NDPA for multi-AP coordinated beamforming (CBF) and multi-AP joint transmission (JT) in EHT

1. An apparatus of an access point (AP) configured for multi-AP coordinated beamforming (CBF) and multi-AP joint transmission (JT) in an Extremely High Throughput (EHT) wireless local area network (WLAN), the apparatus comprising: processing circuitry and memory,

wherein when the AP is operating as a master AP (AP1) in a multi-AP network, the processing circuitry is configured to:

encode a null data packet announcement (NDPA) frame for multi-AP channel sounding, the NDPA for transmission to a second AP (AP2) and a plurality of stations (STAs) of an EHT group, the NDPA encoded to have an information field indicating whether a sounding sequence type is for JT channel sounding or CBF channel sounding, the NDPA further encoded to include fields identifying APs participating in the channel sounding including the AP1 and the AP2;

encode a first null data packet (NDP1) for transmission to the STAs of the EHT group, the NDP1 to be transmitted concurrently with a second null data packet (NDP2) from the AP2, the NDP1 and the NPD2 comprising sounding sequences for either the JT channel sounding or the CBF channel sounding, the NDP1 and the NPD2 transmitted via a plurality of spatial streams; and

decode a channel state information (CSI) report frame receive from each STA of the EHT group, wherein each CSI report frame includes channel state information determined by one of the STAs of the EHT group based on both the NDP1 and the NDP2,

wherein for the CBF channel sounding, the CSI reports are determined by the STAs separately for the NDP1 and the NDP2, and

wherein for the JT channel sounding, the CSI reports are determined by the STAs from a combined reception of the NDP1 and the NDP2.

2. The apparatus of claim 1 , wherein the NDPA frame is further encoded to indicate whether the AP1 will transmit a beam-forming refinement phase (BFRP) trigger frame solicit the CSI report from each of the STAs, and

wherein when the NDPA is encoded to indicate that the AP1 will transmit the BFRP trigger frame, the processing circuitry is further configured to:

encode the BFRP trigger frame for transmission a short inter-frame spacing (SIFS) after the NDP1 to the STAs of the EHT group to solicit the CSI report from each of the STAs.

3. The apparatus of claim 2 , wherein for the CBF channel sounding, the processing circuitry is further configured to determine beamforming vectors based on the CSI reports.

4. The apparatus of claim 3 , wherein the fields identifying APs participating in the channel sounding comprise AP information fields, and wherein the AP information fields further include a number of spatial streams to be transmitted by each of the APs participating in the channel sounding.

5. The apparatus of claim 4 , wherein the AP information fields further include a mapping between the spatial streams and a P-matrix, for use by the STAs is performing a singular value decomposition (SVD) on a channel matrix obtained from the NDP1 and the NDP2, and

wherein the P-matrix is a complex square matrix having positive principal minors.

6. The apparatus of claim 5 , wherein the AP information fields further indicate whether each AP will transmit the BFRP trigger frame to solicit CSI reports from the STAs or whether an AP is able to receive a CSI report from another AP over a backhaul.

7. The apparatus of claim 1 , wherein the information field indicating whether the sounding sequence type is for the JT channel sounding or the CBF channel sounding is a common information field.

8. The apparatus of claim 1 , wherein the NDPA frame is further encoded to include a STA information fields for each of the STAs of the EHT group, wherein each STA information field is encoded to include an indicator indicating whether the sounding sequence type, for an associated STA of the EHT group, is for the JT channel sounding or the CBF channel sounding.

9. The apparatus of claim 1 , wherein the NDPA frame is a trigger frame having a trigger type subfield indicating multi-AP channel sounding, the trigger frame to trigger transmission of an NDPA by both the AP1 and AP2.

10. The apparatus of claim 1 , wherein the AP1 further comprising a plurality of antennas configured for transmitting the plurality of spatial streams of the NDP1, and

wherein the memory is configured to store the NDP1.

