Wireless communication device and wireless communication method

Abstract

A wireless communication device and a wireless communication method are capable of improving utilization efficiency of a transmission path. More particularly, in a system that uses a service period, such as a restricted target-wait-time (R-TWT) service period, to transfer real-time application (RTA) data between wireless devices, a reception-side device and a transmission side device collaborate to allow for retransmission of missed RTA at a later time that comes after the service period.

Description

WIRELESS COMMUNICATION DEVICE AND WIRELESS COMMUNICATION METHOD

[0001] The present disclosure relates to a wireless communication device and a wireless communication method, and more particularly, to a wireless communication device and a wireless communication method capable of improving utilization efficiency of a transmission path.

[0002] This application claims the benefit of Japanese Priority Patent Application JP 2023-171119 filed on October 2, 2023, the entire contents of which is incorporated herein by reference.

[0003] Currently, in the IEEE802.11be standard, not only a data transmission amount of an assumed application is increased, but also the data is required to have low latency (Low Latency) and high reliability. As these communication technologies, in IEEE802.11be standardization, a method of sequentially transmitting low-latency data by periodically setting restricted target wake-up time (R-TWT) is currently studied.

[0004] The R-TWT technology is defined as a technology that determines a time for activating a target existing in the related art and activates the target to realize a low power consumption operation, and is defined as a mechanism in which a transmission-side communication device periodically acquires a transmit opportunity (TXOP) and transmits data to be transmitted as a low latency in the transmit opportunity (TXOP) with priority over other data. The R-TWT technology is regarded as a technique for transmitting data suitable for real-time applications, and technical proposals using these techniques have been currently made.

[0005] PTL 1 discloses a technique of limiting a time length by communication addressed to another communication device in a case where a TWT operation is requested and a data frame is for low latency communication. PTL 2 discloses a technique in which a transmission period of N cycles is set as a beacon cycle, and OFDMA communication is performed by overlapping with M cycles shorter than the transmission period of N cycles. PTL 3 discloses a technique for performing multilink communication by including AP Primary Link information in a TWT request as a connection request / re-connection request.

[0006] JP 2022-133131 AJP 2021-016059 AJapanese Translation of PCT International Application Publication No. 2022-541085

[0007] Although the R-TWT technology described above is defined so that the transmission-side communication device and the reception-side communication device operate in synchronization with each other at a predetermined cycle, it is necessary to set a service period (SP) of the R-TWT in order to define a certain cycle and prioritize the communication. In a case where these techniques are applied to data requiring a low latency, it is necessary to set parameters for completing transmission within an allowable delay time, and there has been a possibility that a transmission delay will occur unless an arrival cycle of the R-TWT SP is shortened.

[0008] In addition, since a communication error may occur on a wireless transmission path, unless data in which the communication error has occurred is retransmitted, all data cannot be reliably delivered end to end. In particular, in a case where the communication amount for performing the minimum necessary data transmission is secured by securing the transmit opportunity (TXOP) once by setting the R-TWT SP, it has been difficult to retransmit the undelivered data within a service period. Therefore, there has been a demand for a technique for improving the utilization efficiency of the transmission path in the case of retransmitting the undelivered data.

[0009] The present disclosure has been made in view of such a situation, and is capable of improving utilization efficiency of a transmission path.

[0010] A wireless communication device according to one aspect of the present disclosure is a wireless communication device including: a control unit that receives data transmitted from another wireless communication device, adjusts an output timing of outputting the received data to a connected application device, generates, according to the output timing, retransmission request information for requesting retransmission of undelivered data that is the data that has not been delivered among the transmitted data, and transmits the generated retransmission request information to the other wireless communication device.

[0011] A wireless communication method according to one aspect of the present disclosure is a wireless communication method including: receiving data transmitted from another wireless communication device; adjusting an output timing of outputting the received data to a connected application device; generating, according to the output timing, retransmission request information for requesting retransmission of undelivered data that is the data that has not been delivered among the transmitted data; and transmitting the generated retransmission request information to the other wireless communication device, by a wireless communication device.

[0012] In the wireless communication device and the wireless communication method according to one aspect of the present disclosure, data transmitted from another wireless communication device is received, an output timing of outputting the received data to an application device to be connected is adjusted, retransmission request information for requesting retransmission of undelivered data that is the data that has not been delivered among the transmitted data is generated according to the output timing, and the generated retransmission request information is transmitted to the other wireless communication device.

[0013] A wireless communication device according to one aspect of the present disclosure is a wireless communication device including: a control unit that transmits data to another wireless communication device, receives retransmission request information transmitted from the other wireless communication device, and retransmits, to the other wireless communication device, the data that is the undelivered data specified by the received retransmission request information and that is the undelivered data among the transmitted data, according to an output timing of outputting the data to an application device connected in the other wireless communication device.

[0014] A wireless communication method according to one aspect of the present disclosure is a wireless communication method, including: transmitting data to another wireless communication device; receiving retransmission request information transmitted from the other wireless communication device; and retransmitting, to the other wireless communication device, the data that is the undelivered data specified by the received retransmission request information and that is the undelivered data among the transmitted data, according to an output timing of outputting the data to an application device connected in the other wireless communication device, by the wireless communication device.

[0015] In the wireless communication device and the wireless communication method according to one aspect of the present disclosure, data is transmitted to another wireless communication device, retransmission request information transmitted from the other wireless communication device is received, and the data that is undelivered data specified by the received retransmission request information and undelivered data among the transmitted data is retransmitted to the other wireless communication device according to an output timing of outputting the data to an application device connected in the other wireless communication device.

[0016] Note that the wireless communication device according to one aspect of the present disclosure may be an independent device or an internal block configuring one device.

[0017] Fig. 1 is a diagram illustrating a configuration example of a wireless LAN system to which the present disclosure is applied.Fig. 2 is a diagram illustrating an operation of a related-art R-TWT.Fig. 3 is a diagram illustrating problems in a wireless communication using a related-art R-TWT SP.Fig. 4 is a diagram illustrating problems in the wireless communication using the related-art R-TWT SP.Fig. 5 is a diagram illustrating an example of an output sequence of related-art RTA data application.Figs. 6A and 6B are diagrams illustrating a configuration example of a downlink R-TWT SP according to a related art.Figs. 7A and 7B are diagrams illustrating a modification of the downlink R-TWT SP configuration example according to the related art.Figs. 8A and 8B are diagrams illustrating a configuration example of an uplink R-TWT SP according to the related art.Figs. 9A and 9B are diagrams illustrating a modification of the configuration example of the uplink R-TWT SP according to the related art.Fig. 10 is a diagram illustrating an example of an output sequence of an application of RTA data according to the present disclosure.Figs. 11A and 11B are diagrams illustrating a configuration example of a downlink R-TWT SP according to the present disclosure.Figs. 12A and 12B are diagrams illustrating a configuration example of an uplink R-TWT SP according to the present disclosure.Fig. 13 is a diagram illustrating a configuration example of a buffer in a case where RTA data is transmitted using the R-TWT SP.Fig. 14 is a block diagram illustrating a configuration example of a wireless communication device to which the present disclosure is applied.Fig. 15 is a block diagram illustrating a configuration example of a wireless communication module in Fig. 14.Fig. 16 is a diagram illustrating a first example of an exchange sequence of a setup request frame for RTA data exchange.Fig. 17 is a diagram illustrating a second example of the exchange sequence of the setup request frame for the RTA data exchange.Fig. 18 is a diagram illustrating a configuration of a setup request element of an access control parameter of RTA data according to the present disclosure.Fig. 19 is a diagram illustrating a configuration of a setup response element of the access control parameter of RTA data according to the present disclosure.Fig. 20 is a diagram illustrating a configuration example of a trigger frame according to the present disclosure.Fig. 21 is a diagram illustrating a configuration example of a data frame according to the present disclosure.Fig. 22 is a diagram illustrating a configuration example of a delimiter of a data frame according to the present disclosure.Fig. 23 is a diagram illustrating a configuration example of a block ACK frame according to the present disclosure.Fig. 24 is a flowchart illustrating a flow of exchange processing of setup information of an RTA parameter.Fig. 25 is a flowchart illustrating a flow of the exchange processing of setup information of the RTA parameter.Fig. 26 is a flowchart illustrating a flow of transmission processing by a transmission-side communication device.Fig. 27 is a flowchart illustrating a flow of the transmission processing by the transmission-side communication device.Fig. 28 is a flowchart illustrating a flow of reception processing by a reception-side communication device.Fig. 29 is a flowchart illustrating a flow of reception processing by the reception-side communication device.

[0018] <System configuration> Fig. 1 is a diagram illustrating a configuration example of a wireless local area network (LAN) system to which the present disclosure is applied. In Fig. 1, the wireless LAN system includes a transmission-side communication device 10Tx and a reception-side communication device 10Rx, and one of the communication devices operates as an access point (AP) and the other communication device operates as a communication terminal (station (STA)), to configure one basic service set (BSS).

[0019] Furthermore, in Fig. 1, in a case where there are the transmission-side communication device 10Tx on a data transmission side and the reception-side communication device 10Rx on a data reception side, there is an overlapping basic service set (OBSS) as a peripheral network including communication devices 20A and 20B around them. The communication devices 20A and 20B configuring the network of the OBSS do not necessarily conform to the latest standard, and may include a legacy communication device that can recognize only a signal of a communication scheme standardized in the past. Hereinafter, a case where the communication devices 20A and 20B are legacy communication devices will be described.

