JP6484568B2 - Wireless communication control method, wireless communication apparatus, and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication control method, a wireless communication apparatus, and a wireless communication system, and more particularly to wireless QoS (Quality of Service) guarantee.

  In recent years, the need for small-lot, multi-product production at manufacturing sites is expanding. As a result, the number of manufacturing steps increases, and wireless use such as conveyance of intermediate products and automation of manufacturing machines is expanding to the control field. On the other hand, since the communication infrastructure cannot be expanded each time, coexistence with existing communication is essential.

  In general, a single physical infrastructure accommodates control-related communications with different communication requirements, information-related communications that are general communications targeted at workers' tablets, etc., and monitoring communications that are intermediate between them. In order to do this, a network virtualization technology is necessary that physically shows one thing in a logical manner. To that end, IoT (Internet of Things), a technology that connects various other “things” to the Internet, which is connected to IT-related devices such as personal computers, servers, and printers, provides the “guarantee” necessary for building virtual networks. Wireless communication "is required.

  Here, interference that is a cause of deterioration of SINR (Signal-to-Interference Noise Ratio) that is wireless communication quality includes interference outside the system and interference inside the system. Inter-system interference is uncontrollable, but intra-system interference can be managed in a closed environment assuming that a controlled closed system such as a manufacturing plant can limit the introduction of interference sources. . On the other hand, the interference in the system is interference derived from communication of other terminals. For example, by controlling the communication standard IEEE802.11e, non-QoS communication at the QoS communication timing is avoided and interference of QoS communication is suppressed. It becomes possible to respond.

  Here, the QoS guarantee of IEEE802.11e has a problem that there is no guarantee control for a data request delay.

  Therefore, as background techniques for solving these problems, there are JP-A-2015-103849 (Patent Document 1) and JP-A-2013-131835 (Patent Document 2).

  Patent Document 1 aims to obtain an optimal backoff length that satisfies system requirements and can reduce packet collisions after retransmission. A wireless communication device provided in a wireless network using a CSMA / CA communication procedure is Based on the maximum number of retransmissions per link, the packet arrival rate, the delay time, and the packet length of the transmission data set in advance as a request value, the CW value for each number of retransmissions is calculated, and the packet arrival rate is calculated. It is disclosed that a processor is provided that performs retransmission control of a packet by selecting the smallest number of retransmissions to be satisfied and the CW value at the number of retransmissions as parameters at the time of retransmission.

  Further, Patent Document 2 discloses a highly reliable wireless communication apparatus that enables delay control with respect to a requested delay time even between the same traffic amount and the same data type, and that can complete data transmission more reliably by a timeout time. For the purpose of providing, a wireless communication apparatus performs access control to start transmission after a back-off time based on a random value selected from a contention window width has elapsed after detecting a free state of a channel by carrier sense . The remaining time calculation unit calculates the remaining time from the generation of data to the allowable request delay time. The setting unit sets the contention window width according to the remaining time calculated by the remaining time calculating unit. The setting unit makes the first contention window width set by the first remaining time smaller than the second contention window width set by the second remaining time longer than the first remaining time. This is disclosed.

Japanese Patent Laying-Open No. 2015-103849 JP2013-131835A

  Patent Document 1 selects the minimum number of retransmissions for which the arrival rate within the allowable delay satisfies the requirement, and selects the minimum number of retransmissions for which the arrival rate within the allowable delay satisfies the requirement. Further, Patent Document 2 sets the contention window width according to the remaining time from the generation of data to the allowable request delay time, and the connection attempt frequency increases as the remaining time becomes shorter and reaches within the request delay. The rate is improved.

  However, since Patent Documents 1 and 2 do not consider the degree of congestion, there is a problem that the communication speed of an information system with a long request delay is unnecessarily lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a wireless communication control method, a wireless communication apparatus, and a wireless communication system, which are compatible with delay guarantee of control communication and improvement of communication speed of information communication.

  In order to solve the above-described problems, the present invention is, for example, a wireless communication control method for a wireless communication apparatus used in a wireless communication system that performs CSMA / CA access control. A step of receiving a status; a step of receiving an application type; a step of receiving a request delay time; and calculating a margin time to a request delay time which is a difference between the request delay time and an elapsed time from data generation; , Determining the contention window value based on the application type, the margin time until the request delay time, and the congestion state, and performing access control of the CSMA / CA scheme based on the determined contention window value.

