Wireless Channel Parameter Estimation for Millimeter-Wave Hybrid Beamforming Systems

This paper proposes a sub-antenna array beamsteering-domain channel estimation framework for millimeter-wave (mmWave) systems with hybrid beamforming. Unlike conventional array-domain methods that require access to per-antenna baseband, the proposed approach leverages joint transmitter (Tx) and receiver (Rx) beamsteering observations to enable high-resolution, digital-beamforming-like parameter estimation under practical hardware constraints. A generalized signal model is developed that incorporates measured beam patterns, including sidelobe and phase effects, ensuring a practical representation of hybrid transceivers. Building on this model, we adapt the classical SAGE and MUSIC algorithms to operate in the beamsteering domain, allowing accurate estimation of multipath angle and delay parameters without relying on discretized angular grids. The proposed methods are evaluated through extensive Monte Carlo simulations across different SNR levels, array configurations, and beamsteering resolutions, and are further validated on a 28 GHz hybrid beamforming testbed. Results demonstrate that the beamsteering-based SAGE achieves superior resolution in dense multipath environments, while beamsteering-based MUSIC provides robustness under reduced beamsteering diversity. These findings establish the proposed framework as a practical and effective solution for accurate mmWave channel parameter estimation with hybrid beamforming architectures.