pinecone/core-2020-05-10-deduplication huggingface dataset:
Spectral and Energy Efficient Cognitive Radio Aided Heterogeneous Cellular Network with Uplink Power Adaptation

In future heterogeneous cellular networks (HCN), cognitive radio (CR) compatible with device to device communication (D2D) technique can be an aid to further enhance system spectral and energy efficiency. The unlicensed smart devices (SDs) are allowed to detect the available licensed spectrum and utilise the spectrum resource which is detected as not being used by the licensed users (LUs). In this work, we propose such a system and provide comprehensive analysis of the effect of selection of SDs’ frame structure on the energy efficiency, throughput and interference. Moreover, uplink power control strategy is also considered where the LUs and SDs adapt the transmit power based on the distance from their reference receivers. The optimal frame structure with power control is investigated under high SNR and low SNR network environments. The impact of power control and optimal sensing time and frame length, on the achievable energy efficiency, throughput and interference are illustrated and analysed by simulation results. It has been also shown that the optimal sensing time and frame length which maximizes the energy efficiency of SDs strictly depends on the power control factor employed in the underlying network such that the considered power control strategy may decrease the energy efficiency of SDs under very low SNR regime
Using Network Coding to Achieve the Capacity of Deterministic Relay
  Networks with Relay Messages

In this paper, we derive the capacity of the deterministic relay networks
with relay messages. We consider a network which consists of five nodes, four
of which can only communicate via the fifth one. However, the fifth node is not
merely a relay as it may exchange private messages with the other network
nodes. First, we develop an upper bound on the capacity region based on the
notion of a single sided genie. In the course of the achievability proof, we
also derive the deterministic capacity of a 4-user relay network (without
private messages at the relay). The capacity achieving schemes use a
combination of two network coding techniques: the Simple Ordering Scheme (SOS)
and Detour Schemes (DS). In the SOS, we order the transmitted bits at each user
such that the bi-directional messages will be received at the same channel
level at the relay, while the basic idea behind the DS is that some parts of
the message follow an indirect path to their respective destinations. This
paper, therefore, serves to show that user cooperation and network coding can
enhance throughput, even when the users are not directly connected to each
other.Comment: 12 pages, 5 figures, submitted to IEEE JSAC Network codin
Differential Modulation for Asynchronous Two-Way-Relay Systems over
  Frequency-Selective Fading Channels

In this paper, we propose two schemes for asynchronous multi-relay two-way
relay (MR-TWR) systems in which neither the users nor the relays know the
channel state information (CSI). In an MR-TWR system, two users exchange their
messages with the help of $N_R$ relays. Most of the existing works on MR-TWR
systems based on differential modulation assume perfect symbol-level
synchronization between all communicating nodes. However, this assumption is
not valid in many practical systems, which makes the design of differentially
modulated schemes more challenging. Therefore, we design differential
modulation schemes that can tolerate timing misalignment under
frequency-selective fading. We investigate the performance of the proposed
schemes in terms of either probability of bit error or pairwise error
probability. Through numerical examples, we show that the proposed schemes
outperform existing competing solutions in the literature, especially for high
signal-to-noise ratio (SNR) values
Robust Secret Key Extraction from Channel Secondary Random Process

The vast majority of existing secret key generation protocols exploit the inherent randomness of the wireless channel as a common source of randomness. However, independent noise added at the receivers of the legitimate nodes affect the reciprocity of the channel. In this paper, we propose a new simple technique to generate the secret key that mitigates the effect of noise. Specifically, we exploit the estimated channel to generate a secondary random process (SRP) that is common between the two legitimate nodes. We compare the estimated channel gain and phase to a preset threshold. The moving differences between the locations at which the estimated channel gain and phase exceed the threshold are the realization of our SRP. We study the properties of our generated SRP and derive a closed form expression for the probability mass function of the realizations of our SRP. We simulate an orthogonal frequency division multiplexing (OFDM) system and show that our proposed technique provides a drastic improvement in the key bit mismatch rate (BMR) between the legitimate nodes when compared to the techniques that exploit the estimated channel gain or phase directly. In addition to that, the secret key generated through our technique is longer than that generated by conventional techniques. Moreover, we compute the conditional probabilities used to estimate the secret key capacit
Subcarrier grouping with environmental sensing for MIMO-OFDM systems
  over correlated double-selective fading channels

