System and method for backhaul based sounding feedback

Abstract

A system and method for backhaul based explicit sounding feedback of 802.11 AP to AP channel state information (CSI) so that inter AP interference can be reduced and multiple APs transmissions that can occur simultaneously on the same radio channel. A modification may be made to APs such that they can accurately measure the CSI between them that in turn enables their respective beamformer to create pattern nulls toward each other while simultaneously developing pattern enhancements toward their intended station. An AP may send a sounding packet to its associated STAs, poll explicit feedbacks from STAs and receive backhaul CSI feedbacks from neighboring APs. There is no additional Wi-Fi overhead in physical layer. Backhaul feedback link is established through direct peer-to-peer (P2P) link which bypassed the sounding controller to reduce CSI feedback delay.

What is claimed is: 
     
       1. A method implemented in an access point (AP) configured to exchange messages with at least one associated station (STA) via a wireless channel, the AP comprising: a plurality of antennas, radio circuitry configured to transmit and receive via said antennas, and a baseband processor, the method comprising:
 establishing a backhaul link with at least one co-channel neighboring AP, 
 sending a sounding packet to said at least one associated STA over the wireless channel, 
 obtaining channel state information (CSI) feedback from said at least one co-channel neighboring AP via the backhaul link, 
 determining that the radiation pattern of the AP towards said at least one co-channel neighboring AP can be reduced sufficient to protect the AP from interference from the at least one co-channel neighboring AP, 
 generating a radiation pattern that is reduced towards said at least one co-channel AP, and 
 exchanging messages with at least one associated station (STA) via a wireless channel at the same time as generating said reduced radiation pattern, 
 wherein prior to said determining, generating and exchanging, determining that a network allocation vector (NAV) for the channel is set by one said co-channel neighboring AP, and 
 wherein said determining uses the CSI, obtained via a backhaul link, for a co-channel neighboring AP that has set the NAV. 
 
     
     
       2. The method according to  claim 1  wherein the at least one co-channel neighboring AP is operating within a clear channel assessment (CCA) range of said AP. 
     
     
       3. The method according to  claim 1  wherein establishing said backhaul link comprises:
 transmitting a query for an address of said at least one co-channel neighboring AP; and 
 receiving a response comprising an address for each said at least one co-channel AP. 
 
     
     
       4. The method according to  claim 3  comprising:
 sending said query to a controller, 
 receiving said response from said controller, and 
 establishing said backhaul link with said at least one co-channel neighboring AP as a peer-to-peer (P2P) link which bypasses said controller. 
 
     
     
       5. The method according to  claim 1  in which said obtaining comprises obtaining CSI for multiple co-channel neighboring APs and the method further comprises comprising compiling a table of most recently obtained CSI for said multiple co-channel neighboring APs. 
     
     
       6. The method according to  claim 1  further comprising detecting a sounding packet sent by a co-channel neighboring AP via a wireless channel to at least one STA associated with the neighboring AP, and in response to said detecting sending CSI to said at least one neighboring AP via a backhaul link. 
     
     
       7. The AP according to  claim 1 , the baseband processor is configured to query the sounding controller about the neighboring AP's backhaul IP address by decoded MAC transmitter address in received beacon. 
     
     
       8. An access point (AP) configured to exchange messages with at least one associated station (STA) via a wireless channel, the AP comprising:
 a plurality of antennas, 
 radio circuitry configured to transmit and receive via said antennas, and 
 a baseband processor, wherein the baseband processor is configured to cause the AP to:
 establish a backhaul link with at least one co-channel neighboring AP, 
 send a sounding packet to said at least one associated STA over the wireless channel, wherein the sounding packet is sent according to the multi-user multiple input multiple output (MU-MIMO) sounding protocol, 
 obtain channel state information (CS I) feedback from said at least one neighboring AP via the backhaul link and from its associated STAs over-the-air according to the MU-MIMO sounding protocol, and 
 determine one or more weights for signals transmitted to or received from said antennas to generate a radiation pattern to reduce interference between said AP and at least one co-channel neighboring AP based on said CSI feedback. 
 
 
     
     
       9. The AP according to  claim 8  wherein the radio circuitry is configured to operate in compliance with the IEEE 802.11 standard. 
     
     
       10. An access point (AP) configured to exchange messages with at least one associated station (STA) via a wireless channel, the AP comprising:
 a plurality of antennas, 
 radio circuitry configured to transmit and receive via said antennas, and 
 a baseband processor, wherein the baseband processor is configured to:
 establish a backhaul link with at least one neighboring AP, 
 detect a sounding packet sent by the neighboring AP to at least one associated STA over the wireless channel, 
 send channel state information (CSI) to said at least one neighboring AP via the backhaul link, 
 indicate that it is capable of responding to sounding packets by transmitting identification of this capability, wherein the identification of this capability is transmitted in a beacon management frame of the AP, and 
 operate in compliance with the IEEE 802.11 standard and to register its backhaul IP address, Wi-Fi SSID, and Wi-Fi MAC address to a sounding controller via a backhaul link at power-up. 
 
 
     
     
       11. A communication system comprising a plurality of access points (APs) each configured to:
 exchange messages with at least one associated station (STA) via a wireless channel, 
 establish a backhaul link with at least one co-channel neighboring AP, 
 send a sounding packet to said at least one associated STA over the wireless channel, 
 obtain channel state information (CSI) feedback from said at least one neighboring AP via the backhaul link, the system further comprising a sounding controller for registration of said APs, each AP being configured to register with said sounding controller, 
 determine that the radiation pattern of the AP towards said at least one co-channel neighboring AP can be reduced sufficient to protect the AP from interference from the at least one co-channel neighboring AP, 
 generate a radiation pattern that is reduced towards said at least one co-channel AP, and 
 exchange messages with at least one associated station (STA) via a wireless channel at the same time as generating said reduced radiation pattern, 
 wherein prior to said determining, generating and exchanging, determining that a network k allocation vector (NAV) for the channel is set by one said co-channel neighboring AP, and 
 wherein said determining uses the CSI, obtained via a backhaul link, for a co-channel neighboring AP that has set the NAV.