Browsing by Author "Tarng, JH"

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A new and efficient hybrid model for estimating space diversity in indoor environment
(2000-03-01)
Tarng, JH
;
Chang, RS
;
Huang, JM
;
Tu, YM
;
電信工程研究所
This study presents a novel hybrid model based on a two-dimensional (2-D) site-specific model and a statistical model to investigate space diversity in indoor environments. The statistical model describes the field scattered by rough surface boundaries and randomly positioned scatterers, which may be important when one or both of the receiving and transmitting antennas are close to the boundaries of the scatterers. Comparing the computed spatial correlation with the measured one with the transmitting frequency at 2.44 GHz at many different sites demonstrates the effectiveness of the hybrid model. In addition to accurately predicting field strength, the hybrid model can quantify the relative mean contribution of diffused scattering in an indoor environment with a factor r. The factor is equal to the ratio of ensemble average of a randomly scattered envelope to the spatially averaged envelope. Its optimum value is in a narrow range from 0.3 to 0.5 when the intensity fluctuation at the measurement sites is in or close to saturation regions, where a large number of micromultipaths are generated. This finding confirms the relative ease in applying the hybrid model. Experimental results suggest that choosing r = 0.4 in a saturation allows the hybrid model to yield a satisfactory performance, as confirmed by a blind test. Moreover, good diversity gains can be obtained with an antenna spacing greater than or equal to one wavelength. Our results further demonstrate that the diversity gain of horizontally spaced antennas exceeds that of vertically spaced antennas.
A novel 3-D scattering model of 1.8-GHz radio propagation in microcellular urban environment
(1999-05-01)
Tarng, JH
;
Ju, KM
;
電信工程研究所
;
Institute of Communications Engineering
This work presents a novel three-dimensional (3-D) scattering model to predict the path loss of a microcellular radio channel in an urban environment. The analytical scattering model combined with a patched-wall model predicts the median path loss more accurately than the conventional analytical ray-tracing model in the cases studied, Comparing the path loss with the measured one at 1.8 GHz demonstrates the effectiveness of the scattering model. The scattering model includes three major propagation modes: 1) a direct-path wave; 2) a ground-reflected wave; and 3) the scattered field from the walls aligned along a street. The proposed model with a polarization scattering matrix associated with the patched-wall model aptly describes the third mode, which is usually neglected or oversimplified.
A novel and efficient hybrid model of radio multipath-fading channels in indoor environments
(2003-03-01)
Tarng, JH
;
Liu, WS
;
Huang, YF
;
Huang, JM
;
電信工程研究所
This paper presents a novel and efficient hybrid model combining a two-dimensional (2-D) site-specific model and a statistical model to characterize multipath fading in indoor environments. The site-specific, model describes the propagation effects of interior walls and building walls. The latter model characterizes the effect of scattering due to rough surface boundaries and/or randomly positioned scatterers such as furniture and personnel, which significantly affects small-scale fading. The hybrid model is computationally efficient since only the 2-D site-specific model is needed. In addition to Accurately predicting mean field strength, the model can effectively quantify the relative mean contribution of diffused scattering with a factor r. The factor is also an effective index to quantify the cluttering strength of the propagation environment: 1) light-cluttering situation r less than or equal to 0.35 and 2) heavy-cluttering situation r greater than or equal to 0.65. Some blind tests validate the effectiveness of the model. A large amount of experimental data for 2.44-GHz radio at many different sites shows that a Nakagami distribution describes the fading distribution well.
