Novel Digital Radio over Fiber (DRoF) System with Data Compression for Neutral-Host Fronthaul Applications

© 2013 IEEE. Digital radio-over-fibre transmission has been studied extensively as a way of providing seamless last-mile wireless connectivity by carrying digitised radio frequency (RF) services over broadband optical infrastructures. With the growing demand on wireless capacity and the number of wireless services, a key challenge is the enormous scale of the digital data generated after the digitisation process. In turn, this leads to optical links needing to have very large capacity and hence, high capital expenditure (CAPEX). In this paper, we firstly present and then experimentally demonstrate a multiservice DRoF system for a neutral-host fronthaul link where both forward and reverse links use data compression, multiband multiplexing and synchronisation algorithms. The effect of a novel digital automatic gain control (DAGC) is comprehensively analysed to show an improved RF dynamic range alongside bit rate reduction. In this case, the system allows all cellular services from the three Chinese mobile network operators (MNOs) to be converged onto a single fiber infrastructure. We successfully demonstrate 14 wireless channels over a 10Gbps 20km optical link for indoor and outdoor wireless coverage, showing a minimum error value magnitude (EVM) of 60dB RF dynamic range. It is believed that the technology provides an ideal solution for last-mile wireless coverage in 5G and beyond

Fast-Settling Two-Stage Automatic Gain Control for Multi-Service Fibre-Wireless Fronthaul Systems

© 2013 IEEE. With the development of fast digitiser and digital signal processing techniques, wide-band digital radio-over-fiber (DRoF) based wireless fronthaul systems have been extensively studied as a way of offering multi-service wireless coverage. With data compression, the high digital data rate caused by digitisation can be reduced so as to minimise the infrastructure cost for last-mile cellular coverage. However, data compression always comes with the cost of a lower input power dynamic range. To overcome the issue, this paper proposes a novel fast-settling two-stage automatic gain control (FSS-AGC) algorithm, in which gain adjustment is carried out by a multi-threshold decision mechanism with a fast-settling time (within 2 μs), high stability and great accuracy. By introducing a novel gain control mechanism which simultaneously adjusts the gain in the digital and RF domains, the loss of dynamic range after compression is compensated. This algorithm is applied and demonstrated in a DRoF based digital distributed antenna system (DDAS) which supports all current cellular services from 3 Chinese mobile network operators (MNOs). The demonstration shows over 73dB dynamic range, with 40dB improvement compared with conventional links. Its promising properties and excellent performance enable its potential application in next-generation converged networks for Internet of things (IoT) and 5G services.National Natural Science Foundation of China under Grant 61371006, the Equipment Advance Research Project, the Defense Industrial Technology Development Program, the Chinese Government Fund, the International Cooperative Project of Smart In-building Wireless System using Flexible Digital Transmission Technology (SWIFT

Testing supersymmetry at the LHC through gluon-fusion production of a slepton pair

Renormalizable quartic couplings among new particles are typical of supersymmetric models. Their detection could provide a test for supersymmetry, discriminating it from other extensions of the Standard Model. Quartic couplings among squarks and sleptons, together with the SU(3) gauge couplings for squarks, allow a new realization of the gluon-fusion mechanism for pair-production of sleptons at the one-loop level. The corresponding production cross section, however, is at most of ${\cal O}(1)$fb for slepton and squark masses of ${\cal O}(100)$GeV. We then extend our investigation to the gluon-fusion production of sleptons through the exchange of Higgs bosons. The cross section is even smaller, of ${\cal O}(0.1)$fb, if the exchanged Higgs boson is considerably below the slepton-pair threshold, but it is enhanced when it is resonant. It can reach ${\cal O}(10)$fb for the production of sleptons of same-chirality, exceeding these values for $\widetilde{\tau}$'s of opposite-chirality, even when chirality-mixing terms in the squark sector are vanishing. The cross section can be further enhanced if these mixing terms are nonnegligible, providing a potentially interesting probe of the Higgs sector, in particular of parameters such as $A$, $\mu$, and $\tan\beta$.Comment: 28 pages, 11 figure

AGI and the Knight-Darwin Law: why idealized AGI reproduction requires collaboration

