148 research outputs found
NoncovANM: Gridless DOA Estimation for LPDF System
Direction of arrival (DOA) estimation is an important research in the area of
array signal processing, and has been studied for decades. High resolution DOA
estimation requires large array aperture, which leads to the increase of
hardware cost. Besides, high accuracy DOA estimation methods usually have high
computational complexity. In this paper, the problem of decreasing the hardware
cost and algorithm complexity is addressed. First, considering the ability of
flexible controlling the electromagnetic waves and low-cost, an intelligent
reconfigurable surface (IRS)-aided low-cost passive direction finding (LPDF)
system is developed, where only one fully functional receiving channel is
adopted. Then, the sparsity of targets direction in the spatial domain is
exploited by formulating an atomic norm minimization (ANM) problem to estimate
the DOA. Traditionally, solving ANM problem is complex and cannot be realized
efficiently. Hence, a novel nonconvex-based ANM (NC-ANM) method is proposed by
gradient threshold iteration, where a perturbation is introduced to avoid
falling into saddle points. The theoretical analysis for the convergence of the
NC-ANM method is also given. Moreover, the corresponding Cram\'er-Rao lower
bound (CRLB) in the LPDF system is derived, and taken as the referred bound of
the DOA estimation. Simulation results show that the proposed method
outperforms the compared methods in the DOA estimation with lower computational
complexity in the LPDF system.Comment: 11 pages, 8 figure
Realistic Volume Rendering with Environment-Synced Illumination in Mixed Reality
Interactive volume visualization using a mixed reality (MR) system helps
provide users with an intuitive spatial perception of volumetric data. Due to
sophisticated requirements of user interaction and vision when using MR
head-mounted display (HMD) devices, the conflict between the realisticness and
efficiency of direct volume rendering (DVR) is yet to be resolved. In this
paper, a new MR visualization framework that supports interactive realistic DVR
is proposed. An efficient illumination estimation method is used to identify
the high dynamic range (HDR) environment illumination captured using a panorama
camera. To improve the visual quality of Monte Carlo-based DVR, a new
spatio-temporal denoising algorithm is designed. Based on a reprojection
strategy, it makes full use of temporal coherence between adjacent frames and
spatial coherence between the two screens of an HMD to optimize MR rendering
quality. Several MR development modules are also developed for related devices
to efficiently and stably display the DVR results in an MR HMD. Experimental
results demonstrate that our framework can better support immersive and
intuitive user perception during MR viewing than existing MR solutions.Comment: 6 pages, 6 figure
URGLQ: An Efficient Covariance Matrix Reconstruction Method for Robust Adaptive Beamforming
The computational complexity of the conventional adaptive beamformer is
relatively large, and the performance degrades significantly due to both the
model mismatch errors and the unwanted signals in received data. In this paper,
an efficient unwanted signal removal and Gauss-Legendre quadrature
(URGLQ)-based covariance matrix reconstruction method is proposed. Different
from the prior covariance matrix reconstruction methods, a projection matrix is
constructed to remove the unwanted signal from the received data, which
improves the reconstruction accuracy of the covariance matrix. Considering that
the computational complexity of most matrix reconstruction algorithms are
relatively large due to the integral operation, we proposed a Gauss-Legendre
quadrature-based method to approximate the integral operation while maintaining
the accuracy. Moreover, to improve the robustness of the beamformer, the
mismatch in the desired steering vector is corrected by maximizing the output
power of the beamformer under a constraint that the corrected steering vector
cannot converge to any interference steering vector. Simulation results and
prototype experiment demonstrate that the performance of the proposed
beamformer outperforms the compared methods and is much closer to the optimal
beamformer in different scenarios.Comment: 11 pages, 16 figure
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