Abstract
As an emerging technology, the hybrid analog-digital structure has been considered for use in future millimeter-wave communications. Although this structure can reduce the hardware cost and power consumption considerably, the spatial covariance matrix (SCM), as the core of subspace-based direction of arrival (DOA) estimation, cannot be obtained directly. Previously, the beam sweeping algorithm (BSA) has been found effective for reconstructing the spatial covariance matrix and realizing DOA estimation by forming the beams to difference directions. However, it is computationally intractable owing to the high-dimensional matrix operation. To address this problem and improve the DOA estimation performance, this paper applies the nested array to the hybrid analog-digital structure and proposes the enhanced BSA (EBSA) for DOA estimation. By deleting a large number of redundant elements exist in the SCM to be reconstructed, the computational cost can be considerably reduced. Also, the nested array can offer high degrees of freedom. Finally, simulation experiments are conducted to verify the performance of EBSA. The results indicate that the proposed EBSA is better than the state-of-the-art method in terms of estimation accuracy and computational cost.
Highlights
As an emerging technology, the hybrid analog-digital structure has been considered for use in future millimeter-wave communications
As for the proposed enhanced BSA (EBSA), the maximum number of signals that can be realized on direction of arrival (DOA) estimation is N2(N1 + 1) − 1, while it is N − 1 for the original beam sweeping algorithm (BSA) based on the uniform linear array with N elements
To ensure the accuracy of the estimation, the number of predetermined DOA angles is set to N(N − 1) when the number of antennas is set to N for both EBSA and BSA
Summary
The signal model of the hybrid analog-digital structure with nested array is shown in Fig. 1, where one radio frequency chain is connected to multiple antennas. The signal model of the hybrid analog-digital structure with nested array is shown, where one radio frequency chain is connected to multiple antennas. E−j2πpN d sin(θk)/ ]T represents the steering vector for the incident angle of θk , sk(t) denotes K narrow-band signals impinging from far field onto the array, ε(t) denotes the Gaussian white noise and []T represents the transpose. Since one radio frequency chain is connected to multiple antennas in the hybrid analog-digital structure, y(t) is unknown to the digital receiver. After R is obtained, the MUSIC algorithm can be applied to the hybrid analog-digital structure to achieve the DOA of each signal. Providing low computational cost and high degrees of freedoms for DOA estimation, the proposed EBSA based on the hybrid analog-digital structure with nested array will be described in detail as follows
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