Title of the invention: Communication device and communication method
Technical field
[0001]
　The techniques disclosed herein relate to communication devices and communication methods that realize highly efficient and high quality multicast communication.
Background technology
[0002]
　Recently, the introduction of wireless LAN (Local Area Network) technology represented by the IEEE802.11 standard is progressing in public facilities as well. For example, at a stadium, a service is provided that uses wireless LAN technology to distribute video to information terminals carried by spectators such as smartphones. According to such a service, the audience can select and watch a video that cannot normally be seen on TV by selecting their favorite angle.
[0003]
　However, since it is expected that the number of terminals will be enormous, if the above-mentioned video distribution service is to be provided by general one-to-one communication, wireless resources will be tight and high-quality video cannot be distributed. I am concerned.
[0004]
　It is also conceivable to provide a video distribution service using one-to-many communication such as multicast or broadcast, but an error correction function or a retransmission function is further required to maintain high quality of the distributed video. In order to set the function, it is necessary to exchange the delivery destination, and as a result, the wireless resource becomes tight.
[0005]
　For example, the Block Acck method (see, for example, Patent Document 1) in which frame aggregation (multiplexing) for speeding up communication and Acck frames for a plurality of MAC (Media Access Control) frames for improving transmission efficiency are grouped together. That), etc. are known. However, in order to use this kind of data exchange method, it is necessary to carry out a sequence for making a predetermined setting between transmission and reception for the number of terminals of the video distribution destination, which makes wireless resources tight.
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Unexamined Patent Publication No. 2012-19459
Outline of the invention
Problems to be solved by the invention
[0007]
　An object of the technique disclosed in the present specification is to provide a communication device and a communication method capable of performing a reception / rejection response without complicated connection settings and realizing highly efficient and high-quality multicast communication. ..
Means to solve problems
[0008]
　Technology disclosed herein has been made in consideration of the above problems, a first aspect is
　a communication unit for transmitting and receiving signals,
　and a control unit for controlling the transmission and reception of the signal
comprises a The
　control unit is a
communication device that controls transmission of an induced signal that induces transmission of a reception availability response signal to the transmission signal to one or more destination stations that have transmitted the signal .
[0009]
　Specifically, the communication device according to the first aspect operates as a base station, transmits a multicast signal to a plurality of subordinate terminal stations, and induces transmission of a reception availability response signal to the multicast signal. The induced signal is transmitted.
[0010]
　A second aspect of the technique disclosed herein is
　the step of transmitting a signal to the destination station and transmitting to the
　destination station an induced signal that induces transmission of a reception availability response signal to the signal.
It is a communication method having a step and .
[0011]
　Further, a third aspect of the technology disclosed herein,
　a communication unit for transmitting and receiving signals,
　and a control unit for controlling the transmission and reception of the signal
comprises a,
　the control unit may transmit the reception possibility response signal
It is a communication device that controls the transmission of the reception availability response signal in response to the reception of the induction signal that induces the reception .
[0012]
　Specifically, the communication device according to the third aspect operates as a terminal connected to the base station, and is transmitted from the base station in response to receiving the induced signal from the base station. It is configured to transmit a reception availability response signal for a multicast signal.
[0013]
　A fourth aspect of the technique disclosed herein is a 　receiveability response signal to the signal in response
　to the step of receiving the signal and the reception of
the induced signal inducing the transmission of the reception availability response signal. Is
a communication method having a step of transmitting .
Effect of the invention
[0014]
　According to the technique disclosed in the present specification, it is possible to provide a communication device and a communication method that can perform a reception acceptance / rejection response without performing complicated connection settings and realize high-efficiency and high-quality multicast communication. ..
[0015]
　The effects described in the present specification are merely examples, and the effects of the present invention are not limited thereto. In addition, the present invention may exert additional effects in addition to the above effects.
[0016]
　Still other objectives, features and advantages of the techniques disclosed herein will become apparent by more detailed description based on embodiments and accompanying drawings described below.
A brief description of the drawing
[0017]
[Fig. 1] Fig. 1 is a diagram showing an example of a multicast communication sequence that enables a reception / rejection response from a terminal.
FIG. 2 is a diagram showing a configuration example of a frame for transmitting a reception availability response signal.
FIG. 3 is a diagram showing a configuration example of a trigger frame (Random NACK Trigger) that induces transmission of a reception availability response signal.
FIG. 4 is a diagram showing an example of a multicast communication sequence including size adjustment of a reception / rejection response signal.
[Fig. 5] Fig. 5 is a flowchart showing an example of a processing procedure for a communication device operating as an AP to perform multicast communication while causing a terminal to make a reception / rejection response.
FIG. 6 is a flowchart showing an example of a processing procedure for a communication device operating as a terminal under the AP to receive a frame multicast transmitted from the AP and to make a reception / rejection response.
FIG. 7 is a diagram showing a configuration example of a communication device 700.
[Fig. 8] Fig. 8 is a diagram showing an example of a series of packet switching sequences from a terminal connecting to a base station to establishing one-to-one communication.
Mode for carrying out the invention
[0018]
　Hereinafter, embodiments of the techniques disclosed in the present specification will be described in detail with reference to the drawings.
[0019]
　At stadiums and the like, services are provided that distribute video to information terminals carried by spectators using wireless LAN technology such as IEE802.11. However, since it is expected that the number of terminals will be enormous, there is a concern that high-quality video cannot be delivered due to the tightness of wireless resources when trying to provide a video distribution service by general one-to-one communication.
[0020]
　It is also conceivable to provide a video distribution service using one-to-many communication such as multicast or broadcast, but an error correction function or a retransmission function is further required to maintain high quality of the distributed video. Communication with the delivery destination is required to set the function, and wireless resources become tight.
[0021]
　FIG. 8 shows an example of a series of packet switching sequences from when a terminal (STAtion: STA) connects to a base station (Access Point: AP) to establish one-to-one communication.
[0022]
　First, the STA_1 transmits a probe request to the AP determined as the connection destination, and inquires whether or not it is the ESS (Exted Service Set) -ID set by the STA_1. On the other hand, if the AP has the same ESS-ID, the AP returns a probe response. However, this procedure can be omitted by the STA_1 receiving a beacon (Beacon) from the AP.