With the increase of physical antenna and subcarrier numbers in MIMO-OFDM
systems, channel side information feedback amount and signal precoding
complexity overburden will consume much more system resource, even become
intolerable. To solve this problem, previous works mainly focused on fixed
subcarrier grouping size and precoded MIMO signals in the same group with
unitary channel state information (CSI). It could reduce the system overburden,
but such a process would lead to system capacity loss due to the channel
mismatch in precoding procedure. In this paper, we consider a MIMOOFDM system
over double-selective i.i.d. Rayleigh channels and investigate the quantitative
relation between group size and capacity loss theoretically. By exploiting our
developed theoretical results, we also propose an adaptive subcarrier grouping
algorithm, which not only enables to have a good control of system service
quality but also to reduce system overburden significantly. Numerical results
are shown to provide valuable insights on the system design of MIMO-OFDM
systems and indicate that the proposed subcarrier grouping scheme is extremely
efficient in some common scenarios.Comment: 30 pages, 9 figures, journal versio
Implementation Aspects of a Transmitted-Reference UWB Receiver

In this paper, we discuss the design issues of an ultra wide band (UWB) receiver targeting a single-chip CMOS implementation for low data-rate applications like ad hoc wireless sensor networks. A non-coherent transmitted reference (TR) receiver is chosen because of its small complexity compared to other architectures. After a brief recapitulation of the UWB fundamentals and a short discussion on the major differences between coherent and non-coherent receivers, we discuss issues, challenges and possible design solutions. Several simulation results obtained by means of a behavioral model are presented, together with an analysis of the trade-off between performance and complexity in an integrated circuit implementation
Software-only TDOA/RTF positioning for 3G WCDMA wireless network

A hybrid location finding technique based oil time difference of arrival (TDOA) with round-trip time (RTT) measurements is proposed for a wideband code division Multiple access (WCDMA) network. In this technique, a mobile station measures timing from at least three base stations using user equipment receive-transmit (UE Rx-Tx) time difference and at least three base stations measure timing from the mobile station using RTT. The timing measurements of mobile and base stations are then combined to solve for both the location of the mobile and the synchronization offset between base stations. A software-only geolocation system based on the above mobile/base stations timing measurements is implemented in Matlab platform and the performance of the system is investigated using large-scale propagation models
On the problems of symbol-spaced tapped-delay-line models for WSSUS channels

Article from the journal: Wireless Communications and Mobile Computing

The deposited fulltext is a preprint of the definitive article at Wiley Interscience  
http://dx.doi.org/10.1002/wcm.683This paper analyzes the validity and statistical behavior of symbol-spaced tapped-delay-line (SSTDL) models for wide-sense stationary uncorrelated scattering (WSSUS) mobile radio channels. SSTDL models are obtained by sampling the channel impulse response (CIR) in delay domain at a rate equal to the reciprocal of the symbol duration. They were proposed more than four decades ago as canonical channel models for band-limited timevariant linear (TVL) systems, and are nowadays widely in use for assessing the performance of several wireless communication systems. The applicability of these tapped-delay-line (TDL) models seems to be unquestionable, as they were developed in the framework of the sampling theorem. Nonetheless, we show here that SSTDL models should be used with care to model WSSUS channels, because the channel's uncorrelated scattering (US) condition might easily be violated. Furthermore, we show that SSTDL models suffer from strong limitations in emulating the channel frequency correlation funcion (FCF). This drawback leads to an inaccurate performance evaluation of wireless communication systems sensitive to the FCF. To cope with this problem, we present a simple solution by doubling the channel's sampling rate. The benefits of this solution are demonstrated with some exemplary simulation results. © 2008 John Wiley & Sons, Ltd
Scheduling for next generation WLANs: filling the gap between offered and observed data rates

In wireless networks, opportunistic scheduling is used to increase system throughput by exploiting multi-user diversity. Although recent advances have increased physical layer data rates supported in wireless local area networks (WLANs), actual throughput realized are significantly lower due to overhead. Accordingly, the frame aggregation concept is used in next generation WLANs to improve efficiency. However, with frame aggregation, traditional opportunistic schemes are no longer optimal. In this paper, we propose schedulers that take queue and channel conditions into account jointly, to maximize throughput observed at the users for next generation WLANs. We also extend this work to design two schedulers that perform block scheduling for maximizing network throughput over multiple transmission sequences. For these schedulers, which make decisions over long time durations, we model the system using queueing theory and determine users' temporal access proportions according to this model. Through detailed simulations, we show that all our proposed algorithms offer significant throughput improvement, better fairness, and much lower delay compared with traditional opportunistic schedulers, facilitating the practical use of the evolving standard for next generation wireless networks
Performance analysis of DSRC priority mechanism for road safety applications in vehicular networks

