Patent Description:
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) <NUM>. 11ad standard is a high-speed wireless communication standard operating in a band of <NUM> or higher. It has signal coverage of about <NUM> meters but can support throughput of <NUM> 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 <NUM>. 11ay standard, an evolved version of IEEE <NUM>. 11ad, is under development.

An existing standard such as IEEE <NUM>. 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 <NUM>:<NUM> 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. <CIT> relates to a method and apparatus for delayed block acknowledgements in a wireless local area network (WLAN).

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:.

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.

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. The characteristics and features of the present disclosure are described with reference to exemplary embodiments presented herein. Throughout the present specification, similar reference numerals will be used to refer to similar components or features.

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> is a block diagram of a wireless AV system according to an embodiment of the present disclosure.

Referring to <FIG>, a wireless AV system <NUM> may include a main device <NUM>, a display panel device <NUM>, and a remote control device <NUM>.

The main device <NUM> 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 <NUM>.

In order to perform such operation, the main device <NUM> may include an external signal receiver <NUM>, an external device interface unit <NUM>, a storage unit <NUM>, a main controller <NUM>, a wireless communication unit <NUM>, and a power supply unit <NUM>.

The external signal receiver <NUM> may include a tuner <NUM>, a demodulator <NUM>, and a network interface unit <NUM>.

The tuner <NUM> 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 <NUM> 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 <NUM> 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 <NUM> 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 <NUM> 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 <NUM> or storage unit <NUM>.

The external device interface unit <NUM> may provide a connection path between the wireless AV system <NUM> and an external device. The external device interface unit <NUM> 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 <NUM> via wired or wireless connection, and may then deliver the received external input signal to the main controller <NUM>. The external device interface unit <NUM> 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 <NUM> 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 <NUM> may provide an interface for connecting the main device <NUM> to a wired/wireless network including an internet network. The network interface unit <NUM> 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 <NUM> 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 <NUM>.

The network interface unit <NUM> 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 <NUM> may transmit or receive data to or from a corresponding server by accessing a predetermined webpage through the network.

Also, the network interface unit <NUM> may receive contents or data provided from a content provider or a network operator. That is, the network interface unit <NUM> 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 <NUM> 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 <NUM> may select and receive a wanted application among applications that are open to public, through the network.

The storage unit <NUM> may store programs for performing processing and control of each signal within the main controller <NUM>, and then the storage unit <NUM> may store signal-processed image, voice, or data signals.

Additionally, the storage unit <NUM> may perform a function for temporarily storing image, voice, or data signals that are inputted from the external device interface unit <NUM> or network interface unit <NUM>, and the storage unit <NUM> may also store information related to a predetermined image through a channel memory function.

The storage unit <NUM> may store an application or an application list that is inputted from the external device interface unit <NUM> or network interface unit <NUM>.

The main controller <NUM> may control the main device <NUM> by using a user instruction (or command) that is inputted through the remote control device <NUM>, 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 <NUM>.

The main controller <NUM> enables user-selected channel information to be outputted along with a processed image or audio signal through a display device <NUM> or an audio output unit <NUM>.

Additionally, the main controller <NUM> 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 <NUM>, to be outputted through the display device <NUM> or audio output unit <NUM> in accordance with according to an external device image playback instruction (or command) that is received through the remote control device <NUM>.

The main controller <NUM> may perform a control operation so that content stored in the storage unit <NUM>, 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 <NUM> may decode a video, an image, a picture, a sound, or data related to a broadcast program being inputted through the demodulator <NUM>, the external device interface unit <NUM>, or the storage unit <NUM>. Then, the main controller <NUM> may process the decoded data in accordance with encoding/decoding methods supported by the display device <NUM>. Thereafter, the main controller <NUM> 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 <NUM> may transmit the generated data stream or bitstream to the display device <NUM> through the wireless communication unit <NUM>. Depending upon the embodiments, the main controller <NUM> may also bypass the decoded data, without encoding the decoded data in accordance with the encoding/decoding methods supported by the display device <NUM>, and may directly transmit the decoded data to the display device <NUM> through the wireless communication unit <NUM>.

