A beam forming method applicable to a multi-array antenna system, comprising: deriving an estimation of the channel impulse response h ka n as seen by each antenna element in the multi-array antenna system, wherein ka = 1... K a n, n = 1... N, N represents the total number of arrays and is more than one, and K a n represents the total number of antenna elements in the n th array, wherein h ka n are arranged into N channel matrixes H n, where H n = h 1 T, h 2 T,... h K a n T T and wherein a joint channel matrix H is defined as H = H 1 T, H 2 T,... H N T T, wherein (•) T represents transposition of a vector or matrix; deriving a spatial cross correlation matrix R n of a channel corresponding to each array of antennas from h ka n, where R n = H n ⁢ H n H, wherein (•) H represents conjugated transposition of a vector or matrix; deriving antenna array weight vectors w gob n, n =1... N of each array of antennas from R n in a GOB algorithm, said GOB algorithm being implemented with steps of: defining a predefined set of array response vectors a n (φ l), which cover certain scanning angles φ l, l = 1... L, L representing the total number of scanning angles, computing the power p l n of the received signal for every array response vector a n (φ l), where p l n = a n ⁢ φ l H ⁢ R n ⁢ a n φ l, n = 1... N, l = 1... L, and choosing as antenna array weight vector w gob n the array response vector a n (φ max), where φ max is the φ l that maximizes, for a constant n, the power p l n, providing the maximum power for beam forming;; deriving a spatial cross correlation matrix R of a joint channel of all of the arrays of antennas from h ka n as R = HH H; deriving an eigenvector w ebb corresponding to the maximum eigenvalue of R, where w ebb = w 1 T, w 2 T,... w N T T, each of the N subarrays w n of w ebb being the array weight vector of the n th array of antennas; deriving a phase difference Δφ n between each two arrays of antennas from w gob n and w n as Δ ⁢ φ n = arg w gob n H ⁢ w n T, n = 1... N; deriving a total GOB antenna array weight vector w gob of all arrays of antennas from w gob n and Δ ⁢ φ n as w gob = w gob 1 ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ 1, w gob 2 ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ 2,... w gob N ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ N; and performing beam forming based transmission using w gob. deriving an estimation of the channel impulse response h ka n as seen by each antenna element in the multi-array antenna system, wherein ka = 1... K a n, n = 1... N, N represents the total number of arrays and is more than one, and K a n represents the total number of antenna elements in the n th array, wherein h ka n are arranged into N channel matrixes H n, where H n = h 1 T, h 2 T,... h K a n T T and wherein a joint channel matrix H is defined as H = H 1 T, H 2 T,... H N T T, wherein (•) T represents transposition of a vector or matrix; deriving a spatial cross correlation matrix R n of a channel corresponding to each array of antennas from h ka n, where R n = H n ⁢ H n H, wherein (•) H represents conjugated transposition of a vector or matrix; deriving antenna array weight vectors w gob n, n =1... N of each array of antennas from R n in a GOB algorithm, said GOB algorithm being implemented with steps of: defining a predefined set of array response vectors a n (φ l), which cover certain scanning angles φ l, l = 1... L, L representing the total number of scanning angles, computing the power p l n of the received signal for every array response vector a n (φ l), where p l n = a n ⁢ φ l H ⁢ R n ⁢ a n φ l, n = 1... N, l = 1... L, and choosing as antenna array weight vector w gob n the array response vector a n (φ max), where φ max is the φ l that maximizes, for a constant n, the power p l n, providing the maximum power for beam forming;; defining a predefined set of array response vectors a n (φ l), which cover certain scanning angles φ l, l = 1... L, L representing the total number of scanning angles, computing the power p l n of the received signal for every array response vector a n (φ l), where p l n = a n ⁢ φ l H ⁢ R n ⁢ a n φ l, n = 1... N, l = 1... L, and choosing as antenna array weight vector w gob n the array response vector a n (φ max), where φ max is the φ l that maximizes, for a constant n, the power p l n, providing the maximum power for beam forming;; deriving a spatial cross correlation matrix R of a joint channel of all of the arrays of antennas from h ka n as R = HH H; deriving an eigenvector w ebb corresponding to the maximum eigenvalue of R, where w ebb = w 1 T, w 2 T,... w N T T, each of the N subarrays w n of w ebb being the array weight vector of the n th array of antennas; deriving a phase difference Δφ n between each two arrays of antennas from w gob n and w n as Δ ⁢ φ n = arg w gob n H ⁢ w n T, n = 1... N; deriving a total GOB antenna array weight vector w gob of all arrays of antennas from w gob n and Δ ⁢ φ n as w gob = w gob 1 ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ 1, w gob 2 ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ 2,... w gob N ⁢ e j ⋅ 2 ⁢ π ⋅ Δ ⁢ φ N; and performing beam forming based transmission using w gob.