Patent Publication Number: US-2022232417-A1

Title: Device for transmitting data in wireless av system and device for receiving data in wireless av system

Description:
BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to wireless communication, and more specifically, to an apparatus and method for transmitting data and an apparatus and method for receiving data in a wireless audio/video (WAV) system. 
     Related Art 
     Recently, demand for high-definition and high-quality images such as high definition (HD) images and ultra-high definition (UHD) images has increased in various fields. Since the amount of information or bits to be transmitted relatively increases as image data becomes high-definition and high-quality data, transmission cost may increase when image data is transmitted using a medium such as a conventional wired/wireless broadband line. 
     Meanwhile, the Institute of Electrical and Electronics Engineers (IEEE) 802.11ad standard is a high-speed wireless communication standard operating in a band of 60 GHz or higher. It has signal coverage of about 10 meters but can support throughput of 6 Gbps or more. Since it operates in a high frequency band, signal propagation is dominated by ray-like propagation. Signal quality can be improved as a transmit (TX) or receive (RX) antenna beam is aligned toward a strong spatial signal path. Currently, the IEEE 802.1lay standard, an evolved version of IEEE 802.11ad, is under development. 
     An existing standard such as IEEE 802.11ad or ay series premises multiple access and communication of a plurality of devices. On the other hand, an application of a wireless audio video (AV) system is generally designed on the premise of 1:1 wireless communication (e.g., communication between a wireless set-top box and a wireless TV). Therefore, it is difficult to expect efficient image data transmission when the existing standard is directly applied to the wireless AV system. 
     Accordingly, a procedure of operating the wireless AV system and a communication design method optimized for implementing this procedure are required. 
     SUMMARY 
     The present disclosure provides a scheduling method of a data transmission device and reception device in a wireless audio video (AV) system. 
     The present disclosure also provides a data transmission device and reception device supporting a reverse transmission protocol in a wireless AV system. 
     The present disclosure also provides a data transmission device and reception device performing forward data retransmission in a wireless AV system by suppressing reverse data frame transmission despite a reverse direction grant (RDG). 
     According to an aspect of the present disclosure, there is provided an apparatus for performing data transmission and reception in a wireless AV system. The apparatus includes a communication unit configured to receive from an initiator a forward data frame and reverse direction grant information indicating permission of reverse transmission within a transmission opportunity (TXOP) obtained by the initiator, generate a block ACK frame for the forward data frame to transmit the block ACK frame to the initiator, and buffer a reverse data frame to be transmitted to the initiator, and a processor coupled to the communication unit and configured to obtain AV data from the forward data frame. Herein, the communication unit may set a value of a more data field indicating whether the reverse data frame is present, based on whether at least part of the forward data frame fails in reception and priorities of the forward data frame and the reverse data frame, and may transmit the more data field to the initiator. 
     In an aspect, if the communication unit fails in reception of at least part of the forward data frame, and the forward data frame has a higher priority than the reverse data frame, the communication unit may set the value of the more data field to indicate that the reverse data frame is not present, even if the reverse data frame is buffered. 
     In another aspect, if the communication unit fails in reception of at least part of the forward data frame, and the forward data frame has a higher priority than the reverse data frame, the communication unit may set the value of the more data field to indicate that a transmission timing of the reverse data frame is delayed. 
     As an apparatus for performing data transmission and reception in an AV system, the apparatus includes: 
     a communication unit configured to receive from an initiator a forward data frame and RDG information indicating permission of reverse transmission within a TXOP obtained by the initiator, generate a block ACK frame for the forward data frame to transmit the block ACK frame to the initiator, and buffer a reverse data frame to be transmitted to the initiator; and 
     a processor coupled to the communication unit and configured to obtain AV data from the forward data frame, 
     wherein the communication unit sets a value of a more data field indicating whether the reverse data frame is present, based on whether at least part of the forward data frame fails in reception and priorities of the forward data frame and the reverse data frame, and transmits the more data field to the initiator. 
     In another aspect, the communication unit may delay the transmitting timing of the buffered reverse data frame within a valid transmission time. The valid transmission time may be designed as a time in which data transmitted by the initiator can be validly used. 
     In another aspect, if the communication fails in reception of at least part of the forward data frame, the communication unit may set the block ACK to NACK so that the forward data frame is received again from the initiator. 
     In another aspect, if the communication unit succeeds in reception of the forward data frame, the communication unit may set the value of the mode data field to indicate that the reverse data frame is present, and may transmit at least part of the reverse data frame within a valid transmission time. 
     In another aspect, if it is determined that the reverse data frame is transmitted by exceeding the valid transmission time, the communication unit may transmit a first part of the reverse data frame within the valid transmission time, and may delay a transmission timing of a second part which is the remaining part of the reverse data frame to a next valid transmission time. 
     In another aspect, the forward data frame may be data stored in a buffer of the initiator. The buffer of the initiator may be updated to new data in units of a valid transmission time. 
     According to another aspect of the present disclosure, there is provided an apparatus of performing data transmission and reception in a wireless AV system. The apparatus includes a communication unit configured to obtain a TXOP for transmitting to a responder a forward data frame to be buffered, transmit to the responder the forward data frame and RDG information indicating permission of reverse transmission within the TXOP, and receive from the responder a block ACK frame for the forward data frame, and a processor coupled to the communication unit and coupled to transfer AV data for the forward data frame to the communication unit. The communication unit may receive from the responder a value of a more data field indicating whether the reverse data frame is present, based on whether at least part of the forward data frame fails in reception and priorities of the forward data frame and the reverse data frame. 
     In an aspect, if the responder fails in reception of at least part of the forward data frame, and the forward data frame has a higher priority than the reverse data frame, the value of the more data field may be set to indicate that the reverse data frame is not present, even if the reverse data frame is buffered. 
     In another aspect, if the responder fails in reception of at least part of the forward data frame, and the forward data frame has a higher priority than the reverse data frame, the value of the more data field may be set to indicate to the responder that a transmission timing of the buffered reverse data frame is delayed. 
