Browsing by Author "Hsieh, Wan-Hsin"

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An Approach Attaining Adjustable Designated Footprint
(2009)
Hsieh, Wan-Hsin
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Chang, Chieh-Fu
;
Kao, Ming-Seng
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交大名義發表
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National Chiao Tung University
In satellite communications, the footprint is characterized by contour lines with specific receiving power When data is delivered to the area within a specific footprint, called the designated footprint, illegal users outside the boundary of designated footprint (BDF) can still receive the signal with degraded power. In other words, illegal users can obtain the transmitted data with higher error probability. In this paper, we present a special two-stage serially concatenated (2-SC) coding scheme to more precisely define the designated footprint. Hence users outside the BDF are excluded from obtaining the data, i.e. they cannot correctly decode the data. The key technique, 2-SC coding scheme, achieves the brick-wall effect in error performance regarding bit energy-to-noise density ratio (E(b) / N(0)). The brick-wall effect has sharp cutoff at a critical E(b) / N(0). When the transmitted data is protected by the 2-SC coding scheme, only the users within the designated footprint can successfully decode the data. Otherwise, for users outside the BDF with received E(b) / N(0) slightly less than critical E(b) / N(0), even if the coding structure is known, they cannot correctly decode the data. Thus the BDF is sharply defined by the critical E(b) / N(0). Moreover, by means of purposely-introduced error in the codewords, we can adjust the critical E(b) / N(0) and the BDF. We provide comprehensive analysis of the coding performance and further discuss the application of the proposed scheme to enhance secure satellite communications.(12)
Efficient Acquisition Algorithm for Long Pseudorandom Sequence
(2014-07-01)
Hsieh, Wan-Hsin
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Chang, Chieh-Fu
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Kao, Ming-Seng
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交大名義發表
;
電信工程研究所
In this paper, a novel method termed the phase coherence acquisition (PCA) is proposed for pseudorandom (PN) sequence acquisition. By employing complex phasors, the PCA requires only complex additions in the order of N, the length of the sequence, whereas the conventional method using fast Fourier transform (FFT) requires complex multiplications and additions both in the order of N log(2)N. To combat noise, the input and local sequences are partitioned and mapped into complex phasors in PCA. The phase differences between pairs of input and local phasors are used for acquisition; thus, complex multiplications are avoided. For more noise-robustness capability, the multilayer PCA is developed to extract the code phase step-by-step. The significant reduction of computational loads makes the PCA an attractive method, especially when the sequence length of N is extremely large, which becomes intractable for the FFT-based acquisition.
SNR-Aided Accurate Phase Estimation in 1-Bit Software-Defined Receiver
(2012-04-01)
Hsieh, Wan-Hsin
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Chang, Chieh-Fu
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Kao, Ming-Seng
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電子物理學系
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Department of Electrophysics
This work investigates the high-accuracy phase discriminator in 1-bit software-defined receiver (SDR) for three signal-to-noise ratio (SNR) ranges: low SNR, high SNR and moderate SNR. Unlike traditional approaches, our approach first distinguishes which SNR range an application falls into, and this SNR information is then utilized to select a proper phase discriminator to achieve high accuracy. For low-SNR applications, traditional arctangent phase discriminator (APD) is adopted and the analysis of asymptotic performance is derived. For high-SNR applications, the noise-balanced digital phase discriminator (NB-DPD) is adopted to improve accuracy [1]. Between them, for moderate-SNR applications, a novel SNR-aided phase discriminator (SNRaPD) is proposed. The analytical and simulation results verify the superiority of the proposed approach for applications in different SNR ranges. The determination of moderate SNR range is critical and discussed finally.
Ventricular divergence correlates with epicardial wavebreaks and predicts ventricular arrhythmia in isolated rabbit hearts during therapeutic hypothermia
(2020-02-21)
Hsieh, Yu-Cheng
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Hsieh, Wan-Hsin
;
Li, Cheng-Hung
;
Liao, Ying-Chieh
;
Lin, Jiunn-Cherng
Introduction High beat-to-beat morphological variation (divergence) on the ventricular electrogram during programmed ventricular stimulation (PVS) is associated with increased risk of ventricular fibrillation (VF), with unclear mechanisms. We hypothesized that ventricular divergence is associated with epicardial wavebreaks during PVS, and that it predicts VF occurrence. Method and results Langendorff-perfused rabbit hearts (n = 10) underwent 30-min therapeutic hypothermia (TH, 30 degrees C), followed by a 20-min treatment with rotigaptide (300 nM), a gap junction modifier. VF inducibility was tested using burst ventricular pacing at the shortest pacing cycle length achieving 1:1 ventricular capture. Pseudo-ECG (p-ECG) and epicardial activation maps were simultaneously recorded for divergence and wavebreaks analysis, respectively. A total of 112 optical and p-ECG recordings (62 at TH, 50 at TH treated with rotigaptide) were analyzed. Adding rotigaptide reduced ventricular divergence, from 0.13 +/- 0.10 at TH to 0.09 +/- 0.07 (p = 0.018). Similarly, rotigaptide reduced the number of epicardial wavebreaks, from 0.59 +/- 0.73 at TH to 0.30 +/- 0.49 (p = 0.036). VF inducibility decreased, from 48 +/- 31% at TH to 22 +/- 32% after rotigaptide infusion (p = 0.032). Linear regression models showed that ventricular divergence correlated with epicardial wavebreaks during TH (p<0.001). Conclusion Ventricular divergence correlated with, and might be predictive of epicardial wavebreaks during PVS at TH. Rotigaptide decreased both the ventricular divergence and epicardial wavebreaks, and reduced the probability of pacing-induced VF during TH.