WO2022024171A1

WO2022024171A1 - Base station and communication method

Info

Publication number: WO2022024171A1
Application number: PCT/JP2020/028672
Authority: WO
Inventors: 朗岸田; 健悟永田; 保彦井上; 裕介淺井; 泰司鷹取
Original assignee: 日本電信電話株式会社
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2022-02-03
Also published as: JP7476966B2; JPWO2022024171A1

Abstract

This base station (10) comprises: a wireless signal processing unit (102) which receives, from a terminal, information on a measurement result of measuring delay when transmitting a wireless signal; a management unit (103) which analyzes the cause of the delay on the basis of the information on the measurement result; and a control unit (104) which controls, on the basis of a delay factor, an access parameter or access method related to transmission or both the access parameter and the access method.

Description

Base station and communication method

The embodiment relates to a base station and a communication method.

The wireless LAN base station and terminal access the channel using CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) and transmit wireless signals. In CSMA / CA, the base station and the terminal wait for the time specified by the access parameter, and transmit the radio signal after confirming by carrier sense that the channel is not in use by another terminal or the like.

EDCA (Enhanced Distribution Channel Access) is defined as one of the priority control methods in wireless LAN. In EDCA, traffic from the upper layer is classified into four access categories (AC), that is, AC_VO (Voice), AC_VI (Video), AC_BE (Best effort), and AC_BK (Background). Then, in EDCA, CSMA / CA is performed for each access category. In EDCA, the access parameters are assigned so that the transmission of the radio signal is relatively prioritized in the order of AC_VO, AC_VI, AC_BE, AC_BK.

EDCA gives relative priority among traffic. Here, RTA (Real-Time Application) such as control of a network game or an industrial robot may have an absolute delay requirement for each application. Relative priorities among traffic may not always meet the requirements.

The embodiment provides a base station and a communication method that can use an application (RTA) having an absolute requirement for delay.

One aspect of the base station includes a radio signal processing unit, a management unit, and a control unit. The radio signal processing unit receives information on the measurement result of the delay when transmitting the radio signal from the terminal. The management unit analyzes the cause of the delay based on the information of the measurement result. The control unit controls an access parameter or an access method related to transmission, or both the access parameter and the access method, based on the cause of the delay.

According to the embodiment, it is possible to provide a base station and a communication method that can use an application (RTA) having an absolute requirement for delay.

FIG. 1 is a diagram showing a configuration of an example of a communication system according to an embodiment. FIG. 2 is a diagram showing a hardware configuration of an example of a base station. FIG. 3 is a diagram showing a hardware configuration of an example of a terminal. FIG. 4 is a diagram showing processing of the MAC (Media Access Control) layer at the time of communication between the base station and the terminal. FIG. 5 is a functional block diagram of the base station. FIG. 6 is a functional block diagram of the terminal. FIG. 7 is a diagram showing the format of the field for storing the measurement report. FIG. 8 is a diagram for explaining the delay measured by the measuring unit in the embodiment. FIG. 9 is a diagram showing the frame format of the data frame including the measurement report. FIG. 10 is a flowchart showing a transmission process of an example of a terminal. FIG. 11 is a flowchart showing a reception process of the base station. FIG. 12 is a conceptual diagram for explaining an example of adjusting access parameters only within one's own BSS. FIG. 13 is a diagram showing an example of adjusting access parameters for reducing delay in consideration of interference from other BSS. FIG. 14 is a diagram for explaining the delay measured by the measuring unit in the modified example 3.

Hereinafter, embodiments will be described based on the drawings. FIG. 1 is a diagram showing a configuration of an example of a communication system according to an embodiment. The communication system 1 has a base station 10 and a terminal 20. The base station 10 communicates wirelessly with a terminal in a predetermined service area. Although not shown in FIG. 1, communication may be performed between the terminals 20.

FIG. 2 is a diagram showing a hardware configuration of an example of the base station 10. The base station 10 is an access point (AP) for the terminal 20. The base station 10 is not limited to a fixed one, but may be mounted on a mobile body.

The base station 10 has a processor 11, a ROM (ReadOnlyMemory) 12, a RAM (RandomAccessMemory) 13, a wireless module 14, and a routing module 15.

The processor 11 is a processing device that controls the entire base station 10. The processor 11 is, for example, a CPU (Central Processing Unit). The processor 11 is not limited to the CPU. Further, an ASIC (Application Specific IC) or the like may be used instead of the CPU. Further, the number of processors 11 may be two or more instead of one.

ROM 12 is a read-only storage device. The ROM 12 stores firmware and various programs necessary for the operation of the base station 10.

The RAM 13 is a storage device that can be arbitrarily written. The RAM 13 is used as a work area for the processor 11 and temporarily stores the firmware and the like stored in the ROM 12.

The wireless module 14 is a module configured to perform necessary processing for wireless LAN communication. The wireless module 14 constitutes a MAC frame from, for example, data transferred from the processor 11, converts the configured MAC frame into a wireless signal, and transmits the configured MAC frame to the terminal 20. Further, the wireless module 14 receives a wireless signal from the terminal 20, extracts data from the received wireless signal, and transfers the data to, for example, the processor 11.

The routing module 15 is provided for the base station 10 to communicate with, for example, a server (not shown) via a network. The base station 10 does not necessarily have to have the routing module 15. The base station 10 may be configured to access a router provided outside the base station 10 by wireless communication or wired communication and connect to a network via this router.

