Pseudo-guard intervals insertion in an FBMC transmitter

1. An FBMC/OQAM modulator, to modulate an FBMC/OQAM signal from a binary stream, the FBMC/OQAM modulator comprising at least one QAM mapper to map said binary stream into at least one time domain representation of complex symbols, a first transmission chain and a second transmission chain, each transmission chain comprising:

a precoder configured to transpose a first, and respectively a second, set of symbols obtained from the said complex symbols into a frequency domain representation of real, respectively imaginary, samples,

a phase rotator configured to apply a phase quadrature keying to the samples that output the decoder, and

an FBMC modulator configured to modulate the output of the phase rotator into a time domain representation of an FBMC symbol, the FBMC/OQAM modulator further comprising an adder to sum the output of the first transmission chain with a delayed version of the output of the second transmission chain, wherein the FBMC/OQAM modulator is further configured to insert guard interval sequences into the binary stream that input the QAM mapper, or into the symbols in the time domain representation processed by the precoders.

2. The FBMC/OQAM modulator of claim 1 , wherein the first and second sets of symbols are made of distinct symbols from the said complex symbols that are output to the QAM mapper, and wherein the precoders of the first and second transmission chains are configured to process respectively the first and second sets of symbols by at least:

reordering the set of symbols by concatenating to said set of symbols a flipped version of the complex conjugate of the set of symbols,

performing a Fourier transform over the reordered symbols, and

applying a

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i

⁢

⁢

π

⁢

k

N

linear phase shift to the samples that output the Fourier transform, where N is the number of samples that output the Fourier transform, and k is the index of the sample to which the phase rotation is applied.

3. The FBMC/OQAM modulator of claim 1 , wherein the first, and respectively second, set of symbols is made of the real, and respectively imaginary, part of the said complex symbols that are output to the QAM mapper, and wherein the precoder of the first transmission chain and the precoder of the second transmission chain are configured to perform a Direct Cosine transform over the respective sets of symbols.

4. The FBMC/OQAM modulator of claim 1 , wherein the FBMC modulator of the first and second transmission chains are configured to modulate a time domain representation of an FBMC symbol from samples in a frequency domain representation by performing at least:

an oversampling, by a factor K greater or equal than one,

a filtering by a prototype filter, and

an inverse Fourier transform.

5. The FBMC/OQAM modulator of claim 1 , wherein an oversampling factor K of the FBMC modulation is greater than one, and wherein the FBMC/OQAM signal modulated overlaps with K−1 other FBMC/OQAM signals.

6. The FBMC/OQAM modulator of claim 1 , wherein the guard interval sequences are inserted so as to be positioned over samples comprising samples situated substantially at the end of the first half of FBMC symbols generated by the FBMC modulators.

7. The FBMC/OQAM modulator of claim 1 , wherein the guard interval sequences are null sequences.

8. A radio communication equipment comprising at least one FBMC/OQAM modulator according to claim 1 .

9. A method, to modulate an FBMC/OQAM signal from a binary stream, comprising the steps of:

performing a QAM mapping of said binary stream, to obtain a time domain representation of complex symbols,

computing a first and a second set of symbols from the said complex symbols,

processing the first set of symbols by a first processing chain and the second set of symbols by a second processing chain, wherein each processing comprises:

precoding the set of symbols to transpose it into a frequency domain representation of real, respectively imaginary, samples,

applying a phase quadrature keying to the frequency domain representation of samples,

applying an FBMC modulation to the rotated frequency domain representation of complex samples,

delaying the samples of the second processing chain, summing the output of the first processing chain with the output of the second processing chain,

the method further comprising a step of inserting guard interval sequences into the binary stream or into the symbols in the time domain representation that are processed by the precoders.

10. A non-transitory computer readable storage medium storing a computer program comprising instructions, when executed by a processor, to implement the method of claim 9 .