Hierarchical beamforming strategies for source detection with linear arrays at 26 GHz

The present work investigates hierarchical beamforming strategies for millimeter-wave communication systems, focusing on amplitude tapering and sub-array approaches. The research addresses key challenges in Angle of Arrival (AoA) estimation and beam management, essential for next-generation wireless networks. The tapering-based method, implemented on a 4-element linear array, demonstrated precise beamwidth and sidelobe control, enabling hierarchical search strategies with reduced implementation effort. Experimental validation confirmed its effectiveness in identifying transmission directions under line-of-sight conditions; however, its reliance on full-array activation made it less energy-efficient and more sensitive to multipath-induced errors in reflective environments. Conversely, the sub-array approach, applied to an 8-element linear array, showcased enhanced robustness against multipath effects and quantifiable power savings. By activating only a subset of elements at each search level, this method achieved an estimated 42% reduction in average power per configuration and significantly fewer beam evaluations than exhaustive search. Its hierarchical adaptability supported efficient AoA estimation with balanced energy demands. The Rician K-factor analysis validated its suitability for line-of-sight-dominated environments. Comparative results revealed that while tapering achieves high angular resolution, it requires precise amplitude control and is less resilient to multipath. The sub-array technique, though less effective in sidelobe suppression, offers superior scalability, flexibility, and energy efficiency, making it a practical choice for real-world millimeter-wave systems. This work highlights the potential of hierarchical codebook designs in optimizing beamforming performance, training efficiency, execution time, and power consumption for millimeter-wave communications.