11. A non-transitory computer-readable storage medium that stores instructions for execution by processing circuitry of an access point (AP) configured for multi-AP coordinated beamforming (CBF) and multi-AP joint transmission (JT) in an Extremely High Throughput (EHT) wireless local area network (WLAN), wherein when the AP is operating as a master AP (AP1) in a multi-AP network, the instruction configure the processing circuitry to:

encode a null data packet announcement (NDPA) frame for multi-AP channel sounding, the NDPA for transmission to a second AP (AP2) and a plurality of stations (STAs) of an EHT group, the NDPA encoded to have an information field indicating whether a sounding sequence type is for JT channel sounding or CBF channel sounding, the NDPA further encoded to include fields identifying APs participating in the channel sounding including the AP1 and the AP2;

encode a first null data packet (NDP1) for transmission to the STAs of the EHT group, the NDP1 to be transmitted concurrently with a second null data packet (NDP2) from the AP2, the NDP1 and the NPD2 comprising sounding sequences for either the JT channel sounding or the CBF channel sounding, the NDP1 and the NPD2 transmitted via a plurality of spatial streams; and

decode a channel state information (CSI) report frame receive from each STA of the EHT group, wherein each CSI report frame includes channel state information determined by one of the STAs of the EHT group based on both the NDP1 and the NDP2,

wherein for the CBF channel sounding, the CSI reports are determined by the STAs separately for the NDP1 and the NDP2, and

wherein for the JT channel sounding, the CSI reports are determined by the STAs from a combined reception of the NDP1 and the NDP2.

12. The non-transitory computer-readable storage medium of claim 11 , wherein the NDPA frame is further encoded to indicate whether the AP1 will transmit a beam-forming refinement phase (BFRP) trigger frame solicit the CSI report from each of the STAs, and

wherein when the NDPA is encoded to indicate that the AP1 will transmit the BFRP trigger frame, the processing circuitry is further configured to:

encode the BFRP trigger frame for transmission a short inter-frame spacing (SIFS) after the NDP1 to the STAs of the EHT group to solicit the CSI report from each of the STAs.

13. The non-transitory computer-readable storage medium of claim 12 , wherein for the CBF channel sounding, the processing circuitry is further configured to determine beamforming vectors based on the CSI reports.

14. The non-transitory computer-readable storage medium of claim 13 , wherein the fields identifying APs participating in the channel sounding comprise AP information fields, and wherein the AP information fields further include a number of spatial streams to be transmitted by each of the APs participating in the channel sounding.

15. The non-transitory computer-readable storage medium of claim 14 , wherein the AP information fields further include a mapping between the spatial streams and a P-matrix, for use by the STAs is performing a singular value decomposition (SVD) on a channel matrix obtained from the NDP1 and the NDP2, and

wherein the P-matrix is a complex square matrix having positive principal minors.

16. The non-transitory computer-readable storage medium of claim 15 , wherein the AP information fields further indicate whether each AP will transmit the BFRP trigger frame to solicit CSI reports from the STAs or whether an AP is able to receive a CSI report from another AP over a backhaul.

17. The non-transitory computer-readable storage medium of claim 11 , wherein the information field indicating whether the sounding sequence type is for the JT channel sounding or the CBF channel sounding is a common information field.

18. The non-transitory computer-readable storage medium of claim 11 , wherein the NDPA frame is further encoded to include a STA information fields for each of the STAs of the EHT group, wherein each STA information field is encoded to include an indicator indicating whether the sounding sequence type, for an associated STA of the EHT group, is for the JT channel sounding or the CBF channel sounding.

19. An apparatus of station (STA) configured for multi-AP coordinated beamforming (CBF) and multi-AP joint transmission (JT) in an Extremely High Throughput (EHT) wireless local area network (WLAN), the apparatus comprising: processing circuitry and memory,

decode a null data packet announcement (NDPA) frame for multi-AP channel sounding, the NDPA received from an access point operating as a master AP (AP1) in a multi-AP network that includes a second AP (AP2) and one or more other stations (STAs) of an EHT group, the NDPA having an information field indicating whether a sounding sequence type is for JT channel sounding or CBF channel sounding, the NDPA further including fields identifying APs participating in the channel sounding including the AP1 and the AP2;

decode a first null data packet (NDP1) received from the AP1 and a second null data packet (NDP2) from the AP2, the NDP1 and the NPD2 comprising sounding sequences for either the JT channel sounding or the CBF channel sounding, the NDP1 and the NPD2 received via a plurality of spatial streams; and

encode a channel state information (CSI) report frame for transmission to the AP1, wherein the CSI report frame includes channel state information determined by the STA based on both the NDP1 and the NDP2,

wherein for the CBF channel sounding, the CSI report is determined by the STA separately for the NDP1 and the NDP2, and

wherein for the JT channel sounding, the CSI report is determined by the STA from a combined reception of the NDP1 and the NDP2.

20. The apparatus of claim 19 , wherein the NDPA frame indicate whether the AP1 will transmit a beam-forming refinement phase (BFRP) trigger frame solicit the CSI report from each of the STAs, the processing circuitry is further configured to:

decode the BFRP trigger frame to be received a short inter-frame spacing (SIFS) after the NDP1 to solicit the CSI report from the STA.