A Survey of Various Schedulers Used for Fair Bandwidth Allocation in WiMAX: IEEE 802.16

ABSTRACT

Wireless Interoperability for Multiple Access (WiMAX) is one of the emerging fields of high-speed wireless communication that has enormous capabilities due to its range and the connection speed. Like wireless local area networks (LANs), WiMAX networks implement multiple quality of service (QoS) frameworks at the Media Access Control (MAC) level for assured data, voice, and video services. The question of ensuring QoS is basically how to distribute available resources to users in order to satisfy QoS parameters such as latency, jitter and throughput requirements. IEEE 802.16 standard does not have any particular guidelines on scheduling of incoming and outgoing data. This has caught the attention of researchers working on WiMAX. This article discusses the various issues in WiMAX along with a classification of various scheduling approaches based upon the type of scheduler for the sake of better understanding the scheduling problem and analyzing various available theories.     

A systematic investigation of the integrated effects of gate underlapping,dual work functionality and hetero gate dielectric for improved performance of CP TFETs

This paper presents a comparative analysis of the combined effects of gate underlapping and dual work functionality with hetero gate dielectric engineering for a charge plasma tunnel field-effect transistor (CP TFET). Ultrathin nanoscale devices, despite their size and cost advantage, present serious issues, including doping control, random dopant fluctuation and fabrication complexity. Given these concerns, the concept of charge plasma is introduced to avoid the need for conventional doping for the formation of the source and drain regions, which makes the device resistive to process variation. Conduction for negative gate bias (ambipolarity), excess Miller capacitance (gate-to-drain capacitance) and poor RF performance in TFETs are addressed by the use of gate underlapping from the drain side. In addition, enhanced ON-state current is obtained by work function shifting (dual work functionality). This shift in work function can be accomplished by nitrogen doping of the gate electrode for experimental levels [1]. The combined effects of the underlap and dual work function are seen in the device having a single gate dielectric. However, the ON-state current remains lower in the case of \(\mathrm{SiO}_{2}\) as the gate dielectric. Therefore, a hetero gate dielectric \(\mathrm{SiO}_{2}\) on the drain side and \(\mathrm{HfO}_{2}\) on the source side are considered in order to improve the RF parameters and enhance the ON-current concept, respectively. Finally, the combined effects of gate underlap with work function shift and hetero dielectric are analyzed in CP TFETs. The results show that proper underlap length and gate work function provide a significant improvement in device performance. Therefore, optimization of the underlap length and work function is performed to determine the specific work function that provides overall enhancement of DC and analog/RF performance of the device. In addition, optimization of the dual work function gate length is demonstrated.     

Thermal and rheological behavior of acrylonitrile–carboxylic acid copolymers and their metal salt complexes

The influence of acrylic, methacrylic, and itaconic acid comonomers in the nitrile oligomerization of acrylonitrile copolymers has been studied by DSC and DSC‐FTIR in air and nitrogen atmospheres. Addition of metal salts in poly(acrylonitrile–acrylic acid) copolymer, PA on thermal and rheological behavior has also been reported. Incorporation of CuSO₄, FeSO₄, ZnSO₄, and Al₂ (SO₄)₃ (1 to 5 wt %) salt in the polymer solution affects its solubility in DMF. The complexes of PA with zinc sulphate, took a longer time to dissolve in DMF, whereas the complexes with Fe(SO₄) and Al₂(SO₄)₃ are almost insoluble in DMF, perhaps due to intermolecular crosslinking. Addition of these metal salts to the PA solution also affects its Brookfield viscosity. The viscosity of 10 wt % polymer solution increases from 400 centipoise (Cps) to 1090 Cps for complex with 5% FeSO₄ (on the weight of dope solids) and 690 Cps for Al₂ (SO₄)₃ and 906 cps for ZnSO₄ complex. However, for CuSO₄ salt complex this value is 770 Cps. FTIR spectra shows the participation of COOH and CN group in the complex formation, which is responsible for enhanced Brookfield viscosity. Thermal behavior of the polymer–metal salt complex showed that these salts also affect the exothermic reaction. The initiation of cyclization reaction takes place at a lower temperature compared to neat acrylonitrile–acrylic acid copolymer. However, the heat liberated per unit time in N₂ atmosphere in case of neat polymer is 6.3 Jg⁻¹ min⁻¹, which reduces to 5.5 Jg⁻¹ min⁻¹ in the case of the PA/Al complex, confirming the role of Al₂ (SO₄)₃ in retarding the rate of cyclization reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 567–582, 1999     

