JP6679701B2 - Wireless communication device, wireless communication method, and wireless communication program - Google Patents

Description

  Embodiments of the present invention relate to a wireless communication device, a wireless communication method, and a wireless communication program.

  In a network, protocols are multi-layered by a seven-layer model of an OSI (Open Systems Interconnection) reference model, and a protocol is designed for each layer. There is disclosed a wireless device that determines an allocation order of wireless resources in consideration of upper layer information such as QoS (Quality of Service) required by an application layer based on such a layered protocol design ( See Patent Document 1.). However, when the QoS required by the application layer is high, the delay time of data transmission / reception may not be reduced only by changing the radio resource allocation order when congestion occurs, for example.

JP, 2009-224836, A

  As described above, the technique described in Patent Document 1 has a problem that the delay time of data transmission / reception may not be reduced when the QoS required by the application layer is high. Therefore, an object of the present invention is to provide a wireless communication device, a wireless communication method, and a wireless communication program capable of reducing the delay time of data transmission / reception.

An embodiment of the present invention includes a transmission unit that transmits data, an estimation unit that estimates a retransmission count upper limit value that does not exceed a transmission delay permissible time of the data until completion of retransmission of the data, and the transmission. And a retransmission upper limit number changing unit that changes the upper limit value of the number of retransmissions in the unit to the retransmission number upper limit value estimated by the estimation unit, the estimation unit having a transmission completion time according to the number of transmissions of the data. An estimated value is obtained for each number of times of transmission based on a delay time that varies in each number of times of transmission, and the retransmission number upper limit value is estimated based on the number of times of transmission of the estimated value of the transmission completion time that exceeds the allowable transmission delay time. The estimation unit includes a first number of transmissions that is the number of transmissions of the estimated value of the transmission completion time that exceeds the transmission delay allowable time, and a transmission completion time that is equal to or less than the transmission delay allowable time. Estimates the retransmission count upper limit value based on a second number of transmissions is the number of transmissions of the estimated value, is a wireless communication apparatus according to claim.

  Further, the wireless communication device of one embodiment of the present invention is characterized in that the retransmission count upper limit value is the second transmission count.

Further, an embodiment of the present invention is a transmission procedure for transmitting data, and an estimation procedure for estimating a retransmission count upper limit value in which the time until the retransmission of the data is completed does not exceed the transmission delay allowable time of the data, And a retransmission upper limit number changing procedure of changing the upper limit value of the number of retransmissions in the transmission procedure to the retransmission number upper limit value estimated in the estimation procedure, wherein the estimation procedure is a transmission completion according to the number of transmissions of the data. The estimated value of time is obtained based on the delay time that varies in each transmission times for each of the transmission times, and the retransmission number upper limit value is set based on the transmission times of the estimated value of the transmission completion time that exceeds the transmission delay allowable time. Estimating, wherein the estimating procedure includes a first number of transmissions, which is the number of transmissions of the estimated value of the transmission completion time that exceeds the transmission delay allowable time, and the transmission delay allowable time or less. Wherein estimating the retransmission count upper limit value based on a second number of transmissions wherein a transmission frequency of the estimated value of the transmission completion time that is a wireless communication method characterized by.

According to an embodiment of the present invention, a transmission procedure for transmitting data to a computer included in a wireless communication device, and an upper limit of the number of retransmissions so that a time until the retransmission of the data is completed does not exceed a transmission delay allowable time of the data. A wireless communication program for executing an estimation procedure for estimating a value, and a retransmission upper limit number changing procedure for changing the upper limit value of the number of retransmissions in the transmission procedure to the retransmission number upper limit value estimated in the estimation procedure, The estimation procedure obtains an estimated value of the transmission completion time according to the number of times of transmission of the data based on the delay time that varies in each transmission time for each of the transmission times, and determines the transmission completion time exceeding the transmission delay allowable time. A method of estimating the retransmission number upper limit value based on the number of times of transmission of an estimated value, wherein the estimating procedure includes the time of the completion of the transmission exceeding the allowable transmission delay time. Of the retransmission count upper limit value based on a first transmission count that is the transmission count of the estimated value and a second transmission count that is the transmission count of the estimated transmission completion time that is less than or equal to the transmission delay allowable time. It is a wireless communication program to be estimated.

  According to the present invention, it is possible to provide a wireless communication device, a wireless communication method, and a wireless communication program capable of reducing the delay time of data transmission / reception.

FIG. 1 is a schematic diagram showing an example of an outline of a wireless communication system 1. It is a figure which shows an example of comparison of the retransmission procedure of the wireless communication system of a reference example and the wireless communication system 1 of this embodiment. 6 is a flowchart showing an example of operation of the wireless communication system 1. 6 is a flowchart showing an example of operation of the wireless communication system 1.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In each of the following drawings, constituent elements that are not necessary for explaining the embodiment are omitted from the drawings. Further, the following embodiments are exemplifications, and the present invention is not limited to the contents of the embodiments.

  FIG. 1 is a schematic diagram showing an example of an outline of the wireless communication system 1. The wireless communication system 1 includes a wireless communication device 10 and a wireless communication device 20. However, there may be a plurality of wireless communication devices 10 and 20. In the wireless communication system 1 shown in FIG. 1, the wireless communication device 10 transmits data received from a network to the wireless communication device 20 by wireless communication in units of frames of a predetermined format. Further, when the wireless communication device 20 receives one frame F from the wireless communication device 10, the wireless communication device 20 transmits an acknowledge ACK indicating that the reception is completed to the wireless communication device 10. Here, F represents the frame number.

  The wireless communication device 10 is, for example, a wireless communication device that forms a base station, a router, or the like that transmits video and audio data. Further, the wireless communication device 20 is, for example, a wireless communication device that constitutes a mobile phone terminal, an information processing terminal, or the like that is capable of playing back video and audio contents. Further, in the wireless communication system 1, the protocol is multi-layered by the 7-layer model of the OSI reference model, and the protocol is designed for each layer. In the wireless communication device 20, a reproduction application for moving image or audio content is installed as an application layer of the OSI reference model.

  Further, the data received by the wireless communication device 10 from the network is, for example, streaming data of moving image content. In the following description, as an example, a case where the wireless communication device 10 sequentially receives streaming data of moving image content from the network and transmits the streaming data to the wireless communication device 20 will be described.

