A computer implemented method for detecting a vital sign of a subject, comprising at least one of a heart rate and a respiratory rate of the subject, said method comprising: receiving a reflected radio frequency signal from the subject, the reflected signal being based on a transmitted signal, which is Doppler-shifted due to mechanical movements corresponding to at least one of the heart rate and the respiratory rate to form the reflected signal; dividing a baseband signal based on the received signal and the transmitted signal into a sequence of sliding windows, wherein each sliding window represents a time interval of the baseband signal; splitting the baseband signal into a respiration information carrying signal and a heartbeat information carrying signal, wherein said splitting of the baseband signal comprises performing wavelet decomposition of the baseband signal and using components produced by the wavelet decomposition as input to an independent component analysis for splitting the signal, or decomposing the baseband signal into intrinsic mode functions using an ensemble empirical mode decomposition (EEMD) algorithm and using the intrinsic mode functions as input to an independent component analysis for splitting the signal; estimating a vital sign parameter based on the signal in at least one sliding window of the sequence of sliding windows, wherein said estimation of a vital sign parameter comprises performing estimation of respiration rate based on the respiration information carrying signal, and performing estimation of heart rate based on the heartbeat information carrying signal; determining whether a vital sign parameter may be reliably estimated based on the signal in at least one sliding window of the sequence of sliding windows; on condition that the vital sign parameter may not be reliably estimated in a sliding window, determining a vital sign parameter of the sliding window based on vital sign parameters estimated in a plurality of windows representing time intervals close to the time interval of the window for which the vital sign parameter is determined. receiving a reflected radio frequency signal from the subject, the reflected signal being based on a transmitted signal, which is Doppler-shifted due to mechanical movements corresponding to at least one of the heart rate and the respiratory rate to form the reflected signal; dividing a baseband signal based on the received signal and the transmitted signal into a sequence of sliding windows, wherein each sliding window represents a time interval of the baseband signal; splitting the baseband signal into a respiration information carrying signal and a heartbeat information carrying signal, wherein said splitting of the baseband signal comprises performing wavelet decomposition of the baseband signal and using components produced by the wavelet decomposition as input to an independent component analysis for splitting the signal, or decomposing the baseband signal into intrinsic mode functions using an ensemble empirical mode decomposition (EEMD) algorithm and using the intrinsic mode functions as input to an independent component analysis for splitting the signal; performing wavelet decomposition of the baseband signal and using components produced by the wavelet decomposition as input to an independent component analysis for splitting the signal, or decomposing the baseband signal into intrinsic mode functions using an ensemble empirical mode decomposition (EEMD) algorithm and using the intrinsic mode functions as input to an independent component analysis for splitting the signal; estimating a vital sign parameter based on the signal in at least one sliding window of the sequence of sliding windows, wherein said estimation of a vital sign parameter comprises performing estimation of respiration rate based on the respiration information carrying signal, and performing estimation of heart rate based on the heartbeat information carrying signal; determining whether a vital sign parameter may be reliably estimated based on the signal in at least one sliding window of the sequence of sliding windows; on condition that the vital sign parameter may not be reliably estimated in a sliding window, determining a vital sign parameter of the sliding window based on vital sign parameters estimated in a plurality of windows representing time intervals close to the time interval of the window for which the vital sign parameter is determined.