Wireless communication method and computer program

Abstract

To improve reliability by using a reception acknowledgement while ensuring efficient use of wireless resources in multicast transmission of wireless transmission.SOLUTION: When a plurality of wireless communication devices included in a multicast group receive a multicast data frame, the devices simultaneously transmit reception acknowledgements of a multicast by using spatial multiplexing in response to a reception confirmation request from a transmission source. On the other hand, a wireless communication device of the transmission source separates and restores the simultaneously received reception acknowledgements into original individual reception acknowledgements by a signal process based on channel information with each wireless communication device of a transmission destination.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a wireless communication device that performs multicast transmission. [Background technology]

[0002] When it is desired to transmit the same data to a large number of wireless terminals, multicast, in which the bandwidth used does not depend on the number of destinations, is more effective than unicast in terms of resource utilization efficiency.

[0003] For example, the IEEE802.11 WLAN standard "IEEE Standard 802.11-2012" defines the basic protocol for multicast delivery. However, the protocol defined here does not allow for receipt confirmation from multiple devices, and it is not possible to improve communication quality by retransmission control using receipt confirmation.

[0004] In addition, the supplemental standard "IEEE802.11aa-2012" defines a multicast extension with receipt confirmation, which introduces the effect of improving communication quality by using receipt confirmation to control retransmission. However, in this extension method, multicast receipt confirmation is performed individually for each group member. For this reason, as the number of terminals transmitting multicast increases, the overhead of communication resource usage increases, which is a problem that limits the resource utilization efficiency, which is one of the advantages of multicast.

[0005] Also, a protection mechanism for multi-user MIMO communication has been proposed in which reservation messages are simultaneously transmitted to multiple devices by multicast, and in response to the reservation messages, the multiple devices simultaneously transmit confirmation messages on the channel, thereby multiplexing confirmation messages (see, for example, Patent Document 1). However, spatial multiplexing is established in this protection mechanism because the contents of the confirmation messages are identical. In other words, this protection mechanism cannot be applied to frames whose contents may differ for each terminal, such as confirmations of receipt of multicast data. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2013-528015 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the technology disclosed in this specification is to provide an excellent wireless communication device that can improve reliability by utilizing receipt confirmation responses while ensuring efficient use of wireless resources in multicast transmission in wireless transmission. [Means for solving the problem]

[0008] The present application has been made in consideration of the above problems, and the technology described in claim 1 is as follows: a communication unit that wirelessly communicates with a plurality of slave stations under its control; a control unit that controls data transmission with each slave station via the communication unit; Equipped with the control unit causes the communication unit to perform multicast transmission as a parent station to a plurality of child stations and to request the child stations to acknowledge receipt of the multicast transmission; The communication unit performs a receiving process for receiving acknowledgement responses simultaneously transmitted from a plurality of slave stations. It is a wireless communication device.

[0009] According to the technology described in claim 2 of the present application, the control unit of the wireless communication device described in claim 1 is configured to selectively request confirmation of receipt from among the child stations participating in the multicast group to which the multicast has been transmitted.

[0010] According to the technology described in claim 3 of the present application, the control unit of the wireless communication device described in claim 1 specifies, via the communication unit, a sub-station which transmits an acknowledgment response frame and one of the transmission methods of the acknowledgment response frame, and the communication unit is configured to separate multiple acknowledgment response frames simultaneously received from multiple sub-stations based on propagation path information between the multiple sub-stations and the own station.

[0011] According to the technology described in claim 4 of the present application, the designation of the transmission method includes an encoding method of a training signal of an acknowledgment response frame for making a format that allows multiple slave stations to separate each of the signals by calculation even if the multiple slave stations transmit simultaneously. The communication unit of the wireless communication device described in claim 3 is configured to acquire propagation path information between each slave station from the training signal transmitted from each slave station in accordance with the encoding method.

[0012] According to a technique recited in claim 5 of the present application, in the wireless communication device recited in claim 3, the designation of the transmission method includes information on a combination of a modulation scheme and an error correction coding scheme for an acknowledgment frame.

[0013] According to a technique recited in claim 6 of the present application, in the wireless communication device recited in claim 3, the designation of the transmission method includes information on the transmission power of a receipt confirmation response frame.

[0014] According to the technology described in claim 7 of the present application, the control unit of the wireless communication device described in claim 3 is configured to notify the designation of the transmission method in a management frame or beacon frame including subgroup identification information notifying that the subgroup is a member of the subgroup when the substation requesting receipt confirmation is subgrouped.

[0015] According to the technology described in claim 8 of the present application, the control unit of the wireless communication device described in claim 3 is configured to notify the designation of the transmission method in a frame requesting receipt confirmation.

[0016] In addition, the technology described in claim 9 of the present application is as follows: A communication unit for wirelessly communicating with the master station; a control unit that controls data transmission with a parent station via the communication unit; Equipped with The communication unit receives a frame that is multicast to a multicast group including the own station, the control unit, when a predetermined condition is satisfied, causes the communication unit to transmit a receipt confirmation response after a predetermined time has elapsed since receiving the multicast transmitted frame. It is a wireless communication device.

[0017] According to the technology described in claim 10 of the present application, the communication unit of the wireless communication device described in claim 9 is configured to transmit a receipt confirmation response frame using a method for transmitting a receipt confirmation response frame specified by the parent station.

[0018] According to the technology described in claim 11 of the present application, the designation of the transmission method includes an encoding method of the training signal of the receipt confirmation response frame in a format that allows multiple slave stations to separate the signals by calculation even when the multiple slave stations transmit simultaneously. The communication unit of the wireless communication device described in claim 10 is configured to encode the training signal in accordance with the encoding method and transmit the encoded training signal.

[0019] According to the technology described in claim 12 of the present application, the designation of the transmission method includes information on a combination of a modulation method and an error correction coding method for the receipt acknowledgment response frame. The communication unit of the wireless communication device described in claim 10 is configured to determine the combination of the modulation method and the error correction coding method to be used for the receipt acknowledgment response frame according to the designation of the transmission method.

[0020] According to the technology described in claim 13 of the present application, the designation of the transmission method includes information on the transmission power of the receipt acknowledgment response frame. And, the communication unit of the wireless communication device described in claim 10 is configured to determine the transmission power to be used for the receipt acknowledgment response frame according to the designation of the transmission method.

[0021] According to the technology described in claim 14 of the present application, the control unit of the wireless communication device described in claim 9 is configured to cause the communication unit to transmit an acknowledgment response frame when its own individual identifier or connection identifier is specified in a multicast data frame or a frame requesting acknowledgment received from a parent station.

[0022] According to the technology described in claim 15 of the present application, the control unit of the wireless communication device described in claim 9 is configured to cause the communication unit to transmit an acknowledgment response frame when subgroup identification information that includes the own station is specified in a multicast data frame received from a parent station or a frame requesting acknowledgment of receipt, the subgroup identification information having been notified in advance by the parent station.

[0023] According to the technology described in claim 16 of the present application, the control unit of the wireless communication device described in claim 9 is configured to determine whether or not to cause the communication unit to transmit a receipt acknowledgment response frame based on the relationship between the sequence number of the received multicast data frame and subgroup identification information that has been notified in advance by the parent station.

[0024] According to the technology described in claim 17 of the present application, the communication unit of the wireless communication device described in claim 9 is configured to set the transmission power based on an estimated result of the attenuation of the propagation path between the local station and the parent station so that the received power at the parent station becomes a predetermined power, and to transmit a receipt confirmation response.

[0025] According to the technology recited in claim 18 of the present application, the wireless communication device recited in claim 1 is configured to operate as an access point of the IEEE 802.11 standard or a GO (Group Owner) of the Wi-Fi Direct standard.

[0026] According to the technology described in claim 19 of the present application, the wireless communication device described in claim 9 is configured to operate as a station according to the IEEE 802.11 standard or as a client according to the Wi-Fi Direct standard. Effect of the Invention

[0027] According to the technology disclosed in this specification, it is possible to provide an excellent wireless communication device that can improve reliability by utilizing receipt confirmation responses while ensuring efficient use of wireless resources in multicast transmission in wireless transmission.

[0028] According to the technology disclosed in this specification, multiple wireless communication devices that are destinations of a multicast data frame simultaneously transmit multicast acknowledgments using spatial multiplexing, and the source wireless communication device disassembles the simultaneously received acknowledgments and restores the original individual acknowledgments through signal processing based on channel information with each destination wireless communication device. In other words, according to the technology disclosed in this specification, it is possible to improve communication quality by allowing simultaneous transmission of multicast data frames and enabling effective use of communication resources while enabling retransmission control using acknowledgments.

[0029] It should be noted that the effects described in this specification are merely examples, and the effects of the present invention are not limited thereto. Furthermore, the present invention may have additional effects in addition to the effects described above.

[0030] Further objects, features and advantages of the technology disclosed in this specification will become apparent from the following detailed description based on the embodiments and the accompanying drawings. [Brief description of the drawings]

[0031] [Figure 1A] FIG. 1A is a diagram illustrating a schematic configuration example of a data transmission system 100 to which the technology disclosed in this specification is applied. [Figure 1B] FIG. 1B is a diagram illustrating a schematic configuration example of a data transmission system 100 to which the technology disclosed in this specification is applied. [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of the functional configuration of the multicast distribution server 130. As shown in FIG. [Diagram 3] FIG. 3 is a diagram showing an example of the internal configuration of the wireless master station 120. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of the internal configuration of the wireless slave station 110. As shown in FIG. [Diagram 5] FIG. 5 is a diagram showing a process flow in the first embodiment. [Figure 6] FIG. 6 illustrates the inclusion relationships of stations connected to the same access point, members of a multicast group, acknowledgement targets, and subgroups. [Figure 7] FIG. 7 shows the frame format used in normal packet transmission in an IEEE802.11 wireless LAN system. [Figure 8A] FIG. 8A is a diagram showing the contents of a PHY preamble when a code is assigned using orthogonal coding and coding of a long preamble is performed. [Figure 8B]FIG. 8B is a diagram showing the contents of a PHY preamble when a code is assigned using time division transmission and encoding of a long preamble is performed. [Figure 9] FIG. 9 is a diagram showing an example of a communication sequence for transmitting and receiving multicast data frames between the AP and the STAs #1 to #6 and confirming their receipt in the first embodiment. [Figure 10] FIG. 10 is a flowchart illustrating a process performed by the STA in response to receiving the MU-BAR frame from the AP in the first embodiment. [Figure 11] FIG. 11 is a flowchart showing the procedure for receiving and processing an MU-BA from a subgroup member designated by an AP. [Figure 12] FIG. 12 is a diagram showing a process flow in the second embodiment. [Figure 13] FIG. 13 is a flowchart illustrating a process performed by the STA in response to receiving an MU-BAR frame from the AP in the second embodiment. [Figure 14] FIG. 14 is a diagram showing a process flow in the third embodiment. [Figure 15] FIG. 15 is a diagram showing an example of a communication sequence for transmitting and receiving multicast data frames between the AP and the STAs #1 to #6 and confirming their receipt in the third embodiment. [Figure 16] FIG. 16 is a diagram showing a process flow in the fourth embodiment. [Figure 17] FIG. 17 is a flowchart illustrating a process performed by a STA in response to receiving a multicast data frame from an AP in the fourth embodiment. [Figure 18] FIG. 18 is a diagram showing a process flow in the fifth embodiment. [Figure 19] FIG. 19 is a diagram showing an example of a communication sequence for transmitting and receiving multicast data frames between the AP and the STAs #1 to #6 and confirming their receipt in the fifth embodiment. [Figure 20]FIG. 20 is a flowchart illustrating a process performed by the STA in response to receiving an MU-BAR frame from the AP in the fifth embodiment. [Figure 21] FIG. 21 is a flowchart showing the procedure for receiving and processing an MU-BA from a STA designated by an AP. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, embodiments of the technology disclosed in this specification will be described in detail with reference to the drawings.