FIG. 3 is a diagram showing a hardware configuration of an example of the terminal 20. The terminal 20 is a terminal device (station) such as a smartphone. The terminal 20 may be a mobile terminal, a terminal mounted on a mobile body, or a fixed terminal.

The terminal 20 has a processor 21, a ROM 22, a RAM 23, a wireless module 24, a display 25, and a storage 26.

The processor 21 is a processing device that controls the entire terminal 20. The processor 21 is, for example, a CPU. The processor 21 is not limited to the CPU. Further, ASIC or the like may be used instead of the CPU. Further, the number of processors 21 may be two or more instead of one.

ROM 22 is a read-only storage device. The ROM 22 stores the firmware and various programs required for the operation of the terminal 20.

The RAM 23 is a storage device that can be arbitrarily written. The RAM 23 is used as a work area for the processor 21, and temporarily stores the firmware and the like stored in the ROM 22.

The wireless module 24 is a module configured to perform necessary processing for wireless LAN communication. For example, the wireless module 24 configures a MAC frame for wireless communication from the data transferred from the processor 21, converts the configured MAC frame into a wireless signal, and transmits the configured MAC frame to the base station 10. Further, the wireless module 24 receives a wireless signal from the base station 10, extracts data from the received wireless signal, and transfers the data to, for example, the processor 21.

The display 25 is a display device that displays various screens. The display 25 may be a liquid crystal display, an organic EL display, or the like. Further, the display 25 may be provided with a touch panel.

The storage 26 is a storage device such as a hard disk. The storage 26 stores, for example, various applications executed by the processor 21.

FIG. 4 is a diagram showing processing of the MAC (Media Access Control) layer during communication between the base station 10 and the terminal 20. In FIG. 4, both the processing on the transmitting side and the processing on the receiving side are shown. When one of the radio modules of the base station 10 and the terminal 20 performs processing on the transmitting side, the other wireless module performs processing on the receiving side. In the following example, the wireless modules on the transmitting side and the receiving side are described without distinction.

First, the processing on the sending side will be explained. In step S10, the radio module performs A-MSDU aggregation. Specifically, the wireless module combines a plurality of data input from an upper layer such as an application layer to generate an A-MSDU (Aggregate-MAC service data unit).

In step S11, the wireless module assigns a sequence number (SN) to the A-MSDU. The sequence number is a unique number for identifying the A-MSDU.

In step S12, the wireless module fragmentes (divides) the A-MSDU into a plurality of MPDUs (MAC protocol data units).

In step S13, the wireless module encrypts each MPDU and generates an encrypted MPDU.

In step S14, the wireless module adds a MAC header and an error detection code (FCS) to each encrypted MPDU. The error detection code is, for example, a CRC (Cyclic Redundancy Check) code.

In step S15, the wireless module performs A-MPDU aggregation. Specifically, the wireless module combines a plurality of MPDUs to generate an A-MPDU (Aggregate-MAC protocol data unit) as a MAC frame.

After step S15, the wireless module processes the physical layer of the MAC frame. That is, the wireless module performs modulation processing or the like on the MAC frame to generate a wireless signal, and transmits the wireless signal to the base station 10.

Next, the processing on the receiving side will be described. When the radio signal is received, the radio module processes the physical layer to restore the MAC frame from the radio signal. After that, the wireless module processes the MAC layer shown in FIG.

In step S20, the wireless module performs A-MPDU deaggregation. Specifically, the wireless module divides the A-MPDU into MPDU units.

In step S21, the wireless module detects an error. For example, the radio module determines whether or not the reception of the radio signal is successful by CRC. When the reception of the radio signal fails, the radio module may make a retransmission request. At this time, the wireless module may request retransmission in units of MPDU. On the other hand, when the reception of the radio signal is successful, the radio module performs the following processing.

In step S22, the wireless module performs address detection. At this time, the wireless module determines whether or not the sent MPDU is addressed to itself based on the address recorded in the MAC header of each MPDU. When it is not addressed to you, the wireless module does not perform the following processing. When addressed to itself, the wireless module does the following:

In step S23, the wireless module decrypts the encrypted MPDU.

In step S24, the wireless module defragments the MPDU. That is, the wireless module restores the A-MSDU from the plurality of MPDUs.

In step S25, the wireless module performs A-MSDU deaggregation. Specifically, the wireless module restores the A-MSDU to data in MSDU units.

After step S25, the wireless module outputs data to the upper layer of the MAC layer. The upper layer is, for example, an application layer.

FIG. 5 is a functional block diagram of the base station 10. The base station 10 has a data processing unit 101, a radio signal processing unit 102, a management unit 103, and a control unit 104. The data processing unit 101, the radio signal processing unit 102, the management unit 103, and the control unit 104 are realized by, for example, a processor 11 and a radio module 14.

The data processing unit 101 constitutes a MAC frame from, for example, data transferred from a server on the network. Further, the data processing unit 101 restores data from the MAC frame transferred from the radio signal processing unit 102. This data includes a measurement report sent from the terminal 20.

The wireless signal processing unit 102 performs processing for transmitting or receiving a wireless signal. For example, the radio signal processing unit 102 converts the MAC frame configured by the data processing unit 101 into a radio signal, and transmits the radio signal to the terminal 20. Further, the radio signal processing unit 102 receives a radio signal from the terminal 20, extracts a MAC frame from the received radio signal, and transfers the MAC frame to the data processing unit 101.

