receiving means of the base station may receive information on the availability of UL-MU or the on / off of its capability from the terminal as a non-base station. Further, when the terminal as the non-base station is a legacy terminal (such as a terminal compatible with the IEEE802.11a / b / g / n / ac standard), information on the compatible channel width (maximum available channel width) can be obtained. You may receive it. The receiving means of the terminal may receive information on UL-MU compatibility from the base station.

The example of 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, a UL-MU compatible terminal may notify a base station of information about a resource that it wants to use in UL-MU transmission. In this case, the base station may allocate resources for UL-MU communication to each terminal based on the information.

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 the user's application operation, and the data is carried by the 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 puts the data in the frame body field. A data frame is generated by adding a MAC header. Then, 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 PHY processing unit 50 receives a physical packet, the physical layer is processed based on the physical header to extract a MAC frame (here, a data frame), and the data frame is passed to the reception processing unit 40. When the reception processing unit 40 receives a data frame (when it grasps 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 extracts the extracted data via the MAC common processing unit 20. And pass it to the upper processing unit 90. As a result, application operations such as data writing and playback occur.

The control frame is used for control when transmitting / receiving (exchanged) a management frame and a data frame with another wireless communication device. The control frame includes, for example, an RTS (Request to Send) frame and a CTS (Clear to) that are exchanged with another wireless communication device to reserve a wireless medium before starting the exchange of the management frame and the data frame. Send) There is a frame and so on. Further, as another control frame, there is a delivery confirmation response frame for confirming the delivery of the received management frame and data frame. Examples of the delivery acknowledgment frame include an ACK (Acknowledgement) frame and a BA (Block Ac) frame. Since the CTS frame is also transmitted as a response of the RTS frame, it can be said that it is a frame representing 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 TXOP (Transmission Opportunity; TXOP), which indicates the time during which the medium can be occupied after the acquisition of CFP (Contention Free Period) or access right (transmission right), that is, to a wireless medium. It is a frame that allows access. 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 the necessity of transmitting the response frame (control frame) and generates the frame. Necessary information (type of control frame, information to be set in RA (Receiver Addless) field, etc.) is sent to the transmission processing unit 30 together with a transmission instruction. The transmission processing unit 30 generates an appropriate control frame based on the information required for the frame generation and the transmission instruction.

When the MAC processing unit 10 transmits a MAC frame based on CSMA / CA (Carrier Sense Multiple Access with Carrier Assistance), it is necessary to acquire an access right (transmission right) on the wireless medium. The transmission processing unit 30 measures the 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 further passes a MAC frame. In addition to the transmission instruction, the transmission processing unit 30 may instruct the modulation method and the coding method used for the transmission together. In addition to these, the transmission processing unit 30 may instruct the transmission power. When the MAC processing unit 10 obtains TXOP (Transmission Operation; TXOP) indicating the time during which the medium can be occupied after acquiring the access right (transmission right), the MAC processing unit 10 is accompanied by restrictions such as a Quality of Service (QoS) attribute, but other MAC frames can be continuously exchanged with wireless communication devices. TXOP is acquired, for example, when a wireless communication device transmits a predetermined frame (for example, RTS frame) based on CSMA / CA and correctly receives a response frame (for example, CTS frame) from another wireless communication device. When this predetermined frame is received by the other wireless communication device, the other wireless communication device transmits the response frame after the minimum frame interval (Short InterFrame Space; SIFS). Further, as a method of acquiring TXOP without using an RTS frame, for example, a data frame requesting transmission of a delivery acknowledgment frame by direct unicast (a frame having a shape in which frames are concatenated as described later, or a payload is concatenated). It may be a frame of a shaped shape) or a management frame may be transmitted and a delivery acknowledgment frame (ACK frame or BlockACK frame) for the management frame may be correctly received. Alternatively, if a frame that does not require another wireless communication device to transmit the delivery confirmation response frame and the duration / ID field of the frame is set to a period longer than the time required to transmit the frame is transmitted. , It may be interpreted that the usage right for the period described in the Duration / ID field has been acquired from the stage when the frame is transmitted.

The reception processing unit 40 manages the carrier sense information described above. This carrier sense information is based on the physical carrier sense information regarding the busy / idle of the medium (CCA) input from the PHY processing unit 50 and the medium reservation time described in the reception frame. Includes both virtual carrier sense information. If either carrier sense information is busy, the medium is considered busy and transmission is prohibited during that time. In the IEEE802.11 standard, the media reservation time is described in the Duration / ID 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 the medium is busy, or a period during which the medium is virtually busy is called a NAV (Network Allocation Vector). It can be said that the medium reservation time represents the length of the period for instructing the suppression of access to the wireless medium, that is, the length of the period for postponing the access to the wireless medium.

The reception processing unit 40 manages access to the wireless medium based on the carrier sense information. When transmitting a MAC frame, the state of the wireless medium is determined by using the backoff algorithm based on the carrier sense information, and if the wireless medium is in the idle state, the access right is acquired and the transmission processing unit 30 is transmitted. Use to send MAC frames. In addition, the reception processing unit 40 executes EDCA (Alternated Current Distributed Channel Access), which is a priority control using an access category (AC). In EDCA, the minimum value CWmin, the maximum value CWmax, AIFSN (AIFS Number), and TXOP limit (upper limit value of TXOP) of the contention window are defined as EDCA parameters for each AC. One of the features of the present embodiment is to control these parameters to be changed according to the history of UL-MU transmission or the setting state of enabling or disabling the ability of UL-MU transmission. As an example, the history of UL-MU transmission includes the presence / absence of execution of UL-MU transmission, the number of executions of UL-MU transmission, the execution result of success or failure of UL-MU transmission, and UL-MU transmission (for example, the reference UL). -Includes at least one of the elapsed time from (MU transmission, UL-MU transmission performed at a predetermined point in time, etc.). The EDCA parameter may be controlled by the MAC / PHY management unit 60 instead of the reception processing unit 40, or by another processing circuit in the MAC processing unit 10. The details of EDCA and EDCA parameters will be described later.

Here, the data frame may be configured to concatenate a plurality of MAC frames or payload portions of a plurality of MAC frames. The former is called A (Aggregate) -MPDU in the IEEE802.11 standard, and the latter is called A (Aggregate) -MSDU (MAC service data unit). In the case of A-MPDU, a plurality of MPDUs are connected in the PSDU. Moreover, not only the data frame but also the management frame and the control frame are to be connected. In the case of A-MSDU, MSDUs, which are a plurality of data payloads, are concatenated in the frame body of one MPDU. In both A-MPDU and A-MSDU, delimiter information (length information, etc.) is stored in a data frame so that the concatenation of a plurality of MPDUs and the concatenation of a plurality of MSDUs can be appropriately separated by the receiving terminal. Has been done. Both A-MPDU and A-MSDU may be used in combination. Further, the A-MPDU may target only one MAC frame instead of a plurality of MAC frames, and in this case also, the delimiter information is stored in the data frame.
When A-MPDU or the like is received, the responses to a plurality of connected MAC frames are collectively transmitted. In this case, a BA (Block Ac) frame is used instead of the ACK frame. In the following description and figures, the notation of MPDU may be used, but this also includes the case of A-MPDU or A-MSDU described above.

In the IEEE 802.11 standard, non-base station terminals join the BSS (this is called the Infrastructure BSS), which is mainly composed of base stations, and data frames can be exchanged within the BSS. A plurality of procedures are defined step by step. For example, there is a procedure called association, and a terminal of a non-base station transmits an association request frame to a base station for which the terminal requests a connection. The base station transmits an ACK frame for the association request frame, and then transmits an association response frame, which is a response to the association request frame.

The terminal stores the capacity of its own terminal in the association request frame, and can notify the base station of the capacity of its own terminal by transmitting it. For example, the terminal may transmit information for identifying the channel and / or resource unit that the terminal can support, or the standard that the terminal supports, in the association request frame. This information may also be set in a frame transmitted by a procedure called reassociation for reconnecting to another base station.
In this reassociation procedure, the terminal transmits a reassociation request frame to another base station requesting reconnection. The other base station transmits an ACK frame for the reassociation request frame, and then transmits a reassociation response frame, which is a response to the reassociation request frame.

As the management frame, a beacon frame, a probe response frame, or the like may be used in addition to the association request frame and the reassociation request frame. The beacon frame is basically transmitted by the base station, and can store parameters indicating the attributes of the BSS as well as parameters notifying the capabilities of the base station itself. Therefore, as a parameter for notifying the ability of the base station itself, information on whether or not the base station can support UL-MU or whether or not the ability is on / off may be added. Further, as another parameter, information on the supported rate of the base station may be notified. The support rate may include a rate that a terminal participating in the BSS formed by the base station must support and an optional rate. The probe response frame is a frame that receives a probe request frame from a terminal that transmits a beacon frame and transmits it in response to the probe request frame. Since the probe response frame basically notifies the same content as the beacon frame, the base station notifies the terminal that transmitted the probe request frame of its own capability even if the probe response frame is used. be able to. By giving this notification to the UL-MU compatible terminal, the terminal may perform an operation such as enabling the UL-MU communication function of the own terminal, for example.

In addition, the terminal may notify the information of the rate that the own terminal can execute among the support rates of the base station as the information for notifying the base station about the ability of the own terminal. However, for the required rate among the support rates, the terminal connected to the base station shall have the ability to execute the required rate.

If some of the information handled above determines the content of other information by notifying certain information, the notification can be omitted. For example, consider the case where an ability to support a certain new standard or specification is defined, and if it corresponds to it, it is naturally a UL-MU compatible terminal. In this case, it is not necessary to explicitly notify the existence of the ability to correspond to the standard or the specification as the above-mentioned information, and explicitly notify that the terminal is a UL-MU compatible terminal as the above-mentioned other information.

FIG. 2 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. BSS (Basic Service Set) 1 is formed by the base station 100 and the subordinate terminals 1 to 8. This system is a wireless LAN system conforming to the IEEE802.11 standard using CSMA / CA (Carrier Sense Multiple Access with Carrier Availability). The terminals 1 to 8 include at least a plurality of UL-MU compatible terminals (hereinafter, may be referred to as HE (High Efficiency) terminals), and other legacy terminals may be included. Legacy terminals include Non-HE terminals that support QoS but not UL-MU, and Non-QoS terminals that do not support either QoS or UL-MU. Specifically, the legacy terminal is a terminal compatible with the IEEE802.11a / b / g / n / ac standard. The UL-MU compatible terminal is capable of UL-MU communication such as UL-MU-MIMO or UL-OFDMA with the base station 100.

FIG. 3A shows an example of a basic format of a MAC frame. The data frame, management frame, and control frame according to the present embodiment are based on such a frame format. This frame format includes MAC header, Frame body, and FCS fields. As shown in FIG. 3B, the MAC header includes fields of Frame Control, Duration / ID, Addless1, Addless2, Addless3, Quality Control, Quality Control, and HT (High Throughput) control.

Not all of these fields need to be present, and some fields may not be present. For example, the Addless3 field may not exist. Also, the QoS Control and / or HT Control fields may not be present. It is also possible that the frame body field does not exist. There may also be other fields not shown in FIG. For example, there may be more Addless4 fields. In the case of the trigger frame described later, the common information field and the terminal information field may exist in the frame body field or the MAC header.

The recipient address (Receiver Address; RA) is entered in the field of Addless1, the source address (Transmitter Address; TA) is entered in the field of Addless2, and the field of Addless3 is a BSS identifier according to the purpose of the frame. BSSID (Basic Service Set Identifier) or TA is entered. The BSSID may be a wildcard BSSID (all bits are 1) that targets all BSSIDs.

The Frame Control field includes two fields such as a type (Type) and a subtype (Subtype). The data frame, the management frame, and the control frame are roughly classified in the Type field, and the detailed types in the roughly classified frames are performed in the Subtype field. For example, control frames include BA (Block Ac) frames, BAR (Block Ac Request) frames, RTS (Request to Send) frames, and CTS (Clear to Send) frames. These frames are identified by Subtype. It is done in the field. Trigger frames, which will be described later, may also be distinguished by a combination of type and subtype. As an example, trigger frames are classified as control frames (type "control").

The Duration / ID field describes the media reservation time, and when a MAC frame addressed to another terminal is received, the medium is virtually busy from the end of the physical packet containing the MAC frame to the media reservation time. Is determined. Such a mechanism for virtually determining the medium to be busy, or a period for virtually determining the medium to be busy is called a NAV (Network Allocation Vector), as described above. The QoS field is used to perform QoS control for transmitting in consideration of the priority of the frame. The HT Control field is a field introduced in IEEE802.11n. The HT (High Throughput) Control field exists when the order field is set to 1 at the time of the QoS data or the management frame. The HT Control field is also VHT (Very High Throughput) Control field is also HE (High)
It can also be extended to the Effective) Control field, and can notify according to various functions of IEEE802.11n, IEEE802.11ac, or IEEE802.11ax, respectively.

In the management frame, the information element (Information element; IE) to which a unique Identifier (Identifier) is assigned is framed.
Set in the Body field. One or more information elements can be set in the frame body field after the unique field according to the type of management frame. As shown in FIG. 4, the information element has each field of an Element ID field, a Length field, and an Information field. The information element is identified by an Element ID. The information field stores the content of the information to be notified, and the Length field stores the length information of the information field.

FCS (Frame Check Sequence) information is set in the FCS field as a checksum code used for frame error detection on the receiving side. As an example of FCS information, there is CRC (Cyclic Redundancy Code) and the like.

(First operation example of this embodiment)
FIG. 5 shows a first example of an operation sequence between the base station (AP) 101 and the terminals (STA) 1 to 8 according to the present embodiment. In the figure, of the terminals 1 to 8, only the terminal 1 and the terminal 2 are shown. It is assumed that terminals 1 to 4 are HE terminals and terminals 5 to 8 are legacy terminals (Non-HE terminals or Non-Qos terminals).

As a premise, communication (single user communication) is individually performed between the base station and a part or all of the terminals 1 to 8 on a CSMA / CA basis. In single-user communication, for example, one channel having a basic channel width (for example, 20 MHz) is used for individual communication between a base station and a terminal. As an example of single-user communication, when the terminal holds data for uplink transmission, the access right to the wireless medium is acquired according to CSMA / CA. Therefore, the terminal performs carrier sense during the carrier sense time (standby time), which is the sum of the fixed time DIFS / AIFS and the randomly determined backoff time, and the medium (CCA) is idle. If determined, gain access to the medium. The terminal transmits a data frame containing the data to be transmitted (more specifically, a physical packet including the data frame). The RA of the data frame is the MAC address of the base station (that is, BSSID), and the TA is the MAC address of the terminal. When the base station normally receives this data frame, it returns an ACK frame (more specifically, a physical packet including the ACK frame) which is a delivery acknowledgment frame after SIFS from the completion of receiving the data frame. By receiving the ACK frame, the terminal determines that the data frame has been successfully transmitted. The data frame transmitted to the base station may be an aggregation frame (A-MPDU or the like), and the delivery confirmation response frame to which the base station responds may be a BA frame (the same applies hereinafter).