[0023]
　After that, STA_1 sends an authentication request to the AP, and the AP returns an authentication response to the AP. Subsequently, the STA_1 sends a connection request (Association Request) to the AP, and the AP returns a connection response (Association Response). Then, data communication becomes possible between the AP and the STA_1 through a procedure for key exchange between the AP and the STA_1.
[0024]
　For example, in order for the AP installed in the stadium to establish a link with other terminals STA_2, ..., STA_N in the stadium, the same communication sequence as above must be repeatedly executed for each terminal.
[0025]
　In order to enable a reception acceptance / rejection response (Ack) between the AP and the STA_1, the STA_1 further sends an Ac Request, and if the AP responds to the Ac Request, an Ac Response is returned.
[0026]
　Also, when setting the GCR (GroupCast with Relay) required for high-quality video reception, it is necessary to carry out a communication sequence similar to the above (GCR is for multicast communication adopted in IEEE802.11aa). It is a mechanism that enables reception / rejection response.) Further, in order to perform a batch reception availability response (Block ACK) for a plurality of frames, the ADDBA (Add Block Ac) Request frame that requests negotiation from the receiving side and the ADDBA Response frame that is returned from the receiving side are exchanged. Therefore, it is necessary to negotiate in advance between the transmitting side and the receiving side to set the communication quality such as the modulation method and the transmission rate. When using the above GCR, a sequence for its setting is also required.
[0027]
　As described above, the complicated exchange as described above is required only by setting the connection with one terminal. If the AP installed in the stadium tries to deliver high-quality video to a huge number of terminals in the stadium, wireless resources may be exhausted only by the exchange related to the connection setting.
[0028]
　Therefore, in the present specification, it is possible for the STA to make a reception / rejection response without performing complicated connection settings between the AP and the STA (in other words, without wasting radio resources for the connection settings). The technology for realizing high-quality multicast communication will be disclosed below.
[0029]
　The technology disclosed in the present specification can be applied to both multicast communication and broadcast communication. In the following, for the sake of convenience, only "multicast communication" will be described in a unified manner, but it should be understood that it can be interpreted as "broadcast communication".
[0030]
　FIG. 1 shows an example of a multicast communication sequence that enables a reception / rejection response from a terminal to which the technique disclosed in the present specification is applied. However, the horizontal axis of the illustrated communication sequence is the time axis.
[0031]
　The illustrated communication sequence is an example in which a certain AP multicasts a frame such as video data to three terminals STA_1, STA_2, and STA_3 within a communicable range (or signal reach range). For the sake of simplification of the drawings, the AP communicates with three terminals, but it should be understood that the same operation is possible when performing multicast communication with four or more terminals. Further, it should be understood that the same communication sequence as in FIG. 1 is possible when the AP is installed in the stadium and multicast communication is performed to a huge number of terminals in the stadium.
[0032]
　Each multicast frame transmitted by the AP is an MPDU (MAC Protocol Data Unit). Further, the plurality of MPDUs # 1 to # 4 that the AP continuously transmits by multicast are A-MPDUs (Aggression MPDUs) that are concatenated including the MAC header. Therefore, each terminal STA_1, STA_2, and STA_3 can independently respond to each of the plurality of multicast-transmitted MPDUs # 1 to # 4. It is also assumed that these MPDUs # 1 to # 4 are encrypted in advance using the keys provided by the AP to the terminals STA_1, STA_2, and STA_3 (hereinafter, the same applies).
[0033]
　Each terminal STA_1, STA_2, and STA_3 detects whether or not reception is possible for each frame multicast transmitted from the AP, and sequentially stores the detection result.
[0034]
　Then, after transmitting a certain number of MPDUs, the AP transmits a trigger frame (Trigger Frame) for inducing transmission of a reception availability response signal to each terminal STA_1, STA_2, and STA_3 at an appropriate timing.
[0035]
　As will be described in detail later, the trigger frame transmitted here indicates a plurality of candidate areas capable of transmitting the reception / rejection response signal, and the terminal receiving the candidate regions randomly selects the candidate regions and transmits the reception / rejection response signal. be able to. Such a trigger frame is also referred to as a random trigger frame (Random NACK Trigger (R-NACK Trigger)) in the present specification. The trigger frame itself is defined by IEEE802.11ax as a frame that allows uplink channel access.
[0036]
　Each terminal STA_1, STA_2, STA_3 that has received the trigger frame (R-NACK Trigger) sends a reception enablement / rejection response (NACK) signal indicating the MPDU that could not be received according to the information described in the trigger frame, and sets the trigger frame. It is transmitted after a predetermined time after receiving it.
[0037]
　In the communication sequence example shown in FIG. 1, it is shown that the trigger frame is the target of the reception acceptance / rejection response for the four MPDUs # 1 to # 4 transmitted by multicast. Further, as will be described in detail later, the trigger frame is in the frequency domain (MPDU NACK area) allocated for transmitting the reception availability response signal to the MPDU that is the target of the reception availability response, or in each MPDU NACK region. Information for setting a candidate area for transmitting a reception availability response signal provided in the trigger frame is described in the trigger frame.
[0038]
　Each terminal STA_1, STA_2, STA_3 is induced by a trigger frame, and is received or rejected by using any one candidate region randomly selected in each MPDU NACK region corresponding to the MPDU detected as unreceivable. Notifies the AP of the MPDU that could not be received by transmitting.
[0039]
　In the communication sequence example shown in FIG. 1, since STA_1 detected that MPDU # 2 among the multicast-transmitted MPDUs # 1 to # 4 could not be received, it was induced by the trigger frame and received MPDU # 2. A reception availability response signal is transmitted within the MPDU # 2NACK area assigned to the acceptance / rejection response. Similarly, since STA_2 has detected that MPDU # 2 could not be received, it transmits a reception availability response signal within the MPDU # 2 NACK area assigned to the reception enablement / rejection response of MPDU # 2 induced by the trigger frame. To do. Similarly, since STA_3 detected that MPDU # 2 and # 4 could not be received, the MPDU # 2 NACK area induced by the trigger frame and assigned to each of the reception enable / fail responses of MPDU # 2 and # 4 And the reception availability response signal is transmitted in both the MPDU # 4 NACK area.