Here, the wireless signal processing unit 102 may be configured to transmit a wireless signal by, for example, EDCA. In this case, the radio signal processing unit 102 has transmission queues AC_VO, AC_VI, AC_BE, and AC_BK for each access category (AC). The transmission queue AC_VO is a queue for holding a MAC frame categorized in VO (Voice). The transmission queue AC_VI is a queue for holding a MAC frame categorized in VI (Video). The transmission queue AC_BE is a queue for holding a MAC frame categorized in BE (Best effort). The transmission queue AC_BK is a queue for holding a MAC frame categorized in BK (Background). Further, the radio signal processing unit 102 may have a transmission queue AC_LL for holding a MAC frame categorized in the access category LL (Low latency). Access category AC_LL is an access category for RTAs that have absolute delay requirements, such as network games, industrial robot control applications, and the like. The transmit queue AC_LL may have a plurality of transmit queues, each of which corresponds to an acceptable limit delay time.

The radio signal processing unit 102 maps the MAC frame transferred from the data processing unit 101 to any of four or five access categories according to the category of the data recorded in the MAC frame. According to the result of this mapping, the radio signal processing unit 102 inputs the MAC frame to the corresponding transmission queue.

The wireless signal processing unit 102 waits for transmission for a time specified by the access parameter set for each access category while confirming that the wireless signal is not transmitted by another terminal or the like by the carrier sense for each access category. When the channel becomes busy while waiting for transmission, it waits for the specified time count. When a channel is busy, it means that the channel is being used for other transmissions. When the channel is idle while waiting for transmission, the radio signal processing unit 102 takes out a MAC frame from the corresponding transmission queue, converts the MAC frame into a radio signal, and transmits the MAC frame. When a channel is idle, it means that the channel is not being used for other transmissions.

Here, the access parameters may be assigned so that the transmission of the radio signal is prioritized in the order of LL, VO, VI, BE, and BK. Access parameters may include CW _min , CW _max , AIFS, TXOP _Limit . CW _min and CW _max are the maximum value and the minimum value of the contention window (CW), which is the transmission waiting time for avoiding conflict, respectively. The shorter the CW _min and CW _max , the easier it is for the transmit queue to get a transmit opportunity. AIFS (Arbitration Inter Frame Space) is a fixed transmission waiting time set for each access category of the radio signal. The smaller the AIFS, the higher the priority of the send queue. The TXOP _Limit is an upper limit of the transmission opportunity (TXOP), which is the occupied time of the channel. The larger the value of TXOP _Limit , the more radio signals can be transmitted at one transmission opportunity.

The management unit 103 manages the measurement report sent from the terminal 20. For example, the management unit 103 holds the measurement report and analyzes the measurement report at a required timing. The measurement report is a report including information on the delay of transmission of the radio signal in the terminal 20. As will be described in detail later, the delay in transmitting a radio signal is caused by a plurality of delay factors. The measurement report contains information on the measurement results of the delay for each factor of the delay.

The control unit 104 performs the control necessary for transmitting the radio signal according to the delay factor analyzed by the management unit 103. This control includes adjustment of access parameters in the radio signal processing unit 102. The details of the operation of the control unit 104 will be described later.

FIG. 6 is a functional block diagram of the terminal 20. The terminal 20 has a data processing unit 201, a radio signal processing unit 202, and a measurement unit 203. The data processing unit 201, the radio signal processing unit 202, and the measurement unit 203 are realized by, for example, a processor 21 and a radio module 24.

The data processing unit 201 constitutes a MAC frame from, for example, data input from a higher-level application. Further, the data processing unit 201 restores data from the MAC frame transferred from the radio signal processing unit 202. This data is used, for example, by higher level applications. Further, the data processing unit 201 generates a MAC frame including a measurement report that stores the measurement result by the measurement unit 203.

The wireless signal processing unit 202 performs processing for transmitting or receiving a wireless signal. For example, the radio signal processing unit 202 converts the MAC frame configured by the data processing unit 201 into a radio signal, and transmits the radio signal to, for example, the base station 10. Further, the radio signal processing unit 202 receives a radio signal from the base station 10, extracts a MAC frame from the received radio signal, and transfers the MAC frame to the data processing unit 201. Here, the radio signal processing unit 202 may be configured to transmit a radio signal by, for example, EDCA, like the base station 10.

The measuring unit 203 measures the delay of transmission of the radio signal in the terminal 20 for each factor. Then, the measurement unit 203 creates a measurement report including delay information based on the measurement result. FIG. 7 is a diagram showing the format of the field for storing the measurement report. The field in which the measurement report is stored includes a plurality of fields in which the measurement result data for each access category is stored. The field in which the measurement report is stored may include only one field, for example, the field in which the measurement result data of AC_LL is stored. Further, in the field in which the measurement report is stored, the delay measurement result may be stored not for each access category but for each traffic type (TID). The TID is given for each application (session) handled by the terminal 20. The mapping to the access category described above may be performed based on the TID. By storing the measurement result for each TID, the delay distinguished for each application can be measured.

FIG. 8 is a diagram for explaining the delay measured by the measuring unit 203 in the embodiment. Delays measured in embodiments include 1) queuing time T _Q , 2) contention wait time T _W , 3) contention time T _C , 4) retransmission time T _R , and 5) transmission time T _T T. The queuing time T _Q , the contention waiting time T _W , the contention time _TC , the retransmission time T _R , and the transmission time T T T _TX may be measured by a clock (not shown) provided in the terminal 20.

