GMC	Generalized Minimax Concave Penalty
GSNC	Grey Spectral Noise Cancellation
GSNE	Grey Spectral Noise Estimation
ECG	Electrocardiogram
EMD	Empirical Mode Decomposition
SASS	Sparsity Assisted Signal Smoothing
NLM	Non-local Means
IMFs	Intrinsic Mode Functions
LTI	Linear Time Invariant
AWGN	Additive White Gaussian Noise
LPF	Low-pass Filter
HPF	High-pass Filter
STFT	Short Time Fourier Transform
BPD	Basis Pursuit Denoising
FBS	Forward-backward Spliting
SNR	signal-to-noise ratio
$SN{R}_{imp}$	signal-to-noise ratio improvement
RMSE	average of root mean square error
PRD	Percent root mean square difference