Device and method for inserting quadruplet and device and method for extracting quadruplet

Abstract

The invention relates to inserting reference signals in a radio signal to be transmitted over a wireless communication system, the radio signal being emitted according to a specific SS-STBC scheme, the method comprising, inserting the reference signals to transmit them in the radio signal such as samples of these reference signals are in specific positions in the SS-STBC symbol.

Claims

1. 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 transmit 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 a first block of M symbols X=(X.sub.0, . . . X.sub.M−1) to a precoder to obtain a second block of M symbols Y=(Y.sub.0, . . . Y.sub.M−1), with $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, & for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{P_{1} + m o d (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, & for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix},$ with P.sub.1 and P.sub.2 predefined positive integers, such as P.sub.1+P.sub.2 is strictly smaller than M/2, p is a predefined integer, Q is a positive integer smaller than M/2, and ε is 1 or −1 and X.sub.k* being the complex conjugate of X.sub.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.sub.1−P.sub.2; K) of integers such as ${n_{i} | i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}};$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols.

2. The method according to claim 1, wherein for each quadruplet i, inserting the first, second, third and fourth Reference Signals is done by setting values of symbol X.sub.n.sub.i and symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ to respectively values representing the first and second Reference Signals of quadruplet i, before applying the precoder and the M size DFT corresponding to the first transmit antenna to the first block of M symbols.

3. The method according to claim 1, wherein for each quadruplet i, said method further comprises: setting the values of the symbol X.sub.n.sub.i and of the symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ to 0, with i∈ custom character 1;L, before applying the precoder to the first block of M symbols; inserting the first, second, third and fourth Reference Signals is done by: setting values of symbol X.sub.n.sub.i and symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ to respectively values representing the first and second Reference Signals of quadruplet i, after applying the precoder to the first block of M symbols and before applying the M size DFT corresponding to the first transmit antenna to the first block of M symbols; setting values of symbol Y.sub.n.sub.i and symbol $Y_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ to respectively values representing fourth and third Reference Signals of quadruplet i, before applying the M size DFT corresponding to the second transmit antenna to the second block.

4. The method according to claim 1, wherein for each quadruplet i, said method further comprises: setting the values of the symbol X.sub.n.sub.i and of the symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ to 0, with i∈ custom character 1;L, before applying the precoder and the M size DFT to the first block of M symbols; inserting the first, second, third and fourth Reference Signals is done by: adding samples of the first Reference Signal and samples of the second Reference Signal to an output signal of the N size IDFT corresponding to the first transmit antenna, to obtain the first SC-FDMA symbol; adding samples of the third Reference Signal and samples of the fourth Reference Signal to an output signal of the N size IDFT corresponding to the second transmit antenna, to obtain the second SC-FDMA symbol.

5. The method according to claim 4, said method further comprising to set the output signal of the N size IDFT corresponding to the first transmit antenna to 0 at least during a time period corresponding to one of the positions in the first SC-FDMA symbol dependent on the position n.sub.i of the symbol X.sub.n.sub.i and/or the position $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols; and/or to set the output signal of the N size IDFT corresponding to the second transmit antenna to 0 at least during a time period corresponding to one of the positions in the second SC-FDMA symbol dependent on the position n.sub.i of the symbol X.sub.n.sub.i and/or the position $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols, for at least one i∈ custom character 1;L before inserting the first, second, third and fourth Reference Signals of quadruplet i.

6. The method according to claim 1, said method further comprising determining: a number H of pairs of positive integers k.sub.1 and k′.sub.1 with l∈ custom character 1;H, with H strictly greater than 1, such as:
k.sub.1=1,k′.sub.H=L,
∀l∈1;H−1,k.sub.l<k′.sub.l<k.sub.l+1<k′.sub.l+1, a positive integer d strictly greater than 1; the L integers n.sub.i, with i∈1;L such as:
∀l∈1;L−1,n.sub.k.sub.l+1−n.sub.k′l≥d
∀l∈ custom character 1;L,n.sub.k′.sub.l−n.sub.k.sub.l=k′.sub.l−k.sub.l.

7. The method according to claim 1, said method further comprising determining: a positive integer d strictly greater than 1; the L integers n.sub.i, with i∈ custom character 1;L such as:
n.sub.i+1−n.sub.i≥d.

8. The method according to claim 1, wherein n.sub.L−n.sub.1=L−1.

9. The method according to claim 1, wherein a value ρ.sub.n.sub.i, such as the samples in the first SC-FDMA symbol that are obtained from the symbol X.sub.n.sub.i whose value is set to ρ.sub.n.sub.i are equal to the samples of the first reference signal of quadruplet i in the first SC-FDMA symbol, is a component of a CAZAC sequence; and/or wherein a value $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as the samples in the first SC-FDMA symbol that are obtained from the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the second reference signal of quadruplet i in the first SC-FDMA symbol, is a component of a CAZAC sequence; and/or wherein a value ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as use samples in the second SC-FDMA symbol that are obtained from the symbol $Y_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the third reference signal of quadruplet i in the second SC-FDMA symbol, is a component of a CAZAC sequence; and/or wherein a value ρ′.sub.n.sub.i, such as the samples in the second SC-FDMA symbol that are obtained from the symbol Y.sub.n.sub.i whose value is set to ρ′.sub.n.sub.i are equal to the samples of the fourth reference signal of quadruplet i in the second SC-FDMA symbol, is a component of a CAZAC sequence.

10. The method according to claim 1, wherein a value ρ.sub.n.sub.i, such as the samples in the first SC-FDMA symbol that are obtained from the symbol X.sub.n.sub.i whose value is set to ρ.sub.n.sub.i are equal to the samples of the first reference signal of quadruplet i in the first SC-FDMA symbol, is equal to a value $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as the samples in the first SC-FDMA symbol that are obtained from the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the second reference signal of quadruplet i in the first SC-FDMA symbol; and/or wherein a value ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as the samples in the second SC-FDMA symbol that are obtained from the symbol $Y_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ equal to the samples of the third reference signal of quadruplet i in the second SC-FDMA symbol, is equal to a value ρ′.sub.n.sub.i, such as the samples in the second SC-FDMA symbol that are obtained from the symbol Y.sub.n.sub.i whose value is set to ρ′.sub.n.sub.i are equal to the samples of the fourth reference signal of quadruplet i in the second SC-FDMA symbol.

11. The method according to claim 1, wherein a value ρ.sub.n.sub.i, such as the samples in the first SC-FDMA symbol that are obtained from the symbol X.sub.n.sub.i whose value is set to ρ.sub.n.sub.i are equal to the samples of the first reference signal of quadruplet i in the first SC-FDMA symbol, is equal to a value ρ′.sub.n.sub.i, such as the samples in the second SC-FDMA symbol that are obtained from the symbol Y.sub.n.sub.i whose value is set to ρ′.sub.n.sub.i are equal to the samples of the fourth reference signal of quadruplet i in the second SC-FDMA symbol; and/or wherein a value $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as the samples in the first SC-FDMA symbol that are obtained from the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ who value is set to $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the second reference signal of quadruplet i in the first SC-FDMA symbol, is equal to a value ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$ such as the samples in the second SC-FDMA symbol that are obtained from the symbol $Y_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the third reference signal of quadruplet i in the second SC-FDMA symbol.