  According to the present invention, it is possible to provide a wireless communication control method, a wireless communication apparatus, and a wireless communication system that are compatible with delay guarantee of control communication and improvement of communication speed of information communication.

1 is a configuration diagram of a wireless communication system in Embodiment 1. FIG. 3 is a functional block diagram on a terminal side in Embodiment 1. FIG. 3 is a functional block diagram on the base station side in Embodiment 1. FIG. 1 is a device configuration diagram on a terminal side in Embodiment 1. FIG. 1 is a device configuration diagram on a base station side in Embodiment 1. FIG. It is an operation | movement flow of the congestion condition reception update of the communication terminal by the side of the terminal in Example 1. FIG. It is an operation | movement flow of CW determination and access control of the communication terminal of the terminal side in Example 1. FIG. It is an example of a function which determines CW from the congestion condition in Example 1, and margin time. 6 is an operation flow of congestion status update and transmission of a communication terminal on the base station side in the first embodiment. 6 is an operation flow of CW determination and access control of a communication terminal on the base station side in the first embodiment. It is an operation | movement flow of CW determination and access control of the communication terminal of the terminal side in Example 2. FIG. 10 is a function example for determining a value of a margin time coefficient α from a congestion state in the second embodiment. It is an example of a function which determines CW value from margin time and coefficient alpha in Example 2. It is the operation flow of CW determination and access control of the communication terminal on the terminal side in the third embodiment. It is an example of the function in Example 3 which determines evaluation value (beta) from a congestion condition, application classification, and margin time. It is an example of a function which determines CW value from evaluation value beta in Example 3.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by this.

  FIG. 1 is a configuration diagram of a wireless communication system in the present embodiment. In FIG. 1, reference numeral 101 denotes a control target device, and reference numeral 102 denotes a communication device that performs control system communication of the control target device 101. Similarly, reference numeral 105 denotes an information terminal, and reference numeral 106 denotes a communication apparatus that performs information communication of the information terminal 105. Further, the center device 104, the control target device 101, and the information terminal 105 perform transmission and reception of information by the communication device 103 that performs communication with the communication devices 102 and 106. That is, in FIG. 1, it is assumed that the control target device 101, for example, an industrial device, is controlled remotely by wireless control from the center device 104, and at the same time, an information terminal such as a PC or a tablet used by an operator. A case where information communication with 105 is performed is assumed.

  Note that the communication devices 102, 103, and 106 may be incorporated in the control target device 101, the center device 104, and the information terminal 105, respectively. Hereinafter, the communication device 103 on the center device 104 side is referred to as a base station side communication device, and the communication devices 102 and 106 on the control target device 101 or the information terminal 105 side are referred to as terminal side communication devices.

  FIG. 2 is a functional block diagram of the terminal side communication apparatus in the present embodiment. In FIG. 2, an encoding unit 201 that encodes data to be transmitted, a modulation unit 202 that modulates encoded data, a demodulation unit 204 that demodulates received data, a decoding unit 205 that decodes demodulated data, and data transmission / reception A transmission / reception unit 203, an application I / F 206 that exchanges data to be transmitted and an application of decrypted data with an application, and a control unit 207 that performs overall control.

  The control unit 207 stores data to be transmitted and information on congestion status, manages margin time, calculates a CW (Contention Window) value for each transmission, and other processes related to control of CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) I do.

  FIG. 3 is a functional block diagram of the communication apparatus on the base station side in the present embodiment. In FIG. 3, an encoding unit 301 that encodes data to be transmitted, a modulation unit 302 that modulates encoded data, a demodulation unit 304 that demodulates received data, a decoding unit 305 that decodes demodulated data, and data transmission / reception A transmission / reception unit 303, a network I / F 306 that exchanges data to be transmitted and decoded data with the network, and a control unit 307 that performs overall control.

  The control unit 307 performs processing related to storage of data to be transmitted and information on congestion status, calculation of congestion status, determination of necessity of notification of congestion status, notification, and other CSMA / CA control.

  FIG. 4 is a device configuration diagram of the communication device on the terminal side in the present embodiment. 4, 210 is a processor, 211 is a data buffer, 212 is a memory, 213 is an application I / F, 214 is a wireless transmission / reception unit, 215 is a storage device, and 220 is a data bus. The communication control operation is executed by the processor 210 according to programs, and these programs are stored in the storage device 215.

