Patent Document ID: 8175189
Application ID: 12401711
Patent Flag: 1

Claim One:
1. A method for processing user symbols with a generalized decision feedback equalizer (GDFE) based precoder in a base station of a multi-user multiple-input multiple-output (MU-MIMO) wireless system having K user terminals (UTs) with L k antennas each, each user terminal (UT) having associated therewith a feedforward filter represented by F 1 , F 2. .. , F K , the method comprising: computing a filter matrix C using one of the following expressions 
 C =( HVΣ 1/2 ) H [HS xx H H +S zz ] −1 where V is a unitary matrix, Σ is a diagonal matrix with non-negative entries, superscript H denotes conjugate transpose, and S zz is a least favorable noise covariance matrix, where S xx is an input covariance matrix for the downlink channel S xx = I - [ H H ⁢ DH + I ] - 1 λ , where I is an identity matrix, H is a channel matrix representing a channel through which communications occur in the wireless system, D is an input covariance matrix for an equivalent Uplink/medium access channel (MAC) in the wireless system which is chosen to be capacity optimal, and λ is a scalar variable for a given total transmit power P t , 
 λ=trace( I−[H H DH+I] −1 )/ P t , 
 C =λ( VΣ 1/2 ) H H † for a channel matrix H whose rank is greater than or equal to its number of rows, where superscript † denotes a Moore-Penrose Generalized Inverse, 
 C =( VΣ 1/2 ) H H † for a channel matrix H whose rank is greater than or equal to its number of rows, and 
 C =[√{square root over (Σ † )}−λ√{square root over (Σ)}] V H H H D (iv) wherein a feedforward filter matrix F is represented by F=GM H C, M is a unitary matrix, and G is an interference pre-cancellation matrix used in a transmitter at an interference pre-cancellation stage of the GDFE precoder; computing the matrix M using QR decomposition (QRD) of C as 
 C=MR; computing the feedforward filter matrix F as 
 F =BlockDiagonal( R ) where the BlockDiagonal(.) function extracts submatrices F 1 , F 2. .. , F k of size {a k ×L k } from block diagonals of the matrix R, and a k is a number of symbols allotted to the k th user terminal (UT) and equals the rank of F k ; computing the interference pre-cancellation matrix G as 
 G=FR † where superscript † denotes a Moore-Penrose Generalized Inverse; and processing user symbols by a decision feedback equalizing stage of the GDFE precoder to produce filtered vector symbols.