[0020] In Fig. 1, white circles represent wireless communication devices to which the present disclosure is applied, radio coverage ranges are indicated by broken lines A1 and A2, and a configuration is illustrated in which low-delay data transmission is performed from the transmission-side communication device 10Tx to the reception-side communication device 10Rx using a real-time application (RTA) indicated by an arrow C1. In addition, black circles represent legacy communication devices configuring the OBSS, and radio coverage ranges are indicated by dash-dotted lines A3 and A4.

[0021] Here, in the communication devices 20A and 20B which are legacy communication devices, it is difficult to recognize a communication protocol for a real-time application described in the latest standard, it is not possible to grasp that communication of the real-time application is performed almost periodically, and in a case where it is determined that the transmission path is in an empty state, communication is started. That is, Fig. 1 illustrates a state in which transmission signals from the communication devices 20A and 20B of the OBSS interfere with data transmission of a real-time application used between the transmission-side communication device 10Tx and the reception-side communication device 10Rx as indicated by arrows I1 and I2.

[0022] <Related-art Operation> Fig. 2 is a diagram illustrating an operation of a related-art restricted target wake-up time (R-TWT). In Fig. 2, an upper stage illustrates a service period (SP) of the R-TWT set in advance, a middle stage illustrates a state in which the operation of the transmission-side communication device 10Tx that acquires a transmit opportunity in the TWT transitions from a left side to a right side with a lapse of time, and a lower stage illustrates a state in which the operation of the reception-side communication device 10Rx that almost periodically receives in the TWT transitions from the left side to the right side. Further, in the middle stage and the lower stage, the data transmission operation is illustrated as an upward convex state and the data reception operation is illustrated as a downward convex state with respect to a time axis corresponding to the time direction.

[0023] Here, as indicated by a section indicated by a broken line of the upper stage, a SP of the R-TWT is set substantially periodically in advance, and within the SP period, for example, data (hereinafter, also referred to as RTA data) of a real-time application to which a traffic identifier (TID) as a specific identifier is assigned can be preferentially transmitted. In addition, after the lapse of the SP period, since other general data can be transmitted and received, arbitrary data (hereinafter, also referred to as other data) is exchanged. That is, in Fig. 2, in the period of the R-TWT SP, the RTA data #1 to #4 are transmitted, but the other data #1 to #3 are transmitted outside the period. Note that the RTA data is also described as RTD, and the other data is also described as ND.

[0024] Fig. 3 is a diagram illustrating problems in related-art wireless communication using an R-TWT SP. Fig. 3 illustrates a flow of a configuration similar to that of Fig. 2, and redundant description is appropriately omitted. In Fig. 3, when a second R-TWT SP arrives, for example, in a state in which the signal transmission of the communication device 20A existing in the OBSS in which the setting of the R-TWT SP cannot be grasped is started, the period is treated as a BUSY state. Therefore, even if the SP of the R-TWT arrives, transmission of desired RTA data cannot be performed in a case where the transmission-side communication device 10Tx is in the BUSY state.

[0025] In addition, when the third R-TWT SP arrives, even if data addressed to the reception-side communication device 10Rx is transmitted, if the reception-side communication device Rx strongly receives a signal from the communication device 20B of the OBSS whose setting of the R-TWT SP cannot be grasped, there is a problem that desired RTA data cannot be correctly decoded. Furthermore, in a case where the BUSY state exceeds the SP of the R-TWT, the data transmission of the real-time application scheduled in the cycle cannot be performed, and the transmission is performed after performing general data and access control. In this case, the RTA data is not necessarily preferentially transmitted. Fig. 3 illustrates a case where the delay is accumulated and the second RTA data #2 is transmitted when the fourth R-TWT SP arrives.

[0026] Fig. 4 is a diagram illustrating another case of the problem in the related-art wireless communication using the R-TWT SP. Fig. 4 illustrates a flow of a configuration similar to Fig. 2, and redundant description will be appropriately omitted. Fig. 4 illustrates a case where communication is performed with the service period (SP) of the R-TWT set longer than that in the case of Fig. 2 in consideration of retransmission of the RTA data.

[0027] Fig. 4 illustrates a state in which the transmission-side communication device 10Tx can transmit desired RTA data #2 by canceling the BUSY state within the period when the second R-TWT SP arrives, for example, even in the BUSY state in which the signal transmission of the communication device 20A existing in the OBSS in which the setting of the R-TWT SP cannot be grasped is started, as long as the RTWTSP is sufficiently set. In addition, in the third R-TWT SP, even in a case where the reception-side communication device 10Rx is in the BUSY state, retransmission can be performed in the R-TWT SP, and the desired RTA data #3 can be periodically transmitted. However, since a portion other than the R-TWT SP becomes relatively short, there is a problem that an opportunity to transmit data other than the RTA data decreases.

[0028] Fig. 5 is a diagram illustrating an example of a related-art output sequence of an application of RTA data. In the sequence diagram of Fig. 5, it is assumed that time sequentially passes from an upper side to a lower side in the diagram. Furthermore, the sequence diagram of Fig. 5 illustrates a flow of outputting the received RTA data to the application of the reception-side communication device 10Rx on the right side in the drawing when the data is transmitted through the wireless transmission path in a case where predetermined RTA data substantially periodically arrives from the application of the transmission-side communication device 10Tx on the left side in the drawing.

[0029] That is, the transmission-side communication device 10Tx is configured to collectively transmit the RTA data in the period of the R-TWT SP set substantially periodically, and here, the RTA data #1 to #3 is transmitted using the first R-TWT SP. At this time, in a case where the RTA data #3 does not correctly arrive at the reception-side communication device 10Rx, the situation is returned to the transmission-side communication device 10Tx through, for example, a block ACK (BA) frame. Subsequently, in the second R-TWT SP, new RTA data #4 to #6 is transmitted including the RTA data #3 that has not been delivered yet. Furthermore, at this time, in a case where the RTA data #6 does not correctly arrive at the reception-side communication device 10Rx, the situation is returned to the transmission-side communication device 10Tx through, for example, a block ACK frame.

[0030] Further, in the third R-TWT SP, new RTA data #7 to 8 is transmitted including the RTA data #6 that has not been delivered yet. Also here, in a case where the RTA data #7 does not correctly arrive at the reception-side communication device 10Rx, the situation is returned to the transmission-side communication device 10Tx through, for example, a block ACK frame. Then, in the fourth R-TWT SP, it is configured to retransmit the RTA data #7 that has not been delivered, and the transmission-side communication device 10Tx confirms the reception of all the data by receiving the return of the block ACK frame from the reception-side communication device 10Rx.

[0031] On the other hand, the reception-side communication device 10Rx is configured to output the RTA data received at a predetermined timing to the connected application device, and here, an example is illustrated in which the data is output after the first R-TWT SP that has received the first data ends. That is, there is the undelivered RTA data #3, and then a delay time occurs until the undelivered data is retransmitted, but these delays are absorbed and reach the application device at first. However, the retransmission timing is delayed due to an increase in the undelivered data, and further, in a case where the undelivered data #6 and #7 exist in the middle, the RTA data #7 does not arrive, so that a delay occurs until the data is delivered to the application device as indicated by an arrow D1 in the drawing.

[0032] Figs. 6A and 6B are diagrams illustrating a configuration example of a downlink (DL) R-TWT SP according to the related art. Figs. 6A and 6B illustrate an example in which the access point (AP) is set as the transmission-side communication device 10Tx in an upper stage illustrated in Fig. 6A and the communication terminal (STA) is set as the reception-side communication device 10Rx in a lower stage illustrated in Fig. 6B, as a diagram in which time elapses from the left side to the right side in the diagram. In addition, in Figs. 6A and 6B, with respect to the time axis corresponding to the time direction, the signal to be transmitted is illustrated as an upward convex state, and the signal to be received is illustrated as a downward convex state, and the time of the R-TWT SP necessary for communicating the desired RTA data is illustrated by a broken line.

[0033] That is, the time during which the predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P1 indicated by a broken line. Here, the transmission-side communication device 10Tx is configured to transmit the RTA data (DL RTA Data) in a downstream direction (DL) from the access point (AP) according to a predetermined access procedure, and return an acknowledgment of receipt from the reception-side communication device 10Rx by a block ACK frame (BA). Here, a redundant time of the R-TWT SP including retransmission illustrated in Figs. 7A and 7B to be described later is indicated by a period P2 indicated by a dash-dotted line for convenience.

[0034] Figs. 7A and 7B are diagrams illustrating a modification of a downlink R-TWT SP configuration example according to the related art. Since Figs. 7A and 7B are described in a manner similar to Figs. 6A and 6B, redundant description will be appropriately omitted. Figs. 7A and 7B illustrate an example in which a redundant time for retransmission is included in one R-TWT SP, and a time during which predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P2 indicated by a dash-dotted line. In the case of this configuration example, an example is illustrated in which the period of the R-TWT SP that is originally necessary is doubled and set in order to enable the same amount of data to be retransmitted by setting the R-TWT SP once.