  The programs stored in the storage device 215 include a communication control program 216 that performs standard communication control other than data exchange with applications and CW value determination, receives congestion status from the base station, and sets a parameter management table. A congestion status management program 217 to be updated, and a CW value determination program 218 for determining a CW value from information on the application type, delay requirement, congestion status, and elapsed time from queue input stored in the parameter management table 219.

  FIG. 5 is a device configuration diagram of the communication device on the base station side in the present embodiment. In FIG. 5, 310 is a processor, 311 is a data buffer, 312 is a memory, 313 is a network I / F, 314 is a wireless transmission / reception unit, 315 is a storage device, and 320 is a data bus. The communication control operation is executed by the processor 310 according to programs, and these programs are stored in the storage device 315.

  As a program stored in the storage device 315, a communication control program 316 for performing data exchange with a network or standard communication control, a congestion state is calculated, a congestion state is determined, transmission necessity is determined, and congestion is transmitted to a terminal The status management program 317 has a parameter management table 318 for storing information such as a congestion status, a calculation method of the congestion status, and a criterion for determining whether or not to notify the congestion status.

  FIG. 6 is an operation flow of congestion status reception update of the communication terminal on the terminal side in this embodiment. In FIG. 6, it is first determined whether or not the congestion status information is received from the base station in S201, and if it is received in S202, the congestion status is updated.

  FIG. 7 is an operation flow of CW determination and access control of the communication terminal on the terminal side in this embodiment. In FIG. 7, first, in S203, it is determined whether there is transmission data. If there is transmission data, the application type and request delay information are acquired together with the data body in S204. This is determined by, for example, from which buffer the data has been taken out. In S205, a margin time until the requested delay time is calculated. Here, margin time = request delay time−elapsed time from data generation. In S206, the latest congestion status is acquired, and in S207, the CW value is determined from the application type, margin time, and congestion status.

  Thereafter, data transmission is performed under the same control as the standard CSMA / CA control. That is, the presence / absence of transmission of another terminal is confirmed in S208 (Carrier Sense), and if there is no transmission, the back-off time is determined in S209. For the backoff, a random value of 1 to CW is selected. Then, after waiting for the back-off time in S210, transmission is started when there is no transmission from another terminal. Then, in S212, it waits for an ACK response from the application, and if not, determines that a collision has occurred, and returns to S205 as a CW value determination flow again. On the other hand, if there is an ACK reply, the process returns to S203 as the next transmission data processing.

  It should be noted that the congestion status reception update operation of FIG. 6 and the CW determination and data transmission operations of FIG. 7 are independent, and the congestion status reception update operation may be performed during data transmission.

  Further, each application may have a communication queue, and the application type and the request delay time may be determined based on the communication queue in which the transmission packet is stored.

  FIG. 8 shows an example of a function for determining the CW value from the congestion status and the margin time until the request delay time in this embodiment. FIG. 8A shows the case of control communication as the application type, and FIG. 8B shows the case of information communication as the application type.

  In both FIGS. 8A and 8B, the CW value is increased as the margin time until the request delay time increases and as the congestion increases. In other words, the control is performed such that the minimum value and the maximum value of the CW value with respect to the margin time become larger as the congestion becomes larger, and the minimum value and the maximum value of the CW value with respect to the margin time become smaller as the congestion becomes smaller. Further, control is performed so that the minimum value and the maximum value of the CW value for congestion increase as the margin time increases, and the minimum value and the maximum value of the CW value for congestion decrease as the margin time decreases. Further, the CW value is determined such that the larger the congestion state, the larger the CW value for the same margin time.

  Also, compared to control system communication, where the required delay time is generally strict as an application type, for example, the delay time is generally less restrictive because the user only has to wait even if the delay is generally delayed. The CW value in the case of information communication with a large is set large. The information system is a delay guarantee type in which the CW value is low when the congestion state (congestion degree) is low (initially short and long for each collision), and the CW value is increased as the allowance time increases when the congestion state is high. To do. Thereby, for example, in the information system, the communication speed can be improved by controlling the CW value to be small and the waiting time to be shortened when the congestion state is low.

  In FIG. 8, the characteristic is a polygonal line, but it may be a straight line or a quadratic function, and the control system may be independent of the congestion state.

  Further, if the congestion state is equal to or less than a predetermined threshold, the CW value may be determined according to the conventional communication standard IEEE802.11e without considering the congestion state.

