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1,108 results on '"Chen, Hsiao-Hwa"'

204. Smart Grids

Author

Wietfeld, Christian, primary, Cardenas, Alvaro A., additional, Chen, Hsiao-Hwa, additional, Popovski, Petar, additional, and Wong, Vincent W. S., additional

Published
2017
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224. The REAL Approach to Generate Orthogonal Complementary Codes for Next Generation CDMA Systems (Special Issue on Next Generation Network Technologies)

Author

Chen, Hsiao-Hwa

Subjects
Computer Science::Information Theory
Abstract

This paper introduces a new approach to generate the orthogonal complementary (OC) codes suitable for new generation CDMA applications, characterized by isotropic multiple access interference (MAI) free and multipath interference (MI) free properties. The code design methodology proposed in this paper is named as “Real Environment Adaptation Linearization" (REAL) approach and it takes into account major impairing factors existing in real applications, such as MAI, MI, asynchronous transmissions and random signs in consecutive symbols. A CDMA system using the generated codes can ensure a truly interference-free operation. Two important facts will be revealed by the analysis given in this paper. First, implementation of an interference-free CDMA will never be possible unless using complementary code sets, such as the OC code sets. In other words, all traditional spreading codes working on an one-code-per-user basis are not useful for implementation of an MAI-free and MI-free CDMA system. Second, to enable the interference-free CDMA operation, the flock size of the OC codes should be made equal to the set size of the codes, implying that a OC code set can support as many users as the flock size of the code set. A systematic search has been carried out to generate the super-set of various OC codes with the help of carefully selected seed codes belonging to distinct sub-sets. This paper will also propose an implementation scheme based on multi-carrier CDMA architecture and its performance is compared by simulations with the ones using traditional spreading codes.

Published
2006

226. Orthogonal Decision-Feedback Detector for Asynchronous Multiuser CDMA Systems

Author

Chen, Hsiao-Hwa and Sim, Hak-Keong

Subjects
Electrical engineering -- Research, Communications equipment -- Research, Decision theory -- Usage
Abstract

This paper introduces asynchronous orthogonal decision-feedback detector (AODFD) for asynchronous CDMA multiuser detection. The AODFD based on entire message-length detection is studied first. A realizable scheme, sliding-window AODFD, is then proposed and its performance is analyzed. In spite of its simple structure, the sliding-window AODFD can perform as desirably as ADDFD, which has a much higher complexity. The reduced complexity of the sliding-window AODFD is due to the use of orthogonal matched-filtering and a short window size. Different from ADDFD that requires computational intensive z-transformed matrix inversion and spectral factorization, AODFD uses agile Gram-Schmidt procedure. It is possible for AODFD to adopt a simple updating algorithm and parameter updating is no longer always necessary when users leave the system. The comparisons are also made with other orthogonal-based detectors and the bit error probability results show that the AODFD is an attractive multiuser detector. Index Terms--CDMA, multiuser detection, decision feedback.

Published
2001

227. Zero-Insertion Adaptive Minimum Mean-Square Error (MMSE) Receiver for Asynchronous CDMA Multiuser Detection

Author

Chen, Hsiao-Hwa and Liu, Zhi-Qiang

Subjects
Multichannel communication -- Research, Asynchronous communications -- Research, Detector circuits (Telecommunications) -- Research, Business, Electronics, Electronics and electrical industries, Transportation industry
Abstract

This paper proposes an asynchronous code-division multiple-access multiuser detector, zero-insertion adaptive minimum mean-square error (ZA-MMSE) multiuser detector, in which a data stream is partitioned into blocks by inserted zero bits and detection proceeds block by block to ensure a balance between processing delay and detection efficiency. The bit error rate performance of the ZA-MMSE detector is evaluated under different multipath scenarios with varying severity characterized by average relative strength of the paths. The results are compared with decorrelator, revealing that the ZA-MMSE detector offers promising detection efficiency at a relatively low complexity, which is linear to the product of the number of users and block length. As an-effort to implement it adaptively, the transient behavior of the ZA-MMSE detector with different recursive algorithms is studied. It is concluded that the least mean square algorithm is not suitable due to its power-dependent convergence; whereas the recursive least square algorithm offers a consistently fast convergence regardless of the received power, making it ideal for application in a time-varying channel with near--far effect. Index Terms--Code-division multiple access (CDMA), minimum mean-square error (MMSE), multiuser detection, spread spectrum.

Published
2001

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