DIFS / AIFS means the time of either DIFS or AIFS. When it is not compatible with QoS, it refers to DIFS, and when it is compatible with QoS, it refers to AIFS (hereinafter, may be referred to as AIFS [AC]) determined according to the access category (AC: Access Category) of the data to be transmitted. The basic configuration of a physical packet is a MAC frame stored in a data field with a physical header added. As an example, as shown in FIG. 6, the physical header includes L-STF (Legacy-Short Training Field), L-LTF (Legacy-Long Training Field), and L-SIG (Legacy Signal) defined in the IEEE802.11 standard. Field), including. L-STF, L-LTF, and L-SIG are fields that can be recognized by terminals of legacy standards such as IEEE802.11a, and are signal detection, frequency correction (propagation path estimation), and transmission speed (transmission rate), respectively. Information such as is stored. Fields other than those described here (for example, fields that cannot be recognized by legacy standard terminals and can be recognized by UL-MU compatible terminals) may be included. For example, HE-SIG-A (and HE-SIG-B), HE-STF, HE-LTF and the like examined in IEEE802.11ax may be included.

Here, the above-mentioned backoff time is an integer randomly selected from a contention window (CW) given as an integer from 0 multiplied by a slot time (for example, 9 μs). The initial value of CW is the minimum value (CWmin), and each time it is retransmitted, the value of CW is gradually increased until it reaches the maximum value (CWmax). Both CWmin and CWmax have a value for each AC (access category) like AIFS.

There is EDCA (Enhanced Distributed Channel Access) as a priority control method using AC. A brief description of EDCA will be given. In the IEEE802.11 standard wireless LAN, when data is passed from the upper layer (LLC layer, etc.) to the MAC layer, if the terminal supports Quality of Service (QoS), the traffic type (TID) is set together with the data. You will be notified. According to the existing standard, the terminals compatible with IEEE802.11n and IEEE802.11ac support QoS.

The data is classified into four ACs, for example, based on the traffic type. As an example, the TID value exists from 0 to 15, 0 to 7 are used in terminals (including base stations) in the EDCA environment, and 8 to 15 are HCCA (hybrid coordination function (HCF) controlled channel access (HCC) control channel access ( It is used in terminals (including base stations) in an HCCA)) environment or a HEMM (HCCA, EDCA mixed mode) environment. Here, assuming an EDCA environment, it is classified into one of four ACs according to which of 0 to 7 the TID value is.

As the type of AC, BACKGROUND (AC_BK), BEST EFFORT (AC_BE), VIDEO (AC_VI), and VOICE (AC_VO) are defined. The priority of each AC is AC_BK, AC_BE, AC_VI, AC_VO in order from the lowest. A transmission buffer (transmission queue) is provided for each of the four ACs, and the classified data is stored in the corresponding transmission buffer. The transmission buffer may be a memory, an SSD, a hard disk, or the like. When the transmission buffer is a memory, the memory may be a volatile memory such as DRAM or SRAM, or a non-volatile memory such as NAND or MRAM.

A plurality of EDCA parameters are defined for each AC, and these parameters determine the difference in the priority of media access at the time of transmission. Examples of parameters include CWmin, CWmax, AIFSN, and TXOP limit (Max TXOP). CWmin and CWmax are the minimum and maximum values of CW. AIFSN stands for AIFS Number and corresponds to the time length of AIFS. The TXOP limit represents the upper limit value (maximum value) of the TXOP that can be acquired. AIFSN, CWmin and CWmax are set to smaller values as AC has a higher priority for media access. On the contrary, the TXOP limit tends to be set to a larger value as the AC has a higher priority of medium access, but the AC_VI is basically a larger value than the AC_VO. This takes into account the characteristics of the traffic type.

FIG. 7 shows an example of the values of a plurality of EDCA parameters for each access category. If it is not compatible with QoS (for Non-QoS terminals), the access category is set to Legacy for convenience.
It is described as DCF (Distributed Coordination Foundation). DCF is an access method similar to EDCA, but without the concept of QoS control (priority control based on AC). When the value of Max TXOP (TXOP limit) is 0, it means that only one frame (more specifically, one MSDU) can be transmitted. The value of the EDCA parameter in FIG. 7 is a default value, and the value of the EDCA parameter can be set in advance for each base station (BSS). In the present embodiment, the illustrated default EDCA parameter value or the EDCA parameter value preset by the base station is referred to as a normal EDCA parameter value. For example, the illustrated TXOP limit value may be referred to as a normal TXOP limit value.

In the EDCA environment, in the terminals (HE terminal and QoS terminal), the procedure for data transmission based on CSMA / CA is performed independently for each AC having the data for transmission. That is, for each AC, carrier sense is performed during the waiting time including AIFS [AC] according to the type of AC and the backoff time, and the AC whose waiting time becomes zero first acquires the access right. To do. When there are a plurality of ACs whose standby times are zero at the same time, the AC having a higher priority for media access acquires the access right. In the Non-QoS terminal, as described above, the waiting time including the DIFS and the backoff time and the carrier sense are performed, and it is determined that the medium (CCA) is idle until the end of the waiting time. , Gain access to the medium.

In FIG. 5, it is assumed that the base station holds the trigger frame 51 of the UL-MU in the transmission buffer. The trigger frame 51 includes information for designating a plurality of terminals for UL-MU transmission, information on various parameters used by each terminal for UL-MU transmission, and the like. Examples of parameter information include information on resources used in UL-MU transmission, information on transmission packet length, information on transmission power, and the like. Further, the information may be information that specifies or recommends the AC of the data to be transmitted by UL-MU transmission. The information of the parameter may be individually specified for each terminal or may be specified in common for a plurality of terminals. The RA set in the MAC header is, for example, a broadcast address or a multicast address. TA is the MAC address (BSSID) of the base station. An example of the format of the trigger frame will be described later.

Further, the terminal 1 holds the data of AC_VO (access category is Voice), and the terminal 2 holds the data of AC_BE (access category is BestEffort) in the transmission buffer of the corresponding AC. It is assumed that neither the base station, the terminal 1 nor the terminal 2 holds data for ACs other than these. The EDCA parameter applied to the trigger frame is the same as the value of the parameter of VO (Voice), which is the most preferred AC. However, the trigger frame may be the same as the value of another AC parameter, or the value for the trigger frame can be defined separately.

The base station, the terminal 1, and the terminal 2 perform carrier sense during the standby time, which is the sum of the AIFS [AC] corresponding to the AC and the backoff time, respectively. AIFS [AC] elapses without detecting a carrier in any of the base station, the terminal 1, and the terminal 2, and the carrier sense is continuously performed during the subsequent backoff time. An example of the value of the backoff counter at a certain time point (assumed to be t1) of the backoff time is shown in FIG. 8 (A). At time point t1, the base station backoff counter (AC_CW) points to 3, the terminal 1 backoff counter (EDCA_CW_VO) points to 4, and the terminal 2 backoff counter (EDCA_CW_BE) points to 15. Therefore, after this, it can be seen that the backoff counter of the base station becomes 0 earliest.

When the backoff counter of the base station becomes 0 without detecting the carrier, that is, when the backoff time elapses, the base station acquires the access right to the radio medium and transmits the trigger frame 51. More specifically, a physical packet in which a physical header is added to the trigger frame 51 is transmitted. The trigger frame 51 is received by terminals 1 and 2 (and other terminals not shown). The terminal 1 and the terminal 2 determine that the carrier has been detected by receiving the signal carrying the trigger frame 51, and stop the backoff operation. That is, the back-off counters of the terminal 1 and the terminal 2 are stopped. The values of the back-off counters at the base station, the terminal 1 and the terminal 2 at this time point (referred to as t2) are shown in FIG. 8 (B). The counter value is 0 at the base station, 1 (= 4-3) at the terminal 1, and 12 (= 15-3) at the terminal 2.

When the terminal 1 and the terminal 2 that have received the trigger frame 51 detect that the own terminal is specified in the trigger frame 51, they read data from the corresponding transmission buffer for AC and generate a data frame containing the data. Then, the physical packets (PPDU) 52 and 53 with the physical header added to the data frame are transmitted by UL-MU after a predetermined time from the completion of reception of the trigger frame 51. When a physical packet length (PPDU length) common to a plurality of terminals is specified in the trigger frame, the terminals 1 and 2 generate a physical packet having the specified length. If the packet length to be generated is less than the specified length, the physical packet length is adjusted by adding padding data to the end.

The predetermined time may be SIFS or a value larger than this. UL-MU is, for example, UL-MU-MIMO or UL-OFDMA or a method in which these are combined (UL-MU-MIMO & OFDMA). Which method to use may be predetermined by the BSS or may be specified by the trigger frame.

The base station that has received the physical packets 52 and 53 transmits the delivery confirmation response frame 54 after a predetermined time (SIFS or the like) from the completion of receiving these physical packets. Here, as the delivery confirmation response frame, the Multi-STA BA frame (hereinafter, M-BA frame) 54 including the delivery confirmation to the terminal 1 and the terminal 2 is transmitted. An example of the format of the M-BA frame will be described later. The delivery confirmation response method may be a method other than the transmission of the M-BA frame. For example, the ACK frame (or BA frame) may be sequentially transmitted to the terminal 1 and the terminal 2 by a single user. Alternatively, an ACK frame (or BA frame) may be transmitted to the terminal 1 and the terminal 2 by DL-MU. DL-MU is, for example, DL-MU-MIMO or DL-OFDMA or a method in which these are combined (DL-MU-MIMO & OFDMA).

The terminal 1 and the terminal 2 that have received the M-BA frame 54 confirm whether or not the transmission of the data frame is successful by confirming the information addressed to the own terminal included in the M-BA frame 54. When the terminal 1 and the terminal 2 determine that the transmission has failed, they decide to retransmit the corresponding data frame at the next opportunity or later. Here, it is assumed that both the terminal 1 and the terminal 2 succeed in transmission.

After the transmission of the M-BA frame 54, the base station does not have the data or frame to be transmitted, and the terminals 1 and 2 still hold the data in the same AC transmission buffer as the previously transmitted data. Suppose you are. That is, the terminal 1 and the terminal 2 are UL-MU transmitting the data for which the access right is acquired by the carrier sense before the reception of the trigger frame 51, and the data for transmission is continuously sent to the same transmission buffer for AC. have.

Therefore, the terminal 1 and the terminal 2 start the carrier sense after a predetermined time (SIFS or the like) from the completion of receiving the M-BA frame. Specifically, the terminal 1 and the terminal 2 perform carrier sense during the standby time, which is the sum of the AIFS [AC] and the backoff time, respectively. At this time, as the backoff time, the time indicated by the value of the backoff counter (see FIG. 8B) when the trigger frame 51 is stopped when the signal is received is used. Therefore, in both the terminal 1 and the terminal 2, the value of the back-off counter when AIFS [AC] has elapsed is the value shown in FIG. 8 (B). Therefore, after this, it can be seen that the backoff counter of the terminal 1 becomes 0 at the earliest.

When the backoff counter becomes 0 at the terminal 1 without detecting the carrier, that is, when the backoff time elapses, the terminal 1 reads data from the transmission buffer for the corresponding AC to generate a data frame. A physical packet (PPDU) 55 containing a data frame is transmitted. When generating a data frame, the terminal determines TXOP within the range of the TXOP limit value (see FIG. 7) of the corresponding AC, and subtracts the packet length from the length to obtain the value obtained by subtracting the packet length from the MAC header Duration /. Set in the ID field. In the case of transmitting only one frame (only this transmission), a predetermined value (for example, 0) may be set.

The physical packet 55 is received at the base station, and a delivery confirmation response frame is transmitted to the terminal 1 after SIFS from the completion of reception. In the example of the figure, the BA frame 56 is transmitted, but if the transmitted data frame is not an A-MPDU, it may be an ACK frame. The terminal 2 determines that the carrier has been detected by receiving the signal carrying the physical packet 55, and stops the backoff operation. That is, the backoff counter of the terminal 2 is stopped. The values of the back-off counters at the terminal 1 and the terminal 2 at this time point (referred to as t3) are shown in FIG. 8 (C). Since there is no frame to be transmitted at the base station, there is no backoff counter (this is indicated as No Frame in the figure), and it is 0 for terminal 1 and 11 (= 12-1) for terminal 2. is there.

After that, the sequence is continued in the same manner. The terminal 2 continues to use the backoff counter value at t3 at the next carrier sense. When the terminal 1 has data to be further transmitted, the terminal 1 newly randomly selects a value from the CW according to the corresponding AC, and calculates the backoff time.

In the above-described sequence, both the terminal 1 and the terminal 2 succeed in UL-MU transmission, but even if they fail, the value of the backoff counter may be inherited in the same manner. Normally, when the EDCA fails, the value of the backoff counter is regained, but the value of CW for selecting the backoff counter is gradually increased each time until the maximum value (CWmax) is reached.
This normal operation may be applied. As a modification, if the UL-MU transmission fails, the value of the backoff counter may be inherited, and if it succeeds, the backoff time may be newly determined.

In the above sequence, the AC that was the target of the backoff operation before the trigger frame was received and the AC that was the target of UL-MU transmission were the same, but both ACs may be different. For example, the AC recommended or specified in the trigger frame may be different from the AC targeted for the backoff operation. In that case as well, the backoff counter value stopped at the time of receiving the trigger frame may be reused for the backoff operation for the next SU transmission. If AC is specified in the trigger frame, the terminal transmits data belonging to the AC, and if the data belonging to the AC does not exist in the transmission buffer, the terminal does not transmit UL-MU, or the data is stored. You may send a frame containing a notification that it does not exist.
When AC is recommended in the trigger frame, data belonging to the AC is transmitted as much as possible. For example, if the data belonging to the recommended AC exists in the transmission buffer, the data may be transmitted, and if it does not exist, the data belonging to another AC may be transmitted.

Similarly, when there are a plurality of ACs that were the targets of the backoff operation before the trigger frame was received and one of them was the AC that was the target of the UL-MU transmission, each AC that stopped when the trigger frame was received. The backoff counter value for may be reused in the next backoff operation.

In the trigger frame, multiple terminals for UL-MU transmission were specified, but the terminals were not specified, and resources were randomly selected from the resource group (for example, resource unit group in the case of OFDMA) where random access was permitted on the terminal side. You may use a trigger frame which allows you to select and transmit UL-MU (random access). Such a trigger frame may be called a random access trigger frame: Trigger Frame For Random Access: TF-R). In this case, in the flowchart of FIG. 9, the determination of whether or not the own terminal is specified in the trigger frame (S13 of FIG. 9) may be replaced with the determination of whether or not the terminal side randomly accesses. Then, in the case of performing random access, the process may proceed to step S14 in FIG. The terminal receiving the TF-R selects a resource based on a method similar to the random backoff method. For example, the number of resources for which random access is permitted is subtracted from the random backoff counter value randomly selected in advance, and when it becomes 0 or less, the resource is selected assuming that there is a selection right. If it is larger than 0, the random access this time is postponed, and when the next TF-R is received, the random backoff counter value after subtraction is used to determine the presence or absence of the selection right in the same manner. Details of TF-R and random access will be described later.

FIG. 9 is a flowchart of the operation of the terminal according to the first operation example of the present embodiment.

When the terminal receives the trigger frame from the base station during the back-off operation (S11), the back-off operation is stopped, that is, the back-off counter is stopped (S12). The backoff counter value at this time is maintained as it is. That is, the backoff counter value at this time is stored in the storage device. The terminal determines whether or not its own terminal is designated for UL-MU based on the trigger frame (S13). If the local terminal is specified (YES), data is read from the transmission buffer for the corresponding AC, a data frame containing the data frame is generated, and a physical packet containing the data frame is received from the completion of reception of the trigger frame. UL-MU transmission is performed after a predetermined time (S14). As described above, the AC that reads data may be an AC that has been the target of the backoff operation or an AC that is different from this, but here it is assumed that the ACs are the same.