12. The method according to claim 1, wherein a maximum module among modules of values ρ.sub.n.sub.i, $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q))}, {ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q))}$ and ρ′.sub.n.sub.i with i∈ custom character 1;L, is equal to or smaller than a maximum module among modules of modulation symbols of a digital modulation scheme used to obtain said block of symbols, with ρ.sub.n.sub.i such as the samples in the first SC-FDMA symbol that are obtained from the symbol X.sub.n.sub.i whose value is set to ρ.sub.n.sub.i are equal to the samples of the first reference signal of quadruplet i in the first SC-FDMA symbol, and $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ such as the samples in the first SC-FDMA symbol that are obtained from the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to $ρ_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the second reference signal of quadruplet i in the first SC-FDMA symbol, and ${ρ^{'}}_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ such as the samples in the second SC-FDMA symbol that are obtained from the symbol $Y_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ whose value is set to ${ρ^{'}}_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ are equal to the samples of the third reference signal of quadruplet i in the second SC-FDMA symbol, and ρ′.sub.n.sub.i such as the samples in the second SC-FDMA symbol that are obtained from the symbol Y.sub.n.sub.i whose value is set to ρ′.sub.n.sub.i are equal to the samples of the fourth reference signal of quadruplet i in the second SC-FDMA symbol.

13. The method according to claim 1, wherein a value ρ.sub.i, such as the samples in the first SC-FDMA symbol are obtained from the symbol X.sub.n whose value is set to ρ.sub.n, ρ.sub.n being: equal to a value ρ.sub.n+Q, such as the samples in the first SC-FDMA symbol are obtained from the symbol X.sub.n+Q whose value is set to ρ.sub.n+Q, if n∈ custom character 0;P.sub.1−1∪M/2;M/2+P.sub.1−1; equal to a value ρ.sub.n−Q such as the samples in the first SC-FDMA symbol are obtained from the symbol X.sub.n−Q whose value is set to ρ.sub.n−Q, if $n \in 〚 \frac{M}{2} - P_{2}; \frac{M}{2} - 1 〛 .Math. 〚 M - P_{2}; M - 1 〛;$ and/or a value ρ′.sub.n, such as the samples in the second SC-FDMA symbol are obtained from the symbol Y.sub.n whose value is set to ρ′.sub.n, ρ′.sub.n being: equal to a value ρ′.sub.n+Q, such as the samples in the second SC-FDMA symbol are obtained from the symbol X.sub.n+Q whose value is set to ρ′.sub.n+Q, if n∈ custom character 0;P.sub.1−1U M/2;M/2+P.sub.1−1; equal to a value ρ′.sub.n−Q, such as the samples in the second SC-FDMA symbol are obtained from the symbol X.sub.n−Q whose value is set to ρ′.sub.n−Q, if $n \in 〚 \frac{M}{2} - P_{2}; \frac{M}{2} - 1 〛 .Math. 〚 M - P_{2}; M - 1 〛 .$

14. A non-transitory computer readable medium having stored thereon a computer program product comprising code instructions that when executed by at least a processor cause the processor to perform 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 transmit 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 a first block of M symbols X=(X.sub.0, . . . X.sub.M−1) to a precoder to obtain a second block of M symbols Y=(Y.sub.0, . . . Y.sub.M−1), with $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{P_{1} + \mod (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix},$ with P.sub.1 and P.sub.2 predefined positive integers, such as P.sub.1+P.sub.2 is strictly smaller than M/2, p a predefined integer, Q is a positive integer smaller than M/2, and ε is 1 or −1 and X.sub.k* being the complex conjugate of X.sub.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.sub.1−P.sub.2; K) of integers such as ${n_{i} .Math. i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}};$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols.

15. A device 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 transmit 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 smaller than or equal to M/2, said radio signal being processed by: applying a first block of M symbols X=(X.sub.0, . . . X.sub.M−1) to a precoder to obtain a second block of M symbols Y=(Y.sub.0, . . . Y.sub.M−1), with $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{P_{1} + \mod (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix},$ with P.sub.1 and P.sub.2 predefined positive integers, such as P.sub.1+P.sub.2 is strictly smaller than M/2, p a predefined integer, Q is a positive integer smaller than M/2, and 6 is 1 or −1 and X.sub.k* being the complex conjugate of X.sub.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 device comprising: a processor; and a non-transitory computer-readable medium comprising instructions stored thereon, which when executed by the processor configure the device to: determine a number L smaller than or equal to min(M/2-P.sub.1-P.sub.2; K) of integers such as ${n_{i} .Math. i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}};$ 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 quadruplet: insert 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.sub.i of the symbol X.sub.n.sub.i in the first block of M symbols; insert 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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols; insert 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.sub.i of the symbol X.sub.n.sub.i in the first block of M symbols; insert 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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols.

16. A method for extracting K quadruplets of a first, a second, a third and a fourth Reference Signals in a radio signal received over a wireless communication system, said radio signal being emitted by an emitter comprising at least two transmit antennas, each transmit 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, the emission of the radio signal being processed by: applying a first block of M symbols X=(X.sub.0, . . . X.sub.M−1) to a precoder to obtain a second block of M symbols Y=(Y.sub.0, . . . Y.sub.M−1), with $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{P_{1} + \mod (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix},$ with P.sub.1 and P.sub.2 predefined positive integers, such as P.sub.1+P.sub.2 is strictly smaller than M/2, p a predefined integer, Q is a positive integer smaller than M/2, and ε is 1 or −1 and X.sub.k* being the complex conjugate of X.sub.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, in the radio signal; said first, second, third and fourth reference signals being inserted in the radio signal by: determining a number L smaller than or equal to min(M/2−P.sub.1−P.sub.2; K) of integers such as ${n_{i} .Math. i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}};$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols; said method comprising for at least one quadruplet i of first, second, third and fourth Reference Signals among the L quadruplets: extracting, before applying N size DFT on the received radio signal, parts of the radio signal, each part being received in one time window among time windows, said time windows being strictly included in the given time interval; processing said extracted parts independently from other parts of the received radio signal.

17. The method according to claim 16, wherein each time window among the time windows strictly includes at least one time period corresponding to the receiving of samples in a position among the positions in the first and/or second SC-FDMA symbols.

18. The method according to claim 16, wherein each time window among the time windows is strictly included in at least one time period corresponding to the receiving of samples in a position among the positions in the first and/or second SC-FDMA symbols.

19. The method according to claim 16, wherein each time window among the time windows is equal to one time period corresponding to the receiving of samples in a position among the positions in the first and/or second SC-FDMA symbols.

20. A device for extracting K quadruplets of a first, a second, a third and a fourth Reference Signals in a radio signal received over a wireless communication system, said radio signal being emitted by an emitter comprising at least two transmit antennas, each transmit 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, the emission of the radio signal being processed by: applying a first block of M symbols X=(X.sub.0, . . . X.sub.M−1) to a precoder to obtain a second block of M symbols Y=(Y.sub.0, . . . Y.sub.M−1), with $Y_{k} = {\begin{matrix} ε X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, for k \in \underline{〚 P_{1}; \frac{M}{2} - P_{2} 〚} \\ - ε X_{P_{1} + \mod (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, for k \in \underline{〚 \frac{M}{2} + P_{1}; M - P_{2} 〚^{'}} \end{matrix}$ with P.sub.1 and P.sub.2 predefined positive integers, such as P.sub.1+P.sub.2 is strictly smaller than M/2, p a predefined integer, Q is a positive integer smaller than M/2, and ε is 1 or −1 and X.sub.k* being the complex conjugate of X.sub.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 first, second, third and fourth reference signals being inserted in the radio signal by: determining a number L smaller than or equal to min(M/2−P.sub.1−P.sub.2; K) of integers such as ${n_{i} .Math. i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}};$ 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the rust 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.sub.i of the symbol X.sub.n.sub.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 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$ of the symbol $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$ in the first block of M symbols; said device comprising: a processor; and a non-transitory computer-readable medium comprising instructions stored thereon, which when executed by the processor configure the device to, for at least one quadruplet i of first, second, third and fourth Reference Signals: extract, before applying N size DFT modules on the received radio signal, parts of the radio signal, each part being received in one time window among time windows, said time windows being strictly included in the given time interval; process said extracted parts independently from other parts of the received radio signal.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates a SS-STBC type transmitter and receiver.

