Browsing by Author "Li, Chien-Chang"

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A Filterbank Approach to Window Designs for Multicarrier Systems
(2007)
Lin, Yuan-Pei
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Li, Chien-Chang
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Phoong, See-May
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電控工程研究所
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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.
Design of time domain equalizers incorporating radio frequency interference suppression
(2006)
Wu, Ya-Wen
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Lin, Yuan-Pei
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Li, Chien-Chang
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Phoong, See-May
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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.
Filterbank framework for multicarrier systems with improved subcarrier separation
(2006)
Lin, Yuan-Pei
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Li, Chien-Chang
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Phoong, See-May
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電控工程研究所
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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.
On the Duality of MIMO Transceiver Designs With Bit Allocation
(2011-08-01)
Li, Chien-Chang
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Lin, Yuan-Pei
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電機工程學系
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Department of Electrical and Computer Engineering
Bit rate and power are two commonly used optimality criteria for MIMO transceiver design. In the literature, bit rate maximization and power minimization problems are viewed as different problems and solved independently. In this paper, we derive the duality between these two problems for both the cases with and without integer constraint on bit allocation. We will show that if a transceiver is optimal for the power-minimizing problem, it is also optimal for the rate maximizing problem, and the converse is true. Such a duality has not been stated and proved in the literature to the best of our knowledge. The derivation does not involve any existing optimal solution and we can establish duality result even for the rate maximization problem with integer bit constraint, which the optimal solution is not known. The duality also allows us to develop an algorithm for finding the rate-maximizing transceiver with integer bit allocation using the solution of power-minimizing system. We will also consider some possible generalizations of the problem, for example, when there is a constraint on the maximal constellation size and when the subchannel bit error rates (BERs) are constrained. For each of these cases, we will see that the duality between the two problems continued to hold. In the simulations, we will compute the optimal solutions for these two problems and demonstrate the duality between these two.
Optimization of Transceivers with Bit Allocation to Maximize Bit Rate for MIMO Transmission
(2009-12-01)
Li, Chien-Chang
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Lin, Yuan-Pei
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Tsai, Shang-Ho
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Vaidyanathan, P. P.
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交大名義發表
There have been many results on designing transceivers for MIMO channels. In early results, the transceiver is designed for a given bit allocation. In this paper we will jointly design the transceiver and bit allocation for maximizing bit rate. By using a high bit rate assumption, we will see that the optimal transceiver and bit allocation can be obtained in a closed form using simple Hadamard inequality and the Poincare separation theorem. In the simulation, we will demonstrate the usefulness of the joint design. Simulation results, in which a high bit rate assumption is not used in allocating bits, show that a higher bit rate can be achieved compared to previously reported methods.
Predictive Coding of Bit Loading for Time-Correlated MIMO Channels With a Decision Feedback Receiver
(2015-07-01)
Li, Chien-Chang
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Lin, Yuan-Pei
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we consider variable-rate transmission over a slowly varying multiple-input multiple-output (MIMO) channel with a decision feedback receiver. The transmission rate is adapted to the channel by dynamically assigning bits to the subchannels of the MIMO system. Predictive quantization is used for the feedback of bit loading to take advantage of the time correlation inherited from the temporally correlated channel. Due to the use of decision feedback at the receiver, the bit loading is related to the Cholesky decomposition of the channel Gram matrix. Assuming the channel is modeled by a slowly varying Gauss-Markov process, we show that the nested submatrices generated during the process of Cholesky decomposition can be updated as time evolves. Based on the update, we derive the optimal predictor of the next bit loading for predictive quantization. Furthermore, we derive the statistics of the prediction error, which are then exploited to design the quantizer to achieve a smaller quantization error. Simulations are given to demonstrate that the proposed predictive quantization gives a good approximation of the desired transmission rate with a low feedback rate.
STATISTICAL DESIGNS FOR TRANSMISSION OVER CORRELATED MIMO CHANNELS WITH LINEAR RECEIVERS
(2012)
Lin, Yuan-Pei
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Hsiao, Chunwei
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Li, Chien-Chang
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電機學院
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College of Electrical and Computer Engineering
In this paper we jointly consider statistical precoding and statistical bit allocation for transmission over correlated MIMO (multiple-input and multiple-output) channels with a linear and zero forcing receiver. Assuming the statistics of the channel is available to the transmitter, we will derive BER bounds using the statistics of subchannel error variances. The bounds are then used to design statistical precoder and statistical bit allocation. The combination of statistical precoding and bit allocation has great advantage over statistical precoding alone or statistical bit allocation alone. This is because the proposed precoding helps to bring out the statistical difference among the subchannels, which is then exploited by statistical bit allocation to better the performance. Simulations will be given to demonstrate that, the proposed system has significant gain over statistical designs that employs statistical precoding only or statistical bit allocation only.