After the UL-MU transmission, the terminal receives the delivery confirmation response frame (M-BA frame, etc.) transmitted from the base station and inspects the delivery confirmation response frame to determine whether the UL-MU transmission is successful. (S15). If there is data that has failed to be transmitted, it is decided to retransmit the data at the next and subsequent transmission (UL-MU transmission or SU transmission) opportunity.

The terminal acquires the access right for SU transmission when the own terminal is not specified in the trigger frame (NO in S13) or when the data to be UL-transmitted exists even after the UL-MU transmission (YES in S16). To do so, do a career sense. The carrier sense is performed during the waiting time, which is the sum of the fixed time AIFS [AC] and the backoff time, depending on the EDCA parameter of the corresponding AC. At this time, as the backoff time, the backoff counter value at the time of stopping in step S12 is used (S17). During the carrier sense, the terminal acquires the access right to the wireless medium if there is no carrier detection (YES in S18). When the terminal can acquire the access right, it reads data from the transmission buffer for the corresponding AC, generates a data frame, and SU-transmits a physical packet including the data frame (S19). In the above-described sequence example, the terminals 3 and 4 (HE terminals) correspond to terminals for which the own terminal was not specified in the trigger frame in step S13. When terminals 5 to 8 (legacy terminals) stop the backoff operation due to reception of the trigger frame 51 or the like, the backoff counter value of the immediately preceding backoff counter value is set as the backoff time at the time of carrier sense until the SU transmission is successful. You just have to keep using the values.

As described above, when the trigger frame is received during the backoff operation, the backoff counter is stopped, and the counter value at that time is diverted to the backoff operation for single user (SU) transmission performed after UL-MU transmission. If it is a general operation, at the next SU transmission, a new value is randomly selected from the CW to calculate the backoff time, but in the present embodiment, the backoff counter stopped when the trigger frame is received. Since the value is reused, it is possible to prevent the backoff operation performed before the trigger frame reception from being wasted. Although there is a problem of fairness in the use of wireless media between the terminal that transmitted UL-MU and the other terminals, when performing UL-MU transmission in the EDCA environment, the back-off operation of the terminal that transmitted UL-MU is performed. It can be prevented from being wasted.

(Second operation example of this embodiment)
FIG. 10 shows a second example of the operation sequence of the base station (AP) 101 and the terminals (STA) 1 to 8 according to the present embodiment. This sequence controls the terminal to change the value of the TXOP limit, which is one of the EDCA parameters, according to the history of UL-MU transmission, and uses the changed value to TXOP at the time of SU transmission. One of the features is to determine.
The TXOP limit value may be controlled by either the MAC processing unit 10 or the MAC / PHY management unit 60 of FIG.

In the following description, an example in which the value of the TXOP limit is reduced when the predetermined change condition is satisfied in the history of UL-MU transmission will be shown. The change condition is that when the own terminal is specified in the trigger frame and the UL-MU transmission is successful, a certain time has not passed from the predetermined time. If the change condition is satisfied, the value of the TXOP limit is decremented, and if the change condition is not satisfied, the normal TXOP limit value (default value in FIG. 7) is used.

In the figure, only the terminal 1, the terminal 2, and the terminal 3 are shown among the terminals 1 to 8. It is assumed that terminals 1 to 4 are HE terminals, and terminals 5 to 8 are legacy terminals (Non-HE terminals or Non-Qos terminals).

In FIG. 10, the base station holds the UL-MU trigger frame 61 in the transmission buffer. Further, the terminal 1 holds the data of AC_VO (access category is Voice), and the terminal 2 and the terminal 3 each hold the data of AC_BE (access category is BestEffort) in the transmission buffer of the corresponding AC. It is assumed that neither terminal 1 to terminal 3 holds data for ACs other than these. The value of the EDCA parameter applied to the trigger frame is the same as the value of the EDCA parameter of AC_VO.

The base station and terminals 1 to 3 perform carrier sense during the sum of AIFS [AC] and backoff time. It is assumed that AIFS [AC] has elapsed without the carrier being detected in both the base station and the terminals 1 to 3, and the carrier sense is continuously maintained during the subsequent backoff time.

It is assumed that the back-off counter of the base station becomes 0 first. The base station acquires the access right to the wireless medium and transmits the trigger frame 61. More specifically, a physical packet in which a physical header is added to the trigger frame 51 is transmitted. In the trigger frame 61, information for designating terminals 1 to 3 is specified, and parameters for UL-MU (resources to be used, packet length, transmission power, etc.) are specified for terminals 1 to 3 respectively. There is. The trigger frame 61 is received by terminals 1 to 3 (and other terminals not shown). The terminals 1 to 3 determine that the carrier has been detected by receiving the signal of the trigger frame 61, and stop the backoff operation (stop the backoff counter). The value of the backoff counter at the time of stop is stored.

The terminals 1 to 3 that have received the trigger frame 61 detect that the own terminal is designated by analyzing the trigger frame 61. Terminals 1 to 3 set a certain time in the timer, and activate the timer when the reception of the trigger frame 61 is completed or later, for example, after a fixed time, or when the own terminal completes UL-MU transmission. Let me. Here, it is assumed that the terminals 1 to 3 start the timer when the reception of the trigger frame 61 is completed. Here, it is assumed that the value of the fixed time set in the timer is the transmission cycle of the trigger frame. In this example, the time length from the completion of transmission of the trigger frame 61 to the start of transmission of the next trigger frame (trigger frame 68 in the figure) or the time length with an extra value added so as to sufficiently include the transmission of the next trigger frame. Corresponds to. The fixed time is not limited to this, and may be longer or shorter than this. For example, it may be the length of time until the transmission of the next beacon frame, or it may be an integral multiple, for example, twice the transmission cycle of the trigger frame. If the time when the timer is activated is after the completion of reception of the trigger frame 61, the time length set in the timer may be adjusted accordingly. The value to be set in the timer may be predetermined, or may be determined by the base station and notify each terminal of the information of the value. A trigger frame may be used for the notification, or another frame (beacon frame) or the like may be used. The first activation of the timer may be at the time when the own terminal decides to transmit UL-MU, or at the time when the UL-MU transmission request is notified to the base station using the header of the management frame or the QoS data frame.

The terminals 1 to 3 read data from the transmission buffer for the corresponding AC to generate a data frame, and after a predetermined fixed time from the completion of reception of the trigger frame 61, the physical packets 62 each have a physical header added to the data frame. ~ 64 is transmitted by UL-MU. The predetermined time may be SIFS, or a value larger or smaller than this.

The base station that has received the physical packets 62 to 64 transmits the delivery confirmation response frame 65 after a predetermined time (SIFS or the like) from the completion of receiving these packets. Here, as the delivery confirmation response frame, the M-BA frame 65 including the delivery confirmation to the terminals 1 to 3 is transmitted. As described in the description of the first operation example of the present embodiment, the method of the delivery confirmation response may be a method other than the transmission of the M-BA frame.

The terminals 1 to 3 that have received the M-BA frame 65 confirm the success or failure of the data frame transmission by confirming the information addressed to the own terminal included in the M-BA frame 65. Here, it is assumed that both terminals 1 to 3 succeed in transmission. If it is determined that the transmission has failed, it is decided to retransmit the data that failed to be transmitted. The terminal that fails in transmission may not (re) start the timer by the trigger frame 61, or may continue the operation of the timer as it is. In order to prevent the timer by the trigger frame 61 from being activated by the terminal that failed to transmit, for example, the presence or absence of the delivery confirmation response frame 65 transmitted after a fixed time from the UL-MU transmission, and at least the delivery confirmation response frame 65 It is confirmed whether the delivery confirmation response regarding the UL-MU transmission of the own terminal is included, and it is determined whether to activate the timer based on the confirmation response. Here, it is assumed that the timer is continued.

After this, the base station does not hold a frame to be transmitted internally, while terminals 1 to 3 are still in the same AC transmission buffer as the data frame transmitted in the physical packets 62 to 64, respectively. It is assumed that the data for transmission is held.

The terminals 1 to 3 start carrier sense for SU transmission of the retained data after a predetermined time (SIFS or the like) from the completion of receiving the M-BA frame. Specifically, the terminals 1 to 3 perform carrier sense during the standby time, which is the sum of the AIFS [AC] and the backoff time, respectively. At this time, as the backoff time, the backoff counter value when the trigger frame 61 is stopped may be used as in the first operation example described above.
However, this is an example of this operation, and the backoff time may be newly determined from the CW at the terminals 1 to 3.

Of the terminals 1 to 3, it is assumed that the back-off counter of the terminal 1 becomes 0 first. The terminal 1 reads data from the transmission buffer of the corresponding AC, generates a data frame, and transmits a physical packet (PPDU) 66 in which a physical header is added to the data frame. When generating a data frame, TXOP is determined within the range of the TXOP limit value of the corresponding AC, and the value obtained by subtracting the packet length from the length is set in the Duration / ID field of the MAC header. In the case of transmitting only one frame (only this transmission), a predetermined value (for example, 0) may be set. At this point, the terminal 1 determines that the change condition is satisfied because the timer has not timed out. Therefore, the terminal 1 determines TXOP by using the TXOP limit value (second TXOP limit value) smaller than the normal value (default value of Max TXOP in FIG. 7) as the TXOP limit value of the AC.

As an example, assuming that the TXOP limit (first TXOP limit) before the change of the corresponding AC is Old_Max_TXOP and the changed TXOP limit (second TXOP limit) is NEW_Max_TXOP, the change is performed according to the following (Equation 1). “X” represents multiplication. α is a coefficient of 0 or more and less than 1.
NEW_Max_TXOP _{per AC} = α × Old_Max_TXOP _{per AC}
(Equation 1)

The terminal 1 _{determines TXOP within the range of NEW_Max_TXOP per AC} or less, and sets a value according to the determined time length in the Duration / ID field of the MAC header of the data frame to be transmitted in the physical packet 66. Specifically, a value obtained by subtracting the packet length (PPDU length) of the physical packet 66 from the determined TXOP is set in the Duration / ID field. When α is 0, the second TXOP limit value becomes 0, which means that only one frame can be transmitted as described above.

As another calculation example of the second TXOP limit, the packet length (PPDU length) of the physical packet 62 transmitted by the UL-MU may be subtracted from the first TXOP limit value. Alternatively, a value depending on the physical packet length (for example, a value that is larger as the packet length is longer and smaller as the packet length is shorter) may be subtracted from the first TXOP limit value.

The base station that has received the physical packet 66 transmits a delivery confirmation response frame 67 (more specifically, a physical packet in which a physical header is added to the delivery confirmation response frame 67) after a predetermined time (SIFS or the like) from the completion of reception. .. Here, the aggregation frame is carried as a data frame in the physical packet 66, and the BA frame is transmitted as a delivery confirmation response frame.

The terminal 1 that has received the BA frame 67 may continue to read data from the transmission buffer for the corresponding AC to generate a data frame and transmit a physical packet including the data frame as long as it is in the TXOP. At this time, a value corresponding to the remaining time of TXOP is set in the Duration / ID field of the MAC header of the data frame. For example, the value set in the Duration / ID field of the MAC header of the BA frame 67 may be set by subtracting the SIFS and the packet length of the physical packet to be transmitted this time. Alternatively, the value obtained by subtracting the time length from the completion of transmission of the physical packet 66 to the start of transmission of the physical packet this time and the packet length of the physical packet to be transmitted this time from the value set in the Duration / ID field of the physical packet 66 is subtracted. It may be set.

After that, the terminal 1 can repeatedly transmit the physical packet including the data frame and receive the delivery confirmation response frame at the SIFS interval as long as it is in TXOP.

After the end of TXOP, before receiving the trigger frame 68 and in a state where the timer has not yet timed out, the terminal 1 further performs carrier sense for transmission of data belonging to the AC, and accesses as the carrier sense result is idle. Suppose you have acquired the right. As the TXOP limit value used at this time, the above-mentioned second TXOP limit may be continuously used.
Alternatively, the second TXOP limit value may _{be regarded as α × Old_Max_TXOP per AC} and applied to Equation 1 to calculate a smaller value. At this time, α may be fixed, or the value of α may be decreased or increased each time the TXOP limit is updated.

When the timer times out, the terminal 1 determines that the change condition is not satisfied, and returns the TXOP limit value to the first TXOP limit value (normal TXOP limit value). When the local terminal is specified again in the trigger frame 68, the timer is started again, and if the change condition is satisfied and the access right for SU transmission is acquired while the timer is running (before time-out). Decreases the TXOP limit value used in the SU transmission. If the local terminal is specified again in the trigger frame 68 before the timer activated by the trigger frame 61 times out, the timer is reset (the timeout time is returned to the initial value) and the terminal is activated.

In the above sequence, the operation when the terminal 1 can acquire the access right is described as an example in the carrier sense for SU transmission, but the same operation is performed when the terminal 2 or the terminal 3 acquires the access right. Be told.

Since the terminal 4 is not specified by the trigger frame 61, the TXOP is determined using the first TXOP limit value (normal TXOP limit value) when the data frame for SU transmission is generated. Similarly, terminals 5 to 8 (legacy terminals) also determine TXOP using the first TXOP limit value (normal TXOP limit value) when generating a data frame for SU transmission. In this embodiment, the legacy terminal uses a normal TXOP limit value.

FIG. 11A shows an example of a sequence in which TXOP is determined within the first TXOP limit value, transmission of a physical packet including a data frame and reception of a delivery confirmation response frame (BA frame) are repeatedly performed in TXOP. In FIG. 11B, the TXOP is determined within the second TXOP limit value lower than the first TXOP limit value, and the transmission of the physical packet including the data frame and the reception of the delivery confirmation response frame (BA frame) are repeatedly performed in the TXOP. An example sequence is shown. In FIGS. 11 (A) and 11 (B), the broken line rectangle indicates that the frame is a frame (here, a BA frame) received from the base station.

In FIG. 11A, since a longer TXOP can be set, more data can be transmitted by SU. Therefore, the terminal specified by the trigger frame and successfully transmitting UL-MU (the terminal to which the second TXOP limit value is applied) and the other terminals (the terminal to which the first TXOP limit value is applied) are the wireless media. It is possible to maintain fairness in terms of use. Further, since the TXOP limit is limited in the SU transmission of the terminal that has succeeded in UL-MU transmission, the occupied period of the radio medium is reduced, and it becomes easy to secure the period in which the base station can transmit the trigger frame.

In the above sequence, the terminal specified by the trigger frame maintains the operation of the timer even if the UL-MU transmission fails, and uses the second TXOP limit value until the timer times out. This is because although the UL-MU transmission failed, it was given an opportunity to transmit, which was superior to other terminals. Alternatively, even if the terminal is specified by the trigger frame, if the UL-MU transmission fails, the timer may not be (re) activated by the trigger frame. In this case, it can be said that the response emphasizes the fact that the transmission was not successful.

In the above-described sequence, Equation 1 is calculated based on the first TXOP limit value to calculate the second TXOP limit value, but the second TXOP limit value may be stored in the database in advance. In this case, the terminal may read the second TXOP limit value from the database. A plurality of TXOP limit values (second TXOP limit to mTXOP limit. M is an integer of 3 or more) that are gradually smaller than the first TXOP limit may be stored in the database. In this case, the TXOP limit value, which is a stepwise lower value, may be used each time the access right for SU transmission is acquired by the carrier sense until the timer times out.