[0033] FIG. 1 shows a schematic configuration example of a data transmission system 100 to which the technology disclosed in this specification is applied.

[0034] In the illustrated data transmission system 100, as shown in Fig. 1B, a multicast distribution server 130 and a wireless master station 120 are connected via a backbone network 140. Also, as shown in Fig. 1A, the wireless master station 120 has a plurality of wireless slave stations 110-1, 110-2, ... under its control, and communicates wirelessly with each of the wireless slave stations 110-1, 110-2, .... In this data transmission system 100, multicast data transmitted by the multicast distribution server 130 is delivered (multicast transmitted) to the wireless slave stations 110-1, 110-2, ... all at once via the wireless master station 120.

[0035] 1A illustrates six wireless slave stations 110-1, 110-2, ..., 110-6, each of which has established a connection with the wireless master station 120. For the sake of convenience, in the following description, it is assumed that all of the six wireless slave stations 110-1, 110-2, ..., 110-6 are participating in a multicast group that receives multicast data from the multicast distribution server 130.

[0036] However, the technology disclosed in this specification does not require all wireless slave stations 110 connected to the wireless master station 120 to participate in the multicast group, and other wireless slave stations (not shown) that do not participate in the multicast group may be connected to the wireless master station 120. Furthermore, the wireless slave stations 110-1, 110-2, ..., 110-6 connected to the wireless master station 120 can each perform individual communication with the wireless master station 120, separate from the multicast transmission.

[0037] In addition, the number of wireless master stations is not limited to one. One or more other wireless master stations each having other wireless slave stations (not shown) under its control may be connected to the multicast distribution server 130. Although only one wireless master station 120 is illustrated in FIG. 1B, it is also assumed that a plurality of wireless master stations are connected to the multicast distribution server 130 via the backbone network 140. Each wireless master station transmits the multicast data transmitted by the multicast distribution server 130 to its own subordinate wireless slave stations by multicast transmission.

[0038] Furthermore, as shown in FIG. 1B, the multicast distribution server 130 and the wireless master station 120 do not need to be separate entities, and the multicast distribution server 130 may be a single device that is physically integrated with any one of the wireless master stations.

[0039] 2 shows a schematic diagram of the functional configuration of the multicast distribution server 130. The illustrated multicast distribution server 130 includes a data source 201, a data processing unit 202, and a backbone communication unit 203. The data source 201 generates content to be distributed, encodes it, and passes it to the data processing unit 202. The data processing unit 202 generates packets from the data input from the data source 201. The backbone communication unit 203 adds a protocol header for communication on the backbone network 140 to the packets, and sends them to the backbone network 140.

[0040] 3 shows an example of the internal configuration of the wireless master station 120. The wireless master station 120 shown in the figure includes a backbone communication unit 301, a data processing unit 302, a modulation / demodulation unit 303, a spatial signal processing unit 304, a channel estimation unit 305, a wireless interface unit 306, an antenna 307, and a control unit 308. In the example shown in the figure, the wireless master station 120 includes a plurality of transmitting / receiving antennas 307-1, ..., 307-M and wireless interface (IF) units 306-1, ..., 306-M for each antenna, and performs multi-user MIMO (Multiple Input Multiple Output) communication.

[0041] The backbone communication unit 301 communicates with the backbone network 140. Data sent from the multicast distribution server 130 arrives at the backbone communication unit 301.

[0042] When the data processing unit 302 receives an input from the backbone communication unit 301 or when it has data that it has generated, it processes the data into packets for wireless transmission, such as by adding a header for media access control (MAC) and an error detection code, and provides the processed data to the modem unit 303. Conversely, when it receives an input from the modem unit 303, the data processing unit 302 analyzes the header, detects packet errors, and reorders the packets, and passes them to its own protocol upper layer or the backbone communication unit 301.

[0043] During wireless transmission, the modem unit 303 performs error correction coding, interleaving, and modulation processing on input data from the data processing unit 302 based on the error correction code and modulation method set by the control unit 308, generates a data symbol stream, and passes it to the spatial signal processing unit 304. During wireless reception, the modem unit 303 performs demodulation, deinterleaving, and error correction decoding processing on the input from the spatial signal processing unit 304, which is the opposite of the transmission processing, and passes it to the data processing unit 302 or the control unit 308.

[0044] During wireless transmission, the spatial signal processing unit 304 performs signal processing (described later) for spatial separation on the input as necessary, and provides the obtained one or more transmission symbol streams to each of the wireless interface units 306-1, ..., 306-M. During wireless reception, the spatial signal processing unit 304 performs spatial processing on the reception symbol streams input from each of the wireless interface units 306-1, ..., 306-M, and decomposes the streams as necessary before passing them to the modem unit 303.

[0045] The channel estimation unit 305 calculates complex channel gain information of the propagation path from the preamble portion and the training signal portion of the input signal from each of the wireless interface units 306-1, ..., 306-M. The calculated complex channel gain information is used for demodulation in the modem unit 303 and spatial processing in the spatial signal processing unit 304 via the control unit 308.

[0046] During wireless transmission, each of the wireless interface units 306-1, ..., 306-M converts the digital transmission signal input from the spatial signal processing unit 304 into an analog transmission signal, power amplifies it, filters it, and further frequency up-converts it to a wireless frequency band, and sends it to the corresponding antenna 307-1, ..., 307-M. During wireless reception, each of the wireless interface units 306-1, ..., 306-M performs the inverse process on the input from the corresponding antenna 307-1, ..., 307-M, i.e., frequency down-conversion, filtering, low noise amplification, and conversion to a digital signal, and provides the result to the spatial signal processing unit 304 or the channel estimation unit 305.

[0047] The control unit 308 transfers information between the units 301 to 306, sets communication parameters, and schedules packets in the data processing unit 302.

[0048] 4 shows an example of the internal configuration of the wireless slave station 110. The illustrated wireless slave station 110 includes a data sink 401, a data processing unit 402, a modulation / demodulation unit 403, a spatial signal processing unit 404, a channel estimation unit 405, a wireless interface unit 406, an antenna 407, and a control unit 408. In the illustrated example, the wireless slave station 110 includes M transmitting / receiving antennas 407-1, ..., 407-M' and wireless interface units 406-1, ..., 406-M' for each antenna, but the wireless slave station 110 does not need to include multiple transmitting / receiving systems and may include only one.

[0049] The data sink 401 is a destination of the received data, and the data in the data source 201 in the multicast distribution server 130 arrives at the data sink 401 via the backbone network 140 and the wireless master station 120 .

[0050] When the data processing unit 402 is transmitting data that it has generated, it processes the data into packets for wireless transmission, such as by adding a header for media access control (MAC) and an error detection code, and provides the processed data to the modem unit 403. Conversely, when it is receiving input from the modem unit 403, the data processing unit 402 analyzes the header, detects packet errors, and reorders the packets, and passes them to its own protocol upper layer or the data sink 401.

[0051] During wireless transmission, the modem unit 403 performs error correction coding, interleaving, and modulation processing on input data from the data processing unit 402 based on the error correction code and modulation method set by the control unit 408, generates a data symbol stream, and passes it to the spatial signal processing unit 404. During wireless reception, the modem unit 403 performs demodulation, deinterleaving, and error correction decoding processing on the input from the spatial signal processing unit 404, which is the opposite of the transmission processing, and passes it to the data processing unit 402 or the control unit 408.

[0052] The spatial signal processing unit 404 provides the signal to the wireless interface units 406-1, ..., 406-M'. During wireless reception, the spatial signal processing unit 404 performs spatial processing on the received symbol streams input from the wireless interface units 406-1, ..., 406-M', decomposes the streams as necessary, and passes the decomposed streams to the modem unit 403.

[0053] The channel estimation unit 405 calculates complex channel gain information of the propagation path from the preamble portion and the training signal portion of the input signal from each of the wireless interface units 406-1, ..., 406-M'. The calculated complex channel gain information is used for demodulation in the modem unit 403 and spatial processing in the spatial signal processing unit 404 via the control unit 408.

[0054] During wireless transmission, each of the wireless interface units 406-1, ..., 406-M' converts the digital transmission signal input from the spatial signal processing unit 404 to an analog transmission signal, power amplifies it, filters it, and further frequency up-converts it to a wireless frequency band, and sends it to the corresponding antenna 407-1, ..., 407-M'. During wireless reception, each of the wireless interface units 406-1, ..., 406-M' performs the inverse processing on the input from the corresponding antenna 407-1, ..., 407-M', i.e., frequency down-conversion, filtering, low noise amplification, and conversion to a digital signal, and provides the result to the spatial signal processing unit 404 or the channel estimation unit 405.

[0055] The control unit 408 transfers information between the units 401 to 406, sets communication parameters, and schedules packets in the data processing unit 402.

[0056] A data transmission system 100 to which the technology disclosed in this specification is applied utilizes spatial multiplexing to allow simultaneous transmission of multicast acknowledgements, thereby enabling efficient use of communication resources while enabling retransmission control using acknowledgements to improve communication quality.

[0057] When the multiple wireless slave stations 110-1... included in the multicast group receive the multicast data frame, they simultaneously transmit multicast acknowledgement responses using spatial multiplexing in response to an acknowledgement request from the source wireless master station 120. Meanwhile, the wireless master station 120 separates and restores the simultaneously received acknowledgement responses into the original individual acknowledgement responses by signal processing based on channel information with each wireless slave station 110-1....

[0058] The mechanism for simultaneous acknowledgement of receipt in multicast transmission will be explained in detail with reference to the following five examples.

[0059] Example 1: With pre-subgrouping. The receipt confirmation request is a separate frame from the data frame. Example 2: No prior subgrouping. The acknowledgement request is a separate frame from the data frame. Example 3: No prior subgrouping. The receipt confirmation request is included in the data frame and is explicitly specified. Example 4: With pre-subgrouping. The receipt confirmation request is implicitly requested using the existing parameter values, which are also included in the data frame. Example 5: Acquire channel gain information from all users in advance. Acknowledgement requests are sent in separate frames from data frames.

