Patent ID: 8483265

Claim:
A method for processing user symbols with a generalized decision feedback equalizer (GDFE) based precoder in a base station (BS) of a multi-user multiple-input multiple-output (MU-MIMO) wireless system having K user terminals (UTs) which communicate with the base station via an uplink (UL) channel and a corresponding downlink (DL) channel, the base station having N t antennas and P t as available transmit power, the DL channel being represented by a DL channel matrix H DL , the method comprising: a processor computing an effective UL channel matrix H UL using one of two methods (i) H UL =H DL H , or H UL =[(P t /N t )H DL H H DL +I] −1/2 H DL H ; extracting H k , k=1, 2, . . . , K, from the UL channel matrix H UL [H 1 H , H 2 H , . . . , H k H ] where H k H corresponds to an equivalent UL channel for the k th UT, and I is an identity matrix; computing a singular value decomposition (SVD) of the DL channel between the BS and k th UT, H k , for all K UTs, H k =U k S k V k H where U k denotes left singular vectors, S k is a diagonal matrix with singular values making up the diagonal, and V k denotes right singular vectors; extracting all singular values as s =[diag( S 1 ), . . . , diag( S K )]; extracting a vector ŝ from s by choosing first utmost N t largest non-zero singular values of s; sorting elements in ŝ in decreasing order; performing water-filling to allocate power and obtain a diagonal matrix Γ k representing power allocations corresponding to the singular values of the k th UT; computing an UL covariance matrix for each UT as Φ k =U k Γ k U k H ; obtaining an overall input covariance matrix D for the equivalent UL channel as D = BlockDiag ⁡ [ Φ 1 , Φ 2 , … ⁢ , Φ K ] = [ Φ 1 0 0 0 ⋮ 0 0 0 Φ K ] where BlockDiag(.) function generates a block diagonal matrix by placing input matrix arguments at diagonals; computing a filter matrix C based on the UL covariance matrix D; computing a feedforward filter matrix F based on the filter matrix C; computing an interference pre-cancellation matrix G, based on the feedforward filter matrix F and the filter matrix C, used in a transmitter at an interference pre-cancellation stage of the GDFE precoder; and processing user symbols by a decision feedback equalizing stage of the GDFE precoder to produce filtered vector symbols.