Browsing by Author "Lin, Chia-Hua"

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A Novel Sub-Nyquist Sampling of Sparse Wideband Signals
(2013)
Lin, Chia-Hua
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Tsai, Shang-Ho
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Chuang, Gene C. H.
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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
We propose a Sub-Nyquist sampling scheme using only one mixer, one filter bank with M subfilters and M low rate ADCs. Compared to the MWC (Modulated Wideband Converter) system in [1], the proposed sampling system has several complexity advantages. First, due to the use of only one mixer, the hardware complexity for analog circuits is significantly reduced. Moreover, the system only needs one PN sequence and thus the search complexity for the best sequence is greatly reduced. The use of the best sequence enables the proposed system to achieve a smaller mean square error (MSE) between the original and the reconstructed signals than that of the MWC system. Simulation results are provided to show the performance superiority of the proposed system in terms of MSE and recovery percentage.
Interplay of Template Constraints and Microphase Separation in Polymeric Nano-Objects Replicated from Novel Modulated and Interconnected Nanoporous Anodic Alumina
(2018-01-01)
Bayat, Haider
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Lin, Chia-Hua
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Cheng, Ming-Hsiang
;
Steuber, Marc
;
Chen, Jiun-Tai
We report on a versatile strategy to fabricate shape-controlled polymeric nano-objects with an internal compartmentalized structure by replication from pore-diameter-modulated and interconnected nanoporous anodized aluminum oxide (AAO). The AAO with modulated pore diameters is synthesized in a refined temperature-modulated hard anodization (TMHA) approach, by alternating the flow rate of an air stream cooling the electrolyte. Through pore-widening of the templates with modulated pore diameters, a stable interconnected 3D network with transversal ellipsoidal holes is fabricated as a second template structure. From these unprecedented template structures exhibiting modulated pores and an intricate 3D network structure, shape-controlled polymeric nano-objects are replicated using the melt wetting method with polystyrene homopolymer (PS) and cylinder-forming block copolymer polystyrene-block-polydimethylsiloxane (PS298-b-PDMS195). The replicated nanostructures are separated into individual anisotropically shaped nanocapsules by passing the replicas through a polycarbonate membrane followed by gentle sonication. Inside the nano-objects, the microphase separation of PS298-b-PDMS195 affords parallel aligned nanophases, in which domain sizes and morphologies are different compared to the unconfined bulk according to transmission electron microscopy analyses. These advanced AAO platforms and the nanoscale polymer replicas offer new routes for compartmentalized nano objects with potential future relevance for applications ranging from drug nanocarriers to biosensors.
On Quantization for Masked Beamforming Secrecy Systems
(2015-10-01)
Lin, Chia-Hua
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Tsai, Shang-Ho
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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 study investigates how to quantize the masked beamforming systems to maximize the secrecy rate for MISOSE (multiple-input, single-output, single-eavesdropper) channels and assume that this eavesdropper equipped with only single antenna, where only partial channel state information (CSI) at the legitimate receiver is available to the transmitter. In this case, the artificial noise (AN) leaks to the legitimate receiver due to CSI quantization. In the literature, all quantization bits are used to quantize the beamforming vector. Then the null space of this quantized beamforming vector is used to transmit the AN. We find that such quantization schemes can result in serious interference at the legitimate receiver. To overcome this issue, we propose that the beamforming vector and the AN vector should be quantized separately, where the beamforming vector should be selected from a codebook to maximize the beamforming gain and the AN vector should be selected from another codebook to minimize the leakage (or interference). Theoretical results show that separate quantization can significantly reduce the AN leakage at the legitimate receiver. Furthermore, based on the proposed quantization scheme, we show how to allocate bits to separately quantize the beamforming vector and the AN vector to maximize the secrecy rate. By using the proposed quantization and bit allocation schemes, the secrecy rates of masked beamforming systems can be improved compared to the conventional quantization schemes. Simulation results corroborate the theoretical results.
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
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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)
;
Lin, Yuan-Pei
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電機工程學系
;
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.