[0060] In the following, it is assumed that an IEEE802.11 wireless LAN (Local Area Network) system is applied to wireless communication between the wireless master station 120 and the wireless slave station 110. Each embodiment will be described by replacing the wireless master station 120 with an access point (AP) and the wireless slave station 110 with a station (STA). EXAMPLES

[0061] In the first embodiment, the AP divides the STAs that will join the multicast group into subgroups in advance, and transmits a receipt confirmation request to the group member STAs in a frame separate from the data frame.

[0062] FIG. 5 shows a process flow in the first embodiment.

[0063] Understanding Multicast Groups First, in flow F501, each STA belonging to a multicast group is assumed to have joined the multicast group it wishes to receive in advance. To join a multicast group, mechanisms such as IGMP (Internet Group Management Protocol) or IPv6 MLD (Multicast Listener Discovery) are used. Each STA receives the multicast address of the multicast group in which it is participating.

[0064] Multicast group joining protocols such as IGMP and IPv6 MLD are layer 3 or higher, so normally, when joining a multicast group, the AP does not know which multicast addresses the STAs under its control are receiving. For this reason, each STA that joins a multicast group notifies the AP of its multicast registration status separately, either at the request of the AP or voluntarily, so that the AP can know the multicast group joining status. Alternatively, the AP may have a mechanism for analyzing the contents of layer 3 or higher and collect information on the multicast participation of its subordinate STAs by itself.

[0065] 《Creating a Receipt Confirmation Subgroup》 Next, in flow F502, the AP classifies the participating STAs into one or more subgroups for acknowledgment for each multicast group. As will be described later, the AP does not request acknowledgment for the multicast transmission from all STAs in the multicast group every time it transmits a multicast, but only from the subgroup.

[0066] The AP, after grasping the multicast group participation status of each STA under its control by flow F501, first divides the STAs that are the recipients of a certain multicast group (hereafter referred to as group members) into those that are subject to receipt confirmation and those that are not. It is not necessary for all group members to be subject to receipt confirmation for the multicast flow. There are no restrictions on the criteria for this decision, but either (a1) or (a2) below may be used.

[0067] (a1) Communication quality obtained from past transmission and reception for each STA (for example, downlink error rate and modulation information used, uplink received signal strength, etc.). For example, only group members with poor communication quality (communication quality below a specified value, or a specified number of group members with poor communication quality, etc.) are subject to the multicast reception confirmation. (a2) Information notified by each STA as to whether reliability is required for the corresponding multicast. For example, only group members that require reliability are subject to the corresponding multicast reception confirmation.

[0068] The AP then classifies the group members being acknowledged into one or more subgroups, which are the sets of STAs that will simultaneously acknowledge the multicast data frames that will subsequently be transmitted, all of which will of course be chosen from among the members of the multicast group.

[0069] The maximum number of members that can participate in each subgroup is determined in advance. In this embodiment, the maximum number of members in a subgroup is four. Generally, to separate multiple signals received simultaneously, more receiving antennas are required than the number of signals. For this reason, in this embodiment, the wireless master station 120 serving as an AP is equipped with four or more sets of wireless interface units 306 and antennas 307.

[0070] The criteria for classifying STAs into subgroups are not limited. For example, either of the following criteria (b1) or (b2) may be used.

[0071] (b1) A combination that makes it easier to separate signals based on wireless channel state information (Channel State Information: CSI) between each member and the AP obtained from packets received so far from each member. (b2) A combination that reduces the difference in reception level at the AP based on the CSI information obtained from packets received so far from each member.

[0072] For reference, Fig. 6 shows an example of the containment relationship between STA 600 connected to the same AP, members of a multicast group 610, targets of multicast transmission acknowledgement 611, and subgroups. Note that a STA can belong to multiple multicast groups, so if there are multiple multicast groups, they may overlap with each other.

[0073] In the example shown in Fig. 6, STAs (subordinate stations) 600 connected to the same AP are divided into two groups: members of a multicast group 610 and STAs 620 that do not belong to the multicast group. The STAs that are members of the multicast group 610 are divided into multicast reception confirmation targets 611 and group members 612 that do not perform reception confirmation, based on the state of grasping the multicast group participation status. The multiple STAs that are multicast reception confirmation targets 611 are then classified into subgroups #0, #1, ... of a predetermined number of units or less, based on criteria such as wireless channel state information and reception level.

[0074] In the data transmission system 100 (see FIG. 1A) referred to in this embodiment, there are six stations (wireless slave stations), all of which belong to the same multicast group.

[0075] In the following explanation, it is assumed that all six STAs #1 to #6 are the targets of receipt confirmation, and that the six STAs are classified into two subgroups #0 and #1 of three STAs each, as follows. Note that identification information for identifying a subgroup is referred to as a subgroup identifier.

[0076] Subgroup #0: STA#1, STA#3, STA#5 Subgroup #1: STA#2, STA#4, STA#6

[0077] <<Generating Subgroup Attachment Information>> Once the members to be acknowledged are classified into subgroups, the AP further generates auxiliary information for signal separation within the subgroups.

[0078] The purpose of generating the auxiliary information is that in order to recover individual acknowledgements from the acknowledgement response frames that are transmitted simultaneously from the STAs in the subgroup, CSI information from all STAs in the subgroup is required, and this information can be obtained from the acknowledgement frame itself.

[0079] The acquisition of CSI information will now be described. Fig. 7 shows a frame format used for normal packet transmission in an IEEE802.11 wireless LAN system. A packet 700 is made up of a PHY Preamble section 710, a PHY Header section 720, a MAC Header section 730, and a Payload section 740.

[0080] The PHY Preamble section 710 stores a fixed data sequence (hereinafter referred to as a Short Preamble) 711 for performing packet detection and frequency synchronization in the physical layer on the receiving side, and a fixed data sequence (hereinafter referred to as a Long Preamble) 712 for obtaining CSI on the receiving side. This latter data sequence is referred to as L. Since L is known, the wireless device that receives the packet can know the CSI by using the received waveform of that part. Known information for obtaining CSI, such as this Long Preamble, is also called a training signal.

[0081] However, if the STAs that are subgroup members simultaneously transmit receipt confirmations in this format, the signal in the Long Preamble section 712 for CSI estimation will be interfered with, and the AP will not be able to obtain individual CSI information. To address this issue, we consider encoding the signal in the Long Preamble section 712 differently for each member in the subgroup.

[0082] In this embodiment, the Long Preamble portion is expanded and encoded into a format that can be received even if the frames are simultaneously transmitted, and is used in the receipt confirmation response frame. As the encoding method, for example, either of the following methods (c1) or (c2) can be used.

[0083] (c1) Orthogonal coding In the orthogonal coding method, first, a Walsh sequence having a length equal to or greater than the maximum number of members in a subgroup is generated. In this embodiment, the maximum number is set to 4, so a Walsh sequence with a sequence length of 4 is generated. In this case, four sequences, Codes 1 to 4, shown below, can be used.

[0084] [ 1, 1, 1, 1] (sign 1) [ 1, 1,-1,-1] (sign 2) [ 1,-1, 1,-1] (sign 3) [ 1,-1,-1, 1] (sign 4)

[0085] Using Walsh sequences, we can generate four sequences with length four times L by multiplying each element by sequence L, as shown below.

[0086] [L, L, L, L] [L, L,-L,-L] [ L,-L, L,-L] [ L,-L,-L, L]

[0087] The above four sequences are orthogonal to each other. Therefore, even if they are received simultaneously, each CSI can be obtained by multiplying them by the code corresponding to the code to be extracted from the above codes 1 to 4 and adding them for each length of L.

[0088] In this method, one of the above codes 1 to 4 is assigned to the group member STAs for each subgroup without duplication.

[0089] (c2) Time-division transmission In the time division transmission method, the transmission times from each subgroup member are shifted so that the transmissions of L do not overlap. This is equivalent to replacing the codes in the above orthogonal coding with the following codes 11 to 13.

[0090] [ 1, 0, 0] (sign 11) [ 0, 1, 0] (sign 12) [ 0, 0, 1] (sign 13)

[0091] In the data transmission system 100 (see FIG. 1) referred to in this embodiment, six group members STA#1 to #6 are classified into two subgroups #0 and #1 of three each (as described above), and in each subgroup, codes are assigned using either orthogonal coding or time division transmission, as shown in (d1) and (d2) below.

[0092] (d1) Subgroup #0 STA#1 ... Code 1 or Code 11 STA#3: Code 2 or Code 12 STA#5 … Code 3 or Code 13 (d2) Subgroup #1 STA#2 … Code 1 or Code 11 STA#4 … Code 2 or Code 12 STA#6 … Code 3 or Code 13

[0093] Fig. 8A shows the contents of the PHY preamble when codes 1 to 3 are assigned to group member STAs in each of subgroups #0 and #1 without overlapping, and codes are assigned using orthogonal coding to encode the long preamble. Fig. 8B shows the contents of the PHY preamble when codes 11 to 13 are assigned to group member STAs in each of subgroups #0 and #1 without overlapping, and codes are assigned using time division transmission to encode the long preamble.

[0094] <<Advance notification of receipt confirmation subgroup and ancillary information>> Then, in flow F503, the AP notifies each group member in advance of the subgroup information of each member determined above and the coding information of the Long Preamble signal used by each member in the subgroup. The management frame transmitted by the AP for this notification is referred to as the Ack Group Assignment frame below. The AP may transmit the Ack Group Assignment frame individually to each member by unicast, or may transmit it to a multicast address that can be received by all group members. The AP may also transmit the attached information as part of an existing broadcast frame such as a beacon, without using a dedicated Ack Group Assignment frame.

[0095] The information that the AP will notify each member in advance will include the following (e1) and (e2).

[0096] (e1) Information that associates each group member with the subgroup identifier to which it belongs (e2) Attachment information for each subgroup member (long preamble coding method, maximum code length, and assigned code identifier)

[0097] Of the above (e2) auxiliary information, the maximum code length (which, as mentioned above, is linked to the maximum number of members in the subgroup) and the Long Preamble coding method do not necessarily need to be included in the Ack Group Assignment frame if they are determined and shared in advance.

[0098] In addition, information regarding the modulation scheme and error correction coding used by the subgroup members for the acknowledgment response, as well as the transmission power used for the acknowledgment response, may be included in the ancillary information of the Ack Group Assignment frame (instead of the MU-BAR described below).

[0099] A group member that has received the subgroup information and the additional information (e1) and (e2) in advance stores it, for example, in a memory in the control unit 408, and uses it when transmitting a receipt confirmation response frame (training signal).

[0100] The AP may add or change the subgroup assignment and associated information during the delivery of a multicast flow, in which case it will re-run the notification process described above for all members.

[0101] The above steps F501 to F503 are steps related to the preliminary setup, and need only be executed at least once.