  As described above, when the wireless communication device 20 receives the frame F from the wireless communication device 10, the wireless communication device 20 transmits an acknowledge ACK indicating that the reception is completed to the wireless communication device 10. Further, the wireless communication device 20 receives the new frame F and receives the already received frame F-1 or the like (here, the frame F-1 is the frame transmitted from the wireless communication device 10 immediately before the frame F). Is generated). The wireless communication device 20 receives the new frame F for generating the moving image before starting the generation of the moving image, thereby reproducing the continuous moving image content. That is, this frame F is data required to be transmitted and received within a predetermined time. In other words, this data is data for which real-time property is important. Next, an outline of a procedure for transmitting and receiving the frame F by the wireless communication device 10 and the wireless communication device 20 will be described with reference to FIG.

  FIG. 2 is a diagram showing an example of comparison of retransmission procedures between the wireless communication system of the reference example and the wireless communication system 1 shown in FIG. FIG. 2A is a diagram showing an example of a retransmission procedure of a wireless communication system as a reference example for explanation. FIG. 2B is a diagram showing an example of a retransmission procedure of the wireless communication system 1 shown in FIG. The transmitting side is the wireless communication device 10 in the example of the present embodiment. The receiving side is the wireless communication device 20 in the example of the present embodiment. Further, it is assumed that the wireless communication system of the reference example shown in FIG. 2A includes wireless communication devices on the transmitting side and the receiving side corresponding to the wireless communication device 10 and the wireless communication device 20.

  In the wireless communication device 10 shown in FIG. 1, the allowable delay of the frame F is set based on the QoS required by the application layer. Here, the allowable delay is a delay time allowed from the start of the transmission of the frame F by the wireless communication device 10 to the completion of the transmission of the frame F. The completion of the transmission of the frame F means that the wireless communication device 10 receives an acknowledge ACK indicating that the wireless communication device 20 has received the frame F of the frame F transmitted by the wireless communication device 10. . In the following description, this allowable delay is also referred to as a transmission delay allowable time Ta.

  An example of QoS required by this application layer is an access category. This access category includes an access category that emphasizes delay time and an access category that emphasizes throughput. Examples of applications in the access category that emphasize delay time include moving image streaming and VoIP (Voice over Internet Protocol). Further, as an example of an application of an access category in which throughput is emphasized, there is a mail (text) (HTML sentence) written in HTML (Hyper Text Markup Language) in a web page.

  In the wireless communication system 1 shown in FIG. 1, the data transmitted by the wireless communication device 10 is provided with an access category specified in a higher communication protocol layer, and the transmission delay allowable time Ta is set for each access category. Has been defined. When the time from the start of the transmission of the frame F to the reception of the acknowledge ACK for this frame F is the transmission delay allowable time Ta or less, the wireless communication device 10 sets the frame F within the transmission delay allowable time Ta. It is determined that the transmission has been completed.

  Here, there are cases where the wireless communication device 20 cannot receive the frame F transmitted by the wireless communication device 10, such as when a frame loss occurs in the wireless communication path. In this case, the wireless communication device 10 retransmits the frame F. More specifically, the wireless communication device 10 determines whether or not the acknowledge ACK for the frame F is received by the time the acknowledge waiting time Tw elapses after transmitting the frame F. Here, the acknowledge waiting time Tw is a waiting time from when the wireless communication device 10 starts transmitting the frame F until the wireless communication device 10 receives an acknowledge ACK for this frame F. When the wireless communication device 10 receives the acknowledge ACK for the frame F by the time the acknowledge waiting time Tw elapses, the wireless communication device 10 determines that the transmission is completed and does not perform subsequent retransmission. That is, the wireless communication device 10 determines that the transmission is completed when the time from transmitting the frame F to receiving the acknowledge ACK for the frame F is shorter than the acknowledge waiting time Tw. When it is determined that this transmission is completed, the wireless communication device 10 starts transmission of this new frame F + 1 if there is a new frame F + 1 to be sent next. Further, if the wireless communication device 10 does not receive the acknowledge ACK for the frame F before the acknowledge waiting time Tw elapses, the wireless communication device 10 determines that the transmission is not completed, and retransmits the frame F. .

  In the transmission procedure of FIG. 2A, when the frame F is transmitted, the frame F repeats until the number of retransmissions reaches a predetermined upper limit value of the number of retransmissions while it is not determined that the transmission of the frame F is completed. Will be resent. In the example of FIG. 2A, the transmission is completed when the frame F is retransmitted k times, and then the next frame F + 1 is transmitted. In this case, the transmission completion time TM exceeds the transmission delay allowable time Ta. The transmission completion time TM is the time from the start of transmission of the frame F by the transmission side to the reception of the acknowledge ACK for this frame F. In addition, below, the measured value of the transmission completion time TM is also described as the measured value TM of the transmission completion time.

  In the transmission procedure of FIG. 2A, the transmission side does not receive the acknowledge ACK for the frame F (initial transmission) transmitted for the first time before the acknowledge waiting time Tw elapses. As a result, the transmitting side retransmits this frame F (retransmission 1). Further, the transmitting side does not receive the acknowledge ACK for the retransmitted frame F (retransmission 1) until the acknowledge waiting time Tw elapses. As a result, the transmitting side retransmits this frame F (retransmission 2). In the same manner thereafter, the transmitting side repeatedly retransmits the frame F, and for the transmitted frame F (retransmission k) retransmitted at the k-th time, the acknowledge ACK for this frame F is acknowledged before the acknowledge waiting time Tw elapses. To receive. As a result, the transmitting side determines that the transmission of the frame F has been completed and does not perform subsequent retransmission. On the other hand, when the reception of the frame F is not completed even after the transmission delay allowable time Ta has passed, the receiving side uses this unreceived frame F as another frame that has already been received or a predetermined alternative data. And so on. Further, when the receiving side receives the frame F after exceeding the transmission delay allowable time Ta, the receiving side discards the received frame F.

  That is, in the transmission procedure of FIG. 2A, when the transmission of the frame F is not completed, the retransmission of the frame F is repeated until the number of retransmissions of the frame F reaches the upper limit value of the number of retransmissions. In the example shown in FIG. 2A, the upper limit of the number of retransmissions is set to a value larger than k. Then, in this example, the transmission delay allowable time Ta has elapsed when the transmitting side did not receive the acknowledge ACK for the retransmission of the frame F of the e + 1th retransmission. Further, when the acknowledge ACK for the kth retransmission of the frame F after e + 1 times is received, the transmission delay allowable time Ta is naturally passed. That is, the upper limit of the number of retransmissions is larger than the number of times that the frame F can be retransmitted within the transmission delay allowable time Ta. In this way, when the upper limit of the number of retransmissions is larger than the number of times that the frame F can be retransmitted within the transmission delay allowable time Ta, the frame F becomes useless and the transmission of the subsequent frame F + 1 is also delayed.