A novel concept for finding proper orthogonal wavelets effectively to solve a large object scattering problem
(2003-04-18)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
友訊交大聯合研發中心
[1] A novel concept of "visible energy" is proposed, and its magnitude is shown to be valuable information for determining whether the chosen orthogonal wavelet is proper in solving a large object scattering problem. With the properly chosen wavelets for the targeting problem the ( transformed) wavelet-domain impedance matrix can be sparsified effectively for solving electromagnetic integral problems. Visible energy is defined as the energy of all dilations of a single mother wavelet for an arbitrary translation in the spectral domain over the entire "visible region." It is found that for large matrix sizes, using wavelets with smaller visible energy will lead to a greater sparsification of the matrix. Numerical examples considering various scatterers with different shapes such as a circular cylinder, an L-shaped scatterer, and a duct show the validity of our findings.
A novel TOA estimation method of broadband signal propagation in outdoor environment
(2004)
Chang, WJ
;
Tarng, JH
;
電信工程研究所
;
Institute of Communications Engineering
In high-speed wireless data transmission, severe frequency-selective fading of multipath channel causes inter-symbol interference (ISI) and leads to a significant problem of the systems. To ease the problem, precise modeling of the multipath time-of-arrival (TOA) is important and needed. In this paper, a novel method based on Turin's A-K model is proposed to estimate TOA of a broadband signal through the measured result of a narrow band signal in outdoor environments. Our method have been validated by the measurement result of 1.95 GHz and 2.44 GHz radio propagation in metropolitan and suburban areas. TOA of a 120MHz bandwidth signal can be effectively predicted by using our method with the measured results of a 15MHz bandwidth signal.
A preliminary report on the Phase-I ATSC field test results in Taiwan
(2000)
Tsai, JF
;
Lin, CC
;
Hang, HM
;
Tarng, JH
;
Yu, HC
In May 1998, Taiwan formally adopted the ATSC Digital Television (DTV) as its local digital terrestrial broadcasting standard. In order to define the DTV service area and specify the transmission parameters, we like to know the characteristics of the DTV signal over the local irregular terrain, the impact of interference, and the relationship between the signal power and video quality. me measured the DTV signal and compared the DTV and the NTSC service availability. We selected 100 test sites in Taipei city and its vicinity including three types of environment: urban, suburban and rural areas. In general, the DTV system has a clear advantage over the NTSC system in reception quality.
A study of alternative broadcasting technologies for the extension of DTV coverage in Taiwan
(2000-12-01)
Yu, HC
;
Tarng, JH
;
Hang, HM
;
Lee, ZY
;
電子工程學系及電子研究所
In Taiwan. there are six major NTSC terrestrial broadcasting stations and 129 relay stations, which cover about 98% of Taiwan's population. This paper addresses the planning of DTV broadcasting in Taiwan. DTV signals will be broadcast from the same six major transmitting sites and are expected to provide similar coverage. To extend DTV coverage beyond the major transmitting sites, only the existing 9 NTSC relay stations with over 100W transmitting power would relay DTV signals. Residences living beyond the above coverage areas could rely on CATV or DTH to receive terrestrial DTV programs.
Acoustic pulse propagation in a fluctuating ocean with range-dependent sound-speed profile
(1996-04-01)
Chang, WR
;
Tarng, JH
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
When an acoustic pulse propagates in a randomly fluctuating ocean with a deterministic sound-speed profile, it is distorted since every frequency component experiences different extents of scattering from the random inhomogeneity and echo numbers. Here, the split-step method is used to simulate an acoustic pulse with a 3-kHz carrier propagating through a turbulent ocean with range-independent/-dependent sound-speed profiles. It is found that (1) the ocean is a frequency-selective fading channel; (2) the received pulse profile is dependent on the received depth, sound-speed distribution, fluctuation strength, and scale length of turbulence in oceans; (3) the rms pulsewidth is broadened by several times its initial value as a consequence of pulse echoes and pulse wandering of every pulse realization of the ensemble; (4) the rms pulsewidth is increased when the fluctuation strength increases or the scale length decreases; and (5) the statistical properties of the propagating pulse are similar for both the range-independent and -dependent cases in the mean square sense. (C) 1996 Acoustical Society of America.