  In this way, a CW control method is provided in which CW is determined according to the application type, the margin time until the request delay time, and the congestion status. As a result, it is possible to achieve both the guarantee of the delay of the control system communication and the improvement of the communication speed of the information system communication by the control giving priority to the communication speed while the congestion state is low.

  FIG. 9 is an operational flow of congestion status update and transmission on the base station side in this embodiment. In FIG. 9, first, the congestion state is updated in S301. As an evaluation index of the congestion state, for example, a wireless communication resource usage rate or a carrier sense success rate notified to the terminal is used. Next, in S302, it is determined whether or not the congestion status needs to be transmitted to the terminal side. If necessary, the congestion status is transmitted to the terminal side in S303. For example, it is transmitted when a certain period or congestion state fluctuates by a predetermined threshold or more.

  FIG. 10 is an operation flow of CW determination and access control on the base station side in this embodiment. In FIG. 10, data transmission is performed by the same control as the standard CSMA / CA control. That is, it is determined whether there is transmission data in S304. If there is transmission data in S305, the data is acquired and the number of retransmissions is set to zero. In S306, the CW value is determined according to the number of retransmissions. Then, in S307, the presence / absence of transmission of another terminal is confirmed (Carrier Sense). If there is no transmission, the back-off time is determined in S308. For the backoff, a random value of 1 to CW is selected. If there is no transmission from another terminal after waiting for the back-off time in S309, transmission is started in S310. In step S311, if an ACK reply from the application is not waited, it is determined that a collision has occurred, the number of retransmissions is incremented by 1, and the flow returns to step S306 as a CW value determination flow. On the other hand, if there is an ACK reply, the process returns to S304 as the next transmission data processing.

  Note that the congestion status update and transmission operations in FIG. 9 and the CW determination and data transmission operations in FIG. 10 are independent, and the congestion status update and transmission operations may be performed during data transmission.

  As described above, the present embodiment is a radio communication control method for a radio communication apparatus on a terminal side used in a radio communication system that performs CSMA / CA access control, and includes a step of receiving a congestion status of the radio communication system; A step of receiving an application type, a step of receiving a request delay time, a step of calculating a margin time until a request delay time which is a difference between the request delay time and an elapsed time from data generation, an application type and a request delay There is a step of determining a contention window value based on a margin time to time and a congestion state, and performing access control of the CSMA / CA method based on the determined contention window value.

  A wireless communication control method for a base station-side wireless communication apparatus used in a wireless communication system that performs CSMA / CA access control, the step of updating a congestion state of the wireless communication system, and transmitting the updated congestion state Steps.

  A terminal-side wireless communication apparatus used in a wireless communication system that performs CSMA / CA access control, a transmission / reception unit that transmits / receives data, a congestion state, an application type, and a request delay of the wireless communication system from the transmission / reception unit Receive the time, calculate the allowance time until the request delay time, which is the difference between the request delay time and the elapsed time from data generation, and calculate the contention window value based on the application type, the allowance time until the request delay time and the congestion status And a control unit that performs CSMA / CA access control based on the determined contention window value.

  In addition, a wireless communication device on the base station side used in a wireless communication system that performs access control according to the CSMA / CA scheme, a transmission / reception unit that transmits and receives data, and updates the congestion status of the wireless communication system and updates from the transmission / reception unit The control unit is configured to transmit the congestion state.

  As a result, it is possible to provide a wireless communication control method, a wireless communication apparatus, and a wireless communication system that are compatible with delay guarantee of control communication and improvement of communication speed of information communication.

  In this embodiment, an example will be described in which the CW value is determined by multiplying the margin time by a coefficient corresponding to the congestion state.

  FIG. 11 is an operation flow of CW determination and access control of the communication terminal on the terminal side in this embodiment. In FIG. 11, the steps other than S225 and S226 are the same as those of FIG. In S207 of FIG. 7, the CW value is determined from the application type, margin time, and congestion status. In FIG. 11, the coefficient α is determined from the application type and congestion status in S225. Next, in S226, the CW value is determined from the application type and the margin time × α.

  FIG. 12 is a function example for determining the value of the margin time coefficient α from the congestion state in this embodiment. FIG. 12A shows the case of control communication as the application type, and FIG. 12B shows the case of information communication as the application type.

