Method and apparatus for transmitting frame on basis of sounding procedure
A method and apparatus for transmitting a frame on the basis of a sounding procedure is disclosed. The method for transmitting the frame on the basis of a sounding procedure in a wireless LAN may comprise the steps of: transmitting an NDPA frame to each of multiple STAs by an AP wherein the NDPA frame notifies of the transmission of NDP; transmitting the NDP to each of the multiple STAs by the AP; receiving, by the AP, multiple feedback frames transmitted through multiple transmission sources allocated to the multiple STAs in time sources overlapped by the multiple STAs, respectively; and transmitting, by the AP, multiple downlink frames to the multiple STAs respectively.
1. A method of transmitting a frame based on a sounding procedure in a wireless local area network (WLAN), the method comprising:
generating, by a transmitting station, a null data packet announcement (NDPA) frame initiating the sounding procedure,
wherein the NDPA frame includes:
a feedback type field indicating a single user feedback mode or a multi user feedback mode, and
a feedback index field indicating a number of columns to be used for a beamforming feedback matrix;
transmitting, by the transmitting station, the NDPA frame;
transmitting, by the transmitting station, a null data packet (NDP) frame following the NDPA frame;
receiving, by the transmitting station, first feedback frames from first reporting stations,
wherein the first feedback frames are received based on an uplink multi-user operation, which enables the first feedback frames to be received by the transmitting station simultaneously, and
wherein each of the first feedback frames indicates a corresponding beamforming feedback matrix configured based on the feedback index field and a signal to noise ratio (SNR) for a corresponding wireless channel;
after receiving the first feedback frames, delaying, by the transmitting station, during a short inter-frame space (SIFS), and transmitting, by the transmitting station, a polling frame to second reporting stations immediately after the SIFS; and
receiving, by the transmitting station, second feedback frames from the second reporting stations,
wherein the second feedback frames are received based on the uplink multi-user operation, which enables the second feedback frames to be received by the transmitting station simultaneously, and
wherein each of the second feedback frames indicates a corresponding beamforming feedback matrix configured based on the feedback index field and a signal to noise ratio (SNR) for a corresponding wireless channel.
2. The method of claim 1 , wherein frequency resources for the first feedback frames are separately allocated by the transmitting station.
3. The method of claim 1 , wherein the polling frame indicates frequency resources allocated for the second feedback frames and identifiers of the second reporting stations.
4. The method of claim 1 , wherein the NDP frame comprises a first physical layer protocol data unit (PPDU) part including a legacy training field and a legacy signal field and a second PPDU part including a high efficiency short training field (HE-STF) and a high efficiency long training field (HE-LTF) and does not comprise a protocol service data unit (PSDU) field, wherein the first PPDU part is configured by a first point fast Fourier transform (FFT) operation and the second PPDU part is configured by a second point FFT operation such that a subcarrier spacing of the second PPDU part is four times fewer than a subcarrier spacing of the first PPDU part.
5. A transmitting station for transmitting a frame based on a sounding procedure in a wireless local area network (WLAN), the transmitting station comprising:
a radio frequency (RF) unit implemented to transmit or receive a radio signal; and
a processor operatively coupled to the RF unit,
wherein the processor is configured to:
generate a null data packet announcement (NDPA) frame initiating the sounding procedure,
wherein the NDPA frame includes:
a feedback type field indicating a single user feedback mode or a multi user feedback mode, and
a feedback index field indicating a number of columns to be used for a beamforming feedback matrix;
transmit the NDPA frame;
transmit a null data packet (NDP) frame following the NDPA frame;
receive first feedback frames from first reporting stations,
wherein the first feedback frames are received based on an uplink multi-user operation, which enables the first feedback frames to be received by the transmitting station simultaneously, and
wherein each of the first feedback frames indicates a corresponding beamforming feedback matrix configured based on the feedback index field and a signal to noise ratio (SNR) for a corresponding wireless channel;
after receiving the first feedback frames, delay during a short inter-frame space (SIFS), and transmit a polling frame to second reporting stations immediately after the SIFS; and
receive second feedback frames from the second reporting stations,
wherein the second feedback frames are received based on the uplink multi-user operation, which enables the second feedback frames to be received by the transmitting station simultaneously, and
wherein each of the second feedback frames indicates a corresponding beamforming feedback matrix configured based on the feedback index field and a signal to noise ratio (SNR) for a corresponding wireless channel.
6. The transmitting station of claim 5 , wherein frequency resources for the first feedback frames are separately allocated by the transmitting station.
7. The transmitting station of claim 5 , wherein the polling frame indicates frequency resources allocated for the second feedback frames and identifiers of the second reporting stations.
8. The transmitting station of claim 5 , wherein the NDP frame comprises a first physical layer protocol data unit (PPDU) part including a legacy training field and a legacy signal field and a second PPDU part including a high efficiency short training field (HE-STF) and a high efficiency long training field (HE-LTF) and does not comprise a protocol service data unit (PSDU) field, wherein the first PPDU part is configured by a first point fast Fourier transform (FFT) operation and the second PPDU part is configured by a second point FFT operation such that a subcarrier spacing of the second PPDU part is four times fewer than a subcarrier spacing of the first PPDU part.