[0035] Here, assuming a case where the transmission-side communication device 10Tx transmits the RTA data (DL RTA Data) in the downstream direction by a predetermined access procedure, and returns an acknowledgment of receipt thereof from the reception-side communication device 10Rx by a block ACK frame (BA), and all of these RTA data are undelivered, a sufficient time is secured for returning a retransmission frame and a block ACK frame of similar RTA data. However, in a case where these retransmissions are not performed, the time of the R-TWT SP redundantly secured is wasted. Therefore, it is necessary to release the period using a CF-END (Contention Free-END) frame or the like as necessary.

[0036] Figs. 8A and 8B are diagrams illustrating a configuration example of an uplink (UL) R-TWT SP according to the related art. Since Figs. 8A and 8B are described in a manner similar to Figs. 6A and 6B, redundant description will be appropriately omitted. In Figs. 8A and 8B, a time during which the predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P1 indicated by a broken line. In Figs. 8A and 8B, because of the uplink, in contrast to the downlink, the access point (AP) serves as the reception-side communication device 10Rx, and the communication terminal (STA) serves as the transmission-side communication device 10Tx.

[0037] Here, a predetermined trigger frame (UL RTA Trigger) is transmitted from the access point (AP), so that the communication terminal (STA) serving as the transmission-side communication device 10Tx transmits the RTA data (UL RTA Data) in an uplink direction (UL) according to a predetermined access procedure, and the acknowledgment of receipt is returned from the access point (AP) serving as the reception-side communication device 10Rx according to the block ACK frame (BA). Here, a redundant time including retransmission of the R-TWT SP illustrated in Figs. 9A and 9B to be described later is indicated by a period P2 indicated by a dash-dotted line for convenience.

[0038] Figs. 9A and 9B are diagrams illustrating a modification of an uplink R-TWT SP configuration example according to the related art. Since Figs. 9A and 9B are described in a manner similar to Figs. 8A and 8B, redundant description will be omitted. Figs. 9A and 9B illustrate an example in which a redundant time for retransmission is included in one R-TWT SP, and a time during which predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P2 indicated by a dash-dotted line. In the case of this configuration example, an example is illustrated in which the period of the R-TWT SP that is originally necessary is doubled and set in order to enable the same amount of data to be retransmitted by setting the R-TWT SP once.

[0039] Here, a predetermined trigger frame is transmitted from the access point (AP), so that the communication terminal (STA) to be the transmission-side communication device 10Tx transmits the uplink RTA data (UL RTA Data) according to the trigger frame by a predetermined access procedure, and the acknowledgment of receipt is returned from the access point (AP) to be the reception-side communication device 10Rx by a block ACK frame (BA). In addition, assuming a case where all of these RTA data are undelivered, a sufficient time is secured for returning a retransmission frame and a block ACK frame of similar RTA data. However, in a case where these retransmissions are not performed, the time of the R-TWT SP secured redundantly is wasted, and thus, it is necessary to release the period using a CF-END frame or the like as necessary.

[0040] As described above, in the related-art operation, in a case where the undelivered data is retransmitted, the transmission path cannot be efficiently used, and as a result, a large delay occurs until the RTA data is output to the application device when the undelivered data exists. In the operation of the present disclosure, the utilization efficiency of the transmission path is improved in a case where retransmission of the undelivered data is performed. As a result, in the present disclosure, even when there is undelivered data, it is possible to suppress a delay until the RTA data is output to the application device. Hereinafter, a configuration of the present disclosure will be described.

[0041] <Operation of the present disclosure> Fig. 10 is a diagram illustrating an example of an output sequence of an application of RTA data according to the present disclosure. Similarly to the sequence diagram of Fig. 5, the sequence diagram of Fig. 10 illustrates a configuration in which time sequentially passes from the upper side to the lower side in the diagram, and illustrates a flow of outputting the received RTA data to the application of the reception-side communication device 10Rx on the right side in the diagram in a case where the data is transmitted through the wireless transmission path in a case where predetermined RTA data substantially periodically arrives from the application of the transmission-side communication device 10Tx on the left side in the diagram.

[0042] That is, the transmission-side communication device 10Tx is configured to collectively transmit the RTA data in the period of the R-TWT SP set substantially periodically, and here, the RTA data #1 to #3 is transmitted using the first R-TWT SP. At this time, in a case where the RTA data #3 does not correctly arrive at the reception-side communication device 10Rx, the situation is returned to the transmission-side communication device 10Tx through, for example, a block ACK frame (BA). Note that the reception-side communication device 10Rx can set a delay amount (initial delay) to such an extent that no delay occurs when the undelivered data occurs for the RTA data, adjust the output timing, and output the data to the application.

[0043] Here, unlike the related-art operation illustrated in Fig. 5, in the operation of the present disclosure, as illustrated in Fig. 10, before the retransmission of the RTA data is performed in the R-TWT SP, the retransmission is immediately performed using the outside of the period of the SP for transmitting other data. That is, in a case of confirming the presence of the RTA data #3 as the undelivered data, the transmission-side communication device 10Tx immediately retransmits the undelivered RTA data #3. Note that, here, the reception may be confirmed by returning a block ACK frame as necessary. The transmission-side communication device 10Tx is configured to transmit desired RTA data #4 to #7 in the next R-TWT SP.

[0044] Furthermore, here, in a case where the RTA data #6 and #7 do not correctly arrive at the reception-side communication device 10Rx, the situation is returned to the transmission-side communication device 10Tx through, for example, a block ACK frame. Also in this case, the retransmission of the RTA data is configured to immediately perform the retransmission using a period other than the period of the SP for transmitting the other data, and for example, the RTA data #6 and #7 which are the undelivered data are configured to be retransmitted.

[0045] In this case, in the reception-side communication device 10Rx, although the data up to the RTA data #5 is in a state of being delivered without delay, the RTA data #6 that has not been delivered is also immediately retransmitted. Therefore, as indicated by an arrow D2 in the drawing, the data is delivered with a slight delay that has little influence on the connected application device. That is, all the data to be collected by the previous R-TWT SP is brought into an arrived state before the next R-TWT SP arrives, so that the reception-side communication device 10Rx can output the data without delay to the connected application device. Further, the subsequent RTA data #7 is continuously output to the connected application device, so that the output delay once generated is recovered as time passes. As a result, a data retransmission scheme (retransmission method) suitable for the real-time application is obtained.

[0046] Figs. 11A and 11B are diagrams illustrating a configuration example of a downlink R-TWT SP according to the present disclosure. Figs. 11A and 11B illustrate an example in which the access point (AP) is set as the transmission-side communication device 10Tx in the upper stage illustrated in Fig. 11A and the communication terminal (STA) is set as the reception-side communication device 10Rx in the lower stage illustrated in Fig. 11B, as a diagram in which time elapses from the left side to the right side in the diagram. In addition, in Figs. 11A and 11B, with respect to the time axis corresponding to the time direction, the signal to be transmitted is illustrated as an upward convex state, and the signal to be received is illustrated as a downward convex state, and the time of the R-TWT SP necessary for communicating the desired RTA data is illustrated by a broken line.

[0047] That is, the time during which the predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P1 indicated by a broken line. Here, the transmission-side communication device 10Tx is configured to transmit the downlink RTA data (DL RTA Data) from the access point (AP) according to a predetermined access procedure, and return an acknowledgment of receipt from the reception-side communication device 10Rx by a block ACK frame (BA).

[0048] In the case of this example, in a case where there is undelivered data, the undelivered data is retransmitted using a timing outside the period of the R-TWT SP, and the presence of the undelivered data is confirmed again by receiving a return of a block ACK frame (BA) as necessary. Then, in a case where there is data yet to be delivered, the data (Resend DL RTA Data) is immediately retransmitted outside the period of the R-TWT SP by a predetermined access procedure. In addition, since transmission of other general data (Normal Data) is also possible at a timing outside the period of the R-TWT SP, it may be possible to enable or disable retransmission of the RTA data according to the presence or absence of demand for these data.

[0049] Figs. 12A and 12B are diagrams illustrating a configuration example of an uplink R-TWT SP according to the present disclosure. Since Figs. 12A and 12B are described in a manner similar to Figs. 11A and 11B, redundant description will be appropriately omitted. In Figs. 12A and 12B, a time during which the predetermined RTA data can be transmitted in one R-TWT SP is indicated by a period P1 indicated by a broken line.

[0050] Here, a predetermined trigger frame (UL RTA Trigger) is transmitted from the access point (AP), so that the communication terminal (STA) serving as the transmission-side communication device 10Tx transmits the uplink RTA data (UL RTAData) according to a predetermined access procedure, and returns a block ACK frame (BA) and a trigger frame (Resend UL RTA Trigger (RT)) for retransmission of the RTA data from the access point (AP) serving as the reception-side communication device 10Rx in response to an acknowledgment of receipt of the uplink RTA data (UL RTAData).

[0051] Then, in a case where the communication terminal (STA) to be the transmission-side communication device 10Tx is requested to retransmit the RTA data, the communication terminal retransmits the undelivered data at a timing outside the period of the R-TWT SP (Resend UL RTA Data). Furthermore, the access point (AP) serving as the reception-side communication device 10Rx returns a block ACK frame as necessary. At this time, if retransmission is not necessary, the trigger frame (RT) for retransmission is not transmitted. In addition, at these timings, transmission of other general data (Normal Data) is also possible, and a configuration for effectively utilizing the transmission path can be obtained.