In the above sequence, of the EDCA parameters, only the TXOP limit is changed small, but other EDCA parameters may be changed together with the TXOP limit. As an example, CWmin, CWmax or both may be modified to be greater.
Alternatively, the AIFSN may be changed to be larger. The method of change may be the same as that of the TXOP limit. For example, it may be multiplied by a certain coefficient, or it may be a method of storing one candidate value or a plurality of values gradually increased in advance in the database. When changing AIFSN, CWmin, and CWmax, these values are used in advance for the next SU transmission, so the behavior when the timer times out while the countdown of the backoff counter has already started. You need to think.
If the timer times out while the countdown of the backoff counter has already started, for example, AIFSN or CWmin changed when the countdown is continued and the access right is acquired and the backoff counter is newly regained. Apply the CWmax value. The above-mentioned TXOP limit may be applied at the same timing. Alternatively, for CWmin and CWmax, the current value that has already been counted down is compared with the initial value of the backoff counter derived from the newly used parameter, and if the newly derived initial value is smaller, the current countdown value is used. You may replace it with the initial value.

FIG. 12 is a flowchart of the operation of the terminal according to the second operation example of the present embodiment.

When the terminal receives the trigger frame from the base station (S101), it determines whether the own terminal is designated for UL-MU based on the trigger frame (S102). When the local terminal is specified, the physical packet including the data frame is UL-MU transmitted (S103) after a predetermined time from the completion of receiving the trigger frame. After the UL-MU transmission, the terminal receives the delivery confirmation response frame (M-BA frame, etc.) transmitted from the base station and inspects the delivery confirmation response frame to determine whether the UL-MU transmission is successful. (S104).
If there is data that has failed to be transmitted, it is decided to retransmit it at the next and subsequent transmission (UL-MU transmission or SU transmission) opportunity.

If there is data that the terminal wants to transmit UL after UL-MU transmission, the terminal acquires the access right for SU transmission during the waiting time, which is the sum of AIFS [AC] and the randomly determined backoff time. , Do a career sense. During the carrier sense, the terminal acquires the access right to the wireless medium if there is no carrier detection. When the terminal can acquire the access right, the terminal reads data from the transmission buffer of the corresponding AC and generates a data frame.
At this time, the TXOP limit value to be used is determined, and the TXOP is determined within the range equal to or less than the TXOP limit value. Specifically, it is determined whether the change condition is satisfied (S106), and if the change condition is not satisfied, it is decided to use the first TXOP limit value, and the TXOP is determined in the range equal to or less than the first TXOP limit value (S106). S109). On the other hand, when the change condition is satisfied, the TXOP is determined within the range of the second TXOP limit value or less, which is smaller than the first TXOP limit value (S107). As an example, the first TXOP limit value is a default value predetermined by the system (see FIG. 7) or a value preset by the base station in the BSS.

The terminal sets the value corresponding to the determined TXOP in the Duration / ID field of the MAC header of the data frame to be transmitted. Then, the physical packet including the data frame is transmitted by SU (S108). After that, if the next trigger frame has not been received (NO in S110) and there is data to be transmitted, the process returns to step S105. As described above, the TXOP limit value may be further lowered stepwise each time the access right for SU is acquired. When the next trigger frame is received from the base station (YES in S110), the process returns to step S102.

Here, an example of the change condition will be described in detail. As in the second sequence example described above, the first change condition is constant from the completion of reception (or transmission start) of the trigger frame when the local terminal is specified in the trigger frame and the UL-MU transmission is successful. Whether or not it is included in time. If it is included in a certain period of time, the change condition is satisfied, and if it is not included, the change condition is not satisfied. The length of the fixed time may be the length of the fixed cycle, for example, when the trigger frame is transmitted at the fixed cycle. Alternatively, it may be shorter or longer than this.

As a specific implementation example, as described above, when the reception of the trigger frame is completed, the timer set to the fixed time length (for example, the cycle length of the trigger frame) is started, and the timer is changed while the timer does not time out. Judge that the conditions are met. If the timer is not running or times out, it is determined that the change conditions are not met. In this case, it is determined that the change condition is not satisfied at least until the next trigger frame is received.

The starting point for operating the timer is not limited to the time when the reception of the trigger frame is completed. A timer may be set after the completion of reception of the trigger frame, for example, when it is confirmed that the transmission of the own device is successful in the reception of the M-BA frame. In this case, the value set in the timer may be the remaining time until the reception of the next trigger frame. The value set in the timer may be appropriately adjusted according to the time at which the timer is set.

Here, an example of determining the value to be set in the timer (hereinafter, timer set value) is shown. The timer setting value can be determined by the terminal or the base station.

When determining the timer setting value on the terminal, for example, the transmission cycle of the trigger frame is observed, and the timer setting value is determined to be an integral multiple of the transmission cycle of the trigger frame. The value obtained by subtracting the packet length (PPDU length) of the trigger frame from an integral multiple of the transmission cycle may be determined as the timer set value. An integer to be multiplied by the transmission cycle may be determined according to the traffic (the amount of data in the transmission buffer, etc.) possessed by the terminal. For example, the larger the amount of data stored in the transmission buffer of AC_VO, the smaller the integer value, or the smaller the amount of data, the larger the integer value. Alternatively, the relationship may be set to the opposite.

Alternatively, the base station notifies a plurality of terminals in the BSS in advance of the transmission cycle of the trigger frame, and each terminal determines the timer setting value from the traffic (data amount) of the own terminal and the notified transmission cycle. You may. For example, a threshold value is set according to the transmission cycle, and if the traffic is equal to or less than the threshold value, the timer set value is set to a large value, and if it is larger than the threshold value, the timer set value is set to a small value. Alternatively, the relationship may be set to the opposite. The longer the transmission cycle, the larger the threshold value may be set.

When the base station determines the timer set value, for example, the base station receives a buffer status report (BSR) from a terminal belonging to the BSS, and determines the timer set value using the BSR. The BSR includes, for example, traffic information for each AC. The BSR may be placed in a QoS Control field or HE Control field, or may be transmitted as an information element in the management frame. The BSR may be spontaneously transmitted by the terminal, or the base station may send a BSR transmission request to the terminal, and the terminal may transmit the BSR in response to the request. The transmission request may be included in the trigger frame.

The base station may determine the timer set value for each terminal. For example, the more traffic the terminal has, the smaller the timer setting value, or the smaller the number, the larger the timer setting value. Alternatively, the relationship may be set to the opposite. Further, the base station may determine the timer setting value common to a plurality of terminals. In this case, the traffic (data amount) of a plurality of terminals may be statistically processed (for example, averaged) to determine the timer set value. The timer set value may be determined for each AC. The base station notifies each terminal of the timer setting value determined for each terminal or common to the terminals. A trigger frame may be used for the notification, a management frame such as a beacon frame may be used, or another frame may be used.

As a second example of the change condition, when the own terminal is specified in the trigger frame and the UL-MU transmission is successful, the predetermined frame is subsequently received. The predetermined frame may be a beacon frame. Before receiving the beacon frame, it is determined that the change condition is satisfied, and when the beacon frame is received, it is determined that the change condition is no longer satisfied. After that, when the own terminal is specified in the next trigger frame and the UL-MU transmission is successful, it is determined that the change condition is satisfied again. The period of the trigger frame is assumed to be shorter than the period of the beacon frame, but may be longer. Here, the case of the beacon frame is described as a predetermined frame, but another frame may be used. When the timing of receiving a predetermined frame is known in advance, the same operation can be realized by the method using the timer described above. The type of received frame may be determined, for example, by analyzing the type and subtype of the frame control field of the MAC header.

As a third example of the change condition, the success or failure of the change condition may be determined based on the number of times the trigger frame is received and the number of times the frame is successfully transmitted (UL-MU transmission) in response to the trigger frame. For example, if the ratio of the number of successful frame transmissions to the number of times the trigger frame is received is greater than or equal to the threshold value, the change condition may be satisfied, and if the ratio is less than the threshold value, it may be determined that the change condition is not satisfied. As an example, the second TXOP limit value is used when the change condition is satisfied, and the first TXOP limit value is used when the change condition is not satisfied. In this way, the TXOP limit value to be used is controlled based on the number of times the trigger frame is received and the number of times the frame is transmitted successfully.

As a fourth example of the change condition, the success or failure of the change condition is based on the number of times the frame is successfully transmitted (UL-MU transmission) in response to the trigger frame and the number of times the frame is successfully transmitted by the single user transmission. May be judged. For example, if the ratio of the number of successful UL-MU transmissions to the number of successful single-user transmissions is greater than or equal to the threshold value, the change condition may be satisfied, and if the ratio is less than the threshold value, it may be determined that the change condition is not satisfied. As an example, the second TXOP limit value is used when the change condition is satisfied, and the first TXOP limit value is used when the change condition is not satisfied. In this way, the TXOP limit value to be used is controlled based on the number of successful single-user transmissions and the number of successful UL-MU transmissions. That is, in this case, the value of the TXOP limit is controlled to be changed by using the history of SU transmission in addition to the history of UL-MU transmission. The history of SU transmission is based on the presence / absence of execution of SU transmission, the number of executions of SU transmission, the execution result of success or failure of SU transmission, and SU transmission (for example, reference SU transmission, SU transmission performed at a predetermined time, etc.). Includes at least one of the elapsed times of.

In the third and fourth examples of the above-mentioned change conditions, the number of times the frame is transmitted in response to the trigger frame (self) instead of the number of times the frame is successfully transmitted (UL-MU transmission) in response to the trigger frame. The device may use the specified number of times).

In the above-mentioned example of the first change condition, the second TXOP limit value is used assuming that the change condition is satisfied until the timer times out, but even if the second TXOP limit value is changed stepwise according to the elapsed time. Good. For example, as the timeout approaches, the second TXOP limit value may be increased so as to approach the first TXOP limit value.

Further, in the above-mentioned example of the third change condition, the second TXOP limit value is used assuming that the change condition is satisfied when the ratio of the number of successful frame transmissions to the number of times the trigger frame is received is equal to or greater than the threshold value. Alternatively, the TXOP limit value may be changed (the TXOP limit value is reduced) so that the larger the ratio, the larger the difference from the first TXOP limit value. Alternatively, the TXOP limit value may be controlled (the TXOP limit value is increased) so that the difference from the first TXOP limit value becomes smaller as the ratio becomes smaller.

Further, in the example of the fourth change condition, when the ratio of the number of successful UL-MU transmissions to the number of successful single user transmissions is equal to or greater than the threshold value, the change condition is satisfied, and the second TXOP limit value is used. Alternatively, the TXOP limit value may be changed (the TXOP limit value is reduced) so that the larger the ratio, the larger the difference from the first TXOP limit value. Alternatively, the TXOP limit value may be controlled (the TXOP limit value is increased) so that the difference from the first TXOP limit value becomes smaller as the ratio becomes smaller.

In the second operation example described above, the TXOP limit value is changed by the operation of the terminal side, but the base station side determines the TXOP limit value to be used in each terminal based on the history of UL-MU transmission of each terminal. Then, the determined TXOP limit value may be notified to each terminal. Other frames such as a trigger frame or a beacon frame can be used for the notification.
As a method of determining the TXOP limit value used by each terminal in the base station, the same algorithm as in the case of determining by the terminal described above may be used. It is also possible that the base station determines the TXOP limit value to be used by only one of the plurality of terminals, and the remaining terminals are their own terminals to determine the TXOP limit value to be used. In this case, the base station need only notify the at least one terminal.

The change condition to be used among the first to fourth change conditions described above may be stored in the terminal in advance, or the base station may notify each terminal of the information specifying the change condition. .. As an example, another frame such as a trigger frame or a beacon frame can be used for the notification.

As described above, in the second operation example, the TXOP limit value is slightly changed for the data belonging to the same AC as the data transmitted by UL-MU, but the TXOP limit value may be changed for other ACs as well. .. However, it is assumed that the lower limit of the TXOP limit value is 0, and if the default value of the TXOP limit is 0, the value is not reduced any more. It may be made smaller, but in this case, it is assumed that the TXOP limit value is 0, and the TXOP is determined.

For example, the AC to which the data transmitted by UL-MU in step S103 of FIG. 12 belongs (tentatively described as AC-1) and the AC to which the data to be transmitted in the SU of subsequent step S108 belongs (tentatively described as AC-2). Consider the case where is different. Also in this case, the TXOP limit value may be changed in step S107 for SU transmission of data belonging to AC-2 according to the operation flow of FIG. Alternatively, when AC-1 and AC-2 are different, the operation flow of FIG. 12 may not be applied and the TXOP limit value may not be changed (the normal TXOP limit value is used).

Further, in the second operation example described above, it is assumed that the AC of the data to be transmitted by UL-MU is determined on the terminal side, but as in the first operation example, the base station recommends AC in the trigger frame or You may specify it. The operation when AC is recommended or specified in the trigger frame may be the same as in the first operation example.

Further, in the second operation example described above, the base station may transmit a random access trigger frame (TF-R) as a trigger frame as in the first operation example. In this case, in the flowchart of FIG. 12, the determination of whether or not the own terminal is specified in the trigger frame (S102 of FIG. 12) may be replaced with the determination of whether or not the terminal side randomly accesses. Then, when it is decided to perform random access, the process may proceed to step S103 in FIG.

In the second operation example described above, the value obtained by subtracting the transmission packet length from the determined TXOP was set as the reserved time of the wireless medium in the Duration / ID field of the MAC header, but a similar field exists in the physical header. If so, the reserved time may be set in the physical header. If a field for storing the determined TXOP value exists in the physical header or the MAC header, the TXOP value may be stored in the field.

(Third operation example of this embodiment)
It is assumed that the terminal can switch between valid (Able) and invalid (Disable) of the UL-MU capability. The terminal may change the TXOP limit value according to the enabled or disabled setting state of the UL-MU capability. For example, consider the case where another system (LTE (Long Term Evolution), Bluetooth (registered trademark), etc.) that shares an antenna inside the terminal exists. When there is a radio wave interference problem between the wireless LAN circuit and another system, it is conceivable to disable the UL-MU capability in the terminal to alleviate this interference problem. In an environment where UL-MU is possible, when UL-MU is transmitted in response to a trigger frame from a base station, it is necessary to perform transmission under the conditions specified by the trigger frame (for example, with the transmission power specified by the base station). This can cause interference with other systems) as it must be transmitted). Therefore, it is conceivable that the terminal disables the UL-MU capability and shifts to the SU mode.

When the UL-MU capability is invalid, the terminal uses the normal TXOP limit value (first TXOP limit value) shown in FIG. 7. When the UL-MU capability is valid, the TXOP limit value with a lower priority (lower value) is used. The change of the TXOP limit value may be applied only to AC-VO and AC-VI whose default value of the TXOP limit is larger than 0. The TXOP limit value after this change may be predetermined, or may be determined by the base station and notified to the terminal. The notification from the base station may use a management frame such as a beacon frame or an association response frame, or may use another type of frame. Further, the above-mentioned other operation example, for example, the operation based on the timer and the enable / disable setting of the UL-MU capability may be linked. When the timer is running and the change condition is satisfied, the UL-MU ability is set to be valid, and when the timer is not started (including the time-out) and the change condition is not satisfied. Is an interlocking such as setting the UL-MU ability as invalid.