     In another aspect, the transmitting timing of the buffered reverse data frame may be delayed within a valid transmission time. The valid transmission time may be designed as a time in which the forward data frame can be validly used by the responder. 
     In another aspect, if the responder fails in reception of at least part of the forward data frame, the communication unit may retransmit the forward data frame to the responder. 
     In another aspect, if the responder succeeds in reception of the forward data frame, and the value of the more data field indicate that the revere data frame is present, the communication unit may receive at least part of the revere data frame within a valid transmission time. 
     In another aspect, if it is determined that the reverse data frame is transmitted by exceeding the valid transmission time, the communication unit may receive a first part of the reverse data frame within the valid transmission time, and may delay a reception timing of a second part which is the remaining part of the reverse data frame to a next valid transmission time. 
     In another aspect, the forward data frame to be buffered may be updated to new data in units of a valid transmission time. 
     There is an advantage in that a reverse data frame can be transmitted while enabling retransmission of a forward data frame within a valid transmission time even if transmission of the forward data frame fails, when a reverse direction grant is activated in the wireless AV system supporting a reverse direction grant protocol. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a wireless AV system according to an embodiment of the present disclosure. 
         FIG. 2  is a block diagram showing a wireless data transceiving system according to an embodiment of the present disclosure. 
         FIG. 3  is a conceptual diagram of a case where the wireless data transceiving system according to an embodiment of the present disclosure is implemented according to an IEEE 802.11 series communication protocol. 
         FIG. 4  illustrates a communication procedure based on a reverse direction protocol in a wireless AV system according to an embodiment. 
         FIG. 5  illustrates a communication procedure based on a reverse direction protocol in a wireless AV system according to another embodiment. 
         FIG. 6  and  FIG. 7  illustrate a communication procedure based on a reverse direction protocol in a wireless AV system according to another embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following detailed description illustrates embodiments of a device and method for transmitting wireless data and embodiments of a device and method for receiving wireless data that are provided according to the present disclosure. And, such embodiments do not represent the only forms of the present disclosure. The characteristics and features of the present disclosure are described with reference to exemplary embodiments presented herein. However, functions and structures that are similar or equivalent to those of the exemplary embodiments described in the present specification may be included in the scope and spirit of the present disclosure and may be achieved by other intended embodiments. Throughout the present specification, similar reference numerals will be used to refer to similar components or features. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
     In recent years, the design of display devices, such as TVs, has become important, and display panels have become thinner with the development and evolution of technologies for display panels, such as OLED. However, due to the thickness of a driving circuit that is required in order to drive a display panel, there have been restrictions (or limitations) in manufacturing and designing thinner display panels. Therefore, a technology that is capable of separating components excluding components that are mandatorily required to be physically and electrically connected to the display panel, from the display panel, and equipping the physically or electrically separated components to a separate device (hereinafter referred to as a “main device”) is being considered as a promising technology. In this case, a main device and a display device may be configured to exchange image signals and audio signals based on a wireless communication between the main device and the display device. The present disclosure relates to a wireless AV system, or a wireless display system being equipped with a main device and a display device that are provided as physically and/or electrically independent components, wherein media may be played (or reproduced) based on a wireless communication between the devices. 
       FIG. 1  is a block diagram of a wireless AV system according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , a wireless AV system  10  may include a main device  10 , a display panel device  200 , and a remote control device  300 . 
     The main device  100  may perform an operation of receiving an external signal in a wired or wireless format that is related to audio, video, pictures, images, multimedia, or at least one combination thereof, processing the received external signal by using various methods, so as to generate a data stream or a bitstream, and transmitting the generated data stream or bitstream to the display device  200 . 
     In order to perform such operation, the main device  100  may include an external signal receiver  110 , an external device interface unit  115 , a storage unit  120 , a main controller  130 , a wireless communication unit  140 , and a power supply unit  150 . 
     The external signal receiver  110  may include a tuner  111 , a demodulator  112 , and a network interface unit  113 . 
     The tuner  111  receives an external signal in a wired or wireless format that is related to audio, video, pictures, images, multimedia, or at least one combination thereof. For example, the tuner  111  may select a specific broadcast channel in accordance with a channel selection command and may receive a broadcast signal corresponding to the selected specific broadcast channel. 
     The demodulator  112  may separate the received broadcast signal to a video signal, an image signal, a picture signal, an audio signal, and a data signal related to a broadcast program. And, then, the demodulator  112  may reconstruct (or restore or recover) the separated video signal, image signal, picture signal, audio signal, and data signal to a format that can be outputted. 
     The external device interface unit  115  may receive an application or an application list of a nearby (or neighboring) external device and may deliver (or communicate) the application or application list to the main controller  130  or storage unit  120 . 
     The external device interface unit  115  may provide a connection path between the wireless AV system  100  and an external device. The external device interface unit  115  may receive an external input signal including audio, video, pictures, images, multimedia, or at least one combination thereof from an external device, which is connected to the main device  100  via wired or wireless connection, and may then deliver the received external input signal to the main controller  130 . The external device interface unit  115  may include multiple external input terminals. The multiple external input terminals may include an RF terminal, an RGB terminal, one or more High Definition Multimedia Interface (HDMI) terminals, a USB terminal, a component terminal, an AV terminal, a CI terminal. 
     An external device that is connectable to the external device interface unit  115  may be any one of a set-top box, a Bluray player, a DVD player, a gaming system, a sound bar, a smart phone, a PC, a USB memory, a home theater system. However, these are merely exemplary. 
     The network interface unit  113  may provide an interface for connecting the main device  100  to a wired/wireless network including an internet network. The network interface unit  113  may transmit or receive data to or from another user or another electronic device through an accessed network or another network that is linked to the accessed network. 
