An apparatus for vital sign detection, wherein the vital sign is breathing, heartbeat or another vital sign having a periodic pattern, comprising: a receiver configured for receiving at least one wireless signal from a multipath channel that can be impacted by a vital sign of at least one living being; a processor; and a memory communicatively coupled with the processor, wherein the processor is configured for: extracting a time series of channel state information, CSI, for the multipath channel from the at least one wireless signal, obtaining one or more periodic fluctuations based on a spectral analysis of the time series of CSI, determining whether the vital sign is present based on the one or more periodic fluctuations, and upon determining that the vital sign is present, determining one or more vital sign rates of one or more living beings; calculating a time-reversal resonance strength, TRRS, matrix based on the time series of CSI, and smoothing the TRRS matrix in time domain to generate a smoothed TRRS matrix, wherein the spectral analysis is performed based on the smoothed TRRS matrix; and either: performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, generating a pseudo-spectrum based on the noise subspace, performing spectrum folding on the pseudo-spectrum to generated an updated pseudo-spectrum, trimming the updated pseudo-spectrum into a range related to vital sign rate, and detecting one or more peaks of the updated pseudo-spectrum within the range, wherein the one or more vital sign rates of the one or more living beings are determined based on the detected one or more peaks; or performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, obtaining a matrix based on the noise subspace, generating a polynomial equation based on the obtained matrix, and selecting one or more complex roots of the polynomial equation, wherein the one or more vital sign rates of the one or more living beings are determined based on information related to at least one of angle and phase of the one or more complex roots. a receiver configured for receiving at least one wireless signal from a multipath channel that can be impacted by a vital sign of at least one living being; a processor; and a memory communicatively coupled with the processor, extracting a time series of channel state information, CSI, for the multipath channel from the at least one wireless signal, obtaining one or more periodic fluctuations based on a spectral analysis of the time series of CSI, determining whether the vital sign is present based on the one or more periodic fluctuations, and upon determining that the vital sign is present, determining one or more vital sign rates of one or more living beings; calculating a time-reversal resonance strength, TRRS, matrix based on the time series of CSI, and smoothing the TRRS matrix in time domain to generate a smoothed TRRS matrix, wherein the spectral analysis is performed based on the smoothed TRRS matrix; and either: performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, generating a pseudo-spectrum based on the noise subspace, performing spectrum folding on the pseudo-spectrum to generated an updated pseudo-spectrum, trimming the updated pseudo-spectrum into a range related to vital sign rate, and detecting one or more peaks of the updated pseudo-spectrum within the range, wherein the one or more vital sign rates of the one or more living beings are determined based on the detected one or more peaks; or performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, obtaining a matrix based on the noise subspace, generating a polynomial equation based on the obtained matrix, and selecting one or more complex roots of the polynomial equation, wherein the one or more vital sign rates of the one or more living beings are determined based on information related to at least one of angle and phase of the one or more complex roots. performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, generating a pseudo-spectrum based on the noise subspace, performing spectrum folding on the pseudo-spectrum to generated an updated pseudo-spectrum, trimming the updated pseudo-spectrum into a range related to vital sign rate, and detecting one or more peaks of the updated pseudo-spectrum within the range, wherein the one or more vital sign rates of the one or more living beings are determined based on the detected one or more peaks; or performing an eigenvalue decomposition on the TRRS matrix, obtaining a noise subspace based on the eigenvalue decomposition, obtaining a matrix based on the noise subspace, generating a polynomial equation based on the obtained matrix, and selecting one or more complex roots of the polynomial equation, wherein the one or more vital sign rates of the one or more living beings are determined based on information related to at least one of angle and phase of the one or more complex roots.