pwc-archive/papers-with-abstracts huggingface dataset:
Interference Exploitation-based Hybrid Precoding with Robustness Against Phase Errors
Date: 2019-07-23 00:00:00

Hybrid analog-digital precoding significantly reduces the hardware costs in
massive MIMO transceivers when compared to fully-digital precoding at the
expense of increased transmit power. In order to mitigate the above shortfall,
we use the concept of constructive interference-based precoding, which has been
shown to offer significant transmit power savings when compared with the
conventional interference suppression-based precoding in fully-digital
multiuser MIMO systems. Moreover, in order to circumvent the potential
quality-of-service degradation at the users due to the hardware impairments in
the transmitters, we judiciously incorporate robustness against such
vulnerabilities in the precoder design. Since the undertaken constructive
interference-based robust hybrid precoding problem is nonconvex with infinite
constraints and thus difficult to solve optimally, we decompose the problem
into two subtasks, namely, analog precoding and digital precoding. In this
paper, we propose an algorithm to compute the optimal constructive
interference-based robust digital precoders. Furthermore, we devise a scheme to
facilitate the implementation of the proposed algorithm in a low-complexity and
distributed manner. We also discuss block-level analog precoding techniques.
Simulation results demonstrate the superiority of the proposed algorithm and
its implementation scheme over the state-of-the-art methods.
Power Allocation for Massive MIMO-based, Fronthaul-constrained Cloud RAN Systems
Date: 2018-10-10 00:00:00

Cloud radio access network (C-RAN) and massive multiple-input-multiple-output
(MIMO) are two key enabling technologies to meet the diverse and stringent
requirements of the 5G use cases. In a C-RAN system with massive MIMO,
fronthaul is often the bottleneck due to its finite capacity and transmit
precoding is moved to the remote radio head to reduce the capacity requirements
on fronthaul. For such a system, we optimize the power allocated to the users
to maximize first the weighted sum rate and then the energy efficiency (EE)
while explicitly incorporating the capacity constraints on fronthaul. We
consider two different fronthaul constraints, which model capacity constraints
on different parts of the fronthaul network. We develop successive convex
approximation algorithms that achieve a stationary point of these non-convex
problems. To this end, we first present novel, locally tight bounds for the
user rate expression. They are used to obtain convex approximations of the
original non-convex problems, which are then solved by solving their dual
problems. In EE maximization, we also employ the Dinkelbach algorithm to handle
the fractional form of the objective function. Numerical results show that the
proposed algorithms significantly improve the network performance compared to a
case with no power control and achieves a better performance than an existing
algorithm.
Receptor crosstalk improves concentration sensing of multiple ligands
Authors: Martin Carballo-Pacheco, Jonathan Desponds, Tatyana Gavrilchenko, Andreas Mayer, Roshan Prizak, Gautam Reddy, Ilya Nemenman, Thierry Mora
Date: 2018-10-10 00:00:00

Cells need to reliably sense external ligand concentrations to achieve various biological functions such as chemotaxis or signaling. The molecular recognition of ligands by surface receptors is degenerate in many systems leading to crosstalk between different receptors. Crosstalk is often thought of as a deviation from optimal specific recognition, as the binding of non-cognate ligands can interfere with the detection of the receptor's cognate ligand, possibly leading to a false triggering of a downstream signaling pathway. Here we quantify the optimal precision of sensing the concentrations of multiple ligands by a collection of promiscuous receptors. We demonstrate that crosstalk can improve precision in concentration sensing and discrimination tasks. To achieve superior precision, the additional information about ligand concentrations contained in short binding events of the non-cognate ligand should be exploited. We present a proofreading scheme to realize an approximate estimation of multiple ligand concentrations that reaches a precision close to the derived optimal bounds. Our results help rationalize the observed ubiquity of receptor crosstalk in molecular sensing.
Building an Ontology for the Domain of Plant Science using Prot\'eg\'e
Authors: Kassani Sara Hosseinzadeh, Kassani Peyman Hosseinzadeh
Date: 2018-10-11 00:00:00
Tasks: Management