Here, the TXOP limit is described as the EDCA parameter, but the value of another EDCA parameter such as CWmin, CWmax or AIFSN may be controlled in the same manner. For example, when the UL-MU ability is invalid, the normal parameter value shown in FIG. 7 is used, and when the UL-MU ability is valid, a parameter value having a lower priority (a larger value) is used. Alternatively, when the UL-MU capability is invalid, a parameter value lower than the normal parameter value shown in FIG. 7 may be used, and when the UL-MU capability is valid, the normal parameter value shown in FIG. 7 may be used. Good. A method other than that described here may be used. The value of any combination of TXOP limit, CWmin, CWmax or AIFSN may be controlled in the same manner.

The terminal notifies the base station of information indicating whether the UL-MU capability is valid or invalid. Notification may be performed, for example, by providing an invalid field in the HE Control field and setting a bit in the field. Alternatively, the notification may be performed using the reserved area of the existing field, or may be a method of notifying valid or invalid information as an information element in an arbitrary management frame. The base station that receives the invalid notification recognizes the terminal as a terminal that cannot execute UL-MU transmission, and performs processing such as excluding it from the target of UL-MU scheduling.

FIG. 13 is a flowchart of the operation of the terminal according to the third operation example of the present embodiment. The terminal determines whether the UL-MU capability is valid or invalid at an arbitrary timing (S121). For example, interference with another system that shares an antenna in the terminal is measured, and if the measured value is a certain value or more, invalidity is determined. Alternatively, when another predetermined system is operating, another determination method such as always determining invalidity may be used. When the terminal determines whether it is valid or invalid, it notifies the base station of information indicating valid or invalid (S122). When the terminal decides to invalidate the UL-MU capability, it shifts to the SU mode and decides to use a normal TXOP limit value (first TXOP limit value) as the TXOP limit value. On the other hand, when the UL-MU capability is valid, it is determined to use the second TXOP limit value lower than the first TXOP limit value (S124).

In the above description, the terminal side controls the change of the TXOP limit value, but the base station side determines the TXOP limit value used by the terminal based on the enabled or disabled setting state of the UL-MU capability of the terminal. You may. In this case, the base station notifies the terminal of the determined TXOP limit value. It is also possible that only one of the plurality of terminals is the base station to determine the TXOP limit value used by the terminal, and the remaining terminals are the own terminals to determine the TXOP limit value to be used. In this case, the base station need only notify the at least one terminal.

(Fourth operation example of this embodiment)
The transmission of the trigger frame by the base station will be described. The following description is also applicable when the trigger frame is TF-R.

As an example, the base station periodically transmits a trigger frame. The base station performs carrier sense before transmitting the trigger frame. As described above, a carrier sense is performed between a fixed time (AIFS, etc.) and a randomly determined backoff time, and if a carrier is not detected, an access right is acquired and a trigger frame is transmitted. An example of the transmission sequence of the trigger frame in this case is shown in FIG. 14 (A). The trigger frames 51A, 51B, and 51C are transmitted at a predetermined cycle. Career sense is performed between AIFS and backoff time prior to transmission.

Alternatively, as another method of carrier sense, carrier sense may be performed during PIFS before transmission as in the case of the beacon frame, and if the carrier is not detected, access right may be acquired and the trigger frame may be transmitted. An example of the transmission sequence of the trigger frame in this case is shown in FIG. 14 (B). Carrier sense is performed during PIFS before transmission. This is the same operation as in the case of transmitting the beacon frame. As a result, the trigger frame can be transmitted like a beacon frame which is a management frame. In addition, another fixed time may be used instead of PIFS.

When the carrier is detected by the carrier sense (in the case of busy), the base station cannot acquire the access right and cannot transmit the trigger frame at the timing of the transmission cycle. In this case, the base station may perform carrier sense again and repeat carrier sense until a carrier sense result indicating an idle state is obtained. As a result, the transmission timing of the trigger frame is delayed. An example of the sequence in this case is shown in FIG. 15 (A). The transmission of the trigger frame 51A is transmitted later than the timing of the transmission cycle. This operation is the same as when the carrier sense for transmitting the beacon frame becomes busy.
That is, in the transmission of the beacon frame, when the access right cannot be acquired as the carrier sense busy, the carrier sense is repeated until the access right is acquired.

If a certain condition is satisfied during repeated carrier sense, the base station may stop (give up) the transmission of the trigger frame and wait until the next transmission timing. As a certain condition, for example, when the remaining time until the next transmission timing becomes a certain value or less, it may be decided to cancel the transmission of the trigger frame this time. Alternatively, if the threshold time is exceeded from the timing of the transmission cycle, it may be decided to cancel the transmission of the trigger frame this time. The threshold time may be determined according to the length of the transmission cycle. For example, the threshold time may be half the length of the transmission cycle. An example of the sequence in this case is shown in FIG. 15 (B). Since the carrier sense has been busy, the trigger frame 51A cannot be transmitted even if half of the transmission cycle length has elapsed from the timing of the transmission cycle. Therefore, the transmission of the trigger frame 51A is stopped.

The transmission cycle of the trigger frame may be fixed or changeable. When changing the transmission cycle, the carrier sense method may be the same as described above. When the transmission cycle can be changed, for example, the base station receives a buffer status report (BSR) from a terminal belonging to BSS. The BSR includes traffic information (such as the amount of data existing in the transmission buffer) for each AC, for example. The BSR may be placed in a QoS Control field or HE Control field, or may be transmitted as an information element in a management frame. The BSR may be spontaneously transmitted by the terminal, or a BSR transmission request may be sent from the base station and the terminal may transmit in response to the request. The request may be included in the trigger frame.

The base station may determine the transmission cycle of the trigger frame based on the BSRs received from the plurality of terminals. For example, the transmission cycle is determined according to the number of terminals and the amount of data held by each terminal. Specifically, the more terminals have a certain amount or more of data, the shorter or longer the transmission cycle may be. Further, as the number of terminals is a certain number or more and the amount of data of each terminal is large, the transmission cycle may be shortened or lengthened. This determination may be made for a specific amount of AC data, or for a total amount of data for all ACs.

As described above, the base station may recommend or specify an AC that performs UL-MU transmission in the trigger frame. In this case, the recommended or designated AC may be an AC common to all terminals, or may be an AC recommended or specified individually for each terminal. When commonly recommended or specified, the base station determines TXOP within the TXOP limit value of the AC, and in the Duration / ID field in the MAC header of the trigger frame, the NAV period (from the TXOP value to the packet length of the trigger frame). The value obtained by subtracting) may be set. As a result, the base station can set the NAV in the BSS and prevent transmission by the hidden terminal or the like during the execution of UL-MU.

Burst transmission may be performed in which the transmission of the trigger frame, the UL-MU transmission, and the transmission of the M-BA frame are continuously repeated. An example of burst transmission is shown in FIG. First, the trigger frame 61 is transmitted by the access right acquired by the radio medium as an idle by the carrier sense, and the UL-MU transmission from the plurality of terminals and the M-BA frame transmission from the base station are performed. After this, the base station transmits the trigger frame 69 after PIFS without inspecting the radio medium with carrier sense. After that, the same sequence is repeated. In such a burst transmission, the base station first performs a carrier sense for transmitting the trigger frame 61 that is the starting point of the burst transmission only once, and before the transmission of the trigger frames 69, 70, etc. during the burst transmission period. Does not require carrier sense, so efficient communication is possible. After the burst transmission is completed, the base station acquires the access right by performing carrier sense again when performing burst transmission again at an arbitrary time. When performing such burst transmission, the transmission cycle of the trigger frame may be an interval from the trigger frame 61, which is the starting point of burst transmission, to the trigger frame 71, which is the starting point of the next burst transmission. In the second operation example of the present embodiment described above, an example in which the timer is set to the transmission cycle of the trigger frame or a value corresponding to an integral multiple of the transmission cycle has been described, but this transmission cycle is the trigger frame that is the starting point of burst transmission. The transmission cycle may be.

Hereinafter, the trigger frame format, the M-BA frame format, UL-MU-MIMO, and UL-OFDMA will be described in detail.

(Trigger frame)
FIG. 17A shows an example of the format of the trigger frame. This format is based on the general MAC frame format shown in FIG. 3, and includes a Frame Control field, a Duration / ID field, an Addless1 field, an Addless2 field, a common information field (Common Info.) Field, and a plurality of terminals. It includes an information field (Per User Info.) Field and an FCS field. Specify that it is a trigger frame by Type and Subtype of the Frame Control field. Type may be "control" as an example, and Subtype may define a new value corresponding to the trigger frame. However, a trigger frame in which Type is "managed" or "data" may be defined. Instead of defining a new value as Subtype, a field for notifying that it is a trigger frame may be expressed by using a reserved field in the MAC header.

A broadcast address or a multicast address may be set as RA in the Address1 field. The MAC address (BSSID) of the base station may be set as TA in the Address2 field. However, the Addless1 field, the Addless2 field, or both may be omitted. In the common information field, parameter information to be notified in common to a plurality of terminals that specify UL-MU transmission is set. For example, information for specifying the format of the terminal information field, information for specifying the packet length to be transmitted in the response, information indicating the purpose of the trigger frame, and the type of frame to be transmitted in the response may be set. In addition, information that recommends or specifies the AC to which the data to be transmitted belongs may be set. Further, information on the number of terminal information fields may be set. Further, when a plurality of terminals belong to the same group ID, the group ID may be set. Further, the timer setting value described in the second operation example of the present embodiment may be set in the common information field. In this case, as an example, the format of the common information field shown in FIG. 17B may be used. In this example, Type-dependent Common
Before the Info subfield, a Timer Value subfield for notifying the timer setting value is provided. However, the format shown in FIG. 17B is an example, and other subfields may exist or some subfields may be omitted. The position of the Timer Value subfield is also not limited to the position shown in FIG. 17 (B).

In the plurality of terminal information fields, information for designating a terminal for UL-MU transmission (terminal identifier such as AID) and parameter information to be individually notified to the terminal are set. For example, specify information about the resources that the terminal uses for UL-MU transmission. In addition, information that specifies the transmission power used by the terminal, MCS, and the like may be set. The terminal that has received the trigger frame performs UL-MU transmission according to the parameter information specified in the common information field and the terminal information field in which the identifier of the own terminal is set. In some cases, such as when a group ID is set in the common information field, the terminal identifier may be omitted from the terminal information field.
Further, the timer setting value described in the second operation example of the present embodiment may be set in the terminal information field. In this case, as an example, the format of the terminal information field shown in FIG. 17C may be used. In this example, the Timer that notifies the timer setting value before the Type-dependent Per User Info variable subfield.
A Value subfield is provided. However, the format shown in FIG. 17C is an example, and other subfields may exist or some subfields may be omitted. The position of the Timer Value subfield is also not limited to the position shown in FIG. 17 (C).

In the case of a random access trigger frame (TF-R), the same format as in FIG. 17 can be used as an example. For example, in the terminal information field, information indicating that the use is not limited to a specific terminal is set. Specifically, "X", which is an unused AID value, may be specified. The value of X may be notified in advance from the base station to each terminal by a management frame such as a beacon frame. A resource in which "X" is set (for example, a resource unit in the case of OFDMA) is a resource that can be used by any terminal, that is, a resource for random access. The terminal randomly selects a terminal information field in which X is set, and uses the resources described therein for UL-MU transmission. In the case of TF-R, X may be set in all the terminal information fields, or the AID of the terminal may be set in some terminal information fields. In that case, the resources set in some of the terminal information fields are used by the terminal of the AID. Even if the terminal has the AID of its own device set in any of the terminal information fields, the resources described in the terminal information field in which X is set should be used in addition to the resources specified for the own terminal. May be tolerated. The terminal receiving the TF-R selects a resource based on a method similar to the random backoff method. For example, the number of resources for which "X" is set is subtracted from the random backoff counter value randomly selected in advance, and when it becomes 0 or less, it is assumed that there is a selection right, and the resource is selected. If it is larger than 0, the random access this time is postponed, and when the next TF-R is received, the random backoff counter value after subtraction is used to determine the presence or absence of the selection right in the same manner. The method of realizing the trigger frame for random access may be a method other than that described here.

It is also possible to limit the use of resources for random access to a specific terminal group or a group having a specific group ID. In the former case, a plurality of AIDs may be set. In the latter case, the group ID may be set in the terminal information field.

(Multi-STA BA frame)
The Multi-STA BA frame is a diverted Block Acc frame (BA frame) for confirming delivery to a plurality of terminals in one frame. The frame type may be Control, and the frame subtype may be BlockAck, as in the case of a normal BA frame. FIG. 18A shows a format example of the Multi-STA BA frame. FIG. 18B shows an example of the format of the BA Control field in the BA frame, and FIG. 18C shows an example of the format of the BA Information field in the BA frame. When reusing BA frames, it may be indicated in the BA Control field that it is an extended BA frame format for notifying delivery acknowledgments for multiple terminals. For example, in the 802.11 standard, when the Multi-TID subfield is 1 and the Compressed Bitmap subfield is 0, the current status is reserved. This may be used to indicate that it is an extended BA frame format for notifying delivery acknowledgments for multiple terminals. Alternatively, in FIG. 18B, the area of bits B3-B8 is a reserved subfield, but a part or all of this area is in a BA frame format extended to notify a delivery acknowledgment regarding a plurality of terminals. It may be defined to indicate that there is. Alternatively, it is not necessary to explicitly give such a notification.

The RA field in the BA frame may be a broadcast address or a multicast address as an example. In the Multi-User subfield of the BA Control field, the number of users (number of terminals) to be reported in the BA Information field may be set. In the BA Information field, for each user (terminal), a subfield for the association ID, a Block Acack start sequence control (Block Acack Starting Sequence Control) subfield, and a Block Acck bitmap (Block).
Ack Bitmap) Subfield and is placed.

AID is set in the association ID subfield to identify the user. More specifically, as shown in FIG. 18C, as an example, a part of the Per TID Info field is used as a subfield for the association ID. Currently, 12 bits (B0 to B11) are reserved areas. The first 11 bits (B0-B10) are used as a subfield for the association ID. The Block Ack start sequence control subfield and the Block Ack bitmap subfield may be omitted if the frame transmitted by the terminal is a single data frame (if it is not an aggregation frame). As another example, a partial state operation is used and the corresponding sequence number is represented by a Block Acc bitmap subfield. When the frame transmitted by the terminal is an aggregation frame, Block
In the Ack start sequence control subfield, the first MSDU (medium access control control) of the delivery acknowledgment indicated by the BlockAck frame is displayed.
(MAC) service data unit) sequence number is stored. The Block Acck bitmap subfield is a bitmap (Block) consisting of bits for success or failure of reception of each sequence number after the Block Acck start sequence number.
Ack bitmap) should be inserted.

(UL-MU-MIMO)
UL-MU-MIMO aims to improve the efficiency of uplink transmission by transmitting a frame to a base station (spatial multiplex transmission) by a plurality of terminals at the same timing and in the same frequency band. FIG. 19 is a diagram for explaining the concept of MU-MIMO. It is assumed that the base station performs UL-MU-MIMO with four terminals 1 to 4 (denoted as STA 1 to 4 in the figure). Terminals 1 to 4 transmit frames at the same time using the same channel (20 MHz, 40 MHz, 80 MHz, etc., which may have any bandwidth). The base station receives these frames at the same time, but can separate these frames by using the preamble signal included in the physical header of each frame. This will be described in detail below.