The main controller <NUM> may be configured to implement the functions, procedures, and/or methods of a processor <NUM> of a wireless data transmitting device <NUM> 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 <NUM>. The main controller <NUM> may be provided in the form of a system on chip (SoC).

The wireless communication unit <NUM> may be operatively coupled to the main controller <NUM>, for example, as a combination of a wireless communication chip and an RF antenna. The wireless communication unit <NUM> may receive a data stream or bitstream from the main controller <NUM>, 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 <NUM>. The wireless communication unit <NUM> establishes a wireless link, and the main device <NUM> and the display device <NUM> are connected through the wireless link. The wireless communication unit <NUM> 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., <NUM>, <NUM>, and <NUM> cellular networks). For example, the wireless communication unit <NUM> may perform communication by using a communication protocol, such as a standard of the IEEE <NUM> series.

The power supply unit <NUM> supplies power to the external signal receiver <NUM>, the external device interface unit <NUM>, the storage unit <NUM>, the main controller <NUM>, and the wireless communication unit <NUM>. Methods for receiving power from an external source performed by the power supply unit <NUM> may include a terminal method and a wireless method. In case the power supply unit <NUM> receives power by using a wireless method, the power supply unit <NUM> may include a separate configuration in order to wirelessly receive power. For example, the power supply unit <NUM> 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 <NUM> may also be wirelessly connected to the remote control device <NUM>, thereby being capable of transferring (or delivering) signals inputted by the user to the main controller <NUM> or transmitter (or delivering) signals from the main controller <NUM> to the user. For example, the wireless communication unit <NUM> may receive or process control signals, such as power on/off, screen settings, and so on, of the main device <NUM> from the remote control device <NUM> or may process control signals received from the main controller <NUM> so that the processed signals can be transmitted to the remote control device <NUM> 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 <NUM> 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 <NUM>.

Subsequently, the display device <NUM> may process a wireless stream, which is received from the main device <NUM> through a wireless interface, by performing a reverse process of a signal processing operation that is performed by the main device <NUM>, and, then, the display device <NUM> may output a display or audio (or sound). In order to perform such operation, the display device <NUM> may include a wireless communication unit <NUM>, a user input interface unit <NUM>, a panel controller <NUM>, a display unit <NUM>, an audio output unit <NUM>, and a power supply unit <NUM>.

The wireless communication unit <NUM> may be configured as a combination of a wireless communication chip and an RF antenna. The wireless communication unit <NUM> is connected to the wireless communication unit <NUM> of the main device <NUM> through a wireless link and performs wireless communication with the wireless communication unit <NUM> of the main device <NUM>. More specifically, the wireless communication unit <NUM> receives a wireless stream from the wireless communication unit <NUM> of the main device <NUM>, demodulates the received wireless stream, and transmits the demodulated wireless stream to the panel controller <NUM>. The wireless communication unit <NUM> 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., <NUM>, <NUM>, and <NUM> cellular networks). For example, the wireless communication unit <NUM> may perform communication by using a communication protocol, such as a standard of the IEEE <NUM> series.

The panel controller <NUM> decodes a signal that is demodulated by the wireless communication unit <NUM> 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 <NUM> may decompress or reconstruct the bitstream or data stream. Thereafter, the panel controller <NUM> 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 <NUM>, the audio output unit <NUM>, and the user input interface unit <NUM>.

The video signal, the picture signal, the image signal, and so on, that are inputted to the display unit <NUM> may be displayed as a picture corresponding to the inputted picture signal. Alternatively, the picture signal that is processed by the panel controller <NUM> may be transmitted back to the main device <NUM> through the wireless communication unit <NUM> and may then be inputted to an external output device through the external device interface unit <NUM> of the main device <NUM>.

