Browsing by Author "Chang, Hsiu-Chi"

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An Iterative Weighted Reliability Decoding Algorithm for Two-Step Majority-Logic Decodable Cyclic Codes
(2013-10-01)
Chang, Hsiu-Chi
;
Chen, Chih-Lung
;
Chang, Hsie-Chia
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An iterative weighted reliability two-step majority logic decoding (IWRTS-MLGD) algorithm for two-step majority-logic (TS-MLG)-decodable cyclic codes is presented. In contrast to other message passing decoding algorithms that utilize real number operations, our proposed decoding algorithm requires only logical operations and integer additions. Therefore, large computational complexities can be reduced. For moderate-length TS-MLG-decodable cyclic codes, the proposed algorithm aided with soft information and a scaling factor outperforms the hard-decision TS-MLGD algorithm and hard-decision BCH codes with similar length by 1.2- and 1.0-dB, respectively.
Early-pruned K-best sphere decoding algorithm based on radius constraints
(2008)
Wu, Yi Hsuan
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Liu, Yu Ting
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Chang, Hsiu-Chi
;
Liao, Yen-Chin
;
Chang, Hsie-Chia
A technique to prune the paths for K-best sphere decoding algorithm (SDA) based on radius constraint is presented. The proposed scheme preserves breadth-first searching nature, and the distinct radii for each decoding layer are theoretically derived from the system model with the noise statistics. In addition, based on the data range provided by the radius, a low complexity sorting strategy is proposed. The proposed method can apply to SDA with various path cost functions. Euclidean norm and sum of absolute difference are demonstrated in this paper. With SNR degradation less than 0.2dB, more than 47% and 90% computation complexity can be reduced in 16-QAM and 64-QAM 4 x 4 MIMO detection, respectively.
Iterative Decoding Algorithms for a Class of Non-Binary Two-Step Majority-Logic Decodable Cyclic Codes
(2014-06-01)
Chang, Hsiu-Chi
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Chang, Hsie-Chia
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents two iterative decoding algorithms for a class of non-binary two-step majority-logic (NB-TS-MLG) decodable cyclic codes. A partial parallel decoding scheme is also introduced to provide a balanced trade-off between decoding speed and storage requirements. Unlike non-binary one-step MLG decodable cyclic codes, the Tanner graphs of which are 4-cycle-free, NB-TS-MLG decodable cyclic codes contain a large number of short cycles of length 4, which tend to degrade decoding performance. The proposed algorithms utilize the orthogonal structure of the parity-check matrices of the codes to resolve the degrading effects of the short cycles of length 4. Simulation results demonstrate that the NB-TS-MLG decodable cyclic codes decoded with the proposed algorithms offer coding gains as much as 2.5 dB over Reed-Solomon codes of the same lengths and rates decoded with either hard-decision or algebraic soft decision decoding.
Low-complexity prediction techniques of K-best sphere decoding for MIMO systems
(2007)
Chang, Hsiu-Chi
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Liao, Yen-Chin
;
Chang, Hsie-Chia
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In multiple-input multiple output (MIMO) systems, maximum likelihood (MEL) detection can provide good performance, however, exhaustively searching for the MEL solution becomes infeasible as the number of antenna and constellation points increases. Thus ML detection is often realized by K-best sphere decoding algorithm. In this paper, two techniques to reduce the complexity of K-best algorithm while remaining an error probability similar to that of the ML detection is proposed. By the proposed K-best with predicted candidates approach, the computation complexity can be reduced. Moreover, the proposed adaptive K-best algorithm provides a means to determine the value K according the received signals. The simulation result shows that the reduction in the complexity of 64-best algorithm ranges from 48% to 85%, whereas the corresponding SNR degradation is maintained within 0.13dB and 1.1dB for a 64-QAM 4 x 4 MIMO system.
What Do Smartphone Users Do when They Sense Phone Notifications?
(2017-01-01)
Chang, Yung-Ju
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Chung, Yi-Ju
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Shih, Yi-Hao
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Chang, Hsiu-Chi
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Lin, Tzu-Hao
Smartphone users receive a variety of notifications on their phone every day. To understand how smartphone users deal with notifications, recent mobile receptivity research has started studying notification management and attendance behavior. However, what do smartphone users do when they sense a notification, such as hearing the sound or feeling the vibration before they spot it? We present a study investigating smartphone users' behavior starting from the moment when they sense a notification, including speculating the source and deciding whether and when to look at it, until they attend to it. We explore how users' behaviors vary according to the situation, what factors affect the behaviors, and in what situations users need particular help from a notification system to be better aware of and to accurately judge the source of a notification. We expect the findings will provide useful implications for the design of future notification alert system.