1 Introduction  
2 Preliminary  
2.1 Federated Edge Learning  
2.2 Knowledge Distillation  
2.3 Why Concern Knowledge Distillation in Federated Edge Learning  
3 Challenges in Federated Edge Learning with Solutions based on Knowledge Distillation  
4 Discussion  
4.1 Limitations  
4.2 Open Problems  
4.3 Practical Guidance for Real Deployment  
5 Conclusion