[0052] Fig. 13 is a diagram illustrating a configuration example of a buffer in a case where the RTA data is transmitted using the R-TWT SP. In Fig. 13, a buffer for a real-time application (RTA) is provided in addition to a related-art buffer for each main access category (AC: Access Category). Alternatively, Voice, which is a related-art highest priority buffer, may be used as a buffer for RTA data, and a related-art buffer for video data may be configured as a data buffer for Voice and Video.

[0053] <Configuration example of wireless communication device> Fig. 14 is a block diagram illustrating a configuration example of a wireless communication device to which the present disclosure is applied. In Fig. 14, the wireless communication device 10 includes a network module 11, an input module 12, a control module 13, an output module 14, and a wireless communication module 15.

[0054] The network module 11 performs various processing related to Internet connection under the control of the control module 13. For example, in a case of operating as an access point (AP), the network module 11 has a configuration in which a function such as a communication modem for connecting to an Internet network is mounted, and has a configuration in which Internet connection is performed through a public communication line and an Internet service provider.

[0055] The input module 12 has a function of inputting instruction information corresponding to an instruction from the user to the control module 13. The input module 12 includes, for example, an input device such as a push button, a keyboard, or a touch panel.

[0056] The control module 13 controls each unit (module) to operate the wireless communication device 10 as an access point (AP) or a communication terminal (STA). The control module 13 exchanges necessary information (data) with each unit (module). The control module 13 includes, for example, a control device such as a microprocessor or a microcontroller, a storage device such as a semiconductor memory, and the like.

[0057] The output module 14 has a function of displaying necessary information to the user on the basis of the information supplied from the control module 13. Here, the information displayed and informed by the output module 14 includes, for example, an operation state of the wireless communication device 10, information obtained through the Internet network, and the like. The output module 14 includes, for example, a display element such as a liquid crystal display, an organic EL display, or a light emitting diode (LED) display, or an output device including a speaker that outputs sound or music.

[0058] The wireless communication module 15 performs various processing related to wireless communication under the control of the control module 13. The wireless communication module 15 includes, for example, a wireless communication chip, a peripheral circuit, a control device such as a microcontroller, a storage device such as a semiconductor memory, and the like. Details of the configuration of the wireless communication module 15 will be described later with reference to Fig. 15.

[0059] In Fig. 14, the network module 11, the control module 13, and the wireless communication module 15 configure a control unit 21, the input module 12 configures an input unit 22, and the output module 14 configures an output unit 23. The output unit 23 includes an application device on which a real-time application is operated, and the application device includes a display or the like. The application device is controlled by the control unit 21. The control unit 21 may be regarded as a wireless communication device to which the present disclosure is applied. That is, the wireless communication device to which the present disclosure is applied may include the control unit 21 and be connected to the input unit 22 and the output unit 23.

[0060] Note that, in the wireless communication device 10, the control module 13 and the wireless communication module 15 are essential components, but whether or not the network module 11, the input module 12, and the output module 14 excluding the control module and the wireless communication module are included in the components is arbitrary. That is, each wireless communication device 10 operating as an access point (AP) or a communication terminal (STA) can be configured with only necessary modules, and unnecessary portions may be simplified or not incorporated. For example, in the wireless communication device 10 of Fig. 14, the network module 11 may be incorporated only in an access point (AP), and the input module 12 and the output module 14 may be incorporated only in a communication terminal (STA). In the wireless communication module 15, whether or not to include an antenna is optional. The wireless communication device 10 illustrated in Fig. 14 corresponds to both the transmission-side communication device 10Tx on the data transmission side and the reception-side communication device 10Rx on the data reception side.

[0061] Fig. 15 is a block diagram illustrating a configuration example of the wireless communication module 15 in Fig. 14. The wireless communication module 15 includes an interface 101 that is connected to another module and exchanges various types of information and data, a transmission buffer 102 that temporarily stores data to be transmitted, an RTA data management unit 103 that manages data (RTA data) of a series of real-time application (RTA) according to the present disclosure, and a data frame construction unit 104 that constructs a data frame (for example, the RTA data frame of Fig. 21 to be described below) at a predetermined timing. While the present disclosure uses the term “unit” and “module” it should be understood that in this context of data / signal processing, the “unit” and / or “module” may be implemented in circuitry. The circuitry may be programmable circuitry such as one or more CPUs configured by execution of computer readable instructions (code). The circuitry may also be implemented in hardwire configurations (e.g., ASIC), or a hybrid of programmable circuitry and hardwired circuitry.

[0062] The wireless communication module 15 includes a transmit opportunity control unit 105 that manages a transmit opportunity (TXOP: Transmit Opportunity) for periodically transmitting RTA data, and a control frame setting unit 106 that constructs a control frame such as a block ACK frame (for example, an RTA block ACK frame in Fig. 23 to be described below) or a trigger frame (for example, the RTA Trigger frame of Fig. 20 described below). Furthermore, the wireless communication module 15 includes a transmission signal processing unit 107 that performs encoding processing of data to be transmitted, an access control unit 108 that performs access control necessary for transmission of a frame, and an antenna unit 109 that transmits a transmission signal from the transmission signal processing unit 107 as a radio signal. Here, the transmission control of the RTA data is performed on the basis of the control of the access control unit 108, and the state of the transmission path can be sequentially monitored and used.

[0063] Furthermore, the wireless communication module 15 includes a reception signal processing unit 110 that extracts information configured as a frame from a reception signal received as a radio signal through the antenna unit 109, a control frame determination unit 111 that extracts information included in a trigger frame or a block ACK frame from each frame extracted by the reception signal processing unit 110, and a data frame analysis unit 112 that extracts data such as RTA data from the received data frame. Then, the wireless communication module 15 further includes an RTA data output timing control unit 113 that controls a timing of outputting the received RTA data to the connected application device, and a receive buffer 114 that temporarily stores the received data.

[0064] Note that, in the configuration illustrated in Fig. 15, an arrow between each block represents a flow and control of data (signal), and each block operates in cooperation with another block connected by the arrow in order to realize its own function. For example, the RTA data management 103 operates in cooperation with each of the transmit opportunity control unit 105 and the RTA data output timing control unit 113 in order to realize a function of managing a series of RTA data according to the present disclosure. In addition, the RTA data output timing control unit 113 operates in cooperation with each of the RTA data management 103, the transmit opportunity control unit 105, and the data frame analysis unit 112 in order to realize a function of controlling a timing of outputting the RTA data to the application device.

[0065] <Example of sequence> Fig. 16 is a diagram illustrating a first example of the exchange sequence of the setup request frame of the RTA data exchange. The exchange sequence of Fig. 16 is used to exchange parameters used to notify each other of, for example, setting of a service period (SP) of R-TWT, a retransmission scheme, and the like in advance between both wireless communication devices in a case where the parameters related to the RTA data are exchanged from the transmission-side communication device 10Tx to the reception-side communication device 10Rx.

[0066] In the example of Fig. 16, first, the transmission-side communication device 10Tx notifies the reception-side communication device 10Rx of the requested parameter, and the reception-side communication device 10Rx returns an agreeable parameter to the transmission-side communication device 10Tx on the basis of the request, so that the parameters regarding transmission and reception of the RTA data agreed by both sides are set on both sides.

[0067] First, a parameter setup request (Real Time Parameter Setup Request) related to the transmission of the RTA data is transmitted from the transmission-side communication device 10Tx (S11). Then, the reception-side communication device 10Rx that has received the setup request acquires the parameter described therein, and returns a setup response (Real Time Parameter Response) describing a response of the parameter regarding reception (S12). In this manner, a setting cycle and a duration of the service period (SP) of the R-TWT are set on the basis of the parameters agreed on by both communication devices, and further, the operation related to the retransmission of the RTA data according to the present disclosure is agreed.

[0068] Fig. 17 is a diagram illustrating a second example of the exchange sequence of the setup request frame of the RTA data exchange. Contrary to the exchange sequence of Fig. 16, the exchange sequence of Fig. 17 is used to exchange parameters used to notify each other of the setting of the service period (SP) of the R-TWT, the retransmission scheme, and the like in advance between both wireless communication devices in a case where the parameters related to the RTA data are exchanged from the reception-side communication device 10Rx to the transmission-side communication device 10Tx.

[0069] First, a parameter setup request (Real Time Parameter Setup Request) related to the transmission of the RTA data is transmitted from the reception-side communication device 10Rx (S21). Then, the transmission-side communication device 10Tx that has received the setup request acquires the parameters described therein, and returns a setup response (Real Time Parameter Response) describing a response of the parameters related to transmission (S22). In this manner, a setting cycle and a duration of the service period (SP) of the R-TWT are set on the basis of the parameters agreed on by both communication devices, and further, the operation related to the retransmission of the RTA data according to the present disclosure is agreed.

[0070] <Frame configuration> Fig. 18 is a diagram illustrating a configuration of a setup request element of an access control parameter of RTA data according to the present disclosure. The setup request element is configured as a kind of information element, and may be exchanged at the time of association, for example, or may be configured as a part of an action frame so as to be exchanged at an arbitrary timing.

[0071] As illustrated in Fig. 18, the setup request element of the access control parameter of the RTA data includes an Element ID indicating the format of the element, a Length indicating the information length of the element, an RTA Access Control Setup Element including the access control parameter of the actual RTA data, and a CRC (Cyclic Redundancy Check) which is an error detection code added as necessary.

[0072] In the setup request element, the content of the RTA Access Control Setup Element is configured to describe and transmit a parameter desired by the communication device on the requesting side, and finally determine the parameter agreed on by the communication device on the responding side.