Due to the rapid development of technology, large amounts of heterogeneous
data generated every day. Biological data is also growing in terms of the
quantity and quality of data considerably. Despite the attempts for building a
uniform platform to handle data management in Plant Science, researchers are
facing the challenge of not only accessing and integrating data stored in
heterogeneous data sources but also representing the implicit and explicit
domain knowledge based on the available plant genomic and phenomic data.
Ontologies provide a framework for describing the structures and vocabularies
to support the semantics of information and facilitate automated reasoning and
knowledge discovery. In this paper, we focus on building an ontology for
Arabidopsis Thaliana in Plant Science domain. The aim of this study is to
provide a conceptual model of Arabidopsis Thaliana as a reference plant for
botany and other plant sciences, including concepts and their relationships.
Challenges in approximating the Black and Scholes call formula with hyperbolic tangents
Date: 2018-09-20 00:00:00
Tasks: Management

In this paper we introduce the concept of standardized call function and we
obtain a new approximating formula for the Black and Scholes call function
through the hyperbolic tangent. This formula is useful for pricing and risk
management as well as for extracting the implied volatility from quoted
options. The latter is of particular importance since it indicates the risk of
the underlying and it is the main component of the option's price. Further we
estimate numerically the approximating error of the suggested solution and, by
comparing our results in computing the implied volatility with the most common
methods available in literature we discuss the challenges of this approach.
Prices, Profits, Proxies, and Production
Authors: Victor H. Aguiar, Nail Kashaev, Roy Allen
Date: 2018-10-10 00:00:00
Tasks: counterfactual

This paper studies nonparametric identification and counterfactual bounds for heterogeneous firms that can be ranked in terms of productivity. Our approach works when quantities and prices are latent, rendering standard approaches inapplicable. Instead, we require observation of profits or other optimizing-values such as costs or revenues, and either prices or price proxies of flexibly chosen variables. We extend classical duality results for price-taking firms to a setup with discrete heterogeneity, endogeneity, and limited variation in possibly latent prices. Finally, we show that convergence results for nonparametric estimators may be directly converted to convergence results for production sets.
Alternative stable states in a model of microbial community limited by multiple essential nutrients
Date: 2018-10-10 00:00:00

Microbial communities routinely have several alternative stable states
observed for the same environmental parameters. Sudden and irreversible
transitions between these states make external manipulation of these systems
more complicated. To better understand the mechanisms and origins of
multistability in microbial communities, we introduce and study a model of a
microbial ecosystem colonized by multiple specialist species selected from a
fixed pool. Growth of each species can be limited by essential nutrients of two
types, e.g. carbon and nitrogen, each represented in the environment by
multiple metabolites. We demonstrate that our model has an exponentially large
number of potential stable states realized for different environmental
parameters. Using game theoretical methods adapted from the stable marriage
problem we predict all of these states based only on ranked lists of
competitive abilities of species for each of the nutrients. We show that for
every set of nutrient influxes, several mutually uninvadable stable states are
generally feasible and we distinguish them based upon their dynamic stability.
We further explore an intricate network of discontinuous transitions (regime
shifts) between these alternative states both in the course of community
assembly, or upon changes of nutrient influxes.
Deriving the factor endowment--commodity output relationship for Thailand (1920-1927) using a three-factor two-good general equilibrium trade model
Date: 2018-10-11 00:00:00

Feeny (1982, pp. 26-28) referred to a three-factor two-good general
equilibrium trade model, when he explained the relative importance of trade and
factor endowments in Thailand 1880-1940. For example, Feeny (1982) stated that
the growth in labor stock would be responsible for a substantial increase in
rice output relative to textile output. Is Feeny's statement plausible? The
purpose of this paper is to derive the Rybczynski sign patterns, which express
the factor endowment--commodity output relationship, for Thailand during the
period 1920 to 1927 using the EWS (economy-wide substitution)-ratio vector. A
'strong Rybczynski result' necessarily holds. I derived three Rybczynski sign
patterns. However, a more detailed estimate allowed a reduction from three
candidates to two. I restrict the analysis to the period 1920-1927 because of
data availability. The results imply that Feeny's statement might not
necessarily hold. Hence, labor stock might not affect the share of exportable
sector in national income positively. Moreover, the percentage of Chinese
immigration in the total population growth was not as large as expected. This
study will be useful when simulating real wage in Thailand.
A Comparison of CP-OFDM, PCC-OFDM and UFMC for 5G Uplink Communications
Date: 2018-10-11 00:00:00