The audio signal that is processed by the panel controller <NUM> may be audio-outputted to the audio output unit <NUM>. Moreover, the audio signal that is processed by the panel controller <NUM> may be transmitted back to the main device <NUM> through the wireless communication unit <NUM> and may then be inputted to an external output device through the external device interface unit <NUM> of the main device <NUM>.

Meanwhile, the panel controller <NUM> may control the display unit <NUM> so as to display a picture (or image). For example, the panel controller <NUM> may perform control operation, so that a broadcast picture (or image) that is inputted through the tuner <NUM>, an externally inputted picture (or image) that is inputted through the external device interface unit <NUM>, a picture (or image) that is inputted through the network interface unit, or a picture (or image) that is stored in the storage unit <NUM> can be displayed on the display unit <NUM>. In this case, the picture (or image) that is displayed on the display unit <NUM> may be a still picture (or image) or a video, and may be a 2D image or a 3D image.

The panel controller <NUM> may be configured to implement the functions, procedures, and/or methods of a processor <NUM> included in a wireless data receiving device <NUM>, which will be described with reference to each embodiment of the present specification. Additionally, the processor <NUM> may be configured to implement the functions, procedures, and/or methods of the wireless data receiving <NUM> that will be described with reference to each embodiment of the present specification.

The user input interface unit <NUM> may transmit a signal that is inputted, by the user, to the panel controller <NUM> or may transmit a signal from the panel controller <NUM> to the user. For example, the user input interface <NUM> may receive and process control signals, such as power on/off, screen settings, and so on, of the display device <NUM> from the remote control device <NUM>, or may process control signals received from the panel controller <NUM> so that the processed signals can be transmitted to the remote control device <NUM> 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 <NUM> 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 <NUM>.

The power supply unit <NUM> supplies power to the wireless communication unit <NUM>, the user input interface unit <NUM>, the panel controller <NUM>, the display unit <NUM>, and the audio output unit <NUM>. Methods for receiving power from an external source performed by the power supply unit <NUM> may include a terminal method and a wireless method. In case the power supply unit <NUM> receives power by using a wireless method, the power supply unit <NUM> may include a separate configuration in order to wirelessly receive power. For example, the power supply unit <NUM> 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 <NUM> performs an operation of remotely controlling various features of the main device <NUM> or the display device <NUM>, such as power on/off, channel selection, screen setup, and so on. Herein, the remote control device <NUM> may also be referred to as a "remote controller (or remote)".

Meanwhile, since the main device <NUM> and the display device <NUM>, which are shown in <FIG>, 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 <NUM> and the display device <NUM>, 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 of the present disclosure.

According to another embodiment of the present disclosure, unlike the example shown in <FIG>, the main device <NUM> may receive and play-back (or reproduce) an image (or picture) through the network interface unit <NUM> or the external device interface unit <NUM> without including the tuner <NUM> and the demodulator <NUM>.

For example, the main device <NUM> 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 <NUM> according to an embodiment of the present disclosure that will hereinafter be described may be performed not only by the main device <NUM> and the display device <NUM>, as described above with reference to <FIG>, 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 <NUM>.

In light of system input/output, the main device <NUM> may be referred to as a wireless source device that wirelessly provides a source, and the display device <NUM> 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 <NUM> 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 <NUM> may be provided as a wireless communication module or a chip. The display device <NUM> 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 <NUM> may be provided in the form of a wireless communication module or chip.

The main device <NUM> and the display device <NUM> may be integrated to forms that configure parts of a mobile device. For example, the main device <NUM> and the display device <NUM> 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 <NUM> and the display device <NUM> 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' 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 <NUM> 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 <NUM> 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 <NUM> 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 <NUM> may wirelessly communicate with the display device <NUM> and may transmit wireless data. Therefore, in light of a wireless data transceiving system <NUM>, the main device <NUM> may be referred to as a wireless data transmitting device <NUM>, and the display device <NUM> may be referred to as a wireless data receiving device <NUM>. Hereinafter, the present disclosure will be described in more detail in light of the wireless data transceiving system <NUM>. Firstly, a detailed block diagram of the wireless data transceiving system <NUM> will be illustrated.