[0073] As illustrated in Fig. 18, the RTA Access Control Setup Element includes parameters such as a Reservation Type indicating a reservation setting method, a TID indicating a traffic identifier for individually identifying RTA data, a Reservation Start Time indicating a reservation start time, a Reserve Duration indicating a duration of reservation, a Reserve Interval indicating a reservation interval, a Buffer Size indicating a buffer size, a queue size indicating a buffer queue size, an Output Delay indicating an output delay amount, an ACK Policy indicating necessity of returning a block ACK as a method of acknowledgment of receipt, and an RTA Resend indicating a data retransmission scheme. Output Delay describes an allowable delay amount of the RTA data to the application device according to the present disclosure. RTA Resend describes a retransmission scheme of RTA data according to the present disclosure.

[0074] Fig. 19 is a diagram illustrating a configuration of a setup response element of an access control parameter of RTA data according to the present disclosure. The setup response element is configured as a kind of information element, and may be exchanged at the time of association, for example, or may be configured as a part of an action frame so as to be exchanged at an arbitrary timing, and is configured to be returned as a response to the method sent as the setup request element.

[0075] As illustrated in Fig. 19, the setup response element of the access control parameter of the RTA data includes an Element ID indicating the format of the element, a Length indicating the information length of the element, an RTA Access Control Setup Element including the access control parameter of the actual RTA data, and a CRC which is an error detection code added as necessary.

[0076] In the setup response element, the content of the RTA Access Control Setup Element is configured to receive a frame in which a desired parameter is described from the communication device on the requesting side, finally determine a parameter supportable by the communication device on the responding side from these parameters, and return the parameter as a response frame.

[0077] As illustrated in Fig. 19, the RTA Access Control Setup Element includes parameters such as a Reservation Type indicating a reservation setting method, a TID indicating a traffic identifier for individually identifying RTA data, a Reservation Start Time indicating a reservation start time, a Reserve Duration indicating a duration of reservation, a Reserve Interval indicating a reservation interval, a Buffer Size indicating a buffer size, a queue size indicating a buffer queue size, an Output Delay indicating an output delay amount, an ACK Policy indicating necessity of returning a block ACK, and an RTA Resend indicating a data retransmission scheme. Output Delay describes an allowable delay amount of the RTA data to the application device according to the present disclosure. RTA Resend describes a retransmission scheme of RTA data according to the present disclosure.

[0078] Fig. 20 is a diagram illustrating a configuration example of a trigger frame (hereinafter, also referred to as RTA trigger frame) according to the present disclosure. In the present disclosure, as the configuration of the trigger frame specialized for the RTA data, the retransmission scheme is described and transmitted, so that, for example, the retransmission scheme related to the transmission of the RTA data (UL RTA Data) in the uplink direction (UL) can be informed. For example, in a case where a transmit opportunity (TXOP) is acquired by the R-TWT SP or the like, when the low latency RTA data is transmitted and received, the transmission from the transmission-side communication device 10Tx associated with the traffic identifier (TID) designated in the RTA data is designated by the RTA trigger frame, for example, by an association identifier (AID).

[0079] As illustrated in Fig. 20, the RTA trigger frame includes Frame Control indicating a predetermined frame format, Duration indicating duration, RA (Receive Address) indicating reception address information, TA (Transmit Address) indicating transmission address information, Common Info indicating common information of the trigger frame, User Info List indicating individual information for each user in the trigger frame, Padding added as necessary, and FCS which is a frame check sequence for error detection.

[0080] UserInfo List has a configuration in which UserInfo is described for each user, and the UserInfo includes an AID12 that recognizes a target communication device, RU Allocation indicating a resource unit used for communication, UL FEC Coding Type indicating a coding format of uplink communication, UL HE-MCS and UL-DMC indicating an encoding scheme of uplink communication, SS Allocation / RA-RU Info indicating spatial multiple allocation or random access resource unit, UL Target Receive Power indicating received power of an uplink target, and the like. In addition, Reserved indicating reservation for future extension is secured, and further, Trigger Dependent User Info is added as necessary as user information dependent on the trigger.

[0081] In Fig. 20, RTA Resend describing the retransmission scheme of the RTA data according to the present disclosure is newly set as the configuration of User Info of the RTA trigger frame. That is, the presence or absence of retransmission of the RTA data can be informed by the parameter described in RTA Resend. Furthermore, Fig. 20 also illustrates a configuration of Common Info of the RTA trigger frame.

[0082] Fig. 21 is a diagram illustrating a configuration example of a data frame (hereinafter, also referred to as an RTA data frame) according to the present disclosure. In Fig. 21, the retransmission scheme of the RTA data is informed using the header information of the RTA data frame. Specifically, as a frame configuration of an A-MPDU (Aggregate-MPDU) which is an aggregated MAC protocol data unit (MPDU), information regarding a retransmission scheme of the RTA data is described in specific MPDU data.

[0083] As illustrated in Fig. 21, the A-MPDU has a configuration in which a plurality of MPDUs is continuously transmitted through a delimiter (D). In the present disclosure, an RTA Resend flag is set in a portion of QoS Control in a MAC header portion of an MPDU that is a subframe configuring the A-MPDU, and in a case where the RTA Resend flag is set, retransmission of the RTA MPDU subsequent to the MAC header is performed. That is, in a case where RTA data that requires retransmission is included, this bit is set, and if this bit is not set, it can be recognized that the RTA data does not require retransmission. Then, an FCS is added to the MPDU to determine whether or not there is an error in the MPDU. With such a configuration, it is possible to use traffic for other data transmission by preventing retransmission of unnecessary RTA data in advance.

[0084] Fig. 22 is a diagram illustrating a configuration example of a delimiter of a data frame according to the present disclosure. In Fig. 22, the retransmission scheme is informed using the delimiter information of the RTA data frame. Specifically, in place of or in combination with the RTA Resend information described in the MAC header illustrated in Fig. 21, the retransmission scheme is notified using a specific bit of the delimiter (D) of the A-MPDU.

[0085] As illustrated in Fig. 22, an RTA Resend flag is set in the delimiter, and in a case where the RTA Resend flag is set, retransmission of the RTA data is performed. In the case of such a method for notifying the retransmission scheme using the delimiter, even in a case where a bit error occurs in the MAC header portion and the last FCS is not correctly decoded, it is possible to obtain a method capable of avoiding the risk.

[0086] Fig. 23 is a diagram illustrating a configuration example of a block ACK frame (hereinafter, also referred to as an RTA block ACK frame) according to the present disclosure. In Fig. 23, the RTA block ACK frame has a configuration similar to that of the related-art block ACK frame in order to maintain compatibility. As illustrated in Fig. 23, the RTA block ACK frame includes Frame Type indicating the type of a predetermined frame, Duration indicating the duration of the frame, RA indicating address information for identifying the reception-side communication device, TA indicating address information for identifying the transmission-side communication device, BA Control in which a control parameter of the block ACK frame is described, and FCS for detecting an error of the frame in BA Information in which sequence number information capable of specifying data to be retransmitted is described.

[0087] As illustrated in Fig. 23, in a case where the bit of the RTA Resend Request of BA Control is set, the RTA block ACK frame indicates that information that can specify (identify) RTA data which needs to be retransmitted is described in the following BA Information. BA Information, Resend RTA Data Starting Sequence Number indicating a first sequence number for requesting retransmission, Next Sequence Number indicating a sequence number to be transmitted in the next R-TWT SP, and Resend Request Sequence Bitmap in which a sequence number requiring retransmission is described in bitmap format.

[0088] That is, in a case where there is a grace in the timing of output to the application device, it is possible to specify the RTA data to be retransmitted and request retransmission. On the other hand, in a case where there is no grace in the timing of output to the application device, it is possible to handle the data as data that does not require retransmission and to obtain a method of preventing unnecessary retransmission in advance. As a result, the transmission-side communication device 10Tx that has received the RTA block ACK frame can specify the RTA data that needs to be retransmitted from the block ACK frame. Note that the reception-side communication device may be configured to transmit the RTA block ACK frame in a case of receiving a frame including a traffic identifier (TID) for retransmitting the undelivered RTA data outside the period of the R-TWT SP.

[0089] <Flow of setup information exchange> A flow of the RTA parameter setup information exchange processing will be described with reference to the flowcharts of Figs. 24 and 25. In Figs. 24 and 25, one flowchart is illustrated such that both the wireless communication device 10 requesting setup and the wireless communication device 10 responding to setup operate.

[0090] First, both the wireless communication devices 10 acquire parameters for the RTA data (S101). Furthermore, both the wireless communication devices 10 determine whether or not setup of the RTA data is necessary (S102), and the wireless communication device 10 that requires setup performs the following processing in steps S103 to S107. That is, the target wireless communication device 10 calculates the requested RTA parameter from the amount of transmittable information per predetermined time, the information on the maximum allowable delay, a capacity of the buffer available for the RTA data, and the like (S103).

[0091] In addition, the target wireless communication device 10 periodically calculates an interval (Interval) of RTWTSP required to be secured as a transmit opportunity (TXOP) (S104), and also calculates a duration (Duration) to be secured as a transmit opportunity (TXOP) in one R-TWT SP (S105). The target wireless communication device 10 constructs an RTA setup request frame (for example, a frame including the setup request element of Fig. 18) in which the calculated request parameter is described, and transmits the RTA setup request frame to a counterpart wireless communication device 10 (S106). Note that the target wireless communication device 10 may be configured to be able to transmit the setup request not only in a case of operating as the transmission-side communication device 10Tx that transmits the RTA data but also in a case of operating as the reception-side communication device 10Rx that receives the RTA data.