  On the other hand, in the transmission procedure of FIG. 2B, when the frame F is transmitted, the number of retransmissions reaches the retransmission number upper limit value e estimated by the wireless communication device 10 while it is not determined that the transmission of the frame F is completed. Until frame F is repeatedly retransmitted. In the example of FIG. 2B, when the number of retransmissions of the frame F reaches the retransmission number upper limit value e, the retransmission is stopped, and then the next frame F + 1 is transmitted. In the present embodiment, the retransmission count upper limit value e is estimated such that the transmission completion time TM does not exceed the transmission delay permissible time Ta and the transmission delay permissible time Ta is as close as possible even after e retransmissions. The estimated value is based on the transfer time of frame F, the waiting time between frames, the transfer time of acknowledge ACK, the waiting time of carrier sense, and the like. The retransmission count upper limit value e is a value that changes according to the wireless environment, and the wireless communication device 10 adaptively estimates the retransmission count upper limit value e by measuring the past transmission completion time TM. A method of calculating the retransmission count upper limit value e will be described later.

  As described above, in the transmission procedure shown in FIG. 2B, the transmission side determines that the number of retransmissions n reaches the retransmission number upper limit value e even if the transmission of the frame F is not completed. Will not retransmit any more times. When the number of retransmissions reaches the retransmission count upper limit value e and the transmission side has a new frame F + 1 to be transmitted next, the transmission side starts transmission of this new frame F + 1 from the next transmission. When the reception side does not complete the reception of the frame F even after the transmission delay allowable time Ta has passed, the reception side uses this unreceived frame F as another frame that has already been received or a predetermined alternative data. And so on. Further, when the receiving side receives the frame F after exceeding the transmission delay allowable time Ta, the receiving side discards the received frame F.

  That is, in the wireless communication system 1 of the present invention, the number of retransmissions of the frame F is adjusted so as to be the transmission delay allowable time Ta or less. In the example shown in FIG. 2B, the wireless communication device 10 ends the retransmission of the frame F e times before the transmission delay allowable time Ta elapses. As a result, it is possible to prevent the unnecessary frame F from being retransmitted and to quickly transmit the subsequent frame F + 1.

  As shown in FIG. 2A, when the transmitting side retransmits the frame F after exceeding the transmission delay allowable time Ta, even if the frame F is received by the receiving side, the receiving side will allow the transmission delay. The frame F received after exceeding the time Ta is discarded. Therefore, when the transmitting side retransmits the frame F after exceeding the allowable transmission delay time Ta, a useless frame F that is not used by the receiving side is transmitted. Therefore, the wireless communication device 10 according to the present embodiment estimates the optimum upper limit value of the number of retransmissions e, thereby reducing the number of retransmissions of the unnecessary frame F without excessively reducing the number of retransmissions. Hereinafter, a specific configuration of the wireless communication system 1 will be described.

  Returning to FIG. 1, the wireless communication device 10 of the present embodiment includes a control unit 100 and a storage unit 110. The control unit 100 includes a CPU (Central Processing Unit) and performs various calculations. The storage unit 110 includes a storage device such as a flash memory, an HDD (Hard Disk Drive), a RAM (Random Access Memory), a ROM (Read Only Memory), and a register. A program (firmware) executed by the CPU of the control unit 100 is stored in the storage unit 110 in advance. Further, the storage unit 110 temporarily stores the calculation result of the CPU performing the calculation processing, the data supplied from the network, and the like.

  The control unit 100 includes a time counting unit 101, a transmitting unit 102, an estimating unit 103, a retransmission upper limit number changing unit 104, and a receiving unit 105 as its functional units. Note that, in the following description, the transmitting unit 102 and the receiving unit 105 are described as both functions realized by the CPU of the control unit 100, but the present invention is not limited to this. For example, a part or all of the transmission unit 102 and the reception unit 105 may have a function realized by a wireless module including an LSI (Large Scale Integration) independent of the CPU.

  The timer unit 101 measures the transmission completion time TM. Here, the transmission completion time TM means that the receiving unit 105 receives an acknowledge ACK for the frame F after the first transmission or one or more retransmissions after the transmission unit 102 starts transmitting the frame F. It's time to go.

  The transmitter 102 transmits the frame F. That is, the transmitting unit 102 transmits the data to which the access category designated in the higher communication protocol layer is added, in units of frames according to a predetermined communication protocol. Here, the access category indicates the QoS required by the upper application layer.

  Further, the transmission unit 102 determines whether or not the frame F needs to be retransmitted. Specifically, the transmission unit 102 determines whether or not the reception unit 105 has received an acknowledge ACK for this frame F from the start of transmission of the frame F until the acknowledge waiting time Tw elapses. When the transmitting unit 102 receives the acknowledge ACK for this frame F before the acknowledge waiting time Tw elapses, the transmitting unit 102 determines that the retransmission of the frame F is unnecessary. Also, the transmitting unit 102 determines that the frame F needs to be retransmitted if the receiving unit 105 does not receive the acknowledge ACK for the frame F before the acknowledge waiting time Tw elapses. When it is determined that the frame F needs to be retransmitted, the transmitting unit 102 retransmits the frame F until the upper limit value of the number of retransmissions notified from the retransmission upper limit number changing unit 104 is reached.

  Based on the value of the transmission completion time TM, the estimation unit 103 estimates the retransmission count upper limit value e that is the transmission time closest to the transmission delay allowable time Ta without exceeding the transmission delay allowable time Ta. . The allowable transmission delay time Ta is predetermined for each access category. Specifically, for example, a transmission delay allowable time Ta1 is predetermined in the access category VS, which is an access category for transmitting streaming data of moving image content. In addition, a transmission delay allowable time Ta2 is predetermined in the access category VO, which is an access category for transmitting VoIP data.

