Embodiments provide a scheme for estimating an optimal read threshold voltage using a deep neural network (DNN) with reduced number of processing. A controller receives first and second program voltage (PV) levels associated with read operations on cells. The controller estimates first and second probability distribution parameter sets representing skew normal distributions of the first and second PV levels, respectively. The controller estimates an optimal read threshold voltage based on the first and second probability distribution parameter sets. The optimal read threshold voltage is a read threshold voltage such that first probability density function (PDF) value of the skew normal distribution of the first PV level is the same as the second PDF value of the skew normal distribution of the second PV level.