Khoa N. Le

On Angle-of-Arrival and Time-of-Arrival Statistics of Geometric Scattering Channels

This paper proposes a hyperbolic distribution to model the distribution of random scatterers between a base station (BS) and the user equipment (UE) in multipath mobile environments. New hyperbolic angle-of-arrival (AoA) probability density function (pdf), power azimuth spectrum (PAS), time-of-arrival (ToA) pdf, and power delay spectrum (PDS) are derived. The effectiveness of Gaussian, Janaswamy, and hyperbolic scatterer distributions is assessed by estimating their fitting errors to a given empirical data set. New 3-D simulation results on the Gaussian and hyperbolic PAS and PDS are given and discussed. The line-of-sight (LoS) distance D (in kilometers) between the BS and the UE and the propagation path distance mu (in kilometers) can be related mathematically.

On mathematical derivations of auto-term functions and signal-to-noise ratios of the Choi--Williams, first- and nth-order hyperbolic kernels

This paper continues investigations on the hyperbolic kernel family [K.N. Le et al., Opt. Eng. 42 (8) (2003) 2400-2415] by giving further mathematical insight into auto-term and noise robustness properties of the first-order hyperbolic, Choi-Williams (CW) and nth-order hyperbolic kernels, for which explicit expressions are derived and approximated for useful values of kernel control parameters @b, @s and kernel order n. Simulation results are also given to support the mathematical approximations.

A mathematical approach to edge detection in hyperbolic-distributed and Gaussian-distributed pixel-intensity images using hyperbolic and Gaussian masks

This paper mathematically introduces a new hyperbolic distribution and hyperbolic mask for edge detection. Mathematical comparisons between the hyperbolic and Gaussian (Mexican-hat) masks in the time and frequency domain are given for typical scale parameters of @b=1 and @s=2 respectively. Edge-detection error probability as a function of the half mask size m is estimated using both masks in Gaussian- and hyperbolic-distributed pixel-intensity images. Advantages and disadvantages of the masks and both distributions are discussed. Experiments on edge detection in images are presented. The effects of noise are also considered.

Bounds on Inter-carrier Interference Power of OFDM in a Gaussian Scattering Channel

This letter derives the upper and lower bounds on inter-carrier interference power PICI of Orthogonal Frequency Division Multiplexing (OFDM) in a Gaussian scattering channel. The bounds are computed as functions of fdTs product of the maximum Doppler spread fd and symbol duration Ts, ζ frequency tracking and ϵ mobile travelling direction. Insightful discussions on the characteristics of PICI are given. Future work is also outlined.

A new formula for the angle-of-arrival probability density function in mobile environment

This paper theoretically derives an angle-of-arrival (AoA) probability density function in multi-path mobile environment where the scatterer distribution obeys a hyperbolic sech function. Using simulations, comparisons are made between the Gaussian distribution and the hyperbolic sech distribution for different distance from the base station (BS), user equipment (UE) and UEs effective radius.

Hyperbolic wavelet family

This article reports early results on digital implementation of first- and nth-order hyperbolic wavelets whose important parameters are explicitly expressed and numerically estimated. The first-order hyperbolic, Morlet and Choi–Williams wavelets are compared in detail by numerically calculating their band-peak frequencies, minimum numbers of sampling points, scale resolutions, and maximum numbers of scales. One of the main aims is to show that there exists a strong link among time–frequency kernels and wavelets. This relationship helps to expand and link time–frequency and wavelet approaches to signal analysis. One example of using the hyperbolic wavelet for speech recognition is also given.

Hyperbolic kernel for time-frequency power spectrum

We propose a new family of hyperbolic kernels F hyperbolic(u,t)5@sech(but)# n , where n51,3,5,..., for a joint time- frequency distribution. The first-order hyperbolic kernel sech(but )i s mainly considered. Theoretical aspects of the new hyperbolic kernel are examined in detail. The effectiveness of a kernel is determined by three factors: cross-term suppression, auto-term resolution, and noise robust- ness. The effectiveness of the new kernel is compared with other kernels including Choi-Williams, Wigner-Ville, and multiform tiltable exponential using two different signals: complex-exponential and chirp.

Signal detection using time-frequency distributions with nonunity kernels

A new technique is proposed to solve the simple binary signal-detection problem using a nonunity kernel time-frequency signal detector (GNKD). The GNKD is based on a Cohen time-frequency power spectrum, employing nonunity kernels only. This class of signal detectors includes the Choi-Williams detector (CWWD) and the recently proposed hyperbolic detector (HyD). This work extends the work done by Kumar and Carroll, who investigated the cross unity-kernel Wigner-Ville detector (CWD), which is a special case of the GNKD class. The discrete Moyals formula for the nonunity kernel time-frequency distribution is derived. The performance of the GNKD is then compared to that of the CWD and the cross-correlator (CORR) detectors by calculating the signal-to-noise ratio (SNR) and the loss factor Q. The GNKD is shown to be better than both the CWD and the CORR with improvement in the SNR by a factor of &. The HyD can improve the SNR by about 18% compared to the CWWD. Detection of some practical nonstationary signals is also inves- tigated to exemplify the proposed method.

A survey on effective assessment methods to enhance student learning

Summary The effectiveness of eight different assessment methods – (1) seminar, (2) closed-book mid semester test, (3) open-book mid-semester test, (4) problem-based assignment, (5) presentation, (6) multiple choice question test, (7) closed-book final examination, and (8) open-book final examination – is studied in this paper. A detailed survey is conducted to thoroughly understand student needs, and the significance of assessment items and methods. Individual interviews are conducted to gather further information and clarification on the survey. Relative important index (RII) values and F-tests of all categories and groups are estimated. Recommendations are given to improve the effectiveness of various assessment methods.

On generic skill development: An engineering perspective

This paper addresses ten generic skills set out by Engineers Australia from the engineering graduate perspective. Generic skills of electronic-engineering and civil-engineering graduates are studied prior to graduation and after graduation. Detailed comparisons are made. Possible recommendations are also discussed.