A method for inserting K quadruplets of a first, a second, a third and a fourth Reference Signals in a radio signal to be transmitted over a wireless communication system, said radio signal being 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 1, of different frequencies, and K being a strictly positive integer smaller than or equal to M/2, said radio signal being provided by: - applying to a first block of M symbols X=(X 0,...X M-1) a precoder to obtain a second block of M symbols Y=(Y 0,...Y M-1), with Y k = { ε X ∗ M 2 + P 1 + mod − k + P 1 + p − 1, Q, for k ∈ 〚 P 1; M 2 − P 2 〚 − ε X ∗ P 1 + mod − k + P 1 + M 2 + p − 1, Q, for k ∈ 〚 M 2 + P 1; M − P 2 〚, with P 1 and P 2 predefined positive integers, such as P 1 +P 2 is strictly smaller than M/2, p a predefined integer and ε is 1 or -1 and X k * being the complex conjugate of X k; - applying at least a M size DFT then a N size IDFT corresponding to a first transmit antenna, to the first block of M symbols to obtain a first single-carrier frequency division multiple access, SC-FDMA, symbol representing the first block of M symbols, said first SC-FDMA symbol being of a given duration; - applying at least a M size DFT then a N size IDFT corresponding to a second transmit antenna, to the second block of M symbols to obtain a second single-carrier frequency division multiple access, SC-FDMA, symbol representing the second block of M symbols, said second SC-FDMA symbol being of the given duration; - transmitting during a time interval of the given duration, respectively on the first and second transmit antennas, simultaneously the first and second SC-FDMA symbols, into the radio signal; said method comprising: - determining a number L smaller than or equal to min(M/2-P 1 -P 2; K) of integers such as n i | i ∈ 〚 1; L 〛, P 1 ≤ n i < M 2 − P 2, ∀ i, j ∈ 〚 1; L 〛 2, i < j ⇒ n i < n j; and for each i-th quadruplet out of L quadruplets of a first, a second, a third and a fourth Reference Signals among the K quadruplets: - inserting the first Reference Signal such as samples of the first Reference Signal are in positions in the first SC-FDMA symbol dependent on a position n i of the symbol X n i in the first block of M symbols; - inserting the second Reference Signal such as samples of the second Reference Signal are in positions in the first SC-FDMA symbol dependent on the position M 2 + P 1 + mode ( n i + P 1 + p- 1, Q) of the symbol X M 2 + P 1 + mod − n i + P 1 + p − 1, Q in the first block of M symbols; - inserting the third Reference Signal such as samples of the third Reference Signal are in positions in the second SC-FDMA symbol dependent on a position n i of the symbol X n i in the first block of M symbols; - inserting the fourth Reference Signal such as samples of the fourth Reference Signal are in positions in the second SC-FDMA symbol dependent on the position M 2 + P 1 + mode (- n i + P 1 + p- 1, Q) of the symbol X M 2 + P 1 + mod − n i + P 1 + p − 1, Q in the first block of M symbols. - applying to a first block of M symbols X=(X 0,...X M-1) a precoder to obtain a second block of M symbols Y=(Y 0,...Y M-1), with Y k = { ε X ∗ M 2 + P 1 + mod − k + P 1 + p − 1, Q, for k ∈ 〚 P 1; M 2 − P 2 〚 − ε X ∗ P 1 + mod − k + P 1 + M 2 + p − 1, Q, for k ∈ 〚 M 2 + P 1; M − P 2 〚, with P 1 and P 2 predefined positive integers, such as P 1 +P 2 is strictly smaller than M/2, p a predefined integer and ε is 1 or -1 and X k * being the complex conjugate of X k; - applying at least a M size DFT then a N size IDFT corresponding to a first transmit antenna, to the first block of M symbols to obtain a first single-carrier frequency division multiple access, SC-FDMA, symbol representing the first block of M symbols, said first SC-FDMA symbol being of a given duration; - applying at least a M size DFT then a N size IDFT corresponding to a second transmit antenna, to the second block of M symbols to obtain a second single-carrier frequency division multiple access, SC-FDMA, symbol representing the second block of M symbols, said second SC-FDMA symbol being of the given duration; - transmitting during a time interval of the given duration, respectively on the first and second transmit antennas, simultaneously the first and second SC-FDMA symbols, into the radio signal; - determining a number L smaller than or equal to min(M/2-P 1 -P 2; K) of integers such as n i | i ∈ 〚 1; L 〛, P 1 ≤ n i < M 2 − P 2, ∀ i, j ∈ 〚 1; L 〛 2, i < j ⇒ n i < n j; - inserting the first Reference Signal such as samples of the first Reference Signal are in positions in the first SC-FDMA symbol dependent on a position n i of the symbol X n i in the first block of M symbols; - inserting the second Reference Signal such as samples of the second Reference Signal are in positions in the first SC-FDMA symbol dependent on the position M 2 + P 1 + mode ( n i + P 1 + p- 1, Q) of the symbol X M 2 + P 1 + mod − n i + P 1 + p − 1, Q in the first block of M symbols; - inserting the third Reference Signal such as samples of the third Reference Signal are in positions in the second SC-FDMA symbol dependent on a position n i of the symbol X n i in the first block of M symbols; - inserting the fourth Reference Signal such as samples of the fourth Reference Signal are in positions in the second SC-FDMA symbol dependent on the position M 2 + P 1 + mode (- n i + P 1 + p- 1, Q) of the symbol X M 2 + P 1 + mod − n i + P 1 + p − 1, Q in the first block of M symbols.