Kefei Liu

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Due to the scarcity of the electromagnetic spectrum, multi-dimensional signaling schemes that take into account several signal dimensions such as space, time, frequency and constellation , are good candidates for increasing the data rate and/or improving the link reliability in future communication systems. Recently a new space-time-frequency diversity(More)
very similar performance of the competing receivers with extra pilot overhead at sufficiently high signal-to-noise ratio (SNR) conditions. On the other hand, it is slightly inferior to them in terms of channel estimation accuracy and bit error rate at lower SNRs.
Both theoretical and experimental studies suggest that response properties in the visual system are shaped by signals in the natural environment. Recent studies showed that, in the primary visual cortex (V1), neurons preferring light decrements (OFF stimuli) outnumber those preferring light increments (ON stimuli). However, it is not clear whether the(More)
A novel R-dimensional (R ≥ 3) model order selection (MOS) criterion is proposed for estimating the number of sources embedded in noise. By extending the classical r-mode matrix unfolding of a Rth-order measurement tensor to multi-mode matrix unfolding, (2 R−1 − 1) unfolded matrices are obtained. To maximize the iden-tifiability, the unfolded matrix whose(More)
a r t i c l e i n f o a b s t r a c t Estimation of the number of signals impinging on an array of sensors, also known as source enumeration, is usually required prior to direction-of-arrival (DOA) estimation. In challenging scenarios such as the presence of closely-spaced sources and/or high level of noise, using the true source number for nonlinear(More)
The responses of visual cortical neurons to natural stimuli are both reliable and sparse. These properties require inhibition, yet the contribution of specific types of inhibitory neurons is not well understood. Here we demonstrate that optogenetic suppression of parvalbumin (PV)- but not somatostatin (SOM)-expressing interneurons reduces response(More)
R-dimensional (R-D) harmonic retrieval (HR) in colored noise, where R Z 2, is required in numerous applications including radar, sonar, mobile communications, multiple-input multiple-output channel estimation and nuclear magnetic resonance spectroscopy. Tensor-based subspace approaches to R-D HR such as R-D unitary ESPRIT and R-D MUSIC provide(More)
Multiclass classification is one of the core problems in many applications. High classification accuracy is fundamental to be accepted as a valuable or even indispensable tool in the work flow. In the classification problem, each sample is usually represented as a vector of features. Most of the cases, some features are usually redundant or misleading, and(More)
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Abstract—Subspace-based high-resolution algorithms for direction-of-arrival estimation have been developed for large-scale adaptive antenna arrays. However, its prerequisite step, namely, source(More)