*3.3. Data Pre-Processing Filtering and Feature Extraction*

The raw signals were processed by applying a median filter and 3rd order low pass Butterworth filter with 20 Hz cut-off. These signals were then segmented with fixed width sliding windows of 2.56 s with 50% overlap. A total of 17 features extracted from the time and frequency domains for each window were used in this work, where only about six features are shown in Table 2. The full 17 features can be found in [42].

**Table 2.** 6 Features extraction of time and frequency domain for each window.

