Improvement of downlink LTE system performances using nonlinear equalization methods based on SVM and Wiener–Hammerstein

In this paper, we present versatile nonlinear equalizer based on support vector machine for a standard downlink LTE link. The nonlinear effects are introduced through a solid state power amplifier. The equalizer is compared with a linear RLS and nonlinear Wiener–Hammerstein (W–H) for 16QAM–MIMO–OFDM transmission, revealing improved performance at 1 Mb/s, by 3 and 2 dB in SNR, respectively, when targeting a EVM (dB) of ?60 dB. SVM equalization also outperforms the Wiener–Hammerstein by 1 dB in SNR.     

Throughput Behavior in Multihop Multiantenna Wireless Networks

Multiantenna or MIMO systems offer great potential for increasing the throughput of multihop wireless networks via spatial reuse and/or spatial multiplexing. This paper characterizes and analyzes the maximum achievable throughput in multihop, MIMO-equipped, wireless networks under three MIMO protocols, spatial reuse only (SRP), spatial multiplexing only (SMP), and spatial reuse and multiplexing (SRMP), each of which enhances the throughput, but via a different way of exploiting MIMO's capabilities. We show via extensive simulation that as the number of antennas increases, the maximum achievable throughput first rises and then flattens out asymptotically under SRP, while it increases "almost" linearly under SMP or SRMP. We also evaluate the effects of several network parameters on this achievable throughput, and show how throughput behaves under these effects.     

Formylation of O-Silylated Enolates by Vilsmeier's Reagent

Reaction of trimethylsilylenol ethers and Vilsmeier's reagent leads to the corresponding regiocontrolled β-dicarbonyl compounds with high to good yields.     

Coulomb charging effect of electrons in InAs/InAlAs quantum dots studied by capacitance techniques

Capacitance-voltage and deep level transient spectroscopy were used to study the capture characteristics of self-assembled InAs/InAlAs quantum dots grown on the InP substrate. It is found that the number of electrons captured by quantum dots can be controlled by varying the width of applied pulse voltage in the DLTS measurements. The Coulomb charging energy and the time of capture can be deduced from the filling time dependent deep level transient spectra.     

Energy analysis during acoustic bubble oscillations: Relationship between bubble energy and sonochemical parameters

In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by an ultrasonic wave has been theoretically studied for various conditions of acoustic amplitude, ultrasound frequency, static pressure and liquid temperature in order to explain the effects of these key parameters on both sonochemistry and sonoluminescence. The Keller–Miksis equation for the temporal variation of the bubble radius in compressible and viscous medium has been employed as a dynamics model. The numerical calculations showed that the rate of energy accumulation, dE/dt, increased linearly with increasing acoustic amplitude in the range of 1.5–3.0 atm and decreased sharply with increasing frequency in the range 200–1000 kHz. There exists an optimal static pressure at which the power w is highest. This optimum shifts toward a higher value as the acoustic amplitude increases. The energy of the bubble slightly increases with the increase in liquid temperature from 10 to 60 °C. The results of this study should be a helpful means to explain a variety of experimental observations conducted in the field of sonochemistry and sonoluminescence concerning the effects of operational parameters.     

Optimized link state routing for quality‐of‐service provisioning: implementation,measurement, and performance evaluation

This paper provides a measurement‐based performance evaluation of the Optimized Link State Routing (OLSR) protocol. Two versions of OLSR, OLSR‐ETX and OLSR‐ETT, are implemented and evaluated on a mesh network that we built from off‐the‐shelf commercial components and deployed within our department building. OLSR‐ETX uses the Expected Transmission Count (ETX) metric, whereas OLSR‐ETT uses the Expected Transmission Time (ETT) metric as a means of assessing link quality. The paper describes our implementation process of the ETT metric using the plug‐in feature of OLSRd, and our calculation method of link bandwidth using the packet‐pair technique. A series of measurements are conducted in our testbed to analyze and compare the performance of ETX and ETT metrics deemed useful for quality of service. Our measurements show that OLSR‐ETT outperforms OLSR‐ETX significantly in terms of packet loss, end‐to‐end delay, jitter, route changes, bandwidth, and overall stability, yielding much more robust, reliable, and efficient routing. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of ultrasound on adsorption-desorption of p-chlorophenol on granular activated carbon

The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-desorption on granular activated carbon. Adsorption equilibrium experiments and batch kinetics studies were carried out in the presence and the absence of ultrasound at 21 kHz. Results indicate that the adsorption of p-chlorophenol determined in the presence of ultrasound is lower than the adsorption observed in the absence of ultrasound. Desorption of p-chlorophenol from activated carbon with and without the application of ultrasound was studied. The desorption rates were favoured by increased ultrasound intensity. This rise is more noticeable as temperature increases. The addition of ethanol or NaOH to the system causes an enhancement of the amount of p-chlorophenol desorbed, especially in the presence of ultrasound. A synergetic enhancement of the desorption rate was observed when ultrasonic irradiation was coupled with ethanol chemical regeneration.     

A Cross-Layer Admission Control Framework for Wireless Ad-Hoc Networks using Multiple Antennas

Unlike single omnidirectional antennas, multiple antennas offer wireless ad-hoc networks potential increases in their achievable throughput and capacity. Due to recent advances in antenna technology, it is now affordable to build wireless devices with more than one antenna. As a result, multiple antennas are expected to be an essential part of next-generation wireless networks to support the rapidly emerging multimedia applications characterized by their high and diverse QoS needs. This paper develops an admission control framework that exploits the benefits of multiple antennas to better support applications with QoS requirements in wireless ad-hoc networks. The developed theory provides wireless ad-hoc networks with flow-level admission control capabilities while accounting for cross-layer effects between the PHY and the MAC layers. Based on the developed theory, we propose a mechanism that multiple antenna equipped nodes can use to control flows' admissibility into the network. Through simulation studies, we show that the proposed mechanism results in high flow acceptance rates and high network throughput utilization.     

Cross-Layer Optimized Conditions for QoS Support in Multi-Hop Wireless Networks with MIMO Links

Recent advances in antenna technology made it possible to build wireless devices with more than one antenna at affordable costs. Because multiple antennas offer wireless networks a potential capacity increase, they are expected to be a key part of next-generation wireless networks to support the rapidly emerging multimedia applications characterized by their high and diverse QoS requirements. This paper developed methods that exploit the benefits of multiple antennas to enable multi-hop wireless networks with flow-level QoS capabilities. The authors first propose a cross-layer table-driven statistical approach that allows each node to determine the amount of spatial reuse and/or multiplexing, offered by the multiple antennas that are available to it. The authors then use the developed statistical approach to derive sufficient conditions under which flow rates are guaranteed to be feasible. The derived conditions are multi-layer aware in the sense that they account for cross-layer effects between the PHY and the MAC layers to support QoS at higher layers. The authors evaluate and compare the derived sufficient conditions via extensive simulations. The authors show that the conditions result in high flow acceptance rates when used in multi-hop wireless networking problems such as QoS routing and multicommodity flow problems. The authors also demonstrate the importance and the effect of considering cross-layer couplings into the development of flow acceptance methods.