1 INTRODUCTION  

2 TAXONOMY OF DISTRIBUTED DL  

3 SYNCHRONOUS/ASYNCHRONOUS FRAMEWORK  

4 CENTRALIZED/DECENTRALIZED FRAMEWORK  

5 QUANTIZATION METHODS  

6 SPARSIFICATION METHODS  

7 SCHEDULING OF COMMUNICATION AND COMPUTING  

8 CONVERGENCE ANALYSIS  

9 AUXILIARY TECHNOLOGIES  

10 CONCLUSION AND FUTURE DIRECTIONS  