     Additionally, some content data stored in the main device  100  may be transmitted to a user or an electronic device, which is selected from other users or other electronic devices that are pre-registered in the main device  100 . 
     The network interface unit  113  may access a predetermined webpage through an accessed network or another network that is linked to the accessed network. That is, the network interface unit  113  may transmit or receive data to or from a corresponding server by accessing a predetermined webpage through the network. 
     Also, the network interface unit  113  may receive contents or data provided from a content provider or a network operator. That is, the network interface unit  113  may receive contents such as movies, advertisements, games, VODs, and broadcast signals, which are provided from a content provider or a network provider, and related information through the network. 
     Additionally, the network interface unit  113  may receive firmware update information and update files provided from a network operator and may transmit data to an internet or content provider or a network operator. 
     The network interface unit  113  may select and receive a wanted application among applications that are open to public, through the network. 
     The storage unit  120  may store programs for performing processing and control of each signal within the main controller  130 , and then the storage unit  120  may store signal-processed image, voice, or data signals. 
     Additionally, the storage unit  120  may perform a function for temporarily storing image, voice, or data signals that are inputted from the external device interface unit  115  or network interface unit  113 , and the storage unit  120  may also store information related to a predetermined image through a channel memory function. 
     The storage unit  120  may store an application or an application list that is inputted from the external device interface unit  115  or network interface unit  113 . 
     The main controller  130  may control the main device  100  by using a user instruction (or command) that is inputted through the remote control device  300 , or by using an internal program, and may access a network in order to be capable of downloading an application or an application list that is wanted by a user to the main device  100 . 
     The main controller  130  enables user-selected channel information to be outputted along with a processed image or audio signal through a display device  200  or an audio output unit  250 . 
     Additionally, the main controller  130  enables an image signal or audio signal, which is inputted from an external device, e.g., a camera or camcorder, through the external device interface unit  115 , to be outputted through the display device  200  or audio output unit  250  in accordance with according to an external device image playback instruction (or command) that is received through the remote control device  300 . 
     The main controller  130  may perform a control operation so that content stored in the storage unit  120 , received broadcast content, or externally input content can be played back (or reproduced). Such content may be configured in various formats, such as a broadcast image, an externally inputted image, an audio file, a still image, an accessed (or connected) web screen, a document file, and so on. 
     The main controller  130  may decode a video, an image, a picture, a sound, or data related to a broadcast program being inputted through the demodulator  112 , the external device interface unit  115 , or the storage unit  120 . Then, the main controller  130  may process the decoded data in accordance with encoding/decoding methods supported by the display device  200 . Thereafter, the main controller  130  may process the encoded data by using various video/audio processing methods, such as compression and encoding, so as to transmit the corresponding data through a wireless channel, thereby generating a data stream or bitstream. Finally, the main controller  130  may transmit the generated data stream or bitstream to the display device  200  through the wireless communication unit  140 . Depending upon the embodiments, the main controller  130  may also bypass the decoded data, without encoding the decoded data in accordance with the encoding/decoding methods supported by the display device  200 , and may directly transmit the decoded data to the display device  200  through the wireless communication unit  140 . 
     The main controller  130  may be configured to implement the functions, procedures, and/or methods of a processor  1130  of a wireless data transmitting device  1100  that are to be described with reference to each embodiment of the present specification. Layers of the wireless interface protocol may be implemented in the processor  1130 . The main controller  130  may be provided in the form of a system on chip (SoC). 
     The wireless communication unit  140  may be operatively coupled to the main controller  130 , for example, as a combination of a wireless communication chip and an RF antenna. The wireless communication unit  140  may receive a data stream or bitstream from the main controller  130 , may generate a wireless stream by encoding and/or modulating the data stream or bitstream into a format that can be transmitted through a wireless channel, and may transmit the generated wireless stream to the display device  200 . The wireless communication unit  140  establishes a wireless link, and the main device  100  and the display device  200  are connected through the wireless link. The wireless communication unit  140  may be configured based on various wireless communication modes, such as short-range wireless communication including Wi-Fi, Bluetooth, NFC, and RFID, or a mobile communication network (e.g., 3G, 4G, and 5G cellular networks). For example, the wireless communication unit  140  may perform communication by using a communication protocol, such as a standard of the IEEE 802.11 series. 
     The power supply unit  150  supplies power to the external signal receiver  110 , the external device interface unit  115 , the storage unit  120 , the main controller  130 , and the wireless communication unit  140 . Methods for receiving power from an external source performed by the power supply unit  150  may include a terminal method and a wireless method. In case the power supply unit  150  receives power by using a wireless method, the power supply unit  150  may include a separate configuration in order to wirelessly receive power. For example, the power supply unit  150  may include a power pick-up unit configured to be magnetically coupled with an external wireless power transmitting device so as to receive wireless power, and a separate communication and control unit configured to perform communication with the wireless power transmitting device in order to receive wireless power and to control transmission and reception of wireless power. 
     The wireless communication unit  140  may also be wirelessly connected to the remote control device  300 , thereby being capable of transferring (or delivering) signals inputted by the user to the main controller  130  or transmitter (or delivering) signals from the main controller  130  to the user. For example, the wireless communication unit  140  may receive or process control signals, such as power on/off, screen settings, and so on, of the main device  100  from the remote control device  300  or may process control signals received from the main controller  130  so that the processed signals can be transmitted to the remote control device  300  in accordance with various communication methods, such as Bluetooth, Ultra Wideband (WB), ZigBee, Radio Frequency (RF), or Infrared (IR) communication, and so on. 
     Additionally, the wireless communication unit  140  may deliver (or communicate) control signals that are inputted from a local key (not shown), such as a power key, a volume key, a setup key, and so on, to the main controller  130 . 