<FIG> is a block diagram showing a wireless data transceiving system according to an embodiment of the present disclosure.

Referring to <FIG>, a wireless data transceiving system <NUM> refers to a system that wirelessly transmits and receives a data stream. And, the wireless data transceiving system <NUM> includes a wireless data transmitting <NUM> and at least one wireless data receiving device <NUM>. The wireless data transmitting device <NUM> is communicatively coupled to the at least one wireless data receiving device <NUM>.

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 <NUM> may also be referred to as a wireless compressed data stream transceiving system. Additionally, the wireless compressed data stream transceiving system <NUM> may further include a functional or physical unit for compressing data.

Referring to the detailed configuration of each device, the wireless data transmitting device <NUM> includes a processor <NUM>, a memory <NUM>, and a communication unit <NUM>, and the wireless data receiving device <NUM> includes a communication unit <NUM>, a memory <NUM>, and a processor <NUM>.

The processor <NUM> may be configured to implement the functions, procedures, and/or methods of the wireless data transmitting device <NUM> that are to be described with reference to each embodiment of the present specification. Also, the processor <NUM> may also be configured to implement the functions, procedures, and/or methods of the wireless data receiving device <NUM> 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 <NUM> and <NUM>.

In light of the display system in <FIG>, the processor <NUM> may be configured to perform the function of the main controller <NUM>. For example, the processor <NUM> may decode a video, an image, a picture, a sound, or data related to a broadcast program that are inputted through the demodulator <NUM>, the external device interface unit <NUM>, or the storage unit <NUM>, 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 <NUM> through the communication unit <NUM>.

The memories <NUM> and <NUM> are operatively coupled with the processors <NUM> and <NUM> and store various types of information for operating the processors <NUM> and <NUM>.

The communication units <NUM> and <NUM> are operatively coupled with the processors <NUM> and <NUM> and wirelessly transmit and/or receive data. The communication units <NUM> and <NUM> establish a wireless link <NUM>, and the wireless data transmitting device <NUM> and the wireless data receiving device <NUM> are inter-connected through the wireless link <NUM>. The communication units <NUM> and <NUM> 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., <NUM>, <NUM>, and <NUM> cellular networks). For example, the wireless communication units <NUM> and <NUM> may perform communication by using a communication protocol, such as a standard of the IEEE <NUM> series.

<FIG> 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 <NUM> series communication protocol.

Referring to <FIG>, a wireless data transceiving system <NUM> in (A) of <FIG> may include at least one basic service set (hereinafter referred to as `BSS') <NUM> and <NUM>. ABSS 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 <NUM> may include a first AP <NUM> and one first STA <NUM>-<NUM>. A second BSS <NUM> may include a second AP <NUM> and one or more STAs <NUM>-<NUM> and <NUM>-<NUM>. Herein, the first AP <NUM> may correspond to the communication unit <NUM> of <FIG>, and the one or more STAs <NUM>-<NUM> and <NUM>-<NUM> may correspond to the communication unit <NUM> of <FIG>.

An infrastructure BSS <NUM> and <NUM> may include at least one STA, APs <NUM> and <NUM> providing a distribution service, and a distribution system (DS) <NUM> connecting multiple APs.

The distribution system <NUM> may implement an extended service set (hereinafter referred to as `ESS') <NUM>, which is extended by being connected to multiple BSSs <NUM> and <NUM>. The ESS <NUM> may be used as a term indicating one network that is configured by connecting one or more APs <NUM> and <NUM> through the distribution system <NUM>. At least one AP being included in one ESS <NUM> may have a same service set identification (hereinafter referred to as 'SSID').

A portal <NUM> may perform the role of a bridge, which connects the wireless LAN network (IEEE <NUM>) with another network (e.g., <NUM>.

In a WLAN having the structure shown in (A) of <FIG>, a network between the APs <NUM> and <NUM> and a network between the APs <NUM> and <NUM> and the STAs <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be implemented.

