Composite Digital-Analog Beamforming Architecture for 6G Upper-Mid Band User Equipment

초록

This letter proposes a form-factor-aware composite beamforming architecture for 6G Upper-Mid Band (UMB) user equipment. By synergistically integrating a digital metal-frame sub-array with an analog phased array module, the system optimizes the balance between coverage and multiplexing gain under strict hardware constraints. We derive a closed-form optimal analog combining vector using an effective channel metric that rigorously accounts for inter-stream interference. The proposed solution is proven equivalent to the interference-aware MMSE (IA-MMSE), while the traditional independent MMSE degenerates to independent matched filtering (Ind-MF). Asymptotic analysis reveals dynamic adaptation, converging to Ind-MF behavior in noise-limited regimes and to interference-aware zero-forcing (IA-ZF) behavior in interference-limited regimes. Simulations under a heterogeneous channel model with transmitter-side water-filling show spectral efficiency comparable to full-digital systems with markedly reduced RF complexity, outperforming conventional hybrid baselines.

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