     Subsequently, the display device  200  may process a wireless stream, which is received from the main device  100  through a wireless interface, by performing a reverse process of a signal processing operation that is performed by the main device  100 , and then, the display device  200  may output a display or audio (or sound). In order to perform such operation, the display device  200  may include a wireless communication unit  210 , a user input interface unit  220 , a panel controller  230 , a display unit  240 , an audio output unit  250 , and a power supply unit  260 . 
     The wireless communication unit  210  may be configured as a combination of a wireless communication chip and an RF antenna. The wireless communication unit  210  is connected to the wireless communication unit  140  of the main device  100  through a wireless link and performs wireless communication with the wireless communication unit  140  of the main device  100 . More specifically, the wireless communication unit  210  receives a wireless stream from the wireless communication unit  140  of the main device  100 , demodulates the received wireless stream, and transmits the demodulated wireless stream to the panel controller  230 . The wireless communication unit  210  may be configured based on various wireless communication modes, such as short-range wireless communication including Wi-Fi, Bluetooth, NFC, and RFID, or a mobile communication network (e.g., 3G, 4G, and 5G cellular networks). For example, the wireless communication unit  210  may perform communication by using a communication protocol, such as a standard of the IEEE 802.11 series. 
     The panel controller  230  decodes a signal that is demodulated by the wireless communication unit  210  so as to reconstruct (or recover) a bitstream or data stream. At this point, in case the bitstream or data stream is a compressed stream, the panel controller  230  may decompress or reconstruct the bitstream or data stream. Thereafter, the panel controller  230  may output the bitstream or data stream as a video signal, an image signal, a picture signal, an audio signal, or a data signal related to a broadcast program, and may transmit the signals to the display unit  240 , the audio output unit  250 , and the user input interface unit  220 . 
     The video signal, the picture signal, the image signal, and so on, that are inputted to the display unit  240  may be displayed as a picture corresponding to the inputted picture signal. Alternatively, the picture signal that is processed by the panel controller  230  may be transmitted back to the main device  100  through the wireless communication unit  210  and may then be inputted to an external output device through the external device interface unit  115  of the main device  100 . 
     The audio signal that is processed by the panel controller  230  may be audio-outputted to the audio output unit  250 . Moreover, the audio signal that is processed by the panel controller  230  may be transmitted back to the main device  100  through the wireless communication unit  210  and may then be inputted to an external output device through the external device interface unit  115  of the main device  100 . 
     Meanwhile, the panel controller  230  may control the display unit  240  so as to display a picture (or image). For example, the panel controller  230  may perform control operation, so that a broadcast picture (or image) that is inputted through the tuner  111 , an externally inputted picture (or image) that is inputted through the external device interface unit  115 , a picture (or image) that is inputted through the network interface unit, or a picture (or image) that is stored in the storage unit  120  can be displayed on the display unit  240 . In this case, the picture (or image) that is displayed on the display unit  240  may be a still picture (or image) or a video, and may be a 2D image or a 3D image. 
     The panel controller  230  may be configured to implement the functions, procedures, and/or methods of a processor  1230  included in a wireless data receiving device  1200 , which will be described with reference to each embodiment of the present specification. Additionally, the processor  1230  may be configured to implement the functions, procedures, and/or methods of the wireless data receiving  1200  that will be described with reference to each embodiment of the present specification. 
     The user input interface unit  220  may transmit a signal that is inputted, by the user, to the panel controller  230  or may transmit a signal from the panel controller  230  to the user. For example, the user input interface  220  may receive and process control signals, such as power on/off, screen settings, and so on, of the display device  200  from the remote control device  300 , or may process control signals received from the panel controller  230  so that the processed signals can be transmitted to the remote control device  300  in accordance with various communication methods, such as Bluetooth, Ultra Wideband (WB), ZigBee, Radio Frequency (RF), or Infrared (IR) communication, and so on. 
     The user input interface unit  220  may transmit a control signal, which is inputted through a local key (not shown), such as a power key, a volume key, a setup key, and so on, to the panel controller  230 . 
     The power supply unit  260  supplies power to the wireless communication unit  210 , the user input interface unit  220 , the panel controller  230 , the display unit  240 , and the audio output unit  250 . Methods for receiving power from an external source performed by the power supply unit  260  may include a terminal method and a wireless method. In case the power supply unit  260  receives power by using a wireless method, the power supply unit  260  may include a separate configuration in order to wirelessly receive power. For example, the power supply unit  260  may include a power pick-up unit configured to be magnetically coupled with an external wireless power transmitting device so as to receive wireless power, and a separate communication and control unit configured to perform communication with the wireless power transmitting device in order to receive wireless power and to control transmission and reception of wireless power. 
     The remote control device  300  performs an operation of remotely controlling various features of the main device  100  or the display device  200 , such as power on/off, channel selection, screen setup, and so on. Herein, the remote control device  300  may also be referred to as a “remote controller (or remote)”. 
     Meanwhile, since the main device  100  and the display device  200 , which are shown in  FIG. 1 , are provided only as an example of one embodiment of the present disclosure, some of the illustrated components may be integrated or omitted, or other components may be added according to the specifications of the main device  100  and the display device  200 , which are actually implemented. That is, as necessary, two or more components may be integrated into one component, or one component may be divided into two or more components. In addition, a function that is performed in each block is presented to describe an embodiment of the present disclosure, and a specific operation or device will not limit the scope and spirit of the present disclosure. 
     According to another embodiment of the present disclosure, unlike the example shown in  FIG. 1 , the main device  100  may receive and play-back (or reproduce) an image (or picture) through the network interface unit  113  or the external device interface unit  115  without including the tuner  111  and the demodulator  112 . 
     For example, the main device  100  may be implemented by being divided into an image processing device, such as a set-top box, for receiving broadcast signals or content according to various network services, and a content playback device for playing content input from the image processing device. 
     In this case, an operating method of the wireless AV system  10  according to an embodiment of the present disclosure that will hereinafter be described may be performed not only by the main device  100  and the display device  200 , as described above with reference to  FIG. 1 , but also by one of the divided image processing device, such as the set-top box, or content playback device, which includes an audio output unit  250 . 