[0102] The subsequent processes F504 to F508 are processes that are repeatedly performed in association with the transmission and reception of multicast data. Fig. 9 shows an example of a communication sequence for transmitting and receiving multicast data frames between the AP and STAs #1 to #6 and confirming their receipt in this embodiment.

[0103] Multicast data transmission and reception In flow F504, the AP sequentially transmits multicast data DATA#0, DATA#1, and DATA#2 to STA#1 to STA#6 in the multicast group as shown by reference numbers 901 to 903 in Fig. 9. These multicast data frames are transmitted using the normal frame format as shown in Fig. 7 without undergoing the encoding process described above.

[0104] If multicast group member STAs #1 to #6 have previously been acknowledged in the Ack Group Assignment frame or beacon frame and have been assigned to a subgroup, they retain the reception status of each multicast frame for each sequence number of the multicast data frame.

[0105] At the same time, STAs #1 to #6, which are group members of the subgroup, use the PHY preamble of the multicast data frame to correct the frequency offset of their reference oscillators for the AP.

[0106] 《Confirmation of receipt》 In this embodiment, after transmitting one or more multicast data frames, the AP transmits an acknowledgment request frame (hereinafter referred to as a Multi-User Block Ack Request (MU-BAR) frame) for multiple users as shown by reference numbers 904 and 908 in FIG. 9 as flow F505.

[0107] In this embodiment (the example shown in FIG. 9), it is assumed that the AP transmits the MU-BAR alone as one wireless packet. As a modification, the AP may transmit the MU-BAR as one wireless packet in the wireless section by aggregating the multicast data and the MU-BAR at the MAC layer using A-MPDU (Aggregated Mac Protocol Data Unit).

[0108] The MU-BAR frame includes the following contents (f1) to (f5).

[0109] (f1) Information for identifying the multicast flow for which receipt is to be acknowledged (f2) Subgroup identifier for which a multicast acknowledgment is expected (f3) The starting sequence number for which the subgroup members are to receive multicast acknowledgments. (f4) The modulation method and error correction code used in the acknowledgement response (f5) Information regarding the transmission power used for the receipt confirmation response

[0110] Here, the information (f4) on the modulation method used for the acknowledgement response does not necessarily have to be explicitly specified, and as long as the AP and each STA share a rule that is uniquely determined for all acknowledgement targets, such as always using the lowest rate or using the same rate as the MU-BAR frame, the information on the modulation method does not have to be included in the frame. The modulation method used for the acknowledgement response may be limited to modulation that does not use two or more spatial streams.

[0111] The purpose of transmitting the information (f5) about the transmission power used in the acknowledgement response is to prevent a large difference in the reception power between the acknowledgement responses that the AP receives simultaneously from multiple STAs. If there is a too large difference in reception power, it may not be possible to restore the response frame with the lower power. For this reason, the AP notifies each member STA of the desired transmission power so that the reception power of the response from each subgroup member STA matches the target power. The content of the information (f5) is to directly specify the value of the transmission power to be used in the response transmission, or to specify the difference value from the previous transmission power to convey that the previous response transmission should be increased or decreased to approach the desired power. The calculation of this difference value may refer to the reception power during past frame transmission and reception with the subgroup member. Note that the information (f5) about the transmission power request does not necessarily have to be included in the frame. In that case, each STA will autonomously determine and adjust the transmission power.

[0112] The MU-BAR frame is sent to the multicast address that is the subject of acknowledgment. The destination address may be used implicitly as the identifier (f1) of the multicast flow that is the subject of acknowledgment.

[0113] When the STAs of subgroup members #0 and #1 receive MU-BAR frames 904 and 908 from the AP, they transmit acknowledgement response MU-BA frames for the corresponding multicast flows as flow F506, as shown by reference numbers 905 to 907 and 909 to 911 in Fig. 9. At this time, they encode the Long Preamble (as described above) using encoding information specified in advance by the AP and transmit it.

[0114] FIG. 10 shows, in the form of a flowchart, a processing procedure that a STA executes in response to receiving an MU-BAR frame from an AP.

[0115] When the STA receives an MU-BAR frame from the AP (Yes in step S1001), the STA checks whether the subgroup identifier included in the MU-BAR frame is that of the group to which the STA belongs (step S1002).

[0116] If the subgroup identifier is not that of the group to which the STA belongs (No in step S1002), the STA skips all subsequent processes and ends this process.

[0117] On the other hand, if the subgroup identifier is that of the group to which the STA belongs (Yes in step S1002), the STA generates a receipt confirmation response MU-BA from the reception success / failure record of the multicast flow targeted by the MU-BAR frame (step S1003).

[0118] Each subgroup member STA includes in the MU-BA frame it generates information on reception success / failure for each sequence number in the target multicast flow. However, although the target is the multicast flow sent by the AP before receiving the MU-BAR frame, it is not necessary to include information prior to the starting sequence number notified in the MU-BAR frame. Also, if a frame arrives requesting retransmission within the STA, but the STA determines that the upper layer of the STA has no further use, the STA may notify the frame as successful even if it was not received.

[0119] Next, the STA checks whether or not it has received information on the transmission power to be used in the receipt confirmation response frame in the MU-BAR frame (step S1004).

[0120] If the STA has received information about the transmission power to be used for the receipt confirmation response frame in the MU-BAR frame (Yes in step S1004), the STA sets the transmission power to be used for the receipt confirmation response frame as instructed in the MU-BAR frame (step S1005).

[0121] Also, if the STA has not received information on the transmission power to be used in the receipt acknowledgement frame in the MU-BAR frame (No in step S1004), the STA estimates the propagation loss from past reception power information (of packets received from the previous AP, including MU-BAR), and sets the transmission power of the receipt acknowledgement frame so that the reception power on the AP side becomes a predetermined value (step S1007). Note that this predetermined value is assumed to be shared in advance at least among the STAs that are subgroup members.

[0122] Note that the power used for transmitting MU-BA in steps S1005 and S1007 may be controlled as required.

[0123] The STA then adds a PHY Preamble that is a Long Preamble encoded using encoding information notified in advance in the Ack Group Assignment frame or beacon frame, and transmits an acknowledgment response (Multi-User Block Ack: MU-BA) frame (step S1006).

[0124] In summary, according to the processing flow shown in FIG. 10, a STA that receives an MU-BAR checks whether the subgroup identifier described in the contents matches that of the subgroup to which it belongs, and transmits an MU-BA frame only if they match.

[0125] The timing of transmission of MU-BA from STA is a predetermined time after the STA finishes receiving MU-BAR. This predetermined time interval is shared between AP and all STAs, and is preferably an interval that cannot be interrupted by wireless transmission from a third party within the communication range. Also, information specifying this predetermined time interval may be included in MU-BAR, and a different value may be taken for each subgroup, or when transmitting another MU-BAR even in the same subgroup. In this embodiment, SIFS (Short Inter Frame Space) specified in the IEEE802.11 wireless LAN standard is used. Note that PIFS (PCF Inter Frame Space) may be used instead of SIFS. When transmitting, each STA does not need to perform carrier sense.

[0126] At the AP side, MU-BAs from the designated subgroup members are simultaneously received SIFS after the MU-BAR transmission. Then, in flow F507, the AP disassembles and restores the MU-BAs from the multiple STAs that were simultaneously received by the AP through signal processing.

[0127] The procedure for receiving and processing an MU-BA from a subgroup member designated by the AP is shown in the form of a flow chart in Figure 11. After transmitting an MU-BAR, the AP waits for an MU-BA frame from the subgroup and performs processing that differs from normal reception operations.

[0128] When the AP detects a short preamble (Yes in step S1101), the received signal processed by each wireless interface unit 306-1, ... is sent to the channel estimation unit 305, and the short preamble unit synchronizes the frame start timing, synchronizes the frequency, and sets the AGC (Auto Gain Control) (step S1102).

[0129] Next, the AP checks whether or not it has simultaneously received MU-BAs from group member STAs within the length of time (SIFS) in which responses are expected after the completion of MU-BAR transmission (step S1103).

[0130] Here, when MU-BAs are simultaneously received from group member STAs within the time length in which a response is expected after completion of MU-BAR transmission (Yes in step S1103), the channel estimation unit 305 restores the long preamble received sequence of each subgroup member from the respective codes pre-assigned to each group member STA in the coded long preamble section following the short preamble section, and obtains CSI estimates from each STA (step S1104).

[0131] When long preambles are encoded by assigning codes using orthogonal encoding, channel estimation section 305 restores the long preamble reception sequence of each subgroup member by multiplying a code corresponding to a code to be extracted from the orthogonal codes by one element of the code for each length unit of sequence L and adding the multiplication results for each length unit of L. When long preambles are encoded by assigning codes using time division transmission, channel estimation section 305 extracts the long preamble reception sequence of each subgroup member by shifting the time.

[0132] The Long Preamble reception sequence thus obtained is the CSI from each STA received by each antenna 307-1, ..., 307-M (reception chain). Here, the number of the reception antenna is m (m = 1 to M, where M is the total number of antennas that can be used for reception by the AP), and the number of the code used (together with the subgroup identifier, this is information that identifies the STA) is n (n = 1 to N, where N is the total number of codes used, the number of members of the subgroup, and corresponds to the MU-BA multiplexing number). From the combination of the reception antenna and the code used, an estimated channel matrix H with M × N elements can be obtained. The estimated CSI of each member STA is expressed as hm,n Then, the estimated channel matrix H is expressed by the following equation (1).

[0133]

number

[0134] The input signal received simultaneously at antenna number m is expressed as y m Then, the received signal vector Y is expressed by the following equation (2):

[0135]

number

[0136] The estimated channel matrix H and received signal vector Y are input to the spatial signal processing unit 304. Then, the spatial signal processing unit 304 restores (decomposes) the MU-BA from each subgroup member STA using the channel matrix H and received signal vector Y (step S1105). The decomposition process is applied to the signal after the Long Preamble section (i.e., after the PHY Header section).

[0137] The algorithm for the MU-BA restoration (decomposition) process performed by the spatial signal processor 304 is not particularly limited. For example, a plurality of signals can be decomposed using Minimum Mean Square Error (MMSE) equalization. According to MMSE equalization, the signal can be decomposed by multiplying the received signal vector Y by a weight vector W to suppress interference components from other STAs. The weight vector W is a noise vector n m Let N be the noise vector composed of the above. It is expressed by the following formula (3). In the following formula (3), I represents the unit matrix, H H represents the Hermitian transpose of the channel matrix

[0138]

number

[0139] By performing the above process, the AP can recover MU-BAs from all members of the subgroup targeted by the MU-BAR and obtain acknowledgement information for the multicast data flow.

[0140] On the other hand, if the MU-BA cannot be simultaneously received from the group member STAs within the expected time period from the completion of the transmission of the MU-BAR until a response is received (No in step S1103), the AP returns to normal reception operation. In this case, the channel estimation unit 305 acquires a CSI estimation value from one Long Preamble (step S1106). Then, the spatial signal processing unit 304 performs reception processing of the signal after the Long Preamble portion (i.e., after the PHY Header portion) based on the acquired CSI information (step S1107).