  The estimation unit 103 calculates the estimated values T0 to Tn of the transmission completion time when the number of retransmissions is 0 to n. Here, the estimated value T0 is an estimated value of the time from when the wireless communication device 10 starts transmitting the frame F to when it receives the acknowledge ACK for the frame F of the initial transmission without performing retransmission. In addition, the estimated value Tn is such that after the wireless communication device 10 starts transmitting the frame F (that is, the first transmission), the retransmission is performed n times, and an acknowledge ACK is sent to the frame F of the nth retransmission. It is an estimate of the time to receive. Further, it is assumed that the estimated value Tn of the transmission completion time exceeds the allowable transmission delay time Ta and the estimated value Tn-1 of the transmission completion time is equal to or less than the allowable transmission delay time Ta. In this case, the retransmission count upper limit value e is n-1. For example, when the allowable transmission delay time Ta is 20 ms, the estimated value T8 of the transmission completion time of 8 retransmissions is 19 ms, and the estimated value T9 of the transmission completion time of 9 retransmissions is 21 ms, the retransmission count upper limit value e Is 8.

  That is, the estimation unit 103 obtains the estimated values T0 to Tn of the transmission completion time corresponding to the number of transmissions of the frame F for each number of retransmissions (that is, the number of retransmissions 0 to n), and the transmission delay allowable time. The retransmission number upper limit value e is estimated based on the transmission number n of the estimated value Tn of the transmission completion time exceeding Ta. At that time, the estimation unit 103 is the number of times of transmission of the estimated value Tn of the transmission completion time that exceeds the allowable transmission delay time Ta (first transmission number) and the estimated value of the transmission completion time that is less than or equal to the allowable transmission delay time Ta. The retransmission number upper limit value e is estimated based on n-1 (second transmission number), which is the number of transmissions of Tn-1. In this case, the retransmission count upper limit value e is n-1 (second transmission count).

  The retransmission control for each frame is performed by the transmission unit 102. At that time, for example, when the transmitting unit 102 and the receiving unit 105 are functions realized by a wireless module independent of the CPU, the transmitting unit 102 or the receiving unit 105 may provide information on the number of times of retransmission performed depending on the specifications of the wireless module. There are times when it is provided to the estimation unit 103 and times when it is not provided. The correspondence by the estimation unit 103 to this difference in specifications will be described later.

  When the retransmission count upper limit value e estimated by the estimation unit 103 changes, the retransmission maximum count changing unit 104 determines the latest retransmission count upper limit value notified from the estimation unit 103 of the retransmission count upper limit value applied in the transmission unit 102. Change to e.

  Then, the receiving unit 105 receives the acknowledge ACK transmitted by the wireless communication device 20 with respect to the frame F transmitted by the transmitting unit 102, and when receiving, outputs a signal indicating that to the clock unit 101.

  Each function of the wireless communication device 10 described above may also have the wireless communication device 20. Further, in the control unit 100 shown in FIG. 1, each functional block can be integrated or divided. For example, the function of the clock unit 101 may be provided in the receiving unit 105 or the estimating unit 103. It suffices that the estimation unit 103 be able to obtain information indicating the time required until the transmission of the frame F is completed (acknowledge ACK is received).

  Next, a method of calculating the estimated values T0 to Tn of the transmission completion time by the estimation unit 103 and estimating the retransmission number upper limit value e will be described by taking two types of wireless systems as examples.

[Example 1: Wireless LAN (Local Area Network)]
First, a method of calculating the estimated value Tn of the transmission completion time by the estimation unit 103 when the wireless communication device 10 and the wireless communication device 20 are an IEEE 802.11 compliant wireless LAN will be described. In this case, in the MAC (Medium Access Control) layer, CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) is adopted as an access method. In this CSMA / CA, each wireless communication device detects whether or not another wireless communication device is transmitting a wireless signal (that is, performs carrier sense), and starts communication if it is not transmitted. Hereinafter, the waiting time associated with the carrier sense will be referred to as a carrier sense waiting time. Since the transmission completion time TM includes this carrier sense wait time, the transmission completion time TM changes according to the carrier sense wait time. Therefore, the transmission completion time TM changes according to the communication state of other wireless communication devices.

  The estimated value Tn of the transmission completion time accompanying the retransmission of n times is a fixed waiting time DIFS (Distributed Inter Frame Space), the estimated value Bi of the backoff time at the i-th retransmission, and the data transfer time at the i-th retransmission. Di, a total value CS of carrier sense wait times, a constant wait time SIFS (Short Inter Frame Space), a frame size AK (bytes) of an acknowledge ACK, and an ACK frame transfer rate Rack are used to calculate the equation (1). Calculate by

  Strictly speaking, it may be possible to include a flight time time in which the frame flies in the air, but the flight time time is extremely short, so it is not included in the equation (1). Further, since SIFS + (AK · 8) / Rack in the equation (1) is a short time, it may be possible to simplify the calculation and omit it.

  Further, the total value CS of carrier sense wait times is the total value of carrier sense wait times at the first time and each retransmission time, and is a value that does not depend on the number of retransmission times. The carrier sense waiting time is an unknown value that changes according to the communication environment. Therefore, the estimation unit 103 calculates the carrier sense waiting time including the transmission completion time as a total value over a plurality of transmission times, and based on the measurement value TM of the transmission completion time as described later in order to improve the estimation accuracy. Are changing adaptively.

  Further, the estimated value Bi of the back-off time is a minimum value CWmin of CW (contention window; random number generation range), a maximum value CWmax of CW, a slot time ST of a fixed time, and a range of 0 to 1. It is calculated by the equation (2) using the fixed value FV.

  Here, when FV is 0.5, Bi is the expected value of the backoff time, and when FV is 1, Bi is the maximum value of the backoff time, but not limited to these, FV is in the range of 0 to 1. It can take any value.