Polynomial-cancellation-coded orthogonal frequency division multiplexing
(PCC-OFDM) is a form of OFDM that has waveforms which are very well localized
in both the time and frequency domains and so it is ideally suited for use in
the 5G network. This paper analyzes the performance of PCC-OFDM in the uplink
of a multiuser system using orthogonal frequency division multiple access
(OFDMA) and compares it with conventional cyclic prefix OFDM (CP-OFDM), and
universal filtered multicarrier (UFMC). PCC-OFDM is shown to be much less
sensitive than either CP-OFDM or UFMC to time and frequency offsets. For a
given constellation size, PCC-OFDM in additive white Gaussian noise (AWGN)
requires 3dB lower signal-to-noise ratio (SNR) for a given bit-error-rate, and
the SNR advantage of PCC-OFDM increases rapidly when there are timing and/or
frequency offsets. For PCC-OFDM no frequency guard band is required between
different OFDMA users. PCC-OFDM is completely compatible with CP-OFDM and adds
negligible complexity and latency, as it uses a simple mapping of data onto
pairs of subcarriers at the transmitter, and a simple weighting-and-adding of
pairs of subcarriers at the receiver. The weighting and adding step, which has
been omitted in some of the literature, is shown to contribute substantially to
the SNR advantage of PCC-OFDM. A disadvantage of PCC-OFDM (without overlapping)
is the potential reduction in spectral efficiency because subcarriers are
modulated in pairs, but this reduction is more than regained because no guard
band or cyclic prefix is required and because, for a given channel, larger
constellations can be used.
Regulatory Options and Technical Challenges for the 5.9 GHz Spectrum: Survey and Analysis
Date: 2018-10-11 00:00:00

In 1999, the Federal Communications Commission (FCC) allocated 75 MHz in the
5.9 GHz ITS Band (5850-5925 MHz) for use by Dedicated Short Range
Communications (DSRC) to facilitate information transfer between equipped
vehicles and roadside systems. This allocation for DSRC in the ITS band has
been a co-primary allocation while the band is shared with the Fixed Satellite
Service (FSS), fixed microwave service, amateur radio services and other
Federal users authorized by the National Telecommunications and Information
Administration (NTIA). In recent time, Cellular V2X (C-V2X), introduced in 3GPP
Release 14 LTE standard, has received significant attention due to its
perceived ability to deliver superior performance with respect to vehicular
safety applications. There is a strong momentum in the industry for C-V2X to be
considered as a viable alternative to DSRC and accordingly, to operate in the
ITS spectrum. In another recent notice, the FCC is soliciting input for a
proposed rulemaking to open up more bandwidth for unlicensed Wi-Fi devices,
mainly based on the 802.11ac standard. The FCC plans to work with the
Department of Transportation (DoT), and the automotive and communications
industries to evaluate potential sharing techniques in the ITS band between
DSRC and Wi-Fi devices. This paper analyzes the expected scenarios that might
emerge from FCC and the National Highway Traffic Safety Administration (NHTSA)
regulation options and identifies the technical challenge associated with each
scenario. We also provide a literature survey and find that many of resulting
technical challenges remain open research problems that need to be addressed.
We conclude that the most challenging issue is related to the interoperability
between DSRC and C-V2X in the 5.9 GHz band and the detection and avoidance of
harmful adjacent and co-channel interference.
Lifting the Heston model
Date: 2019-11-22 00:00:00
Tasks: model