Acoustic pulse propagation in a range-dependent turbulent ocean
(1995)
Tarng, JH
;
Chang, WR
;
電信工程研究所
;
Institute of Communications Engineering
An effective three-dimensional model for UHF radio propagation into multistory office buildings
(1999-01-20)
Tarng, JH
;
Chang, YC
;
Chen, CM
;
電信工程研究所
;
Institute of Communications Engineering
An effective three-dimensional (3-D) direct-transmitted model combined with a patched-wall model is proposed to explore UHF radio propagation into multistory buildings in a microcellular environment. The model is verified by comparing the computed path loss with the measured one of 1.7 and 2.44 GHz radio waves propagating at different sites. The comparison demonstrates that the model has reasonably accurate prediction when the number of floor levels between the transmitting and the receiving antennas is no more than four.
Analysis of ATSC field test results in Taiwan
(2002-03-01)
Lin, CC
;
Chen, CM
;
Tarng, JH
;
Hang, HM
;
Yu, HC
Field tests of the transmission performance of the ATSC DTV system have been conducted in Taiwan. The test results as well as comparisons against the NTSC system performance are reported and analyzed. From the measured results the reception characteristics of the DTV can be deduced and can provide guidelines for television stations to design transmission system, schedule equipment deployment, plan service coverage areas, and improve the reception quality of the digital signal.
Application of mix-phase wavelets to sparsify impedance matrices
(1999-10-01)
Huang, JM
;
Leou, JL
;
Jeng, SK
;
Tarng, JH
;
電信工程研究所
Effective wavelets to solve electromagnetic integral equations are proposed. It is based on the same construction procedure as Daubechies wavelets but with mix-phase to obtain maximum sparsity of moment matrix. These new wavelets are proved to have excellent performance in non-zero elements reduction in comparison with minimum-phase wavelet transform (WT). If further sparsity is concerned, wavelet packet (WP) transform can be applied but increases the computational complexity. In some eases, the capability of non-zero elements reduction by this nsw wavelets even better than WP with minimum-phase wavelets and with less computational efforts. Numerical experiments demonstrate the validity and effectiveness of the neu; wavelets.
Effect of radio bandwidth on multipath clustering
(2003)
Chang, WJ
;
Tarng, JH
;
電信工程研究所
;
Institute of Communications Engineering
Detail knowledge of time dispersion characteristics of radio multipath propagation channel is essential for successful design of Ultra-Wideband (UWB) systems. The multipath-clustering phenomenon, which is caused by the fact that scatterers tend to group together, may become one of the dominant factors affecting the delay spread especially in the long delay situation. In this paper, a method based on Turin's A-K model is proposed to investigate and estimate the effect of radio bandwidth on the multipath clustering. It is found that the signal of larger bandwidth will observe stronger multipath clustering phenomenon because more paths can be resolved due to a finer time resolution. Our finding has been validated by the measurement result of 1.95 GHz radio propagation in metropolitan and suburban areas. It is also proposed that the A-K process of a wider-bandwidth signal can determine that of a narrower-bandwidth signal.
Effective models in evaluating radio coverage on single floors of multifloor buildings
(1999-05-01)
Tarng, JH
;
Liu, TR
;
電信工程研究所
;
Institute of Communications Engineering
An effective site-specific hybrid model is developed to predict the path loss and the effective radio coverage on single floors, The hybrid model, combined with a two-dimensional (2-D) model and an easy-to-use direct-transmitted ray (DTR) model, is incorporated with the building blueprint in usage, Both effects of the interior walls and the metallic objects such as whiteboards, bookcases, and standing air conditioners on radio propagation are considered. It is found that inclusion of metallic objects will enhance the performance of the model.
