Browsing by Author "Chen, Hung-Chun"

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Bit Allocation and Statistical Precoding for Correlated MIMO Channels With Limited Feedback
(2012-02-01)
Lin, Yuan-Pei
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Chen, Hung-Chun
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Jeng, Panna
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電機工程學系
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Department of Electrical and Computer Engineering
In this paper, we jointly consider statistical precoding and feedback of bit allocation (BA) for multiple-input-multiple-ouput (MIMO) systems over correlated channels. The proposed system will be termed a BA system. We assume that the statistics of the channel is known to the transmitter and a reverse link of very low rate is available so that the receiver can send back the quantized BA. Based on the statistics of the channel, we derive the statistical precoder so that bounds of the error rate averaged over the random correlated channel are minimized. Due to statistical precoding, the distribution of the BA is highly nonuniform. Treating BA as a vector signal, we quantize it using vector quantization (VQ), which is known to be particularly useful for quantizing signals with nonuniform distributions. As the distribution of BA is taken into consideration in the codebook design, a good tradeoff between performance and feedback rate can be achieved. Simulations show that the combination of statistical precoding and VQ-based quantization for BA leads to good performance with a small number of feedback bits.
Differential Feedback of Geometrical Mean Decomposition Precoder for Time-Correlated MIMO Systems
(2017-07-15)
Chen, Hung-Chun
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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
For a time-correlated channel, we consider the differential feedback of the geometrical mean decomposition (GMD) precoder, which is known to be optimal for a number of criteria. When the channel varies slowly, we can expect the optimal GMD precoders of consecutive channel uses to be close. We consider the feedback of the so-called differential precoder and show that it lies in a neighborhood of the identity matrix using matrix perturbation theory. Furthermore, the radius of the neighborhood is shown to be proportional to a time-correlation parameter. Such a characterization allows for subsequent efficient quantization of the differential precoder. We show how to design codewords for the prescribed radius by perturbing the identity matrix and applying QR decomposition on the perturbed matrix. Simulations are given to demonstrate that, with a small feedback rate, the performance of the proposed differential GMD comes close to the case when perfect channel state information is available to the transmitter for slowly time-varying channels like those in indoor and microcellular environments.
FEEDBACK OF DIFFERENTIAL PRECODER FOR GEOMETRICAL MEAN DECOMPOSITION SYSTEMS
(2016)
Chen, Hung-Chun
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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
For a time-correlated channel, we consider the differential feedback of the geometrical mean decomposition (GMD) precoder, which is known to be optimal for a number of criteria. When the channel varies slowly, we can expect the optimal GMD precoders of consecutive channel uses to be close. We consider the feedback of the so-called differential precoder and show that it lies in a neighborhood of the identity matrix using matrix perturbation theory. Furthermore the radius of the neighborhood is proportional to a time-correlation parameter. Such a characterization is crucial for efficient quantization of the differential precoder. Simulations are given to demonstrate that, with a small feedback rate, the performance of the proposed differential GMD comes close to the case when perfect channel state information is available to the transmitter.
FEEDBACK RATE ALLOCATION OF PRECODER AND BIT LOADING FOR MIMO SYSTEMS WITH LIMITED FEEDBACK
(2013)
Chen, Hung-Chun
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Lin, Yuan-Pei
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電機學院
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College of Electrical and Computer Engineering
In this paper we consider feedback rate allocation for MIMO systems with limited feedback of both bit loading and precoder. Allocation of feedback rate is an essential problem when there are two or more kinds of feedback information. We address this issue by analyzing the performance loss due to quantization of precoder and bit loading. We first derive the increase in transmission power when precoder is quantized, and then the additional penalty when bit loading is also quantized. The analysis allows us to find the optimal feedback rate allocation that minimizes the power penalty. Simulations show that the system with proper feedback rate allocation can achieve a very good performance compared with systems that do not consider the feedback of precoder and bit loading jointly.
High Performance and Low power Monolithic Three-Dimensional Sub-50 nm Poly Si Thin film transistor (TFTs) Circuits
(2017-05-02)
Wu, Tsung-Ta
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Huang, Wen-Hsien
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Yang, Chih-Chao
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Chen, Hung-Chun
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Hsieh, Tung-Ying
Development of manufacture trend for TFTs technologies has focused on improving electrical properties of films with the cost reduction to achieve commercialization. To achieve this goal, high-performance sub-50 nm TFTs-based MOSFETs with ON-current (I-on)/subthreshold swing (S.S.) of 181 mu A/mu m/107 mV/dec and 188 mu A/mu m/98 mV/dec for NMOSFETs and PMOSFETs in a monolithic 3D circuit were demonstrated by a low power with low thermal budget process. In addition, a stackable static random access memory (SRAM) integrated with TFTs-based MOSFET with static noise margins (SNM) equals to 390 mV at V-DD = 1.0 V was demonstrated. Overall processes include a low thermal budget via ultra-flat and ultra-thin poly-Si channels by solid state laser crystallization process, chemical-mechanical polishing (CMP) planarization, plasma-enhanced atomic layer deposition (ALD) gate stacking layers and infrared laser activation with a low thermal budget. Detailed material and electrical properties were investigated. The advanced 3D architecture with closely spaced inter-layer dielectrics (ILD) enables high-performance stackable MOSFETs and SRAM for power-saving IoT/mobile products at a low cost or flexible substrate.
Limited Feedback of Precoder and Bit Loading for MIMO Systems: A Joint Design
(2013-12-01)
Chen, Hung-Chun
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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
This paper jointly considers limited feedback of bit loading and precoder. In the past when both precoder and bit loading are fed back to the transmitter, the feedback rate is often allocated between the two using an ad hoc approach and codebooks are designed separately rather than jointly. In this paper we allocate feedback rate in a systematic manner by analyzing the effect of quantization on transmission power. The analysis allows us to obtain the rate allocation that minimizes the power penalty due to limited feedback. As both precoder and bit loading are fed back to the transmitter, the information embedded in one can be exploited for the design of the other. To take advantage of bit loading feedback, which carries valuable information on the importance of individual subchannels, we employ multiple precoder codebooks, each tailored to a bit loading vector in the bit loading codebook. The multi-codebook scheme enjoys significant gain over the single-codebook case that does not take bit loading feedback into consideration. Simulations are given to demonstrate that the proposed system can achieve a very good performance due to carefully designed feedback rate allocation and joint codebook designs.
MULTIPLE PRECODER CODEBOOKS FOR MIMO SYSTEMS WITH LIMITED FEEDBACK OF PRECODER AND BIT LOADING
(2013)
Chen, Hung-Chun
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Lin, Yuan-Pei
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電機學院
;
College of Electrical and Computer Engineering
In this paper we propose to use multiple precoder codebooks for MIMO systems with limited feedback of precoder and bit loading. One precoder codebook is designed for each bit loading vector in the bit loading codebook as bit loading contains information on the importance of individual subchannels. For each precoder codebook, we incorporate the associated bit loading in codebook design to minimize transmission power based on sequential vector quantization. There is no need of informing the transmitter which precoder codebook has been used as the information is conveyed by the bit loading feedback. Due to the exploitation of bit loading information, the proposed multi-codebook scheme outperforms the single-codebook scheme significantly as will be demonstrated by simulations.