Browsing by Author "Phoong, See-May"

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A Filterbank Approach to Window Designs for Multicarrier Systems
(2007)
Lin, Yuan-Pei
;
Li, Chien-Chang
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Windowing is often applied to multicarrier systems to improve frequency separation among the subcarriers. At the transmitter side better frequency separation leads to a smaller out-of-band spectral leakage and also less interference to radio frequency transmission. At the receiver side better separation gives more suppression of radio frequency interference. As these are frequency based characteristics, a filterbank representation presents a natural and useful framework for formulating the problem. In this work, we propose a unified filterbank approach to the design of windows for multicarrier systems. The filterbank viewpoint provides an additional insight into the transmitter design for spectral leakage reduction as well as to the receiver design for interference suppression. A better frequency separation among the subchannels can be achieved.
A frequency domain based TEQ design for DSL systems
(2006)
Lin, Yuan-Pei
;
Lin, Yu-Pin
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose a frequency domain based design method for designing TEQ (time domain equalizer) for DSL (digital subscriber loops) applications. In DSL applications, usually frequency division multiplexing is used to separate the upstream and downstream signals. In either direction of transmission, some of the frequency bands are not used for transmission. Interference is formulated and minimized in the frequency domain to take advantage of the unused frequency bands. The frequency domain approach allows us to have a more direct control over the frequency response of the resulting TEQ, which is crucial in the final achievable transmission bit rates. The simulation examples demonstrate that the proposed method shortens the channel effectively and very good transmission bit rates can be achieved.
A New Iterative Algorithm for Finding the Minimum Sampling Frequency of MultiBand Signals
(2010-10-01)
Lin, Yuan-Pei
;
Liu, Yi-De
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this correspondence, we propose a new iterative algorithm for finding the minimum sampling frequency of a signal that consists of multiple bandpass signals. This finds important application in software radio where it is desirable to downconvert multiple bandpass signals simultaneously. We will derive a new set of conditions for alias-free sampling. The minimum sampling frequency can be found by iteratively increasing the sampling frequency to meet the alias-free conditions. We will show how the algorithm can be generalized to find alias-free sampling frequency intervals. Simulations will be given to demonstrate the usefulness of the proposed method.
A New Iterative Algorithm for Finding the Minimum Sampling Frequency of MultiBand Signals
(2010-10-01)
Lin, Yuan-Pei
;
Liu, Yi-De
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this correspondence, we propose a new iterative algorithm for finding the minimum sampling frequency of a signal that consists of multiple bandpass signals. This finds important application in software radio where it is desirable to downconvert multiple bandpass signals simultaneously. We will derive a new set of conditions for alias-free sampling. The minimum sampling frequency can be found by iteratively increasing the sampling frequency to meet the alias-free conditions. We will show how the algorithm can be generalized to find alias-free sampling frequency intervals. Simulations will be given to demonstrate the usefulness of the proposed method.
An eigren-based TEQ design for VDSL systems
(2007-01-01)
Lin, Yuan-Pei
;
Liang, Li-Han
;
Chung, Pei-Ju
;
Phoong, See-May
;
電信工程研究所
In this paper, we propose an eigen-based semiblind time-domain equalizer (TEQ) design method for VDSL systems. We exploit the fact that the VDSL system is frequency-division duplexing and maximize signal-to-interference ratio in the frequency domain. Unlike earlier eigen-based TEQ designs, the proposed method does not require the channel impulse response nor channel noise statistics. Using properties of the training symbols in VDSL initialization, the TEQ can be obtained by computing an eigenvector of a positive definite matrix that depends only on the averaged received VDSL symbols. The proposed method is referred to as semiblind, as properties of the training symbols are used but the channel impulse response is not known. Examples will be given to demonstrate that the proposed TEQ design method can effectively shorten the channel impulse response and achieve very good bit rates with only a small number of training symbols.
An Improved ESPRIT-Based Blind CFO Estimation Algorithm In OFDM Systems
(2014)
Pan, Yen-Chang
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電機學院
;
College of Electrical and Computer Engineering
Carrier frequency offset (CFO) is an important issue in orthogonal frequency division multiplexing (OFDM) systems. It destroys the orthogonality between subcarriers and causes degradation in system performance. This paper presents an improved algorithm for the existing ESPRIT-based CFO estimation method. The proposed method estimates the CFO by taking the determinant of a matrix within the ESPRIT algorithm. It is a simple modification to the original ESPRIT-based method and its computational overhead is low. The performance analysis shows that the proposed method can achieve a lower mean square error.
AN ITERATIVE ALGORITHM FOR FINDING THE MINIMUM SAMPLING FREQUENCY FOR TWO BANDPASS SIGNALS
(2009)
Lin, Yuan-Pei
;
Liu, Yi-De
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose an efficient algorithm for finding the minimum sampling frequency for a signal that consists of two bandpass signals. This has important application in software radio where it is desirable to downconvert multiple bandpass signals simultaneously. We will derive a new set of conditions for alias-free sampling that can be checked with few computations. The minimum sampling frequency can be found by iteratively increasing the sampling frequency to meet the alias-free conditions. We will demonstrate that the proposed method has a much lower complexity than previously reported algorithms.
