AI summaryⓘ
The authors explore a simpler and cheaper way to make hybrid beamforming work in wireless systems by sharing phase shifters (PS) among multiple antennas instead of giving each antenna its own. They design a setup where antennas connect statically but still allow flexible beam control through smart PS connections and digital processing. For single and multiple RF chain systems, they propose algorithms to group antennas or optimize quality of service while keeping most of the beamforming performance. Their approach cuts down the number of PS needed significantly without causing common signal problems. This shows that reducing hardware costs is best done by carefully planning how phase shifters are shared rather than just using fewer parts.
Hybrid beamformingPhase shifterSub-connected architectureRF chainDigital precodingAntenna groupingQuality of service (QoS)Majorization-minimization (MM) algorithmBeamforming capabilityAnalog phase-shifter network
Authors
Honghao Wang, Qingqing Wu, Yifei Wu, Yuxuan Chen, Wen Chen, Derrick Wing Kwan Ng
Abstract
Hybrid beamforming is a promising solution for high-frequency multi-antenna wireless systems, but its implementation is constrained by the cost and complexity of analog phase-shifter (PS) networks. Although sub-connected architectures simplify the analog network, their conventional realization still requires a dedicated PS for each antenna, causing considerable layout area, wiring, calibration, and control overheads. To address this issue, this paper proposes a novel static-connection architecture with sparse PSs for ultra-low-cost sub-connected hybrid beamforming, where antennas within each sub-array share a PS through an optimized fixed PS-to-antenna connection matrix. The proposed architecture preserves static connections while enabling dynamic beam control via adaptive PS phase-shift adjustments and digital precoding. For the single-radio-frequency (RF)-chain scenario, the sparse-PS connection design is transformed into an antenna-grouping problem, with analytically characterized structural properties and an efficient algorithm. For the multi-RF-chain scenario, we develop a quality-of-service (QoS)-majorization-minimization (MM) algorithm to handle the mixed discrete-continuous optimization problem. Numerical results demonstrate that the proposed architecture reduces the PS count while preserving most beamforming capability of the traditional full-PS sub-connected architecture. In particular, the proposed design achieves PS-count reductions of 37.5% and 62.5% in single-RF-chain and multi-RF-chain systems, respectively, while avoiding deep-null and grating-lobe degradations associated with deterministic connection schemes. These results provide engineering insights into static sparse-PS sharing: the key to hardware-efficient hybrid beamforming is not merely reducing the PS count, but also preserving essential analog-domain degrees of freedom through optimized PS connection topologies.