[0092] Then, in a case of receiving the RTA setup response frame (for example, a frame including the setup response element of Fig. 19) from the counterpart wireless communication device 10 (S107: Yes), the target wireless communication device 10 reads a parameter that can be set by the counterpart wireless communication device 10 and sets the parameter as an agreed RTA reservation parameter (S108). The processing in step S108 ends, and then a series of processing ends. On the other hand, in a case where the RTA setup response frame has not been received by the predetermined response time, the processing returns to step S102, and the target wireless communication device 10 may review the parameter request setting again and retransmit the RTA setup request frame.

[0093] On the other hand, in a case where it is determined not to issue the setup request in the determination of step S102, the processing proceeds to step S109 of Fig. 25. Then, in a case of receiving the RTA setup request frame from the other wireless communication device 10 (S109: Yes), the target wireless communication device 10 acquires the RTA parameter described in the frame (S110). The RTA parameter acquired here is an RTA parameter requested by the counterpart wireless communication device 10. The target wireless communication device 10 determines whether or not the RTA parameter can be set on the basis of the RTA parameter acquired from the frame and its own RTA parameter (S111).

[0094] In a case where it is determined that the RTA parameter can be set (S111: Yes), in the target wireless communication device 10, the processing of the following steps S112 to S115 is performed. That is, the target wireless communication device 10 periodically sets an interval (Interval) of the R-TWT SP that needs to be secured as the transmit opportunity (TXOP) (S112), and also sets a duration (Duration) that can be processed in one transmit opportunity (TXOP) (S113). The target wireless communication device 10 constructs an RTA setup response frame in which the set response parameter is described, and transmits the RTA setup response frame to the counterpart wireless communication device 10 (S114). In addition, the target wireless communication device 10 sets the parameter as an agreed RTA reservation parameter (S115). The processing of step S115 ends, and then a series of processes ends. Note that in a case where the RTA setup request frame is not received (S109: No) or in a case where it is determined that the RTA parameter cannot be set (S111: No), the processing is terminated and the series of processes is terminated. With the performance of this setup information exchange, it is possible to set, as the R-TWT SP, a service period (SP) which is a minimum necessary transmit opportunity (TXOP) for the RTA data.

[0095] <Flow of Transmission Processing> A flow of transmission processing by the transmission-side communication device 10Tx will be described with reference to the flowcharts in Figs. 26 and 27.

[0096] The transmission-side communication device 10Tx determines whether or not it is within the period of the R-TWT SP that operates regularly (S201). In a case of determining that the current time is within the period of the R-TWT SP (S201: Yes) and determining that the transmission path is available in the idle state (S202: Yes), the transmission-side communication device 10Tx performs the processes of subsequent steps S203 to S208.

[0097] That is, the transmission-side communication device 10Tx acquires the remaining time of the R-TWT SP (S203) and acquires the RTA data (S204). Further, the transmission-side communication device 10Tx acquires the output timing parameter of the RTA data in the reception-side communication device 10Rx (S205), and in a case where it is determined that the RTA data can be retransmitted (S206: Yes), the transmission-side communication device sets the retransmittable parameter (S207). Here, in a case where there is a margin for recovery by performing retransmission even if the RTA data is not delivered after the RTA data is transmitted, it is determined that the RTA data can be retransmitted, and a flag indicating the retransmittable parameter can be set as, for example, header information. Note that in a case where it is determined that the retransmission of the RTA data is not possible (S206: No), the setting of the retransmittable parameter is skipped. Then, the transmission-side communication device 10Tx transmits the RTA data frame (Fig. 21) (S208). The processing of step S208 ends, and then the processing returns to step S201. In this manner, the transmission-side communication device 10Tx can transmit the RTA data acquired at that time within the period of the R-TWT SP.

[0098] In a case where it is determined in step S202 that the transmission path is not in the idle state and is not available (S202: No), the processing proceeds to step S209 in Fig. 27. When receiving the RTA block ACK frame (Fig. 23) from the reception-side communication device 10Rx after transmitting the RTA data frame (S209: Yes), the transmission-side communication device 10Tx acquires the ACK parameter described in the frame (S210). In a case where it is determined that there is no undelivered data with reference to the ACK parameter (S211: No), the transmission-side communication device 10Tx exits the processing and ends the series of processing. On the other hand, in a case where it is determined that there is undelivered data (S211: Yes), the processing of the following steps S212 to S215 is performed. The undelivered data is the undelivered RTA data among the transmitted RTA data. For example, the transmission-side communication device 10Tx can determine whether or not there is undelivered data by specifying data of an ID that has not been received by the reception-side communication device 10Rx among the IDs informed in advance or missing data among data to be continuously received.

[0099] That is, the transmission-side communication device 10Tx acquires the output timing parameter in the reception-side communication device 10Rx for the RTA data to be retransmitted described in the ACK parameter (S212), and determines whether or not the output timing has a time grace (S213). Then, in a case where it is determined that there is a grace in the output timing (S213: Yes), the transmission-side communication device 10Tx acquires RTA data to be retransmitted (S214), performs processing related to retransmission of the acquired RTA data outside the period of the R-TWT SP (S215), and transmits an RTA data frame including the RTA data to be retransmitted outside the period of the R-TWT SP (S208). That is, the transmission-side communication device 10Tx can retransmit the undelivered RTA data in a period (a period outside the period of R-TWT SP) in which the predetermined delay is within the allowable time according to the output timing in the reception-side communication device 10Rx. Note that, here, the RTA data to be retransmitted is retransmitted outside the period of the R-TWT SP, but it may be understood that an end time of the R-TWT-SP secured as a transmit opportunity is extended and the RTA data is retransmitted in the extended period.

[0100] On the other hand, in a case where it is determined that there is no grace in the output timing (S213: No), the processing exits without acquiring the RTA data to be retransmitted, and the processing returns to step S201 in Fig. 26. On the other hand, in a case where the RTA block ACK frame is not received (S209: No), when another frame is received (S216: Yes), the reception processing of the another frame is performed (S217). For example, in a case where a data frame addressed to the own device is received, the reception processing of the data frame is performed. That is, the transmission-side communication device 10Tx can operate to transmit the RTA data in response to the request in a case where the trigger frame of the RTA data is received from the reception-side communication device 10Rx as a counterpart during the R-TWT SP period, and operate to receive the data even in a case where the data frame addressed to itself is received from another wireless communication device.

[0101] In a case where the processing in step S217 ends or no other frame is received (S216: No), the processing returns to step S201 in Fig. 26. Then, a series of operations is repeated until the period of the R-TWT SP continues.

[0102] <Flow of Reception Processing> A flow of reception processing by the reception-side communication device 10Rx will be described with reference to flowcharts in Figs. 28 and 29.

[0103] In a case of receiving the RTA data frame addressed to the reception reception-side communication device 10Rx transmitted from the transmission-side communication device 10Tx (S301: Yes), the reception-side communication device 10Rx acquires the RTA data that could be received (S302). The reception-side communication device 10Rx determines whether or not there is a request for returning an ACK frame (S303), and in a case where it is determined that it is necessary to return an ACK frame (S303: Yes), constructs an ACK frame in which an ACK parameter is described (S304). Further, the reception-side communication device 10Rx determines whether or not there is an error in the RTA data transmitted from the transmission-side communication device 10Tx (S305). In a case where it is determined that the RTA data includes an error (S305: Yes), the reception-side communication device specifies the undelivered data (S307), and acquires a parameter of a timing to be output to the connected application device (S306).

[0104] Then, the reception-side communication device 10Rx determines whether or not there is a time grace in the output timing (S308), and in a case where it is determined that there is no time grace in the output timing (S308: No), the processing proceeds to step S313 in Fig. 29. Alternatively, also in a case where it is determined that no error is included in the RTA data (S305: No), the processing proceeds to step S313 of Fig. 29. In this case, the reception-side communication device 10Rx transmits the constructed ACK frame as it is as a response frame (S313). On the other hand, in a case where it is determined that there is a grace in the output timing (S308: Yes), the processing proceeds to step S309 in Fig. 29. That is, in a case where there is a grace for the output timing, the reception-side communication device 10Rx determines that the RTA data can be retransmitted, sets a retransmission request for the RTA data as necessary (S309), and acquires the remaining time of the R-TWT SP (S310).

[0105] The reception-side communication device 10Rx determines whether or not the period of the R-TWT SP is exceeded on the basis of the remaining time of the R-TWT SP (S311), and in a case of determining that the period of the R-TWT SP is exceeded (S311: Yes), performs processing related to retransmission outside the period of the R-TWT SP (S312). Then, the reception-side communication device 10Rx transmits an RTA block ACK frame (Fig. 23) as a response frame (S313). For example, in a case where the undelivered data is specified and the output timing has a grace, when the period of the R-TWT SP is exceeded (outside the period of the R-TWT SP), the undelivered RTA data is retransmitted by the transmission-side communication device 10Tx, so that the reception-side communication device 10Rx performs a process of receiving the RTA data retransmitted outside the period of the R-TWT SP. Note that, in a case where the end time of the R-TWT-SP secured as a transmit opportunity is extended and the RTA data is to be retransmitted, when the remaining time of the R-TWT SP is less than the time to end retransmission, the duration of the R-TWT SP may be extended and the end time may be extended to transmit the RTA block ACK frame as a response frame. Also, in a case where it is determined that the period of the R-TWT SP has not been exceeded (a case where it is determined that extension of the R-TWT SP is not necessary), the RTA block ACK frame is transmitted as a response frame (S313).