Meanwhile, unlike the system shown in (A) of <FIG>, the wireless data transceiving system <NUM> shown in (B) of <FIG> may be capable of performing communication by establishing a network between the STAs without any APs <NUM> and <NUM>. A network that is capable of performing communication by establishing a network between the STAs without any APs <NUM> and <NUM> is defined as an Ad-Hoc network or an independent basic service set (hereinafter referred to as `IBSS').

Referring to (B) of <FIG>, the wireless data transceiving system <NUM> 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 <NUM>, STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are managed in a distributed manner. Here, the STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may correspond to the communication unit <NUM> or the communication unit <NUM> of <FIG>.

All STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> 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) <NUM> 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>, a communication channel that is established by the communication units <NUM> and <NUM> may be a network communication channel. In this case, the communication units <NUM> and <NUM> 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 <NUM> 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 <NUM>, <NUM>, <NUM>, <NUM>, 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 <NUM> 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 <NUM> and <NUM> 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 <NUM> and <NUM> may include an application-specific integrated circuit (ASIC), a different chipset, a logic circuit, and/or a data processor. The memories <NUM> and <NUM> 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 <NUM> and <NUM> 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 <NUM> and <NUM> and may be executed by the processors <NUM> and <NUM>. The memories <NUM> and <NUM> may be implemented inside the processors <NUM> and <NUM>. Alternatively, the memories <NUM> and <NUM> may be implemented outside of the processors <NUM> and <NUM>, and the memories <NUM> and <NUM> may be communicatively connected to the processors <NUM> and <NUM> 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 <NUM> may be referred to as an AP or a personal basic service set control point (PCP) station, and the wireless data receiving device <NUM> 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 <NUM> may be referred to as a wireless source device that wirelessly provides a source, and the wireless data receiving device <NUM> 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 <NUM> 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 <NUM> may be provided as a wireless communication module or a chip. And, the wireless data receiving device <NUM> 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 <NUM> may be provided in the form of a wireless communication module or chip.

The wireless data transmitting device <NUM> and the wireless data receiving device <NUM> may be integrated to forms that configure parts of a mobile device. For example, the wireless data transmitting device <NUM> and the wireless data receiving device <NUM> 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 <NUM> and the wireless data receiving device <NUM> may be provided in the form of wireless communication modules or chips.

<FIG> 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 <NUM> standard using a radio resource of a 60HGz band.

Referring to <FIG>, an initiator <NUM> obtains a transmission opportunity (TXOP) <NUM> and has a right to transmit data to a responder <NUM> within the TXOP. The responder <NUM> is a device which receives data from the initiator within the TXOP <NUM> obtained by the initiator <NUM>.

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 <NUM> to the responder <NUM> may be called a forward data frame <NUM> or a downlink data frame. From a perspective of a medium access control (MAC) layer, the forward data frame <NUM> 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 <NUM> may be a PHY protocol data unit (PPDU).

The responder <NUM> generates a block ACK frame <NUM> indicating whether the forward data frame <NUM> is successfully received and feeds back it to the initiator <NUM> after a short inter frame space (SIFS). For example, as shown in <FIG>, when at least part of the forward data frame <NUM> fails in transmission (see <NUM>), the responder <NUM> feeds back the block ACK <NUM> in which NACK is set for the failed part to the initiator <NUM>.