(2) FIG. 2.1 schematizes a block diagram of a classical SS-STBC transmitter.

(3) FIG. 2.2 details the SS-STBC pre-coder logical functioning.

(4) FIG. 3 schematizes a block diagram of a classical SS-STBC receiver.

(5) FIG. 4.1 schematizes a block diagram of pre-DFT insertion of RS according to the invention.

(6) FIG. 4.2 schematizes a block diagram of post pre-coder insertion of RS according to the invention.

(7) FIG. 4.3 schematizes a block diagram of post-IDFT insertion of RS according to the invention.

(8) FIG. 5 schematizes a block diagram of RS extraction and DATA decoding according to the invention.

(9) FIG. 6.1 illustrates a flowchart representing the steps of pre-DFT inserting reference signals in the radio signal according to the invention.

(10) FIG. 6.2 illustrates a flowchart representing the steps of post pre-coding insertion of reference signals in the radio signal according to the invention.

(11) FIG. 6.3 illustrates a flowchart representing the steps of post-IDFT inserting reference signals in the radio signal according to the invention.

(12) FIG. 7 illustrates a flowchart representing the steps of extracting reference signals in the radio signal according to the invention.

DESCRIPTION OF EMBODIMENTS

(13) Referring to FIG. 1, there is shown a transmitter 1.1 transmitting a radio signal to a receiver 1.2. The transmitter 1.1 is in the cell of the receiver 1.2. This transmission may be a SS-STBC based transmission in the context of OFDM based system. In this example the transmitter 1.1 is a mobile terminal and the receiver 1.2 is a fixed station which in the context of LTE is a base station. The transmitter 1.1 can as well be the fixed station and the receiver 1.2 a mobile terminal.

(14) The transmitter 1.1 comprises one communication module (COM_trans) 1.3, one processing module (PROC_trans) 1.4 and a memory unit (MEMO_trans) 1.5. The MEMO_trans 1.5 comprises a non-volatile unit which retrieves the computer program and a volatile unit which retrieves the reference signal parameters. The PROC_trans 1.4 which is configured to insert the reference signals according to the invention. The COM_trans is configured to transmit to the receiver 1.2 the radio signal. The processing module 1.4 and the memory unit 1.5 may constitute the device for inserting the reference signals, as previously described. The processing module 1.4 and the memory unit 1.5 can be dedicated to this device or also used for other functions of the transmitter like for processing the radio signal.

(15) The receiver 1.2 comprises one communication module (COM_recei) 1.6, one processing module (PROC_recei) 1.7 and a memory unit (MEMO_recei) 1.8. The MEMO_recei 1.8 comprises a non-volatile unit which retrieves the computer program and a volatile unit which retrieves the reference signal parameters. The PROC_recei 1.7 is configured to extract the reference signals from the radio signal. The COM_recei 1.6 is configured to receive from the transmitter the radio signal. The processing module 1.7 and the memory unit 1.8 may constitute the device for extracting the reference signals, as previously described. The processing module 1.7 and the memory unit 1.8 can be dedicated to this device or also used for other functions of the receiver like for processing the receiving scheme on the radio signal.

(16) Referring to FIG. 2.1, there is shown a block diagram of a classical SS-STBC transmitter. Such SS-STBC transmitters apply SC-FDMA schemes on a block of symbols (first block of symbols) and a pre-coded block of symbols (second block of symbols) to obtain the radio signal. This ensures full diversity for a rate of one symbol per channel use. An SS-STBC transmitter emits a radio signal by emitting on at least two transmit antennas Tx1 2.0 and Tx2 2.1.

(17) The radio signal being provided by applying a SS-STBC pre-coder 2.2 to a first block of symbols X=(X.sub.0, . . . X.sub.M−1) and obtaining a second block of symbols Y=(Y.sub.0, . . . Y.sub.M−1). The first block of symbols may be obtained by a QPSK digital modulation scheme or any other digital modulation scheme as QAM. M is the number of allocated subcarriers. In such SS-STBC scheme, M is even.

(18) Then, a M-size DFT 2.3, 2.4 (discrete Fourier transform) is applied to each block of symbols X and Y. For each block of symbols, M complex symbols are obtained in the frequency domain, which are respectively custom character and That is for each M-size DFT 2.3, 2.4, one complex symbol is obtained for each k-th subcarrier among the M allocated subcarriers. These complex symbols are mapped, with subcarrier mapping modules 2.5 and 2.6 in the frequency domain to M out of N inputs of N-size IDFT modules, 2.7, 2.8. Regarding the subcarrier mapping, each vector of complex symbols S.sup.Tx1= custom character and S.sup.Tx2= is mapped to the M allocated subcarriers out of N existing subcarriers via subcarrier mapping modules 2.5 and 2.6. The subcarrier mapping can be for example localized, that is the M elements of each vector S.sup.Tx1,2 are mapped to M consecutive subcarriers among the N existing. The subcarrier mapping can be for example distributed, that is the M elements of each vector S.sup.Tx1,2 are mapped equally distanced over the entire bandwidth with zero occupying the unused subcarriers.

(19) Inverse DFT of size N 2.7 and 2.8 are then applied to the two resulting vectors {tilde over (S)}.sup.Tx1 and {tilde over (S)}.sup.Tx2 of the subcarrier mapping modules 2.5 and 2.6, therefore generating two SC-FDMA symbols, each of them being sent at the same time from respectively one of the two transmit antennas. More precisely, at the output of the IDFT modules, 2.7, 2.8 a signal {tilde over (x)}.sup.Tx1=({tilde over (x)}.sup.Tx1.sub.0, . . . , {tilde over (x)}.sup.Tx1.sub.N−1) and a signal {tilde over (x)}.sup.Tx2=({tilde over (x)}.sup.Tx2.sub.0, . . . , {tilde over (x)}.sup.Tx2.sub.N−1), are obtained. Each of these signals occupy during a time interval corresponding to a single-carrier frequency division multiple access, SC-FDMA, symbol, M allocated subcarriers out of the N existing subcarriers. The signals {tilde over (x)}.sup.Tx1 and {tilde over (x)}.sup.Tx2 are time-domain signal whose frequency-domain representations, during a given time interval, are respectively the complex symbols S.sub.k.sup.Tx1 and S.sub.k.sup.Tx2 for each k.sup.th occupied subcarrier with k=0 to M−1. Equivalently, the time-domain signals {tilde over (x)}.sup.Tx1 and {tilde over (x)}.sup.Tx2 during a given time interval represent respectively, in the frequency domain, the complex symbols S.sub.k.sup.Tx1 and S.sub.k.sup.Tx2 for each k.sup.th frequency with k=0 to M−1. These time-domains signals {tilde over (x)}.sup.Tx1 and {tilde over (x)}.sup.Tx2 respectively correspond to SC-FDMA symbols. Therefore, samples in the signal {tilde over (x)}.sup.Tx1 or in the signal {tilde over (x)}.sup.Tx2 refer respectively to samples in a SC-FDMA symbol corresponding to a first transmit antenna 2.0 and to samples in a SC-FDMA symbol corresponding to a second transmit antenna 2.1.