[0106] On the other hand, in a case where it is determined in step S301 that the RTA data frame has not been received (S301: No), the processing proceeds to step S314 in Fig. 29. The reception-side communication device 10Rx determines whether or not a range of the period of the R-TWT SP is exceeded (S314), and in a case where it is determined that the range of the period of the R-TWT SP is exceeded (S314: Yes), when it is determined that there is undelivered RTA data (S315: Yes), the processing returns to step S301 and continues the RTA data receiving process. Note that, in a case where the reception-side communication device 10Rx operates as, for example, an access point (AP) and operates as a transmit opportunity (TXOP) holder of the R-TWT SP, the reception-side communication device 10Rx may operate to receive the RTA data after transmitting the trigger frame as necessary to urge the transmission-side communication device 10Tx to transmit the RTA data addressed to itself.

[0107] Alternatively, in a case where it is determined in the determination of step S314 that the range of the period of the R-TWT SP is not exceeded (S314: No), the processing returns to step S301, and the reception of a series of RTA data is waited. On the other hand, in a case where it is determined that the period of the R-TWT SP is exceeded (S314: Yes), when it is determined that there is no undelivered RTA data (S315: No), or when it is determined that it is not necessary to return the ACK frame (S303: No), the reception processing of the RTA data in the target R-TWT SP is ended.

[0108] As described above, under the control of the control unit 21 in Fig. 14, the transmission-side communication device 10Tx of the present disclosure can transmit data (for example, RTA data such as the RTA data frame in Fig. 21) to the reception-side communication device 10Rx, receive the retransmission request information (for example, the RTA block ACK frame in Fig. 23) transmitted from the reception-side communication device 10Rx, and retransmit, to the reception-side communication device 10Rx, the undelivered data specified by the received retransmission request information and among the transmitted data, the undelivered data according to the output timing of outputting the data to the application device (the application device included in the output unit 23 in Fig. 14) connected in the reception-side communication device 10Rx.

[0109] In addition, under the control of the control unit 21 in Fig. 14, the reception-side communication device 10Rx of the present disclosure can receive the data transmitted from the transmission-side communication device 10Tx (for example, the RTA data such as the RTA data frame in Fig. 21), adjust the output timing of outputting the received data to the connected application device (the application device included in the output unit 23 in Fig. 14), generate retransmission request information (for example, the RTA block ACK frame in Fig. 23) for requesting retransmission of the undelivered data, which is the data that has not been delivered among the transmitted data, according to the output timing, and transmit the generated retransmission request information to the transmission-side communication device 10Tx.

[0110] That is, in the present disclosure, the necessity of retransmission of the undelivered data is determined according to the output timing at which the RTA data is output to the application device connected in the reception-side communication device 10Rx, and the undelivered data is retransmitted at the retransmittable timing, thereby improving the utilization efficiency of the transmission path. As a result, even when there is undelivered data, the reception-side communication device 10Rx can suppress a delay until the RTA data is output to the application device.

[0111] Further, in the present disclosure, since the retransmission data is retransmitted in a period (a second period different from the first period) different from the service period of the transmit opportunity determined in advance, that is, (a period of) outside the period of the set R-TWT SP, the minimum necessary R-TWT SP can be set and reused for other data transmission. Furthermore, since the reception-side communication device 10Rx manages the return of the ACK frame and the return request, the reception-side communication device 10Rx side can determine the necessity of retransmission adaptively to the grace of the output timing. With adjustment of the output timing of the RTA data that has arrived at the reception-side communication device 10Rx to the application device, it is possible to appropriately recover even if a delay occurs due to retransmission.

[0112] Note that, as described above, the R-TWT technology is defined as a technology that determines a time for activating a target existing in the related art and activates the target to realize a low power consumption operation, and is defined as a mechanism in which a transmission-side communication device periodically acquires a transmit opportunity (TXOP) and preferentially transmits data to be transmitted as a low latency in the transmit opportunity (TXOP) over other data. That is, a technology has been proposed in which a traffic identifier (TID) associated with a transmission-side communication device and a reception-side communication device is defined, and only data of the identifier is preferentially transmitted in a case where a transmit opportunity (TXOP) arrives at a predetermined cycle. The R-TWT technology is regarded as a technique for transmitting data suitable for real-time applications, and technical proposals using these techniques have been currently made.

[0113] These R-TWT technologies are defined in order for the transmission-side communication device and the reception-side communication device to operate in synchronization with each other at a predetermined cycle. However, it is necessary to set a service period (SP) of the R-TWT in order to define a certain cycle and to prioritize the communication. In a case where these techniques are applied to RTA data requiring a low latency, it is necessary to set parameters for completing transmission within an allowable delay time, and there is a problem that a transmission delay occurs unless an arrival period of the R-TWT SP is shortened. In addition, since a communication error occurs on the wireless transmission path, there has been a problem that all the data cannot be reliably delivered end-to-end unless the data in which the error occurs is retransmitted. In particular, in a case where a communication amount for performing the minimum necessary data transmission is secured by securing one transmit opportunity (TXOP) of the R-TWT SP, it has not been possible to perform retransmission of the undelivered data within the service period.

[0114] As currently assumed, when the transmission of the RTA data (data requiring a low latency) is limited to the R-TWT SP, there has been a problem that the transmission of the RTA data is delayed unless the next R-TWT SP arrives, and there has been a problem that the delay is accumulated. That is, if the undelivered data is accumulated and the data is retransmitted to solve the problem, the delay amount has tended to increase in the transmission of the RTA data, which was not preferable. Therefore, in order to secure a transmit opportunity (TXOP) in the R-TWT SP and retransmit data that has not been delivered due to a transmission error, it has been necessary to secure a service period (SP) including a redundant time. However, in this case, there has been a problem that a service period (SP) is set for specific wireless communication, and transmit opportunities (TXOP) for other general wireless communication are relatively reduced. In particular, in a case where retransmission is not necessary, it is necessary to release a redundant time secured as a service period (SP) and reuse the same for other general data communication.

[0115] Therefore, the present disclosure proposes the following wireless communication device and wireless communication method as a method for solving such a problem. In other words, a wireless communication device and a wireless communication method have been proposed in which, in a case where there is a grace in the output timing of the RTA data, the reception-side communication device performs retransmission of the undelivered data to reliably collect and output the data with a lower latency and more reliably. Furthermore, the present disclosure proposes a wireless communication device and a wireless communication method that, in a case where it is difficult to transmit RTA data within an R-TWT period scheduled to acquire a transmit opportunity (TXOP) at a predetermined cycle, perform retransmission of the RTA data with a low latency beyond a range of the period. Furthermore, the present disclosure proposes a wireless communication device and a wireless communication method that output received RTA data so as not to cause a delay from a predetermined output timing of the RTA data.

[0116] With such a wireless communication device and a wireless communication method, for example, the following effects can be obtained. That is, it is determined whether or not retransmission of the RTA data is possible in accordance with the output timing of the reception-side communication device, so that it is possible to reduce the traffic required for retransmission of unnecessary data and to improve the utilization efficiency of the transmission path. Also, in the transmission-side communication device, the output timing is managed so that the RTA data can be delivered to the application device connected to the reception-side communication device with a low latency.

[0117] In the reception-side communication device, in a case where there is a margin in the output timing, the block ACK frame of the retransmission request is returned, so that retransmission of unnecessary RTA data can be prevented. In the reception-side communication device, in a case where there is no margin for the output timing, a method of efficiently using the transmission path can be obtained by not requesting retransmission. Even if there is undelivered data in the RTA data, the delay can be recovered by adjusting the output timing of the reception-side communication device by retransmitting the data at an arbitrary timing. The transmission-side communication device retransmits the RTA data beyond the service period of the R-TWT SP so that the RTA data can be delivered to the reception-side communication device with a low latency. In addition, the transmission-side communication device only needs to set a minimum service period of the R-TWT SP for desired RTA data with the reception-side communication device, and communication of other general data can be used together, so that utilization efficiency of the transmission path can be improved.

[0118] <Modifications> The series of processing steps described above can be executed by hardware and also can be executed by software. In a case where the series of processing is executed by software, a program configuring the software is installed from a program recording medium to a computer incorporated in dedicated hardware, a general-purpose personal computer (PC), or the like. For example, in a computer that executes the above-described series of processing by a program, a central processing unit (CPU) loads a program stored in a storage unit including a hard disk, a nonvolatile memory, or the like into a random access memory (RAM) and executes the program, whereby the above-described series of processing is performed. Note that the program executed by the computer may be a program in which processing is performed in time series in the order described in the present description, or may be a program in which processing is performed in parallel or at necessary timing such as when a call is made.