The base station receives the frames of the terminals transmitted by UL-MU-MIMO as a signal in which the frames of each terminal are simultaneously superimposed. In UL-MU-MIMO, the base station needs to spatially separate the frame of each terminal from the signals received from a plurality of terminals at the same time. For this purpose, the base station utilizes the uplink propagation path response with each of the plurality of terminals. The base station can estimate the uplink propagation path response of each terminal by using the preamble signal added to the head side of the frame transmitted by the plurality of terminals. This preamble signal is specifically included in the field for the preamble signal in the physical header arranged at the beginning of the frame.

FIG. 20 shows an example of the configuration of a physical packet including a frame transmitted by terminals 1 to 4. As shown in FIG. 20, the preamble signal is arranged, for example, in the field for the preamble signal between the L-SIG field and the frame. The preamble signals 1 to 4 of the terminals 1 to 4 are orthogonal to each other. The L-STF (Legacy-Short Training Field), L-LTF (Legacy-Long Training Field), L-SIG (Legacy Signal Field) and the like arranged before the preamble signals 1 to 4 are, for example, 1AE. It is a field that can be recognized by terminals of legacy standards such as, and stores information such as signal detection, frequency correction (propagation path estimation), and transmission speed, respectively. L-STF, L-LTF, and L-SIG are the same signals at a plurality of terminals that transmit UL-MU-MIMO. The above-mentioned purinable signal corresponds to an example of the resource according to the present embodiment. Hereinafter, the preamble signal will be described.

The preamble signal is composed of a known bit string or a known symbol string. The base station can correctly spatially separate (decode) the fields after the preamble signal by estimating the propagation path response of the uplink using the known bit string. This can be done using any known method, such as the ZF (Zero-Forcing) method, the MMSE (Mini-Mean Square Error) method, or the maximum likelihood estimation method. As an example, the preamble signal is arranged in the physical header (PHY header) arranged at the head side of the MAC frame. Since the same signal is transmitted from each terminal in the field before the preamble signal in the physical header, the base station can decode even if these signals are received at the same time. On the other hand, the preamble signals of each terminal are orthogonal to each other. Therefore, the base station can individually identify the preamble signals received from each terminal at the same time. As a result, the base station can estimate the propagation path of the uplink from each terminal to the base station by using the preamble signal for each terminal. After the preamble signal, separate signals are sent for each terminal, but these signals can be separated using the estimated propagation path response.

As a method of orthogonalizing the preamble signal between terminals, any of temporal, frequency and code methods can be used. In the case of time orthogonality, the field for the preamble signal is divided into a plurality of sections, and the preamble signal of each terminal is transmitted in different sections. In a certain section, only one of the terminals transmits a preamble signal. That is, while one terminal transmits a preamble signal, another terminal does not transmit anything. In the case of frequency orthogonality, each terminal transmits a preamble signal at frequencies that are orthogonal to each other. In the case of sign orthogonality, each terminal transmits a signal in which value columns contained in different rows (or different columns) of the orthogonal matrix are arranged. Each row (or each column) of the orthogonal matrix is orthogonal to each other. With either method of orthogonalization, the base station can identify the preamble signal of each terminal.

In order for each terminal to use preamble signals that are orthogonal to each other, the base station needs to provide information on the preamble signal used by each terminal and its transmission method. This information corresponds to the resources used in UL-MU-MIMO. Specifically, in the case of time orthogonality, the preamble signal (the preamble signal may be the same or different between terminals) is transmitted at what timing, and in the case of frequency orthogonality, at which frequency, respectively. The preamble signal (the preamble signal may be the same or different between terminals) is transmitted, or in the case of sign orthogonality, which coding pattern (which row or column pattern of the orthogonal matrix) is used to preamble the signal. Or information (resource information) is required.

(OFDMA)
OFDMA allocates a resource unit including one or a plurality of subcarriers to terminals, and simultaneously transmits and receives between the base station and a plurality of terminals on a resource unit basis. A resource unit is a frequency component that is the smallest unit of a resource for communication.

FIG. 21 shows resource units (RU # 1, RU # 2, ... RU # K) secured in a continuous frequency domain of one channel (described here as channel M). A plurality of subcarriers orthogonal to each other are arranged in the channel M, and a plurality of resource units including one or a plurality of subcarriers are defined in the channel M. One or more subcarriers (guard subcarriers) may be arranged between resource units, but guard subcarriers are not essential. Identification information for identifying the resource unit or subcarrier may be set for each resource unit or each subcarrier in the channel. The bandwidth of one channel is, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, and the like, but is not limited thereto. A plurality of 20 MHz channels may be combined into one channel. The number of subcarriers or resource units in the channel may vary depending on the bandwidth. OFDMA communication is realized when a plurality of terminals use different resource units at the same time.

The bandwidth (or the number of subcarriers) of the resource unit may be common to each resource unit, or the bandwidth (or the number of subcarriers) may be different for each resource unit. FIG. 22 schematically shows an example of an arrangement pattern of resource units in one channel. The horizontal direction corresponds to the frequency domain direction along the paper surface. FIG. 22A shows an example in which a plurality of resource units (RU # 1, RU # 2, ... RU # K) having the same bandwidth are arranged.
FIG. 22B shows an example in which a plurality of resource units (RU # 11-1, RU # 11-2, ..., RU # 11-L) having a bandwidth larger than that of FIG. 22A are arranged. .. FIG. 22C shows an example in which resource units having three or more types of bandwidths are arranged. The resource unit (RU # 12-1, RU # 12-2) has the largest bandwidth, and the resource unit RU # 11- (L-1) has the same bandwidth and resources as the resource unit shown in FIG. 22 (B). The units (RU # K-1, RU # K) have the same bandwidth as the resource unit of FIG. 22 (A).

As an example, when the entire 20 MHz channel width is used, 26 resource units can be set for 256 subcarriers (tones) arranged within the 20 MHz channel width. That is, nine resource units are set in the 20 MHz channel width, and the bandwidth of the resource unit is smaller than the 2.5 MHz width. In the 40 MHz channel width, as an example, 18 resource units are set. In the 80 MHz channel width, as an example, 37 resource units are set. If this is developed, for example, in a 160 MHz channel width or an 80 + 80 MHz channel width, 74 resource units are set. Of course, the width of the resource unit is not limited to a specific value, and resource units of various sizes can be arranged.

The number of resource units used by each terminal is not limited to a specific value, and one or more resource units may be used. When the terminal uses a plurality of resource units, a plurality of resource units that are continuous in frequency may be bonded and used as one resource unit, or a plurality of resource units located at different locations may be allowed to be used. May be good. The resource unit # 11-1 of FIG. 22 (B) may be considered as an example of the resource unit in which the resource units # 1 and # 2 of FIG. 22 (A) are bonded.

The subcarriers in one resource unit may be continuous in the frequency domain, or the resource unit may be defined from a plurality of subcarriers arranged discontinuously. The number of channels used in OFDMA is not limited to one, and in addition to channel M, another channel (see channel N in FIG. 21) arranged at a distance in the frequency domain may be similarly used as channel M. The resource unit may be secured and the resource unit in both the channel M and the channel N may be used. The method of arranging the resource units may be the same or different between the channel M and the channel N. As an example, the bandwidth of one channel is, but is not limited to, 20 MHz, 40 MHz, 80 MHz, 160 MHz, etc., as described above. It is also possible to use three or more channels. It is also possible to consider channel M and channel N together as one channel.

Career Sense is the physical carrier of CCA (Clear Channel Assistance) regarding busy / idle.
Both Sense) and a virtual carrier sense based on the media reservation time described in the received frame may be included. The carrier sense information based on CCA or NAV performed for each channel may be applied to all resource units in the channel in common. For example, all resource units belonging to a channel whose carrier sense information indicates an idle may be determined to be idle.

In addition to the resource unit-based OFDMA described above, OFDMA can also be channel-based OFDMA. The OFDMA in this case may be particularly referred to as MU-MC (Multi-User Multi-Channel). In MU-MC, a access point allocates a plurality of channels (one channel width is, for example, 20 MHz) to a plurality of terminals, and the plurality of channels are used simultaneously to simultaneously transmit to or receive from a plurality of terminals. Do.

(Second Embodiment)
FIG. 23 is a functional block diagram of the base station (access point) 400 according to the second embodiment. This access point includes a communication processing unit 401, a transmitting unit 402, a receiving unit 403, antennas 42A, 42B, 42C, 42D, a network processing unit 404, a wired I / F 405, and a memory 406. .. The access point 400 is connected to the server 407 via a wired I / F 405. The communication processing unit 401 has the same functions as the MAC processing unit 10 and the MAC / PHY management unit 60 described in the first embodiment.
The transmitting unit 402 and the receiving unit 403 have the same functions as the PHY processing unit 50 and the analog processing unit 70 described in the first embodiment. The network processing unit 404 has the same function as the higher-level processing unit 90 described in the first embodiment. Here, the communication processing unit 401 may internally hold a buffer for transferring data to and from the network processing unit 404. This buffer may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The network processing unit 404 controls data exchange with the communication processing unit 401, data writing / reading with the memory 406, and communication with the server 407 via the wired I / F 405. The network processing unit 404 may perform communication processing higher than the MAC layer and processing of the application layer such as TCP / IP and UDP / IP. The operation of the network processing unit may be performed by processing software (program) by a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware.

As an example, the communication processing unit 401 corresponds to a baseband integrated circuit, and the transmitting unit 402 and the receiving unit 403 correspond to an RF integrated circuit that transmits and receives frames. The communication processing unit 401 and the network processing unit 404 may be configured by one integrated circuit (one chip). The digital region processing portion and the analog region processing portion of the transmission unit 402 and the reception unit 403 may be composed of different chips. Further, the communication processing unit 401 may execute communication processing higher than the MAC layer such as TCP / IP and UDP / IP. Further, although the number of antennas is four here, it is sufficient that at least one antenna is provided.

The memory 406 stores the data received from the server 407 and the data received by the receiving unit 403. The memory 406 may be, for example, a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM. Further, it may be SSD, HDD, SD card, eMMC or the like. The memory 406 may be outside the base station 400.

The wired I / F 405 sends and receives data to and from the server 407. In the present embodiment, the communication with the server 407 is performed by wire, but the communication with the server 407 may be performed wirelessly. In this case, a wireless I / F may be used instead of the wired I / F 405.

The server 407 is a communication device that receives a data transfer request requesting data transmission and returns a response including the requested data, and is assumed to be, for example, an HTTP server (Web server), an FTP server, or the like. However, it is not limited to this as long as it has a function of returning the requested data. It may be a communication device operated by a user such as a PC or a smartphone.

When the STA belonging to the BSS of the base station 400 issues a data transfer request to the server 407, a packet related to the data transfer request is transmitted to the base station 400. The base station 400 receives this packet via the antennas 42A to 42D, and the receiving unit 403 executes the physical layer processing and the like, and the communication processing unit 401 executes the MAC layer processing and the like.

The network processing unit 404 analyzes the packet received from the communication processing unit 401.
Specifically, the destination IP address, destination port number, and the like are confirmed. When the data of the packet is a data transfer request such as an HTTP GET request, the network processing unit 404 determines that the data requested by this data transfer request (for example, the data existing in the URL requested by the HTTP GET request) is Check if it is cached in memory 406. The memory 406 stores a table in which a URL (or its reduced representation, for example, a hash value or an alternative identifier) is associated with data. Here, the fact that the data is cached in the memory 406 is expressed as the existence of the cached data in the memory 406.

When the cache data does not exist in the memory 406, the network processing unit 404 transmits a data transfer request to the server 407 via the wired I / F 405. That is, the network processing unit 404 transmits a data transfer request to the server 407 on behalf of the STA. Specifically, the network processing unit 404 generates an HTTP request, performs protocol processing such as adding a TCP / IP header, and passes the packet to the wired I / F 405.
The wired I / F 405 transmits the received packet to the server 407.

The wired I / F 405 receives a packet from the server 407 that is a response to the data transfer request. The network processing unit 404 grasps that the packet is addressed to the STA from the IP header of the packet received via the wired I / F 405, and passes the packet to the communication processing unit 401. The communication processing unit 401 executes the processing of the MAC layer for this packet, the transmitting unit 402 executes the processing of the physical layer, etc., and transmits the packet addressed to the STA from the antennas 42A to 42D.
Here, the network processing unit 404 associates the data received from the server 407 with the URL (or its reduced representation) and stores it in the memory 406 as cache data.

When the cache data exists in the memory 406, the network processing unit 404 reads the data requested by the data transfer request from the memory 406 and transmits this data to the communication processing unit 401. Specifically, an HTTP header or the like is added to the data read from the memory 406, protocol processing such as addition of a TCP / IP header is performed, and a packet is transmitted to the communication processing unit 401. At this time, as an example, the source IP address of the packet is set to the same IP address as the server, and the source port number is also set to the same port number as the server (the destination port number of the packet transmitted by the communication terminal). Therefore, from the viewpoint of STA, it looks as if it is communicating with the server 407. The communication processing unit 401 executes the processing of the MAC layer for this packet, the transmitting unit 402 executes the processing of the physical layer, etc., and transmits the packet addressed to the STA from the antennas 42A to 42D.

By such an operation, the frequently accessed data responds based on the cache data stored in the memory 406, and the traffic between the server 407 and the base station 400 can be reduced. The operation of the network processing unit 404 is not limited to the operation of the present embodiment. Any general cache proxy that fetches data from server 407 instead of STA, caches the data in memory 406, and responds to data transfer requests for the same data from the cached data in memory 406. For example, there is no problem with another operation.

Although the base station having a cache function has been described in the present embodiment, a terminal (STA) having a cache function can be realized with the same block configuration as in FIG. 23. In this case, the wired I / F 405 may be omitted.

(Third Embodiment)
FIG. 24 shows an example of the overall configuration of a terminal or a base station. This configuration example is an example, and the present embodiment is not limited thereto. The terminal or base station includes one or more antennas 1 to n (n is an integer of 1 or more), a wireless LAN module 148, and a host system 149. The wireless LAN module 148 corresponds to the wireless communication device according to the first embodiment. The wireless LAN module 148 includes a host interface, which is connected to the host system 149. In addition to being connected to the host system 149 via a connection cable, it may be directly connected to the host system 149. Further, the wireless LAN module 148 can be mounted on the board by solder or the like and connected to the host system 149 via the wiring of the board. The host system 149 communicates with an external device by using the wireless LAN module 148 and the antennas 1 to n according to an arbitrary communication protocol. The communication protocol may include TCP / IP and a higher layer protocol. Alternatively, TCP / IP may be mounted on the wireless LAN module 148, and the host system 149 may execute only the protocol of the upper layer. In this case, the configuration of the host system 149 can be simplified. This terminal is, for example, a mobile terminal, 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 It may be an adapter, a set-top box, a gateway, a printer server, a mobile access point, a router, an enterprise / service provider access point, a portable device, a handheld device, or the like.

FIG. 25 shows a hardware configuration example of the wireless LAN module. This configuration is applicable when the wireless communication device is mounted on either a non-base station terminal or a base station. That is, it can be applied as an example of a specific configuration of the wireless communication device shown in FIG. In this configuration example, at least one antenna 247 is provided. When a plurality of antennas are provided, a plurality of sets of a transmission system (216, 222-225), a reception system (232-235), a PLL 242, a crystal oscillator (reference signal source) 243, and a switch 245 are arranged corresponding to each antenna. Each set may be connected to the control circuit 212. The PLL 242, the crystal oscillator 243, or both correspond to the oscillator according to this embodiment.

