In-Band, Full-Duplex Self-Interference Mitigation Under Realistic Hardware Constraints

Many radio frequency (RF) applications could benefit from simultaneous transmission and reception at the same frequency at the same time. Naively, these in-band, full-duplex (IBFD) RF systems would suffer from dramatic self-interference that inhibits capabilities and limits performance. We provide a system overview of self-interference mitigation techniques including antenna isolation, circulators, analog mitigation, and digital mitigation. We identify key technical issues that limit performance. Specifically, we discuss a digitally-controlled analog front-end that mitigates self-interference directly in the RF chain at the carrier frequency. We implement this approach in simulation and demonstrate that this solution provides sufficient mitigation in the context of a multiple-stage self-interference mitigation system. We further demonstrate the viability of this analog mitigation approach given delay spread, finite number of delay taps, non-negative constraint on tap weights, finite bit precision, individual and bulk timing errors, and dominant delay components that are off the lattice of delay taps.