Browsing by Author "Tsai, Shang-Ho (Lawrence)"

Now showing 1 - 14 of 14

A NOVEL SYSTEM AND STATISTICAL ANALYSIS FOR PREDICTING DEFIBRILLATION TIMING DURING VENTRICULAR FIBRILLATION
(2018-01-01)
Tsai, Shang-Ho (Lawrence)
;
Tsai, Min-Shan
;
Jiang, Yu-Chen Fan
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work proposes a new algorithm and analytical methods for predicting the successful rate of a defibrillation during ventricular fibrillation. Accurate predictions help in improving outcomes of cardiopulmonary resuscitation. This also helps in finding a good defibrillation timing to avoid ineffective defibrillation, which leads to myocardial damages and thus a poor prognosis after the resuscitation. Simulation results show that the proposed algorithm outperforms conventional methods in terms of several commonly used performance indices; meanwhile, the proposed analysis also well matches the practical experimental results.
An Equal Gain Transmission in MIMO Wireless Communications
(2010)
Tsai, Shang-Ho (Lawrence)
;
電機工程學系
;
Department of Electrical and Computer Engineering
The maximum SNR loss between equal gain transmission (EGT) and the optimal scheme, i.e. maximum ratio transmission (MRT) is 1.05 dB in MISO channels. However, little is known about the performance loss of EGT in MIMO channels, since there is no simple closed-form solution available for the best EGT in MIMO channels. In this study, an EGT design for MIMO channels is proposed and its performance is analyzed theoretically. Interestingly, the SNR loss between the proposed EGT and the MRT in MIMO channels is shown to be at most 1.05 dB as well. Unlike the optimal MRT, which requires both magnitude and phase information of channels, EGT only needs phase information and hence has several implementional advantages compared to the MRT; that is, it can greatly relax the effort of power amplifier and computational complexity. Consequently, simple transceiver design can be realized using the proposed EGT with small performance degradation.
Beamforming with no instantaneous feedback for mmWave transmission
(2017-01-01)
Lin, Yuan-Pei
;
Tsai, Shang-Ho (Lawrence)
;
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 statistical beamforming for millimeter wave (mmWave) channels. For a commonly used geometry channel model of uniform planar array (UPA), we show that the average channel Gram matrix can be approximated in a closed form, which allows the statistical beamformer to be computed directly. The sparse nature of the mmWave channel lends itself to statistical beamforming as the optimal beamformer that uses full channel information is typically steered in some spatial frequency determined by the statistics. Simulations are given to show that the performance of the proposed statistical beamformer that needs no instantaneous feedback is comparable to a limited feedback system with 1/8 feedback bits per antenna.
Beamforming with no instantaneous feedback for mmWave transmission
(2017-01-01)
Lin, Yuan-Pei
;
Tsai, Shang-Ho (Lawrence)
;
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 statistical beamforming for millimeter wave (mmWave) channels. For a commonly used geometry channel model of uniform planar array (UPA), we show that the average channel Gram matrix can be approximated in a closed form, which allows the statistical beamformer to be computed directly. The sparse nature of the mmWave channel lends itself to statistical beamforming as the optimal beamformer that uses full channel information is typically steered in some spatial frequency determined by the statistics. Simulations are given to show that the performance of the proposed statistical beamformer that needs no instantaneous feedback is comparable to a limited feedback system with 1/8 feedback bits per antenna.
Carrier Frequency Offset Estimation Algorithm for OFDM-Based Multi-cell Systems
(2014)
Hung, Ying-Che
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Peng, Sheng-Yuan
;
Tsai, Shang-Ho (Lawrence)
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we propose an algorithm for estimating the carrier frequency offset (CFO) in OFDM-based multi cell networks. In 3GPP-LTE single-cell systems, the CFO can be estimated by applying the Schmidt algorithm. However, multi cell interference (MCI) is induced in multi-cell environments; as a result the MCI degrades estimate accuracy. One solution to mitigate MCI may be via properly designing the training sequences. In this paper, we propose a method for generating training sequences with good orthogonality in both time and frequency domain. Therefore, MCI can be effectively suppressed and CFO estimation algorithms designed for single-user or single cell environments can be slightly modified, and applied in multi cell environments. An example is given for showing how to modify the estimation algorithms. Consequently, the computational complexity can be dramatically reduced. Moreover, the training sequences can be applied for detecting cell identity (ID) thanks to its good orthogonality. Simulation results show that the proposed sequences and the CFO estimation algorithms outperform conventional schemes in multi-cell environments.
