I. INTRODUCTION  
A. Motivations and Contributions  

II. CHALLENGES DISCUSSED IN THE LITERATURE  
A. Challenges to Frequency Division Duplexing (FDD)  
B. Challenges to Hybrid Beam-Forming (HBF)  
C. Challenges to TDD  
D. Challenges to CSI-Network (CsiNet) and CsiNet-Longshort-Term-Memory (CsiNet-LSTM)  

IV. NUMERICAL RESULTS  
A. Evaluation  
B. Open Trends (Future Work)  

V. CONCLUSION