Compensation of IQ imbalance and DC offset for OFDM transmission over frequency selective channels
(2008)
Tseng, Hsien-Yu
;
Cho, Wen-Jen
;
Chang, Ting-Kang
;
Phoong, See-May
;
Lin, Yuan-Pei
In this paper a time-domain method for joint estimation of in-phase and quadrature-phase (IQ) imbalance, direct current (DC) offset and channel response for orthogonal frequency division multiplexing (OFDM) system is proposed. Using the fact that in an OFDM system the block size is usually much larger than the cyclic prefix length, we show that without knowing the channel impulse response, we are able to accurately estimate the IQ mismatch and DC offset, from which the channel response can be obtained. Only one OFDM block is needed for training. Simulation results demonstrate that the performance of the proposed method is very close to the ideal case when IQ mismatch, DC offset and channel response are perfectly known at the receiver.
Design of nonuniform filter bank transceivers for frequency selective channels
(2007)
Chiang, Han-Ting
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In recent years, there has been considerable interest in the theory and design of filter bank transceivers due to their superior frequency response. In many applications, it is desired to have transceivers that can support multiple services with different incoming data rates and different quality-of-service requirements. To meet these requirements, we can either do resource allocation or design transceivers with a nonuniform bandwidth partition. In this paper, we propose a method for the design of nonuniform filter bank transceivers for frequency selective channels. Both frequency response and signal-to-interference ratio (SIR) can be incorporated in the transceiver design. Moreover, the technique can be extended to the case of nonuniform filter bank transceivers with rational sampling factors. Simulation results show that nonuniform filter bank transceivers with good filter responses as well as high SIR can be obtained by the proposed design method. Copyright (c) 2007 Hindawi Publishing Corporation. All rights reserved.
Design of time domain equalizers incorporating radio frequency interference suppression
(2006)
Wu, Ya-Wen
;
Lin, Yuan-Pei
;
Li, Chien-Chang
;
Phoong, See-May
;
電控工程研究所
It is known that radio frequency interference (RFI) degrades the performance of DMT systems for digital subscriber loops. The RFI signal, though narrowband in nature, may be spread to subchannels around the RFI frequencies due to the large sidelobes of the receiving rectangular window. In this paper, we propose a joint consideration of channel shortening and RFI suppression in the design of time domain equalizers (TEQ). We will design the TEQ by minimizing ISI, channel noise and RFI interference. Simulation results are given to show that the proposed method can considerably reduce interference around the RFI frequencies and increase the transmission rate.
FEEDBACK FOR TIME-CORRELATED MIMO-OFDM SYSTEM USING PREDICTIVE QUANTIZATION OF BIT LOADING AND SUBCARRIER CLUSTERING
(2015)
Lin, Yuan-Pei
;
Chou, Tzu-Hsuan
;
Phoong, See-May
;
電機工程學系
;
Department of Electrical and Computer Engineering
In the paper, we consider limited feedback for a MIMO-OFDM system over a time-correlated multipath fading channel. Due to time correlation, the subcarriers are correlated in both time and frequency. We propose the use of predictive quantization of bit loading (PQB) and subcarrier clustering (SC). Applying PQB on the subcarriers allows us to exploit the time correlation of the channel and adapt the transmission rate according to the channel condition while SC enables us to take advantage of the frequency correlation of the channel. Simulation results are given to demonstrate that the proposed feedback scheme can achieve a good performance due to the exploitation of both time and frequency correlation.
Filterbank framework for multicarrier systems with improved subcarrier separation
(2006)
Lin, Yuan-Pei
;
Li, Chien-Chang
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Frequency separation among the subcarriers is of great importance for multicarrier systems. At the transmitter side better frequency separation leads to a smaller out-of-band spectral leakage and also less interference to radio frequency transmission. At the receiver side better separation gives more suppression of radio frequency interference. As these are frequency based characteristics, a filterbank representation renders a natural tool for formulating the problem. In this work, we will consider a filterbank framework for designing multicarrier systems with improved subcarrier separation.
FINDING THE MINIMUM SAMPLING FREQUENCY OF MULTI-BRAND SIGNALS: AN EFFICIENT ITERATIVE ALGORITHM
(2010)
Lin, Yuan-Pei
;
Liu, Yi-De
;
Phoong, See-May
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose an efficient iterative algorithm for finding the minimum sampling frequency for a signal that consists of multiple bandpass signals. This finds important application in software radio where it is desirable to down-convert multiple bandpass signals simultaneously. We will derive a new set of conditions for alias-free sampling for signals that contain multi-band signals. The conditions can be easily examined with few computations. The minimum sampling frequency can be found by iteratively increasing the sampling frequency can be found by iteratively increasing the sampling frequency to meet the alias-free conditions. The simulations demonstrate that the proposed method required a much lower complexity than existing algorithms.
