Design and Analysis of Wideband In-Band-Full- Duplex FR2-IAB Networks

Abstract

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

Design of Full Duplex Millimeter-Wave Integrated Access and Backhaul Networks

“…A Rician-alike channel model could be utilized to model the SI channel due to a strong LOS path. A detailed hypothetical wideband mmWave SI channel model is formulated in our recent work [10]. It is worth noting that there is still ambiguity in characterizing the mmWave SI channel model in the literature.…”

“…Since the BB channel estimation error model is still unknown for mmWave, even for the RF effective channel. However, without loss of generation, we model the BB channel estimation error matrix as a complex Gaussian random matrix with zero mean and small variance σ 2 e , and assume the RF effective channel estimation to be the combination between the RF beamforming and this random matrix [10], [12]. Note that interference leakage occurs due to the CEE and results in the RSI power.…”

“…Thus, the above hybrid design for the IAB-node needs to be modified. Moreover, without the assumption of the pre-known RF beamformings, one should get the RF beamformings by scanning a pre-defined codebook, and a relevant study has been proposed in our recent work [10].…”

“…Since the BB SIC depends on the estimated CSI of the SI channel, the CEE has a strong impact on the performance of digital SIC. A staged SIC which combines the RF and the digital cancellation is studied in our recent work [10]. Regarding the MUI, traditional ZF is utilized at the IAB-node transmitter based on the RF effective channel to obtain the desired BB precoder.…”

Design of Full-Duplex Millimeter-Wave Integrated Access and Backhaul Networks

“…Therefore, in this article, we assume the accurate knowledge of RF effective channel only, where the RF precoders and combiners are provided by genie. In practice, these RF quantities are obtained by beam-training codebooks [10]. Next, the optimal BB precoders/combiners can then be obtained as the left/right dominant singular vectors of the estimated RF effective channel matrix.…”