Phase Noise in Full-Duplex Radios Using Off-the-Shelf Oscillators

This letter analyzes the effect of phase noise (PN) on digital non-linear self-interference (SI) cancellation for low delay spread non-linear SI channels typical of small form factor in-band full-duplex (IBFD) radios in indoor environments. Use of a shared local oscillator (LO) between the transmit and receive radios is assumed, and it is shown that, in theory, un-cancelled SI due to PN can be reduced by optimizing the relative delay between receive LO path and SI channel. Simulations and measurements from hardware IBFD transceivers using realistic LO phase noise characteristics demonstrate that, for these devices/environments, in practice LO phase noise does not limit digital cancellation when using shared local oscillators.