Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
There is a significant number of visually impaired individuals who suffer sensitivity loss to high spatial\r\nfrequencies, for whom current optical devices are limited in degree of visual aid and practical application.\r\nDigital image and video processing offers a variety of effective visual enhancement methods that can be\r\nutilised to obtain a practical augmented vision head-mounted display device. The high spatial frequencies of\r\nan image can be extracted by edge detection techniques and overlaid on top of the original image to improve\r\nvisual perception among the visually impaired. Augmented visual aid devices require highly user-customisable\r\nalgorithm designs for subjective configuration per task, where current digital image processing visual aids\r\noffer very little user-configurable options. This paper presents a highly user-reconfigurable morphological\r\nedge enhancement system on field-programmable gate array, where the morphological, internal and external\r\nedge gradients can be selected from the presented architecture with specified edge thickness and magnitude. In\r\naddition, the morphology architecture supports reconfigurable shape structuring elements and configurable\r\nmorphological operations. The proposed morphology-based visual enhancement system introduces a high\r\ndegree of user flexibility in addition to meeting real-time constraints capable of obtaining 93 fps for high-definition\r\nimage resolution....
In this paper, the probability density function (PDF) estimation is introduced in the framework of estimating the\r\nNakagami fading parameter. This approach provides an analytic procedure for finding the fading parameter. Using the\r\ncopula theory, an accurate PDF estimate is obtained even when the desired signal is corrupted in a noisy\r\nenvironment. In the real world, the noise samples could be highly dependent on the main signal. Copula-based\r\nmodels are a general set of statistical models defined for any multivariate random variable. Thus, they depict the\r\nstatistical behavior of a received signal including two dependent terms, representative of the desired signal and noise.\r\nPrevious works in the Nakagami parameter determination have mainly examined estimation based on either a\r\nnoiseless sample model or an independent trivial noisy one. In this paper, we consider a more comprehensive\r\nsituation about the noise destruction and our investigation is done in low signal-to-noise ratios. The parametric\r\nbootstrap method approves the accuracy of the analytically estimated PDF, and simulation results show that the new\r\nestimator has superior performance over conventional estimators....
This article presents an iterative minimum mean square error- (MMSE-) based method for the joint estimation of\r\nsignal-to-noise ratio (SNR) and frequency-selective channel in an orthogonal frequency division multiplexing (OFDM)\r\ncontext. We estimate the SNR thanks to the MMSE criterion and the channel frequency response by means of the\r\nlinear MMSE (LMMSE). As each estimation requires the other one to be performed, the proposed algorithm is iterative.\r\nIn this article, a realistic case is considered; i.e., the channel covariance matrix used in LMMSE is supposed to be totally\r\nunknown at the receiver and must be estimated. We will theoretically prove that the algorithm converges for a\r\nrelevantly chosen initialization value. Furthermore simulations show that the algorithm quickly converges to a solution\r\nthat is close to the one in which the covariance matrix is perfectly known. Compared to existing SNR estimation\r\nmethods, the algorithmimproves the trade-off between the number of required pilots and the SNR estimation quality....
Object localization using active sensor network exploiting the scattering of the emitted waves by a transmitter has\r\nbeen drawing a lot of research interest in the last years. For most applications, the environment leads to the arrival of\r\nmultiple signals corresponding to emitted signal, signals which are scattered by the objects, and noise. In practical\r\nsystems, the signals impinging on an array are frequently correlated, and the object number rapidly exceeds the\r\nnumber of sensors, making unsuitable most high-resolution methods used in array processing. We propose a solution\r\nto overcome these two experimental constraints. Firstly, frequential smoothing is used to decorrelate the scattered\r\nsignals, enabling the estimation of their time delays of arrival (TDOA), using subspace-based methods. Secondly, an\r\nefficient algorithm for source localization using the TDOA is proposed. The advantage of the developed method is its\r\nefficiency even if the number of sources is larger than the number of sensors, in the presence of correlated signals.\r\nThe performances of the proposed method are assessed on simulated signals. The results on real-world data are also\r\npresented and analyzed....
In a switching problem, a one-to-one mapping from the inputs to the outputs is conducted according to a switch\r\npattern, i.e., a permutation matrix. In this paper, we investigate a wireless switching problem, in which a group of\r\nsingle-antenna relays acts together as a multiple-input-multiple-output (MIMO) switch to carry out distributed\r\nprecode-and-forward. All users transmit simultaneously to the MIMO switch in the uplink and then the MIMO switch\r\nprecodes the received signals and broadcasts in the downlink. Ideally, each user could receive its desired signal from\r\none other user with no or little interference from other users. Self-interference is allowed in the received signals, as it\r\ncan be canceled when each user has the channel gain of its self-interference. We propose two distributed relaying\r\nschemes based on two widely adopted criteria, i.e., zero-forcing relaying and minimum mean square error (MMSE)\r\nrelaying. For the distributed zero-forcing relaying, we further propose a message passing approach, with which the\r\nproposed zero-forcing relaying achieves significant throughput gain with little attendant overhead. We also claim that\r\nthe proposed MMSE relaying achieves even larger throughput at the expense of larger amount of message passing.\r\nSimulation results validate the throughput gains of the proposed relaying schemes....
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