Patent ID: 8842782

Claim:
An apparatus for filtering a received signal to obtain a filtered signal, wherein the received signal has been transmitted by conducting a transmission, wherein the apparatus comprises: a detector configured to detect whether the transmission is either a single-user Multiple Input Multiple Output transmission or a multi-user Multiple Input Multiple Output transmission, and a filter application unit, wherein the filter application unit is configured to apply a first receive filter with a first filter characteristic on the received signal to obtain the filtered signal when the transmission is the single-user Multiple Input Multiple Output transmission, and wherein the filter application unit is configured to apply a second receive filter with a second, different filter characteristic on the received signal to obtain the filtered signal when the transmission is the multi-user Multiple Input Multiple Output transmission, wherein the detector is configured to determine whether a ratio of a maximum of main-diagonal coefficients of an interference-plus-noise covariance matrix and an average noise power is greater than one to determine whether the transmission is the multi-user Multiple Input Multiple Output transmission or the single-user Multiple Input Multiple Output transmission, wherein the filter application unit is configured to apply a Minimum-Mean-Square-Error receive filter as the second receive filter on the received signal when the transmission is the multi-user Multiple Input Multiple Output transmission, the Minimum-Mean-Square-Error receive filter being defined according to m _ MMSE H = g _ 1 H ⁢ R _ ηη _ - 1 g _ 1 H ⁢ R _ ηη - 1 ⁢ g _ 1 as the second receive filter on the received signal when the transmission is the multi-user Multiple Input Multiple Output transmission, wherein g 1 denotes a matrix-vector product H 1 p i , wherein H 1 denotes the channel from an eNodeB to a user equipment, wherein p i denotes a precoding vector recommended by the user equipment, wherein g 1 H denotes a Hermitian of the matrix-vector product g 1 , and wherein R ηη −1 denotes an inverse matrix of a covariance matrix R ηη .