[0040]
　In the AP, the MPDU corresponding to each individual MPDU NACK area in which the reception availability response signal is detected is included in the entire frequency domain allocated to the transmission of the reception availability response signal to the plurality of MPDUs to be confirmed for reception availability. It is possible to recognize that the signal could not be received by any of the destination terminals and determine that the signal should be resent. In the communication sequence example shown in FIG. 1, the AP could not receive MPDU # 2 and MPDU # 4 at either terminal, and MPDU # 2 could not receive more terminals, so that the AP was retransmitted. It can be recognized that the priority is high. Then, the AP can guarantee the communication quality for each terminal by retransmitting the MPDU # 2 having a high priority.
[0041]
　The reception availability response signal transmitted by each terminal is a radio wave signal transmitted with a transmission power equal to or higher than a predetermined value in the frequency domain (NACK area for each MPDU) assigned to each target MPDU, and specific data is transmitted. It does not have to be superimposed. Further, on the AP side, it is determined whether or not the reception availability response signal for the corresponding MPDU has been received only by whether or not the reception power (energy) equal to or higher than the predetermined value can be detected in the frequency domain assigned to each MPDU NACK region. To do. Therefore, the AP can determine whether or not the corresponding MPDU should be retransmitted only by the received signal strength in the NACK region for each MPDU, and it is not necessary to demodulate and decode the received signal.
[0042]
　In the present embodiment, the frequency size (Individual Signal Size) used for one reception / rejection response signal is set to 1/N of the frequency size allocated to the NACK area for each MPDU (however, N is an integer of 2 or more). ), A plurality of (N) candidate areas are provided in the NACK area for each MPDU. On the terminal side, one of N in the NACK area for each MPDU corresponding to the MPDU that could not be received is randomly selected, and a reception availability response signal is returned to the AP. Transmission of a reception availability response signal using a randomly selected candidate region is also referred to as Random NACK Transition in the present specification. Through the Random NACK Transition, the AP can simultaneously receive reception / rejection response signals in a maximum of N candidate regions for one MPDU, and can grasp that at least N terminals could not receive the MPDU. Become. However, if more than N terminals simultaneously transmit reception availability response signals, or if two or more terminals select the same candidate area and transmit reception acceptance / rejection response signals, the AP will NACK each MPDU. It is not possible to accurately grasp the number of terminals from the number of candidate areas of the reception availability response signal received in the area.
[0043]
　The AP can recognize the number of terminals that could not receive the corresponding MPDU based on the number of candidate regions that received the reception availability response signal in each MPDU NACK area, and retransmits the MPDU according to the number of terminals. Control can be performed. For example, when the time resource that can be used for retransmission is limited, the AP preferentially retransmits the MPDU having a large number of terminals that have returned the reception availability response signal.
[0044]
　In the communication sequence example shown in FIG. 1, N = 2, that is, two candidate regions are provided in the NACK region for each MPDU. Then, the reception acceptance / rejection response signal was returned to each of MPDU # 2 and # 4, but the reception acceptance / rejection response signals were returned to MPDU # 2 by the three terminals STA_1, STA_2, and STA_3. Only one terminal STA_3 returns a reception availability response signal to MPDU # 4. Since the AP receives the reception availability response signal in the two candidate regions for MPDU # 2, it can determine that at least two terminals could not receive MPDU # 2. Further, since the AP receives the reception availability response signal in only one candidate area in MPDU # 4, it can be determined that at least one terminal could not receive MPDU # 4. Therefore, the AP determines that the MPDU having a larger number of received reception / rejection responses has a higher retransmission priority, and at the next transmission timing, only the MPDU # 2 having a higher retransmission priority is retransmitted.
[0045]
　Here, if the number of candidate areas provided in the NACK area for each MPDU is smaller than the number of terminals under the AP, for MPDUs that many terminals could not receive, a plurality of terminals randomly have the same candidate area. Is selected to increase the possibility of transmitting a reception availability response signal. In such a situation, even if it is possible to determine the MPDU (or MPDU that needs to be retransmitted) in which the terminal that could not be received exists, it is difficult to grasp the number of terminals that could not be received. There is a concern that the priority of retransmission cannot be accurately determined among the plurality of MPDUs to which the pass / fail response signal has been returned. In this case, the Individual Signal Size may be reduced to increase the number N of candidate regions provided in the NACK region for each MPDU so that the subordinate terminals do not duplicately select the same candidate region.
[0046]
　FIG. 2 shows a configuration example of a frame for the terminal of the transmission destination of the MPDU to transmit the reception availability response signal to the AP. However, in the figure, the horizontal axis is the time axis and the vertical axis is the frequency axis. This frame is composed of a common preamble area and a signal in which reception availability response signals placed in one candidate area selected from each MPDU NACK area assigned to each MPDU that the terminal could not receive are connected in the time direction.
[0047]
　As shown in the figure, first, all usable frequency domains are set to the common preamble domain, and preamble transmission is performed. This is for legacy countermeasures in the IEEE802.11 system, and is similar to the Triggered PDU (PLCP (Physical Layer Convergence Protocol) Protocol Data Unit) defined in IEEE802.11ax.
[0048]
　Then, after performing the preamble transmission, the terminal selects a region for one Individual Signal Size, which is a small frequency size, and transmits a reception availability response signal. Specifically, the entire frequency domain (Random Access Resource Size) that can be used for transmitting the reception availability response signal is divided by the number of MPDUs targeted for the reception acceptance / rejection response, and the reception availability response signal is transmitted for each MPDU. A NACK area is provided for each allocated MPDU. In the illustrated example, N MPDUs of MPDU # 1 to # N transmitted by multicast are targeted for reception acceptance / rejection response, and the entire frequency region is N MPDU-by-NACK regions (MPDU # 1 NACK region, MPDU #). It is divided into 2 NACK areas, ..., MPDU # N NACK areas).
[0049]
　Each NACK region for each MPDU is further divided into a plurality of smaller candidate regions with a smaller frequency size Individual Signal Size. The Individual Signal Size corresponds to the frequency width used by one receiveability response signal. When the terminal cannot receive any of the plurality of MPDUs transmitted in succession, one candidate selected from the MPDU-by-NACK area assigned to each of the MPDUs that could not be received after the common preamble area. A reception availability response signal (electric power) is connected to the area to transmit a frame (in FIG. 2, when the terminal cannot receive MPDU # 1, ..., MPDU # N, within each MPDU NACK area. An example is shown in which the reception availability response signal (power) is placed in a randomly selected candidate area (displayed in gray). Therefore, in one MPDU NACK area, the terminals for the number of MPDU NACK areas divided by the Individual Signal Size can simultaneously transmit (individually) receive / reject response signals without duplication.