(20) A cyclic prefix can be optionally appended after IDFT.

(21) Referring to FIG. 2.2 there is shown in detail the logical functioning of a SS-STBC pre-coder module 2.2.

(22) The SS-STBC pre-coder 2.2 applied to the block of symbols X=(X.sub.0, . . . X.sub.M−1) (also referred as the first block of symbols) outputs the block of symbols Y=(Y.sub.0, . . . Y.sub.M−1) (also referred as the second block of symbols). Considering the first block of symbols X=(X.sub.0, . . . X.sub.M−1) this one is divided in two parts of M/2 symbols as showed on FIG. 2.2. The first, respectively the second part, contains Q contiguous modulation symbols custom character , respectively contiguous symbol . The Q contiguous modulation symbols of the first part and the second part contain data and reference signals.

(23) To limit the interference between the two parts of the block symbols, the first part may contain a cyclic prefix of P.sub.1 contiguous symbols and/or a cyclic postfix of P.sub.2 contiguous symbols respectively positioned before and after the Q contiguous modulation symbols custom character . The second part may also contain a cyclic prefix of P.sub.1 contiguous symbols and/or a cyclic postfix of P.sub.2 contiguous symbols respectively positioned before and after the Q contiguous modulation symbols . P1 and/or P2 values may also be set to 0, and in that case no prefix and/or no postfix is included.

(24) Therefore, the first block of symbols X=(X.sub.0, . . . X.sub.M−1) can be defined:

(25) X.sub.0=A.sub.Q−P.sub.1, . . . , X.sub.P.sub.1.sub.−1=A.sub.Q−1, for the cyclic prefix of the first part,

(26) X.sub.P.sub.1=A.sub.0, X.sub.P.sub.1.sub.+1=A.sub.1, . . . , X.sub.P.sub.1.sub.+Q−1=A.sub.Q−1, for the data/RS symbols of the first part,

(27) $X_{P_{1} + Q} = A_{0}, .Math., X_{\frac{M}{2} - 1} = A_{P_{2} - 1},$
for the cyclic postfix of the first part,
X.sub.M/2=B.sub.Q−P.sub.1, . . . , X.sub.M/2+P.sub.1.sub.−1=B.sub.Q−1, for the cyclic prefix of the second part, X.sub.P.sub.1.sub.+M/2=B.sub.0, X.sub.P.sub.1.sub.+M/2+1=B.sub.2, . . . , X.sub.M−P.sub.2.sub.−1=B.sub.Q−1, for the data/RS symbols of the second part,
X.sub.M−P.sub.2=B.sub.0, . . . , X.sub.M−1=B.sub.P.sub.2.sub.−1, for the cyclic postfix of the second part.

(28) When applying the SS-STBC pre-coder to the first block of symbols X=(X.sub.0, . . . X.sub.M−1), the second block of symbols Y=(Y.sub.0, . . . Y.sub.M−1) is obtained. This second block of symbols can be defined relatively to the first block of symbols previously defined, as:

(29) Y.sub.0={tilde over (B)}.sub.Q−P.sub.1, . . . , Y.sub.P.sub.1.sub.−1={tilde over (B)}.sub.Q−1, for the cyclic prefix of the first part,

(30) Y.sub.P.sub.1={tilde over (B)}.sub.0, Y.sub.P.sub.1.sub.+1={tilde over (B)}.sub.1, . . . Y.sub.P.sub.1.sub.+Q−1={tilde over (B)}.sub.Q−1, for the data/RS symbols of the first part,

(31) $Y_{P_{1} + Q} = {\tilde{B}}_{0}, .Math., Y_{\frac{M}{2} - 1} = {\tilde{B}}_{P_{2} - 1},$
for the cyclic postfix of the first part,
Y.sub.M/2=−Ã.sub.Q−P.sub.1, . . . , Y.sub.M/2+P.sub.1.sub.−1=−Ã.sub.Q−1, for the cyclic prefix of the second part,
Y.sub.P.sub.1.sub.+M/2=−Ã.sub.0, Y.sub.P.sub.1.sub.+M/2+1=−Ã.sub.2, . . . , Y.sub.M−P.sub.2.sub.−1=−Ã.sub.Q−1, for the data/RS symbols of the second part,
Y.sub.M−P.sub.2=−Ã.sub.0, . . . , Y.sub.M−1=−Ã.sub.P.sub.2.sub.−1, for the cyclic postfix of the second part.
With Ã.sub.n=A*.sub.mod(−n,Q) and {tilde over (B)}.sub.n=B*.sub.mod(−n,Q) and X* is the complex conjugate of X.

(32) Therefore, Y can be defined, regarding the payload data and Reference signal symbols based on X by:

(33) $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + 2 P_{1} + Q - k}^{*}, & for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{\frac{M}{2} + 2 P_{1} + Q - k}^{*}, & for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix}$

(34) With ε the value 1 or −1 When not stated otherwise, in the following we consider ε=1. Indeed, changing the sign (+/−) of the signal related to the second antenna does not change the method.

(35) In the case of the invention the pre-coder is a modified SS-STBC pre-coder which is defined by:

(36) $Y_{k} = {\begin{matrix} .Math. X_{\frac{M}{2} + P_{1} + \mod (- k + P_{1} + p - 1, Q)}^{*}, & for k \in 〚 P_{1}; \frac{M}{2} - P_{2} 〚 \\ - .Math. X_{P_{1} + \mod (- k + P_{1} + \frac{M}{2} + p - 1, Q)}^{*}, & for k \in 〚 \frac{M}{2} + P_{1}; M - P_{2} 〚 \end{matrix}$

(37) That is when applying the SS-STBC modified pre-coder to the first block of symbols X=(X.sub.0, . . . X.sub.M−1), the second block of symbols Y=(Y.sub.0, . . . Y.sub.M−1) can be defined relatively to the first block, as:

(38) Y.sub.0={tilde over (B)}.sub.Q−P.sub.1, . . . , Y.sub.P.sub.1.sub.−1={tilde over (B)}.sub.Q−1, for the cyclic prefix of the first part,

(39) Y.sub.P.sub.1={tilde over (B)}.sub.0, Y.sub.P.sub.1.sub.+1={tilde over (B)}.sub.1, . . . , Y.sub.P.sub.1.sub.+Q−1={tilde over (B)}.sub.Q−1, for the data/RS symbols of the first part,

(40) $Y_{P_{1} + Q} = {\tilde{B}}_{0}, .Math., Y_{\frac{M}{2} - 1} = {\tilde{B}}_{P_{2} - 1},$
for the cyclic postfix of the first part,
Y.sub.M/2=−Á.sub.Q−P.sub.1, . . . , Y.sub.M/2+P.sub.1.sub.−1=−Á.sub.Q−1, for the cyclic prefix of the second part,
Y.sub.P.sub.1.sub.+M/2=−Ã.sub.0, Y.sub.P.sub.1.sub.+M/2+1=−Ã.sub.2, . . . , Y.sub.M−P.sub.2.sub.−1=−Ã.sub.Q−1, for the data/RS symbols of the second part,
Y.sub.M−P.sub.2=−Ã.sub.0, . . . , Y.sub.M−1=−Ã.sub.P.sub.2.sub.−1, for the cyclic postfix of the second part.

