Method for demodulating a signal

摘要

A method for demodulating a signal in a receiver including at least two antennas, each receiving a signal, the received signals corresponding to a single emitted signal including symbol frames in which certain symbols, referred to as driver symbols, are known to the receiver, the method including: noise whitening in order to form two combined signals, the noise components of which are separate; normalizing the noise components of the combined signals in order to form two signals, the noise components of which are separate and have equal average standards; and performing signal demodulation with the maximum combination of the signal-to-noise ratio on the two signals, the noise components of which are separate and which have equal average standards, wherein during the first noise-whitening step for forming the two combined signals, the latter are determined retroactively using the maximum criterion.

主权项

1. A method for demodulating a signal in a receiver comprising at least two antennas each receiving a signal transmitted through an associated radio propagation channel, the signals received corresponding to a same emitted signal comprising time and frequency distributed symbol frames in which driver symbols are known to the receiver, said method comprising:
noise whitening to form two combined signals that have noise components which are separate; normalising the noise components of the two combined signals in order to form two signals (r′, r″) that have noise components which are separate and have equal average standards; performing signal demodulation with a maximum combination of a signal-to-noise ratio on the two signals (r′, r″), the noise components of which are separate and which have equal average standards, wherein the noise whitening to form the two combined signals comprises: weighting each of the signals received with respective first weighting vectors associated with a respective antenna of the receiver, the signal associated with the first antenna being weighted by a weighting vector w1 and the signal associated with the second antenna being weighted by a weighting vector w2, combining the weighted received signals in order to form a first combined signal (c1), weighting a reference signal comprising said driver symbols with another weighting vector, comparing the first combined signal and the weighted reference signal in order to form an error, determining the weighting vectors (w1; w2) using a maximum a posteriori criterion by maximising a probability of occurring of said weighting vectors (w1; w2) conditionally with the error obtained, weighting each signal received with: second weighting vectors (w*2, −w*1), the signal received on the first antenna being weighted by a conjugate of a complex vector w2 and the signal received on the second antenna being weighted by an opposite of the conjugate of a complex vector w1, combining signals received weighted by the second weighting vectors in order to form a second combined signal (c2), wherein respective coefficients of the propagation channel corresponding to a useful signal associated with the respective antenna of the receiver and used in performing signal demodulation with the maximum combination of the signal-to-noise ratio on the two signals (r′, r″), obtained at an end of the noise-whitening step, are determined using the maximum a posteriori criterion by maximising the probability of the occurring of the channel conditionally with the error present on the one hand in the first combined signal (c1) and on the other hand in the second combined signal (c2), by taking into account the propagation channel seen in the first combined signal (c1) and in the second combined signal (c2).