In-band Full-duplex in Hand-held Applications: Analysis of Canceller Tuning Requirements

This paper investigates the impact of user-antenna interaction on transmit-to-receive (Tx-Rx) isolation in a handheld In-band Full-duplex (IBFD) transceiver. Dynamic antenna measurements which capture the effect of user hand movements at 1900 MHz are incorporated into simulations of a two stage adaptive self-interference canceller, which simulates an electrical balance duplexer and a second stage of digital cancellation with different tracking adaptation rates. Results demonstrate that the dynamic self-interference channel which results from user movement places demanding requirements on the canceller coefficient tracking. Adaptation intervals of the order of tens of microseconds are required to maintain Tx-Rx isolation of the order of 90 dB, calling into question the feasibility of IBFD handheld devices.