[0119] The present disclosure is applicable to various products. For example, in a case where the wireless communication device 10 is a communication terminal (STA), the wireless communication device may be configured as a mobile terminal such as a smartphone, a tablet PC, a notebook PC, a portable game terminal, or a digital camera, a fixed terminal such as a television receiver, a printer, a digital scanner, or a network storage, or an in-vehicle terminal such as a car navigation device. Furthermore, the wireless communication device 10 may be configured as a machine-to-machine communication (M2M) terminal such as a smart meter, a vending machine, a remote monitoring device, or a point of sale (POS) terminal. Furthermore, the wireless communication device 10 may be a wireless communication module (for example, an integrated circuit module including one die) mounted on these terminals.

[0120] Furthermore, for example, in a case where the wireless communication device 10 is an access point (AP), it may be configured as an AP (wireless base station) of a wireless LAN having a router function or not having a router function. Furthermore, the wireless communication device 10 may be configured as a mobile wireless LAN router. Furthermore, the wireless communication device 10 may be a wireless communication module (for example, an integrated circuit module including one die) mounted on these devices.

[0121] Note that embodiments of the present disclosure are not limited to the embodiments described above, and various modifications may be made without departing from the scope of the present disclosure. Furthermore, the effects described in the present description are merely examples and are not limited, and other effects may be provided.

[0122] Furthermore, the present disclosure can have the following configurations.

[0123] <Aspect 1> A reception-side wireless communication device comprising: circuitry configured to receive a first part of real-time application (RTA) information transmitted from a transmission-side communication device during a service period, detect a failure to properly receive a second part of RTA information transmitted from the transmission-side communication device during the service period, within the service period, transmit to the transmission-side communication device an indication that the first part of RTA was received properly, and after the service period has expired, receive the second part of the RTA as a retransmission from the transmission-side communication device. <Aspect 2> The reception-side wireless communication device of aspect 1, wherein the circuitry is further configured to transmit a predetermined trigger frame to urge the transmission-side communication device to retransmit the second part of RTA information. <Aspect 3> The reception-side wireless communication device of aspect 1, wherein the circuitry is further configured to receive the second part of the RTA information as the retransmission from the transmission-side communication device after the service period has expired and prior to a start of a next service period. <Aspect 4> The reception-side wireless communication device of aspect 3, wherein the circuitry is further configured to transmit an acknowledgement to the transmission-side communication device subsequent to reception of the retransmission of the second part of the RTA information. <Aspect 5> The reception-side wireless communication device of aspect 1, wherein the circuitry is further configured to exchange real time parameter setup information with the transmission-side communication device. <Aspect 6> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to receive a real time parameter setup request from the transmission-side communication device, and transmit a real time parameter response to the transmission-side communication device. <Aspect 7> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to transmit a real time parameter setup request to the transmission-side communication device, and receive a real time parameter response message from the transmission-side communication device. <Aspect 8> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to include in the real time parameter setup request an access control setup element message that includes an indication of a RTA resend capability. <Aspect 9> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to include in the access control setup element message at least one of a reservation type, a traffic identifier, reservation start time, reservation duration, reserve interval, buffer size, queue size, output delay, and ACK policy information. <Aspect 10> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to include in the real time parameter setup information RTA trigger frame information with user associated information. <Aspect 11> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to include the real time parameter setup information as part of QoS control information. <Aspect 12> The reception-side wireless communication device of aspect 5, wherein the circuitry is further configured to determine a RTA parameter from at least one of an amount of transmittable information per predetermined time, a maximum allowable delay, and a capacity of a buffer available for the RTA information. <Aspect 13> The reception-side wireless communication device of aspect 1, wherein the circuitry is further configured to determine whether there is a grace period after the service period. <Aspect 14> The reception-side wireless communication device of aspect 1, wherein the circuitry is further configured to determine whether to send a request to urge the transmission side communication device to retransmit the second part of RTA information based on whether a grace period exists after the service period. <Aspect 15> A transmission-side wireless communication device comprising: circuitry configured to transmit a first part of real-time application (RTA) information and a second part of RTA information to a reception-side communication device during a service period, within the service period, receive from the reception-side communication device an indication that the first part of RTA was received properly, and after the service period has expired, retransmit the second part of the RTA as a retransmission to the reception-side communication device. <Aspect 16> The transmission-side wireless communication device of aspect 15, wherein the circuitry is further configured to transmit the second part of the RTA information as the retransmission after the service period has expired and prior to a start of a next service period. <Aspect 17> The transmission-side wireless communication device of aspect 15, wherein the circuitry is further configured to exchange real time parameter setup information with the reception-side communication device. <Aspect 18> The transmission-side wireless communication device of aspect 15, wherein the circuitry is further configured to include in the real time parameter setup information RTA trigger frame information with user associated information. <Aspect 19> The transmission-side wireless communication device of aspect 15, wherein the circuitry is further configured to determine whether there is a grace period after the service period. <Aspect 20> A method executed by a reception-side wireless communication device, the method comprising: receiving a first part of real-time application (RTA) information transmitted from a transmission side communication device during a service period; detecting, with circuitry, a failure to properly receive a second part of RTA information transmitted from the transmission side communication device during the service period; within the service period, transmitting to the transmission side communication device an indication that the first part of RTA was received properly; and after the service period has expired, receiving the second part of the RTA as a retransmission from the transmission side communication device.

[0124] It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

[0125] 10 Wireless communication device 10Tx Transmission-side communication device 10Rx Reception-side communication device 11 Network module 12 Input module 13 Control module 14 Output module 15 Wireless communication module 21 Control unit 22 Input unit 23 Output unit 101 Interface 102 Transmission buffer 103 RTA data management unit 104 Data frame construction unit 105 Transmit opportunity control unit 106 Control frame setting unit 107 Transmission signal processing unit 108 Access control unit 109 Antenna unit 110 Reception signal processing unit 111 Control frame determination unit 112 Data frame analysis unit 113 RTA data output timing control unit 114 Reception buffer

Claims

1. A reception-side wireless communication device comprising: circuitry configured to receive a first part of real-time application (RTA) information transmitted from a transmission-side communication device during a service period, detect a failure to properly receive a second part of RTA information transmitted from the transmission-side communication device during the service period, within the service period, transmit to the transmission-side communication device an indication that the first part of RTA was received properly, and after the service period has expired, receive the second part of the RTA as a retransmission from the transmission-side communication device.

2. The reception-side wireless communication device of claim 1, wherein the circuitry is further configured to transmit a predetermined trigger frame to urge the transmission-side communication device to retransmit the second part of RTA information.

3. The reception-side wireless communication device of claim 1, wherein the circuitry is further configured to receive the second part of the RTA information as the retransmission from the transmission-side communication device after the service period has expired and prior to a start of a next service period.

4. The reception-side wireless communication device of claim 3, wherein the circuitry is further configured to transmit an acknowledgement to the transmission-side communication device subsequent to reception of the retransmission of the second part of the RTA information.

5. The reception-side wireless communication device of claim 1, wherein the circuitry is further configured to exchange real time parameter setup information with the transmission-side communication device.

6. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to receive a real time parameter setup request from the transmission-side communication device, and transmit a real time parameter response to the transmission-side communication device.

7. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to transmit a real time parameter setup request to the transmission-side communication device, and receive a real time parameter response message from the transmission-side communication device.

8. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to include in the real time parameter setup request an access control setup element message that includes an indication of a RTA resend capability.

9. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to include in the access control setup element message at least one of a reservation type, a traffic identifier, reservation start time, reservation duration, reserve interval, buffer size, queue size, output delay, and ACK policy information.

10. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to include in the real time parameter setup information RTA trigger frame information with user associated information.

11. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to include the real time parameter setup information as part of QoS control information.

12. The reception-side wireless communication device of claim 5, wherein the circuitry is further configured to determine a RTA parameter from at least one of an amount of transmittable information per predetermined time, a maximum allowable delay, and a capacity of a buffer available for the RTA information.

13. The reception-side wireless communication device of claim 1, wherein the circuitry is further configured to determine whether there is a grace period after the service period.

14. The reception-side wireless communication device of claim 1, wherein the circuitry is further configured to determine whether to send a request to urge the transmission side communication device to retransmit the second part of RTA information based on whether a grace period exists after the service period.

15. A transmission-side wireless communication device comprising: circuitry configured to transmit a first part of real-time application (RTA) information and a second part of RTA information to a reception-side communication device during a service period, within the service period, receive from the reception-side communication device an indication that the first part of RTA was received properly, and after the service period has expired, retransmit the second part of the RTA as a retransmission to the reception-side communication device.

16. The transmission-side wireless communication device of claim 15, wherein the circuitry is further configured to transmit the second part of the RTA information as the retransmission after the service period has expired and prior to a start of a next service period.

17. The transmission-side wireless communication device of claim 15, wherein the circuitry is further configured to exchange real time parameter setup information with the reception-side communication device.

18. The transmission-side wireless communication device of claim 15, wherein the circuitry is further configured to include in the real time parameter setup information RTA trigger frame information with user associated information.

19. The transmission-side wireless communication device of claim 15, wherein the circuitry is further configured to determine whether there is a grace period after the service period.

20. A method executed by a reception-side wireless communication device, the method comprising: receiving a first part of real-time application (RTA) information transmitted from a transmission side communication device during a service period; detecting, with circuitry, a failure to properly receive a second part of RTA information transmitted from the transmission side communication device during the service period; within the service period, transmitting to the transmission side communication device an indication that the first part of RTA was received properly; and after the service period has expired, receiving the second part of the RTA as a retransmission from the transmission side communication device.

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