[0050]
　When the terminal that is the destination of the A-MPDU multicast transmitted from the AP detects that it could not receive for any of the MPDUs, it is one Random Signal Size from the NACK area for each MPDU corresponding to that MPDU. Candidate areas are randomly selected, and a reception availability response signal is transmitted using the candidate areas (Random NACK Multicast).
[0051]
　The reception availability response signal transmitted by each terminal is a radio wave signal transmitted with a transmission power equal to or higher than a predetermined value within the corresponding MPDU NACK area, and it is not necessary to superimpose specific data. Further, on the AP side, whether or not the reception availability response signal for the corresponding MPDU can be received only by whether or not the reception power (energy) equal to or higher than the predetermined value can be detected in the frequency domain (NACK region for each MPDU) assigned to each MPDU. To judge. Therefore, the AP can determine whether or not the corresponding MPDU should be retransmitted only by the received signal strength in the NACK region for each MPDU, and it is not necessary to demodulate and decode the received signal.
[0052]
　In the signal format example shown in FIG. 2, a plurality of MPDU NACK regions are multiplexed in the frequency axis direction, but a signal format in which the NACK regions are multiplexed in the time axis direction can also be considered.
[0053]
　FIG. 3 shows a configuration example of the trigger frame 300 that induces the transmission of the reception availability response signal. However, the figure shows only the payload (MAC) part, and the illustration of the Phy Header part is omitted. The trigger frame 300 is a random trigger frame (Random NACK Trigger (R-NACK Trigger)) that induces a reception / rejection response signal to be transmitted to the terminal using a region randomly selected (Random NACK Transition). The AP transmits the illustrated trigger frame 300 to each terminal as the transmission destination when executing the retransmission control of the multicast frame.
[0054]
　In the frame type field 301 at the head of the trigger frame 300, a value indicating that it is a random trigger frame is described. In the subsequent Duration field 302, a value indicating a time to be set in the NAV (Network Allocation Vector: transmission prohibition period) is described. In the case of the communication sequence example shown in FIG. 1, a value indicating the time until the terminal completes the transmission of the reception availability response signal (Random NACK Transition) is described in the Duration field. The peripheral terminal that has received the trigger frame 300 suppresses the transmission operation for a period specified by NAV.
[0055]
　In the Receiver Addless field 303, the address (MAC address) of the terminal that is the destination of the trigger frame 300 is described. The terminal designated as the destination of the trigger frame can also be said to be a terminal for which a reception acceptance / rejection response has been requested. The broadcast address may be described in the Receiver Address field 303. Further, in the Transmitter Addless field 304, the address (MAC address) of the AP that is the source of the trigger frame 300 is described.
[0056]
　The Random NACK Trigger Body field 305 corresponds to the frame body of the trigger frame 300. The Random NACK Trigger Body field 305 describes information related to the transmission of the reception availability response signal (Random NACK Transfer) instructed to the terminal designated as the destination in the Receiver Addless field 303. Then, at the end of the trigger frame 300, a frame check sequence (FCS) 306 for detecting and correcting an error in the content of the data described in the trigger frame 300 is added.
[0057]
　In the frame configuration example shown in FIG. 3, the Random NACK Trigger Body field 305 has a Start Frame Number, a Frame Bitmap, a Random Access Resource Size, and an Individual Field Size, which are indicated by reference numbers 311 to 314, respectively. ..
[0058]
　In the Start Frame Number field 311, the first sequence number of the MPDU group (A-MPDU multicast-transmitted by the AP) to be received or rejected is described. In the following Frame Bitmap field 312, the sequence number of the MPDU to be the target of the reception / rejection response (that is, from the first MPDU of the MPDU group to be the reception / rejection response) is entered in order from the first MPDU specified by the Start Frame Number. A bitmap showing the relative position) is described.
[0059]
　For example, when sequence numbers 3, 4, 6, and 7 of the A-MPDUs transmitted by multicast are to be the targets of the reception acceptance / rejection response, the first sequence number 3 is described in the Start Frame Number field 311. In addition, a 5-bit length bitmap indicating that the first, second, fourth, and fifth MPDUs out of the five consecutive sequence numbers 3 to 7 are targeted and the third MPDU is excluded. "11011" is described in the Frame Bitmap field 312.
[0060]
　The start of the MPDU to be received or rejected in the Start Frame Number field 311 is indicated, and the bit position in which "1" is described in the Frame Bitmap field 312 is the relative position from the beginning of the MPDU to be received or rejected. Is shown. Further, the total number of bits whose "1" is indicated in the Frame Bitmap field 312 indicates the total number of MPDUs to be received or rejected.
[0061]
　The Random Access Resource Size field 313 describes the size of the entire frequency domain that can be used to transmit the receiveability response signal. Further, in the Individual Signal Size field 314, the size of one candidate region that can be used for transmitting the reception availability response signal is described. The size referred to here is a size on the frequency axis, and is indicated by, for example, the number of subcarriers. The Random Access Resource Size and the Individual Signal Size are also described in FIG. 2 described above.
[0062]
　The terminal that has received the trigger frame 300 (provided that it is the terminal specified by Receiver Address) divides the Random Access Resource Size by the number of MPDUs that are the targets of the reception availability response, and whether or not reception is possible for each MPDU. A NACK area is provided for each MPDU for transmitting a response signal. However, the number of MPDUs to be received or rejected is the total number of bits indicated by "1" in the Frame Bitmap field (described above).
[0063]
　Then, the terminal can further divide each NACK area for each MPDU by the Individual Signal Size to secure a plurality of candidate areas for transmitting the reception availability response signal. When the terminal responds to a certain MPDU whether or not it can be received, it randomly selects any one of a plurality of candidate areas in the corresponding NACK area for each MPDU and uses the selected candidate area for whether or not to receive. A response signal can be transmitted.
[0064]
　For example, when the Random Access Resource Size is 20 MHz and the Frame Bitmap is 11011, the frequency width of 5 MHz is obtained by dividing the 20 MHz of the Random Access Resource Size by 4, which corresponds to the number of MPDUs to be received or rejected. It is assigned to each NACK area for each MPDU. Further, when the Individual Signal Size is 1 MHz, five candidate regions having a frequency width of 1 MHZ are provided in each NACK region for each MPDU consisting of 5 MHz.