  Further, the data transfer time Di is calculated by the equation (3) using the frame size FS (bytes) and the frame transfer rate Ri in the i-th retransmission. Here, the frame transfer rate Ri changes, for example, when a combination of a modulation scheme and an error correction coding rate used (hereinafter, referred to as a combination of MCS (Modulation and Coding Scheme)) is changed. The combination of MCSs defines the wireless communication data rate. For this MCS combination, an MCS index that is a unique number is defined for each number of transmission streams. For example, the MCS of index 1 (hereinafter referred to as the MCS1 format) is QPSK (Quadrature Phase Shift Keying) of one transmission stream and has an error correction coding rate of 1/2. Further, for example, the MCS 6 is 64QAM (Quadrature Amplitude Modulation) of one transmission stream and has an error correction coding rate of 3/4. Also, at the time of retransmission, the combination of MCSs can be changed according to the number of times of retransmission. Also, the upper limit of the number of retransmissions can be defined in advance for each combination of MCSs. That is, the data rate in the case of retransmission is determined by how to define the combination of MCSs (this definition is called a transmission plan). For example, it is possible to define that MCS6 performs transmission 6 times, MCS4 performs transmission 4 times, MCS2 transmits transmission 3 times, and MCS1 transmits transmission 2 times at maximum (up to 15 transmissions (14 internal retransmissions)). The upper limit of the number of retransmissions for each combination of MCSs can be defined, for example, by a predetermined program executed by the CPU of the control unit 100 based on the QoS such as the access category specified by the application layer. Then, the transmission unit 102 executes the transmission of the frame F based on the predefined combination of MCSs and the upper limit of the number of retransmissions for each combination of MCSs. It is assumed that the estimation unit 103 can acquire information about the transmission plan instructed by the transmission unit 102 from the transmission unit 102 or another functional unit.

  In the calculation of the estimated value Tn of the transmission completion time, the total value CS of the carrier sense waiting time is a value unknown to the wireless communication device 10, while the other parameters are known values. Further, the total value CS of the carrier sense waiting time is a parameter that can greatly vary depending on the wireless environment. Therefore, in the present embodiment, the value of the total value CS of the carrier sense waiting time is changed based on the measured value TM of the transmission completion time in real time. That is, the estimated value Tn of the transmission completion time is more accurately calculated (that is, estimated) by correcting the total value CS of the carrier sense waiting times based on the actual measurement value TM of the transmission completion time.

  For example, the total value CS of the carrier sense waiting time is calculated by the equation (4) using the measurement value TM of the transmission completion time and the estimated value Te of the transmission completion time when the retransmission is performed up to the retransmission count upper limit value e. change. The CS on the right side is the current value, and the CS on the left side is the changed value. Further, the estimated value Te is a value when n = e in the equation (1).

  Here, when the number of retransmissions m corresponding to the measured value TM of the transmission completion time can be acquired, the total value CS of the carrier sense waiting time is the measured value TM of the transmission completion time and the retransmissions up to the number m of retransmissions. The estimated value Tm of the transmission completion time at that time may be used to change the value according to equation (5) instead of equation (4). Here, the estimated value Tm is a value when n = m in the equation (1).

  Since the total value of the total value CS of the carrier sense waiting time is not known at the first time before the measurement value TM of the transmission completion time is measured, the initial value is set to 0, and the measured value TM of the transmission completion time is set to the transmission delay allowable time Ta. It is also desirable to change when a shorter fixed delay is exceeded. For example, when the allowable transmission delay time Ta is 20 ms and the measured value TM of the transmission completion time exceeds 15 ms, the total value CS of the carrier sense waiting time is changed.

  When the total value CS of the carrier sense waiting time is changed by the equations (4) to (5), the changed value is reflected, and the transmission completion time of the n-th retransmission is reflected by the equation (1). Change the estimated value Tn. For example, the estimation unit 103 calculates the total value CS of carrier sense wait times included in the estimated value Tm of the transmission completion time on the basis of the value TM of the transmission completion time and the estimated value Tm of the transmission completion time measured by the time counting unit 101. Update.

  According to the above, when the deterioration of the wireless environment or the congestion with other wireless communication devices occur, the estimated value Tn of the transmission completion time according to the wireless environment is calculated by reflecting it and lengthening the carrier sense waiting time. It becomes possible to do.

  On the other hand, when the wireless environment is improved, it is desirable to reflect it and shorten the carrier sense waiting time. For example, when the total value CS of the carrier sense waiting time is larger than the measured value TM of the transmission completion time, the total value CS of the carrier sense waiting time is changed.

  The total value CS of the carrier sense waiting time includes the measured value TM of the transmission completion time, the constant waiting time DIFS, the minimum value CWmin of CW, the constant time slot time ST, the fixed value FV, and the frame size FS. , The frame transfer rate R0 in the initial transmission, the fixed waiting time SIFS, the frame size AK of ACK, and the ACK frame transfer rate Rack are changed by the equation (6).

  Since SIFS + (AK.multidot.8) / Rack in the equation (6) is a short time, it may be possible to simplify the calculation and omit it.

  Here, when the number of retransmissions m corresponding to the measured value TM of the transmission completion time can be acquired, the total value CS of the carrier sense waiting time is a constant value TM of the transmission completion time, the measured value m of the number of retransmissions, and a constant value. Waiting time DIFS, an estimated backoff time Bi in the i-th retransmission, a data transfer time Di in the i-th retransmission, a fixed waiting time SIFS, an ACK frame size AK, and an ACK frame transfer rate Rack. It is also possible to use and to change the equation (7) instead of the equation (6).

  When the total value CS of the carrier sense waiting time is changed by the formulas (6) to (7), the changed value is reflected, and the retransmission is performed n times by the formula (1) as described above. The estimated value Tn of the transmission completion time is changed.

  With the above processing, it is possible to calculate the estimated value Tn of the transmission completion time that reflects the quality situation when the quality of the wireless environment deteriorates and when the quality improves. Then, as described above, the estimation unit 103 determines that the estimated value Tn of the transmission completion time exceeds the allowable transmission delay time Ta, and the estimated value Tn-1 of the transmission completion time is equal to or less than the allowable transmission delay time Ta, n-1. The retransmission count upper limit value e is determined.

[Example 2: ZigBee (registered trademark)]
Next, a method of calculating the estimated value Tn of the transmission completion time by the estimation unit 103 when the wireless communication device 10 and the wireless communication device 20 are ZigBee compliant with IEEE802.15.4 will be described.

  The estimated value Tn of the transmission completion time with n retransmissions is the estimated value RBi of the random backoff time in the i-th retransmission, the overlap time OLi in the i-th retransmission, the data transfer time D, and the carrier sense wait time. Is calculated by the equation (8) using the sum CS of the above, the ACK waiting time WA, the frame size AK (bytes) of the acknowledge ACK, and the frame transfer rate Rzb. Here, the overlap time OLi in the i-th retransmission indicates a time when an additional waiting occurs due to overlap with the beacon transmission timing or the inactive period in which data is not transmitted after the random backoff time has elapsed. Since WA + (AK · 8) / Rzb in the equation (8) is short, it may be possible to simplify the calculation and omit it.