The queuing time T _Q is the time from when the MAC frame is input to the end of the transmission queue to when it comes to the beginning of the transmission queue. A long queuing time T _Q means that, for example, there is a delay due to a large number of MAC frames stored in the transmission queue.

The contention waiting time _TW is a waiting time determined by AIFS for collision avoidance control having a priority control function for wireless transmission between access categories. When the channel becomes busy during the contention wait time _TW , it waits for AIFS again after the channel becomes idle. A long contention wait time _TW means that there is a delay due to another preferentially transmitted access category (which may be that of another BSS).

The contention time T _c is a waiting time for avoiding collision of transmission of a radio signal between a plurality of access categories or between terminals. The contention time T _c is a back-off time randomly determined within a range in which CW _min is the minimum value and CW, which is a value equal to or less _than CW _max , is the maximum value. After the count of the contention time T _c is completed, the radio signal is transmitted. If the channel becomes busy before the count of the contention time T _c is completed, the remaining contention time T _c is counted after the channel becomes idle. That is, the count of the contention time T _c is carried over. Therefore, the long contention time _Tc measured means that there is a delay due to a conflict in the transmission of radio signals between a plurality of access categories, or a delay due to a conflict in the transmission of a radio signal between a plurality of terminals. Means that is occurring.

Retransmission time _TR is an additional time when the radio signal needs to be retransmitted. That is, the retransmission time _TR is the time from when the wireless transmission is transmitted and when it is determined that the retransmission is necessary until the actual retransmission is performed. Here, the retransmission time TR includes an additional contention waiting time TW at the time of retransmission and a _contention time T _c ′ determined by the new _CW . Therefore, a long retransmission time _TR means that there is a delay due to a collision or a transmission error.

The transmission time _TTX is the time from the transmission of the radio signal to the reception of the acknowledgment (ACK) from the base station 10. In FIG. 8, the transmission time _TX is shown as the time from the end of the _{retransmission} time TR to the reception of the ACK. If there is no retransmission, the transmission time _TTX is the time from the end of the contention time Tc to the reception of the ACK.

When transmitting the measurement report to the base station 10, the measurement report may be included in the data frame and transmitted. FIG. 9 is a diagram showing the frame format of the data frame including the measurement report. For example, the measurement report is stored in a new field for storing the measurement report, which is added to the data frame which is the MAC frame containing the data to be transmitted. When transmitting data with a delay requirement, the terminal 20 attaches a measurement report based on the delay measurement result to the data frame. As a result, the delay status can be notified to the base station 10 in relatively real time.

Next, the operation of the communication system 1 will be described. In the following description, it is assumed that the terminal 20 transmits a radio signal and the base station 10 receives the radio signal.

FIG. 10 is a flowchart showing a transmission process of an example of the terminal 20. In step S31, the data processing unit 201 determines whether or not data to be transmitted has been input from an upper layer such as an application layer. When it is determined in step S31 that no data has been input, the process of FIG. 10 ends. When it is determined in step S31 that the data has been input, the process proceeds to step S32.

In step S32, the data processing unit 201 performs the processing of the MAC layer shown in FIG. 4 on the input data to generate a MAC frame. Further, when the measurement report is included in the data frame and transmitted, the data processing unit 201 includes the measurement report created by the measurement unit 203 when the MAC frame is generated. As will be described later, the measurement report may be transmitted to the base station 10 using the management frame, or may be transmitted to the base station 10 using the Action frame. After the MAC frame is generated, the data processing unit 201 outputs the MAC frame to the radio signal processing unit 202. The radio signal processing unit 202 outputs the time when the MAC frame is input to the end of the transmission queue to the measurement unit 203.

In step S33, the radio signal processing unit 202 transmits a radio signal. At this time, the radio signal processing unit 202 waits for transmission during the waiting time defined by the access parameter for each access category while performing carrier sense to determine the channel state. Then, if the channel is not used by another terminal or the like, the radio signal processing unit 202 converts the MAC frame into a radio signal and transmits the radio signal. Further, the radio signal processing unit 202 measures the time when the MAC frame comes to the head of the transmission queue, the end time of the waiting time determined by AIFS, the end time of the backoff time, and the time when the radio signal is transmitted. Output to unit 203.

In step S34, the radio signal processing unit 202 determines whether or not to retransmit. For example, when a retransmission request is made from the base station 10, it is determined that the retransmission is performed. In addition, when ACK is not sent from the base station 10 for a certain period of time, it may be determined to retransmit. Further, when the block ACK is sent from the base station 10, it is determined that the block ACK is to be retransmitted when the information of the MPDU whose reception has failed is included in the block ACK. When it is determined in step S34 that the retransmission is performed, the process proceeds to step S35. When it is determined in step S34 that the retransmission is not performed, the process proceeds to step S36.

In step S35, the radio signal processing unit 202 performs retransmission. Further, the radio signal processing unit 202 outputs the time when the radio signal is retransmitted to the measurement unit 203.

In step S36, the radio signal processing unit 202 outputs the time when the transmission is completed (for example, the ACK in FIG. 8 is received) to the measurement unit 203.

In step S37, the measurement unit 203 creates a measurement report. The queuing time is calculated from the time difference between the time when the MAC frame comes to the beginning of the transmission queue and the time entered at the end of the transmission queue. The contention waiting time is calculated from the time difference between the end time of the waiting time determined by AIFS and the time when the MAC frame comes to the head of the transmission queue. The contention time is calculated from the time difference between the end time of the backoff time and the end time of the waiting time determined by AIFS. The retransmission time is calculated from the time difference between the time when the retransmission is performed and the time when the first radio signal is transmitted. The transmission time is calculated from the time difference between the time when the ACK is received and the time when the transmission of the first radio signal is performed or the time when the retransmission is performed. After calculating the time information regarding these delays, the measurement unit 203 creates a measurement report by associating the measurement results with the access category and the sequence number.

