Method of reducing the peak-to-average power ratio of a fourier transform-generated multi-carrier signal in transmission systems

1. A method of reducing the peak-to-average power ratio of a multi-carrier signal in transmitter/receiver systems, the method comprising:

providing a digital signal to be transmitted;

subjecting the digital signal to be transmitted to a Fourier transform operation to obtain a modulated signal;

generating an anti-peak signal comprising a pulse train through time, a shape of a base pulse of said pulse train being defined and known at a receiver;

summing said anti-peak signal with said modulated signal in order to obtain a summed signal; and

transmitting the summed signal and auxiliary information to enable demodulation of the summed signal as soon as the summed signal is received,

wherein the step of summing said anti-peak signal with said modulated signal comprises summing said pulse train in phase opposition with respect to the original digital signal if the original signal exhibits peaks exceeding a certain value, and

wherein the step of generating the anti-peak signal comprises generating a pulse train in which the base pulse has a Gaussian-type shape with a width at 3 dB comparable with a distance between samples of the original digital signal and an amplitude on an order of one half of a maximum amplitude of the original digital signal.

2. The method according to claim 1 , wherein said step of generating said anti-peak signal comprises generating a signal composed of a base pulse train, the shape of the base pulse being defined and known at the receiver side, and wherein the step of transmitting said auxiliary information comprises transmitting information concerning the position of the base pulses inside the symbol and their sign.

3. The method according to claim 1 , wherein said step of generating said anti-peak signal comprises generating a signal composed of a base pulse train, the shape of the base pulse being defined and known at a receiver side, the number of pulses generated for each symbol being also defined and known at the receive side, and wherein the step of transmitting auxiliary information comprises transmitting information in a fixed amount.

4. The method according to claim 1 , wherein the step of generating the anti-peak signal further comprises establishing the pulse position as a function of a signal modulus and applying separately the correction on the in-phase and quadrature components of the original signal, choosing the sign for each of them so that it is in phase opposition over each of them.

5. The method according to claim 1 , wherein the step of transmitting auxiliary information comprises transmitting said auxiliary information concerning a symbol together with the next symbol.

6. The method according to claim 1 , further comprising:

receiving the summed signal;

extracting from said summed signal some the auxiliary information and reconstructing the anti-peak signal;

subjecting said summed signal to a Fourier transform thus obtaining a demodulated signal; and

subtracting the anti-peak signal from said demodulated signal to obtain the original signal.

7. The method according to claim 6 , wherein the step of subtracting the anti-peak signal from said demodulated signal comprises subtracting the auxiliary information concerning the preceding symbol with respect to the received one to obtain the original signal related to the preceding symbol.

8. A transmitter for transmitting a multi-carrier signal while reducing the peak-to-average power ratio, the transmitter comprising:

means for receiving a digital signal to be transmitted;

means for subjecting the digital signal to be transmitted to a Fourier transform operation to obtain a modulated signal;

means for generating an anti-peak signal comprising a pulse train through time, the shape of a base pulse of said pulse train being defined and known at a receiver;

means for summing said anti-peak signal with said modulated signal to generate a summed signal; and

means for transmitting the summed signal and auxiliary information to enable demodulation of the transmitted signal as soon as the transmitted signal is received,

wherein the means for summing said anti-peak signal with said modulated signal sum said pulse train in phase opposition with respect to the original digital signal if the original signal exhibits peaks exceeding a certain value, and

wherein said means for generating said anti-peak signal comprise a pulse generator for generating a pulse train in which the base pulse has a Gaussian-type shape with a width at 3 dB comparable with a distance between samples of the original digital signal and an amplitude on an order of one half of a maximum amplitude of the original digital signal.

9. The transmitter according to claim 8 , further comprising storage means for temporarily storing the signals outputting from the means performing the Fourier transform.

10. A method of reducing the peak-to-average power ratio of a multi-carrier signal in transmitter/receiver systems, the method comprising:

providing a digital signal to be transmitted;

subjecting the digital signal to be transmitted to a Fourier transform operation to obtain a modulated signal;

generating an anti-peak signal comprising a pulse train through time, a shape of a base pulse of said pulse train being defined and known at a receiver;

summing said anti-peak signal with said modulated signal in order to obtain a summed signal; and

transmitting the summed signal and auxiliary information to enable demodulation of the summed signal as soon as the summed signal is received,

wherein the step of generating the anti-peak signal comprises generating a pulse train comprising a number of base pulses, with each base pulse having a Gaussian-type shape, and

wherein the step of generating the anti-peak signal further comprises establishing the pulse position as a function of a signal modulus and applying separately the correction on the in-phase and quadrature components of the original digital signal, choosing the sign for each of them so that it is in phase opposition over each of them.

11. The method according to claim 10 , wherein the step of summing said anti-peak signal with said modulated signal comprises summing said pulse train in phase opposition with respect to the original signal if the original signal exhibits peaks exceeding a certain value.

12. The method according to claim 10 , wherein said step of generating said anti-peak signal comprises generating a signal composed of a base pulse train, the shape of the base pulse being defined and known at the receiver side, and wherein the step of transmitting said auxiliary information comprises transmitting information concerning the position of the base pulses inside the symbol and their sign.

13. The method according to claim 10 , wherein said step of generating said anti-peak signal comprises generating a signal composed of a base pulse train, the shape of the base pulse being defined and known at a receiver side, the number of pulses generated for each symbol being also defined and known at the receive side, and wherein the step of transmitting auxiliary information comprises transmitting information in a fixed amount.

14. The method according to claim 10 , wherein the step of transmitting auxiliary information comprises transmitting said auxiliary information concerning a symbol together with the next symbol.

15. The method according to claim 10 , further comprising:

receiving the summed signal;

extracting from said summed signal some the auxiliary information and reconstructing the anti-peak signal;

subjecting said summed signal to a Fourier transform thus obtaining a demodulated signal; and

subtracting the anti-peak signal from said demodulated signal to obtain the original signal.

16. The method according to claim 15 , wherein the step of subtracting the anti-peak signal from said demodulated signal comprises subtracting the auxiliary information concerning the preceding symbol with respect to the received one to obtain the original signal related to the preceding symbol.

17. The method according to claim 10 , wherein said Gaussian-type shape of said base pulse has a width at 3 db which is comparable with the distance between the samples and an amplitude on the order of one half of the maximum amplitude.

18. The method according to claim 10 , wherein a number K of pulses generated for each signal is fixed in advance and wherein said auxiliary information is in a fixed number of bits equal to K (log N+2), wherein N is a number of subcarriers.