[0141] If the AP is unable to restore a frame that is superior to a particular code as a result of the MU-BA restoration process in step S1105, it is possible that the STA to which the code is assigned has not correctly received the MU-BAR and has not transmitted the MU-BA. Although the process in this case is not shown in FIG. 11, the AP may retransmit the MU-BAR.

[0142] Multicast data retransmission The AP separates the acknowledgement responses from the subgroup members to obtain the acknowledgement information, and depending on the result, retransmits the multicast data as flow F508 if necessary.

[0143] The AP may retransmit the multicast data immediately after receiving the acknowledgment response.

[0144] Also, if burst-like radio interference is detected, such as from a microwave oven, immediate retransmission may fail again. In such a case, the AP may retransmit the multicast data after adding a certain delay. If a delay requirement is specified for the multicast flow (content), the AP shall add a delay that does not exceed that requirement. EXAMPLES

[0145] In the second embodiment, the AP does not preliminarily divide the STAs that will join the multicast group into subgroups, and the AP transmits an acknowledgement request to the group member STAs in a frame separate from the data frame.

[0146] FIG. 12 shows a process flow in the second embodiment.

[0147] Understanding Multicast Groups First, in flow F1201, each STA belonging to a multicast group is assumed to have joined the multicast group it wishes to receive in advance. To join a multicast group, mechanisms such as IGMP and IPv6 MLD are used. Each STA receives the multicast address of the multicast group in which it is participating.

[0148] Each STA that participates in a multicast group notifies the AP of its multicast registration status separately, either at the request of the AP or voluntarily, so that the AP can know the multicast group participation status. Alternatively, the AP may have a mechanism for analyzing the contents of layer 3 and above and collect the multicast participation information of its subordinate STAs by itself.

[0149] In the second embodiment, the AP does not create a receipt confirmation subgroup, and does not notify the receipt confirmation subgroup and the attached information in advance.

[0150] The subsequent processing is repeated in association with the transmission and reception of multicast data. In this embodiment, as in the first embodiment, transmission and reception of multicast data frames are performed between the AP and the multicast groups STA#1 to #6 in accordance with the communication sequence shown in FIG.

[0151] Multicast data transmission and reception In flow F1202, the AP sequentially transmits multicast data DATA#0, DATA#1, and DATA#2 to STAs#1 to #6 in the multicast group as shown by reference numbers 901 to 903 in Fig. 9. These multicast data frames are transmitted using the normal frame format as shown in Fig. 7 without undergoing the encoding process described above.

[0152] Multicast group member STA#1~#6 stores the reception status of each multicast frame for each sequence number of the multicast data frame. In addition, multicast group member STA#1~#6 uses the PHY preamble of the multicast data frame to correct the frequency offset of the reference oscillator for the AP.

[0153] 《Confirmation of receipt》 In this embodiment, after transmitting one or more multicast data frames, the AP transmits an MU-BAR frame requesting an acknowledgement as flow F1203, as shown by reference numbers 904 and 908 in Fig. 9. In this embodiment, the AP writes in the MU-BAR frame the identifier of the STA requesting the MU-BA and the coding information of the long preamble, together with the above-mentioned contents (f1), (f4), and (f5).

[0154] Here, the identifier of the STA can be an individual identifier such as the MAC address of the STA or a connection identifier such as an Association ID (AID) in the AP. The additional information of the Long Preamble includes the Long Preamble coding method, the maximum code length, and the identifier of the assigned code.

[0155] In addition to transmitting the MU-BAR alone as a single wireless packet as shown in Figure 9, the AP may also transmit the MU-BAR as a single wireless packet in the wireless section by aggregating the MU-BAR and multicast data using A-MPDU at the MAC layer (same as above).

[0156] When each STA that is specified in the MU-BAR frame to request MU-BA by its individual identifier or connection identifier receives MU-BAR frames 904 and 908 from the AP, it transmits, as flow F1204, acknowledgement response MU-BA frames for the corresponding multicast flow, as shown by reference numbers 905 to 907 and 909 to 911 in Fig. 9. At this time, the Long Preamble portion is encoded (as described above) using the encoding information specified in the MU-BAR frame and transmitted.

[0157] FIG. 13 shows, in the form of a flowchart, a processing procedure that a STA executes in response to receiving an MU-BAR frame from an AP.

[0158] When the STA receives an MU-BAR frame from the AP (Yes in step S1301), the STA checks whether its own individual identifier or connection identifier is specified in the MU-BAR frame (step S1302).

[0159] If its own individual identifier or connection identifier is not specified (No in step S1302), the STA skips all subsequent processes and ends this process.

[0160] On the other hand, if its own individual identifier or connection identifier is specified (Yes in step S1302), the STA generates a receipt confirmation response MU-BA from the reception success / failure record of the multicast flow targeted by the MU-BAR frame (step S1303).

[0161] The STA includes in the MU-BA frame it generates information on reception success / failure for each sequence number in the target multicast flow. However, although the target is the multicast flow sent from the AP before receiving the MU-BAR frame, it is not necessary to include information prior to the start sequence number notified in the MU-BAR frame. Also, if a frame arrives within the STA requesting retransmission but is determined by the upper layer of the STA to be no longer useful, the STA may notify the frame as successful even if it was not received.

[0162] Next, the STA checks whether or not it has received information on the transmission power to be used in the receipt confirmation response frame in the MU-BAR frame (step S1304).

[0163] If the STA has received information about the transmission power to be used for the receipt confirmation response frame in the MU-BAR frame (Yes in step S1304), the STA sets the transmission power to be used for the receipt confirmation response frame as instructed in the MU-BAR frame (step S1305).

[0164] Also, if the STA has not received information on the transmission power to be used in the receipt acknowledgement frame in the MU-BAR frame (No in step S1304), the STA estimates the propagation loss from past reception power information (of packets received from the previous AP, including MU-BAR), and sets the transmission power of the receipt acknowledgement frame so that the reception power on the AP side becomes a predetermined value (step S1307). Note that this predetermined value is assumed to be shared in advance at least among the STAs that are subgroup members.

[0165] Note that the power used for transmitting MU-BA in steps S1305 and S1307 may be controlled as required.

[0166] Then, the STA adds a PHY preamble obtained by encoding a long preamble using the encoding information specified in the MU-BAR frame, and transmits the MU-BA frame (step S1306).

[0167] In summary, according to the processing flow shown in Figure 13, a STA that receives an MU-BAR checks whether the individual identifier or connection identifier described in the contents matches its own, and only sends an MU-BA frame if they match.

[0168] The timing of transmission of MU-BA from the STA is a predetermined time after the STA finishes receiving MU-BAR. This predetermined time interval is shared between the AP and all STAs, and is preferably an interval that cannot be interrupted by wireless transmission from a third party within the communication range. In this embodiment, SIFS or PIFS defined in the IEEE802.11 wireless LAN standard may be used. When transmitting, each STA does not need to perform carrier sense.

[0169] On the AP side, MU-BA from each of the designated STAs is received simultaneously after the SIFS time of the MU-BAR transmission. Then, the AP disassembles and restores the MU-BA from the multiple STAs received simultaneously by signal processing, for example, according to the processing procedure shown in FIG. 11 as flow F1205. Also, if the result of the MU-BA restoration process is that a frame superior to a specific code cannot be restored, it is possible that the STA to which the code is assigned has not received the MU-BAR correctly and has not transmitted the MU-BA. In that case, the AP may retransmit the MU-BAR.

[0170] Multicast data retransmission The AP separates the acknowledgement responses from each of the specified STAs to obtain acknowledgement information, and depending on the result, retransmits the multicast data as flow F1206 if necessary.

[0171] The AP may retransmit the multicast data immediately after receiving the acknowledgment response.

[0172] Also, if burst-like radio interference is detected, such as from a microwave oven, immediate retransmission may fail again. In such a case, the AP may retransmit the multicast data after adding a certain delay. If a delay requirement is specified for the multicast flow (content), the AP shall add a delay that does not exceed that requirement. EXAMPLES

[0173] In the third embodiment, the AP does not pre-group the STAs that will join the multicast group, and the AP explicitly designates the STAs to be acknowledged in the data frame that also serves as an acknowledgement request.

[0174] FIG. 14 shows a process flow in the third embodiment.

[0175] Understanding Multicast Groups First, in flow F1401, each STA belonging to a multicast group is assumed to have joined the multicast group it wishes to receive in advance. To join a multicast group, mechanisms such as IGMP and IPv6 MLD are used. Each STA receives the multicast address of the multicast group in which it is participating.

[0176] Each STA that participates in a multicast group notifies the AP of its multicast registration status separately, either at the request of the AP or voluntarily, so that the AP can know the multicast group participation status. Alternatively, the AP may have a mechanism for analyzing the contents of layer 3 and above and collect the multicast participation information of its subordinate STAs by itself.

[0177] In the third embodiment, similarly to the second embodiment, the AP does not create a receipt confirmation subgroup, and does not notify in advance of the receipt confirmation subgroup and the attached information.

[0178] The following processing is repeated as multicast data is transmitted and received. In this embodiment, multicast data frames are transmitted and received between the AP and the multicast groups STA#1 to #6, and their receipt is confirmed, according to the communication sequence shown in FIG.

[0179] Multicast data transmission and reception In flow F1402, the AP transmits multicast data DATA#0, DATA#1, and DATA#2 in sequence to STAs#1 to #6 in the multicast group as indicated by reference numbers 1501, 1505, and 1509 in FIG.

[0180] In this embodiment, these multicast data frames also serve as receipt confirmation requests. The AP extends the MAC header of each data frame DATA#0, DATA#1, and DATA#2, and writes the identifier of the STA requesting MU-BA and the coding information of the long preamble together with the above-mentioned contents (f1), (f4), and (f5). Unlike the first and second embodiments, the AP does not transmit an MU-BAR frame.

[0181] Here, the identifier of the STA can be an individual identifier such as the MAC address of the STA or a connection identifier such as an Association ID (AID) in the AP. The additional information of the Long Preamble includes the Long Preamble coding method, the maximum code length, and the identifier of the assigned code.

[0182] Each of the multicast group members STA#1-#6 retains the reception status of the multicast frame for which it is at least acknowledging, together with the sequence number of the multicast data frame. In addition, each of the multicast group members STA#1-#6 uses the PHY preamble of the multicast data frame to correct the frequency offset of the reference oscillator for the AP.