     In light of system input/output, the main device  100  may be referred to as a wireless source device that wirelessly provides a source, and the display device  200  may be referred to as a wireless sink device that wirelessly receives a source. The wireless source device and the wireless sink device may implement wireless display (WD) communication technologies that are compatible with standards such as wireless HD, wireless home digital interface (WHDI), WiGig, wireless USB, and Wi-Fi display (WFD, which also known as Miracast). 
     In light of the applications, the main device  100  may be integrated to a form that configures part of a wireless set-top box, a wireless gaming console, a wireless digital video disc (DVD) player, a wireless router, or the like. In this case, the main device  100  may be provided as a wireless communication module or a chip. The display device  200  may be integrated to a form that configures part of a user device or electronic device (e.g., a wireless TV, a wireless monitor, a wireless projector, a wireless printer, a wireless vehicle dashboard display, a wearable device, an augmented-reality (AR) headset, a virtual-reality (VR) headset, or the like) having a display panel so as to display an image and a video. In this case, the display device  200  may be provided in the form of a wireless communication module or chip. 
     The main device  100  and the display device  200  may be integrated to forms that configure parts of a mobile device. For example, the main device  100  and the display device  200  may be integrated into a mobile terminal including a smartphone, a smartpad, a tablet PC, or other types of wireless communication devices, a portable computer having a wireless communication card, a personal digital assistant (PDA), a portable media player, a digital image capturing device, such as a camera or camcorder, or other flash memory devices having wireless communication capabilities. In this case, the main device  100  and the display device  200  may be provided in the form of wireless communication modules or chips. 
     Smartphone users may perform streaming or mirroring of a video and an audio, which are outputted by the users&#39;smartphones, tablet PCs, or other computing devices, to another device, such as a television or a projector, in order to provide a higher resolution display or other enhanced user experience. 
     As described above, the main device  100  may receive an external signal in a wired or wireless format that is related to a medium, such as audio, video, a picture, an image, multimedia, or at least one combination thereof, and the main device  100  may process the received external signal by using various methods, so as to generate a data stream or bitstream, and may transmit the data stream or bitstream to the display device  200  through a wireless interface. 
     Hereinafter, image (or picture)/video/audio data that are transmitted through a wireless interface will be collectively referred to as wireless data. That is, the main device  100  may wirelessly communicate with the display device  200  and may transmit wireless data. Therefore, in light of a wireless data transceiving system  1000 , the main device  100  may be referred to as a wireless data transmitting device  1100 , and the display device  200  may be referred to as a wireless data receiving device  1200 . Hereinafter, the present disclosure will be described in more detail in light of the wireless data transceiving system  1000 . Firstly, a detailed block diagram of the wireless data transceiving system  1000  will be illustrated. 
       FIG. 2  is a block diagram showing a wireless data transceiving system according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , a wireless data transceiving system  1000  refers to a system that wirelessly transmits and receives a data stream. And, the wireless data transceiving system  1000  includes a wireless data transmitting  1100  and at least one wireless data receiving device  1200 . The wireless data transmitting device  1100  is communicatively coupled to the at least one wireless data receiving device  1200 . 
     According to an aspect, the data may be configured of an audio, a video, a picture, an image, multimedia, or at least one combination thereof. 
     According to another aspect, the data may include a bitstream in the form of a compressed audio, a bitstream in the form of a compressed video, a bitstream in the form of a compressed picture, a bitstream in the form of compressed multimedia, or at least one combination thereof. In this case, the wireless data transceiving system  1000  may also be referred to as a wireless compressed data stream transceiving system. Additionally, the wireless compressed data stream transceiving system  1000  may further include a functional or physical unit for compressing data. 
     Referring to the detailed configuration of each device, the wireless data transmitting device  1100  includes a processor  1130 , a memory  1120 , and a communication unit  1140 , and the wireless data receiving device  1200  includes a communication unit  1210 , a memory  1220 , and a processor  1230 . 
     The processor  1130  may be configured to implement the functions, procedures, and/or methods of the wireless data transmitting device  1100  that are to be described with reference to each embodiment of the present specification. Also, the processor  1230  may also be configured to implement the functions, procedures, and/or methods of the wireless data receiving device  1200  that are to be described with reference to each embodiment of the present specification. Layers of the wireless interface protocol may be implemented in the processors  1130  and  1230 . 
     In light of the display system in  FIG. 1 , the processor  1130  may be configured to perform the function of the main controller  130 . For example, the processor  1130  may decode a video, an image, a picture, a sound, or data related to a broadcast program that are inputted through the demodulator  112 , the external device interface unit  115 , or the storage unit  120 , may process the decoded data by using various video/audio processing methods, such as compression and encoding, so as to transmit the data through a wireless channel, thereby generating a data stream or bitstream, and may transmit the generated data stream or bitstream to the display device  200  through the communication unit  1140 . 
     The memories  1120  and  1220  are operatively coupled with the processors  1130  and  1230  and store various types of information for operating the processors  1130  and  1230 . 
     The communication units  1140  and  1210  are operatively coupled with the processors  1130  and  1230  and wirelessly transmit and/or receive data. The communication units  1140  and  1210  establish a wireless link  11 , and the wireless data transmitting device  1100  and the wireless data receiving device  1200  are inter-connected through the wireless link  11 . The communication units  1140  and  1210  may be configured based on various wireless communication modes, such as short-range wireless communication including Wi-Fi, Bluetooth, NFC, and RFID, or a mobile communication network (e.g., 3G, 4G, and 5G cellular networks). For example, the wireless communication units  1140  and  1210  may perform communication by using a communication protocol, such as a standard of the IEEE 802.11 series. 
       FIG. 3  is a conceptual diagram of a case where the wireless data transceiving system according to an embodiment of the present disclosure is implemented according to an IEEE 802.11 series communication protocol. 
     Referring to  FIG. 3 , a wireless data transceiving system  20  in (A) of  FIG. 3  may include at least one basic service set (hereinafter referred to as ‘BSS’)  21  and  25 . A BSS is a set consisting of an access point (hereinafter referred to as ‘AP’) and a station (STA) that are successfully synchronized and, thus, capable of communicating with each other. Herein, the BSS does not refer to a specific region (or area). 
     For example, a first BSS  21  may include a first AP  22  and one first STA  21 - 1 . A second BSS  25  may include a second AP  26  and one or more STAs  25 - 1  and  25 - 2 . Herein, the first AP  22  may correspond to the communication unit  1140  of  FIG. 2 , and the one or more STAs  25 - 1  and  25 - 2  may correspond to the communication unit  1210  of  FIG. 2 . 