How to reconcile the classical Heston model with its rough counterpart? We
introduce a lifted version of the Heston model with n multi-factors, sharing
the same Brownian motion but mean reverting at different speeds. Our model
nests as extreme cases the classical Heston model (when n = 1), and the rough
Heston model (when n goes to infinity). We show that the lifted model enjoys
the best of both worlds: Markovianity and satisfactory fits of implied
volatility smiles for short maturities with very few parameters. Further, our
approach speeds up the calibration time and opens the door to time-efficient
simulation schemes.
Time consistency for scalar multivariate risk measures
Authors: Zachary Feinstein, Birgit Rudloff
Date: 2018-10-11 00:00:00

In this paper we present results on dynamic multivariate scalar risk measures, which arise in markets with transaction costs and systemic risk. Dual representations of such risk measures are presented. These are then used to obtain the main results of this paper on time consistency; namely, an equivalent recursive formulation of multivariate scalar risk measures to multiportfolio time consistency. We are motivated to study time consistency of multivariate scalar risk measures as the superhedging risk measure in markets with transaction costs (with a single eligible asset) (Jouini and Kallal (1995), Roux and Zastawniak (2016), Loehne and Rudloff (2014)) does not satisfy the usual scalar concept of time consistency. In fact, as demonstrated in (Feinstein and Rudloff (2021)), scalar risk measures with the same scalarization weight at all times would not be time consistent in general. The deduced recursive relation for the scalarizations of multiportfolio time consistent set-valued risk measures provided in this paper requires consideration of the entire family of scalarizations. In this way we develop a direct notion of a "moving scalarization" for scalar time consistency that corroborates recent research on scalarizations of dynamic multi-objective problems (Karnam, Ma, and Zhang (2017), Kovacova and Rudloff (2021)).
Analytical Formulations for the Level Based Weighted Average Value of Discrete Trapezoidal Fuzzy Numbers
Authors: Nasiboglu Resmiye, Abdullayeva Rahila
Date: 2018-09-13 00:00:00
Tasks: Decision Making

In fuzzy decision-making processes based on linguistic information,
operations on discrete fuzzy numbers are commonly performed. Aggregation and
defuzzification operations are some of these often used operations. Many
aggregation and defuzzification operators produce results independent to the
decision makers strategy. On the other hand, the Weighted Average Based on
Levels (WABL) approach can take into account the level weights and the decision
makers optimism strategy. This gives flexibility to the WABL operator and,
through machine learning, can be trained in the direction of the decision
makers strategy, producing more satisfactory results for the decision maker.
However, in order to determine the WABL value, it is necessary to calculate
some integrals. In this study, the concept of WABL for discrete trapezoidal
fuzzy numbers is investigated, and analytical formulas have been proven to
facilitate the calculation of WABL value for these fuzzy numbers. Trapezoidal
and their special form, triangular fuzzy numbers, are the most commonly used
fuzzy number types in fuzzy modeling, so in this study, such numbers have been
studied. Computational examples explaining the theoretical results have been
performed.
The Human Cell Atlas White Paper
Date: 2018-10-11 00:00:00

The Human Cell Atlas (HCA) will be made up of comprehensive reference maps of
all human cells - the fundamental units of life - as a basis for understanding
fundamental human biological processes and diagnosing, monitoring, and treating
disease. It will help scientists understand how genetic variants impact disease
risk, define drug toxicities, discover better therapies, and advance
regenerative medicine. A resource of such ambition and scale should be built in
stages, increasing in size, breadth, and resolution as technologies develop and
understanding deepens. We will therefore pursue Phase 1 as a suite of flagship
projects in key tissues, systems, and organs. We will bring together experts in
biology, medicine, genomics, technology development and computation (including
data analysis, software engineering, and visualization). We will also need
standardized experimental and computational methods that will allow us to
compare diverse cell and tissue types - and samples across human communities -
in consistent ways, ensuring that the resulting resource is truly global.
  This document, the first version of the HCA White Paper, was written by
experts in the field with feedback and suggestions from the HCA community,
gathered during recent international meetings. The White Paper, released at the
close of this yearlong planning process, will be a living document that evolves
as the HCA community provides additional feedback, as technological and
computational advances are made, and as lessons are learned during the
construction of the atlas.
Iterative Time-Varying Filter Algorithm Based on Discrete Linear Chirp Transform
Date: 2018-10-11 00:00:00
Tasks: Denoising

