1. Introduction

2. A Brief Tutorial of PNC
2.1. Non-network-coded Scheme (TS)
2.2. Non-physical-layer Network Coding Scheme (SNC)
2.3. Physical-layer Network Coding Scheme (PNC)
2.4. Generalization of PNC
2.5. Important Issues in PNC
2.6. Concluding Remarks for Brief Tutorial

3. Communication-theoretic Studies
3.1. Unchannel-coded PNC
3.2. Channel-coded PNC
3.3. To Probe Further

4. Information-theoretic Studies
4.1. Rate Region of Gaussian TWRC
4.2. Energy Implications for Gaussian TWRC
4.3. To Probe Further

5. Network-theoretic Studies
5.1. Asymptotic Performance Analysis
5.2. Practical Protocol Design
5.3. To Probe Further

6. Optical PNC

7. Conclusions