In step S38, the data processing unit 201 stores the measurement report in, for example, the storage 24. After that, the process of FIG. 10 ends. Here, the stored measurement report is included in the MAC frame and transmitted at the next transmission of data of the same access category, for example.

FIG. 11 is a flowchart showing a reception process of the base station 10 including the communication method according to the embodiment. In step S51, the radio signal processing unit 102 determines whether or not the radio signal has been received. When it is determined in step S51 that the radio signal has not been received, the process of FIG. 11 ends. When it is determined in step S51 that the radio signal has been received, the process proceeds to step S52.

In step S52, the radio signal processing unit 102 performs radio signal reception processing. That is, the wireless signal processing unit 102 performs demodulation processing or the like on the wireless signal to take out the MAC frame. The wireless signal processing unit 102 outputs the MAC frame to the data processing unit 101. The data processing unit 101 processes the MAC layer on the MAC frame and restores the data.

In step S53, the data processing unit 101 determines whether or not the reception is successful. Whether or not the reception is successful can be determined by, for example, CRC. When it is determined in step S53 that the reception is successful, the process proceeds to step S54. When it is determined in step S53 that the reception is not successful, the process proceeds to step S55.

In step S54, the radio signal processing unit 102 transmits an ACK. The ACK may be sent using the block ACK. The block ACK is an ACK containing information on the success or failure of reception for each MPDU. After that, the process proceeds to step S56.

In step S55, the radio signal processing unit 102 requests retransmission. Retransmission may be requested using block ACK. After that, the process returns to step S51.

In step S56, the data processing unit 101 outputs data to an upper layer such as an application layer.

In step S57, the data processing unit 101 determines whether or not there is a measurement report. For example, when the measurement report is included in the MAC frame, it is determined that there is a measurement report. In addition, it may be determined that there is a measurement report when the measurement report is sent from the terminal 20 using the management frame. Further, the base station 10 may request a measurement report using the Action frame, and when the measurement report is hesitated in response to this request, it may be determined that there is a measurement report. When it is determined in step S57 that there is a measurement report, the process proceeds to step S58. When it is determined in step S57 that there is no measurement report, the process of FIG. 11 ends.

In step S58, the management unit 103 determines whether or not there is a delay based on the measurement result of the delay included in the measurement report. For example, the management unit 103 determines whether or not the delay of the access category AC_LL is shorter than the threshold value. This threshold value may be, for example, a fixed value. Further, this threshold value may be set according to the result of negotiation with the terminal 20. For example, when transmitting and receiving RTA traffic, the base station 10 inquires of the terminal 20 about the delay requirement in transmitting and receiving RTA traffic. Then, the base station 10 sets the threshold value according to this inquiry. When it is determined in step S58 that there is a delay, the process proceeds to step S59. When it is determined in step S58 that there is no delay, the process of FIG. 11 ends.

In step S59, the management unit 103 analyzes the cause of the delay based on the delay information stored in the measurement report. In the embodiment, the cause of the delay is roughly classified into the one due to the competition and the one due to the retransmission. The delay due to the conflict is the delay when the contention time is long, and means that the delay due to the conflict of transmission of the radio signal between a plurality of access categories or terminals occurs, for example. Further, the delay due to retransmission is a delay when the retransmission time is long, and means that a delay occurs because many retransmissions occur. The management unit 103 compares the difference between the allowable delay time assigned to each of the contention time and the retransmission time and the actual time, and identifies the time having a larger difference as the cause of the delay. If both the actual time of the contention time and the actual time of the retransmission exceed the allowable time, both may be specified as the cause of the delay, and the time with a larger difference may be specified as the main cause of the delay. good.

In step S60, the control unit 104 adjusts the access parameters. The adjustment of access parameters will be described later. After adjusting the access parameters, the control unit 104 notifies the radio signal processing unit 102 of the adjusted access parameters. After that, the process proceeds to step S61.

In step S61, the radio signal processing unit 102 notifies the terminal 20 of the adjusted access parameters. For example, the radio signal processing unit 102 includes the adjusted access parameter in the beacon and broadcasts the signal. Alternatively, it may be individually known by using an action frame or the like. After that, the process of FIG. 11 ends. Upon receiving this notification, the terminal 20 also carries out communication from the next time onward using the adjusted access parameters.

Next, the adjustment of access parameters will be explained. FIG. 12 is a conceptual diagram for explaining an example of adjusting access parameters. FIG. 12 is an example in which the access parameter is adjusted with the terminal 20 in the own BSS without considering the interference by another BSS (Basic Service Set).

In the example of FIG. 12, the access parameters are adjusted based on the default. The default is the initial value of the access parameter. The default is predetermined for each access category, for example.

The horizontal axis of FIG. 12 shows an example of adjusting access parameters for dealing with delays due to conflicts. The adjustment of the access parameter for dealing with the delay due to the conflict is performed sequentially toward the right, for example, each time it is determined that there is a delay. The adjustment of each access parameter may be performed in combination or may be performed while being switched one by one. Further, the order of adjusting the access parameters may be changed.

