Information channel estimating method and system in radio communication

Abstract

A method for estimating channel in radio communication includes carrying out fading factor spectrum estimation according to fading factor initial estimation and calculating out relevant Doppler frequency deviation estimating result according to obtained spectrum estimating result , carrying out spectrum move for fading factor initial estimation according to Doppler frequency deviation estimating result . Carrying out low pass filtering on spectrum - moved signal and carrying out reverse move for signal being filtered with low pass to obtain final result of channel estimation .

Description

technical field [0001] The present invention relates to the technical field of wireless communication, more specifically to a channel estimation method and system in wireless communication. Background technique [0002] As we all know, there is a multipath propagation phenomenon in wireless communication channels. When the receiver moves in space, the degree of coherence and cancellation of multipath signals will change when the multipath signals are superimposed on the receiver due to the change of different multipath transmission phases, resulting in the generation of received signals. The so-called fading phenomenon. Fading will not only cause the amplitude of the received signal to fluctuate sharply in a wide range, but also cause the phase of the received signal to change randomly. For phase modulation technologies such as binary phase shift keying (BPSK) and quadruple phase shift keying (QPSK), they are very sensitive to phase changes when receiving signals. Therefore...

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Problems solved by technology

[0015] In the actual environment, due to some reasons, it is difficult to achieve the optimal effect of the filter, the key module in channel estimation. These reasons include: first, the moving speed of the receiver relative to the transmitter changes at any time, making the filter The optimal cut-off frequency of the converter must be adjusted dynamically

Second, due to the difference in the local oscillator frequency of the receiver and the transmitter, or in some wireless environments due to the relative movement of the receiver and the transmitter will cause an additional frequency offset f d Modulation, so that there will be a phenomenon of spectrum shift on the frequency spectrum

In this case, the frequency of the fading factor is not symmetrical about the zero frequency center, and the filter with the same cutoff frequency will cause a large deviation in the estimation result. If the cutoff frequency of the low-pass filter is greater than f d +f o , the large bandwidth will also reduce the output signal-to-noise ratio, which will deteriorate the receiver's modulation performance

Third, the shape of the fading factor spectrum generated by the actual wireless environment may be very complex and irregular, which will also bring difficulties to the design of the low-pass filter

[0025] The scheme shown in Figure 7 solves the estimation problem of the Doppler spectrum fading factor shown in Figure 4 to some extent, but the scheme still has the following problems: frequency offset estimation and Doppler frequency estimation are carried out independently Yes, this increases the complexity of the system; there is a phase calculation link in the cross-product frequency discrimination, which needs to perform division and arctangent operations, these two complex operations need to consume a lot of software and hardware resources; in addition, the cross-product The Doppler frequency offset estimation method based on frequency discrimination and re-filtering has good accuracy in the environment with small Doppler frequency, but in the case of large Doppler frequency expansion, the estimation error obtained by this method is very large, so that Will affect the overall accuracy of channel estimation

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