Meanwhile, the responder <NUM> may obtain a right to transmit data within the TXOP <NUM> according to a permission of the initiator <NUM>. As such, when the initiator <NUM> grants a data transmission right to the responder <NUM>, it is called a reverse direction grant (RDG) <NUM>. In addition, a data frame which is transmitted to the initiator <NUM> when the responder <NUM> receives the RDG <NUM> may be called a reverse data frame <NUM> or an uplink data frame. Therefore, the responder <NUM> for which a data transmission right is granted (RDG=<NUM>) by means of the RDG <NUM> transmits to the initiator <NUM> a more data field indicating that a buffered reverse data frame is present, and then transmits the buffered reverse data frame <NUM> to the initiator <NUM> 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 <NUM> may identify that a loss occurs in part of the forward data frame <NUM> from the block ACK frame <NUM> of the responder, and thus may prepare for retransmission of the forward data frame <NUM>. Since the data transmission right is granted to the responder <NUM>, the initiator <NUM> may identify that there is data to be transmitted by the responder <NUM> by means of the more data field. In this case, even if at least part of the forward data frame <NUM> fails in transmission, the initiator <NUM> receives the reverse data frame <NUM> transmitted by the responder <NUM>, instead of retransmitting the forward data frame <NUM>.

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 <NUM>. The valid transmission time <NUM> is preferably designed as a time in which each data frame (or buffered data frame) transmitted by the initiator <NUM> can be validly used by the responder <NUM>, and may be, for example, <NUM>. 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 <NUM> and the responder <NUM> through system information or a beacon frame.

A new data frame may be transmitted every valid transmission time <NUM>, and a MAC buffer may be updated according to the valid transmission time <NUM>. 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 <NUM> given for the data frame, but after the valid transmission time <NUM> elapses, it is no longer valid from a perspective of operating the wireless AV system even if it is transmitted or retransmitted.

In <FIG>, eventually, retransmission <NUM> of the forward data frame <NUM> by the initiator <NUM> occurs after transmitting a block ACK frame <NUM> for the reverse data frame <NUM>. However, at this time point, since a time-out of the valid transmission time <NUM> occurs, the initiator <NUM> drops or interrupts the retransmission <NUM> of the forward data frame <NUM>. In addition, the initiator <NUM> transmits a new forward data frame to the responder <NUM> at a next valid transmission time <NUM>.

<FIG> 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=<NUM>) in the wireless AV system supporting the reverse direction protocol.

In the embodiment of <FIG>, if an initiator <NUM> is the wireless data transmission device <NUM> and a responder <NUM> is the wireless data reception device <NUM>, an operation of the initiator <NUM> may be an operation of the communication unit <NUM>, and an operation of the responder <NUM> may be an operation of the communication unit <NUM>. Alternatively, in the present embodiment, if the initiator <NUM> is the wireless data reception device <NUM> and the responder <NUM> is the wireless data transmission device <NUM>, the operation of the initiator <NUM> may be the operation of the communication unit <NUM>, and the operation of the responder <NUM> may be the operation of the communication unit <NUM>.

Referring to <FIG>, the initiator <NUM> obtains a TXOP <NUM> and transmits a forward data frame <NUM> to the responder <NUM> within the TXOP <NUM>. The forward data frame <NUM> is prepared to be validly transmitted only within a value transmission time <NUM>. Herein, the forward data frame <NUM> may include an RDG field which permits or authorizes reverse transmission.

For example, the RDG field may be configured as shown in Table <NUM>.

That is, when the RDG field value is set to <NUM> from a perspective of the initiator, it indicates that the RDG is present (i.e., reverse transmission is permitted or authorized).

The responder <NUM> receives the forward data frame <NUM> including a RDG field <NUM> (RDG=<NUM>) to permit or authorize reverse transmission. Further, the responder <NUM> generates a block ACK frame <NUM> indicating whether the forward data frame <NUM> is successfully received, and feeds back it to the initiator <NUM> after an SIFS. For example, as shown in <FIG>, when at least part of the forward data frame <NUM> fails in transmission (see <NUM>), the responder <NUM> feeds back the block ACK frame <NUM> in which NACK is set for the failed part to the initiator <NUM>.

Meanwhile, the responder <NUM> 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 <NUM> by the authorization of the initiator <NUM>. Herein, since at least part of the forward data frame <NUM> fails in transmission (see <NUM>), when the responder <NUM> transmits the reverse data frame based on RDG=<NUM>, the forward data frame <NUM> may not be retransmitted within the valid transmission time <NUM>. Therefore, the responder <NUM> may control retransmission of the forward data frame <NUM> despite RDG=<NUM> according to a specific criterion.