“LL CW _min small” in FIG. 12 means that the CW _min of the access category AC_LL is made smaller than the default. The amount of decrease in CW _min may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual contention time. By reducing the CW _min of the access category AC_LL, the probability that the transmission queue of the access category AC_LL can obtain a transmission opportunity is relatively increased. As a result, it is expected that the delay due to competition will be reduced.

“Other TXOP _Limit small” in FIG. 12 means that the TXOP _Limit of access categories AC_VO, AC_VI, AC_BE, and AC_BK other than the access category AC_LL, that is, no absolute delay requirement, is made smaller than the default. .. The amount of decrease in TXOP _Limit may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual contention time. By reducing the TXOP _Limit of the other access categories, the time for occupying the channel with one transmission opportunity for the other access categories is shortened. As a result, the waiting time for the transmission queue of the access category AC_LL to obtain the transmission opportunity is shortened. As a result, it is expected that the delay due to competition will be reduced.

“No other TXOP continuation” in FIG. 12 means that the TXOP _Limit of the other access category is set to 0. By setting the TXOP _Limit of the other access categories to 0, the probability that the transmission queue of the access category AC_LL can obtain a transmission opportunity is relatively increased. As a result, it is expected that the delay due to competition will be reduced.

The vertical axis of FIG. 12 shows an example of adjusting access parameters for dealing with delays due to retransmission. The adjustment of the access parameter for dealing with the delay due to retransmission is carried out sequentially upward, for example, each time it is determined that there is a delay. The adjustment of each access parameter may be performed in combination or may be performed while being switched one by one. Further, the order of adjusting the access parameters may be changed.

“LL CW _min large” in FIG. 12 means that the CW _min of the access category AC_LL is made larger than the default. The amount of increase in CW _min may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. By increasing the CW _min of the access category AC_LL, the probability of radio signal collision for the access category AC_LL becomes low. As a result, it is expected that the delay due to retransmission will be reduced.

“Other CW _min large” in FIG. 12 means that the CW _min of other access categories is made larger than the default. The amount of increase in CW _min may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. By increasing the CW _min of the other access categories, the probability of collision between the access category AC_LL and the other access categories becomes low. As a result, it is expected that the delay due to retransmission will be reduced.

“LL CW _max large” in FIG. 12 means that the CW _max of the access category AC_LL is made larger than the default. The amount of increase in CW _max may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. By increasing the CW _max of the access category AC_LL, the probability of collision of radio signals for the access category AC_LL is reduced. As a result, it is expected that the delay due to retransmission will be reduced.

"LL MCS small" in FIG. 12 means to use a high transmission quality MCS (Modulation and Coding Scheme) that can be used in the access category AC_LL. The MCS is an index value representing a set of a modulation method and an error correction coding rate when a radio signal is generated in the radio signal processing unit. When an MCS of the access category AC_LL with a small error correction coding rate and a small one is selected, the transmission success probability of the radio signal is increased. As a result, it is expected that the delay due to retransmission will be reduced.

“LL MCS designation” in FIG. 12 means that the index value of the available MCS of the access category AC_LL is designated as a predetermined value, for example, the minimum value. By designating the index value of the MCS of the access category AC_LL to, for example, the minimum value, the success probability of retransmitting the radio signal for the access category AC_LL is increased. As a result, it is expected that the delay due to retransmission will be reduced.

“LL AIFS small”, “Other, AIFS large”, “Other CW _max large”, and “LL centralized control” in FIG. 12 are effective measures for both delay due to competition and delay due to retransmission. These measures are taken when both the delay due to conflict and the delay due to retransmission are determined to be the cause of the delay. "LL AIFS small", "Other, AIFS large", "Other CW _max large", and "LL centralized control" are carried out in this order, for example. Each correspondence may be carried out in combination, or may be carried out while being switched one by one. In addition, the order of implementation of correspondence may be changed. Further, after taking these measures, the access parameter for the delay due to the above-mentioned conflict or the access parameter for the delay due to the above-mentioned retransmission may be adjusted according to the main cause of the delay. In addition, these measures are retransmitted even if the delay due to the conflict is not resolved even if the access parameter for the delay due to the above-mentioned conflict is adjusted, or even if the access parameter is adjusted for the delay due to the retransmission described above. It may be carried out when the delay due to is not eliminated.

"LL AIFS small" means that the AIFS of the access category AC_LL is made smaller than the default. The amount of decrease in AIFS may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. By reducing the AIFS of the access category AC_LL, the probability that the radio signal for the access category AC_LL is preferentially transmitted increases. As a result, it is expected that the delay due to competition will be reduced for the access category AC_LL. Further, since the radio signal of the access category AC_LL is often transmitted with priority over the radio signals of other access categories, collisions are reduced, and it is expected that the delay due to retransmission is reduced for the access category AC_LL.

"Other AIFS large" means that the AIFS of other access categories is larger than the default. The amount of increase in AIFS may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. By increasing the AIFS of other access categories, the probability that the send queue of access category AC_LL can get a transmission opportunity is relatively increased, so it is expected that the delay due to competition will be reduced for access category AC_LL. Will be done. Further, since the radio signal of the access category AC_LL is often transmitted with priority over the radio signals of other access categories, collisions are reduced, and it is expected that the delay due to retransmission is reduced for the access category AC_LL.