  The estimated value RBi of the random backoff time is a minimum backoff index BEmin, a maximum backoff index BEmax, a backoff period BP (bits), a frame transfer rate Rzb, and a fixed value in the range of 0 to 1. It is calculated by the equation (9) using FV and.

  Further, the data transfer time D is calculated by the equation (10) using the frame size FS (bytes) and the frame transfer rate Rzb. In ZigBee, unlike wireless LAN, the frame rate is fixed for each retransmission.

  The total value CS of the carrier sense waiting time in the equation (8) is changed by the above equations (4) to (5) when the measured value TM of the transmission completion time exceeds the fixed delay. However, in this case, the estimated value Te of the equation (4) is a value when n = e in the equation (8), and the estimated value Tm of the equation (5) is n = m in the equation (8). Is the value of.

  Further, when the total value CS of the carrier sense waiting times in the equation (8) is larger than the measured value TM of the transmission completion time, the measured value TM of the transmission completion time, the minimum backoff index BEmin, and the backoff period. The BP (bits), the fixed value FV, the frame transfer rate Rzb, the frame size FS, the ACK waiting time WA, and the ACK frame size AK are used to change the value according to Expression (11).

  Since WA + (AK · 8) / Rzb in the equation (11) is short, it may be possible to simplify the calculation and omit it.

  Here, when the number of retransmissions m corresponding to the measured value TM of the transmission completion time can be acquired, the total value CS of the carrier sense waiting times is the measured value TM of the transmission completion time, the measured value m of the number of retransmissions, and i. Estimated value RBi of random backoff time in the second retransmission, overlap time OLi in the i-th retransmission, data transfer time D, ACK waiting time WA, ACK frame size AK (bytes), and frame transfer rate Rzb. It is also possible to use and to change the equation (12) instead of the equation (11).

  By the above processing, the estimated value Tn of the transmission completion time reflecting the quality situation is reflected in both the case where the wireless communication device 10 and the wireless communication device 20 are ZigBee and the case where the quality of the wireless environment is deteriorated or improved. It becomes possible to calculate.

  Then, as described above, the estimated value Tn of the transmission completion time exceeds the allowable transmission delay time Ta, and the estimated value Tn-1 of the transmission completion time becomes equal to or less than the allowable transmission delay time Ta. To decide.

  The application of the present invention to the wireless LAN and ZigBee is presented as an example, and the present invention that changes the estimated value Tn of the transmission completion time to the upper limit value e of the number of retransmissions is not limited to the above example. It is applicable to various wireless communication devices.

  Next, an example of the operation of the wireless communication system 1 will be described with reference to FIGS. 3 and 4. 3 and 4 are flowcharts showing an example of the operation of the wireless communication system 1 described with reference to FIGS. 1 and 2B. 3 and 4 show the wireless LAN described using the wireless system as Example 1 above, and when the estimation unit 103 cannot acquire the number of retransmissions m corresponding to the measurement value TM of the transmission completion time from the transmission unit 102. 3 shows a flowchart of.

  The estimation unit 103 of the wireless communication device 10 determines whether there is a change in the combination of MCSs (step S10). In step S10, the estimation unit 103 determines whether this MCS combination is the same as the previous transmission or has been changed. If the combination of MCSs is the same as the previous transmission (step S10; NO), the process proceeds to step S30. On the other hand, when the combination of MCSs has been changed (step S10: YES), the process proceeds to step S20. In step S20, the estimation unit 103 changes the retransmission count upper limit value e by a subroutine described below by reflecting the value after the MCS change.

  In step S30, the estimation unit 103 determines whether or not the measured value TM of the transmission completion time exceeds a fixed delay shorter than the transmission delay allowable time Ta. When the measured value TM of the transmission completion time is less than or equal to the fixed delay (step S30; NO), the process proceeds to step S60. On the other hand, when the measured value TM of the transmission completion time exceeds the certain delay (step S30; YES), the process proceeds to step S40. In step S40, the estimation unit 103 recalculates the total value CS of the carrier sense waiting time by the above formula (4). In addition, thereafter, in step S50, the estimation unit 103 changes the retransmission count upper limit value e by a subroutine described later by reflecting the value of the total value CS of the changed carrier sense waiting time.

  In step S60, the estimation unit 103 determines whether the total value CS of the carrier sense wait times exceeds the measurement value TM of the transmission completion time. When the total value CS of the carrier sense waiting times is less than or equal to the measured value TM of the transmission completion time (step S60; NO), the process proceeds to step S90. On the other hand, if the total value CS of the carrier sense waiting time exceeds the measured value TM of the transmission completion time (step S60; YES), the process proceeds to step S70. In step S70, the estimation unit 103 recalculates the total value CS of the carrier sense waiting time by the above equation (6). Further, thereafter, in step S80, the estimation unit 103 changes the value of the total value CS of the changed carrier sense waiting time and changes the retransmission count upper limit value e by a subroutine described later.

  In step S90, the retransmission upper limit number changing unit 104 gives an instruction to the transmitting unit 102 to change the retransmission number upper limit value e estimated by the estimation unit 103 to the upper limit value of the retransmission number, and the instruction of the retransmission upper limit number changing unit 104. In response, the transmission unit 102 of the wireless communication device 10 transmits the frame F to the wireless communication device 20.

  Next, with reference to FIG. 4, the operation of the subroutine for changing the retransmission count upper limit value e will be described. In step S110, the estimation unit 103 substitutes 0 as an initial value for n. In step S120, the estimation unit 103 calculates the estimated value Tn of the transmission completion time according to the above equation (1). In step S130, the estimation unit 103 determines whether or not the estimated value Tn of the transmission completion time is within the transmission delay allowable time Ta. If the estimated value Tn of the transmission completion time exceeds the transmission delay allowable time Ta (step S130; NO), the process proceeds to step S150. On the other hand, if the estimated value Tn of the transmission completion time is within the transmission delay allowable time Ta (step S130; YES), the process proceeds to step S140. In step S140, the estimation unit 103 increments n, and proceeds to the process of step S120 again. In step S150, the estimation unit 103 substitutes n−1 into the retransmission count upper limit value e.

