Showing papers in "Aeu-international Journal of Electronics and Communications in 2007"
TL;DR: In this article, a novel current-controlled multiple-input single-output (MISO) universal filter employing current differencing transconductance amplifiers (CDTAs) as active elements is described.
Abstract: A novel current-controlled multiple-input single-output current-mode universal filter employing current differencing transconductance amplifiers (CDTAs) as active elements is described. The proposed circuit offers the following attractive features: employment of the minimum number of active and passive components; simultaneous realization of all the standard filtering functions; independent current-control of the parameters ω o and ω o / Q ; no requirement of component matching conditions; employment of only two grounded passive capacitors which is suitable for integrated circuit (IC) implementation; and low passive and active sensitivities. PSPICE simulation results are given to verify the theoretical analysis. An example application using the proposed circuit in cascade realization of the high-order current-mode filter is also presented.
101 citations
TL;DR: A range of possible values of the m parameter based on the analysis of a measurements campaign in urban scenarios is presented, indicating the severity of multipath fading and a measure of channel quality.
Abstract: It is well known that the short-term fading conditions of the received envelope in wireless communications channels can be modelled by means of the Nakagami distribution. The value of the m parameter, also called shape factor , indicates the severity of multipath fading, and is a measure of channel quality, making its estimation necessary in many applications. In this letter, a range of possible values of the m parameter based on the analysis of a measurements campaign in urban scenarios is presented.
92 citations
TL;DR: This work proposes exploiting the distinct cyclostationary properties of signals from different air interfaces as features for air interface identification, providing a seamless interoperability between different standards and an enhanced roaming capability.
Abstract: Reconfigurable Software Radio (SR) equipment is considered as the next evolutionary step in the mobile communications. One of the most crucial properties of a SR terminal is that it is capable of using a wide range of air interface standards, providing a seamless interoperability between different standards and an enhanced roaming capability, paving way to a more flexible and efficient use of spectral resources. This multimode operation has to be supported by a number of key functionalities, one of which is the air interface identification. A SR terminal, when switched on, has to be able to locate and identify the air interfaces available in the frequency environment, and while connected to a network, it has to monitor the presence of alternative air interfaces to perform interstandard handover if necessary. In our work, we propose exploiting the distinct cyclostationary properties of signals from different air interfaces as features for air interface identification.
80 citations
TL;DR: A non-autonomous chaotic circuit which is suitable for high-frequency integrated circuit (IC) realization is presented and a TRNG design which uses a dual oscillator architecture with the proposed continuous-time chaotic oscillator is proposed.
Abstract: A non-autonomous chaotic circuit which is suitable for high-frequency integrated circuit (IC) realization is presented. Simulation and experimental results verifying the feasibility of the circuit are given. We have numerically verified that the bit streams obtained from the stroboscopic Poincare map of the system passed the four basic tests of FIPS-140-2 test suite. We also have verified that the binary data obtained from the hardware realization of this continuous-time chaotic oscillator in the same way pass the full NIST random number test suite. Then, in order to increase the output throughput and the statistical quality of the generated bit sequences, we propose a TRNG design which uses a dual oscillator architecture with the proposed continuous-time chaotic oscillator. Finally, we have experimentally verified that the binary data obtained by this oscillator sampling technique pass the tests of full NIST random number test suite without Von Neumann processing for a higher throughput speed while compared with the previous one where the proposed continuous-time chaotic oscillator is used alone.
80 citations
TL;DR: In this article, the optical properties of polydimethylsiloxane (PDMS) as a high-performance optical material system for optical interconnects are reported, and a first production line for optical waveguide layers is discussed.
Abstract: This paper reports on the optical properties of polydimethylsiloxane (PDMS) as a high-performance optical material system for optical interconnects. It is shown that optical PDMS layers laminated into printed circuit boards meet the requirements for low cost, low loss (0.06 dB/cm at 850 nm), high temperature ( > 290 ∘ C ) stable and mechanically robust electrical–optical circuit boards. A first production line for optical waveguide layers will be discussed.
73 citations
TL;DR: Numerical results show the effects of the variation of contention window size and backoff exponent for service differentiation on 802.15.4 sensor networks and derive that contention Window size is more affective than back off exponent on the saturation throughput while back Off exponent is more affectsive than contentionwindow size on the average delay of every device.
Abstract: In sensor networks, data packets transmitted by different devices in home networking and industrial applications maintain different levels of importance. In this paper, we propose two mechanisms for IEEE 802.15.4 sensor networks to provide multi-level differentiated services which are required by each and every device. Mathematical model based on the discrete-time Markov chain is presented and is analyzed to measure the performance of the proposed mechanisms. Numerical results show the effects of the variation of contention window size and backoff exponent for service differentiation on 802.15.4 sensor networks. From the results, we derive that contention window size is more affective than backoff exponent on the saturation throughput while backoff exponent is more affective than contention window size on the average delay of every device. Simulation results are given to verify the accuracy of the numerical model.
70 citations
TL;DR: In this paper, two circuits for realizing floating inductor (FI), floating capacitor (FC) and floating frequency-dependent negative resistor (FDNR) simulators depending on the passive component selection are introduced.
