ESPRIT-Type Algorithms in Oversampled DFT Beamspace and Their Performance Analysis

Accurate direction-of-arrival (DoA) estimation is beneficial in array signal processing and directional wireless communications, where improving the spatial resolution is a key challenge. This paper proposes an oversampled discrete Fourier transform (DFT) beamspace framework combined with ESPRIT-type algorithms. By formulating the generalized shift-invariance equations with an arbitrary integer oversampling factor, the proposed DFT-O-UESPRIT algorithm enables high oversampling factor processing and improves the spatial focusing capability of DFT beams. Furthermore, we derive a first-order asymptotic performance analysis for the proposed DFT-O-UESPRIT algorithm to examine its effectiveness. The resulting analytical expressions for the parameter estimation errors hold in the high effective signal-to-noise ratio (SNR) or large-sample-size regime. Notably, these expressions provide theoretical support for resolution enhancement in oversampled beamspace. Numerical simulations validate the theoretical expressions and demonstrate that the proposed approach outperforms both conventional antenna space Unitary ESPRIT and non-oversampled DFT beamspace Unitary ESPRIT, particularly under low SNR conditions and with closely spaced sources.