Narrowband Internet of Things downlink receiving method based on channel estimation and retransmission soft combination

The invention discloses a narrowband Internet of Things downlink receiving method based on channel estimation and retransmission soft combination. The method comprises the following steps of: definingan autocorrelation matrix; carrying out eigenvalue decomposition on the autocorrelation matrix to simplify an LMMSE algorithm so as to complete channel impact response of an estimation frequency domain, thus obtaining hMMSE; performing time domain filtering on the hMMSE by using fast Fourier transform to suppress the influence of noise; on the basis of the S3, carrying out one-dimensional linearinterpolation processing on the OFDM symbol containing the NRS in the frequency domain; acquiring channel impact response estimated values of frequency domains of all sent symbols through time domainaveraging; and repeatedly transmitting the soft information with the transmitting signal probability obtained by demodulation, and using equal gain combination, thus improving the performance of the system. According to the inv