In-Band Full-Duplex Transceiver With Low-IF and Shared-LO Architecture for Small IoT Devices

In-band full duplex applied in Internet of Things (IoT) devices can help in realization of faster and denser wireless networks. Generally, in IoT systems, such as IEEE 802.15.4g, constant envelope modulation, which is resistant to nonlinear distortion, is employed. However, strong nonlinear distortion occurs even in such modulation schemes, and a tradeoff between cancellation performance and computational cost arises for terminals with limited computational resources. In addition, small IoT terminals cannot sufficiently suppress self-interference (SI) in the analog domain owing to form factor limitations. Therefore, this letter proposes an in-band full-duplex transceiver with a low intermediate frequency (IF) and shared local oscillator (LO) structure for IEEE 802.15.4g-based IoT devices that can achieve sufficient SI cancellation with a linear digital SI canceller of low computational cost. The proposed system significantly reduces computational cost, by up to 1/81 compared to a nonlinear SI canceller based on the Hammerstein model. Moreover, the system achieves 66 dB self-interference cancellation with the digital canceller alone and 99 dB with the digital cancellation and analog domain suppression, achieving almost down to the receiver noise floor even with low analog SI cancellation in practical wireless implementation.