Vinyl monomers-induced synthesis of polyvinyl alcohol-stabilized selenium nanoparticles

A simple wet chemical method has been developed to synthesize selenium nanoparticles (size 100-200 nm), by reaction of sodium selenosulphate precursor with different vinyl monomers, such as acrylamide, N,N′-dimethylene bis acrylamide, methyl methacrylate, sodium acrylate, etc., in aqueous medium, under ambient conditions. Polyvinyl alcohol has been used to stabilize the selenium nanoparticles. Average size of the synthesized selenium nanoparticles can be controlled by adjusting concentration of both the precursors and the stabilizer. Rate of the reaction as well as size of the resultant selenium nanoparticles have been correlated with the functional groups of the different monomers. UV-vis optical absorption spectroscopy, X-ray diffraction, energy dispersive X-rays, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy techniques have been employed to characterize the synthesized selenium nanoparticles. Gas chromatographic analysis of the reaction mixture established the non-catalytic role of the vinyl monomers, which were found to be consumed during the course of the reaction.     

Studies on the composition,quality and processing of triticale Part 3. Rheological and baking properties

Studies on rheological and baking properties of 14 promising strains of triticale and two check wheat varieties from India are reported. The farinograms obtained from triticale flours, in general, revealed poor dough development time and lower stability than those from wheat flours. The mean water absorption capacity of triticale flours was 54.3 percent compared to 64.4 percent of wheat flour. The triticale flour produced poor loaf volumes with mean value of 399 cm³ compared to 475 cm³ of wheat flour. Cookie baking tests showed that triticale flours were eminently suited for this purpose because of their soft flour and weaker gluten. Triticale whole meal required much less water for preparation of dough for chapatis and produced red coloured chapatis which tended to stale faster.     

Synthesis of diethyl carbonate from dimethyl carbonate and ethanol using KF/Al2O3 as an efficient solid base catalyst

Diethyl carbonate, an efficient oxygen-containing fuel additive was synthesized from dimethyl carbonate and ethanol using KF/Al₂O₃. The catalysts prepared with different KF loading were characterized using X-ray diffraction, BET surface area and basicity measurement analyses. The effects of different reaction parameters such as temperature, reactant ratio and amount of catalyst were optimized. Among the different alkali halides, 20 wt.% KF supported on alumina exhibited 61.6% diethyl carbonate selectivity with 96% dimethyl carbonate conversion under optimum reaction conditions. The plausible reaction mechanism is proposed based on the results obtained. The possibility of recycling the catalyst was ensured without appreciable loss in activity for four cycles.     

Preparation and characterization of bio-functionalized iron oxide nanoparticles for biomedical application

Amine modified iron oxide (Fe₃O₄) nanoparticles were synthesized by thermal decomposition method and were further used to bio-functionalize by grafting of N-hydroxysuccinimide (NHS) ester of folate and ethylenediaminetetraacetate (EDTA). Fe₃O₄ nanoparticles of ~ 22 nm were confirmed from X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. FT-IR studies indicated two bands at 1515 cm^− 1and 1646 cm^− 1, which can be attributed to carboxylic group and the amide linkage respectively, revealing the conjugation of folate with Fe₃O₄. The conjugation of the chelating agent showed strong C=O stretch and Fe-O vibrations at 1647 and 588 cm^− 1 respectively. The value of saturation magnetization for Fe₃O₄ nanoparticles was found to be 88 emu/g, which further reduced to 18 and 32% upon functionalization with EDTA and NHS ester folate, respectively. These amine modified Fe₃O₄ nanoparticles can also be functionalized with other bifunctional chelators, such as amino acids based diethylene triamine pentaacetic acid (DTPA), and thus find potential applications in radio-labeling, biosensors and cancer detection, etc.     

Automatic parameterization of rational curves and surfaces III: Algebraic plane curves

We present algorithms to compute the genus and rational parametric equations, for implicitly defined irreducible plane algebraic curves of arbitrary degree. Rational parameterizations exist for all irreducible algebraic curves of genus 0. The genus is computed by a complete analysis of the singularities of plane algebraic curves, using affine quadratic transformations. The rational parameterization techniques, essentially, reduce to solving symbolically systems of homogeneous linear equations and the computation of polynomial resultants.