Reduction of peak-to-average ratio in OFDM systems

1. A method for modulating and emitting an orthogonal frequency division multiplexing, OFDM, signal through a transmission channel, the method comprising:

performing a first frequency-to-time conversion of input frequency symbols to generate first time symbols;

clipping said first time symbols using a clipping level selected to optimize amplification yielding the OFDM signal to be transmitted;

performing a time-to-frequency conversion of the clipped first time symbols, to obtain frequency symbols;

performing a second frequency-to-time conversion of said frequency symbols for a set of subcarriers in said transmission channel, to generate second time symbols; and

serializing and amplifying said second time symbols to be emitted as the OFDM signal through said transmission channel,

wherein said first frequency-to-time conversion and said second frequency-to-time conversion are performed using a same frequency-to-time converter.

2. The method according to claim 1 , wherein said set of subcarriers corresponds to data subcarriers.

3. The method according to claim 1 , wherein out-of-band subcarriers other than said set of subcarriers are set to zero before being applied as input of the second frequency-to-time conversion, outside of a bandwidth of data subcarriers.

4. The method according to claim 1 , wherein said first and/or second time-to-frequency conversion and said frequency-to-time conversion are performed with a 128-bit algorithm.

5. The method according to claim 1 , wherein said clipping level is a minimum possible clipping level leading to a minimum possible value for said peak-to-average power ratio.

6. The method according to claim 5 , wherein said clipping level is −7 dB.

7. A non-transitory computer readable recording medium storing a computer program comprising program instructions loadable into a data-processing unit to cause execution of the method according to claim 1 , when the computer program is run by the data processing unit.

8. An emitter for modulating and emitting an orthogonal frequency division multiplexing, OFDM, signal through a transmission channel, the emitter comprising:

a frequency-to-time converter for converting input frequency symbols into time symbols;

means for clipping time symbols connected to said frequency-to-time converter and configured to clip said time symbols;

a time-to-frequency convertor for converting said clipped time symbols into time-clipped frequency symbols; and

means for applying a set of subcarriers to said time-clipped frequency symbols output by said time-to-frequency converter, said means for applying a set of subcarriers being connected to input resulting frequency symbols to said frequency-to-time converter,

wherein said frequency-to-time converter converts said input resulting frequency symbols into time symbols, serializes and amplifies said time symbols to obtain said OFDM signal, and

said clipping is performed using a clipping level such that to optimize amplifying of said serialized time symbols.

9. The emitter according to claim 8 , wherein said set of subcarriers corresponds to data subcarriers.

10. The emitter according to claim 8 , wherein said means for applying said set of subcarriers set out-of-band subcarriers other than said set of subcarriers to zero before inputting said resulting frequency symbols to the frequency-to-time converter, outside of a bandwidth of data subcarriers.

11. The emitter according to claim 8 , wherein said time-to-frequency converter and said frequency-to-time converters have a length of 128 bits.

12. The emitter according to claim 8 , wherein said clipping level is use a minimum possible clipping level leading to a minimum possible peak-to-average power ratio.

13. The emitter according to claim 12 , wherein said clipping level is −7 dB.

14. The emitter according to claim 8 , adapted to emit 802.11 standard-compliant OFDM signal.