For example, the responder <NUM> 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 <NUM> fails in reception, and may transmit the more data field to the initiator <NUM>.

For example, when it is identified that at least part of the forward data frame <NUM> fails in reception, the responder <NUM> transmits to the initiator <NUM> the block ACK frame <NUM> in which NACK is set for the failed data. In addition, the responder <NUM> may decline the authorization despite RDG=<NUM>, and drop, suspend, or postpone the transmission of the buffered reverse data frame. In addition, the responder <NUM> transmits the more data field to the initiator <NUM> by setting "absence of buffered reverse data frame or no more PPDU" (more PPDU=<NUM>). Herein, the more data field may be transmitted by being included in the block ACK frame <NUM>.

Upon receiving the more data field, the initiator <NUM> may perform retransmission <NUM> of the forward data frame <NUM> within the valid transmission time <NUM>, and the responder <NUM> may transmit to the initiator <NUM> a block ACK frame <NUM> for the retransmission <NUM>. Accordingly, delay occurring in retransmission of the forward data frame <NUM> can be reduced, and performance of the wireless AV system can be guaranteed. In addition, a new data frame <NUM> is transmitted by the responder <NUM> during a next valid transmission time <NUM>.

As another example, the responder <NUM> 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 <NUM> fails in reception and priorities of the forward data frame <NUM> and the buffered revered data frame, and may transmit the more data field to the initiator <NUM>.

For example, when it is identified that at least part of the forward data frame <NUM> fails in reception, the block ACK frame <NUM> in which NACK is set for the failed data is generated.

In this case, the responder <NUM> identifies the priorities of the forward data frame <NUM> and the buffered reverse data frame.

If the forward data frame <NUM> has a higher priority than the buffered reverse data frame, the responder <NUM> may decline the authorization despite RDG=<NUM>, and may transmit the more data field to the initiator <NUM> by setting "absence of buffered reverse data frame or no more PPDU" (more PPDU=<NUM>). In addition, the responder <NUM> 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 <NUM>. Upon receiving the more data field, the initiator <NUM> may perform retransmission <NUM> of the forward data frame <NUM> within the valid transmission time <NUM>, and the responder <NUM> may transmit to the initiator <NUM> the block ACK frame <NUM> for the retransmission <NUM>.

Otherwise, if the reverse data frame has a higher priority than the forward data frame <NUM>, the responder <NUM> uses a right granted for transmission of the reverse data frame to transmit the more data field to the initiator <NUM> by setting "presence of buffered reverse data frame or more PPDU" (more PPDU=<NUM>). In this case, the more data field may be transmitted by being included in the block ACK frame <NUM>. Thereafter, the responder <NUM> transmits the reverse data frame to the initiator <NUM> within the TXOP <NUM>. In this case, as shown in <FIG>, the initiator <NUM> does not perform retransmission of the forward data frame, and performs transmission of the new data frame <NUM> when the next valid transmission time <NUM> arrives.

<FIG> and <FIG> 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=<NUM>) in the wireless AV system supporting the reverse direction protocol.

In the embodiment of <FIG> and <FIG>, if an initiator <NUM> is the wireless data transmission device <NUM> and a responder <NUM> is the wireless data reception device <NUM>, an operation of the initiator <NUM> may be an operation of the communication unit <NUM>, and an operation of the responder <NUM> may be an operation of the communication unit <NUM>. Alternatively, in the present embodiment, if the initiator <NUM> is the wireless data reception device <NUM> and the responder <NUM> is the wireless data transmission device <NUM>, the operation of the initiator <NUM> may be the operation of the communication unit <NUM>, and the operation of the responder <NUM> may be the operation of the communication unit <NUM>.

