UPLINK SOUNDING FOR WLAN SYSTEM
In wireless communications, an access point may transmit a first frame to one or more stations. In response to the first frame, the station(s) may transmit a respective second frame to the access point. The access point may generate a beamforming report based on the second frame(s) received by the access point from the station(s). The access point may transmit a third frame(s) that includes the beamforming report to the station(s). The station(s) may generate a respective beamforming matrix based at least on the third frame(s). Other methods, apparatus, and computer-readable media are also disclosed.
1 . A access point operating in a wireless network, the access point comprising:
one or more memories; and
a processor coupled to the one or more memories, wherein the one or more memories include instructions, which when executed by the processor, cause the access point to:
transmit a null data packet announcement frame to a first station and a second station in the wireless network, wherein the null data packet announcement frame causes the first station to transmit a first null data packet frame to the access point,
receive the first null data packet frame from the first station an interframe space period following the null data packet announcement frame,
generate first beamforming information based on the first null data packet frame that describes a wireless channel between the first station and the access point in which the first null data packet frame was transmitted,
transmit the first beamforming information to the first station, wherein the first station is to utilize the first beamforming information for performing beamforming operations with the access point, and
transmit a poll frame to the second station in the wireless network following receipt of the first beamforming information from the first station, wherein the poll frame causes the second station to transmit a second null data packet frame to the access point.
2 . The access point of claim 1 , wherein the one or more memories include further instructions, which when executed by the processor, further cause the access point to:
receive the second null data packet frame from the second station an interframe space period following the poll frame;
generate second beamforming information based on the second null data packet frame that describes a wireless channel between the second station and the access point in which the second null data packet frame was transmitted; and
transmit the second beamforming information to the second station, wherein the second station is to utilize the second beamforming information for performing beamforming operations with the access point.
3 . The access point of claim 1 , wherein the null data packet announcement frame includes a set of bits that indicate a type of the null data packet announcement frame.
4 . The access point of claim 3 , wherein the set of bits indicate whether the null data packet announcement frame is a very high throughput null data packet announcement frame or a high efficiency null data packet announcement frame.
5 . The access point of claim 3 , wherein the set of bits are located in a sounding dialog token of the null data packet announcement frame.
6 . The access point of claim 5 , wherein the set of bits are a first set of bits in the sounding dialog token of the null data packet announcement frame.
7 . The access point of claim 1 , wherein the one or more memories include further instructions, which when executed by the processor, further cause the access point to:
receive an uplink frame from the first station that triggers the access point to transmit the null data packet announcement frame to perform sounding.
8 . The access point of claim 7 , wherein the uplink frame includes a set of preferred subbands for performing sounding, wherein the one or more memories include further instructions, which when executed by the processor, further cause the access point to:
generate the null data packet announcement frame based on the set of preferred subbands.
9 . The access point of claim 1 , wherein the null data packet announcement frame indicates a number of long-training symbols to include in the first null data packet frame and the second null data packet frame.
10 . The access point of claim 9 , wherein the number of long-training symbols is equal for both the first null data packet frame and the second null data packet frame and is set to the ma
11 . A first station operating in a wireless network, the first station comprising:
one or more memories; and
a processor coupled to the one or more memories, wherein the one or more memories include instructions, which when executed by the processor, cause the first station to:
receive a trigger frame from an access point that triggers a sounding sequence from a set of stations in the wireless network, including the first station and a second station,
transmit a first null data packet frame to the access point as part of a first multi-user uplink transmission, wherein the first multi-user uplink transmission involves the first station and the second station and wherein the second station is to transmit a second null data packet frame in the first multi-user uplink transmission, and
receive a multi-user downlink transmission from the access point based on the first multi-user uplink transmission.
12 . The first station of claim 11 , wherein the multi-user downlink transmission includes first beamforming information describing a channel between the first station and the access point and second beamforming information describing a channel between the second station and the access point.
13 . The first station of claim 12 , wherein the one or more memories include further instructions, which when executed by the processor, cause the first station to:
transmit data to the access point as part of a second multi-user uplink transmission, wherein the second multi-user uplink transmission is a beamformed transmission that is configured according to the first beamforming information.
14 . The first station of claim 12 , wherein the trigger frame indicates a number of long-training symbols to include in the first null data packet frame and the second null data packet frame.
15 . The first station of claim 14 , wherein a long-training sequence is used for the long training symbols and is spread across tones of the long training symbols, including pilot tones; and
wherein the first beamforming information is generated based on the long training symbols and indicates which tones of the long training symbols were used for generating the first beamforming information.
16 . The first station of claim 11 , wherein the multi-user downlink transmission is a beamformed transmission that is configured according to beamforming information generated by the access point using the first null data packet frame and the second null data packet frame.
17 . The first station of claim 11 , wherein the trigger frame includes an indication that the first station is to transmit a null data packet frame to the access point.
18 . The first station of claim 17 , wherein the trigger frame indicates a length of the first multi-user uplink transmission and the length of the first multi-user uplink transmission is set to indicate that the first station is to transmit a null data packet frame to the access point.
19 . The first station of claim 11 , wherein the trigger frame includes first station specific information that indicates information for the first station to perform sounding and second station specific information that indicates information for the second station to perform sounding; and
wherein the trigger frame includes common information that includes information that indicates information for both the first station and the second station to perform sounding.
20 . The first station of claim 19 , wherein the first station specific information includes an identifier of the first station and indicates a number of spatial streams for the first station in the first multi-user uplink transmission;
wherein the second station specific information includes an identifier of the second station and indicates a number of spatial streams for the second station in the first multi-user uplink transmission; and
wherein the common information includes frequency allocation information for the first station and the second station in the first multi-user uplink transmission.