On the impact of phase noise on active cancelation in wireless full-duplex

Recent experimental results have shown that full-duplex communication is possible for short-range communications. However, extending full-duplex to long-range communication remains a challenge, primarily due to residual self-interference, even with a combination of passive suppression and active cancelation methods. In this paper, we investigate the root cause of performance bottlenecks in current full-duplex systems. We first classify all known full-duplex architectures based on how they compute their canceling signal and where the canceling signal is injected to cancel self-interference. Based on the classification, we analytically explain several published experimental results. The key bottleneck in current systems turns out to be the phase noise in the local oscillators in the transmit-and-receive chain of the full-duplex node. As a key by-product of our analysis, we propose signal models for wideband and multiple-input-multiple-output (MIMO) full-duplex systems, capturing all the salient design parameters, thus allowing future analytical development of advanced coding and signal design for full-duplex systems.