A method for inserting K pairs of a first and a second Reference Signals in a radio signal to be transmitted over a wireless communication system, said radio signal being intended to be emitted by an emitter comprising at least two transmit antennas, each antenna being configured for transmitting on at least an even number M, strictly greater than 4, of different frequencies, and K being a strictly positive integer strictly smaller than M/2, said radio signal being provided by: - applying (S13; S23) a M size DFT to a block of symbols X=(X 0 , ...X M-1 ), and obtaining for each k th frequency, with k = 0 to M-1, a complex symbol S k in the frequency domain; - obtaining (S13; S23), at an output of an IDFT module corresponding to a first transmit antenna, during a given time interval a first signal representing, in the frequency domain, the complex symbols S k for each k th frequency with k = 0 to M-1; - obtaining (S13; S23), at an output of an IDFT module corresponding to a second transmit antenna, during the given time interval a second signal representing, in the frequency domain, the complex symbols (-1) k+1 εS ∗ (p-1-k)[M] for each k th frequency, with k = 0 to M-1 and p a predefined even integer lower or equal to M-1 and higher or equal to 0 and ε is 1 or -1 and S k ∗ being the complex conjugate of S k ; - emitting (S14) the radio signal corresponding to the first and second signal; said method comprising : - determining K integers such as n i | i ∈ 〚 1 ; K 〛 , 0 ≤ n i ≤ M 2 − 1 , ∀ i , j ∈ 〚 1 ; K 〛 2 , i < j ⇒ n i < n j ; and for each pair i of first and second Reference Signals : - inserting (S12) the first Reference Signal in the radio signal, such as samples of the first Reference Signal are in time periods in the radio signal, said time periods being dependent on a position n i of the symbol X n i in the block of symbols; - inserting (S12) the second Reference Signal in the radio signal, such as samples of the second Reference Signal are in time periods in the radio signal, said time periods being dependent on the position ( n i + M /2) of the symbol X ( n i + M /2) in the block of symbols. - applying (S13; S23) a M size DFT to a block of symbols X=(X 0 , ...X M-1 ), and obtaining for each k th frequency, with k = 0 to M-1, a complex symbol S k in the frequency domain; - obtaining (S13; S23), at an output of an IDFT module corresponding to a first transmit antenna, during a given time interval a first signal representing, in the frequency domain, the complex symbols S k for each k th frequency with k = 0 to M-1; - obtaining (S13; S23), at an output of an IDFT module corresponding to a second transmit antenna, during the given time interval a second signal representing, in the frequency domain, the complex symbols (-1) k+1 εS ∗ (p-1-k)[M] for each k th frequency, with k = 0 to M-1 and p a predefined even integer lower or equal to M-1 and higher or equal to 0 and ε is 1 or -1 and S k ∗ being the complex conjugate of S k ; - emitting (S14) the radio signal corresponding to the first and second signal; - determining K integers such as n i | i ∈ 〚 1 ; K 〛 , 0 ≤ n i ≤ M 2 − 1 , ∀ i , j ∈ 〚 1 ; K 〛 2 , i < j ⇒ n i < n j ; and for each pair i of first and second Reference Signals : - inserting (S12) the first Reference Signal in the radio signal, such as samples of the first Reference Signal are in time periods in the radio signal, said time periods being dependent on a position n i of the symbol X n i in the block of symbols; - inserting (S12) the second Reference Signal in the radio signal, such as samples of the second Reference Signal are in time periods in the radio signal, said time periods being dependent on the position ( n i + M /2) of the symbol X ( n i + M /2) in the block of symbols. <EOS>