The wireless LAN module (wireless communication device) is a baseband IC (Integrated).
It includes a Circuit) 211, an RF (Radio Frequency) IC 221 and a balun 225, a switch 245, and an antenna 247.

The baseband IC 211 includes a baseband circuit (control circuit) 212, a memory 213, a host interface 214, a CPU 215, a DAC (Digital to Analog Converter) 216, and an ADC (Analog to Digital Converter) 217.

The baseband IC211 and RF IC221 may be formed on the same substrate. Further, the baseband IC211 and the RF IC221 may be composed of one chip. DAC216 and / or ADC217 may be located in the RF IC 221 or in another IC. Further, the memory 213 and / or the CPU 215 may be arranged in an IC different from the baseband IC.

The memory 213 stores data to be transferred to and from the host system. Further, the memory 213 stores information notified to the terminal or the base station, information notified from the terminal or the base station, or both of them. Further, the memory 213 may store a program necessary for executing the CPU 215 and may be used as a work area when the CPU 215 executes the program. The memory 213 may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM.

The host interface 214 is an interface for connecting to the host system. The interface may be anything such as UART, SPI, SDIO, USB, PCI Express and the like.

The CPU 215 is a processor that controls the baseband circuit 212 by executing a program. The baseband circuit 212 mainly processes the MAC layer and the physical layer. The baseband circuit 212, CPU 215, or both correspond to a communication control device that controls communication, or a control unit that controls communication.

At least one of the baseband circuit 212 and the CPU 215 includes a clock generation unit that generates a clock, and the internal time may be managed by the clock generated by the clock generation unit.

The baseband circuit 212 performs addition, coding, encryption, modulation processing, etc. of a physical header on the frame to be transmitted as processing of the physical layer, for example, two types of digital baseband signals (hereinafter, digital I signal and digital Q). Signal) is generated.

The DAC 216 DA-converts the signal input from the baseband circuit 212. More specifically, the DAC 216 converts the digital I signal into an analog I signal and the digital Q signal into an analog Q signal. It should be noted that there may be a case where the signal of one system is transmitted as it is without quadrature modulation. When a plurality of antennas are provided and transmission signals of one system or a plurality of systems are distributed and transmitted by the number of antennas, a number of DACs or the like corresponding to the number of antennas may be provided.

The RF IC 221 is, for example, an RF analog IC, a high frequency IC, or both of them. The RF IC 221 includes a filter 222, a mixer 223, a preamplifier (PA) 224, a PLL (Phase Locked Loop) 242, a low noise amplifier (LNA), a balun 235, a mixer 233, and a filter 232.
Some of these elements may be located on baseband IC211 or another IC. The filters 222 and 232 may be a band pass filter or a low pass filter. The RF IC 221 is coupled to the antenna 247 via a switch 245.

The filter 222 extracts a signal in a desired band from each of the analog I signal and the analog Q signal input from the DAC 216. The PLL 242 uses the oscillation signal input from the crystal oscillator 243, and divides or multiplies the oscillation signal, or both, to generate a signal having a constant frequency synchronized with the phase of the input signal. The PLL 242 includes a VCO (Voltage Controlled Oscillator), and obtains a signal having a constant frequency by performing feedback control using the VCO based on an oscillation signal input from the crystal oscillator 243. The generated constant frequency signal is input to the mixer 223 and the mixer 233. The PLL 242 corresponds to an example of an oscillator that generates a signal having a constant frequency.

The mixer 223 up-converts the analog I signal and the analog Q signal that have passed through the filter 222 to a radio frequency by using a signal having a constant frequency supplied from the PLL 242. The preamplifier (PA) amplifies the radio frequency analog I and Q signals generated by the mixer 223 to the desired output power. The balun 225 is a converter for converting a balanced signal (differential signal) into an unbalanced signal (single-ended signal). The RF IC 221 handles balanced signals, but since the unbalanced signals are handled from the output of the RF IC 221 to the antenna 247, the balun 225 performs these signal conversions.

The switch 245 is connected to the transmitting side balun 225 at the time of transmission, and is connected to the receiving side balun 234 or RF IC 221 at the time of receiving. The control of the switch 245 may be performed by the baseband IC211 or the RF IC221, or another circuit for controlling the switch 245 may exist and the switch 245 may be controlled from the circuit.

The radio frequency analog I signal and analog Q signal amplified by the preamplifier 224 are balanced-unbalanced converted by the balun 225, and then radiated as radio waves from the antenna 247 into space.

The antenna 247 may be a chip antenna, an antenna formed by wiring on a printed circuit board, or an antenna formed by using a linear conductor element.

The LNA 234 in the RF IC 221 amplifies the signal received from the antenna 247 via the switch 245 to a level that can be demodulated while keeping noise low. The balun 235 performs an unbalanced-balanced conversion of the signal amplified by the low noise amplifier (LNA) 234. The mixer 233 down-converts the received signal converted into the balanced signal by the balun 235 to the baseband using the signal of a constant frequency input from the PLL 242. More specifically, the mixer 233 has means for generating carriers that are 90 ° out of phase with each other based on the constant frequency signal input from the PLL 242, and the received signals converted by the balun 235 are 90 ° to each other. It is orthogonally demodulated by the out-of-phase carrier wave to generate an I (In-phase) signal having the same phase as the received signal and a Q (Quad-phase) signal having a phase delayed by 90 °. The filter 232 extracts a signal of a desired frequency component from these I signal and Q signal. The I signal and Q signal extracted by the filter 232 are output from the RF IC 221 after the gain is adjusted.

The ADC 217 in the baseband IC 211 AD-converts the input signal from the RF IC 221. More specifically, the ADC 217 converts the I signal into a digital I signal and the Q signal into a digital Q signal. In some cases, only one system of signals may be received without orthogonal demodulation.

When a plurality of antennas are provided, the number of ADCs may be provided according to the number of antennas. Based on the digital I signal and the digital Q signal, the baseband circuit 212 performs physical layer processing such as demodulation processing, error correction code processing, and physical header processing to obtain a frame. The baseband circuit 212 processes the MAC layer on the frame. If the baseband circuit 212 implements TCP / IP, the baseband circuit 212 can also be configured to perform TCP / IP processing.

(Fourth Embodiment)
26 (A) and 26 (B) are perspective views of the wireless communication terminal according to the fourth embodiment, respectively. The wireless communication terminal of FIG. 26 (A) is a notebook PC 301, and the wireless communication terminal of FIG. 26 (B) is a mobile terminal 321. Each corresponds to a form of 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 above can be used. The wireless communication terminal equipped with the wireless communication device is not limited to a notebook PC or a mobile terminal. For example, TVs, digital cameras, wearable devices, tablets, smartphones, game devices, network storage devices, monitors, digital audio players, web cameras, camcorders, projects, navigation systems, external adapters, internal adapters, set-top boxes, gateways, etc. It can also be installed in printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, and the like.

Further, the wireless communication device mounted on the terminal (including the base station) can also be mounted on the memory card. FIG. 27 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 utilizes the wireless communication device 335 for wireless communication with an external device (wireless communication terminal and / or base station, etc.). Note that in FIG. 27, the description of other elements (for example, memory, etc.) in the memory card 331 is omitted.

(Fifth Embodiment)
A fifth embodiment includes a bus, a processor unit, and an external interface unit in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The processor unit and the external interface unit are connected to the buffer via a bus. Firmware runs in the processor section. By including the firmware in the wireless communication device in this way, 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 control unit according to the present embodiment, or another processor that performs processing related to function expansion or modification of the processing. It is also good. The processor unit on which the firmware operates may be provided by the base station, the wireless communication terminal, or both of them according to the present embodiment. Alternatively, the processor unit may be provided with 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.

(Sixth Embodiment)
The sixth embodiment includes a clock generation unit in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The clock generator generates a clock and outputs the clock from the output terminal to the outside of the wireless communication device. In this way, the clock generated inside the wireless communication device is output to the outside, and the host side is operated by the clock output to the outside, so that the host side and the wireless communication device side can be operated in synchronization with each other. It will be possible.

(7th Embodiment)
In the seventh embodiment, in addition to the configuration of the wireless communication device according to any one of the above-described 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 controls to select the power supply to be supplied to the wireless communication device. By providing the wireless communication device with the power supply in this way, it is possible to perform a power consumption reduction operation in which the power supply is controlled.

(8th Embodiment)
The eighth embodiment includes a SIM card in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The SIM card is connected to, for example, a MAC processing unit 10, a MAC / PHY management unit 60, or a control unit 112 in a wireless communication device. In this way, by providing the SIM card in the wireless communication device, it is possible to easily perform the authentication process.

(9th Embodiment)
The ninth embodiment includes a moving image compression / decompression unit in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The moving image compression / decompression section is connected to the bus. As described above, by providing the moving image compression / decompression unit in the wireless communication device, it is possible to easily transmit the compressed moving image and decompress the received compressed moving image.

(10th Embodiment)
The tenth embodiment includes an LED unit in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The LED unit is connected to, for example, at least one of a MAC processing unit 10, a MAC / PHY management unit 60, a transmission processing circuit 113, a reception processing circuit 114, and a control unit 112. By providing the LED unit in the wireless communication device in this way, it is possible to easily notify the user of the operating state of the wireless communication device.

(11th Embodiment)
The eleventh embodiment includes a vibrator unit in addition to the configuration of the wireless communication device according to any one of the above-described embodiments. The vibrator unit is connected to, for example, at least one of a MAC processing unit 10, a MAC / PHY management unit 60, a transmission processing circuit 113, a reception processing circuit 114, and a control unit 112. By providing the vibrator unit in the wireless communication device in this way, it is possible to easily notify the user of the operating state of the wireless communication device.

(12th Embodiment)
A twelfth embodiment includes a display in addition to the configuration of the wireless communication device (base station wireless communication device, wireless communication terminal wireless communication device, or both) according to any of the above-described embodiments. The display may be connected to the MAC processing unit of the wireless communication device via a bus (not shown). By providing the display in this way and displaying the operating state of the wireless communication device on the display, it is possible to easily notify the user of the operating state of the wireless communication device.

(13th Embodiment)
In this embodiment, [1] a frame type in a wireless communication system, [2] a method of disconnecting a connection between wireless communication devices, [3] an access method of a wireless LAN system, and [4] a frame interval of a wireless LAN will be described.
[1] Frame types in communication systems Generally, as described above, frames handled on a wireless access protocol in a wireless communication system are roughly classified into three frames: a data frame, a management frame, and a control frame. It can be divided into types. These types are usually indicated by a header portion commonly provided between frames. As a display method of the frame type, one field may be capable of distinguishing three types, or a combination of two fields may be used to distinguish between the three types. In the IEEE802.11 standard, the frame type is identified by two fields, Type and Subtype, in the Frame Control field in the frame header part of the MAC frame. The data frame, the management frame, and the control frame are roughly classified in the Type field, and the subtypes in the roughly classified frames, for example, the Beacon frame in the management frame, are identified in the Subtype field.

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

A data frame is a frame that transmits data generated inside a wireless communication device to another wireless communication device after establishing a physical communication link with the other wireless communication device. The data is generated in the upper layer of the present embodiment, and is generated by, for example, a user operation.

The control frame is a frame used for control when transmitting (exchanged) a data frame with another wireless communication device. When the wireless communication device receives a data frame or a management frame, the response frame transmitted to confirm the delivery belongs to the control frame. The response frame is, for example, an ACK frame or a BlockACK frame. The RTS frame and CTS frame are also control frames.

These three types of frames are processed as necessary in the physical layer and transmitted as physical packets via the antenna. In addition, the IEEE802.11 standard (the above-mentioned IEEE Std)
In (including extended standards such as 802.11ac-2013), there is an association process as one of the procedures for establishing a connection, but the Association Request frame and the Association Response frame used in it are the management frames, and the Association Request frame. Since the frame and the Association Response frame are unicast management frames, the receiving wireless communication terminal is requested to transmit the ACK frame which is the response frame, and this ACK frame is the control frame as described above.

[2] Method of disconnecting the connection between wireless communication devices There are an explicit method and an implicit method for disconnecting (releasing) the connection. As an explicit method, one of the wireless communication devices having established a connection transmits a frame for disconnection. In the IEEE802.11 standard, the Delivery frame corresponds to this and is classified as a management frame. Normally, the wireless communication device on the side that transmits the frame that disconnects the connection disconnects the connection when the frame is transmitted, and the wireless communication device that receives the frame that disconnects the connection receives the frame. 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 BSS to be connected. When the wireless communication base station disconnects from a certain wireless communication terminal, for example, if the wireless communication base station has a connection management table that manages the wireless communication terminals that subscribe to its own BSS, the connection management Delete the information related to the wireless communication terminal from the table. For example, when the wireless communication base station assigns an AID to each wireless communication terminal that subscribes to its own BSS in the association process, the retained information associated with the AID of the wireless communication terminal that disconnected the connection is used. May be deleted and the AID may be released so that it can be assigned to another newly subscribed wireless communication terminal.

On the other hand, as an implicit method, frame transmission (transmission of data frame and management frame, or transmission of response frame to the frame transmitted by the own device) is detected from the wireless communication device of the connection partner with which the connection is established for a certain period of time. If not, the connection status is determined to be disconnected. There is such a method because, in the situation where the disconnection of the connection is determined as described above, the communication distance from the wireless communication device to which the connection is made is so large that the wireless signal cannot be received or decoded. This is because it is possible that the wireless link cannot be secured. That is, the reception of the frame that disconnects the connection cannot be expected.

A timer is used as a specific example of determining the disconnection by an implicit method. 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 the retransmission period of the frame is activated until the first timer expires (that is,). If the delivery confirmation response frame to the frame is not received (until the desired retransmission period elapses), retransmission is performed. The first timer is stopped when the 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 wireless communication device of the connection partner still exists (in the communication range) (in other words, whether the wireless link can be secured). At the same time, a second timer (for example, a retransmission timer for the management frame) that limits the retransmission period of the frame is activated. Like the first timer, the second timer retransmits if the delivery confirmation response frame to the frame is not received until the second timer expires, and when the second timer expires, it is determined that the connection has been disconnected. .. 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 wireless communication device of the connection partner, the third timer is activated, and each time a frame is newly received from the wireless communication device of the connection partner, the third timer is stopped and the frame is started again from the initial value. When the third timer expires, a management frame is sent to check whether the wireless communication device of the connection partner still exists (in the communication range) (in other words, whether the wireless link is secured) as described above. At the same time, a second timer (for example, a retransmission timer for the management frame) that limits the retransmission period of the frame is activated. In this case as well, if the delivery confirmation response frame to the frame is not received until the second timer expires, retransmission is performed, and when the second timer expires, it is determined that the connection is disconnected. In this case as well, the 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 device of the connection partner still exists may be different from the management frame in the former case. Further, as the timer for limiting the retransmission of the management frame in the latter case, the same timer as in the former case is used here 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 assumes communication or competition with a plurality of wireless communication devices. In the IEEE802.11 wireless LAN, CSMA / CA (Carrier Sense Multiple Access with Carrier Assistance) is the basis of the access method. In the method of grasping the transmission of a certain wireless communication device and transmitting after a fixed time from the end of the transmission, the transmission is performed simultaneously by a plurality of wireless communication devices that grasp the transmission of the wireless communication device, and as a result, the transmission is performed. , Radio signals collide 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 transmission by a plurality of wireless communication devices grasping the transmission of the wireless communication device is stochastically dispersed. Therefore, if there is only one wireless communication device in which the earliest time is subtracted from the random time, the frame transmission of the wireless communication device is successful, and frame collision can be prevented. Since the acquisition of transmission rights is fair among a plurality of wireless communication devices based on a random value, the method adopting Carrier Availability is said to be a method suitable for sharing a wireless medium among a plurality of wireless communication devices. be able to.

