1. Introduction.- 2 Self-Interference Cancellation in Full-Duplex Systems.- 3 Limiting Factors in Self-Interference Cancellation.- 4 Self-Interference Channel Estimation and Cancellation Using Compressed-Sensing and Subspace.- 5 Widely-Linear Subspace-Based Self-Interference Cancellation.- 6 Maximum Likelihood-Based Self-Interference Cancellation.- 7 Active Signal Injection for Self-Interference Cancellation.- 8 Conclusions and Future Work.- References.