In recent years, the increasing traffic demand in radio access networks (RAN) has led to considerable growth of the number of base stations (BS), posing a serious scalability issue with respect to the energy consumption of BSs. Optical-access-enabled Cloud RAN (CRAN) has been recently proposed as a next-generation access network, where the digital unit (DU) of a conventional cell site is separated from the radio unit (RU), by an optical access network (fronthaul), and moved to the “cloud” (DU pool) for centralized signal processing and management. Time-Wavelength Division Multiplexing (TWDM) Passive Optical Network (PON) is a promising fronthaul solution due to its low energy consumption and high capacity. In this study, we propose the concept of Virtual Base Station (VBS), which is dynamically formed for each cell by assigning virtualized network resources, including i) a virtualized PON link connecting the DU and RU and ii) virtualized functional entities performing baseband processing in DU pool. We propose a novel energy-saving scheme exploiting VBS formation for CRAN and compare its performance with the optimal results of an Integer Linear Program for VBS formation optimization problem. Numerical evaluation shows that CRAN with VBS formation achieves significant energy savings compared to traditional RAN and CRAN without VBS formation.

The time-periodic property of the LCD VCOM noise is utilized to reduce the effect of the VCOM noise on the mutual-capacitance measuring touch sensor placed on a LCD panel. The amplitude of the touch sensor driving signal (VSTM) can be reduced reliably down to 0.4 V with the reporting rate of 189 Hz, by using the following two methods. (1) The frequency of VSTM is set to (n+0.5)·fN, by synchronizing VSTM to a LCD gate driver signal with a referenceless CDR. fN is the inverse of the LCD VCOM noise period (TN) and n is a positive integer. (2) The reset period of the RX integrator is set to 2·TN.

Time- and wavelength-division multiplexed passive optical network allows wavelength sharing by optical network units (ONUs) in a time-division multiplexing fashion. When ONUs are lightly loaded, they can share fewer wavelengths to reduce energy consumption. In such a dynamic system, the configuration of wavelength sharing should adapt to the traffic changes for energy saving and load balancing (which affects the quality of service). However, going from one configuration to another is nontrivial, as it usually involves wavelength reassignment and potential service disruptions. The optimization and algorithm design have to account for such reconfiguration (along with other aspects). In this study, we have developed optimization models and online algorithms that incorporate the reconfiguration dimension. Various underlying tradeoffs (e.g., energy saving versus reconfiguration and load balancing versus reconfiguration) are investigated for both static planning and dynamic operations.

In this paper, a sensorless control of an interior permanent magnet synchronous motors (IPMSMs) is proposed using an Extended Kalman Filter (EKF) based on the extended rotor flux concept. Also, simple parameter estimation method is proposed to improve the performance of sensorless drive method. The IPMSM sensorless drive system has nonlinearity charac-teristics and parameters variation. To overcome two main drawbacks, the estimation of Extended rotor flux using the EKF is suitable for high performance because of its ability to perform state estimation for nonlinear systems that involve random noise environment. The simple parameter estimation method is also adopted to reduce deterioration of estimation of variables. The experimental results illustrate the validity of the analytical approach and the efficiency of the proposed method.

In this paper, the improved stator flux estimator has been proposed to ensure A Programmable Low Pass Filter (PLPF) to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency, with the magnitude and phase compensator determined on the assumption of the estimated synchronous speed being coincident with the actual one. However, if the synchronous speed is not exactly estimated, the magnitude and phase compensation will not be appropriate. Therefore, this paper has analyzed the relation between the synchronous speed error and the phase lag error of the stator flux. Based on this analysis, the synchronous speed error compensation scheme is proposed. In addition, this paper proposes the flux error compensation scheme because there still remain errors in spite of the speed error compensation. The validity of the proposed estimator has been proven using the simulation results.

This paper proposes a hybrid passive optical network (PON) system based on a dense wavelength division multiplexing-PON (DWDM-PON) and reach extender (RE) for increasing the optical link budget and link capacity in an existing gigabit PON (GPON) system. A DWDM-PON is applied to the feeder fiber and is interfaced with the RE. The RE provides a wavelength conversion between the DWDM-PON and GPON through frame regeneration, and controls upstream burst signals. The hybrid PON system enables a legacy GPON system to operate over a minimum 40 km distance with a 128-way split per WDM wavelength.

We have successfully transmitted 40 channels/spl times/40 Gb/s NRZ signals using KT (Korea Telecom)'s field installed 511 km of standard single mode fiber. In the field trial, we adopted conventional optical amplifiers to provide cost-effective capacity upgradeability from already installed 10 Gb/s based WDM transmission equipment. After transmission of 511 km, the measured Q-values range from 13.3 to 15.4 dB without forward error correction (FEC) operation. The Q-value fluctuation in the worst performance channel was found to be 0.08 dB.

There are many trials to provide an optimal route for minimum energy consumption in a wireless sensor network. Currently, however, the mechanisms to find minimum energy property graph (MEPG) do not properly take into account the efficiency in time and storage, the optimality in results, and the feasibility in real systems. In this paper, we propose an efficient and first optimal algorithm to find the MEPG, in which all minimum energy paths are included, not only significantly reducing its total number of edges, but also obtaining an optimal result in O(VlogV+E). We also develop power aware data-centric routing protocol characterized by minimum energy consumption and longer lifetime.

The purpose of this study was to investigate the effects of international virtual learning classes. For the purpose, the class implemented using multipoint communication system which was constructed high quality video transfer systems on a cross-border infrastructure (gigabit bandwidth) between Japan to South Korea. In order to reveal the effects of the class, a questionnaire was composed of five categories; consciousness to foreign countries, nationality, acquisition of view point, motivation, recognition to the partner country. The results of 2 /spl times/ 2 mixed two-way ANOVA showed differences of characteristics of two countries and changes of student's attitude. The results revealed that an international virtual learning class has a possibility to develop and enhance student's awareness of humanity and the world. Future implementation will depend on growth and sustenance of the international relationship for a prolonged period.

A read-channel chip set for rewritable 3.5 in 230 Mbytes magneto-optical disk drives (MOD) is presented. The front-end chip includes an automatic gain control (AGC) circuit, a programmable six-pole two-zero equiripple filter/equalizer, a DC restore circuit, and pulse detectors. The back-end contains a frequency synthesizer phase-locked loop (PLL) and a data separator PLL with 3:1 operating range to support a constant density recording with 8-24 Mb/s data rate (or code rate of 16 to 48 Mb/s) in (2, 7) run-length limited (RLL) encoding format. The architecture of the chip provides high degree of programmability through a serial microprocessor interface, fast switching (<1 /spl mu/s) between sector mark and data detector modes, and four levels of power management in a 1.5 /spl mu/m 4 GHz BiCMOS process. With a nominal power supply of 5 V, the chip set dissipates 600 mW during normal operation and 1 mW during sleep mode.

The incomplete Choleski conjugate gradient (ICCG) method and a macromodeling technique employing asymptotic waveform evaluation (AWE) have been applied to the simulation of integrated circuits in the presence of parasitic electrical and thermal substrate coupling interactions. Simulation of electrical substrate coupling effects has been found to be accurate and fast as compared to MEDICI, a device simulation program. Simulation results are also in good agreement with reported measurements on a test chip fabricated in a 2/spl mu/m BiCMOS n-well process. DC/steady-state and transient simulations of thermal substrate interactions using similar techniques on several benchmark circuits show orders of magnitude reduction in cpu time compared to traditional simulation techniques.