Browsing by Author "Chen, Chih-Liang"

Now showing 1 - 8 of 8

A joint synchronization algorithm for OFDM systems
(2007)
Chin, Wen-Long
;
Chen, Sau-Gee
;
Chen, Chih-Liang
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work presents a joint maximum-likelihood (ML) synchronization algorithm for symbol time (ST) offset (STO), carrier frequency offset (CFO) and sampling clock frequency offset (SCFO) for OFDM systems. Unlike most existing techniques which are time-domain approaches considering only AWGN and/or static multipath conditions, the proposed algorithm is developed in frequency-domain under time-variant multipath channels. By analyzing the received frequency-domain data, a mathematical model for the joint effects of STO, CFO and SCFO is derived. The results are used to formulate a log-likelihood function of two consecutive symbols. Based on the function, a joint ML algorithm is proposed. The joint algorithm is both efficient and robust, because the three main synchronization issues are treated altogether. Simulation results exhibit high performances in time-variant multipath fading channels.
An Efficient Cell Search Algorithm for Preamble-based OFDM Systems
(2008)
Chen, Chih-Liang
;
Chen, Sau-Gee
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
For cellular mobile telecommunication, cell identification is an indispensable initial process to establish a communication link. Cell identification requires high computational complexity and accuracy in a short time, especially during the handover process. To achieve high-performance cell identification with low-complexity for the orthogonal frequency division multiplexing (OFDM) systems, this work proposes an efficient cell ID search technique. Simulation results show that the proposed cell ID search method has better performance and lower computational complexity than conventional methods, in multipath Rayleigh fading channels.
Energy-Bandwidth Efficiency Tradeoff in MIMO Multi-Hop Wireless Networks
(2011-09-01)
Chen, Chih-Liang
;
Stark, Wayne E.
;
Chen, Sau-Gee
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper considers a MIMO multi-hop network and analyzes the relationship between its energy consumption and bandwidth efficiency. Its minimum energy consumption is formulated as an optimization problem. By taking both transmit antennas (TAs) and receive antennas (RAs) into consideration, the energy-bandwidth efficiency tradeoff in the networks is investigated. Moreover, the minimum energy of an equally-spaced relaying strategy is investigated for various numbers of antennas. In addition, the minimum energy over all possible antenna pairs is derived. Finally, the effect of the number of hops on the energy-bandwidth efficiency tradeoff is considered. For a fixed antenna pair, the minimum energy over all possible rates and hop numbers are obtained. Generally, the routes with more hops minimize the energy consumption in the low effective rate region. On the other hand, in the high effective rate region, the routes with fewer hops minimize the energy consumption.
LOW-COMPLEXITY AND HIGH-PERFORMANCE NON-COHERENT CELL IDENTIFICATION DETECTION SCHEMES FOR OFDM-BASED SYSTEMS
(2013)
Lin, Ying-Tsung
;
Wang, Yi-Hsiang
;
Chen, Sau-Gee
;
Chen, Chih-Liang
;
電子工程學系及電子研究所
This work proposes two low-complexity and high-performance cell ID detection schemes for cellular communication systems. The first one, called real-correlation multiple differential detection (RMDD), derived from our previous work on cell ID detection called CERCD method, has much less complex multiplication operations while maintains the same performance. Although CERCD algorithm is more robust than existing cell detection methods in AWGN and multipath channel conditions, its performance still can be further improved. As such, the second scheme, called multiple differential detection (MDD), is proposed to improve CERCD method. Simulation results show that MDD has much better performance in frequency-selective channels. Performances and computational complexities of proposed schemes are also evaluated and analyzed under different channel environments to demonstrate their effectiveness.(1)
Low-complexity successive detection method for OFDM systems over doubly selective channels
(2007)
Chen, Chih-Liang
;
Chen, Sau-Gee
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Orthogonal frequency division multiplexing (OFDM) system is robust against inter-symbol interference (ISI) by increasing the symbol duration. However, for high-speed application, time variation of a multipath channel result in inter-carrier interference (ICI). It leads to the performance degradation. This works propose a low-complexity successive detection algorithm combined with the techniques of Newton's iterative matrix inversion method and successive detection method according to signal to noise ratio (SNR) in OFDM system. With the assumption of linearly varying channel impulse responses under fast fading conditions, the proposed algorithm reduces the complexity from O(N-3) of conventional zero-forcing algorithm to O(N-2), meantime it mitigates the noise enhancement problem. In all, it surpasses the performance bound of zero-forcing (ZF) equalization.
Modeling and Verification of a Diamond-Shape Narrow-Tilting Vehicle
(2008-12-01)
Chiou, Jin-Chern
;
Chen, Chih-Liang
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The authors use planar multibody system dynamics to model an intelligent personal mobility (IPM) narrow-tilting vehicle (NTV) with four wheels arranged in a diamond configuration. A planar multibody system tire model is used to represent ground-vehicle interaction. In addition to analyzing the roll plane dynamics, the proposed model supports the measuring of joint reaction forces (a difficult task with actual vehicles) to assist in advanced controller and mechanical system design. We also propose a separate calculation method using two acceleration sensors and one angular position sensor for the purpose of obtaining ground forces. Results from model verification tests (i.e., comparisons with actual data from a slalom test) indicate that the proposed IPM model performed with a high degree of accuracy.
Non-Coherent Cell Identification Detection Methods and Statistical Analysis for OFDM Systems
(2010-11-01)
Chen, Chih-Liang
;
Chen, Sau-Gee
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
To achieve high-performance cell identification detection with low complexity for orthogonal frequency division multiplexing (OFDM) systems, this work proposes an efficient non-coherent cell identification (ID) detection technique based on a new optimization metric. Furthermore, the metric is simplified to two lower-complexity metrics. As such, two more modified cell ID detection methods extended from the first one are also proposed. Experiments show that all the three new cell ID methods achieve better performances than the conventional methods in multipath Rayleigh fading channels. This work also conducts the statistical analysis to characterize the proposed techniques completely. It is shown that the results of the theoretical analysis are close to the simulation results. Among the new techniques, specifically, the third proposed method using the second simplified new metric has much lower complexity and higher performance than the conventional methods.
Tilting Motion Control in Narrow Tilting Vehicle Using Double-Loop PID Controller
(2009)
Chiou, J. C.
;
Lin, Chun-Ying
;
Chen, Chih-Liang
;
Chien, Chin-Pin
;
電控工程研究所
This paper presents an electric narrow tilting vehicle (NTV), which is named Intelligent Personal Mobility (IPM). It can tilt to prevent from rollover. The tilting control strategy is also proposed and implemented by double-loop PID controller in this paper, the first loop controls the tilting rate, and the second loop which encloses the first loop controls the tilting position. This double-loop PIID controller was verified by working with IPM multibody model which had been verified by comparing with IPM in slalom tests. This approach can be adopted to solve instable problems of the others NTV systems.