Nyström Method-Based Hybrid Precoding for mmWave Full-Duplex Integrated Access and Backhaul Systems

Integrated Access and Backhaul (IAB) systems, millimeter-wave (mmWave), and full-duplex (FD) are the critical technologies for the 5G and beyond cellular networks. The capacity and efficiency are significantly enhanced, thanks to the large available bandwidth and simultaneous transmission. However, self-interference (SI) becomes significant, which needs to be canceled in different stages. In this paper, under the mmWave-FD-IAB systems, we propose a fast hybrid precoding algorithm using the Nyström method for the wideband single-user scenario. SI and residual SI (RSI) is canceled by RF precoder and minimum mean squared error combiner at the IAB-node transmitter and receiver, respectively. RF insertion loss with different kinds of phase shifters (PSs) and channel estimation error are considered for accounting the impact of the RF components impairment and channel uncertainty. Simulations show that the proposed design can enhance the backhaul link spectral efficiency and cancel the SI efficiently at the IAB-node. Moreover, passive PSs can tolerate more RSI than active PSs.