Dedicated short range communications (DSRC) has been regarded as one of the most promising technologies to provide robust communications for large scale vehicle networks. It is designed to support both road safety and commercial applications. Road safety applications will require reliable and timely wireless communications. However, as the medium access control (MAC) layer of DSRC is based on the IEEE 802.11 distributed coordination function (DCF), it is well known that the random channel access based MAC cannot provide guaranteed quality of services (QoS). It is very important to understand the quantitative performance of DSRC, in order to make better decisions on its adoption, control, adaptation, and improvement. In this paper, we propose an analytic model to evaluate the DSRC-based inter-vehicle communication. We investigate the impacts of the channel access parameters associated with the different services including arbitration inter-frame space (AIFS) and contention window (CW). Based on the proposed model, we analyze the successful message delivery ratio and channel service delay for broadcast messages. The proposed analytical model can provide a convenient tool to evaluate the inter-vehicle safety applications and analyze the suitability of DSRC for road safety applications
Per-user service model for opportunistic scheduling scheme over fading channels

In this paper, we propose a ¯nite-state Markov model for per-user service of an oppor- tunistic scheduling scheme over Rayleigh fading channels, where a single base station serves an arbitrary number of users. By approximating the power gain of Rayleigh fading chan- nels as ¯nite-state Markov processes, we develop an algorithm to obtain dynamic stochastic model of the transmission service, received by an individual user for a saturated scenario, where user data queues are highly loaded. The proposed analytical model is a ¯nite-state Markov process. We provide a comprehensive comparison between the predicted results by the proposed analytical model and the simulation results, which demonstrate a high degree of match between the two sets
An infrastructure for detecting and punishing malicious hosts using mobile agent watermarking

Mobile agents are software entities consisting of code, data, and state that can migrate autonomously from host to host\ud
executing their code. In such scenario there are some security issues that must be considered. In particular, this paper deals\ud
with the protection of mobile agents against manipulation attacks performed by the host, which is one of the main security\ud
issues to solve in mobile agent systems. This paper introduces an infrastructure for mobile agent watermarking (MAW).\ud
MAW is a lightweight approach that can efficiently detect manipulation attacks performed by potentially malicious hosts\ud
that might seek to subvert the normal agent operation. MAW is the first proposal in the literature that adapts software\ud
watermarks to verify the execution integrity of an agent. The second contribution of this paper is a technique to punish a\ud
malicious host that performed a manipulation attack by using a trusted third party (TTP) called host revocation authority\ud
(HoRA). A proof-of-concept has also been developed and we present some performance evaluation results that demonstrate\ud
the usability of the proposed mechanisms.Postprint (published version
CP2K: Atomistic simulations of condensed matter systems

cp2k has become a versatile open-source tool for the simulation of complex systems on the nanometer scale. It allows for sampling and exploring potential energy surfaces that can be computed using a variety of empirical and first principles models. Excellent performance for electronic structure calculations is achieved using novel algorithms implemented for modern and massively parallel hardware. This review briefly summarizes the main capabilities and illustrates with recent applications the science cp2k has enabled in the field of atomistic simulation
The Dalton quantum chemistry program system

Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.Web of Science4328426
Machine learning methods in chemoinformatics

Machine learning algorithms are generally developed in computer science or adjacent disciplines and find their way into chemical modeling by a process of diffusion. Though particular machine learning methods are popular in chemoinformatics and quantitative structure-activity relationships (QSAR), many others exist in the technical literature. This discussion is methods-based and focused on some algorithms that chemoinformatics researchers frequently use. It makes no claim to be exhaustive. We concentrate on methods for supervised learning, predicting the unknown property values of a test set of instances, usually molecules, based on the known values for a training set. Particularly relevant approaches include Artificial Neural Networks, Random Forest, Support Vector Machine, k-Nearest Neighbors and naïve Bayes classifiers.Publisher PDFPeer reviewe
Electronic structure of conducting organic polymers: insights from time-dependent density functional theory

