I. INTRODUCTION  
II. UNDERSTANDING FALLS  
A. The Challenges of Fall Detection  
B. Fall Categories and Scenarios  
C. Quality Metrics for Fall Detection  
III. RADAR FALL DETECTION FUNDAMENTALS  
A. Radar Signal Processing  
B. Machine Learning for Fall Detection  
IV. REVIEW OF RADAR-BASED FALL DETECTION  
V. DISCUSSION  
VI. CONCLUSION