In both FIGS. 12A and 12B, the coefficient α is set larger as the congestion increases.
In addition, the CW value is set larger in the case of information-related communication in which the required delay time is generally longer than in the case of control-related communication in which the required delay time is generally strict as the application type. In addition, in FIG. 12, although it was set as the characteristic of a broken line, it may be a straight line or a quadratic function.

  FIG. 13 is a function example for determining the CW value from the margin time and the coefficient α in the present embodiment. FIG. 13A shows the case of control communication as the application type, and FIG. 13B shows the case of information communication as the application type. The horizontal axis is the margin time × coefficient α, which is a function that determines the CW value reflecting the function of the coefficient α shown in FIG. Therefore, in both FIGS. 13A and 13B, the larger the margin time × α, the larger the CW value is set. In addition, the CW value is set larger in the case of information-related communication in which the required delay time is generally longer than in the case of control-related communication in which the required delay time is generally strict as the application type.

  The operation flow on the base station side in this embodiment is the same as that in the first embodiment.

  In the present embodiment, the CW value is determined based on the margin time, the coefficient α, and the application type by calculating the coefficient α taking into account the congestion state. Note that the control system communication generally has a strict request delay time and a small request delay time as an application type, and the information system communication generally has a loose request delay time and a large request delay time. Therefore, it can be considered that the margin time is equal to the application type (control communication or information communication). Therefore, if a range with a small margin time is regarded as control-system communication and a large range is information-system communication, it can be controlled by a function of one margin time-CW value.

  In this way, a CW control method is provided in which CW is determined in accordance with the coefficient α taking into account the application type, the margin time until the request delay time, and the congestion state. As a result, it is possible to perform control giving priority to the communication speed while the congestion state is low, and it is possible to achieve both the guarantee of the delay of the control communication and the improvement of the communication speed of the information communication.

  In this embodiment, an example will be described in which the CW value is determined according to an evaluation value obtained from the application type, margin time, and congestion status.

  FIG. 14 is an operation flow of CW determination and access control of the communication terminal on the terminal side in this embodiment. In FIG. 14, the steps other than S245 and S246 are the same as those in FIG. In S207 of FIG. 7, the CW value is determined from the application type, margin time, and congestion status. In FIG. 14, the evaluation value β is determined from the application type, congestion status, and margin time in S245. Next, in S246, a CW value is determined from the evaluation value β.

  FIG. 15 is an example of a function for determining the evaluation value β from the congestion status, application type, and margin time in this embodiment. FIG. 15A shows the case of control communication as the application type, and FIG. 15B shows the case of information communication as the application type.

  In both FIGS. 15A and 15B, the evaluation value β is increased as the margin time to the request delay time is larger and the congestion is larger. In other words, control is performed so that the minimum value and the maximum value of the evaluation value β with respect to the margin time increase as the congestion increases, and the minimum value and the maximum value of the evaluation value β with respect to the margin time decrease as the congestion decreases. To do. Further, control is performed so that the minimum value and the maximum value of the evaluation value β for congestion increase as the margin time increases, and the minimum value and the maximum value of the evaluation value β for congestion decrease as the margin time decreases. .

  Also, the evaluation value β in the case of information-related communication in which the request delay time is generally large is set larger than in the case of control-type communication in which the request delay time is generally strict as the application type. In FIG. 15, the characteristic is a polygonal line, but it may be a straight line or a quadratic function.

  FIG. 16 shows an example of a function for determining the CW value from the evaluation value β in this embodiment. FIG. 16A shows the case of control communication as the application type, and FIG. 16B shows the case of information communication as the application type. The horizontal axis is the evaluation value β, which is a function that determines the CW value reflecting the function of the evaluation value β shown in FIG. Accordingly, in both FIGS. 16A and 16B, the larger the evaluation value β, the larger the CW value is set. In addition, the CW value is set larger in the case of information-related communication in which the required delay time is generally longer than in the case of control-related communication in which the required delay time is generally strict as the application type.

  The operation flow on the base station side in this embodiment is the same as that in the first embodiment.

  In this way, a CW control method is provided in which the CW value is determined from the evaluation value β obtained from the application type, the margin time until the request delay time, and the congestion state. As a result, it is possible to perform control giving priority to the communication speed while the congestion state is low, and it is possible to achieve both the guarantee of delay of control communication and the improvement of the communication speed of information communication.

  Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

101: Control target device, 102, 103, 106: Communication device, 105: Information terminal, 104: Center device, 201, 301: Encoding unit, 202, 302: Modulation unit, 204, 304: Demodulation unit, 205, 305 : Decoding unit, 203, 303: Transmission / reception unit, 206, 213: Application I / F, 207, 307: Control unit, 306: Network I / F, 210, 310: Processor, 211, 311: Data buffer, 212, 312 : Memory, 214, 314: Wireless transmission / reception unit, 215, 315: Storage device, 220, 320: Data bus, 313: Network I / F, 216, 316: Communication control program, 217, 317: Congestion status management program, 218 : CW value determination program, 219, 318: Parameter management table

Claims (8)

A wireless communication control method for a wireless communication apparatus used in a wireless communication system that performs CSMA / CA access control,
Receiving a congestion status of the wireless communication system;
Receiving an application type;
Receiving a request delay time; and
Calculating a margin time to a request delay time which is a difference between the request delay time and an elapsed time from data generation;
Determining a contention window value based on the application type, margin time until the request delay time and the congestion state;
Have a steps for performing access control of CSMA / CA scheme based on contention window value the decision,
The step of determining the contention window value increases the contention window value as the margin time increases, and increases the minimum and maximum values of the contention window value for the margin time as the congestion state increases. The contention window value is determined so as to become a wireless communication control method. The wireless communication control method according to claim 1,
The wireless communication control method, wherein the application type is control communication and information communication. The wireless communication control method according to claim 1,
A wireless communication control method, comprising: determining a contention window value without considering the congestion state if the congestion state is equal to or less than a predetermined threshold value. The wireless communication control method according to claim 1,
The wireless communication control method, wherein the contention window value is determined such that the larger the congestion state, the larger the contention window value with respect to a margin time until the same request delay time. The wireless communication control method according to claim 1,
A wireless communication control method, wherein a communication queue is provided for each application, and the application type and request delay time are determined based on a communication queue in which transmission packets are stored. A wireless communication control method for a wireless communication system in which communication is performed between a base station-side wireless communication device and a terminal-side wireless communication device using CSMA / CA access control,
The base station side wireless communication device is:
Updating the congestion status of the wireless communication system;
Transmitting the updated congestion status; and
The terminal side wireless communication device is:
Receiving the congestion status transmitted from the base station side wireless communication device;
Receiving an application type;
Receiving a request delay time; and
Calculating a margin time to a request delay time which is a difference between the request delay time and an elapsed time from data generation;
Determining a contention window value based on the application type, margin time until the request delay time and the congestion state;
Have a steps for performing access control of CSMA / CA scheme based on contention window value the decision,
The step of determining the contention window value increases the contention window value as the margin time increases, and increases the minimum and maximum values of the contention window value for the margin time as the congestion state increases. The contention window value is determined so as to become a wireless communication control method. A wireless communication apparatus used in a wireless communication system that performs CSMA / CA access control,
A transmission / reception unit for transmitting / receiving data; and
The congestion status, application type, and request delay time of the wireless communication system are received from the transmission / reception unit, and a margin time until the request delay time that is a difference between the request delay time and the elapsed time from data generation is calculated determining a contention window value based classification and allowance time until the required delay time and the congestion status, have a control unit for controlling access CSMA / CA scheme based on contention window value the decision,
The control unit increases the contention window value as the margin time increases, and increases the contention window value so that the minimum value and the maximum value of the contention window value with respect to the margin time increase as the congestion state increases. A wireless communication apparatus that determines a window value . A wireless communication system that communicates between a base station-side wireless communication device and a terminal-side wireless communication device using CSMA / CA access control,
The base station side wireless communication device is:
A base station side transceiver for transmitting and receiving data; and
A base station side control unit for updating the congestion status of the wireless communication system and transmitting the updated congestion status from the base station side transceiver unit,
The terminal side wireless communication device is:
A terminal side transmitting / receiving unit for transmitting and receiving data;
A request which is a difference between the request delay time and the elapsed time since the data generation is received from the terminal side transceiver unit, the congestion status of the wireless communication system, the application type and the request delay time transmitted from the base station side transceiver unit A margin time to a delay time is calculated, a contention window value is determined based on the application type, a margin time to the request delay time, and the congestion status, and a CSMA / CA scheme is based on the determined contention window value have a terminal-side control unit that performs access control,
The terminal-side control unit increases the contention window value as the margin time increases, and increases the minimum and maximum values of the contention window value for the margin time as the congestion state increases. A wireless communication system, wherein a contention window value is determined .

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