"Other CW _max large" means that the CW _max of other access categories is made larger than the default. The amount of increase in CW _max may be a fixed value, or may be determined according to the magnitude of the delay, that is, the time difference between the allowable time and the actual retransmission time. Increasing the CW _max in the other access categories reduces collisions between the radio signals in the other access categories and the AC_LL radio signals. As a result, it is expected that the delay due to the retransmission of the radio signal of AC_LL will be reduced. Further, by increasing the CW _max of the other access categories, the probability that the transmission queue of the access category AC_LL can obtain the transmission opportunity is relatively increased. As a result, it is expected that the delay due to competition will be reduced for the access category AC_LL.

"LL centralized control" means to carry out centralized control for positively securing transmission opportunities for the access category AC_LL. Additional transmission opportunities for the access category AC_LL can be provided using various centralized controls such as HCCA (HCF Control Chanel Access), TWT (Target Wake Time), CFP (Contention Free Period).

As described above, according to the embodiment, the base station 10 collects the delay information in the transmission of the radio signal from the terminal 20, analyzes the delay factor from the delay information, and responds to the analyzed delay factor. Adjust access parameters. By repeating this until the required delay condition is satisfied, the base station 10 can handle RTA traffic with the absolute delay requirement condition.

[Modification 1]
Hereinafter, a modified example of the embodiment will be described. In the above-described embodiment, the cause of the delay is roughly classified into the one due to the contention and the one due to the retransmission. On the other hand, the cause of the delay may be analyzed in more detail.

For example, when the cause of the delay is the queuing time or the contention waiting time, the delay may be eliminated by increasing the transmission opportunity of the LL as compared with other access categories. Therefore, the control unit 104 can adjust access parameters such as reducing the TXOP _Limit of the access category other than LL, reducing the AIFS of the LL, and increasing the AIFS of the access category other than the LL.

Further, for example, when the cause of the delay is the contention time, the delay may be eliminated by setting the backoff time of the LL shorter than that of other access categories. Therefore, the control unit 104 can adjust access parameters such as reducing the CW _max of the LL and increasing the CW _max of the access category other than the LL.

Further, for example, if the cause of the delay is the retransmission time, the delay may be eliminated by increasing the possibility of successful retransmission. Therefore, the control unit 104 can adjust the access parameters such as increasing the CW _max of the LL and other access categories. Further, the control unit 104 can also make adjustments to reduce the index value of the available MCS.

Further, for example, if the cause of the delay is the transmission time, the control unit 104 can make adjustments to increase the available MCS.

[Modification 2]
Further, in the embodiment, an example in which the access parameter is adjusted with the terminal 20 in the BSS of the base station 10 is shown. Here, depending on the location of the terminal 20, the delay may increase due to the influence of other interference sources such as BSS. By including the information related to such interference in the measurement report and sending it to the base station 10, the base station 10 can adjust the access parameters in consideration of the interference.

For example, the terminal 20 identifies different BSS base stations depending on the BSS Color, and measures the channel occupancy time for each BSS. Here, BSS Color represents the "color" of BSS and is set to be different for each adjacent BSS. The channel occupancy time is, for example, the total time of the queuing time, the contention waiting time, the contention time, the retransmission time, and the transmission time described above. Then, the terminal 20 stores the information of the channel occupancy time for each BSS in the base station 10 together with the BSS Color in the measurement report. The base station 10 acquires the occupancy time of another BSS channel from the BSS Color stored in the measurement report as information on interference from the other BSS. Then, when the occupied time of the channel of another BSS exceeds a predetermined threshold value, the base station 10 adjusts the access parameter for reducing the delay due to the interference from the other BSS.

FIG. 13 is a diagram showing an example of adjustment of access parameters for reducing delay in consideration of interference from other BSS. Here, FIG. 13 shows that "change of link or channel" is added in addition to FIG. Therefore, the description of the same processing as in FIG. 12 will be omitted.

"Changing a link or channel" makes a link used for multi-link communication between a base station 10 and a terminal 20 different from a link used for a multi-link communication between another base station and a terminal 20 or a base. This means that the channel used for communication between the station 10 and the terminal 20 is different from the channel used for communication between the other base station and the terminal 20.

Multi-link communication is to communicate between the base station 10 and the terminal 20 using a plurality of different links. The plurality of links may be different in the unit of the frequency band or may be different in the unit of the channel. When the link is different, the base station 10 may negotiate with the other station so that the link used for the communication of the other station is different from the link used for the communication of the own station while maintaining the link used for the communication of the own station. , While maintaining the link used for the communication of the other station, the link used for the communication of the own station may be negotiated with the other station so as to be different from the other station.

The same applies to the case where the channels are different, and the base station 10 negotiates with the other station so that the channel used for the communication of the other station is different from the own station while maintaining the channel used for the communication of the own station. Alternatively, the channel used for communication of the other station may be maintained, and the channel used for communication of the own station may be negotiated with the other station so as to be different from the other station.

Here, "Other TXOP _Limited small", "Other TXOP continuous", "Other CW _min large", "Other AIFS large", "Other CW _max large", and "LL centralized control" shown by the broken line frame in FIG. Has a relatively low effect of reducing the delay when the delay due to interference is large. Therefore, the processes of "other TXOP _limit small", "other TXOP continuous", "other CW _min large", "other AIFS large", "other CW _max large", and "LL centralized control" may be omitted.

In the modification 2 described above, the access parameters are adjusted in consideration of the magnitude of interference caused by other BSS. This is expected to further optimize access parameters.