  In the subroutine shown in FIG. 4, the estimation unit 103 increases the n by 1 with 0 as the initial value, and the estimated value Tn of the transmission completion time is the smallest exceeding the transmission delay allowable time Ta set for each access category. Search for n, which is the value (ie, the first value). Then, the estimation unit 103 determines n−1 at this time as the retransmission count upper limit value e.

  By the processing shown in FIGS. 3 and 4, the estimation unit 103 causes the transmission time closest to the transmission delay allowable time Ta without exceeding the transmission delay allowable time Ta determined for each access category based on the value of the transmission completion time TM. Then, the number of retransmissions is estimated as the retransmission count upper limit value e.

  Note that FIG. 3 is a flowchart when the estimation unit 103 cannot acquire the number of retransmissions m corresponding to the measurement value TM of the transmission completion time from the transmission unit 102, but when the estimation unit 103 can acquire the number of retransmissions m. Can be changed as follows. That is, in step S40, equation (5) can be used instead of equation (4). Further, in step S70, formula (7) can be used instead of formula (6).

  As described above, according to the present embodiment, by estimating the retransmission count upper limit value e that does not exceed the transmission delay allowable time until the data retransmission is completed, the retransmission count can be adaptively adjusted according to the wireless environment. Since the upper limit value is changed, it is possible to set the upper limit value of the number of retransmissions to an appropriate value so that the time until the data retransmission is completed does not exceed the allowable transmission delay time. According to this, it is possible to reduce the number of retransmissions of unnecessary frames that are discarded on the receiving side. Therefore, the delay time of data transmission / reception can be reduced. It should be noted that when estimating the retransmission number upper limit value e that the time until the data retransmission is completed does not exceed the transmission delay allowable time, the maximum time until the data retransmission is completed does not exceed the transmission delay allowable time. It is desirable to set the value of the number of retransmissions to the upper limit e of number of retransmissions. In this case, it is possible to try to retransmit the data by maximally utilizing the transmission delay allowable time while preventing the time until the data retransmission is completed from exceeding the transmission delay allowable time.

  Further, according to the present embodiment, the timer unit 101 measures the transmission completion time TM from when the transmission unit starts transmitting the data until when the transmission of the data is completed. The estimation unit 103 updates the total value CS of carrier sense wait times included in the estimated value Tn of the transmission completion time, based on the value of the transmission completion time TM measured by the clock unit 101 and the estimated value Tn of the transmission completion time. To do. This makes it possible to estimate the total value CS of the carrier sense wait times included in the estimated value Tn of the transmission completion time, and to estimate the retransmission count upper limit value e using the estimated total value CS of the carrier sense wait times. It will be possible.

  Further, according to the present embodiment, the estimation unit 103 obtains the estimated value Tn of the transmission completion time corresponding to the number of times of transmission of the data for each number of transmissions, and estimates the transmission completion time Tn that exceeds the allowable transmission delay time Ta. The upper limit value e of the number of retransmissions is estimated based on the number of transmissions of. As a result, the retransmission count upper limit value e can be estimated based on the number of times of transmission of the estimated value Tn of the transmission completion time that exceeds the allowable transmission delay time Ta.

  Further, according to the present embodiment, the estimation unit 103 obtains the estimated value Tn of the transmission completion time corresponding to the number of times of transmission of the data for each number of transmissions, and estimates the transmission completion time Tn that exceeds the allowable transmission delay time Ta. The upper limit value e of the number of retransmissions is estimated based on the number of transmissions of. As a result, the retransmission count upper limit value e can be estimated based on the number of times of transmission of the estimated value Tn of the transmission completion time that exceeds the allowable transmission delay time Ta.

  Further, according to the present embodiment, the estimation unit 103 calculates the value of the total value CS of carrier sense wait times based on the value of the transmission completion time TM measured by the timer 101, and calculates the calculated carrier sense wait time. The retransmission number upper limit value e is estimated using the total value CS of As a result, it is possible to estimate the total value CS of unknown carrier sense wait times, and it is possible to estimate the retransmission count upper limit value e using the estimated total value CS of carrier sense wait times.

Further, according to the present embodiment, the estimation unit 103 recalculates the total value CS of carrier sense wait times when the measured value TM of the transmission completion time exceeds the fixed delay shorter than the allowable transmission delay time Ta. To do. This makes it possible to adjust the frequency of recalculation of the total value CS of the carrier sense waiting time, reduce the load of arithmetic processing for estimating the total value CS of the carrier sense waiting time, and wait for the carrier sense waiting time. It is possible to reduce the fluctuation of the estimated value of the total value CS of time.
Further, according to the present embodiment, the estimation unit 103 changes the estimated value Tn of the transmission completion time according to the number of times of data transmission when the total value CS of the carrier sense waiting time is changed. This makes it possible to control the estimated value Tn of the transmission completion time according to the number of times of data transmission to be changed only when the total value CS of the carrier sense waiting time is changed.

  In the present embodiment, the retransmission count upper limit value e that does not exceed the transmission delay allowable time is estimated, and the actual retransmission count limit value is changed based on the estimated retransmission count upper limit value e. As a result, the following effects can be obtained. For example, if the upper limit value of the actual number of retransmissions is changed without estimating the upper limit value e of retransmissions, the following problem occurs, but the problem does not occur in the configuration of the present embodiment. That is, even when the retransmission count upper limit value e is not estimated, the retransmission count upper limit value is transmitted by repeating the procedure of decreasing the retransmission count upper limit value when the transmission completion time exceeds the transmission delay allowable time, for example. The completion time can be changed to a value that does not exceed the transmission delay allowable time. However, in this configuration, the maximum number of retransmissions is changed while the number of times a frame can be retransmitted within the transmission delay allowable time is unknown. Therefore, the same procedure is executed a plurality of times until the optimum upper limit value of the number of retransmissions for completing the transmission within the allowable transmission delay time is reached, which may take time. Furthermore, when the wireless environment changes, the change in the upper limit of the number of retransmissions may not keep up with the changes in the wireless environment. However, in the present embodiment, the retransmission number upper limit value e that does not exceed the transmission delay allowable time is estimated, and the upper limit value of the actual retransmission number is changed based on the estimated retransmission number upper limit value e. It is possible to solve the problem and more appropriately change the upper limit value of the number of retransmissions.