(41) With Ã.sub.n=A*.sub.mod(−n+p−1,Q) and {tilde over (B)}.sub.n=B*.sub.mod(−n+p−1,Q).

(42) Such a SS-STBC modified pre-coder enables to have more flexibility in the applied scheme.

(43) Referring to FIG. 3, there is shown a block diagram of a classical SS-STBC receiver. Such a receiver is configured to decode a radio signal emitted by a SS-STBC transmitter. This example shows 2 receive antennas but such receiver can have only one antenna (MISO) or a several antennas (MIMO). In this example said radio signal is received on two antennas Rx1 3.1 and Rx2 3.2. The radio signal received by each antennas differs, and the more the two antennas are spaced from each other the more the radio signal received on each antennas is likely to be different, which introduces receive diversity. After an optional guard removal the resulting signals Rx1 and Rx2 are inputted into two N-size DFT (3.3 and 3.4) and then in subcarriers de-mapping modules (3.5 and 3.6), one associated to Rx1 3.1 one associated with Rx2 3.2.

(44) The result in the frequency domain is two vectors T.sup.Rx1 and T.sup.Rx2. Before inputting T.sup.Rx1 and T.sup.Rx2 in the SS-STBC decoder 3.7, the SS-STBC decoder 3.7 can be adjusted based on the channel estimation (made by a channel estimation module 3.8), channel estimation which is computed for example on the basis of received DMRS (demodulation reference signal). Afterwards, the T.sup.Rx1 and T.sup.Rx2 are inputted in the SS-STBC decoder 3.7 which outputs a block Z of M symbols (Z.sub.0, . . . Z.sub.M−1) in the time domain. Additional modification may be performed at the output of the SS-STBC decoder 3.7 to obtain the block of symbols Z, for example constellation de-mapping and error correction, enables estimating the digital data at the origin of X.

(45) If reference signals are pre-DFT inserted in random position and multiplexed with the data modulation symbols at the DFT input, the samples of the reference signals received cannot be extracted from the received signal and processed before obtaining at first the block of symbols Z at the output of the SS-STBC decoder 3.7. Therefore, the SS-STBC decoder 3.7 will decode T.sup.Rx1 and T.sup.Rx2 without taking into account the information conveyed by the reference signals, which can lead to strongly degraded performance of the SS-STBC decoder 3.7.

(46) Referring to FIG. 4.1, there is shown a block diagram of Pre-DFT insertion of reference signals according to the invention. Regarding the transmitter, the scheme applied is the modified SS-STBC scheme described in FIGS. 2.1 and 2.2.

(47) Therefore, a modified SS-STBC pre-coder 4.2 (simply referenced below as a SS-STBC pre-coder), M-size DFTs 4.3 and 4.4, subcarrier mapping modules 4.5 and 4.6 and N size IDFT modules 4.7 and 4.8 are successively applied to the block of symbols X=(X.sub.0, . . . X.sub.M−1) to obtain the radio signal emitted by Tx1 4.0 and Tx2 4.1.

(48) In this embodiment, reference signal are inserted pre-DFT, that is by setting values of the symbols X.sub.n which are chosen to be reference signals. Therefore, when inserting 4K reference signals, K being a positive integer smaller or equal to M/2 (it may be set strictly smaller than M/2 to avoid the block of symbols X to be a full block of reference signals), L integers n.sub.i are to be determined such as

(49) ${n_{i} | i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}}$

(50) Then reference signals (RSs) are inserted directly in the block of symbol X at the positions n.sub.i and

(51) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q) .$
The RS insertion module 4.9 inserts the reference signals by setting each value of the symbols X.sub.n which are at positions n.sub.i or n.sub.i+M/2 with i∈ custom character 1;L at a value of a reference signal. The RS insertion module 4.9 may be configured in a static way by previously configuring the positions n.sub.i or

(52) 0 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
with i∈ custom character 1;L. Several configurations may also be previously programmed, for example one configuration for each number K, or a limited number of configurations for each number K. Exact values of K and (n.sub.i) can be either fixed, or configurable. Configuration can be done in an implicit manner (based on other parameters known by the transmitter), or in an explicit manner (based on instructions that the receiver is returning to the transmitter via, e.g., a control channel), or a combination of the two. The Data modulator module 4.10 may be configured to insert modulation symbols into the block of symbols in positions that not conflict with the positions n.sub.i or

(53) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
with i∈ custom character 1;L of the reference signals. The RS insertion module 4.9 may inform the Data modulator module 4.10 of the chosen configuration. Regarding the implementation described in FIG. 2, only 2Q symbols are used, the symbols in the two cyclic prefix parts and in the two cyclic suffix parts are defined based on the used symbols. Therefore, only L pairs of symbols are defined here, the remaining K−L pairs being defined by the L pairs. Thus, L is smaller or equal to min(M/2−P.sub.1−P.sub.2; K) (it may be set smaller or equal to min(M/2−P.sub.1−P.sub.2−1; K) to avoid the block of symbols X to be a full block of reference signals).

(54) Positions

(55) ${n_{i} .Math. i \in 〚 1; L 〛, P_{1} \leq n_{i} < \frac{M}{2} - P_{2}, \forall i, j \in {〚 1; L 〛}^{2}, i < j .Math. n_{i} < n_{j}}$
can be advantageously chosen. For example, the RS insertion module 4.9 may be configured with the positions n.sub.i consecutive, that is with n.sub.L−n.sub.1=L−1. Grouping the RS on consecutive positions enables to reduce the interference suffered by the RS from other symbols in the radio signal.

(56) In another example, the positions {n.sub.i|i∈ custom character 1;L} of the RS can be divided in groups of consecutive positions. That is for example, 3 groups of RS of consecutive positions n.sub.1 to n.sub.k′.sub.1, n.sub.k.sub.2(n.sub.k.sub.2>n.sub.k′.sub.1) to n.sub.k′.sub.2 and n.sub.k.sub.3 (n.sub.k.sub.3>n.sub.k′.sub.2) to n.sub.L, where n.sub.k′.sub.1−n.sub.1=k′.sub.1−1, n.sub.k′.sub.2−n.sub.k.sub.2=k′.sub.2−k.sub.2 and n.sub.L−n.sub.k.sub.3=L−k.sub.3. Having several groups which are separated by other symbols in the block of symbols X, enables to track fast phase variations at a lower level than the time duration of a block of symbols.

(57) Regarding the values of the symbols X.sub.n.sub.i and

(58) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L, that is the symbols of X positioned at n.sub.i and

(59) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
for i∈ custom character 1;L, they may be set as components of a CAZAC sequence. More specifically the values of the symbols X.sub.n.sub.i with i∈1;L can be derived from values of a first CAZAC sequence and/or the values of the symbols

(60) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L can be derived from values of a second CAZAC sequence. It can be advantageous to select the second CAZAC sequence such that symbols Y.sub.n.sub.i, with {n.sub.i|i∈1;L} are components of a CAZAC sequence, orthogonal to the first one.

(61) The CAZAC sequences may be for example Zadoff-Chu sequences. That is for example with the values of X.sub.n.sub.i with i∈ custom character 1;L, can be set to the values of a CAZAC sequence of length L, or can be obtained by truncating a CAZAC sequence of length superior to L, or can be obtained by cyclic extension from a CAZAC sequence of length inferior to L.