PAPR Analysis and Mitigation Algorithms for Beamforming MIMO OFDM Systems
(2014-05-01)
Hung, Ying-Che
;
Tsai, Shang-Ho (Lawrence)
;
電機工程學系
;
Department of Electrical and Computer Engineering
Beamforming (or precoding) techniques have been widely adopted in modern MIMO OFDM systems. Using beamforming can significantly improve the receive SNR of OFDM systems. However, the combination of transmit signals after beamforming deteriorates the peak-to-average power ratio (PAPR), which has long been considered a major issue of OFDM systems. High PAPR not only complicates the design of the power amplifier, but also increases power consumption. In this paper, we theoretically analyze the PAPR performance of MIMO OFDM systems that adopt either one of the two popular beamforming schemes, i.e. MRT (maximum ratio transmission) and EGT (equal gain transmission). The analysis considers different numbers of channel taps after sampling. The results may provide important reference for practical designs when evaluating the required power amplifiers and power consumption. Moreover, the theoretical results show that MRT OFDM systems generally perform much worse than EGT OFDM systems in terms of PAPR. Furthermore, motivated from the derived results, PAPR reduction algorithms are proposed for both MRT OFDM and EGT OFDM systems. It is worth to mention that for MRT OFDM systems, the proposed algorithm can improve both PAPR and bit error rate; for EGT OFDM systems, the proposed algorithm improves PAPR while it only slightly degrades bit error rate.
PREDICTING DEFIBRILLATION OUTCOME IN VENTRICULAR FIBRILLATION USING ECG WITH NEURAL NETWORK ALGORITHM
(2019-01-01)
Tsai, Shang-Ho (Lawrence)
;
Tsai, Min-Shan
;
Huang, Hsin-Chi
;
Ling, Dean-Chang (Ash)
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電子工程學系及電子研究所
This work proposes a system to predict the outcomes of the defibrillation during the period of ventricular fibrillation. Accurate outcomes can avoid inefficient defibrillation that causes severe myocardial injury. In this system, we apply a neural network model and use the frequency components of ECG signals as training data to determine the neuron coefficients. The trained system is then validated (tested) using different set of data to justify the performance. Experimental results are provided to show superior performance of the proposed system.
Reducing Jitter Effects for Multiband Bandpass Sampling Systems
(2015)
Chen, Kuan-Chun
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Tsai, Shang-Ho (Lawrence)
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Multiband bandpass sampling techniques have been widely used in Soft Define Radio (SDR) systems. The performance of systems using bandpass sampling is highly affected by jitter effects. This work investigates jitter effects for multiband bandpass sampling systems, and proposes a receiver that applies a two-stage method for combating the jitter effect. At the first stage, a maximum likelihood pilot-aided algorithm is used to estimate and compensate the dominated jitter. Then, at the second stage, we exploit the oversampled property of the received signal and propose a decimate-and-average scheme to further mitigate the residual jitter effect. Simulation results show that the proposed system can significantly reduce the jitter effect.
Resource Allocation and Minimum Rate for Precoded Non-orthogonal Multiple Access
(2017-01-01)
Chen, Chih-Chiang
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Tsai, Shang-Ho (Lawrence)
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Lin, Yuan-Pei
;
Lin, Chia-Hua
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電機工程學系
In this paper, we propose user clustering and power allocation algorithms for a precoded NOMA system. The user clustering for the strong and the weak users, and corresponding power allocation can be optimized disjointedly when SNR is sufficiently high, and this leads to a great reduction in computational complexity. Moreover this proposed power allocation algorithm can maximize sum achievable rate subject to a minimum target rate. Furthermore, from the analytical results, we suggest a reasonable minimum target rate for the weak user so that this rate can always be achieved, i.e, with outage probability 1. Using the suggested target rate, the NOMA system can avoid failing in achieving this target rate even if all power is allocated to the weak user. Simulation results corroborate theoretical results.