Referring to <FIG>, the initiator <NUM> obtains a TXOP <NUM>, and transmits a forward data frame <NUM> to the responder <NUM> within the TXOP <NUM>. The forward data frame <NUM> is prepared to be validly transmitted only within a valid transmission time <NUM>. Herein, the forward data frame <NUM> may include an RDG field <NUM> which permits or authorizes reverse transmission. For example, the RDG field may be configured as shown in Table <NUM> above.

The responder <NUM> receives the forward data frame <NUM> including the RDG field <NUM> (RDG=<NUM>) to permit or authorize reverse transmission. Further, the responder <NUM> generates a block ACK frame <NUM> indicating whether the forward data frame <NUM> is successfully received, and feeds back it to the initiator <NUM> after an SIFS. For example, as shown in <FIG>, when the forward data frame <NUM> succeeds in transmission, the responder <NUM> feeds back the block ACK frame <NUM> in which ACK is set for the entirety of the forward data frame <NUM> to the initiator <NUM>.

Meanwhile, the responder <NUM> may be configured to buffer a reverse data frame <NUM> to be transmitted to the initiator. In addition, the buffered reverse data frame <NUM> may be transmitted to the initiator <NUM> within the TXOP <NUM> by the authorization of the initiator <NUM>. Herein, since the forward data frame <NUM> succeeds in transmission, the responder <NUM> may transmit the reverse data frame <NUM> within the given valid transmission time <NUM>, based on RDG=<NUM>.

However, the reverse data frame <NUM> may be transmitted by exceeding the remaining valid transmission time <NUM> according to a size of the reverse data frame <NUM> (see <NUM>). This is because the remaining TXOP <NUM> can be used without limitation due to the right of the responder <NUM>. In this case, there is a problem in that a collision occurs with transmission of a new forward data frame <NUM> of the originally scheduled initiator <NUM> due to transmission of the reverse data frame <NUM>.

As such, when it is determined that the reverse data frame is transmitted by exceeding the remaining valid transmission time <NUM> (see <NUM>), as shown in <FIG>, the responder <NUM> may transmit a first part <NUM>-<NUM> of the reverse data frame <NUM> within a first valid transmission time <NUM>, and may delay a transmitting timing of the remaining second part <NUM>-<NUM> of the reverse data frame <NUM> to a next second valid transmission time <NUM>. To this end, a data transmission duration can be controlled by negotiating occupancy of the TXOP <NUM> between the initiator <NUM> and the responder <NUM>. Accordingly, the initiator <NUM> may periodically transmit a new forward data frame <NUM> to the responder <NUM> without a collision for the next valid transmission time <NUM> during a single TXOP.

Claim 1:
An apparatus for performing data transmission and reception in a wireless audio video, AV, system, the apparatus comprising:
a communication unit configured to receive from an initiator (<NUM>) a forward data frame (<NUM>) and reverse direction grant, RDG, information (<NUM>) indicating permission of reverse transmission within a transmission opportunity, TXOP, (<NUM>) obtained by the initiator (<NUM>), generate a block ACK frame for the forward data frame (<NUM>) to transmit the block ACK frame to the initiator (<NUM>), and buffer a reverse data frame to be transmitted to the initiator (<NUM>); and
a processor coupled to the communication unit and configured to obtain AV data from the forward data frame (<NUM>),
wherein the communication unit sets a value of a data field indicating whether the reverse data frame is additionally transmitted, based on whether at least part of the forward data frame (<NUM>) fails in reception and priorities of the forward data frame (<NUM>) and the reverse data frame, and transmits the data field to the initiator (<NUM>),
wherein, if the communication unit fails in reception of at least part of the forward data frame (<NUM>), and the reverse data frame has a higher priority than the forward data frame (<NUM>), the communication unit sets the value of the data field to indicate that the reverse data frame is additionally transmitted, and then transmits the reverse data frame to the initiator within the TXOP (<NUM>),
wherein the value of the data field is set to <NUM> if the reverse data frame is additionally transmitted, and
wherein the value of the data field is set to <NUM> if the reverse data frame is not additionally transmitted.