(62) It is advantageous to set values for X.sub.n.sub.i and

(63) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L, such as the maximum absolute values modules are equal or smaller than the maximum absolute values of the modulation symbols of the digital modulation scheme used for modulation. For example, the digital modulation scheme can be QPSK (quadrature phase-shift keying) or other PSK (phase-shift keying) whose values are all of module equal to 1, in this example the values of |X.sub.n.sub.i| and

(64) $.Math. X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)} .Math.$
are chosen as to be smaller or equal to 1.

(65) Referring to FIG. 4.2, there is shown a block diagram of post pre-coder insertion of reference signals according to the invention. Regarding the transmitter, the scheme applied is the modified SS-STBC scheme described in FIG. 2.1, 2.2.

(66) Therefore, a modified SS-STBC pre-coder 4.2 (simply referenced below as a SS-STBC pre-coder), M-size DFTs 4.3 and 4.4, subcarrier mapping modules 4.5 and 4.6 and N size IDFT modules 4.7 and 4.8 are successively applied to the block of symbols X=(X.sub.0, . . . X.sub.M−1) to obtain the radio signal emitted by Tx1 4.0 and Tx2 4.1.

(67) In this embodiment, reference signal are inserted post pre-coder, that is by setting values of the symbols X.sub.n and Y.sub.n which are chosen to be reference signals. For this, the data modulator module 4.12 is configured to set the values of the symbols X.sub.n.sub.i and

(68) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L to 0. The configuration of the data modulator module 4.12 may be made by the RS insertion module 4.11 which can send the position configuration to the data modulator module 4.12. On this incomplete block of symbols X.sub.DATA, a SS-STBC pre-coder 4.2 is applied to obtain a block of symbols Y.sub.DATA=(Y.sub.n). Then the reference signals (RSs) are inserted directly in those two blocks of symbols, the first and second block of symbols X.sub.DATA and Y.sub.DATA at the positions n; and

(69) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q) .$
For each quadruplet i∈ custom character 1;L of reference signals, the RS insertion module 4.11 inserts the reference signals by setting the values of the symbols X.sub.n.sub.i,

(70) 0 $X_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(71) $Y_{\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
to values representing the first, second, fourth and respectively third reference signals. In this configuration each value of the reference signals of a given quadruplet of reference signals can be set independently. Therefore, only the time periods of the samples of each reference signal in the same quadruplet depends on the other reference signals of the quadruplet.

(72) The RS insertion module 4.11 may be configured in a static way by previously configuring the positions n.sub.i or

(73) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
with i∈ custom character 1;L. Several configurations may also be previously programmed, for example one configuration for each number K or a limited number of configurations for each number K. Exact values of K and (n.sub.i).sub.i can be either fixed, or configurable. Configuration can be done in an implicit manner (based on other parameters known by the transmitter), or in an explicit manner (based on instructions that the receiver is returning to the transmitter via, e.g., a control channel). The Data modulator module 4.12 may be configured to insert modulation symbols into the block of symbols in positions that do not conflict with the positions n.sub.i or

(74) $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
with i∈ custom character 1;L of the reference signals. The RS insertion module 4.11 may inform the Data modulator module 4.12 of the chosen configuration. Regarding the implementation described in FIG. 2.1, only 2Q symbols are used, the symbols in the two cyclic prefix parts and in the two cyclic suffix parts are defined based on the used symbols. Therefore, only L quadruplets of symbols are defined here the remaining K−L quadruplets being defined by the L quadruplets. Thus, L is smaller or equal to min(M/2−P.sub.1−P.sub.2; K) (it may be set smaller or equal to min(M/2−P.sub.1−P.sub.2−1; K) to avoid the block of symbols X to be a full block of reference signals).

(75) Once the reference signal inserted the SC-FDMA schemes are applied on each block of symbols (first and second block of symbols) to obtain a first and second SC-FDMA symbol which are transmitted through the emitted radio signal.

(76) In the embodiment of the FIG. 4.2, where the reference signals are inserted post pre-coder, the first and second SC-FDMA symbols obtained are the same or equivalent to the ones obtained when inserting the reference signals in a pre-DFT manner. Therefore, all the features shown in relation with pre-DFT insertion can be applied to post pre-coder insertion.

(77) For example, the positions advantageously chosen in pre-DFT insertion can be applied, by setting to 0 the symbols at those positions and then inserting post pre-coder the reference signals in those positions.

(78) In the embodiments that set the values of the symbols X.sub.n.sub.i and

(79) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L, these embodiments can be applied in the case of post pre-coder insertion, by setting the values of the symbols X.sub.n.sub.i and

(80) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
with i∈ custom character 1;L to the values at would have been set for the symbols X.sub.n.sub.i and

(81) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
if they were set pre-DFT, and setting the values of the symbols Y.sub.n.sub.i and

(82) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
to values according to the transformation operated by the SS-STBC.

(83) In addition, even if the values in the second block of symbols of the third and fourth reference signals are chosen independently than the values in the first block of symbols of the first and second reference signals these embodiments can still be applied. Indeed, the positions are identical between the two embodiments. Therefore, the specific position described can be reproduced in this embodiment.

(84) Regarding the values of the symbols X.sub.n.sub.i,

(85) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(86) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L they may be set as components of a CAZAC sequence. Each value of the reference signals in a same quadruplet can be derived from different CAZAC sequences or from the same CAZAC sequence. The CAZAC sequences may be for example Zadoff-Chu sequences.

(87) The values of the symbols X.sub.n.sub.i,

(88) 0 $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(89) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
may also be set to have the values of X.sub.n.sub.i and Y.sub.n.sub.i respectively

(90) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)} and Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
equal. In addition, it is also possible to set these values to have the values of X.sub.n.sub.i and

(91) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
equal.

(92) It is advantageous to set values for X.sub.n.sub.i,

(93) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(94) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L, such as the maximum absolute values modules are equal or smaller than the maximum absolute values of the modulation symbols of the digital modulation scheme used for modulation. For example, the digital modulation scheme can be QPSK (quadrature phase-shift keying) or other PSK (phase-shift keying) whose values are all of module equal to 1, in this example the values of |X.sub.n.sub.i|,

(95) $.Math. X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)} .Math.,$
|Y.sub.n.sub.i| and

(96) $.Math. Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)} .Math.$
are chosen as to be smaller or equal to 1.

(97) Referring to FIG. 4.3, there is shown a block diagram of post-IDFT insertion of reference signals according to the invention. In this embodiment, the reference signals are not inserted pre-DFT (that is by setting the values of the symbols X.sub.n.sub.i and

(98) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L, to non-null values known by the receiver as shown in FIG. 4.1). The insertion of the reference signals is done post IDFT. For this, the data modulator module 4.14 is configured to set the values of the symbols X.sub.n.sub.i and