Secure MIMO Transmission via Compressive Sensing
(2015)
Lin, Chia-Hua
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Tsai, Shang-Ho (Lawrence)
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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
In this paper, we propose a MIMO precoding transceiver to achieve data secrecy at the physical layer. The proposed system exploits the Restricted Isometry Property (RIP) widely used in compressive sensing to encrypt the data. Because the channels at the legitimate receiver and the eavesdropper are inherently different, the corresponding sensing matrices are different. Thus the eavesdropper cannot decode the data successfully. More specifically, when full channel state information (CSI) at the legitimate receiver is known to the transmitter, the proposed precoder can simultaneously maximize receive SNR and attain secrecy. Simulation results corroborate theoretical results, and show that the proposed system enjoys different advantages when different recovery algorithms are used.
Secure Transmission Using MIMO Precoding
(2014-05-01)
Lin, Chia-Hua
;
Tsai, Shang-Ho (Lawrence)
;
Lin, Yuan-Pei
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we propose an MIMO precoding and postcoding transceiver to achieve data secrecy at the physical layer. When full channel state information (CSI) of the legitimate receiver is known to the transmitter, the proposed precoder can simultaneously maximize to receive signal-to-noise ratio (SNR) and attain secrecy. When only partial CSI is available, a modified Lloyd algorithm is proposed to construct codebooks for quantizing the precoder. As will be explained in this paper, the use of the proposed codebooks does not affect the secrecy of the proposed system. In addition, we propose a low-complexity postcoder to compensate the SNR loss when full CSI is not available. Furthermore, the performance of the proposed system is analyzed from the view points of both recovery rate and secrecy. Based on the analyzed results, we show how to achieve full recovery rate and perfect secrecy for the proposed system. Finally, simulation results corroborate the theoretical results, and show that the proposed system enjoys different advantages when different recovery algorithms are used.
Sequence Designs for Interference Mitigation in Multi-Cell Networks
(2014-01-01)
Hung, Ying-Che
;
Peng, Sheng-Yuan
;
Tsai, Shang-Ho (Lawrence)
;
電機工程學系
;
Department of Electrical and Computer Engineering
We propose a training sequence that can be used at the handshaking stage for multi-cell networks. The proposed sequence is theoretically proved to enjoy several nice properties including constant amplitude, zero autocorrelation, and orthogonality in multipath channels. Moreover, the analytical results show that the proposed sequence can greatly reduce the multi-cell interference (MCI) induced by carrier frequency offset (CFO) to a negligible level. Therefore, the CFO estimation algorithms designed for single-user or single-cell environments can be slightly modified, and applied in multi-cell environments; an example is given for showing how to modify the estimation algorithms. Consequently, the computational complexity can be dramatically reduced. Simulation results show that the proposed sequences and the CFO estimation algorithms outperform conventional schemes in multi-cell environments.
THIC STRUCTURES FOR RF BEAMFORMING
(2017-01-01)
Lin, Yuan-Pei
;
Tsai, Shang-Ho (Lawrence)
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Recently it is shown that the maximum MIMO beamforming gain can be achieved using only one RF (radio frequency) chain. This is done by implementing the beamformer using Two analog pHase shIfters for each Coefficient (THIC). In this paper we analyze the quantization error of the beamforming coefficients (weights) when the phase shifters used in THIC are of finite resolution. An alternative THIC structure is proposed. The new structure, having the same beamforming gain when the phases can take on continuum values, behaves differently upon quantization. It can achieve a smaller quantization error through proper allocation of quantization bits between the two phase shifters. Simulations are given to demonstrate that a performance very close to the full MIMO beamforming gain can be achieved using phase shifters of low resolution.
THIC STRUCTURES FOR RF BEAMFORMING
(2017-01-01)
Lin, Yuan-Pei
;
Tsai, Shang-Ho (Lawrence)
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Recently it is shown that the maximum MIMO beamforming gain can be achieved using only one RF (radio frequency) chain. This is done by implementing the beamformer using Two analog pHase shIfters for each Coefficient (THIC). In this paper we analyze the quantization error of the beamforming coefficients (weights) when the phase shifters used in THIC are of finite resolution. An alternative THIC structure is proposed. The new structure, having the same beamforming gain when the phases can take on continuum values, behaves differently upon quantization. It can achieve a smaller quantization error through proper allocation of quantization bits between the two phase shifters. Simulations are given to demonstrate that a performance very close to the full MIMO beamforming gain can be achieved using phase shifters of low resolution.