I. INTRODUCTION  
II. BACKGROUND  
III. INDOOR POSITIONING SYSTEM (IPS)  
A. Positioning Techniques  
B. Sensing Techniques  
IV. PIONEERING SENSING TECHNOLOGIES FOR INDOOR POSITIONING  
A. Visible Light Communication (VLC)-based  
B. Infrared (IR)-based  
C. LiDAR-based  
D. Sound-based  
E. RADAR-based  
F. Magnetic Sensors-based  
G. Sensors-based  
H. Wireless Sensor Networks (WSN)-based  
I. Radio Frequency Identification (RFID)-based  
J. Bluetooth-based  
K. Wi-Fi-based  
L. Cellular  
M. Ultra-wideband (UWB)  
V. IPS DATASETS  
VI. FUTURE DIRECTIONS  
VII. CONCLUSION