This paper develops a 3GPP-inspired design for the 1 in-band-full-duplex (IBFD) integrated access and backhaul (IAB) 2 networks in the frequency range 2 (FR2) band, which can 3 enhance the spectral efficiency (SE) and coverage while reducing 4 the latency. However, the self-interference (SI), which is usually 5 more than 100 dB higher than the signal-of-interest, becomes the 6 major bottleneck in developing these IBFD networks. We design 7 and analyze a subarray-based hybrid beamforming IBFD-IAB 8 system with the RF beamformers obtained via RF codebooks 9 given by a modified Linde-Buzo-Gray (LBG) algorithm. The 10 SI is canceled in three stages, where the first stage of antenna 11 isolation is assumed to be successfully deployed. The second stage 12 consists of the optical domain (OD)-based RF cancellation, where 13 cancelers are connected with the RF chain pairs. The third stage 14 is comprised of the digital cancellation via successive interference 15 cancellation followed by minimum mean-squared error baseband 16 receiver. Multiuser interference in the access link is canceled by 17 zero-forcing at the IAB-node transmitter. Simulations show that 18 under 400 MHz bandwidth, our proposed OD-based RF cancel-19 lation can achieve around 25 dB of cancellation with 100 taps. 20 Moreover, the higher the hardware impairment and channel 21 estimation error, the worse digital cancellation ability we can 22 obtain. 23 Index Terms-Wideband in-band-full-duplex millimeter wave 24 (FR2 band), subarray hybrid beamforming, integrated access and 25 backhaul, codebook design, self-interference cancellation. 26 I. INTRODUCTION 27 F REQUENCY range 2 (FR2) band (i.e., millimeter wave) 28 communications have been identified as the key technol-29 ogy for the beyond fifth-generation (5G) wireless communi-30 cations to provide much larger bandwidth, narrower beam, 31

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This paper studies a solution for efficient industrial Internet of things (IIoT) communications through a in-band full-duplex (IBFD) enabled private 5G network in frequency range 2 (FR2) band (≥ 24.250 GHz), where ultra-reliable low-latency communications (URLLC) and enhanced mobile broadband (eMBB) devices can be simultaneously served. Large-scale antenna array and RF beamforming are applied, and a self-interference cancellation (SIC) scheme is proposed under such architecture. Particularly, the proposed RF cancellation scheme addressed two key issues of extending current technologies to wideband operations in FR2 band: limited operational bandwidth and the requirement for a large number of cancellers. Then, a frequency domain-based digital canceller is proposed to process with the residual self-interference (RSI) with short processing latency. A game theoretic user allocation algorithm is proposed to minimise cochannel interference (CCI) in a heterogeneous environment. Given a typical IIoT scenario, the performance of such IBFD private 5G network is evaluated in terms of bit-error rate (BER) and spectral efficiency (SE) through simulations and analysed based on numerical results and theoretical calculations. It is demonstrated that the latency of uplink eMBB devices can be reduced by 54% through IBFD radios, and the latency of downlink URLLC devices can be reduced to 0.5 ms with the help of flexible numerology, mini-slot, and self-contained sub-frames introduced in 5G NR. IBFD radios can enhance the SE by 92% compared to HD radios with our SIC and user allocation policy. The high SE in conjunction with abundant resources in FR2 band provide multi-Gbps peak data rates, high reliability, and massive connectivity.

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