Over the past years, Fall Detection System (FDS) has undergone extensive
research to improve living risk, especially for the elderly who are
vulnerable to these fall events. Devices employing sensors are crucial
components of FDS in achieving high accuracy and sensitivity. This
article overviews different sensor modalities, such as ambient-based and
vision-based systems, as well as commonly used wearable devices for fall
detection, along with the associated data processing algorithms. The
critical elements of fall detection, such as architectures and
algorithms for processing sensor data, machine learning and deep
learning methodologies, and validation of FDS performance, are
considered. The article also delves into safety aspects and presents
technical challenges and concerns in FDS for researchers in the field to
identify areas requiring further improvement. Finally, future research
opportunities to improve fall detection for widespread use are outlined.