Doppler frequency offset estimation method and apparatus and doppler frequency offset elimination method and apparatus in OFDM system

Abstract

The embodiment of the present invention provides a doppler frequency offset estimation method and apparatus and a doppler frequency offset elimination method and apparatus in an orthogonal frequency division multiplexing (OFDM) system. The doppler frequency offset estimation method comprises: an OFDM propagation signal is received, wherein a first OFDM symbol in a first OFDM frame in the OFDM propagation signal includes Q preset cyclic prefixes and the Q is larger than or equal to 3; autocorrelation in pairs is carried out on all the preset cyclic prefixes to obtain a plurality of autocorrelation functions; summation is carried out on all the autocorrelation functions to obtain a probability density function; maximum likelihood estimation is carried out on the probability density function to obtain a starting doppler frequency offset and a doppler change rate; and according to the starting doppler frequency offset and the doppler change rate, an objective doppler frequency offset changing with a signal sequence position in the first OFDM frame in the OFDM propagation signal is estimated. Therefore, accuracy of the estimation result is improved and the effect of doppler effect elimination is enhanced.

Description

technical field [0001] The present invention relates to the technical field of wireless communication, in particular to a method and device for estimating Doppler frequency offset in an OFDM system and a method and device for eliminating it. Background technique [0002] When there is relative motion between the transmitting end and the receiving end, the phase and frequency of the source signal transmitted by the transmitting end will change during the propagation process, and the frequency of the signal received by the receiving end is different from the frequency of the source signal. It is called the Doppler effect, and the difference between the frequency of the signal received by the receiver and the frequency of the source signal is called the Doppler frequency offset. Due to the influence of Doppler frequency offset, the signal received by the receiving end usually has problems such as interference, distortion or data loss. [0003] In an OFDM (Orthogonal Frequency ...

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Problems solved by technology

[0008] However, due to the influence of various factors at the transmitting end, receiving end and the surrounding environment, the OFDM source signal transmitted by the transmitting end will undergo different changes during the propagation process, and the changes are random without any rules to follow. Therefore, If according to the method of the prior art, only two preset cyclic prefixes are selected for autocorrelation, the Doppler frequency offset estimation result of the obtained OFDM propagation signal changes with the position of the signal sequence has a large error, which cannot describe the OFDM propagation well. The actual size of the Doppler frequency deviation in the signal is not accurate; and, after the transmitter obtains the Doppler frequency deviation in this way, when the Doppler frequency deviation is reversely processed on the OFDM source signal, the Doppler frequency deviation is eliminated. The effect of Le effect also needs to be improved

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