Method for synchronizing a signal comprising a plurality of chirps, and corresponding computer program product and device

A method for synchronizing a signal received by a communication receiver from an estimation of at least one piece of synchronization information of the signal, the signal comprising a plurality of chirps among M chirps, an s-th chirp among the M chirps being associated with a modulation symbol of rank s of a constellation of M symbols, s being an integer from 0 to M−1,

• the s-th chirp resulting from a modulation of a basic chirp of which an instantaneous frequency varies between a first instantaneous frequency and a second instantaneous frequency during a symbol duration time T,
• the modulation corresponding, for a modulation symbol of rank s, to a circular permutation of a variation pattern of said instantaneous frequency over the symbol duration time T, obtained by a time shift of s times an elementary time duration Tc, such that M*Tc=T,
• the method comprising, for a portion of the signal that is representative of at least one chirp of the plurality of chirps:
• estimating a first piece of time synchronization information that is representative of a time shift in the signal relative to a given time reference;
• estimating a piece of fractional frequency synchronization information that is representative of a frequency shift in the signal relative to a given frequency reference modulo an inverse of the symbol duration time T, by implementing the first piece of time synchronization information;
• estimating at least one second time synchronization information that is representative of a time shift of the signal relative to the given time reference by implementing the piece of fractional frequency synchronization information;
• wherein a portion of the signal comprising a plurality of successive elementary portions of a symbol duration time T starting at an instant according to the first piece of time synchronization information, for at least one pair of successive elementary portions of the plurality of successive elementary portions, the estimation of the piece of fractional frequency synchronization information implements a calculation of a correlation phase, of a correlation value between the signal considered over one of the at least one pair of successive elementary portions and the signal considered over another one of the at least one pair of successive elementary portions, the piece of fractional frequency synchronization information being according to the correlation phase;
• and wherein the estimation of the at least one second time synchronization information comprises a derotation of the portion of the signal according to the piece of fractional frequency synchronization information, delivering a portion of the signal partially resynchronized in frequency.

A device for synchronizing a signal received by a communication receiver from an estimation of at least one piece of synchronization information of the signal, the signal comprising a plurality of chirps among M chirps, an s-th chirp among the M chirps being associated with a modulation symbol of rank s of a constellation of M symbols, s being an integer from 0 to M−1,

• the s-th chirp resulting from a modulation of a basic chirp of which an instantaneous frequency varies between a first instantaneous frequency and a second instantaneous frequency during a symbol duration time T;
• the modulation corresponding, for the modulation symbol of rank s, to a circular permutation of a variation pattern of the instantaneous frequency over the symbol duration time T, obtained by a time shift of s times an elementary time duration Tc, such that M*Tc=T;
• the device comprising a processor configured to perform, for a portion of the signal that is representative of at least one chirp of the plurality of chirps:
• an estimation, implementing said first piece of time synchronization information of a first piece of time synchronization information that is representative of a time shift in the signal relative to a given time reference;
• an estimation of a piece of fractional frequency synchronization information that is representative of a frequency shift in such signal relative to a given frequency reference modulo the inverse of said symbol duration time T;
• wherein the processor is configured to perform:
• an estimation, implementing the piece of fractional frequency synchronization information, of at least one second piece of time synchronization information that is representative of a time shift of the signal relative to the given time reference;
• wherein the portion of the signal comprising a plurality of successive elementary portions of duration T starting at an instant according to the first piece of time synchronization information, for at least one pair of successive elementary portions of the plurality, said estimation of the piece of fractional frequency synchronization information implements a correlation calculation of a phase of a correlation value between the signal considered over one of the successive elementary portions of the at least one pair of successive elementary portions and the signal considered over another of the successive elementary portions of the at least one pair of successive elementary portions, the piece of fractional frequency synchronization information being according to the correlation phase;
• and wherein the estimation of the at least one second piece of time synchronization information comprises a derotation of the portion of the signal according to the piece of fractional frequency synchronization information, delivering a portion of the signal partially resynchronized in frequency.