Sampling is a technique used in changing analog signals into digital ones. To change continuous analog signals into discrete digital signals, data should be extracted from analog signals by specified interval. Such extraction of data is called as sampling and the interval for extraction is called as sampling frequency. The amount of data will vary depending on sampling frequency. Longer sampling frequency leads to smaller number of data obtained from analog signals, resulting in smaller amount of data when changed into digital signals. On the contrary, shorter sampling frequency results in larger amount of data.
Resampling is a process of re-structuring data obtained from a specified sampling frequency into data of another sampling frequency. Users can adjust the amount of data using this process. For resampling, the approximate function of signals should be defined using the mathematical algorithm of Interpolation. In other words, Interpolation is a process of approximating a signal at the specified point using neighboring signals. Such interpolation can be classified into various methods depending on which function is used. Three representative methods are Polynomial Interpolation, Rational Function Interpolation, and Cubic Spline Interpolation.