Table 1.

The most frequently used keywords in the topic of fall detection.

Wearable sensor	Visual sensor	Ambient sensor	Sensor fusion
Fall detection	Fall detection	Fall detection	Fall detection
Falls	Falls	Falls	Falls
Fall accident	Fall accident	Fall accident	Fall accident
Machine learning	Machine learning	Machine learning	Machine learning
Deep learning	Deep learning	Deep learning	Deep learning
Reinforcement learning	Reinforcement learning	Reinforcement learning	Reinforcement learning
Body area networks	Multiple camera	Ambient sensor	Health monitoring
Wearable	Visual	Ambient	Sensor fusion
Worn	Vision-based	Ambience	Sensor network
Accelerometer	Kinect	RF-sensing	Data fusion
Gyroscope	Depth camera	WiFi	Multiple sensors
Biosensor	Video surveillance	Radar	Camera arrays
Smart watch	RGB camera	Cellular	Decision fusion
Gait	Infrared camera	Vibration	Anomaly detection
Wearable based	Health- monitoring	Ambience-based	IoT

They are manually classified into four categories.