Browsing by Author "Wu, Wei-De"

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On Parameter Estimation for Ultra-Wideband Channels with Clustering Phenomenon
(2008)
Wu, Wei-De
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Wang, Chung-Hsuan
;
Chao, Chi-chao
;
Witrisal, Klaus
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電信工程研究所
One of the unique characteristics of ultra-wideband channels is the clustering phenomenon resolved by the ultra-wide signal bandwidth. Channel structures extended from the Saleh-Valenzuela model, e. g., the IEEE 802.15.3a and IEEE 802.15.4a models, have been proposed to describe such phenomenon. It is, however, noticed that a clear and systematic procedure to estimate the model parameters is still missing. Based on the recently developed analytical results, a new estimation approach is proposed in the paper to resolve the inconvenience and ambiguity in previous methods. The key step is to match the statistical profiles of interests by formulating an optimization problem with an explicit analytical objective function that can be systematically solved. Numerical tests have also been conducted to demonstrate the effectiveness of the proposed method.
Signal-to-Interference-Plus-Noise Ratio Analysis for Direct-Sequence Ultra-Wideband Systems in Generalized Saleh-Valenzuela Channels
(2007-10-01)
Wu, Wei-De
;
Lee, Cheng-Chia
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Wang, Chung-Hsuan
;
Chao, Chi-chao
;
電信工程研究所
In this paper, exact signal-to-interference-plus-noise ratio (SINR) analysis of direct-sequence ultra-wideband (UWB) systems with Rake receiving in the presence of inter-symbol interference and multiple-access interference over a generalized Saleh-Valenzuela (GSV) channel with a generic pulse shaping function is provided. The SINR expression, for synchronized multiple-access, is first obtained without assuming random spreading. The GSV channel structure under consideration is a generalization of the Saleh-Valenzuela channel structure with generalized path-gain and path-arrival models, examples of which can include all the IEEE 802.15.3a UWB channel models and some of the IEEE 802.15.4a models. Then, by the novel treatment of renewal processes, the exact average SINR over the GSV channel statistics is obtained. Our analytical results well match computer simulations and can readily be applied to evaluate and improve the performance of UWB systems over realistic channel and interference models.
UWB communications with under-sampled receivers
(2006)
Wu, Wei-De
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Wang, Chung-Hsuan
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Chiu, Mao-Ching
;
Chao, Chi-Chao
;
電子工程學系及電子研究所
In this paper, we investigate a novel coding idea proposed previously to enable under-sampled receivers. An under-sampled receiver can sample the received baseband signals at only a fraction of the Nyquist rate and turns out to be an effective solution to the bottleneck of high-rate sampling and processing in ultra-wideband (UWB) communications. The spectrum aliasing problem can be solved by an analogy between an under-sampled system and a multiple-antenna one. However, underlying differences between the two systems exist and motivate the study of the fundamental limits of a coded under-sampled system. The study is carried out by characterizing the optimal coding structures with and without channel state information at transmitter (CSIT). A practical selective coding structure is also developed to provide satisfactory performance with reduced CSIT requirement. Finally, simulations are conducted to verify the theoretical characterization. Our results indicate that an under-sampled UWB system can benefit from power-saving, cost reduction, and full multipath diversity at the expanse of little or confined performance degradation.