Steer: Beam Selection for Full-Duplex Millimeter Wave Communication Systems

Abstract

Modern millimeter wave (mmWave) communication systems rely on beam alignment to deliver sufficient beamforming gain to close the link between devices. We present a novel beam selection methodology for multi-panel, full-duplex mmWave systems, which we call STEER, that delivers high beamforming gain while significantly reducing the full-duplex self-interference coupled between the transmit and receive beams. STEER does not necessitate changes to conventional beam alignment methodologies nor additional over-the-air feedback, making it compatible with existing cellular standards. Instead, STEER uses conventional beam alignment to identify the general directions beams should be steered, and then it makes use of a minimal number of self-interference measurements to jointly select transmit and receive beams that deliver high gain in these directions while coupling low self-interference.We implement STEER on an industry-grade 28 GHz phased array platform and use further simulation to show that full-duplex operation with beams selected by STEER can notably outperform both half-duplex and full-duplex operation with beams chosen via conventional beam selection. For instance, STEER can reliably reduce self-interference by more than 20 dB and improve SINR by more than 10 dB, compared to conventional beam selection. Our experimental results highlight that beam alignment can be used not only to deliver high beamforming gain in full-duplex mmWave systems but also to mitigate selfinterference to levels near or below the noise floor, rendering additional self-interference cancellation unnecessary with STEER. I. INTRODUCTIONTo equip millimeter wave (mmWave) transceivers with full-duplex capability, recent work has proposed leveraging dense antenna arrays to mitigate self-interference spatially via strategic I. P. Roberts, S. Vishwanath, and J. G. Andrews are with the 6G@UT Research Center and the Wireless Networking and Communications Group at the University of Texas at Austin. T. Novlan is with the Advanced Wireless Technologies Group at AT&T Labs. A. Chopra was with AT&T Labs during this work; he is now with Project Kuiper, Amazon.

Full-Duplex Transceivers for Next-Generation Wireless Communication Systems

“…Therefore, one can imagine it would be preferable from a full-duplex perspective to jointly select transmit and receive beams that deliver high SNR tx and SNR rx and also couple low INR rx . This is precisely the motivation for [77], which is also introduced in Subsection 4.7. If codebooks could be designed such that all possible f ★ , w ★ couple sufficiently low SI, then beam alignment may be conducted on the transmit and receive links independently, as shown in (16), with guarantees of low SI regardless of which beams are selected-the motivation for [54,73] and the codebook design problem introduced in Subsection 4.3.…”

“…Early deployments of full-duplex mmWave base Fig. 17 The 28 GHz phased array platform used for measurements of SI in [76,77,80]. Transmit array on right; receive array on left.…”

“…work of [77], in which the authors propose the first beam selection methodology for full-duplex mmWave communication systems. Traditional beam selection typically selects beams that maximize SNR via codebook-based beam alignment measurements, as highlighted in (16).…”

“…Traditional beam selection typically selects beams that maximize SNR via codebook-based beam alignment measurements, as highlighted in (16). In [77], the authors propose a measurement-driven beam selection methodology, called S , atop conventional beam alignment that incorporates SI into transmit and receive beam selection at a full-duplex mmWave transceiver.…”

“…While these initial beam selections may yield high SNRs, they are likely to couple high levels of SI, shown by measurements in [76]. To identify transmit and receive beams that the base station can use to deliver high SNRs and low SI, the authors of [77] propose S .…”