Can an AGI create a more intelligent AGI? Under idealized assumptions, for a certain theoretical type of intelligence, our answer is: “Not without outside help”. This is a paper on the mathematical structure of AGI populations when parent AGIs create child AGIs. We argue that such populations satisfy a certain biological law. Motivated by observations of sexual reproduction in seemingly-asexual species, the Knight-Darwin Law states that it is impossible for one organism to asexually produce another, which asexually produces another, and so on forever: that any sequence of organisms (each one a child of the previous) must contain occasional multi-parent organisms, or must terminate. By proving that a certain measure (arguably an intelligence measure) decreases when an idealized parent AGI single-handedly creates a child AGI, we argue that a similar Law holds for AGIs

Effects of Environmental Agents on the Attainment of Puberty: Considerations When Assessing Exposure to Environmental Chemicals in the National Children’s Study

The apparent decline in the age at puberty in the United States raises a general level of concern because of the potential clinical and social consequences of such an event. Nutritional status, genetic predisposition (race/ethnicity), and environmental chemicals are associated with altered age at puberty. The Exposure to Chemical Agents Working Group of the National Children’s Study (NCS) presents an approach to assess exposure for chemicals that may affect the age of maturity in children. The process involves conducting the assessment by life stages (i.e., in utero, postnatal, peripubertal), adopting a general categorization of the environmental chemicals by biologic persistence, and collecting and storing biologic specimens that are most likely to yield meaningful information. The analysis of environmental samples and use of questionnaire data are essential in the assessment of chemicals that cannot be measured in biologic specimens, and they can assist in the evaluation of exposure to nonpersistent chemicals. Food and dietary data may be used to determine the extent to which nutrients and chemicals from this pathway contribute to the variance in the timing of puberty. Additional research is necessary in several of these areas and is ongoing. The NCS is uniquely poised to evaluate the effects of environmental chemicals on the age at puberty, and the above approach will allow the NCS to accomplish this task

Dipolar collisions of polar molecules in the quantum regime

Ultracold polar molecules offer the possibility of exploring quantum gases with interparticle interactions that are strong, long-range, and spatially anisotropic. This is in stark contrast to the dilute gases of ultracold atoms, which have isotropic and extremely short-range, or "contact", interactions. The large electric dipole moment of polar molecules can be tuned with an external electric field; this provides unique opportunities such as control of ultracold chemical reactions, quantum information processing, and the realization of novel quantum many-body systems. In spite of intense experimental efforts aimed at observing the influence of dipoles on ultracold molecules, only recently have sufficiently high densities been achieved. Here, we report the observation of dipolar collisions in an ultracold molecular gas prepared close to quantum degeneracy. For modest values of an applied electric field, we observe a dramatic increase in the loss rate of fermionic KRb molecules due to ultrcold chemical reactions. We find that the loss rate has a steep power-law dependence on the induced electric dipole moment, and we show that this dependence can be understood with a relatively simple model based on quantum threshold laws for scattering of fermionic polar molecules. We directly observe the spatial anisotropy of the dipolar interaction as manifested in measurements of the thermodynamics of the dipolar gas. These results demonstrate how the long-range dipolar interaction can be used for electric-field control of chemical reaction rates in an ultracold polar molecule gas. The large loss rates in an applied electric field suggest that creating a long-lived ensemble of ultracold polar molecules may require confinement in a two-dimensional trap geometry to suppress the influence of the attractive dipolar interactions

Semi-Interpenetrating Polymer Networks for Enhanced Supercapacitor Electrodes

Conducting polymers show great promise as supercapacitor materials due to their high theoretical specific capacitance, low cost, toughness, and flexibility. Poor ion mobility, however, can render active material more than a few tens of nanometers from the surface inaccessible for charge storage, limiting performance. Here, we use semi-interpenetrating networks (sIPNs) of a pseudocapacitive polymer in an ionically conductive polymer matrix to decrease ion diffusion length scales and make virtually all of the active material accessible for charge storage. Our freestanding poly(3,4-ethylenedioxythiophene)/poly(ethylene oxide) (PEDOT/PEO) sIPN films yield simultaneous improvements in three crucial elements of supercapacitor performance: specific capacitance (182 F/g, a 70% increase over that of neat PEDOT), cycling stability (97.5% capacitance retention after 3000 cycles), and flexibility (the electrodes bend to a <200 μm radius of curvature without breaking). Our simple and controllable sIPN fabrication process presents a framework to develop a range of polymer-based interpenetrated materials for high-performance energy storage technologies.This work was funded by the European Research Council (ERC) grant to S.K.S., EMATTER (# 280078). K.D.F. acknowledges support from the Winston Churchill Foundation of the United States. T.W. thanks the China Scholarship Council (CSC) for funding and the Engineering and Physical Sciences Research Council of the U.K. (EPSRC) Centre for Doctoral Training in Sensor Technologies and Applications (Grant Number: EP/L015889/1) for support

Inkjet printing infiltration of Ni-Gd:CeO2 anodes for low temperature solid oxide fuel cells.