[0065]
　It is possible to appropriately adjust the frequency size of the Individual Signal Size, that is, the reception availability response signal. For example, the AP can describe the frequency size of the adjusted reception / rejection response signal in the Individual Signal Size field 314 in the Randon Trigger Body field 305 of the trigger frame, and notify each terminal to be the multicast transmission destination. ..
[0066]
　When the upper limit of Random Access Resource Size is set, if the number of MPDUs targeted for reception / rejection response increases, the frequency size allocated to one NACK area for each MPDU becomes narrower by that amount. Further, the frequency size (Individual Signal Size) of one reception availability response signal is determined according to the number of terminals requesting reception availability response (or the number of terminals designated as the destination of the trigger frame).
[0067]
　If the Individual Signal Size is increased, the signal is transmitted using more subcarriers, and the power of one reception / rejection response signal is increased, so that the detection sensitivity is increased. However, as the size of the Individual Signal Size is increased, the number of candidate areas that can be provided in the NACK area for each MPDU is reduced, so that the probability that two or more terminals transmit the reception / rejection response signal using the same candidate area is increased. As a result, the AP cannot accurately grasp the number of terminals that could not receive the MPDU, and the accuracy of determining the priority of the MPDU to be resent is also lowered.
[0068]
　On the other hand, if the Individual Signal Size is made smaller, more candidate regions can be provided in the NACK region for each MPDU of the same size. The individual terminals can randomly select different candidate regions and transmit the reception / rejection response signal without overlapping each other. As a result, the granularity for determining the retransmission priority becomes finer, so that the AP can accurately grasp the number of terminals that could not receive the MPDU, and can determine the priority of the MPDU to be resent with high accuracy. .. However, since the number of subcarriers used for transmitting the reception availability response signal is reduced and the reception power is reduced, the detection sensitivity of the reception availability response signal is lowered.
[0069]
　FIG. 4 shows an example of a multicast communication sequence including size adjustment of the reception / rejection response signal. However, the horizontal axis of the illustrated communication sequence is the time axis. In the middle of the communication sequence, the size of the reception availability response signal is switched.
[0070]
　The communication sequence shown in the figure is an example in which a certain AP multicasts a frame such as video data to four terminals STA_1, STA_2, STA_3, and STA_4 within the communicable range (or signal reach range). .. For the sake of simplification of the drawings, the AP communicates with four terminals, but it should be understood that the same operation is possible when performing multicast communication with five or more terminals. Further, it should be understood that the same communication sequence as in FIG. 4 is possible when the AP is installed in the stadium and multicast communication is performed to a huge number of terminals in the stadium.
[0071]
　Further, each multicast frame transmitted by the AP is an MPDU, and a plurality of MPDUs continuously multicast-transmitted are A-MPDUs concatenated including a MAC header. Therefore, each terminal STA_1, STA_2, STA_3, and STA_4 can independently respond to each of the plurality of frames transmitted by multicast (same as above).
[0072]
　First, the AP multicasts two linked MPDUs # 1 and MPDU # 2. It is also assumed that these MPDUs are encrypted using the keys provided in advance by the AP to the terminals STA_1, STA_2, STA_3, and STA_4 (hereinafter, the same applies). Each terminal STA_1, STA_2, STA_3, STA_4 detects whether or not each MPDU multicast transmitted from the AP can be received, and sequentially stores the detection result.
[0073]
　Subsequently, the AP transmits the first trigger frame (Random NACK Trigger) that induces the transmission of the reception availability response signal to each terminal STA_1, STA_2, STA_3, STA_4. On the other hand, each terminal STA_1, STA_2, STA_3, and STA_4 uses a candidate area randomly selected from the NACK area for each MPDU assigned to the corresponding MPDU to receive a reception availability response signal indicating the MPDU that could not be received. , Send each.
[0074]
　In the first trigger frame, the AP designates both MPDU # 1 and MPDU # 2 as targets for the reception acceptance / rejection response, and the Individual NACK area for each MPDU is divided into two candidate areas. The Signal Size is specified. Further, neither STA_1 nor STA_2 could receive either MPDU # 1 and MPDU # 2, and neither STA_3 nor STA_4 could receive only MPDU # 2. That is, MPDU # 1 could not be received by two terminals, whereas MPDU # 2 could not be received by all terminals. However, since the number of candidate regions for receiving the reception enablement / rejection response signal from each MPDU NACK region is also two, the AP has the same retransmission priority for MPDU # 1 and MPDU # 2.
[0075]
　The AP retransmits the two MPDUs # 1 and MPDU # 2 to each terminal STA_1, STA_2, STA_3, and STA_4 based on the result of determining the priority of retransmission.
[0076]
　Subsequently, the AP transmits a second trigger frame (Random NACK Trigger) that induces the transmission of the reception availability response signal to the terminals STA_1, STA_2, STA_3, and STA_4. However, since the AP could not determine the priority of retransmitting the transmission frame in the reception availability response signal induced by the first trigger frame and returned from each terminal STA_1, STA_2, STA_3, STA_4, 2 In the second trigger frame, a half of the previous Individual Signal Size is specified. Therefore, in each NACK area for each MPDU, four candidate areas, which is twice the previous time, are provided.
[0077]
　As in the case of the first multicast transmission, it is assumed that neither STA_1 nor STA_2 can receive either MPDU # 1 and MPDU # 2, and both STA_3 and STA_4 cannot receive only MPDU # 2. Each terminal STA_1, STA_2, STA_3, and STA_4 transmits a reception availability response signal indicating an MPDU that could not be received, using a candidate area randomly selected from the NACK area for each MPDU assigned to the corresponding MPDU. ..
[0078]
　Since the number of candidate areas in the NACK area for each MPDU has doubled, the AP detects reception / rejection response signals in two candidate areas from the NACK area for MPDU # 1, but for MPDU # 2. From the NACK area of ​​the above, reception availability response signals can be detected in three candidate areas. Therefore, the AP accurately determines that MPDU # 2 has a higher retransmission priority than MPDU # 1, and retransmits only MPDU # 2 at the subsequent transmission timing. That is, the AP can improve the efficiency of the frame retransmission process, and by extension, realize high-quality multicast communication with high efficiency.
