3,963 research outputs found
Development of a dc-ac power conditioner for wind generator by using neural network
This project present of development single phase DC-AC converter for wind
generator application. The mathematical model of the wind generator and Artificial
Neural Network control for DC-AC converter is derived. The controller is designed to
stabilize the output voltage of DC-AC converter. To verify the effectiveness of the
proposal controller, both simulation and experimental are developed. The simulation and
experimental result show that the amplitude of output voltage of the DC-AC converter
can be controlled
Full duplex 60 GHz millimeter wave transmission over multi-mode fiber
Copyright @ 2010 IEEENew wireless subscribers are signing up at an increasing demand of more capacity for ultra-high data rate transfers at speeds more than 1 Gbps, while the radio spectrum is limited. Millimeter wave communication system offers a unique way to resolve these problems. In this paper, the performance of a full duplex transportation system is reported for 1.5 Km of multi-mode fiber length for a sample 10 Gbit/s pseudo random sequence data, with quadrature amplitude modulation mapping and orthogonal frequency division multiplexing modulation with 60 GHz RF and coherent 1550 nm optical carrier. The analysis and simulation results show that the system's quality of service depends on nonlinearity of electro optical modulator, dispersion and signal attenuation impairment of the multi-mode fiber cable
Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications
Orbital angular momentum (OAM) has aroused a widespread interest in many
fields, especially in telecommunications due to its potential for unleashing
new capacity in the severely congested spectrum of commercial communication
systems. Beams carrying OAM have a helical phase front and a field strength
with a singularity along the axial center, which can be used for information
transmission, imaging and particle manipulation. The number of orthogonal OAM
modes in a single beam is theoretically infinite and each mode is an element of
a complete orthogonal basis that can be employed for multiplexing different
signals, thus greatly improving the spectrum efficiency. In this paper, we
comprehensively summarize and compare the methods for generation and detection
of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications
and technical challenges of OAM in communications, including free-space optical
communications, optical fiber communications, radio communications and acoustic
communications. To complete our survey, we also discuss the state of art of
particle manipulation and target imaging with OAM beams
Energy-efficiency improvements for optical access
This article discusses novel approaches to improve energy efficiency of different optical access technologies, including time division multiplexing passive optical network (TDM-PON), time and wavelength division multiplexing PON (TWDM-PON), point-to-point (PTP) access network, wavelength division multiplexing PON (WDM-PON), and orthogonal frequency division multiple access PON (OFDMA-PON). These approaches include cyclic sleep mode, energy-efficient bit interleaving protocol, power reduction at component level, or frequency band selection. Depending on the target optical access technology, one or a combination of different approaches can be applied
MAC Protocol Design for the Support of DBA in OFDMA-PON Networks
Wansu Lim, Ali Gliwan, Pandelis Kourtessis, Konstantinos Kanonakis, Ioannis Tomkos, John Senior, 'MAC Protocol Design for the Support of DBA in OFDMA-PON Networks', Paper presented at the Future Network and Mobile Summit, 15-17 June 2011, Warsaw, Poland.Original MAC frame formats have been developed to provide recommendations for new protocol designs in OFDMA-PONs. The portrayed scalability of the Dynamic Subcarrier Allocation (DScA) protocol is complemented by the granularity of hybrid OFDMA/TDMA topologies. Modelling of the DScA performance in OPNET has recorded the maximum 312.5 Mbits/s transmission rate capacity per ONU achieved at less than 2 ms packet delay and more than 95% network throughput depending on ONU offered load.Peer reviewe
Orthogonal frequency-division multiplexing in wireless communication systems with multimode fiber feeds
The feasibility of using multimode fiber as an inexpensive
cell feed in broad-band indoor picocellular systems is investigated in this paper. The performance of coded orthogonal frequency-division multiplexing (OFDM) for a variety of multimode fiber profiles, including stepped index and -profile graded index fibers, is assessed. In addition to its ability to perform well in a frequency-
selective multipath environment, OFDM is shown to offer
good protection against the frequency selectivity of a dispersive multimode fiber. Data rates in excess of 100 Mb/s (without equalization) over a multimode fiber channel are possible, whereas they may be limited to some 20–30 Mb/s using conventional ASK modulation
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