... akbkakbkakkxxxrrh,,,,,,,~ 1 1 1 11 11 2 (19 ) akbkakbkakkxxxrrh,,,,,,,~ 1 1 1 11 21 2 (20) akbkakbkakkxxxrrh,,,,,,,~ 1 1 1 22 12 2 ... number of antennas is 4, a 4x4 matrix is needed. In our case, we use the following pilot matrix: 11 11 111 1 11 11 111 1P (4) where the number of rows represents ... ra 1, k = xa 1, k· h 11 ,k - xa 1, k· h 12 ,k + na 1, k = xa 1, k· (h 11 ,k - h 12 ,k )+ na 1, k (15 ) ra2,k = xa 1, k· h 21, k - xa 1, k· h22,k + na2,k = xa 1, k·...