Yo Han Ko

2-D DoA Estimation with Cell Searching for a Mobile Relay Station with Uniform Circular Array

In this letter, a 2-D Direction-of-Arrival (DoA) estimation scheme with cell searching is proposed for a mobile relay station (MRS) with uniform circular array (UCA) at a handover region. The proposed scheme of cell searching and DoA estimation for the MRS with UCA is robust even when there exist symbol timing offsets (STOs). Compared with the previous scheme, the proposed scheme can reduce computational complexity and processing time for cell searching and DoA estimation. Simulation results are included to verify the performance of the proposed scheme under a mobile WiMAX environment.

Joint Methods of Cell Searching and DoA Estimation for a Mobile Relay Station with Multiple Antennas

In this paper, a mobile relay station (MRS) for vehicles with beamforming antennas is considered to increase the reliability of transmission link, especially for the MRS at cell boundary. Joint methods for cell searching and DoA estimation are proposed to form a beam in the direction of target BS while nulling interferences from adjacent BSs, especially for IP- based cellular systems employing break-before-make handover or make-before-break handover. The proposed cell searching and DoA estimation methods are evaluated by computer simulation under the environment of IEEE 802.16e (WiBro).

A polar coordinate-oriented method of identifying rotor flux and speed of induction motors without rotational transducers

In this paper, we propose a novel method of identifying rotor flux and speed of induction motors. Our identification algorithm does not involve any pure integration operations, which have been a main source of performance deterioration in most of prior works. This is made possible by formulating the identification problem in the polar coordinate frame. It does not contain any parameters which need to be retuned according to H/W configurations or operation conditions. Moreover, the rotor speed does not have to vary slowly for the convergence of the estimation error. Some experimental results as well as a rigorous convergence analysis are presented to demonstrate the practical use and generality of our identification method. For our experimental work, we have built a prototype drive system, in which all identification and control algorithms are implemented digitally on a DSP.<<ETX>>

DoA estimation with cell searching for mobile relay stations with uniform circular array

In this paper, a Direction-of-Arrival (DoA) estimation scheme with cell searching is proposed for a mobile relay station (MRS) with uniform circular array (UCA) at handover region. The proposed scheme of cell searching and DoA estimation for the MRS with UCA is robust even when there exist symbol timing offsets (STOs). Compared with the previous scheme, the proposed scheme can reduce computational complexity and processing time for cell searching and DoA estimation. Simulation results are included to verify the performance of the proposed scheme under Mobile WiMAX environment.

A Synchronous Digital Duplexing Technique for Wireless Transmission in Indoor Environments

In this paper, we propose a new digital duplexing scheme, called synchronous digital duplexing (SDD), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously in wireless communication. In order to transmit uplink and downlink signals simultaneously, the proposed SDD obtains mutual information among subscriber stations (SSs) with a mutual ranging symbol. This information is used for selection of transmission time, decision on cyclic suffix (CS) insertion, determination of CS length, and re-establishment of FFT starting point. It is shown that in terms of efficiency and flexibility the proposed SDD is better equipped as a duplexing scheme for indoor wireless environments than conventional time division duplexing (TDD) and frequency division duplexing (FDD).

Generalized techniques of reducing torque ripples in BDCM drives

In this paper, a new technique of reducing torque ripples in inverter fed brushless DC motor drives is presented. The developed technique allows the reduction of as many torque ripple components as switching angles per half cycle of the inverter. The switching angles are determined by solving the nonlinear equations of the problem using numerical techniques. Software programs are developed to analyze the technique and the simulated torque waveforms are compared. The developed technique is also implemented to provide experimental torque waveforms. It is demonstrated that the developed technique can reduce the torque ripples and improve the performance of the system.<<ETX>>

A closed-form DoA estimation method with cell searching for an MRS with array antenna

In this paper, closed-form DoA estimation methods with cell searching are proposed for a mobile relay station with array antennas such as ULA and UCA. The proposed methods can reduce the complexity to estimate DoA and search cell ID of each BS. The performances and computational complexities of the proposed methods are evaluated by computer simulation.

Cell searching and DoA estimation methods for OFDM-based mobile relay stations with a ULA

In this paper, cell searching and DoA (Direction of Arrival) estimation methods are proposed for mobile relay stations with a uniform linear array in OFDM-based cellular systems. The proposed methods can improve the performance of cell searching and DoA estimation, even when there exist symbol timing offsets among the signals received from adjacent base stations and Doppler frequency shifts caused by the movement of the mobile relay station. The performances and computational complexities of the proposed cell searching and DoA estimation methods are evaluated by computer simulation under a mobile WiMAX environment.