The data filtering phase collects data from sensor arrays and extracts the key information from the data. For real-time signal streams, the processing flow continuously calculates signal features. Raw data received from the sensors is initially treated as discrete signals. For example, the sensor array applies peak extraction and filtering functions to the
raw data, and then sends the filtered data to the feature extractor, which extracts some mathematical features, such as mean, first-order differences, and peak-to-peak intervals, as basic records. Finally, it converts the extracted signal features to a context generator, which produces the preliminary context for the upper layers, and only collects the necessary contexts as probabilistic conditions. In this procedure, the context interpreter plays a key role in the context-aware service, which includes