Multiband orthogonal frequency division multiplexing (MB-OFDM) is an efficient approach for ultra-wideband (UWB) wireless communication applications. One major difficulty of MB-OFDM UWB signal is its large peak-to-average power Ratio (PAPR). The high PAPR limits its capacity due to the distortion caused by the nonlinear characteristics of both the analog-to-digital converter (ADC) and high-power amplifier (HPA). Hence, it is necessary to reduce the PAPR of MB-OFDM UWB signals. Several techniques have been reported in the literature for PAPR reduction in OFDM. These techniques can also be extended for PAPR reduction in MB-OFDM UWB signals. However, comparative performance evaluation of these techniques for PAPR reduction in MB-OFDM UWB signals is lacking in the literature. Hence, in this paper, four techniques, namely, filtering after clipping, turbo coding of clipped signals, tunable predistorter, and active constellation extension are extended for PAPR reduction of MB-OFDM UWB signals and their performance is evaluated and compared through computer simulations. In this evaluation, the bit-error rate (BER) is used as the performance measure.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

This is a preliminary study and the objective of this study has been to compare the performance of some of the ­primitive and fundamentally different post acquisition image enhancement algorithms as applied to ultrasound (US) liver images. Such a comparison would help to decide as to which algorithm could be useful for clinicians, and in evaluating the role of US liver image enhancement in a soft-copy environment. In this study, 10 US liver images were taken, and 5 fundamentally different and widely employed image enhancement techniques were applied on these images. As the principal objective of image enhancement is to obtain an image with a high content of visual detail, a multipoint rank-order method was used to identify small differences or trends in observations. Among the ­different algorithms, the morphological filtering outperformed other techniques. The images with diffused liver diseases had a preference of 76% and the images with cystic masses had a preference of 67%. Wavelet-based filtering closely ­followed this with 63% of preference in respect of images with a diffused liver disease and 57% of preference in ­respect of images with cystic masses.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

A new vertical handoff decision algorithm is proposed to minimize the cost of the grade of service (GoS) in ­heterogeneous wireless networks, which comprise cellular networks and wireless local area networks (WLANs). We first calculate the block probability and the drop probability, which are factors of the GoS and function of new call arrival rate, handoff call arrival rate and radius of WLANs, cellular network and WLANs under the channel-guard call admission strategy. Then we propose a cost function of the GoS, and obtain the optimal radius of WLANs by using simulated annealing (SA) method to minimize the cost. All the nodes should handoff from cellular network to WLAN if they enter WLAN's scope and handoff from WLAN to cellular network if they leave the scope. Finally, we analyze our handoff algorithm and compare it with other algorithm, and the results show that our algorithm could achieve good effects.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

Wireless sensor networks (WSNs) consist of networked sensor nodes, deployed to sense a phenomenon and report it to a base station. Sensor nodes are small and usually equipped with small batteries with limited capacity, and therefore, one of the most important design considerations for WSNs is power consumption. WSNs expend energy for communications, data processing and sensing; for commonly used RF communications this task accounts for the largest portion of power expended. Hybrid radio frequency/free space optical (RF/FSO) communications has been proposed to reduce power consumption by the sensor node, and in this paper, the performance of the RF/FSO WSN is compared against an RF-only WSN in terms of network lifetime and coverage. Results show that for the wide range of scenarios considered, the RF/FSO WSN lasts at least twice as long as its RF-only counterpart, despite providing the same level of network coverage. This paper also investigates network parameter selection for optimum RF/FSO network coverage.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

Most methods for the FIR differentiator design, published so far, have rather complex algorithms, requiring significant computing time. In addition, their design procedures and equations differ for the cases of even and odd differentiator length. FIR differentiators (filters) designed by these methods mostly have the passband group delay level corresponding to that of the linear phase FIR filters. In that sense, the design procedure of the first and higher order FIR full-band differentiators, proposed in this paper, is not only more efficient, but general too. Its efficiency consists in the direct (by this means - faster) determination of numerical values of their impulse response coefficients. Its generality consists in the fact that this method uses the same procedure and formulas for the design of differentiators with both even and odd length (without any mutual difference). (In order to avoid confusion, in the following text, the order of differentiation will be denoted by k, while the length of the FIR structure will be denoted by N). In ­addition, FIR differentiators designed by this method have approximately constant passband group delay level, which is lower than that of the corresponding linear phase FIR differentiators. These characteristics are enabled due to the fact that full-band differentiators, designed by the presented method, possess neither the (anti)symmetric feature of their impulse response coefficients, nor the strictly linear phase. The proposed method is based on the simultaneous approximation of the prescribed magnitude and group delay responses. The method presents an approach for the FIR differentiator frequency response approximation, directly in the complex, and not in the real domain. Two weighting coefficients, α_R and α_I , for the approximation of the real and imaginary part of the frequency response, respectively, are introduced. In the convenient manner, they are incorporated into properly and specifically defined quadratic measure ­error of the FIR differentiator's frequency response approximation. This manner enables adjusting (decreasing) contributions of the frequency response real and imaginary part approximation errors to the total approximation error. Performing a proper analysis of the real and imaginary part approximation errors (of designed FIR differentiator ­frequency responses), values of these two parameters, giving a small variation of the group delay response, are ­obtained simultaneously with very small magnitude response error in the passband. In order to illustrate the ­proposed method effectiveness, numerical design examples of the second order FIR full-band differentiators are given.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

Target motion analysis (TMA) using conventional passive bearing together with frequency measurements is explored. This approach offers one tactical advantage over the classical bearings-only TMA. It makes the ownship maneuver superfluous. In this paper, TMA is carried out using an unscented Kalman filter (UKF). The inclusion of range, course, and speed parameterization is proposed in the UKF target state vector to obtain the convergence of the solution fast. Finally the results of one scenario in Monte-Carlo simulation are presented.

[ABSTRACT]  [FULL TEXT]  [PDF] [CITATIONS]

The paper describes the design, development, and implementation issues of a digital signal processor-based ­integrated hardware set-up for a distribution static compensator (DSTATCOM). A detailed documentation revealing all the design aspects of the important building blocks of the set-up is presented. The transducer, signal conditioning, synchronizing, blanking, protection, optoisolation, and power supply circuits are constructed and assembled to form a prototype laboratory model. In the present work, an H-bridge voltage source inverter-based DSTATCOM has been realized. The efficacy of this arrangement is demonstrated by conducting experiments and the results are discussed.

[ABSTRACT]  [FULL TEXT]  [PDF]

[FULL TEXT]  [PDF]

This paper is concerned with the estimation of amplitude and phase of an analog multi-harmonic signal based on a ­series of differential values of the signal. To this end, assuming the signal fundamental frequency is known ­before hand (i.e., estimated in an independent stage), a complexity-reduced scheme is proposed here, based on the ­matrix ­method classically used to estimate the Fourier coefficients. The reduction in complexity is achieved ­owing to ­completely new analytical and summarized expressions that enable a quick estimation at a low numerical ­error. It is applied in signal ­reconstruction, spectral estimation, system identification, as well as in other important signal ­processing problems. The proposed method of processing can be used for precise root mean square (rms) ­measurements (for power and ­energy) of a periodic signal based on the presented signal reconstruction. The paper investigates the ­errors related to the signal parameter estimation, and there is a computer simulation that demonstrates the accuracy of these algorithms.

[ABSTRACT]  [FULL TEXT]  [PDF]