[0079]
　In the above-described embodiment, the terminal transmits a reception availability response signal corresponding to NACK when the frame from the AP cannot be received, but conversely, reception availability corresponding to ACK when the frame can be received. Even if the response signal is transmitted, high-quality multicast communication can be realized as well.
[0080]
　FIG. 5 shows an example of a processing procedure for a communication device operating as an AP to perform multicast communication while causing a terminal to perform a reception / rejection response according to the technique disclosed in the present specification in the form of a flowchart.
[0081]
　When transmission data (for example, video data) to be multicast to a plurality of terminals is generated in the upper layer (Yes in step S501), the AP creates a multicast frame for transmitting the transmission data (step S502). The multicast frame is, for example, an A-MPDU in which a plurality of MPDUs are concatenated.
[0082]
　Next, the AP sets each parameter in the trigger frame that induces the transmission of the reception availability response signal to each terminal that is the transmission destination of the multicast frame (step S503). In this processing step, parameters (Start Frame Number, Frame Bitmap) for specifying the MPDU that is the target of the reception / rejection response in the multicast frame, and information on the frequency domain that can be used for transmitting the reception / rejection response signal of each MPDU (Start Frame Number). Parameters such as Random Access Resource Size) and information on the size of a candidate region randomly selected for transmission of a reception / rejection response signal (Individual Signal Size) are set.
[0083]
　Then, the AP sequentially transmits a plurality of multicast frames (step S504). Here, it is assumed that a plurality of MPDUs are concatenated and transmitted by the A-MPDU method.
[0084]
　When the multicast transmission for all MPDUs is completed (Yes in step S505), the AP multicasts the trigger frame including each parameter set in step S503 (step S506).
[0085]
　After that, the AP performs reception processing of the reception availability response signal from each terminal of the transmission destination of the multicast frame (step S507).
[0086]
　Then, the AP determines the priority of retransmission of each MPDU based on the reception result of the reception availability response signal for each target MPDU (step 508). If it is presumed that the reception availability response signal cannot be received with sufficient particle size, such as when the priority of retransmission of each MPDU cannot be clearly determined, the AP describes it in the trigger frame to be transmitted later. Adjust to reduce the Individual Signal Size.
[0087]
　When the next transmission timing arrives, the AP retransmits a predetermined number of MPDUs in descending order of priority (step S509). The content of the retransmission process is the same as in steps S502 to 506 described above.
[0088]
　FIG. 6 is a flowchart of an example of a processing procedure for a communication device operating as a terminal under the control of the AP to receive a frame multicast transmitted from the AP and to make a reception / rejection response according to the technique disclosed in the present specification. It is shown in the format of.
[0089]
　The terminal waits for a signal to arrive from the connection-destination AP (step S601). Then, when a signal arrives from the AP (Yes in step S601), the terminal further checks whether the received signal is a data frame (step S602).
[0090]
　Here, it is assumed that a data frame carrying video data or the like is transmitted from the AP as an A-MPDU multicast frame. Further, the frame arriving from the AP is limited to either a data frame or a trigger frame transmitted after the A-MPDU that induces transmission of a reception availability response signal.
[0091]
　Then, when a data frame arrives from the AP (Yes in step S602), the terminal receives and processes the frame (step S603). Here, when the terminal can successfully receive and process the frame, the terminal passes the received data obtained by demodulation and decoding to the upper layer.
[0092]
　Further, when the terminal cannot receive the data frame arriving from the AP (Yes in step S604), the terminal stores the MPDU (step S605). Then, the process returns to step S601 and waits for the next arrival signal from the AP.
[0093]
　On the other hand, the frame arriving from the AP is not a data frame (No in step S602), but is a trigger frame (see FIG. 3) that induces transmission of a reception availability response signal transmitted after transmission of A-MPDU. In the case (Yes in step S606), the terminal executes the transmission processing of the reception availability response signal.
[0094]
　Specifically, the terminal checks whether or not each MPDU designated as the target of the reception availability response in the trigger frame can be received based on the content stored in step S605 (step S607).
[0095]
　If all the MPDUs targeted for the reception availability response can be received (No in step S607), the process returns to step S601 without transmitting the reception acceptance / rejection response signal to the AP, and the next arrival signal from the AP is transmitted. stand by.
[0096]
　If some of the MPDUs that are the targets of the reception availability response cannot be received (Yes in step S607), the candidate areas are selected from the corresponding NACK areas for each MPDU for all the MPDUs that could not be received. Randomly select one by one (step S608), and transmit a reception availability response signal to the AP using the candidate area (step S609). Then, the process returns to step S601 and waits for the next arrival signal from the AP.
[0097]
　FIG. 7 shows a configuration example of a communication device 700 to which the technique disclosed in the present specification can be applied. The communication device 700 can operate as either a base station (AP) or a terminal (STA), for example, in the communication sequence shown in FIG. 1 or FIG.
[0098]
　The communication device 700 includes a data processing unit 701, a control unit 702, a communication unit 703, and a power supply unit 704. Further, the communication unit 703 is further composed of a modulation / demodulation unit 711, a signal processing unit 712, a channel estimation unit 713, a wireless interface (IF) unit 714, and an amplifier unit 715, and an antenna 716 is connected to the amplifier unit 715. Will be done. The wireless interface unit 714, the amplifier unit 715, and the antenna 716 may be a set thereof, and one or more sets may be constituent elements. Further, the function of the amplifier unit 715 may be included in the wireless interface unit 714.
[0099]
　The data processing unit 701 generates a packet for wireless transmission from the data when data is input from the protocol upper layer (not shown), and adds a header for media access control (MAC) or an error. Processing such as addition of a detection code is performed, and the processed data is provided to the modulation / demodulation unit 711 in the communication unit 703. Conversely, when receiving input from the modulation / demodulation unit 711, the data processing unit 701 analyzes the MAC header, detects packet errors, reorders, etc., and provides the processed data to the upper layer of its own protocol. To do.
[0100]
　The control unit 702 controls the transfer of information between each unit in the communication device 700. Further, the control unit 702 sets parameters in the modulation unit 711 and the signal processing unit 712, and schedules packets in the data processing unit 701. Further, the control unit 702 performs parameter setting and transmission power control of the wireless interface unit 714 and the amplifier unit 715.