[4] Wireless LAN Frame Interval The frame interval of the IEEE802.11 wireless LAN will be described. The frame intervals used in the IEEE802.11 wireless LAN are distributed codedination function interframe space (DIFS), arbitration interframe space (AIFS), point coordination entence spectence , Reduced interframe space (URIFS) and the like.

The definition of the frame interval is defined as a continuous period in which the carrier sense idle should be confirmed and opened before transmission in the IEEE802.11 wireless LAN, and the exact period from the previous frame is not discussed. Therefore, the definition is followed in the description of the IEEE802.11 wireless LAN system here. In the IEEE802.11 wireless LAN, the time to wait for random access based on CSMA / CA is the sum of the fixed time and the random time, and it can be said that this 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 that competes with other wireless communication devices based on CSMA / CA. DIFS is used when there is no distinction of priority by traffic type, and AIFS is used when priority is provided by traffic type (Traffic Identity).

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

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

RIFS is a frame interval that can be used when a plurality of frames are continuously transmitted to the same wireless communication device in a burst after the access right is once acquired, and while RIFS is used, the transmission partner's wireless communication device can be used. Does not request a response frame for.

Here, FIG. 28 shows an example of frame exchange during a competing period based on random access in the IEEE802.11 wireless LAN.

It is assumed that when a data frame (W_DATA1) transmission request is generated in a certain wireless communication device, the medium is recognized as busy media as a result of carrier sense. In this case, the AIFS for a fixed time is vacated from the time when the carrier sense becomes idle, and then the data frame W_DATA1 is transmitted to the communication partner when a random time (random backoff) is vacated. If, as a result of the carrier sense, it is recognized that the medium is not busy, that is, the medium is idle, a fixed time AIFS is provided from the time when the carrier sense is started, and the data frame W_DATA1 is communicated with the communication partner. Send to.

The random time is a pseudo-random integer derived from a uniform distribution between the content windows (CW) given as an integer from 0, multiplied by the slot time. Here, the CW multiplied by the slot time is called the CW time width.
The initial value of CW is given in CWmin, and each time it is retransmitted, 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 device of the transmission destination of W_DATA1, if the data frame is successfully received and the data frame is a frame requesting the transmission of the response frame, the occupation of the physical packet containing the data frame ends on the wireless medium. A response frame (W_ACK1) is transmitted after SIFS time from the time point. When the wireless communication device that has transmitted W_DATA1 receives W_ACK1, it transmits the next frame (for example, W_DATA2) after SIFS time from the end of occupancy of the physical packet containing W_ACK1 on the wireless medium if it is within the transmission burst time limit. can do.

AIFS, DIFS, PIFS and AIFS are functions of SIFS and slot time, but SIFS and slot time are defined for each physical layer. In addition, parameters such as AIFS, CWmin, and CWmax for which values are set for each access category can be set for each communication group (Basic Service Set (BSS) in the 802.11 wireless LAN), but default values are set. ..

For example, in the standardization of 802.11ac, SIFS is 16 μs and slot time is 9 μs, so that PIFS is 25 μs, DIFS is 34 μs, and the default value of the frame interval of access category BACKGROUND (AC_BK) in AIFS is 79 μs. The default frame spacing of BEST EFFORT (AC_BE) is 43 μs, the default frame spacing of VIDEO (AC_VI) and VOICE (AC_VO) is 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 EIFS is basically the sum of SIFS and DIFS and the time length of the response frame when transmitting at the slowest essential physical rate. In a wireless communication device capable of efficiently taking EIFS, the occupancy time length of the physical packet carrying the response frame to the physical packet that activated EIFS can be estimated, and the sum of SIFS, DIFS, and the estimated time can be used. it can.

The terms used in this embodiment should be broadly interpreted. 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. Depending on the circumstances, the "processor" may refer to an application-specific integrated circuit, a field programmable gate array (FPGA), a programmable logic circuit (PLD), and the like. A "processor" may refer to a combination of processing devices such as multiple microprocessors, a combination of DSPs and microprocessors, and one or more microprocessors that work with a DSP core.

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

The frame described in each embodiment may refer not only to a frame called a frame in the IEEE802.11 standard, but also to a frame called a packet such as a Null Data Packet. When the base station expresses that it transmits or receives a plurality of frames or a plurality of X-th frames, these frames or the X-th frames may be the same (for example, the same type or the same contents) or different. .. Any value can be entered in X depending on the situation. Further, the plurality of frames or the plurality of X-th frames may be transmitted or received at different timings in time as well as those transmitted or received at the same time. Further, when expressing that the first frame, the second frame, etc. are transmitted or received at different time points, the expressions of the first, second, etc. are merely expressions for distinguishing the frames, and these expressions are used. The type and content of the frame does not matter.

The present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

The description of the scope of claims at the time of filing is added below.
[1]
It is equipped with a control unit that changes the value of the first parameter that sets the upper limit of the time that the wireless medium can be occupied according to the history of uplink multi-user transmission or the enabled or disabled state of the capability of uplink multi-user transmission. Wireless communication device.
[2]
The transmitter further includes a transmitter that transmits a first frame containing information according to the occupation time of the radio medium determined according to the first parameter to the radio medium based on the access right acquired based on the carrier sense []. 1] The wireless communication device according to the above.
[3]
A receiver that receives the second frame instructing the uplink multi-user transmission, and
A transmission unit that transmits a third frame in response to the second frame is provided.
The wireless communication device according to [1], wherein the control unit reduces the value of the first parameter when the transmission of the third frame is successful.
[4]
A receiver that receives the second frame instructing the uplink multi-user transmission, and
A transmission unit that transmits a third frame in response to the second frame is provided.
The wireless communication device according to [1], wherein the control unit changes the value of the first parameter based on the number of times the second frame is received and the number of times the third frame is successfully transmitted.
[5]
The wireless communication device according to any one of [1] to [4], wherein the control unit further uses the history of single-user transmission to change the value of the first parameter.
[6]
A receiver that receives the second frame instructing the uplink multi-user transmission, and
A transmission unit that transmits a third frame in response to the second frame is provided.
The transmission unit transmits the fourth frame to the wireless medium based on the access right acquired based on the carrier sense.
The wireless communication device according to [1], wherein the value of the first parameter is changed based on the number of times the third frame is successfully transmitted and the number of times the fourth frame is successfully transmitted.
[7]
The wireless communication device according to any one of [1] to [6], wherein the control unit reduces the value of the first parameter by multiplying the value of the first parameter by a first coefficient.
[8]
The control unit reduces the value of the first parameter by subtracting the value corresponding to the length of the third frame from the value of the first parameter. Any one of [3] and [4]. The wireless communication device described in the section.
[9]
The wireless communication device according to any one of [1] to [8], wherein the value of the first parameter is changed according to the elapsed time from a predetermined time point after the uplink multi-user transmission.
[10]
The wireless communication device according to [9], wherein when a certain time has passed from the predetermined time point, the value of the first parameter is changed to a predetermined value.
[11]
The radio according to any one of [1] to [10], wherein the control unit changes the value of the first parameter to a predetermined value when a predetermined fifth frame is received by the reception unit. Communication device.
[12]
The control unit changes the value of the second parameter regarding the period length for performing carrier sense of the wireless medium according to the history of the uplink multi-user transmission, and determines the period according to the changed second parameter. The wireless communication device according to any one of [1] to [11], which performs the carrier sense during the period.
[13]
A receiver that receives the 7th frame instructing uplink multi-user transmission, and
A transmitter that transmits the 8th frame in response to the 7th frame,
The control unit performs the first carrier sense of the radio medium during the first period in order to acquire the access right to the radio medium for transmitting the eighth frame or the ninth frame, and the first carrier sense is performed. When the 7th frame is received during the carrier sense, the 1st carrier sense is stopped, and after the transmission of the 8th frame, the second to acquire the access right for transmitting the 9th frame. Do a career sense,
When the seventh frame is received during the first carrier sense of the wireless medium, the length of the period for performing the second carrier sense is from the length of the first period to the first period. The wireless communication device according to any one of [1] to [12], which is the length obtained by subtracting the time length of the first carrier sense performed from the start of the 7th frame to the reception of the 7th frame.
[14]
The history of the uplink multi-user transmission includes the presence / absence of execution of the uplink multi-user transmission, the number of executions of the uplink multi-user transmission, the execution result of success or failure of the uplink multi-user transmission, and the uplink multi. The wireless communication device according to any one of [1] to [13], which includes at least one of the elapsed times from user transmission.
[15]
The wireless communication device according to any one of [1] to [14], further comprising at least one antenna.
[16]
A transmitter that transmits the first frame instructing uplink multi-user transmission,
A receiver that receives a plurality of second frames transmitted by the uplink multi-user is provided.
Depending on the history of the uplink multi-user transmission or the enabled or disabled state of the uplink multi-user transmission capability of the at least one source for at least one of the sources of the plurality of second frames. , Determine the value of the first parameter that determines the upper limit of the time that the wireless medium can be occupied.
The transmission unit is a wireless communication device that transmits a third frame including information representing the value of the first parameter.
[17]
The wireless communication device according to [16], further comprising at least one antenna.
[18]
A receiver that receives the first frame instructing uplink multi-user transmission, and
A transmitter that transmits a second frame in response to the first frame,
When the first frame is received during the first carrier sense of the wireless medium during the first period in order to acquire the access right for transmitting the second frame or the third frame. A control unit that stops the first carrier sense and controls to perform the second carrier sense in order to acquire the access right for transmitting the third frame after the transmission of the second frame is provided.
The length of the period of the second carrier sense when the first frame is received during the first carrier sense of the wireless medium is from the length of the first period to the length of the first period. A wireless communication device equal to the length obtained by subtracting the time length of the first carrier sense performed from the start to the reception of the first frame.
[19]
A wireless communication method that changes the value of the first parameter that sets the upper limit of the time that the wireless medium can be occupied according to the history of uplink multi-user transmission or the enabled or disabled state of the capability of uplink multi-user transmission.

1, 2, 3, 4, 5, 6, 7, 8: Wireless communication terminal 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: Upper processing unit 211: Baseband IC
213: Memory 214: Host interface 215: CPU
216: DAC
217: ADC
221: RF IC
222: 232: Filter 223, 233: Mixer 224, 234: Amplifier 225, 235: Balun 242: PLL
243: Crystal oscillator 247: Antenna 245: Switch 148: Wireless LAN module 149: Host system 301: Notebook PC
305, 315, 355: Wireless communication device 321: Mobile terminal 331: Memory card 332: Memory card body 51, 51A to 51C, 61, 68, 69, 70, 71: Trigger frame 52, 53, 55, 62 to 64 , 66: Physical packet 54 including data frame, 65: Multi-STA BA frame (delivery confirmation response frame)
64: BA frame

Claims (14)

It ’s a wireless communication device,
A receiver that receives a first frame instructing the wireless communication device to execute uplink multi-user transmission, and a receiver.
In response to the first frame, a transmission unit that transmits a second frame by the uplink multi-user transmission, and a transmission unit.
With a control unit
The receiving unit receives the third frame including the information for specifying the value to be set in the timer, and receives the third frame.
The receiving unit receives the fourth frame, which is a response frame to the second frame, and receives the fourth frame.
When the control unit receives the fourth frame, if the timer set based on the information is activated, the control unit resets the timer and activates the timer.
Wherein the control unit, the timer times out Then, the wireless communication apparatus to change the value of the first parameter for determining the duration of the carrier sense of the wireless medium. The wireless communication device according to claim 1 , wherein the first parameter is a parameter representing at least one of a minimum value and a maximum value of the contention window. The wireless communication device according to any one of claims 1 to 2 , wherein the third frame is a management frame. The wireless communication device according to claim 3 , wherein the management frame is a beacon frame. The wireless communication device can be set to enable or disable the capability of the uplink multi-user transmission.
When the setting of the capability of the uplink multi-user transmission is invalid, the control unit sets the timer according to the reception of the fourth frame and the first parameter according to the timeout of the timer. The wireless communication device according to any one of claims 1 to 4, wherein a predetermined value is used as the value of the first parameter without changing the value of. The control unit sets the timer in response to the reception of the fourth frame when the setting of the uplink multi-user transmission capability is enabled, and the first one in response to the timeout of the timer. Change the value of the parameter and
As a change of the value of the first parameter, the value of the first parameter is changed from the first value to the second value.
The wireless communication device according to claim 5 , wherein the predetermined value is the second value. It ’s a wireless communication device,
A receiver that receives a first frame instructing the wireless communication device to execute uplink multi-user transmission, and a receiver.
In response to the first frame, a transmission unit that transmits a second frame by the uplink multi-user transmission, and a transmission unit.
With a control unit
The receiving unit receives the third frame, which is a response frame to the second frame, and receives the third frame.
Wherein the control unit receives the third frame Then, when running the timer on the reset, to start the timer, the timer times out Then, the first to determine the duration of the carrier sense wireless media Change the value of the parameter from the first value to the second value,
The receiving unit receives a fourth frame including information for specifying at least one of the first value and the second value.
A wireless communication device in which at least one of the first value and the second value of the first parameter is at least one value specified by the information. The wireless communication device according to claim 7 , wherein the first parameter is a parameter representing at least one of a minimum value and a maximum value of the contention window. The wireless communication device according to any one of claims 7 to 8 , wherein the fourth frame is a management frame. The wireless communication device according to claim 9 , wherein the management frame is a beacon frame. The wireless communication device can be set to enable or disable the capability of the uplink multi-user transmission.
When the setting of the uplink multi-user transmission capability is invalid, the control unit activates the timer in response to the reception of the third frame, and the first parameter in response to the timeout of the timer. The wireless communication device according to any one of claims 7 to 10 , wherein a predetermined value is used as the value of the first parameter without changing the value of. The wireless communication device according to claim 11 , wherein the predetermined value is the second value. A wireless communication method executed by a wireless communication device.
A step of receiving a first frame instructing the wireless communication device to perform uplink multi-user transmission, and
In response to the first frame, the step of transmitting the second frame by the uplink multi-user transmission, and
The step of receiving the third frame containing the information that specifies the value to be set in the timer, and
The step of receiving the fourth frame, which is the response frame for the second frame,
When the fourth frame is received, if the timer set based on the information is activated, it is reset and the timer is activated .
The timer times out Then, the step of changing the value of the first parameter for determining the duration of the carrier sense of the wireless medium,
Wireless communication method equipped with. A wireless communication method executed by a wireless communication device.
A step of receiving a first frame instructing the wireless communication device to perform uplink multi-user transmission, and
In response to the first frame, the step of transmitting the second frame by the uplink multi-user transmission, and
The step of receiving the third frame, which is the response frame for the second frame,
When the third frame is received , if the timer is activated, the step of resetting and then activating the timer is performed.
The timer times out Then, the step of changing the value of the first parameter for determining the duration of the carrier sense of the wireless medium from the first value to a second value,
A step of receiving a fourth frame containing information specifying at least one of the first value and the second value is provided.
A wireless communication method in which at least one of the first value and the second value of the first parameter is at least one value specified by the information.

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