On the performance of active analog self-interference cancellation techniques for beyond 5G systems

The in-band full-duplex (IBFD) mechanism is of interest in beyond 5G systems due to its potential to enhance spectral efficiency and reduce delay. To achieve the maximum gain of IBFD systems, the significant self-interference (SI) must be efficiently suppressed. The challenges of wideband self-interference cancellation (SIC) lie in the radio frequency (RF) domain, where the performance will be limited by the hardware. This paper reviews current RF cancellation mechanisms and investigates an efficient mechanism for future wideband systems with minimum complexity. The working principle and implementation details of multi-tap cancellers are first introduced, then an optical domain-based RF canceller is reviewed, and a novel low-cost design is proposed. To minimize the cost and complexity of the canceller, the minimum required number of taps are analyzed. Simulation results show that with the commonly used 12-bits analog-to-digital converter (ADC) at the receiver, the novel optical domain-based canceller can enable efficient SIC in the 3GPP LTE specifications compatible system within 400 MHz bandwidth.