(99) $X_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L to 0 before applying the modified SS-STBC pre-coder 4.2. The configuration of the data modulator module 4.14 may be made by the RS insertion module 4.13 which can send the position configuration to the data modulator module 4.14. On this incomplete block of symbols X.sub.DATA, the SS-STBC scheme as in the embodiment of FIG. 4.1 is applied, starting by the SS-STBC pre-coder 4.2, the M-size DFTs 4.3 and 4.4. At the respective IDFT outputs subsequent signals are obtained, that is {tilde over (x)}.sub.DATA.sup.Tx1 at the output of the IDFT module 4.7 corresponding to the antenna Tx1 and {tilde over (x)}.sub.DATA.sup.Tx2 at the output of the IDFT module 4.8 corresponding to the antenna Tx2. The RS insertion module 4.13 adds respectively to each of the output signals of the IDFT modules (4.7 and 4.8), which are {tilde over (x)}.sub.DATA.sup.Tx1 corresponding to the antenna Tx1 and {tilde over (x)}.sub.DATA.sup.Tx2 corresponding to the antenna Tx2, the signals {tilde over (x)}.sub.DATA.sup.Tx1 and the signal {tilde over (x)}.sub.DATA.sup.Tx2 respectively. The signal {tilde over (x)}.sub.DATA.sup.Tx1 and {tilde over (x)}.sub.DATA.sup.Tx2 are pre-computed samples of the corresponding, symbols X.sub.n.sub.i,

(100) 0 $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(101) $Y_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L. That is rather than setting the post pre-coder values of the symbols X.sub.n.sub.i,

(102) $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(103) $Y_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L in the first and second block of symbols (X and Y), the samples of the reference signals are previously computed to obtain samples identical or at least equivalent to those that would have been obtain, at the output of the IDFT, for example by setting the values (post pre-coder) of the symbols X.sub.n.sub.i,

(104) $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(105) $Y_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L to non-null values known by the receiver, as previously described. For example, {tilde over (x)}.sub.DATA.sup.Tx1 can be obtained by applying SC-FDMA schemes to a first block of symbols where the values of the symbols X.sub.n.sub.i and

(106) $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L are set respectively to the values representing the first and second reference signals and setting the values of the other symbols to 0 (that is by not introducing other symbols). {tilde over (x)}.sub.RS.sup.Tx2 can be obtained by applying SC-FDMA schemes to a second block of symbols where the values of the symbols Y.sub.n.sub.i and

(107) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)}$
with i∈ custom character 1;L are set respectively to the values representing the fourth and third reference signals and setting the values of the other symbols to 0 (that is by not introducing other symbols).

(108) In the embodiments of the FIG. 4.3 where the reference signals are inserted post-IDFT the signals obtained at the output of the adders, {tilde over (x)}.sup.Tx1 and {tilde over (x)}.sup.Tx2, are equivalent to the signals at the outputs of the IDFT modules when post pre-coder inserting the reference signals. Therefore, all the features shown in relation with post pre-coder insertion or pre-DFT insertion can be applied to post-IDFT insertion.

(109) Before adding the signal {tilde over (x)}.sub.RS.sup.Tx1 and the signal {tilde over (x)}.sub.RS.sup.Tx2, it is advantageous to filter the signals {tilde over (x)}.sub.DATA.sup.Tx1 and {tilde over (x)}.sub.DATA.sup.Tx2 to ensure that the samples in the signal {tilde over (x)}.sub.DATA.sup.Tx1 and the signal {tilde over (x)}.sub.DATA.sup.Tx2 of the corresponding symbols X.sub.n.sub.i,

(110) $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(111) $Y_{(\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)},$
whose values have been set to 0, are also strictly equal to 0 for the time periods in which are inserted the samples of the reference signal or at least time periods in which are inserted the parts of the samples of high energy. Therefore, this enables to reduce the interference of signals {tilde over (x)}.sub.DATA.sup.Tx1 and {tilde over (x)}.sub.DATA.sup.Tx2 onto at least the high energy part of signals {tilde over (x)}.sub.RS.sup.Tx1 and {tilde over (x)}.sub.RS.sup.Tx2.

(112) Referring to FIG. 5, there is shown a block diagram of reference signals extraction according to the invention. The radio signal emitted according to the previous embodiments is received by the receiver 1.2, after having crossed a multipath channel and suffered noise and phase noise effects. The receiver can receive the radio signal on one antenna, which is the case in MISO telecommunication system, or on several antennas Rx1, Rx2 as shown in FIG. 5.

(113) After the Analogue to Digital converters (ADC) have been applied to the radio signal received by each antenna, the reference signals are extracted. In a variant, reference signals can be extracted after CP removal. Here, by reference signal extraction we understand separating time domain portions of the received radio signal containing part or all of the information relative to the sent reference signals, corrupted by the channel and the noise/phase noise during the transmission process.

(114) As previously explained this is possible since, in the time domain, samples in the radio signal of the reference signals are superposed, and no parts of high energy samples corresponding to non-reference signals symbols are emitted at the same time of the high energy superposed samples of the reference signals.

(115) Therefore, by extracting the parts of the signals outputted by the ADCs 5.2.1 and 5.2.2 during the time periods dependent to the position n.sub.i (which are the same than time periods dependent to the position

(116) 0 $\frac{M}{2} + P_{1} + \mod (- n_{i} + P_{1} + p - 1, Q)$
due to the SS-STBC pre-coder scheme), the received samples corresponding to the symbols X.sub.n.sub.i,

(117) $X_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(118) $Y_{(\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)}$
are extracted. It is advantageous to take into account only the time periods corresponding to parts of the samples with high energy to avoid extracting unusable samples. These time periods depend on the type of subcarrier mapping that is implemented. For example a localized or a distributed implementation give completely different time periods.

(119) Each type of subcarrier mapping has its own distribution, across the time domain, of the samples in the radio signal. These distribution are well known by the person skilled in the art and shown in the literature (for example: Cf. reference Hyung G. Myung Single Carrier Orthogonal Multiple Access Technique for Broadband Wireless Communications Ph.D. Thesis Defense|2006 Dec. 18) which can easily transpose the teaching of the invention to other subcarrier mapping, thus the invention is not limited to a specific subcarrier mapping.

(120) The extractor 5.8 may be configured to apply time-domain windows for extracting the reference signals according to the time periods of the received samples of the reference signals inserted (pre-DFT, post pre-decoder or post-DFT). A first configuration is to apply time domain windows, each window being equal to one time period among the time periods corresponding to the receiving of the samples of the reference signals (that is the time periods of the received samples of the reference signals). The sizes of the windows may as well slightly exceed the size of the windows of the first configuration each window being positioned to include a window of the first configuration. This enables to extract a slightly wider part of the received samples corresponding to the reference signals which is advantageous when the receiver 1.2 is capable of interference mitigation. The size of the windows may be taken slightly smaller than the size of the windows of the first configuration and each window may be positioned to be included in a window of the first configuration, enabling to limit the extraction of the received samples of non-reference signals which may cause interference with the samples of the reference signal, which is advantageous when the receiver 1.2 is of low performance regarding interference mitigation.

(121) Once the received samples of the reference signals are extracted by the extractor 5.8 they may be time domain or frequency domain processed. The processing of the samples of the reference signals is a common processing well known by the person skilled in the art. For example, reference signals can serve as base for channel estimation through known channel estimation methods applied in the time or in the frequency domain. For example, reference signals can serve to improve the quality of a channel estimate acquired based on other dedicated reference signals (e.g. dedicated SC-FDMA symbols carrying only reference symbols such as DMRS). Once the received samples of the reference signals are processed, the channel estimation module 5.9 can compare these reference signals with reference values, as part of the channel estimation process.

(122) The channel estimation may also result from a classical implementation with dedicated DMRS (demodulation reference signal) which occupy a full block of symbols, in this case the reference signal according to the invention can be used to improve the channel estimation quality.

(123) Once the channel estimation module 5.9 calculated the estimated channel, the SS-STBC decoder 5.7 may be set to compensate the corruption (phase shift, amplitude . . . ) of the signal in the channel between transmitter and receiver. Enabling to enhance the performance of the processing to obtain the block of symbols Z=(Z.sub.0, . . . Z.sub.M−1).