[0101]
　When the communication device 700 operates as a base station and the control unit 702 transmits a multicast frame such as high-quality video data to a plurality of terminals, a reception availability response signal is sent to each destination terminal. The operation of the communication device 700 is controlled so as to perform the process for transmitting the trigger frame for inducing the transmission of the above and the frame retransmission process based on the reception availability response signal received from each terminal, and the operation is highly efficient and highly efficient. Achieve high-quality multicast communication.
[0102]
　When the communication device 700 operates as a terminal, the control unit 702 performs reception processing of the multicast frame transmitted from the connection destination base station, and multicasts according to the trigger frame transmitted from the base station. The operation of the communication device 700 is controlled so as to perform the transmission processing of the reception availability response signal of each transmitted MPDU. The reception availability response signal is transmitted using a candidate area randomly selected from the NACK area for each MPDU.
[0103]
　At the time of signal transmission, the modulation / demodulation unit 711 encodes, interleaves, and modulates the input data from the data processing unit 701 based on the coding and modulation method set by the control unit 702 to generate a data symbol stream. Then, it is provided to the signal processing unit 712. Further, the modulation / demodulation unit 711 performs the opposite processing to the input from the signal processing unit 712 at the time of receiving the signal, and provides the received data to the data processing unit 701 or the control unit 702.
[0104]
　When transmitting a signal, the signal processing unit 712 performs signal processing on the input from the modulation / demodulation unit 711 and provides one or more obtained transmission symbol streams to the respective wireless interface units 714. Further, when the signal is received, the signal processing unit 712 performs signal processing on the received symbol stream input from each wireless interface unit 714 and provides the signal to the modulation / demodulation unit 711.
[0105]
　If necessary, the signal processing unit 712 performs spatial processing such as spatial multiplexing processing of a plurality of streams at the time of signal transmission and spatial decomposition processing of a plurality of streams of the received signal at the time of signal reception. Therefore, the channel estimation unit 713 calculates the complex channel gain information of the propagation path from the preamble portion and the training signal portion of the input signals from the respective radio interface units 714. The calculated complex channel gain information is used for demodulation processing in the modulation / demodulation unit 711 and spatial processing in the signal processing unit 712 via the control unit 702.
[0106]
　When transmitting a signal, the wireless interface unit 714 converts the input from the signal processing unit 712 into an analog signal, performs filtering and up-conversion to the carrier frequency, and sends the signal to the antenna 716 or the amplifier unit 715. Further, when receiving a signal, the wireless interface unit 714 performs the opposite processing with respect to the input from the antenna 716 or the amplifier unit 715, and provides the data to the signal processing unit 712 and the channel estimation unit 713.
[0107]
　When transmitting the signal, the amplifier unit 715 amplifies the analog signal input from the wireless interface unit 714 to a predetermined power and sends it to the antenna 716. Further, when receiving the signal, the amplifier unit 715 amplifies the signal input from the antenna 716 to a predetermined power with low noise, and outputs the signal to the wireless interface unit 714. In the amplifier unit 715, at least one of the transmission function and the reception function may be included in the wireless interface unit 714.
[0108]
　The power supply unit 704 is composed of a battery power source or a fixed power source, and supplies electric power to each unit in the communication device 700.
Industrial applicability
[0109]
　The techniques disclosed in the present specification have been described in detail with reference to the specific embodiments. However, it is self-evident that one of ordinary skill in the art can modify or substitute the embodiment without departing from the gist of the technique disclosed herein.
[0110]
　The techniques disclosed herein can be applied, for example, to wireless networks based on the IEEE 802.11 standard. However, the scope of application of the technology disclosed in this specification is not limited to a specific communication standard. When it is necessary to provide a high-quality distribution service from one base station to a huge number of terminals, by applying the technology disclosed in this specification, complicated connection between the base station and each terminal is performed. Since it is possible to make a reception / rejection response from each terminal without making any settings (in other words, without wasting wireless resources for connection settings), high-quality multicast communication can be realized.
[0111]
　In short, the techniques disclosed in the present specification have been described in the form of examples, and the contents of the present specification should not be interpreted in a limited manner. In order to determine the gist of the technology disclosed in this specification, the scope of claims should be taken into consideration.
[0112]
　The technique disclosed in the present specification can also have the following configuration.
(1) A communication unit for transmitting and receiving a signal and
　a control unit for controlling the transmission and reception of the signal
are provided, and the
　control unit responds to one or more destination stations that transmit the signal with respect to the transmission signal. A
communication device that controls the transmission of an induced signal that induces the transmission of a signal .
(2) The communication device according to (1) above ,
　wherein the signal is transmitted to a plurality of destination stations, and the induced signal includes information regarding a plurality of candidate regions capable of transmitting a reception availability response signal
.
(2-1)
The communication device according to (2) above , wherein the plurality of candidate regions are frequency-divided and multiplexed on the same time .
(3) The communication device according to (2) above
　, wherein the signal includes a plurality of continuous frames, and the induced signal includes information for designating a frame to be received or rejected
.
(3-1) The information that specifies the frame to be the target of the reception availability response indicates the relative position of the first sequence number of the frame group to be the target of the reception acceptance / rejection response and the other frames to be the target of the reception acceptance / rejection response.
The communication device according to (3) above , which includes information .
(4) The induced signal includes information indicating a candidate region for each frame to be received or rejected.
The communication device according to (3) above.
(5)
The communication device according to any one of (2) to (4) above , wherein the induced signal includes information on the size of the candidate region on the frequency axis .
(5-1) The induced signal further includes information for designating a frame to be
　received and rejected , and information on the size of the entire region that can be used for transmitting the receiveable response signal on the frequency axis. The entire area that can be used for transmitting the response signal is divided by the number of frames for which the reception availability response is to be performed, and each region is assigned to the reception availability response signal transmission area for each frame, and the reception availability response signal transmission area for each frame is further assigned.
The communication device according to (5) above , wherein the number of candidate regions divided by the size on the frequency axis of the candidate regions is assigned to the reception availability response signal transmission region for each frame .
(6)
The communication device according to any one of (3) to (5) above , wherein the control unit determines the priority of frame retransmission based on the number of received reception / rejection response signals .
(7) the control unit, depending on the condition of reception of the reception possibility response signal, the width of the frequency axis of the candidate region, or to adjust the total number of candidate areas per frame,
communication according to (6) apparatus.
(8) When there is no difference in the number of received reception / rejection response signals, the control unit reduces the size of the candidate region on the frequency axis or increases the number of candidate regions allocated for each frame. ,
The communication device according to (7) above.