Electromagnetic absorption in human brains by using fast wavelet transform methods
(2001)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
Institute of Communications Engineering
An application of fast wavelet transform methods including discrete wavelet transform (DWT) and discrete wavelet packet (DWP) methods to the electromagnetic absorption in the human brains is presented. The total induced electric field inside the brain determined from the tensor integral-equation (TIE) is solved by the method of moments (MoM), DWT and DWP, respectively. It is found that using the wavelet transform methods especially using the DWP method in the targeted problems will lead to very sparsely moment matrices and relatively reduced computational complexities and memory requirements. Numerical examples are given to show the validity and effectiveness of the method.
Finding proper orthogonal wavelets to solve electromagnetic scattering problems
(2001)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
Institute of Communications Engineering
A novel concept of "visible energy" is proposed and its magnitude is valuable information for determining whether the chosen orthogonal wavelet is proper in solving a electromagnetic scattering problem. With the properly chosen wavelets for the targeting problem, the (transformed) wavelet-domain impedance matrix can be sparsified effectively for solving electromagnetic integral problems. It is found that for the large matrix size using the wavelets with smaller visible energy will lead to a greater sparsification of the matrix. A simple scattering problem of circular cylinder is considered to show the validity of our findings.
Impedance matrix compression using an effective quadrature filter
(2000-08-01)
Huang, JM
;
Leou, JL
;
Jeng, SK
;
Tarng, JH
;
電信工程研究所
An effective quadrature mirror filter (QMF) proposed by Vaidyanathan has been used to solve 2D scattering problems. QMF has been popular for some time in digital signal processing, under the names of multirate sampling, wavelets, etc. In this work, the impulse response coefficients of QMF were used to construct the wavelet transform matrix. Using the matrix to transform the impedance matrices of 2D scatterers produces highly sparse moment matrices that can be solved efficiently. Such a presentation provides better sparsity than the celebrated and widely used Daubechies wavelets. These QMF coefficients are dependent on the filter parameters such as transition bandwidth and filter length. It was found that the sharper the transition bandwidth, the greater the reduction in nonzero elements of the impedance matrix. It also can be applied in the wavelet packet algorithm to further sparsify the impedance matrix. Numerical examples are given to demonstrate the effectiveness and validity of our finding.
Measurements and modeling of radio propagation in large offices with low metallic partitions
(1996-06-20)
Ju, KM
;
Tarng, JH
;
電信工程研究所
;
Institute of Communications Engineering
A theoretical model is developed to predict the propagation loss of UHF radio waves in large modem offices with low metallic partitions. It is found that in addition to free-space propagation loss the shadowing loss due to the blockage by the low partitions in the out-of-sight situation becomes the dominant one. The shadowing loss can be efficiently formulated by using the theory of single or double knife-edge diffraction. The model has been verified by an experiment conducted at 905 MHz, 1.75 GHz, and 2.44 GHz in large offices. The model shows reasonable accuracy. (C) 1996 John Wiley & Sons, Inc.
Measurements and modeling of radio propagation in large offices with low metallic partitions
(1996-06-20)
Ju, KM
;
Tarng, JH
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
A theoretical model is developed to predict the propagation loss of UHF radio waves in large modem offices with low metallic partitions. It is found that in addition to free-space propagation loss the shadowing loss due to the blockage by the low partitions in the out-of-sight situation becomes the dominant one. The shadowing loss can be efficiently formulated by using the theory of single or double knife-edge diffraction. The model has been verified by an experiment conducted at 905 MHz, 1.75 GHz, and 2.44 GHz in large offices. The model shows reasonable accuracy. (C) 1996 John Wiley & Sons, Inc.
Modeling and measurement of 2.44-GHz radio out-of-sight propagation on single floors
(1997-01-01)
Liu, TR
;
Tarng, JH
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
An easy-to-use DTR model combined with a patched-wall model is proposed to predict the path loss for out-of-sight propagation on a single floor through interior walls. The model demonstrates an accurate prediction, and is verified by comparison of the predicted path loss with the measured one of 2.44-GHz radio propagation at four different sites. (C) 1997 John Wiley & Sons, Inc.