     An infrastructure BSS  21  and  25  may include at least one STA, APs  22  and  26  providing a distribution service, and a distribution system (DS)  27  connecting multiple APs. 
     The distribution system  27  may implement an extended service set (hereinafter referred to as ‘ESS’)  28 , which is extended by being connected to multiple BSSs  21  and  25 . The ESS  28  may be used as a term indicating one network that is configured by connecting one or more APs  22  and  26  through the distribution system  27 . At least one AP being included in one ESS  28  may have a same service set identification (hereinafter referred to as ‘SSID’). 
     A portal  29  may perform the role of a bridge, which connects the wireless LAN network (IEEE 802.11) with another network (e.g., 802.X). 
     In a WLAN having the structure shown in (A) of  FIG. 3 , a network between the APs  22  and  26  and a network between the APs  22  and  26  and the STAs  21 - 1 ,  25 - 1 , and  25 - 2  may be implemented. 
     Meanwhile, unlike the system shown in (A) of  FIG. 3 , the wireless data transceiving system  30  shown in (B) of  FIG. 3  may be capable of performing communication by establishing a network between the STAs without any APs  22  and  26 . A network that is capable of performing communication by establishing a network between the STAs without any APs  22  and  26  is defined as an Ad-Hoc network or an independent basic service set (hereinafter referred to as ‘IBSS’). 
     Referring to (B) of  FIG. 3 , the wireless data transceiving system  30  is a BSS that operates in the Ad-Hoc mode, i.e., an IBSS. Since the IBSS does not include any AP, a centralized management entity that performs a management function at the center does not exist. Therefore, in the wireless data transceiving system  30 , STAs  31 - 1 ,  31 - 2 ,  31 - 3 ,  32 - 4 , and  32 - 5  are managed in a distributed manner. Here, the STAs  31 - 1 ,  31 - 2 ,  31 - 3 ,  32 - 4 , and  32 - 5  may correspond to the communication unit  1140  or the communication unit  1210  of  FIG. 2 . 
     All STAs  31 - 1 ,  31 - 2 ,  31 - 3 ,  32 - 4 , and  32 - 5  included in the IBSS may be configured as mobile STAs and are not allowed to access a distributed system. All of the STAs included in the IBSS establish a self-contained network. 
     An STA that is mentioned in the present specification is a random functional medium including a medium access control (hereinafter referred to as ‘MAC’) and a physical layer interface for a wireless medium according to the regulations of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and may be used to broadly refer to both an AP and a non-AP STA. 
     An STA that is mentioned in the present specification may be referred to by using various terms, such a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit, and, simply, a user. 
     Referring back to  FIG. 2 , a communication channel that is established by the communication units  1140  and  1210  may be a network communication channel. In this case, the communication units  1140  and  1210  may establish a tunneled direct link setup (TDLS) in order to avoid or reduce network congestion. Wi-Fi Direct and TDLS are used for setting up relatively short-range communication sessions. The communication channel that establishes a wireless link  11  may be a communication channel of a relatively short range or a communication channel that is implemented by using a physical channel structure, such as Wi-Fi using a variety of frequencies including 2.4 GHz, 3.6 GHz, 5 GHz, 60 GHz, or ultra-wideband (UWB), Bluetooth, and so on. 
     While techniques disclosed in the present specification may generally be described in relation with communication protocols, such as the IEEE 802.11 series standard, it will be apparent that aspects of such techniques may also be compatible with other communication protocols. Illustratively and non-restrictively, wireless communication between the communication units  1140  and  1210  may use orthogonal frequency-division multiplexing (OFDM) schemes. Other various wireless communication schemes including, but not limited to, time-division multiple access (TDMA), frequency-division multiple access (FDMA), code-division multiple access (CDMA), or any random combination of OFDM, FDMA, TDMA, and/or CDMA may also be used. 
     The processors  1130  and  1230  may include an application-specific integrated circuit (ASIC), a different chipset, a logic circuit, and/or a data processor. The memories  1120  and  1220  may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and/or another storage device. The communication units  1140  and  1210  may include a baseband circuit for processing radio frequency signals. When an embodiment is implemented as software, the techniques described herein may be implemented as a module (e.g., a procedure, function, and so on) that performs the functions described in the present specification. The module may be stored in the memories  1120  and  1220  and may be executed by the processors  1130  and  1230 . The memories  1120  and  1220  may be implemented inside the processors  1130  and  1230 . Alternatively, the memories  1120  and  1220  may be implemented outside of the processors  1130  and  1230 , and the memories  1120  and  1220  may be communicatively connected to the processors  1130  and  1230  via various well-known means that are disclosed in this technical field. 
     In light of a wireless communication system (i.e., WLAN, Wi-Fi), the wireless data transmitting device  1100  may be referred to as an AP or a personal basic service set control point (PCP) station, and the wireless data receiving device  1200  may be referred to as an STA or a non-personal basic service set control point (non-PCP) station. 
     In light of the input/output of a data stream, the wireless data transmitting device  1100  may be referred to as a wireless source device that wirelessly provides a source, and the wireless data receiving device  1200  may be referred to as a wireless sink device that wirelessly receives a source. The wireless source device and the wireless sink device may implement wireless display (WD) communication technologies that are compatible with standards such as wireless HD, wireless home digital interface (WHDI), WiGig, wireless USB, and Wi-Fi display (WFD, which also known as Miracast). 
     In light of the applications, the wireless data transmitting device  1100  may be integrated to a form that configures part of a wireless set-top box, a wireless gaming console, a wireless digital video disc (DVD) player, a wireless router, or the like. In this case, the wireless data transmitting device  1100  may be provided as a wireless communication module or a chip. And, the wireless data receiving device  1200  may be integrated to a form that configures part of a user device or electronic device (e.g., a wireless TV, a wireless monitor, a wireless projector, a wireless printer, a wireless vehicle dashboard display, a wearable device, an augmented-reality (AR) headset, a virtual-reality (VR) headset, or the like) having a display panel so as to display an image and a video. In this case, the wireless data receiving device  1200  may be provided in the form of a wireless communication module or chip. 
     The wireless data transmitting device  1100  and the wireless data receiving device  1200  may be integrated to forms that configure parts of a mobile device. For example, the wireless data transmitting device  1100  and the wireless data receiving device  1200  may be integrated into a mobile terminal including a smartphone, a smartpad, a tablet PC, or other types of wireless communication devices, a portable computer having a wireless communication card, a personal digital assistant (PDA), a portable media player, a digital image capturing device, such as a camera or camcorder, or other flash memory devices having wireless communication capabilities. In this case, the wireless data transmitting device  1100  and the wireless data receiving device  1200  may be provided in the form of wireless communication modules or chips. 
