Browsing by Author "Jeng, LD"

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Antijam capability analysis of RS-coded slow frequency-hopped systems
(2000-02-01)
Su, YT
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Jeng, LD
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電信工程研究所
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Institute of Communications Engineering
The application of Reed-Solomon codes in slow frequency-hopped systems has been extensively studied. Earlier investigations assumed an infinite interleaving length and considered partial-band noise jammers only. This paper extends previous efforts by analyzing the effect of finite interleaving length and the impact of band multitone jammers, We also explain why two-threshold (2T) erasure-insertion methods (EIM) are needed and examine their performance, Numerical results are presented to compare the effectiveness of EIM's and jammer types and to stud!, the relationships among the hop rate, the interleaver size, and the code rate, The use of 2T EIM's necessitates the estimation of several additional channel and signal parameters, Simple and effective estimation algorithms are provided as well.
Cochannel interference rejection in multipath channels
(1997-12-01)
Su, YT
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Jeng, LD
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Ueng, FB
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電信工程研究所
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Institute of Communications Engineering
In addition to additive thermal noise, a received direct-sequence spread spectrum (DS/SS) signal may suffer from intersymbol interference (ISI) and interference caused by cochannel narrowband users or other narrowband radio frequency interference (RFI). This paper presents a workable solution for removing narrowband interference (NBI) and reducing ISI or inter-chip interference (ICI) when the communication channel can be modeled as an FIR filter and the NBI comes from multiple CW tones, an AR-modeled Gaussian process, or a BPSK signal. Unlike earlier solutions, the proposed scheme is capable of performing the functions of NBI-rejection, ISI/ICI suppression and data detection (code despreading) simultaneously. It is easy to implement and, more importantly, it yields lower bit error rate (BER) and smaller mean squared error (MSE).
Performance of turbo codes in multipath fading channels
(1998)
Jeng, LD
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Su, YT
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Chiang, JT
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電信工程研究所
;
Institute of Communications Engineering
This paper presents performances of turbo codes in fading multipath channels. We apply two channel estimation techniques, namely, the pilot tone technique and the pilot symbol assisted modulation technique to obtain channel side information for decoding. Various channel models are used in computer simulations. Numerical results are given to quanti,fy various system behavior and to provide numerical examples that provide us system solutions.