ISI-free block transceivers for unknown frequency selective channels
(2007-04-01)
Liu, Chih-Hao
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The orthogonal frequency-division multiplexing (OFDM) transceiver has enjoyed great success in many wideband communication systems. It has low complexity and robustness against channel-induced intersymbol interference (ISI). When the channel order does not exceed the length of cyclic prefix, any frequency-selective channel is converted to a set of frequency-nonselective subchannels. This channel-independent ISI-free property is useful for many applications. In this correspondence, we study general block transceiver with such a property. We will show that the solutions of channel-independent ISI-free block transceivers are given in a closed form. It is found that except for some special cases, the solutions are identical to the Lagrange-Vandermonde and Vandermonde-Lagrange transceivers.
Joint Estimation of CFO and Receiver I/Q Imbalance Using Virtual Subcarriers for OFDM Systems
(2012)
Chang, Chao-Wei
;
Chung, Yuan-Hwui
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電機工程學系
In this paper, we study the estimation of carrier frequency offset (CFO) in the presence of the receiver in-phase and quadrature-phase (I/Q) imbalance for orthogonal frequency division multiplexing (OFDM) systems. By minimizing the energy of the samples on the virtual subcarriers, our proposed algorithm can jointly estimate the CFO and I/Q parameters using one OFDM block. When the CFO is small, a closed-form solution can be obtained. Simulation results show that our proposed method can provide a good performance for both of the I/Q and CFO estimation and it compares favorably with a recent method.
Multirate systems and applications
(2007)
Lin, Yuan-Pei
;
Phoong, See-May
;
Selesnick, Ivan
;
Oraintara, Soontorn
;
Schuller, Gerald
On the design of cmfb transceivers for unknown channels
(2006)
Liu, Chih-Hao
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we consider the cosine modulated filter bank (CMFB) transceiver for unknown channels. Although it is a CMFB transceiver, the only channel dependent part of the transceiver is a set of scalar Multipliers at the receiver, like the OFDM. We show how to optimize the transmit and receive prototype filters so that the signal to interference ratio (SIR) is maximized. Moreover a new objective function that can incorporate the frequency response criteria is proposed. Simulation results show that we can obtain CMFB transceivers with high SIR values and good frequency responses.
Statistical Bit Allocation and Statistical Precoding for Correlated MIMO Channels With Decision Feedback
(2012-11-01)
Lin, Yuan-Pei
;
Phoong, See-May
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this letter, we jointly consider statistical precoding and statistical bit allocation for correlated MIMO channels. Given the statistics of the channel, we derive statistical BER bounds for high and low SNR ranges. Based on the BER bounds, statistical precoder and statistical bit allocation are designed. The statistical precoder helps to expose the statistical difference among the subchannels, which is then exploited by bit allocation. Moreover, we will incorporate bit allocation in determining detection ordering for the decision feedback receiver and present a suboptimal ordering forminimizing the worst subchannel error rate. The suboptimal solution can be implemented efficiently by modifying existing fast algorithms developed for uniform bit allocation. Although the statistical precoder and bit allocation are designed for high and low SNR ranges, very good performance can be achieved for all SNR. Simulations show that the performance of the proposed system is comparable to one that has instantaneous feedback rate of around 4 bits per channel.
STATISTICS-AIDED CODEBOOK DESIGNS FOR LIMITED FEEDBACK BEAMFORMING SYSTEMS OVER MILLIMETER WAVE CHANNELS
(2018-01-01)
Lin, Yuan-Pei
;
Wu, Po-Hsien
;
Phoong, See-May
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we consider statistics-aided beamformer code book designs for millimeter wave (mmWave) channels with limited feedback. The dimension of the beamformer, which scales with the number of transmit antenna, is typically large in mmWave systems and a large dimension adds to the difficulty of codebook designs. Two low-cost design methods are proposed. The first one, a VQ based approach, reduces the dimensionality of the codebook design problem by using training AoDs (angles of departure) instead of training channels. The second one, requiring no codebook training, designs the beamformer codebook from the statistics of the channel alone based on spectral analysis of the channel. Simulations are given to demonstrate the usefulness of the proposed methods.
SUBBAND ADAPTIVE FILTERING USING APPROXIMATELY ALIAS-FREE COSINE MODULATED FILTERBANKS
(2008)
Chang, Yin-Shao
;
Phoong, See-May
;
Lin, Yuan-Pei
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we use a class of cosine modulated filter-ank (CMFB) with approximately reconstruction property for subband adaptive filtering. We show that even after the subband filters are included, the CMFB maintains the approximately alias-free property. In earlier designs, when the filterbank has real coefficients, the alias-free property is usually destroyed after subband filters are inserted. The CMFB has real coefficients and the computational complexity for filtering and subband adaptation is less than that of complex-valued filterbanks. Numerical simulations will be given to demonstrate its approximately alias-free property and fast convergence.