Patent ID: 8649457

Claim:
Precoding process for a transmitter of a MU-MIMO communication system comprising: M antennas in the transmitter and K User Equipments (UE), said precoding being based on a Regularized Zero Forcing (R-ZF) linear precoding of the type: G = H H ⁡ ( HH H + M ⁢ ⁢ α ⁢ ⁢ I K ) - 1 = ( H H ⁢ H + M ⁢ ⁢ α ⁢ ⁢ I M ) - 1 ⁢ H H With: H being a complex matrix representative of the K×M channel estimates, said H matrix comprising channel coefficients which are correlated with corresponding correlation coefficients being the entries of a correlation matrix ⊖ T , I K and I M being the identity matrix, respectively of size K×K and M×M; And α being the regularization parameter, wherein α is computed as follows: a) computing the correlation matrix ⊖ T ; b) initializing two parameters α max and α min ; c) computing α=½(α max +α min ); d) determining ( 140 ) for z=−α the value of S (S H′ ω Θ T H′ ω H (z)) solving the fixed-point equation: S ⁡ ( z ) = ( ∫ λ ⁢ ⁢ μ Θ T ⁡ ( λ ) ⁢ ⅆ λ 1 + λ β ⁢ S ⁡ ( z ) - z ) - 1 With λ being the eigenvalues of the correlation matrix ⊖ T , μ being the empirical eigenvalue distribution functions of ⊖ T and β being M/K; e) determining for z=−α the value of S d ( ⅆ ⅆ x ⁢ S H w ′ ⁢ Θ T ⁢ H w ′ ⁢ ⁢ H ⁡ ( z ) ) solving the fixed-point equation: S d ⁡ ( z ) = 1 + ∫ λ 2 β ⁢ S d ⁡ ( z ) ( 1 + λ β ⁢ S ⁡ ( z ) ) 2 ⁢ μ Θ T ⁡ ( λ ) ⁢ ⅆ λ ( S ⁡ ( z ) ) - 2 f) computing the equation F = S β + β - 1 β ⁢ ⁢ α - α ⁡ ( S d β + β - 1 β ⁢ ⁢ α 2 ) g) adapting the interval [α min , α max ] as follows: if F−P<0, with P being the total available transmit power, then computing ( 180 ) α max =α, otherwise computing α min =α.