Cataloged from PDF version of article.Conducting organic polymers (COPs) became an active field of research after it was discovered how thin films rather than insoluble infusible powders can be produced. The combination of the properties of plastics with those of semiconductors opened the research field of organic electronics. COPs share many electronic properties with inorganic semiconductors, but there are also major differences, e. g., the nature of the charge carriers and the amount of the exciton binding energy. Theoretical analysis has been used to interpret experimental observations early on. The polaron model that was developed from one-electron theories is still the most widely used concept. In the 1990s, time-dependent density functional theory (TDDFT) became available for routine calculations. Using TDDFT, electronic states of long oligomers can be calculated. Now UV spectra of neutral and oxidized or reduced species can be compared with in situ UV spectra recorded during doping. Likewise states of cations can be used to model photoelectron spectra. Analysis of states has resolved several puzzles which cannot be understood with the polaron model, e. g., the origin of the dual absorption band of green polymers and the origin of a 'vestigial neutral band' upon doping of long oligomers. DFT calculations also established that defect localization is not crucial for spectral changes observed during doping and that there are no bound bipolarons in COPs. (C) 2014 John Wiley & Sons, Ltd
Exploiting the Potential Energy Landscape to Sample Free Energy

We review a number of recently developed strategies for enhanced sampling of complex systems based on knowledge of the potential energy landscape. We describe four approaches, replica exchange, Kirkwood sampling, superposition-enhanced nested sampling, and basin sampling, and show how each of them can exploit information for low-lying potential energy minima obtained using basin-hopping global optimization. Characterizing these minima is generally much faster than equilibrium thermodynamic sampling, because large steps in configuration space between local minima can be used without concern for maintaining detailed balance.The authors gratefully acknowledge financial support from the EPSRC and the ERC. S.M acknowledges
financial support from the Gates Cambridge Scholarship.This is the accepted manuscript. The final published version is available at http://onlinelibrary.wiley.com/doi/10.1002/wcms.1217/abstract
The uniform electron gas

The uniform electron gas or UEG (also known as jellium) is one of the most
fundamental models in condensed-matter physics and the cornerstone of the
most popular approximation—the local-density approximation—within density- functional
theory. In this article, we provide a detailed review on the energetics
of the UEG at high, intermediate, and low densities, and in one, two, and three
dimensions. We also report the best quantum Monte Carlo and symmetry-broken
Hartree-Fock calculations available in the literature for the UEG and
discuss the phase diagrams of jellium.P.F.L. thanks the
Australian Research Council for a Discovery Early Career Researcher Award (Grant No. DE130101441) and a
Discovery Project grant (DP140104071). P.M.W.G. thanks the Australian Research Council for funding
(Grants No. DP120104740 and DP140104071)
Challenges in Large Scale Quantum Mechanical Calculations

During the past decades, quantum mechanical methods have undergone an amazing
transition from pioneering investigations of experts into a wide range of
practical applications, made by a vast community of researchers. First
principles calculations of systems containing up to a few hundred atoms have
become a standard in many branches of science. The sizes of the systems which
can be simulated have increased even further during recent years, and
quantum-mechanical calculations of systems up to many thousands of atoms are
nowadays possible. This opens up new appealing possibilities, in particular for
interdisciplinary work, bridging together communities of different needs and
sensibilities. In this review we will present the current status of this topic,
and will also give an outlook on the vast multitude of applications, challenges
and opportunities stimulated by electronic structure calculations, making this
field an important working tool and bringing together researchers of many
different domains.Comment: accepted for publication by WIREs Computational Molecular Scienc
Challenges in large scale quantum mechanical calculations

During the past decades, quantum mechanical methods have undergone an amazing transition from pioneering investigations of experts into a wide range of practical applications, made by a vast community of researchers. First principles calculations of systems containing up to a few hundred atoms have become a standard in many branches of science. The sizes of the systems which can be simulated have increased even further during recent years, and quantum-mechanical calculations of systems up to many thousands of atoms are nowadays possible. This opens up new appealing possibilities, in particular for interdisciplinary work, bridging together communities of different needs and sensibilities. In this review we will present the current status of this topic, and will also give an outlook on the vast multitude of applications, challenges, and opportunities stimulated by electronic structure calculations, making this field an important working tool and bringing together researchers of many different domains.We would like to thank Modesto Orozco and Hansel Gómez for fruitful discussions and Fátima Lucas for providing various test systems and helping with some visualizations. This work was supported by the EXTMOS\ud
project, grant agreement number 646176, and the Energy oriented Centre of Excellence (EoCoE), grant agreement number 676629, funded both within the Horizon2020 framework of the European Union. This research\ud
used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Ofﬁce of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357.Peer ReviewedPostprint (author's final draft