  As described above, in the present embodiment, when the retransmission count upper limit value e estimated by the estimation unit 103 is changed, the retransmission upper limit count changing unit 104 causes the retransmission count upper limit value to be applied in the transmitting unit 102 to be It is changed to the retransmission count upper limit value e estimated by the estimation unit 103. That is, when the retransmission count upper limit value e changes, the transmitting unit 102 changes the retransmission count upper limit value. When performing retransmission while changing the combination of MCSs as described above, the upper limit value of the number of retransmissions can be set for each combination of MCSs. In this case, when changing the upper limit value of the number of retransmissions for all the combinations of a plurality of MCSs, it is possible to arbitrarily select which combination of MCSs changes the upper limit value of the number of retransmissions. For example, first, MCS6 transmits up to 6 times, then MCS4 transmits up to 4 times, then MCS2 transmits up to 3 times, and MCS1 transmits up to 2 times. It is assumed that a transmission plan has been created. In this example, when the upper limit value of the number of retransmissions is reduced in accordance with the change of the upper limit number of retransmissions e, for example, the number of retransmissions may be reduced from the last (MCS1) in ascending order, or the number of retransmissions may be reduced from the first (MCS6) in descending order. May be reduced. That is, in this example, a transmission plan of 6 times for MCS6, 4 times for MCS4, 3 times for MCS2, and 2 times for MCS1, for example, 6 times for MCS6, 4 times for MCS4, 3 times for MCS2, and The MCS1 may be changed to a one-time transmission plan, or the MCS6 may be changed to five times, the MCS4 to four times, the MCS2 to three times, and the MCS1 to two times. Absent. Alternatively, for example, it may be changed from the upper limit number of times of the intermediate MCS4 or MCS2. When the frame transfer rate is changed by changing the number of retransmissions, it is necessary to repeat the recalculation to calculate the estimated value Tn of the transmission completion time.

  Further, in the transmission plan, the lowest rate MCS (MCS1 in this example) having high noise resistance is often provided at the end. Therefore, when the number of retransmissions is reduced from the last (MCS1) in ascending order, the number of retransmissions that matches the upper limit of the number of retransmissions after the reduction is the last retransmission and one or more retransmissions from the last retransmission are performed at the frame transfer rate. It is also desirable to devise to retransmit at the lowest rate within the setting range of. For example, in the flowchart of FIG. 3, when the retransmission upper limit number changing unit 104 reduces the retransmission upper limit number before executing step S90, one or more retransmissions from the end are performed at the lowest of the setting range of the frame transfer rate. It is possible to add a step of changing the transmission plan so as to be retransmitted at a rate. Alternatively, when the transmitting unit 102 receives an instruction to reduce the maximum number of retransmissions by the maximum retransmission number changing unit 104, one or more retransmissions from the end is a retransmission at the lowest rate within the frame transfer rate setting range. The transmission plan may be changed as required.

  Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and the gist of the invention, and at the same time, are included in the invention described in the claims and the scope equivalent thereto.

  Each of the above-mentioned devices has a computer inside. The process of each process of each device described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing the program. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Further, the computer program may be distributed to the computer via a communication line, and the computer that receives the distribution may execute the program.

  Further, the program may be for realizing a part of the functions described above. Further, it may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 10 ... Wireless communication device, 100 ... Control part, 101 ... Timing part, 102 ... Transmitting part, 103 ... Estimating part, 104 ... Retransmission upper limit number changing part, 105 ... Receiving part, 110 ... Storage part, 20 ... Wireless communication device

Claims (4)

A transmission unit for transmitting data,
An estimation unit that estimates a retransmission count upper limit value that does not exceed the transmission delay allowable time of the data until the time to complete the retransmission of the data,
And a retransmission upper limit number changing unit that changes the upper limit value of the number of retransmissions in the transmission unit to the retransmission number upper limit value estimated by the estimation unit,
The estimation unit obtains an estimated value of the transmission completion time according to the number of times of transmission of the data based on a delay time that varies in each transmission time for each of the transmission times, and determines the transmission completion time exceeding the transmission delay allowable time. Estimating the retransmission number upper limit value based on the transmission number of the estimated value,
The estimation unit includes a first transmission number that is the number of transmissions of the estimated value of the transmission completion time that exceeds the transmission delay allowable time, and a number of transmissions of the estimated value of the transmission completion time that is equal to or less than the transmission delay allowable time. Estimating the upper limit of the number of retransmissions based on the second number of transmissions
A wireless communication device characterized by the above-mentioned. The wireless communication device according to claim 1, wherein the retransmission count upper limit value is the second transmission count. A sending procedure for sending data,
An estimation procedure for estimating a retransmission count upper limit value in which the time required to complete the retransmission of the data does not exceed the transmission delay allowable time of the data,
And a retransmission upper limit number changing procedure of changing the upper limit value of the number of retransmissions in the transmission procedure to the retransmission number upper limit value estimated in the estimation procedure,
The estimation procedure obtains an estimated value of the transmission completion time according to the number of times of transmission of the data based on the delay time that varies in each transmission time for each of the transmission times, and determines the transmission completion time exceeding the transmission delay allowable time. Estimating the retransmission number upper limit value based on the transmission number of the estimated value,
The estimation procedure includes a first transmission number that is the number of transmissions of the estimated value of the transmission completion time that exceeds the transmission delay allowable time, and a number of transmissions of the estimated value of the transmission completion time that is less than or equal to the transmission delay allowable time. Estimating the upper limit of the number of retransmissions based on the second number of transmissions
A wireless communication method characterized by the above. In the computer that the wireless communication device has,
A sending procedure for sending data,
An estimation procedure for estimating a retransmission count upper limit value in which the time required to complete the retransmission of the data does not exceed the transmission delay allowable time of the data,
A retransmission upper limit number changing procedure of changing the upper limit value of the number of retransmissions in the transmitting procedure to the upper limit number of retransmissions estimated in the estimating procedure, and a wireless communication program for executing
The estimation procedure obtains an estimated value of the transmission completion time according to the number of times of transmission of the data based on the delay time that varies in each transmission time for each of the transmission times, and determines the transmission completion time exceeding the transmission delay allowable time. Estimating the retransmission number upper limit value based on the transmission number of the estimated value,
The estimation procedure includes a first transmission number that is the number of transmissions of the estimated value of the transmission completion time that exceeds the transmission delay allowable time, and a number of transmissions of the estimated value of the transmission completion time that is less than or equal to the transmission delay allowable time. Estimating the upper limit of the number of retransmissions based on the second number of transmissions
Wireless communication program.

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