[0183] 《Receipt Acknowledgement Response》 The STA that receives the multicast data frames 1501, 1505, and 1509 checks whether the individual identifier or connection identifier written in the MAC header matches its own. Then, only if they match, the STA transmits an MU-BA frame as shown by reference numbers 1502 to 1504 and reference numbers 1506 to 1508 in FIG. 15. At this time, the STA encodes (as described above) the Long Preamble using the encoding information specified in the target multicast data frame and transmits it. The STA transmits an MU-BA frame to the AP in response to receiving the data frame that is the object of the acknowledgment, according to the processing procedure shown in FIG. 13. However, the "MU-BAR frame" in step S1301 in FIG. 13 should be read as "multicast data frame".

[0184] The timing for transmitting an MU-BA from a STA is a predetermined time after the STA has finished receiving the target multicast data frame. This predetermined time interval is shared between the AP and all STAs, and it is desirable that the interval is such that wireless transmissions from third parties within the communication range cannot interrupt the MU-BA. In this embodiment, SIFS or PIFS as specified in the IEEE802.11 wireless LAN standard may be used. When transmitting, each STA does not need to perform carrier sensing.

[0185] On the AP side, MU-BAs from the designated STAs are simultaneously received after the SIFS time of the MU-BAR transmission. Then, in flow F1404, the AP disassembles and restores the MU-BAs from the multiple STAs that were simultaneously received by signal processing, for example, according to the processing procedure shown in FIG.

[0186] Multicast data retransmission The AP separates the acknowledgement responses from each of the specified STAs to obtain acknowledgement information, and depending on the result, retransmits the multicast data as flow F1405 if necessary.

[0187] The AP may retransmit the multicast data immediately after receiving the acknowledgment response.

[0188] Also, if burst-like radio interference is detected, such as from a microwave oven, immediate retransmission may fail again. In such a case, the AP may retransmit the multicast data after adding a certain delay. If a delay requirement is specified for the multicast flow (content), the AP shall add a delay that does not exceed that requirement. EXAMPLES

[0189] In the fourth embodiment, the AP pre-classifies the STAs that will join the multicast group into subgroups, and the AP implicitly specifies the STAs to be acknowledged in the data frame that also serves as an acknowledgement request, using existing parameter values.

[0190] FIG. 16 shows a process flow in the fourth embodiment.

[0191] Understanding Multicast Groups First, in flow F1601, each STA belonging to a multicast group is assumed to have joined the multicast group it wishes to receive in advance. To join a multicast group, mechanisms such as IGMP and IPv6 MLD are used. Each STA receives the multicast address of the multicast group in which it is participating.

[0192] Each STA that participates in a multicast group notifies the AP of its multicast registration status separately, either at the request of the AP or voluntarily, so that the AP can know the multicast group participation status. Alternatively, the AP may have a mechanism for analyzing the contents of layer 3 and above and collect the multicast participation information of its subordinate STAs by itself.

[0193] 《Creating a Receipt Confirmation Subgroup》 Next, in flow F1602, the AP classifies the participating STAs into one or more subgroups for acknowledgment for each multicast group. As will be described later, the AP does not request acknowledgment for multicast transmission from all STAs in the multicast group every time it transmits a multicast, but only from the subgroup.

[0194] After the AP has grasped the multicast group participation status of each STA under its control by flow F1601, the AP first classifies the STAs that are to receive a certain multicast group (hereafter referred to as group members) into those that are to be acknowledged and those that are not. It is not necessary for all group members to be acknowledged for the multicast flow in question.

[0195] The AP then classifies the group members being acknowledged into one or more subgroups, which are the sets of STAs that will simultaneously acknowledge the multicast data frames that will subsequently be transmitted, all of which will of course be chosen from among the members of the multicast group.

[0196] <<Creation of subgroup ancillary information, advance notification of receipt confirmation subgroup and ancillary information>> After classifying the members to be acknowledged into subgroups, the AP further generates auxiliary information for signal separation within the subgroup and a transmission condition for sending an acknowledgement in each subgroup. The transmission condition can be the relationship between the sequence number of the data frame and the subgroup identifier. In this embodiment, each subgroup member transmits an MU-BA when the relationship between the sequence number of the last multicast data frame received by the STA and the following formula (4) is established.

[0197]

number

[0198] Then, in flow F1603, the AP notifies the STAs in the multicast group in advance of information about the created subgroup by using an Ack Group Assignment frame (described above) or a Beaco frame, etc. The information that the AP notifies each member in advance includes the above-mentioned contents (e1) and (e2) as well as the transmission conditions of the subgroup.

[0199] Group members that have received the subgroup information, auxiliary information (e1), (e2), and transmission conditions in advance store them, for example in memory within the control unit 408, and use them when transmitting an acknowledgment response frame (training signal).

[0200] The above steps F1601 to F1603 are related to the preliminary setup, and need only be executed at least once.

[0201] The following processes F1604 to F1607 are repeated processes accompanying the transmission and reception of multicast data. In this embodiment, transmission and reception of multicast data frames and confirmation of receipt are performed between the AP and the multicast groups STA#1 to #6 according to the communication sequence shown in FIG.

[0202] Multicast data transmission and reception In flow F1604, the AP transmits multicast data DATA#0, DATA#1, and DATA#2 in sequence to STAs#1 to #6 in the multicast group as indicated by reference numbers 1501, 1505, and 1509 in FIG.

[0203] In this embodiment, since these multicast data frames also serve as receipt confirmation requests, the AP does not transmit MU-BAR frames. Also, unlike embodiment 3, there is no need to extend the MAC headers of the data frames DATA#0, DATA#1, and DATA#2.

[0204] 《Receipt Acknowledgement Response》 Each STA that has received the multicast data frames 1501, 1505, and 1509 checks in flow F1605 whether the transmission condition previously notified in the Ack Group Assignment frame or beacon frame is satisfied (whether the relational expression (4) between the sequence number and its own subgroup identifier is satisfied). Then, only if the transmission condition is satisfied, the STA transmits the MU-BA frame as shown by reference numbers 1502 to 1504 and reference numbers 1506 to 1508 in FIG. 15. At this time, the STA encodes (as described above) the Long Preamble using the encoding information specified in the target multicast data frame and transmits it. In addition, when transmitting the MU-BA frame, the STA uses the PHY Preamble of the received multicast data frame to correct the frequency offset of the reference oscillator for the AP.

[0205] FIG. 17 shows, in the form of a flowchart, the processing steps that a STA performs in response to receiving a multicast data frame from an AP.

[0206] When a STA receives a multicast data frame from an AP (Yes in step S1701), it checks whether the transmission condition is met (whether the relational expression (4) between the sequence number of the multicast data frame and its own subgroup identifier is met) (step S1702).

[0207] If the transmission condition is not met (No in step S1702), the STA skips all subsequent processes and ends this process.

[0208] On the other hand, if the transmission conditions are met (Yes in step S1702), the STA generates a receipt confirmation response MU-BA from the reception success / failure record of the multicast flow targeted by the multicast data frame (step S1703).

[0209] Next, the STA estimates the path loss from the information of the past reception power (of the packet received from the previous AP including the multicast data frame) and sets the transmission power of the receipt acknowledgment response frame so that the reception power at the AP side becomes a predetermined value (step S1704). Note that this predetermined value is assumed to be shared in advance at least among the STAs of the subgroup members.

[0210] The STA then adds a PHY preamble obtained by encoding a long preamble using the encoding information specified in the multicast data frame, and transmits the MU-BA frame (step S1705).

[0211] In summary, according to the processing flow shown in Figure 17, a STA that receives a multicast data frame checks whether the transmission conditions are met, and transmits an MU-BA frame only if they are met. Since the multicast data frame also serves as an acknowledgment request, there is no need for the AP to transmit an MU-BAR frame. The transmission conditions are determined by the relationship between the sequence number of the multicast data frame and its own subgroup identifier (4), and the STA sets the transmission power when transmitting an MU-BA frame, so there is no need to extend the MAC header of the multicast data frame.

[0212] The timing for transmitting an MU-BA from a STA is a predetermined time after the STA has finished receiving the target multicast data frame. This predetermined time interval is shared between the AP and all STAs, and it is desirable that the interval is such that wireless transmissions from third parties within the communication range cannot interrupt the MU-BA. In this embodiment, SIFS or PIFS as specified in the IEEE802.11 wireless LAN standard may be used. When transmitting, each STA does not need to perform carrier sensing.

[0213] On the AP side, after the SIFS time of the multicast data frame transmission, the MU-BAs from each of the specified STAs are simultaneously received.Then, in flow F1606, the AP disassembles and restores the MU-BAs from the multiple STAs that were simultaneously received by signal processing, for example, according to the processing procedure shown in Fig. 11.

[0214] Multicast data retransmission The AP separates the acknowledgement responses from each of the specified STAs to obtain acknowledgement information, and depending on the result, retransmits the multicast data as flow F1607 if necessary.

[0215] The AP may retransmit the multicast data immediately after receiving the acknowledgment response.

[0216] Also, if burst-like radio interference is detected, such as from a microwave oven, immediate retransmission may fail again. In such a case, the AP may retransmit the multicast data after adding a certain delay. If a delay requirement is specified for the multicast flow (content), the AP shall add a delay that does not exceed that requirement. EXAMPLES

[0217] In the fifth embodiment, the AP acquires channel gain information (CSI) from all STAs participating in the multicast group in advance, and transmits an acknowledgement request to the group member STAs in a separate frame from the data frame.

[0218] In use cases where there is no movement of STAs and there is almost no CSI fluctuation, it is possible to separate the acknowledgement responses by using past CSI information (CSI estimation results in uplink frames such as Association Req) that has been retained for a relatively long time, without obtaining CSI by transmitting in the MU-BA format as shown in Figures 8A and 8B.

[0219] FIG. 18 shows a processing flow in the fifth embodiment.

[0220] Understanding Multicast Groups First, in flow F1801, each STA belonging to a multicast group is assumed to have joined the multicast group it wishes to receive in advance. To join a multicast group, mechanisms such as IGMP and IPv6 MLD are used. Each STA receives the multicast address of the multicast group in which it is participating.

[0221] Each STA that participates in a multicast group notifies the AP of its multicast registration status separately, either at the request of the AP or voluntarily, so that the AP can know the multicast group participation status. Alternatively, the AP may have a mechanism for analyzing the contents of layer 3 and above and collect the multicast participation information of its subordinate STAs by itself.

[0222] In the fifth embodiment, the AP does not create a receipt confirmation subgroup, and does not notify the receipt confirmation subgroup and the attached information in advance.

[0223] The subsequent processing is repeated in association with the transmission and reception of multicast data. Fig. 19 shows an example of a communication sequence for transmitting and receiving multicast data frames between the AP and STAs #1 to #6 and confirming their receipt in this embodiment.

[0224] Multicast data transmission and reception In flow F1802, the AP sequentially transmits multicast data DATA#0, DATA#1, and DATA#2 to STA#1 to STA#6 in the multicast group as shown by reference numbers 1901 to 1903 in Fig. 19. These multicast data frames are transmitted using the normal frame format as shown in Fig. 7 without undergoing the encoding process described above.

