1 INTRODUCTION  
1.2 Motivation of This Survey  
1.3 Contribution of Our Survey  

2 PRELIMINARIES OF BLOCKCHAINS  
2.1 Prime Blockchain Platforms  
2.2 Consensus Mechanism  
2.3 Scalability of Blockchains  

3 THEORIES TO IMPROVING THE PERFORMANCE OF BLOCKCHAINS

4 VARIOUS MODELINGS AND TECHNIQUES FOR BETTER UNDERSTANDING BLOCKCHAINS  
4.1 Graph-based Theories  
4.2 Stochastic Modelings  
4.3 Queueing Theories for Blockchain Systems  
4.4 Analytical Models for Blockchain Networks  
4.5 Data Analytics for Cryptocurrency Blockchains  

5 USEFUL MEASUREMENTS, DATASETS AND EXPERIMENT TOOLS FOR BLOCKCHAINS  
5.2 Useful Evaluation Tools for Blockchains  

6 OPEN ISSUES AND FUTURE DIRECTIONS  
6.1 Performance-Improving Issues  
6.2 Issues for Better Understanding Blockchains Further  
6.3 Security Issues of Blockchains  
6.4 Powerful Experimental Platforms for Blockchains  

7 CONCLUSION