1 INTRODUCTION  
2 V2X SYSTEMATIC ARCHITECTURE  
2.1 Cloud Control and Third-party Platforms  
2.2 Roadside System  
2.3 Connected Vehicles (CVs)  
3 DATASETS  
3.1 Simulators  
3.2 Datasets based on Simulation  
3.3 Datasets based on Real-world Scenarios  
4 TAXONOMY  
4.1 Collaboration Stage  
4.2 Roadside Visual Sensors  
4.3 Communication Latency Compensation  
4.4 Collaboration Efficiency  
4.5 Adversarial Attack and Defense  
4.6 Pose Alignment  
4.7 Others  
5 EXPERIMENTAL ANALYSIS  
5.1 Comparisons of Model Attributes  
5.2 Performance-bandwidth Trade-off Analysis  
5.3 Comparison in Different LiDAR Ranges  
5.4 Robustness Analysis against Time Delay  
5.5 Robustness Analysis against Localization Error  
5.6 Robustness Analysis against Lossy Communication  
5.7 Robustness Analysis against Mixed Noises  
5.8 Sim-to-Real Generalization Evaluation  
5.9 Qualitative Analysis  
6 CHALLENGES AND FUTURE WORK  
6.1 Performance-bandwidth Trade-off  
6.2 Simulator  
6.3 LiDARs Placement  
6.4 Datasets and Collaboration Graph  
6.5 Transmission Scheme  
6.6 Generalization  
6.7 Fusion Methods  
6.8 Security and Privacy  
7 CONCLUSION