[Modification 3]
In the embodiment, the measurement report is transmitted in addition to the original data to be transmitted. On the other hand, the measurement report can also be transmitted to the base station 10 using the Action frame. For example, the base station 10 transmits an Action frame to the terminal 20 with a new field including a status notification request for requesting a measurement report. In response to this, the terminal 20 transmits a measurement report. When returning the measurement report, the terminal 20 can use an Action frame to which a new field for storing the measurement report is added.

The measurement report can also be transmitted to the base station 10 using the management frame. In this case, the terminal 20 periodically transmits a management frame to which a new field for storing the measurement report is added to the base station 10.

In the case where these Action frames are used or the management frame is used, if the MAC frame to be transmitted at the terminal 20 is not stored in the transmission queue, the MAC frame for delay measurement is at the top of the transmission queue. You may enter in. The MAC frame for delay measurement may be transmitted using an access parameter or the like based on the conditions specified by the base station. For example, if the base station wants to measure the delay for a specific TID, it may transmit a MAC frame for delay measurement using the parameters of the access category corresponding to the TID. Here, FIG. 14 is an example in which the Action frame is used, but the same applies when the management frame is used.

[Other variants]
Further, in the above-described embodiment and its modification, the delay is measured at the terminal 20, and the measurement result is transmitted from the terminal 20 to the base station 10. On the other hand, the delay may be measured at the base station 10. In this case, the base station 10 can adjust the access parameters based on the delay measured by itself.

Further, each process according to the above-described embodiment can be stored as a program that can be executed by a processor that is a computer. In addition, it can be stored and distributed in a storage medium of an external storage device such as a magnetic disk, an optical disk, or a semiconductor memory. Then, the processor reads the program stored in the storage medium of the external storage device, and the operation is controlled by the read program, so that the above-mentioned processing can be executed.

The present invention is not limited to the above embodiment, and can be variously modified at the implementation stage without departing from the gist thereof. In addition, each embodiment may be carried out in combination as appropriate, in which case the combined effect can be obtained. Further, the above-described embodiment includes various inventions, and various inventions can be extracted by a combination selected from a plurality of disclosed constituent requirements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, if the problem can be solved and the effect is obtained, the configuration in which the constituent elements are deleted can be extracted as an invention.

1 ... Communication system 10 ... Base station 11 ... Processor 12 ... ROM
13 ... RAM
14 ... Wireless module 15 ... Routing module 20 ... Terminal 21 ... Processor 22 ... ROM
23 ... RAM
24 ... Wireless module 25 ... Display 26 ... Storage 101 ... Data processing unit 102 ... Wireless signal processing unit 103 ... Management unit 104 ... Control unit 201 ... Data processing unit 202 ... Wireless signal processing unit 203 ... Measurement unit

Claims

A wireless signal processing unit that receives information on the measurement result of the delay when transmitting a wireless signal from the terminal, and
A management unit that analyzes the cause of the delay based on the information of the measurement result, and
An access parameter or an access method related to the transmission based on the cause of the delay, or a control unit that controls both the access parameter and the access method.
A base station equipped with.
In the control unit, when the cause of the delay is due to the competition of transmission of the radio signal, the radio signal including the data having the delay requirement is more than the radio signal including the data without the delay requirement. The base station according to claim 1, wherein the access parameter is controlled so as to be transmitted with priority.
The control unit reduces the minimum value of the contention window related to the transmission of the radio signal including the data having the delay requirement, in the transmission opportunity relating to the transmission of the radio signal including the data without the delay requirement. The second aspect of claim 2, wherein the upper limit of the channel occupancy time is reduced, or the number of transmissions at the transmission opportunity related to the transmission of the radio signal including the data without the delay requirement is set to one. The listed base station.
The control unit controls the access parameter so as to increase the success probability of transmission of a radio signal including data with a requirement for delay when the cause of the delay is due to retransmission of the radio signal. The base station described in.
The control unit increases the minimum value of the contention window relating to the transmission of the radio signal including the data having the delay requirement, and the contention window relating to the transmission of the radio signal including the data without the delay requirement. Increasing the minimum value of, increasing the maximum value of the contention window related to the transmission of the radio signal containing the data with the delay requirement, and the modulation related to the transmission of the radio signal containing the data with the delay requirement. Change the index value of the method / coding rate to an index value with higher transmission quality, or set the index value of the modulation method / coding rate related to the transmission of radio signals containing data with the delay requirement to a predetermined value. The base station according to claim 4, wherein at least one of the designations is performed.
The control unit further reduces the AIFS value related to the transmission of the radio signal including the data having the delay requirement, and sets the AIFS value related to the transmission of the radio signal including the data without the delay requirement. The invention according to any one of claims 2 to 5, wherein at least one of increasing the maximum value of the contention window relating to the transmission of the radio signal including the data without the delay requirement is increased. base station.
The base station according to any one of claims 2 to 6, wherein the control unit further performs centralized control on a radio signal including data having a delay requirement condition.
The radio signal processing unit receives information on interference with its own station due to communication between another base station and the terminal from the terminal, and receives information from the terminal.
The base station according to any one of claims 2 to 6, wherein the management unit further analyzes the cause of the delay based on the information of the interference.
The control unit makes the link used for communication with the terminal different from the link used for communication between the other base station and the terminal, or sets the channel used for communication with the terminal with the other base station. The base station according to claim 8, which is different from the channel used for communication with the terminal.
When the base station receives information on the measurement result of the delay when transmitting a radio signal from the terminal,
The base station analyzes the cause of the delay based on the information of the measurement result, and
The base station controls the access parameter or access method related to the transmission, or both the access parameter and the access method, based on the cause of the delay.
A communication method that comprises.