[0225] Multicast group member STA#1~#6 stores the reception status of each multicast frame for each sequence number of the multicast data frame. In addition, multicast group member STA#1~#6 uses the PHY preamble of the multicast data frame to correct the frequency offset of the reference oscillator for the AP.

[0226] 《Confirmation of receipt》 In this embodiment, after transmitting one or more multicast data frames, the AP transmits an MU-BAR frame requesting an acknowledgment as flow F1803, as shown by reference numbers 1904 and 1908 in FIG. 19. In this embodiment, the AP writes the identifier of the STA requesting the acknowledgment response BA in the MU-BAR frame, together with the above-mentioned contents (f1), (f4), and (f5). As the identifier of the STA, an individual identifier such as the MAC address of the STA or a connection identifier such as the Association ID (AID) in the AP can be used. The AP does not need to obtain CSI information in advance from all STAs participating in the multicast group and transmit the coding information of the Long Preamble in the MU-BAR frame.

[0227] In addition to transmitting the MU-BAR alone as a single wireless packet as shown in Figure 19, the AP may also transmit the MU-BAR as a single wireless packet in the wireless section by aggregating the MU-BAR and multicast data at the MAC layer using A-MPDU (same as above).

[0228] When each STA that is specified in the MU-BAR frame to request an MU-BA by its individual identifier, connection identifier, etc. receives MU-BAR frames 1904 and 1908 from the AP, the STA transmits, as flow F1804, acknowledgement response BA frames for the corresponding multicast flow, as shown by reference numbers 1905 to 1907 and 1909 to 1911 in Figure 19.

[0229] The acknowledgement response BA frame transmitted here differs from the MU-BAR frame in which the Long Preamble section is encoded (described above) in that the normal preamble format shown in Figure 7 is used, but the contents from the PHY Header section onwards are the same as those of the MU-BA frame.

[0230] FIG. 20 shows, in the form of a flowchart, a processing procedure that a STA executes in response to receiving an MU-BAR frame from an AP.

[0231] When the STA receives an MU-BAR frame from the AP (Yes in step S2001), the STA checks whether its own individual identifier or connection identifier is specified in the MU-BAR frame (step S2002).

[0232] If its own individual identifier or connection identifier has not been specified (No in step S2002), the STA skips all subsequent processes and ends this process.

[0233] On the other hand, if its own individual identifier or connection identifier is specified (Yes in step S2002), the STA generates a receipt confirmation response BA from the reception success / failure record of the multicast flow targeted by the MU-BAR frame (step S2003).

[0234] The STA generates an acknowledgement BA frame that includes information on reception success / failure for each sequence number of the target multicast flow. However, although the target is the multicast flow that was sent from the AP before the MU-BAR frame was received, it is not necessary to include information prior to the start sequence number notified in the MU-BAR frame. In addition, if a frame that has arrived requesting retransmission is determined to be no longer useful by the upper layer of the STA, the STA may notify the frame as successful even if it was not received.

[0235] Next, the STA checks whether or not it has received information on the transmission power to be used in the receipt acknowledgement response BA frame in the MU-BAR frame (step S2004).

[0236] If the STA has received information about the transmission power to be used for the receipt confirmation response BA frame in the MU-BAR frame (Yes in step S2004), the STA sets the transmission power to be used for the receipt confirmation response BA frame as instructed in the MU-BAR frame (step S2005).

[0237] Also, if the STA has not received information on the transmission power to be used in the receipt acknowledgement BA frame in the MU-BAR frame (No in step S2004), the STA estimates the propagation loss from past reception power information (of packets received from the previous AP, including MU-BAR), and sets the transmission power of the receipt acknowledgement BA frame so that the reception power on the AP side becomes a predetermined value (step S2007). Note that this predetermined value is assumed to be shared in advance at least among the STAs that are subgroup members.

[0238] Incidentally, the power used for transmitting the receipt confirmation response BA in steps S2005 and S2007 may be controlled as required.

[0239] The STA then adds a PHY preamble obtained by encoding a Long Preamble using the encoding information specified in the MU-BAR frame, and transmits an acknowledgement response BA frame (step S2006).

[0240] In summary, according to the processing flow shown in Figure 20, a STA that receives an MU-BAR checks whether the individual identifier or connection identifier described in the contents matches its own, and only if they match, transmits a BA frame without encoding the Long Preamble portion.

[0241] The timing for transmitting the acknowledgement response BA from the STA is a predetermined time after the STA has finished receiving the MU-BAR. This predetermined time interval is shared between the AP and all STAs, and is preferably an interval that cannot be interrupted by wireless transmissions from third parties within the communication range. In this embodiment, SIFS or PIFS as specified in the IEEE802.11 wireless LAN standard may be used. When transmitting, each STA does not need to perform carrier sensing.

[0242] On the AP side, after a SIFS time from the transmission of the MU-BAR, the reception acknowledgement responses BA from the designated STAs are simultaneously received. Then, in flow F1805, the AP disassembles and restores the reception acknowledgement responses BA from the multiple STAs that were simultaneously received by signal processing.

[0243] The procedure for receiving and processing a BA acknowledgement from a subgroup member designated by the AP is shown in the form of a flow chart in Figure 21. After sending an MU-BAR, the AP waits for a BA acknowledgement frame from the subgroup and performs processing that differs from normal reception operations.

[0244] When the AP detects a short preamble (Yes in step S2101), the received signal processed by each wireless interface unit 306-1, ... is sent to the channel estimation unit 395, and the short preamble unit synchronizes the frame start timing, synchronizes the frequency, and sets the AGC (Auto Gain Control) (step S2102).

[0245] Then, the spatial signal processor 304 reads out the past CSI information of each STA to be acknowledged, which is stored in advance (step S2103), and restores (disassembles) the acknowledgement response BA from each STA using the CSI information (step S2104). The disassembly process is applied to the signal after the Long Preamble portion (i.e., after the PHY Header portion).

[0246] Multicast data retransmission The AP separates the acknowledgement responses BA from each of the specified STAs to obtain acknowledgement information, and depending on the result, retransmits the multicast data as flow F1806 if necessary.

[0247] The AP may retransmit the multicast data immediately after confirming the acknowledgement response BA.

[0248] Also, if burst-like radio interference is detected, such as from a microwave oven, immediate retransmission may fail again. In such a case, the AP may retransmit the multicast data after adding a certain delay. If a delay requirement is specified for the multicast flow (content), the AP shall add a delay that does not exceed that requirement.

[0249] The method of this embodiment may be used in combination with the advance subgrouping and notification as in embodiment 1. In that case, the subgroup identifier is transmitted in place of the STA identifier in the content (Payload) portion of the MU-BAR.

[0250] Also in this embodiment, similarly to the third and fourth embodiments, the reception confirmation target may be notified by using a multicast data frame instead of an MU-BAR.

[0251] According to the first to fifth embodiments, in wireless multicast delivery, even when there are a large number of receiving terminals, it is possible to improve the reliability of delivery while suppressing the wireless resources used for receipt confirmation. [Industrial Applicability]

[0252] The technology disclosed in this specification has been described in detail above with reference to specific embodiments. However, it is obvious that a person skilled in the art can modify or substitute the embodiments without departing from the gist of the technology disclosed in this specification.

[0253] In this specification, the embodiment in which the technology disclosed in this specification is applied to a wireless communication system based on the IEEE802.11 wireless LAN standard has been mainly described, but the gist of the technology disclosed in this specification is not limited thereto. When multicast transmission is performed in wireless communication systems based on various other wireless standards, the technology disclosed in this specification can be applied to ensure efficient use of wireless resources while improving reliability by using receipt confirmation responses. For example, when the technology disclosed in this specification is applied to a wireless communication system based on the Wi-Fi Direct standard, the access point (AP) can be read as a GO (Group Owner) and the station (STA) as a Client.

[0254] In short, the technology disclosed in this specification has been described in the form of examples, and the contents of the specification should not be interpreted in a limiting manner. In order to judge the gist of the technology disclosed in this specification, the claims should be taken into consideration.