(9) The
above (1) to (1) to (9), which operate as a base station, transmit a multicast signal to a plurality of subordinate terminal stations, and transmit the induced signal that induces transmission of a reception availability response signal to the multicast signal. The communication device according to any one of 8).
(10) A communication method including a step of transmitting a signal to a destination station and a step
　of transmitting an induced signal inducing transmission of a reception availability response signal to the destination station to the destination station
.
(11) A communication unit for transmitting and receiving a signal and
　a control unit for controlling the transmission and reception of the signal
are provided, and the
　control unit responds to receiving an induced signal inducing transmission of a reception availability response signal. , A
communication device that controls the transmission of reception availability response signals .
(12)
The communication device according to (11) above , wherein the control unit selects one of a plurality of candidate regions designated by the induced signal and transmits a reception availability response signal .
(12-1)
The communication device according to (12) above , wherein the plurality of candidate regions are frequency-divided and multiplexed on the same time .
(13) The communication unit receives the multicast signal, and the
　control unit controls the transmission of the reception availability response signal for the frame designated as the target of the reception acceptance / rejection response by the induced signal among the multicast signals.
The communication device according to any one of (11) and (12) above.
(13-1) the induced signal includes a beginning of the sequence number of the frame group to be subjected to receivability response, information indicating the relative positions of other frames as a target of receivability response
to the (13) The communication device described.
(14)
The communication device according to (13) above , wherein the induced signal transmits a reception availability response signal using a candidate region for each frame indicated by the induced signal .
(15)
The communication device according to any one of (11) to (14) above , wherein the control unit transmits a reception availability response signal having a magnitude on the frequency axis of the candidate region specified by the induced signal. ..
(15-1) The induced signal further includes information for designating a frame to be the target of the reception availability response and information regarding the size on the frequency axis of the entire region that can be used for transmitting the reception acceptance / rejection response signal, and the
　control thereof. The unit divides the entire area that can be used for transmitting the reception availability response signal by the number of frames for which the reception acceptance / rejection response is to be performed, and further divides the reception acceptance / rejection response signal transmission area for each frame by the size on the frequency axis of the candidate region.
The communication device according to (15) above , wherein one of the candidate regions composed of the divided numbers is selected to transmit a reception availability response signal .
(16) operating as a terminal connected to the base station, in response to receiving the induced signal from the base station, transmits a reception possibility response signal for the multicast signal transmitted from the base station,
the ( 11) The communication device according to any one of (15).
(17) A communication method comprising a
　step of receiving a signal and a step of transmitting a reception availability response signal to the signal in response to receiving an induced signal that induces transmission of a reception acceptance / rejection response signal
.
Code description
[0113]
　700 ... Communication device, 701 ... Data processing unit, 702 ... Control unit
　703 ... Communication unit, 704 ... Power supply unit
　711 ... Modulation / demodulation unit, 712 ... Signal processing unit, 713 ... Channel estimation unit
　714 ... Wireless interface unit, 715 ... Amplifier unit
　716 ... Antenna
The scope of the claims
[Claim 1]
　A communication unit for transmitting and receiving a signal and
　a control unit for controlling the transmission and reception of the signal
are provided, and the
　control unit receives a reception availability response signal for the transmitted signal to one or more destination stations that transmit the signal. A
communication device that controls the transmission of an induced signal that induces transmission .
[Claim 2]
The communication device according to claim 1 　,
　wherein the signal is transmitted to a plurality of destination stations, and the induced signal includes information regarding a plurality of candidate regions capable of transmitting a reception availability response signal
.
[Claim 3]
The communication device according to claim 2, 　wherein the signal includes a plurality of consecutive frames, and the
　induced signal includes information for designating a frame to be received or rejected
.
[Claim 4]

The communication device according to claim 3, 　wherein the induced signal includes information indicating a candidate region for each frame to be received or rejected .
[Claim 5]

The communication device according to claim 2, 　wherein the induced signal includes information on the magnitude of the candidate region on the frequency axis .
[Claim 6]

The communication device according to claim 3, 　wherein the control unit determines the priority of frame retransmission based on the number of received reception / rejection response signals .
[Claim 7]

The communication device according to claim 6, 　wherein the control unit adjusts the width of the candidate region on the frequency axis or the total number of candidate regions per frame according to the reception status of the reception availability response signal .
[Claim 8]
　Wherein, when the difference in the number of reception possibility response signal received did not appear, so increasing the number of the candidate space to allocate to reduce the size of the frequency domain of the candidate region or per frame,
claim 7. The communication device according to 7.
[Claim 9]

The communication device according to claim 1, wherein the communication device 　operates as a base station, transmits a multicast signal to a plurality of subordinate terminal stations, and transmits the induced signal that induces transmission of a reception availability response signal to the multicast signal .
[Claim 10]
　A communication method including a step of transmitting a signal to a destination station and a step
　of transmitting an induced signal for inducing transmission of a reception availability response signal to the destination station
.
[Claim 11]
　A communication unit that transmits / receives a signal and
　a control unit that controls the transmission / reception of the signal
are provided, and the
　control unit responds to the reception of an induced signal that induces transmission of a reception / rejection response signal. A
communication device that controls the transmission of response signals .
[Claim 12]

The communication device according to claim 11, 　wherein the control unit selects one of a plurality of candidate regions designated by the induced signal and transmits a reception availability response signal .
[Claim 13]
　The eleventh aspect of claim 11, wherein the communication unit receives a multicast signal, and the
　control unit controls transmission of a reception availability response signal for a frame of the multicast signal designated as a target of reception acceptance / rejection response by the induced signal.
Communication device.
[Claim 14]

The communication device according to claim 13 　, wherein the induced signal transmits a reception availability response signal using a candidate region for each frame indicated by the induced signal .
[Claim 15]

The communication device according to claim 11, 　wherein the control unit transmits a reception availability response signal having a magnitude on the frequency axis of the candidate region designated by the induced signal .
[Claim 16]
　The
eleventh aspect of claim 11, which operates as a terminal connected to a base station and transmits a reception availability response signal to a multicast signal transmitted from the base station in response to receiving the induced signal from the base station. Communication device.
[Claim 17]
　Receiving a signal,
　in response to receiving the induced signal induced transmission of reception possibility response signal, and transmitting the reception possibility response signal to said signal
communication method having.