     Smartphone users may perform streaming or mirroring of a video and an audio, which are outputted by the users&#39;smartphones, tablet PCs, or other computing devices, to another device, such as a television or a projector, in order to provide a higher resolution display or other enhanced user experience. 
       FIG. 4  illustrates a communication procedure based on a reverse direction protocol in a wireless AV system according to an embodiment. This procedure corresponds to a procedure of a reverse direction protocol based on the IEEE 802.11 standard using a radio resource of a 60 HGz band. 
     Referring to  FIG. 4 , an initiator  40  obtains a transmission opportunity (TXOP)  400  and has a right to transmit data to a responder  41  within the TXOP. The responder  41  is a device which receives data from the initiator within the TXOP  400  obtained by the initiator  40 . 
     From a perspective of the wireless AV system, the initiator may be a wireless data transmission device, and the responder may be a wireless data reception device. Alternatively, from the perspective of the wireless AV system, the initiator may be a main device, and the responder may be a display device. Alternatively, from the perspective of the wireless AV system, the initiator may be the display device, and the responder may be the main device. That is, when any one device constituting the wireless AV system is used as the initiator, the other device constituting a pair with that device is used as the responder. Although each embodiment is described hereinafter from perspectives of the initiator and the responder for convenience of explanation, both the initiator and the responder are devices capable of performing data transmission and reception. Therefore, both the initiator and the responder may also be called a data transmission and reception device. 
     A data frame transmitted by the initiator  40  to the responder  41  may be called a forward data frame  410  or a downlink data frame. From a perspective of a medium access control (MAC) layer, the forward data frame  410  may be a MAC protocol data unit (MPDU) or an aggregated MPDU (A-MPDU). From a perspective of a physical (PHY) layer, the forward data frame  410  may be a PHY protocol data unit (PPDU). 
     The responder  41  generates a block ACK frame  420  indicating whether the forward data frame  410  is successfully received and feeds back it to the initiator  40  after a short inter frame space (SIFS). For example, as shown in  FIG. 4 , when at least part of the forward data frame  410  fails in transmission (see  411 ), the responder  41  feeds back the block ACK  420  in which NACK is set for the failed part to the initiator  40 . 
     Meanwhile, the responder  41  may obtain a right to transmit data within the TXOP  400  according to a permission of the initiator  40 . As such, when the initiator  40  grants a data transmission right to the responder  41 , it is called a reverse direction grant (RDG)  412 . In addition, a data frame which is transmitted to the initiator  40  when the responder  41  receives the RDG  412  may be called a reverse data frame  430  or an uplink data frame. Therefore, the responder  41  for which a data transmission right is granted (RDG=1) by means of the RDG  412  may transmit to the initiator  40  a more data field indicating that a buffered reverse data frame is present, and then may transmit the buffered reverse data frame  430  to the initiator  40  after the SFIS. The more data field may also be called a more PPDU field. 
     When the RDG is activated in such a series of the reverse direction protocol procedures, the initiator and the responder may be respectively called an RD initiator and an RD responder. 
     Meanwhile, the initiator  40  may identify that a loss occurs in part of the forward data frame  410  from the block ACK frame  420  of the responder, and thus may prepare for retransmission of the forward data frame  410 . Since the data transmission right is granted to the responder  41 , the initiator  40  may identify that there is data to be transmitted by the responder  41  by means of the more data field. In this case, even if at least part of the forward data frame  410  fails in transmission, the initiator  40  receives the reverse data frame  430  transmitted by the responder  41 , instead of retransmitting the forward data frame  410 . 
     Since the wireless AV system is characterized in that seamless streaming data transmission is achieved wirelessly and reproduced in an AV manner, it is very sensitive to delay. Therefore, every data frame shall be transmitted within a time meaningful for a streaming service, which is called a valid transmission time  440 . The valid transmission time  440  is preferably designed as a time in which each data frame (or buffered data frame) transmitted by the initiator  40  can be validly used by the responder  41 , and may be, for example, 500 us. The valid transmission time may be predetermined when designing the wireless AV system, or may be separately determined by transmitting and receiving information on the valid transmission period between the initiator  40  and the responder  41  through system information or a beacon frame. 
     A new data frame may be transmitted every valid transmission time  440 , and a MAC buffer may be updated according to the valid transmission time  440 . For example, a first data frame currently buffered may be transmitted at a first valid transmission time, and when the first valid transmission time elapses, a second data frame may be buffered. Thereafter, the second data frame may be transmitted at the second valid transmission time. That is, each data frame is transmitted or retransmitted within the valid transmission time  440  given for the data frame, but after the valid transmission time  440  elapses, it is no longer valid from a perspective of operating the wireless AV system even if it is transmitted or retransmitted. 
     In  FIG. 4 , eventually, retransmission  450  of the forward data frame  410  by the initiator  40  occurs after transmitting a block ACK frame  440  for the reverse data frame  430 . However, at this time point, since a time-out of the valid transmission time  400  occurs, the initiator  40  drops or interrupts the retransmission  450  of the forward data frame  410 . In addition, the initiator  40  transmits a new forward data frame to the responder  41  at a next valid transmission time  441 . 
       FIG. 5  illustrates a communication procedure based on a reverse direction protocol in a wireless AV system according to another embodiment. The present embodiment provides a method capable of achieving transmission of a reverse data frame while enabling retransmission of a forward data frame within a valid transmission time even if transmission of the forward data frame fails, when an RDG is activated (RDG=1) in the wireless AV system supporting the reverse direction protocol. 
     In the embodiment of  FIG. 5 , if an initiator  50  is the wireless data transmission device  1100  and a responder  51  is the wireless data reception device  1200 , an operation of the initiator  50  may be an operation of the communication unit  1140 , and an operation of the responder  51  may be an operation of the communication unit  1210 . Alternatively, in the present embodiment, if the initiator  50  is the wireless data reception device  1200  and the responder  51  is the wireless data transmission device  1100 , the operation of the initiator  50  may be the operation of the communication unit  1210 , and the operation of the responder  51  may be the operation of the communication unit  1140 . 
     Referring to  FIG. 5 , the initiator  50  obtains a TXOP  500  and transmits a forward data frame  510  to the responder  51  within the TXOP  500 . The forward data frame  510  is prepared to be validly transmitted only within a value transmission time  540 . Herein, the forward data frame  510  may include an RDG field which permits or authorizes reverse transmission. 
     For example, the RDG field may be configured as shown in Table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Role of transmitting 
                   