ABSTRACT: The effect of inkjet printing infiltration of Gd0.1Ce0.9O2-x in NiO-Gd0.1Ce0.9O2-x anodes on the performance of symmetrical and button cells was investigated. The anodes were fabricated by inkjet printing of suspension and sol inks. Symmetrical cells were produced from composite suspension inks on Gd0.1Ce0.9O2-x electrolyte. As-prepared scaffolds were infiltrated with Gd0.1Ce0.9O2 ink. Increasing the number of infiltration steps led to formation of "nano-decoration" on pre-sintered anodes. High resolution SEM analysis was employed for micro-structural characterization revealing formation of fine anode sub-structure with nanoparticle size varying in the range of 50-200 nm. EIS tests were conducted on symmetrical cells in 4% hydrogen/argon gas flow. The measurements showed substantial reduction of the activation polarization as a function of the number of infiltrations. The effect was assigned to the extension of the triple phase boundary. The i-V testing of a reference (NiO-8 mol% Y2O3 stabilized ZrO2/NiO-Gd0.1Ce0.9O2-x /Gd0.1Ce0.9O2-x /Gd0.1Ce0.9O2-x -La0.6Sr0.4Co0.2Fe0.8O3-δ ) cell and an identical cell with infiltrated anode revealed ~2.5 times improvement in the maximum output power at 600 °C which corresponded with the reduction of the polarization resistance of the symmetrical cells at the same temperature (2.8 times). This study demonstrated the potential of inkjet printing technology as an infiltration tool for cost effective commercial SOFC processing

Analysis of factors influencing the modelling of occupant window opening behaviour in an office building in Beijing, China.

This paper introduces a longitudinal study monitoring occupants’ window opening behaviour in a mixed-mode office building in Beijing, China, when natural ventilation is specifically used for controlling the building’s indoor thermal environment. Based on the field measured data, the influence of factors, including outdoor air temperature, outdoor PM2.5, indoor air temperature, time of day, occupancy and previous window state, on the observed state of windows is analysed. All of them are influential on occupants’ window opening behaviour in the case study building, and so they can be used to model occupants’ window opening behaviour in buildings in China to achieve a better consideration of occupant behaviour in dynamic building performance simulation

Controlling the quantum stereodynamics of ultracold bimolecular reactions

Chemical reaction rates often depend strongly on stereodynamics, namely the orientation and movement of molecules in three-dimensional space. An ultracold molecular gas, with a temperature below 1 uK, provides a highly unusual regime for chemistry, where polar molecules can easily be oriented using an external electric field and where, moreover, the motion of two colliding molecules is strictly quantized. Recently, atom-exchange reactions were observed in a trapped ultracold gas of KRb molecules. In an external electric field, these exothermic and barrierless bimolecular reactions, KRb+KRb -> K2+Rb2, occur at a rate that rises steeply with increasing dipole moment. Here we show that the quantum stereodynamics of the ultracold collisions can be exploited to suppress the bimolecular chemical reaction rate by nearly two orders of magnitude. We use an optical lattice trap to confine the fermionic polar molecules in a quasi-two-dimensional, pancake-like geometry, with the dipoles oriented along the tight confinement direction. With the combination of sufficiently tight confinement and Fermi statistics of the molecules, two polar molecules can approach each other only in a "side-by-side" collision, where the chemical reaction rate is suppressed by the repulsive dipole-dipole interaction. We show that the suppression of the bimolecular reaction rate requires quantum-state control of both the internal and external degrees of freedom of the molecules. The suppression of chemical reactions for polar molecules in a quasi-two-dimensional trap opens the way for investigation of a dipolar molecular quantum gas. Because of the strong, long-range character of the dipole-dipole interactions, such a gas brings fundamentally new abilities to quantum-gas-based studies of strongly correlated many-body physics, where quantum phase transitions and new states of matter can emerge.Comment: 19 pages, 4 figure