14 research outputs found
Interpolation of Sparse Graph Signals by Sequential Adaptive Thresholds
This paper considers the problem of interpolating signals defined on graphs.
A major presumption considered by many previous approaches to this problem has
been lowpass/ band-limitedness of the underlying graph signal. However,
inspired by the findings on sparse signal reconstruction, we consider the graph
signal to be rather sparse/compressible in the Graph Fourier Transform (GFT)
domain and propose the Iterative Method with Adaptive Thresholding for Graph
Interpolation (IMATGI) algorithm for sparsity promoting interpolation of the
underlying graph signal.We analytically prove convergence of the proposed
algorithm. We also demonstrate efficient performance of the proposed IMATGI
algorithm in reconstructing randomly generated sparse graph signals. Finally,
we consider the widely desirable application of recommendation systems and show
by simulations that IMATGI outperforms state-of-the-art algorithms on the
benchmark datasets in this application.Comment: 12th International Conference on Sampling Theory and Applications
(SAMPTA 2017
Feedback Acquisition and Reconstruction of Spectrum-Sparse Signals by Predictive Level Comparisons
In this letter, we propose a sparsity promoting feedback acquisition and
reconstruction scheme for sensing, encoding and subsequent reconstruction of
spectrally sparse signals. In the proposed scheme, the spectral components are
estimated utilizing a sparsity-promoting, sliding-window algorithm in a
feedback loop. Utilizing the estimated spectral components, a level signal is
predicted and sign measurements of the prediction error are acquired. The
sparsity promoting algorithm can then estimate the spectral components
iteratively from the sign measurements. Unlike many batch-based Compressive
Sensing (CS) algorithms, our proposed algorithm gradually estimates and follows
slow changes in the sparse components utilizing a sliding-window technique. We
also consider the scenario in which possible flipping errors in the sign bits
propagate along iterations (due to the feedback loop) during reconstruction. We
propose an iterative error correction algorithm to cope with this error
propagation phenomenon considering a binary-sparse occurrence model on the
error sequence. Simulation results show effective performance of the proposed
scheme in comparison with the literature
MU-Massive MIMO with Multiple RISs: SINR Maximization and Asymptotic Analysis
In this letter, we investigate the signal-to-interference-plus-noise-ratio
(SINR) maximization problem in a multi-user massive
multiple-input-multiple-output (massive MIMO) system enabled with multiple
reconfigurable intelligent surfaces (RISs). We examine two zero-forcing (ZF)
beamforming approaches for interference management namely BS-UE-ZF and
BS-RIS-ZF that enforce the interference to zero at the users (UEs) and the
RISs, respectively.Then, for each case, we resolve the SINR maximization
problem to find the optimal phase shifts of the elements of the RISs. Also, we
evaluate the asymptotic expressions for the optimal phase shifts and the
maximum SINRs when the number of the base station (BS) antennas tends to
infinity. We show that if the channels of the RIS elements are independent and
the number of the BS antennas tends to infinity, random phase shifts achieve
the maximum SINR using the BS-UE-ZF beamforming approach. The simulation
results illustrate that by employing the BS-RIS-ZF beamforming approach, the
asymptotic expressions of the phase shifts and maximum SINRs achieve the rate
obtained by the optimal phase shifts even for a small number of the BS
antennas.Comment: Accepted for publication in IEEE Wireless Communications Letter