               
               
                 Value 
                 side 
                 Interpretation of value 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0 
                 not RD responder 
                 no reverse grant 
               
               
                   
                 RD responder 
                 PPDU carrying corresponding frame is 
               
               
                   
                   
                 transmitted last by RD 
               
               
                 1 
                 RD initiator 
                 RDG is present 
               
               
                   
                 RD responder 
                 PPDU carrying corresponding frame is 
               
               
                   
                   
                 followed by another PPDU 
               
               
                   
               
            
           
         
       
     
     That is, when the RDG field value is set to 1 from a perspective of the initiator, it indicates that the RDG is present (i.e., reverse transmission is permitted or authorized). 
     The responder  51  receives the forward data frame  510  including a RDG field  512  (RDG=1) to permit or authorize reverse transmission. Further, the responder  51  generates a block ACK frame  520  indicating whether the forward data frame  510  is successfully received, and feeds back it to the initiator  50  after an SIFS. For example, as shown in  FIG. 5 , when at least part of the forward data frame  510  fails in transmission (see  511 ), the responder  51  feeds back the block ACK frame  520  in which NACK is set for the failed part to the initiator  50 . 
     Meanwhile, the responder  51  may be configured to buffer a reverse data frame to be transmitted to the initiator (not shown in the figure). In addition, the buffered reverse data frame may be transmitted within the TXOP  500  by the authorization of the initiator  50 . Herein, since at least part of the forward data frame  510  fails in transmission (see  511 ), when the responder  51  transmits the reverse data frame based on RDG= 1 , the forward data frame  510  may not be retransmitted within the valid transmission time  540 . Therefore, the responder  51  may control retransmission of the forward data frame  510  despite RDG=1 according to a specific criterion. 
     For example, the responder  51  may set a value of a more data field indicating whether the reverse data frame is present based on whether at least part of the forward data frame  510  fails in reception, and may transmit the more data field to the initiator  50 . 
     For example, when it is identified that at least part of the forward data frame  510  fails in reception, the responder  51  transmits to the initiator  50  the block ACK frame  520  in which NACK is set for the failed data. In addition, the responder  51  may decline the authorization despite RDG=1, and drop, suspend, or postpone the transmission of the buffered reverse data frame. In addition, the responder  51  may transmit the more data field to the initiator  50  by setting “absence of buffered reverse data frame or no more PPDU” (more PPDU=0). Herein, the more data field may be transmitted by being included in the block ACK frame  520 . 
     Upon receiving the more data field, the initiator  50  may perform retransmission  540  of the forward data frame  510  within the valid transmission time  540 , and the responder  51  may transmit to the initiator  50  a block ACK frame  550  for the retransmission  540 . Accordingly, delay occurring in retransmission of the forward data frame  510  can be reduced, and performance of the wireless AV system can be guaranteed. In addition, a new data frame  560  is transmitted by the responder  50  during a next valid transmission time  541 . 
     As another example, the responder  51  may set a value of a more data field indicating whether the reverse data frame is present, based on whether at least part of the forward data frame  510  fails in reception and priorities of the forward data frame  510  and the buffered revered data frame, and may transmit the more data field to the initiator  50 . 
     For example, when it is identified that at least part of the forward data frame  510  fails in reception, the block ACK frame  520  in which NACK is set for the failed data is generated. 
     In this case, the responder  51  identifies the priorities of the forward data frame  510  and the buffered reverse data frame. 
     If the forward data frame  510  has a higher priority than the buffered reverse data frame, the responder  51  may decline the authorization despite RDG= 1 , and may transmit the more data field to the initiator  50  by setting “absence of buffered reverse data frame or no more PPDU” (more PPDU=0). In addition, the responder  51  may drop, suspend, or postpone the transmission of the buffered reverse data frame. Herein, the more data field may be transmitted by being included in the block ACK frame  520 . Upon receiving the more data field, the initiator  50  may perform retransmission  540  of the forward data frame  510  within the valid transmission time  540 , and the responder  51  may transmit to the initiator  50  the block ACK frame  550  for the retransmission  540 . 
     Otherwise, if the reverse data frame has a higher priority than the forward data frame  510 , the responder  51  may use a right granted for transmission of the reverse data frame to transmit the more data field to the initiator  50  by setting “presence of buffered reverse data frame or more PPDU” (more PPDU=1). In this case, the more data field may be transmitted by being included in the block ACK frame  520 . Thereafter, the responder  51  may transmit the reverse data frame to the initiator  50  within the TXOP  500 . In this case, as shown in  FIG. 4 , the initiator  50  does not perform retransmission of the forward data frame, and performs transmission of the new data frame  560  when the next valid transmission time  541  arrives. 
       FIG. 6  and  FIG. 7  illustrate a communication procedure based on a reverse direction protocol in a wireless AV system according to another embodiment. The present embodiment provides a method enabling retransmission of a reverse data frame within a valid transmission time if transmission of the forward data frame succeeds, when an RDG is activated (RDG=1) in the wireless AV system supporting the reverse direction protocol. 
     In the embodiment of  FIG. 6  and  FIG. 7 , if an initiator  60  is the wireless data transmission device  1100  and a responder  61  is the wireless data reception device  1200 , an operation of the initiator  60  may be an operation of the communication unit  1140 , and an operation of the responder  61  may be an operation of the communication unit  1210 . Alternatively, in the present embodiment, if the initiator  60  is the wireless data reception device  1200  and the responder  61  is the wireless data transmission device  1100 , the operation of the initiator  60  may be the operation of the communication unit  1210 , and the operation of the responder  61  may be the operation of the communication unit  1140 . 
     Referring to  FIG. 6 , the initiator  60  obtains a TXOP  600 , and transmits a forward data frame  610  to the responder  61  within the TXOP  600 . The forward data frame  610  is prepared to be validly transmitted only within a valid transmission time  640 . Herein, the forward data frame  610  may include an RDG field  611  which permits or authorizes reverse transmission. For example, the RDG field may be configured as shown in Table 1 above. 
     The responder  61  receives the forward data frame  610  including the RDG field  611  (RDG=1) to permit or authorize reverse transmission. Further, the responder  61  generates a block ACK frame  620  indicating whether the forward data frame  610  is successfully received, and feeds back it to the initiator  60  after an SIFS. For example, as shown in  FIG. 6 , when the forward data frame  610  succeeds in transmission, the responder  61  feeds back the block ACK frame  620  in which ACK is set for the entirety of the forward data frame  610  to the initiator  60 . 
     Meanwhile, the responder  61  may be configured to buffer a reverse data frame  630  to be transmitted to the initiator. In addition, the buffered reverse data frame  630  may be transmitted to the initiator  60  within the TXOP  600  by the authorization of the initiator  60 . Herein, since the forward data frame  610  succeeds in transmission, the responder  61  may transmit the reverse data frame  630  within the given valid transmission time  640 , based on RDG=1. 
     However, the reverse data frame  630  may be transmitted by exceeding the remaining valid transmission time  640  according to a size of the reverse data frame  630  (see  631 ). This is because the remaining TXOP  600  can be used without limitation due to the right of the responder  61 . In this case, there is a problem in that a collision occurs with transmission of a new forward data frame  650  of the originally scheduled initiator  60  due to transmission of the reverse data frame  630 . 
     As such, when it is determined that the reverse data frame is transmitted by exceeding the remaining valid transmission time  640  (see  631 ), as shown in  FIG. 7 , the responder  61  may transmit a first part  630 - 1  of the reverse data frame  630  within a first valid transmission time  640 , and may delay a transmitting timing of the remaining second part  630 - 2  of the reverse data frame  630  to a next second valid transmission time  641 . To this end, a data transmission duration can be controlled by negotiating occupancy of the TXOP  600  between the initiator  60  and the responder  61 . Accordingly, the initiator  60  may periodically transmit a new forward data frame  670  to the responder  61  without a collision for the next valid transmission time  641  during a single TXOP. 
     Since the device and method for receiving wireless data or the device and method for transmitting wireless data according to the above-described embodiments of the present disclosure do not mandatorily require all of the components or operations that are described above, the device and method for receiving wireless data or the device and method for transmitting wireless data may be performed by including all or part of the above-described components or operations. Additionally, the above-described embodiments of the device and method for receiving wireless data or the device and method for transmitting wireless data may be performed in combination with each other. Furthermore, the above-described components or operations are not mandatorily required to be performed in the order that is described above, and, therefore, it is also possible for components or operations (or process steps) that are described in a later order to be performed before the components or operations (or process steps) that are described in an earlier order. 
     The foregoing description has been presented merely to provide an exemplary description of the technical idea of the present disclosure, and it will be apparent to those skilled in the art to which the present disclosure pertains, that various changes and modifications in the embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Therefore, the embodiments of the present disclosure described above can be implemented separately or in combination with each other. 
     The embodiments disclosed herein are provided not to limit the technical idea of the present disclosure but to describe the present disclosure, and the scope of the technical idea of the present disclosure should not be limited to these embodiments. The scope of the present disclosure should be interpreted by the following claims, and all technical ideas within the scope of equivalents thereto should be construed as being included in the scope of the present disclosure.