Feedback scheme for mu-mimo

Abstract

Embodiments of a system and method for managing feedback in a MU-MIMO system. An access point can announce one or more of mobile stations that are to receive downlink information in a first frame. The access point can also send a sounding package to the one or more mobile stations and receive feedback from the one or more mobile stations according to the feedback schedule. The feedback may be based on the reception of the sounding package.

What is claimed is: 
     
         1 . A method for managing feedback in a multiple user multiple input multiple output (MU-MIMO) system, the method comprising:
 announcing one or more mobile stations that are to receive downlink information in a first frame;   sending a sounding package to the one or more mobile stations;   assigning a feedback schedule for the one or more mobile stations; and   receiving feedback from the one or more mobile stations according to the feedback schedule, the feedback based on reception of the sounding package.   
     
     
         2 . The method of  claim 1 , comprising:
 receiving feedback capability from the one or more mobile stations;   assigning a feedback matrix dimension for the one or more mobile stations;   assigning a modulation and coding scheme for the one or more mobile stations;   assigning a feedback type for the one or more mobile stations based on the feedback capability for the one or more mobile stations;   determining a length of the feedback for each of the one or more mobile stations; and   wherein the feedback schedule comprises time slots for each of the one or more mobile stations based on the length of feedback for the one or more mobile stations.   
     
     
         3 . The method of  claim 1 , wherein the length of the feedback for a first mobile station is determined based on the modulation and coding scheme to be used, the feedback type, the feedback matrix dimension, and the number of downlink streams allocated to the first mobile station. 
     
     
         4 . The method of  claim 1 , wherein the feedback type includes one of un-compressed channel state information feedback, un-compressed precoding matrix, and compressed precoding matrix feedback. 
     
     
         5 . The method of  claim 4 , wherein receiving feedback capability includes receiving information regarding which of the un-compressed channel state information feedback, un-compressed precoding matrix, and compressed precoding matrix feedback are supported by a mobile station. 
     
     
         6 . The method of  claim 1 , comprising:
 setting the modulation and coding scheme for the first frame using the feedback received from the one or more mobile station;   transmitting the first frame to the one or more mobile stations; and   receiving refined feedback from the one or more mobile station based on reception of the first frame.   
     
     
         7 . The method of  claim 1 , updating the modulation and coding scheme for the one or more mobile stations based on the refined feedback. 
     
     
         8 . The method of  claim 1 , wherein feedback type is assigned based on a precoding complexity used by the access point, wherein less complex precoding corresponds to feedback types providing less information. 
     
     
         9 . A method for generating feedback at a first mobile station in a multiple user multiple input multiple output (MU-MIMO) system, the method comprising:
 receiving a sounding package from an access point;   calculating a number of streams for other mobile stations to be transmitted in a downlink frame;   determining a feedback matrix for streams intended for the first mobile station based on the number of streams and a reception quality of the sounding package, wherein a feedback matrix type and dimension is specified in the sounding package; and   sending the feedback matrix to the access point.   
     
     
         10 . The method of  claim 9 , comprising:
 receiving an indication of the number of streams allocated to each mobile station in the downlink frame, wherein calculating a number includes summing the number of streams allocated to other mobile stations.   
     
     
         11 . The method of  claim 9 , wherein determining a modulation and coding scheme includes calculating the modulation and coding scheme by applying random and uniform interference from streams allocated to other mobile stations, and by assuming that streams allocated to other mobile stations are transmitted with substantially equal power. 
     
     
         12 . The method of  claim 9 , comprising:
 receiving the downlink frame from the access point, wherein the downlink frame is transmitted using the modulation and coding scheme sent to the access point; and   adjusting the modulation and coding scheme based on the reception quality of the downlink frame.   
     
     
         13 . The method of  claim 12 , comprising:
 sending the adjusted modulation and coding scheme to the access point on as a piggyback with an ACK/NACK corresponding to the downlink frame.   
     
     
         14 . The method of  claim 9 , wherein the feedback is sent to the access point according to a feedback schedule provided by the access point. 
     
     
         15 . An system comprising:
 an access point configured to:
 announce one or more mobile stations that are to receive downlink information in a frame; 
 send a sounding package to the one or more mobile stations; 
 assign a feedback schedule for the one or more mobile stations; and 
 receive feedback from the one or more mobile stations according to the feedback schedule, the feedback based on reception of the sounding package. 
   
     
     
         16 . The system of  claim 15 , wherein the access point is configured to:
 receive feedback capability from the one or more mobile stations;   assign a feedback matrix dimension for the one or more mobile stations;   assign a modulation and coding scheme for the one or more mobile stations;   assign a feedback type for the one or more mobile stations based on the feedback capability for the one or more mobile stations;   determine a length of the feedback for each of the one or more mobile stations; and   wherein the feedback schedule comprises time slots for each of the one or more mobile stations based on the length of feedback for the one or more mobile stations.   
     
     
         17 . The system of  claim 15 , wherein the one or more mobile stations are configure to:
 receive a sounding package from the access point;   calculate a number of streams for other mobile stations to be transmitted in the frame;   determine a feedback matrix based on the total number of streams and a reception quality of the sounding package, wherein the feedback matrix is generated according to the feedback type assigned in the sounding package; and   send the feedback matrix to the access point in a time slot assigned in the sounding package and using a modulation and coding scheme assigned by the sounding package.   
     
     
         18 . The system of  claim 17 , wherein the access point is configured to:
 adjust precoding matrixes according to the feedback received from the one or more mobile stations; and   transmit the frame to the one or more mobile stations using the precoding matrixes.   
     
     
         19 . The system of  claim 18 , wherein the one or more mobile stations are configured to:
 receive the frame;   refine a modulation and coding scheme based on the reception quality of the frame; and   send the modulation and coding scheme to the access point with an ACK/NACK corresponding to the frame.   
     
     
         20 . The system of  claim 15 , wherein the access point is configured to communicate according to an IEEE 802.11ac standard.