[0255] The technology disclosed in this specification can also be configured as follows. (1) a communication unit that wirelessly communicates with a plurality of slave stations under its control; a control unit that controls data transmission with each slave station via the communication unit; Equipped with the control unit causes the communication unit to perform multicast transmission as a parent station to a plurality of child stations and to request the child stations to acknowledge receipt of the multicast transmission; The communication unit performs a receiving process for receiving acknowledgement responses simultaneously transmitted from a plurality of slave stations. Wireless communication device. (1-1) a step of multicasting to a plurality of slave stations as a master station; requesting a receipt confirmation from a target child station of the multicast transmission; receiving and processing the acknowledgement responses simultaneously transmitted from the plurality of slave stations; A wireless communication method comprising: (1-2) The communication unit aggregates a frame requesting a receipt confirmation from the child station with a multicast data frame and transmits the aggregated frame. A wireless communication device according to (1) above. (2) the control unit selectively requests acknowledgement of receipt from among the child stations participating in the multicast group to which the multicast transmission has been made; A wireless communication device according to (1) above. (2-1) The control unit selectively requests a receipt confirmation based on the state of each child station participating in the multicast group; The wireless communication device according to (2) above. (2-2) the control unit selectively requests a receipt confirmation based on communication quality obtained from past transmissions and receptions to each slave station; The wireless communication device according to (2) above. (2-3) The control unit selectively requests acknowledgement from a child station that requires reliability for multicast. The wireless communication device according to (2) above. (2-4) The control unit divides the slave stations that request the receipt confirmation into subgroups, and requests the receipt confirmation on a subgroup basis. The wireless communication device according to (2) above. (2-4-1) The control unit sets a maximum number of child stations that can participate in a subgroup. The wireless communication device according to (2-4) above. (2-4-1-1) The control unit sets the maximum number based on the number of signals that the communication unit can simultaneously receive and separate. The wireless communication device described in (2-4-1) above. (2-4-2) The control unit subgroups combinations that facilitate signal separation based on wireless channel state information. The wireless communication device according to (2-4) above. (2-4-3) The control unit subgroups combinations that reduce a difference in reception level in the communication unit. The wireless communication device according to (2-4) above. (2-4-4) The control unit causes the communication unit to notify subgroup identification information in advance to a slave station that is to join the subgroup, using a management frame or a beacon frame. The wireless communication device according to (2-4) above. (2-5) the control unit causes the slave station to transmit a request for receipt confirmation using a frame other than the multicast frame; A wireless communication device according to (1) above. (2-6) the control unit causes the child station to transmit a request for receipt confirmation using a part of the multicast frame; A wireless communication device according to (1) above. (2-7) Using the individual identifier or connection identifier of the target slave station, indicate that it is the requestee of the receipt confirmation; The wireless communication device according to (2) above. (2-8) Grouping the slave stations that request the receipt confirmation into a subgroup, and in a case where the subgroup identification information has been notified in advance to the slave stations that will join the subgroup, notifying the slave stations that belong to the subgroup that they are the recipients of the receipt confirmation request using the subgroup identification information; The wireless communication device according to (2) above. (2-9) The control unit determines whether to cause the communication unit to transmit a receipt confirmation response frame based on a combination of a sequence number of the received multicast data frame and subgroup identification information notified in advance from the parent station. The wireless communication device according to (2) above. (3) the control unit designates, via the communication unit, a slave station that is to transmit an acknowledgment response frame and a transmission method of the acknowledgment response frame; the communication unit separates a plurality of receipt confirmation response frames simultaneously received from a plurality of slave stations based on propagation path information between the plurality of slave stations and the own station; A wireless communication device according to (1) above. (4) The designation of the transmission method includes a coding method of the training signal of the receipt confirmation response frame so as to make a format that allows simultaneous transmissions from multiple slave stations to be separated by calculation, the communication unit acquires propagation path information between each of the slave stations from a training signal transmitted from each of the slave stations in accordance with the encoding method. The wireless communication device according to (3) above. (4-1) The communication unit extracts a training signal of each slave station from an orthogonally coded training signal included in a part of the receipt confirmation response frame, and acquires propagation path information between each slave station and the training signal. The wireless communication device according to (4) above. (4-2) the communication unit extracts a training signal of each slave station from a training signal transmitted in a time division manner and included in a part of the receipt confirmation response frame, and acquires propagation path information between each slave station and the training signal; The wireless communication device according to (4) above. (5) The designation of the transmission method includes information on a combination of a modulation method and an error correction coding method of the receipt confirmation response frame. The wireless communication device according to (3) above. (6) the designation of the transmission method includes information on the transmission power of a receipt confirmation response frame; The wireless communication device according to (3) above. (7) When the control unit divides the slave station requesting the receipt confirmation into a subgroup, the control unit notifies the slave station of the designation of the transmission method by a management frame or a beacon frame including subgroup identification information notifying the slave station that the slave station is a member of the subgroup. The wireless communication device according to (3) above. (7-1) when the transmission method includes an encoding method of a training signal portion of a receipt confirmation response frame, the control unit assigns an encoding method of a training signal to each slave station so as not to overlap within a subgroup. The wireless communication device according to (7) above. (8) The wireless communication device according to (3) above, wherein the control unit notifies the designation of the transmission method in a frame requesting confirmation of receipt. (9) a communication unit for wirelessly communicating with the master station; a control unit that controls data transmission with a parent station via the communication unit; Equipped with The communication unit receives a frame that is multicast to a multicast group including the own station, the control unit, when a predetermined condition is satisfied, causes the communication unit to transmit a receipt confirmation response after a predetermined time has elapsed since receiving the multicast transmitted frame. Wireless communication device. (9-1) receiving a frame that is multicast to a multicast group including the own station; transmitting an acknowledgment response after a predetermined time has elapsed since receiving the multicast-transmitted frame when a predetermined condition is satisfied; A wireless communication method comprising: (9-2) in response to receiving a frame requesting an acknowledgement of a multicast transmission from a parent station to the control unit, the control unit causes the communication unit to transmit an acknowledgement of a multicast transmission from the parent station to the control unit after a predetermined time has elapsed since the reception of the multicast frame. The wireless communication device according to (9) above. (10) The communication unit transmits the receipt confirmation response frame using a method for transmitting the receipt confirmation response frame designated by the master station. The wireless communication device according to (9) above. (11) The communication unit encodes a training signal of the receipt confirmation response frame according to a command from the master station and transmits the encoded training signal. The wireless communication device according to (10) above. (11-1) The communication unit encodes the training signal using an encoding method conveyed in a frame requesting receipt confirmation, and transmits the encoded training signal. The wireless communication device according to (10) above. (11-2) When a selective acknowledgement is requested from among the child stations participating in the multicast group to which the multicast transmission has been made, the communication unit transmits the training signal by encoding the training signal using an encoding method that is assigned so as not to overlap with other child stations in the group. The wireless communication device according to (10) above. (12) The communication unit determines a combination of a modulation method and an error correction coding method to be used for the receipt confirmation response frame according to a command from the master station. The wireless communication device according to (10) above. (12-1) The communication unit determines a combination of a modulation scheme and an error correction coding scheme to be used for a receipt confirmation response frame according to a description in a frame from the master station requesting the own station to confirm receipt. The wireless communication device according to (10) above. (13) The communication unit sets a transmission power according to an instruction from the master station and transmits a receipt confirmation response. The wireless communication device according to (10) above. (14) The control unit causes the communication unit to transmit an acknowledgment response frame when its own individual identifier or connection identifier is specified in a multicast data frame or a frame requesting an acknowledgment received from a parent station. The wireless communication device according to (9) above. (15) The control unit causes the communication unit to transmit an acknowledgment response frame when subgroup identification information notified in advance by the parent station is specified as a target in the multicast data frame or the frame requesting an acknowledgment received from the parent station. The wireless communication device according to (9) above. (16) The control unit determines whether to cause the communication unit to transmit a receipt confirmation response frame based on a relationship between a sequence number of the received multicast data frame and subgroup identification information notified in advance by the parent station. The wireless communication device according to (9) above. (17) The communication unit sets a transmission power based on an estimated result of an amount of attenuation in a propagation path between the local station and the master station so that a reception power at the master station becomes a predetermined power, and transmits a receipt confirmation response. The wireless communication device according to (10) above. (18) Operates as an access point of the IEEE 802.11 standard or as a GO (Group Owner) of the Wi-Fi Direct standard. A wireless communication device according to (1) above. (19) Operates as a station conforming to the IEEE 802.11 standard or as a client conforming to the Wi-Fi Direct standard. The wireless communication device according to (9) above. (20) A master station that performs multicast transmission to a plurality of slave stations, requests for receipt confirmation of the multicast transmission from the slave stations, and receives receipt confirmation responses simultaneously transmitted from the plurality of slave stations; A plurality of child stations each receiving a frame that is multicast to a multicast group including the child station, and transmitting an acknowledgment response when a predetermined condition is satisfied and a predetermined time has elapsed since the reception of the multicast frame; A wireless communication system comprising: [Explanation of symbols]

[0256] 100...Data transmission system 110...Wireless slave station, 120...Wireless master station 130…Multicast distribution server 140…Backbone network 201... data source, 202... data processing unit 203…Backbone Communications Department 301: backbone communication unit, 302: data processing unit 303: Modulation / demodulation unit, 304: Spatial signal processing unit 305: Channel estimation unit, 306: Wireless interface unit 307...antenna, 308...control unit

Claims

1. A wireless communication method for wirelessly communicating with a plurality of station devices under an access point device, comprising: A transmission method including a coding method for coding training signals included in a PHY preamble of a receipt acknowledgement response frame transmitted from a plurality of station devices requesting receipt acknowledgement so that the training signals are orthogonal to each other, and a step of multicasting a Multi-User Block Ack Request (MU-BAR) frame including Association IDs (AIDs) of the plurality of station devices; receiving, from the station devices, a plurality of acknowledgement response frames, each of which includes a training signal in a PHY preamble portion, the training signal being encoded according to the encoding method; a step of separating signals subsequent to a PHY preamble portion of the plurality of acknowledgement response frames simultaneously received from the plurality of station devices based on propagation path information between the plurality of station devices and the plurality of station devices acquired from the training signal; A wireless communication method comprising:

2. aggregating and transmitting multicast data frames and MU-BAR frames; The wireless communication method according to claim 1 .

3. Selectively requesting a receipt confirmation from among a plurality of station devices participating in the multicast group to which the multicast transmission has been made; 3. A wireless communication method according to claim 1 or 2.

4. The designation of the transmission method includes information on a combination of a modulation method and an error correction coding method of the plurality of receipt acknowledgment response frames. A wireless communication method according to any one of claims 1 to 3.

5. The designation of the transmission method includes information regarding the transmission power of the plurality of receipt confirmation response frames. A wireless communication method according to any one of claims 1 to 4.

6. A computer program written in a computer-readable format to cause a computer having a wireless communication function to operate as an access point device that wirelessly communicates with a plurality of station devices under its control, the computer comprising: A transmission method including a coding method for coding training signals included in a PHY preamble of a receipt acknowledgement response frame transmitted from a plurality of station devices requesting receipt acknowledgement so that the training signals are orthogonal to each other, and a step of multicasting a Multi-User Block Ack Request (MU-BAR) frame including Association IDs (AIDs) of the plurality of station devices; receiving, from the station devices, a plurality of acknowledgement response frames, each of which includes a training signal in a PHY preamble portion, the training signal being encoded according to the encoding method; a step of separating signals subsequent to a PHY preamble portion of the plurality of acknowledgement response frames simultaneously received from the plurality of station devices based on propagation path information between the plurality of station devices and the plurality of station devices acquired from the training signal; A computer program that executes the following:

7. A wireless communication method for wirelessly communicating as a station device under an access point device, comprising: receiving a Multi-User Block Ack Request (MU-BAR) frame, which is multicast from the access point device and requests a receipt acknowledgement from a plurality of station devices; transmitting an acknowledgement response frame when an association ID (AID) of the own station is specified in the MU-BAR frame and a predetermined time has elapsed since receiving the MU-BAR frame; having In the step of transmitting the receipt confirmation response frame, the receipt confirmation response frame includes, in a PHY preamble portion, a training signal that has been coded in accordance with a transmission method including a coding method for coding training signals of the receipt confirmation response frame transmitted from the own station and another station device, which is specified in the MU-BAR frame, so as to be orthogonal to each other. Wire communication method.

8. The MU-BAR frame is aggregated with a multicast data frame. The wireless communication method according to claim 7.

9. The designation of the transmission method includes information on a combination of a modulation method and an error correction coding method of the receipt confirmation response frame.

9. A wireless communication method according to claim 7 or 8.

10. The designation of the transmission method includes information regarding a transmission power of the receipt confirmation response frame. A wireless communication method according to any one of claims 7 to 9.

11. setting a transmission power so that a reception power at the access point device becomes a predetermined power based on an estimated result of an amount of attenuation of a propagation path between the access point device and the local station, and transmitting the receipt confirmation response; A wireless communication method according to any one of claims 7 to 10.

12. A computer program written in a computer-readable format to cause a computer having a wireless communication function to operate as a station device that wirelessly communicates under an access point device, the computer comprising: receiving a Multi-User Block Ack Request (MU-BAR) frame, which is multicast from the access point device and requests a receipt acknowledgement from a plurality of station devices; transmitting an acknowledgement response frame when an association ID (AID) of the own station is specified in the MU-BAR frame and a predetermined time has elapsed since receiving the MU-BAR frame; Run the command, In the step of transmitting the receipt confirmation response frame, the receipt confirmation response frame includes, in a PHY preamble portion, a training signal that has been coded in accordance with a transmission method including a coding method for coding training signals of the receipt confirmation response frame transmitted from the own station and another station device, which is specified in the MU-BAR frame, so as to be orthogonal to each other. Computer program.

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