(124) The extractor 5.8 can also be placed after the guard removal modules.

(125) Referring to FIG. 6.1 there is shown a flowchart representing the steps of pre-DFT inserting reference signals in a radio signal according to the invention.

(126) At step S11 the RS insertion module 4.9 is configured either in a static way or dynamically (that is that the RS insertion module 4.9 is reconfigured depending for example on a feedback from the receiver through a control channel), or by a combination of the two. In the case of a dynamic configuration the RS insertion module 4.9 may choose another configuration upon those saved in the MEMO_trans 1.5. Indeed, several configurations may be pre-parametered in the RS insertion module 4.9, those configurations can be ordered according to the number of reference signals the configuration provides. A configuration may be defined by the number of quadruplets of reference signals K or L, by the positions n; in the block of symbols X of the symbols X.sub.n.sub.i to which corresponds the different reference signals to be inserted.

(127) RS insertion module 4.9 may inform the Data modulator module 4.10 of the chosen configuration. Enabling the Data modulator module 4.10 to insert modulation symbols into the block of symbols in positions that do not conflict with the positions n.sub.i or n.sub.i+M/2 with i∈ custom character 1;L of the reference signals.

(128) At step S12 the RS insertion module 4.9, inserts the reference signals as previously described, by setting each value of the symbols X.sub.n which are at positions n.sub.i or n.sub.i+M/2 with i∈ custom character 1;L at a value of a reference signal.

(129) At step S13 the signal is processed, that is on the block of symbols X=(X.sub.0, . . . X.sub.M−1) is applied the modified SS-STBC scheme (SS-STBC pre-coder 4.2, DFT modules 4.3 and 4.4, subcarrier mapping modules 4.5 and 4.6, IDFT modules 4.7 and 4.8).

(130) At step S14 the signal is emitted by Tx1 4.0 and Tx2 4.1.

(131) Referring to FIG. 6.2 there is shown a flowchart representing the steps of post pre-coder inserting reference signals in a radio signal according to the invention.

(132) At step S21 the RS insertion module 4.11 may be configured in a static way or dynamically as in FIG. 6.1 (or by a combination of the two). Several configurations may also be pre-parametered in the RS insertion module 4.11, those configurations can be ordered according to the number of reference signals the configuration provides. A configuration may be defined by the number of quadruplets of reference signals K, by the positions n.sub.i in the blocks of symbols X and Y in which the different reference signals are inserted. When configured, the RS insertion module 4.11 may inform the Data modulator module 4.12 of the configuration chosen.

(133) At step S22, based on the configuration of the RS insertion module 4.11, the Data modulator module 4.12 sets the values of the symbols X.sub.n.sub.i and X.sub.(n.sub.i.sub.+M/2) with i∈ custom character 1;L to 0, as previously described in FIG. 4.2.

(134) At step S23, the SS-STBC pre-coder 4.2 is applied on the incomplete block of symbols X.sub.DATA, as previously explained in FIG. 4.2.

(135) At step S24 the RS insertion module 4.11 inserts the reference signals by setting the values of the symbols X.sub.n.sub.i,

(136) $X_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
Y.sub.n.sub.i and

(137) $Y_{\frac{M}{2} + P_{1} + m o d (- n_{i} + P_{1} + p - 1, Q)},$
of the incomplete block of symbols X.sub.DATA and of the block of symbols Y.sub.DATA obtained at the output of the pre-coder 4.2, to values representing the first, second, fourth and third reference signals respectively.

(138) At step S25 the signal is processed, that is on each of the blocks of symbols X and Y, to which the reference signals have been inserted, the SC-FDMA scheme is applied (DFT modules 4.3 and 4.4, subcarrier mapping modules 4.5 and 4.6, IDFT modules 4.7 and 4.8) is applied.

(139) At step S26 the signal is emitted by Tx1 4.0 and Tx2 4.1.

(140) Referring to FIG. 6.3 there is shown a flowchart representing the steps of post-IDFT inserting reference signals in a radio signal according to the invention.

(141) At step S31 the RS insertion module 4.13 may also be configured in a static way or dynamically as in FIG. 5.1 (or by a combination of the two). Several configurations may also be pre-parametered in the RS insertion module 4.13, those configurations can be ordered according to the number of reference signals the configuration provides. A configuration may be defined by the number of quadruplets of reference signals K, by the positions n, in the block of symbols X in which the different reference signals are inserted. When configured, the RS insertion module 4.13 may inform the Data modulator module 4.14 of the configuration chosen.

(142) At step S32, based on the configuration of the RS insertion module 4.13, the Data modulator module 4.14 sets the values of the symbols X.sub.n.sub.i and X.sub.(n.sub.i.sub.+M/2) with i∈ custom character 1;L to 0, as previously described in FIG. 4.3.

(143) At step S33 the signal is processed, that is on the block of symbols X=(X.sub.0, . . . X.sub.M−1), to which the values of the symbols X.sub.n.sub.i and X.sub.(n.sub.i.sub.+M/2) with i∈ custom character 1;L have been set to 0, is applied a SS-STBC type scheme (SS-STBC pre-coder 4.2, DFT modules 4.3 and 4.4, subcarrier mapping modules 4.5 and 4.6, IDFT modules 4.7 and 4.8).

(144) At step S34 the RS insertion module 4.13 adds respectively to each of the output signals of the IDFT modules (4.7 and 4.8), which are {tilde over (x)}.sub.DATA.sup.Tx1 corresponding to the antenna Tx1 4.0 and {tilde over (x)}.sub.DATA.sup.Tx2 corresponding to the antenna Tx2 4.1, the signal {tilde over (x)}.sub.RS.sup.Tx1 and the signal {tilde over (x)}.sub.RS.sup.Tx2. The signal {tilde over (x)}.sub.RS.sup.Tx1 and {tilde over (x)}.sub.RS.sup.Tx2 may be computed as previously mentioned in FIG. 4.3.

(145) At step S35 the signal is emitted by Tx1 4.0 and Tx2 4.1.

(146) Referring to FIG. 7 there is shown a flowchart representing the steps of extracting reference signals in the radio signal according to the invention.

(147) At step S71 the extractor 5.8 is configured according to the configuration of the RS insertion module (4.9, 4.11 or 4.13). The same configurations pre-parametered in the RS insertion module (4.9, 4.11 or 4.13) may be pre-parametered in the extractor 5.8. The transmitter 1.1 can optionally send control information to the receiver 1.2 through a control channel, this control information pointing the configuration to set for extracting the reference signal being sent by the transmitter.

(148) At step S72 the extractor 5.8 extracts parts of the signals outputted by the ADCs 5.2.1 and 5.2.2 during the time periods corresponding with the received samples of the reference signals. The extraction is conduct as described in FIG. 5.

(149) At step S73 the samples of the reference signals are processed as previously described.

(150) At step S74 the channel estimation module 5.9 compares these reference signals with reference values, that is the corresponding values of the emitted samples of the reference signals, to obtain a channel estimation quality. The channel estimation module 5.9 may also specify a previously obtained channel estimation quality.

(151) At step S75 the signal received is then processed, using the channel estimation quality to enhance the performance of the processing. For example the SS-STBC decoder 5.7 may be set to compensate the corruption (phase shift, amplitude . . . ) of the signal in the channel between transmitter and receiver.

Device and method for inserting quadruplet and device and method for extracting quadruplet

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