Denoising of broadband non--stationary signals is a challenging problem in
communication systems. In this paper, we introduce a time-varying filter
algorithm based on the discrete linear chirp transform (DLCT), which provides
local signal decomposition in terms of linear chirps. The method relies on the
ability of the DLCT for providing a sparse representation to a wide class of
broadband signals. The performance of the proposed algorithm is compared with
the discrete fractional Fourier transform (DFrFT) filtering algorithm.
Simulation results show that the DLCT algorithm provides better performance
than the DFrFT algorithm and consequently achieves high quality filtering.
Offline Comparison of Ranking Functions using Randomized Data
Authors: Agarwal Aman, Wang Xuanhui, Li Cheng, Bendersky Michael, Najork Marc
Date: 2018-10-11 00:00:00
Tasks: Off-policy evaluation

Ranking functions return ranked lists of items, and users often interact with
these items. How to evaluate ranking functions using historical interaction
logs, also known as off-policy evaluation, is an important but challenging
problem. The commonly used Inverse Propensity Scores (IPS) approaches work
better for the single item case, but suffer from extremely low data efficiency
for the ranked list case. In this paper, we study how to improve the data
efficiency of IPS approaches in the offline comparison setting. We propose two
approaches Trunc-match and Rand-interleaving for offline comparison using
uniformly randomized data. We show that these methods can improve the data
efficiency and also the comparison sensitivity based on one of the largest
email search engines.
A Novel Chaotic Uniform Quantizer for Speech Coding
Date: 2018-10-11 00:00:00
Tasks: Data Compression, Quantization

Quantization is an essential step in the analog-to-digital conversion process
and it is very important in all modern telecommunication systems. In this
paper, a novel chaotic uniform quantizer is proposed and its application for
speech coding is presented. The proposed system consists of three stages: two
PCM coders separated by an XOR operation with a chaotic sequence, where the
first step is used for continuous signal sampling and second stage performs
data encryption, while the third stage provides additional data compression.
The performance of the presented quantizer for Laplacian distributed signals
and real speech signals is investigated and compared with that of the
well-known uniform and non-uniform quantizers. Simulation results show that the
proposed quantizer provides secured data with higher levels of SQNR compared to
others.
Combined Image Encryption and Steganography Algorithm in the Spatial Domain
Date: 2018-10-11 00:00:00

In recent years, steganography has emerged as one of the main research areas
in information security. Least significant bit (LSB) steganography is one of
the fundamental and conventional spatial domain methods, which is capable of
hiding larger secret information in a cover image without noticeable visual
distortions. In this paper, a combined algorithm based on LSB steganography and
chaotic encryption is proposed. Experimental results show the feasibility of
the proposed method. In comparison with existing steganographic spatial domain
based algorithms, the suggested algorithm is shown to have some advantages over
existing ones, namely, larger key space and a higher level of security against
some existing attacks.
Instantaneous frequency estimation using the discrete linear chirp transform and the Wigner distribution
Date: 2018-10-11 00:00:00

In this paper, we propose a new method to estimate instantaneous frequency
using a combined approach based on the discrete linear chirp transform (DLCT)
and the Wigner distribution (WD). The DLCT locally represents a signal as a
superposition of linear chirps while the WD provides maximum energy
concentration along the instantaneous frequency in the time-frequency domain
for each of the chirps. The developed approach takes advantage of the
separation of the linear chirps given by the DLCT, and that for each of them,
the WD provides an ideal representation. Combining the WD of the linear chirp
components, we obtain a time-frequency representation free of cross-terms that
clearly displays the instantaneous frequency. Applying this procedure locally,
we obtain an instantaneous frequency estimate of a non-stationary
multicomponent signal. The proposed method is illustrated by simulation. The
results indicate the method is efficient for the instantaneous frequency
estimation of multicomponent signals embedded in noise, even in cases of low
signal to noise ratio.