Abstract: In this paper, two circuits for realizing floating inductor (FI), floating capacitor (FC) and floating frequency-dependent negative resistor (FDNR) simulators depending on the passive component selection are introduced. Both of the developed circuits employ a single active device called modified current feedback operational amplifier (MCFOA) and a minimum number of passive elements. The FIs and FCs use a grounded capacitor thus the developed circuits are very suitable for fully integrated circuit (IC) design. Also, the proposed circuits require no critical passive component matching conditions and/or cancellation constraints. The simulation results using SPICE program are also given to verify the theory to exhibit the performance of the first circuit.
68 citations
TL;DR: In this article, a CMOS realization of the current differencing transconductance amplifier (CDTA) is given, which is a newly reported active building block for current-mode signal processing.
Abstract: In this paper, a CMOS realization of the current differencing transconductance amplifier (CDTA) is given, which is a newly reported active building block for current-mode signal processing. Current differencing stage of the CDTA element is realized using a differential current-controlled current source and in the output stage, floating current sources are used to convert intermediate voltage of z terminal to output currents. Due to the compactness of the circuit, it is capable of high-frequency operation and suitable for video signal-processing applications. The CDTA element is used in a current-mode anti-aliasing video filter, which is designed using operational simulation of a seventh-order passive elliptic filter, so the resulting active filter has the low sensitivity feature of its passive counterpart. The filter has 0.1 dB maximum pass band ripple as imposed by ITU video anti-aliasing filter standard. SPICE-simulation results of both the CDTA element and the seventh-order elliptic filter are given. Simulation results are found in close agreement with theoretical results.
67 citations
TL;DR: In this paper, a current-tunable current-mode multifunction filter with two inputs and two outputs employing only four dual-output current-controlled conveyors (DO-CCCIIs) and two grounded capacitors is proposed.
Abstract: In this paper, a current-tunable current-mode multifunction filter with two inputs and two outputs employing only four dual-output current-controlled conveyors (DO-CCCIIs) and two grounded capacitors is proposed. By appropriately connecting the input and output terminals, the proposed circuit can provide lowpass, bandpass, highpass, bandstop and allpass current responses. The filter also offers an independent electronic control of the natural frequency ( ω o ) and the quality factor ( Q ) through adjusting the bias currents of the DO-CCCIIs. No critical matching conditions are imposed for realizing all the filter responses, and all the incremental parameter sensitivities are low. The characteristics of the proposed circuit are simulated using PSPICE to confirm the theory.
66 citations
TL;DR: In this article, a binary-coded genetic algorithm is proposed for the synthesis of planar arrays, which reduces the sidelobe level generated by a uniform planar array using differential evolution.
Abstract: In this paper, differential evolution (DE), one of the youngest paradigms in evolutionary computation, is applied to the process of synthesizing a planar array factor focused on sidelobe-level reduction. Sidelobe level is a critical array factor parameter in the task of reducing background noise and interference in the most recent Wireless Communications Systems. Minimization of sidelobe level involves nonlinear and non-convex dependence between array factor and its elements parameters becoming a highly complex problem. However, DE has proven to be a fast and efficient algorithm for complex real-valued problems. Subsequently, a binary-coded genetic algorithm is proposed for the synthesis of planar arrays. Numerical results show a promising performance of DE reducing noticeably the sidelobe level generated by a uniform planar array.
56 citations
TL;DR: Simulation results indicate that the proposed neuro-fuzzy operator outperforms competing edge detectors and offers superior performance in edge detection in digital images corrupted by impulse noise.
Abstract: A novel neuro-fuzzy (NF) operator for edge detection in digital images corrupted by impulse noise is presented The proposed operator is constructed by combining a desired number of NF subdetectors with a postprocessor Each NF subdetector in the structure evaluates a different pixel neighborhood relation Hence, the number of NF subdetectors in the structure may be varied to obtain the desired edge detection performance Internal parameters of the NF subdetectors are adaptively optimized by training by using simple artificial training images The performance of the proposed edge detector is evaluated on different test images and compared with popular edge detectors from the literature Simulation results indicate that the proposed NF operator outperforms competing edge detectors and offers superior performance in edge detection in digital images corrupted by impulse noise
TL;DR: An efficient algorithm is proposed that can successfully remove impulse noise from corrupted images while preserving image details and significantly outperforms many other well-known techniques for image noise removal.
Abstract: In this letter, we propose an efficient algorithm, which can successfully remove impulse noise from corrupted images while preserving image details. It is efficient, and requires no previous training. The algorithm consists of two steps: impulse noise detection and impulse noise cancellation. Extensive experimental results show that the proposed approach significantly outperforms many other well-known techniques for image noise removal.
TL;DR: In this article, a two-input three-output current-mode universal filter with three dual-output controlled-controlled current conveyors (DOCCCIIs) and two grounded capacitors is presented.
Abstract: A novel current-controlled two-input three-output current-mode universal filter, which employs only three dual-output controlled-controlled current conveyors (DOCCCIIs) and two grounded capacitors, is presented in this paper. The proposed configuration provides inverting-type lowpass, noninverting-type lowpass, inverting-type bandpass, noninverting-type bandpass, highpass, bandstop and allpass current responses at a high impedance terminal, which enable easy cascadability. The filter also offers an independent electronic control of the natural frequency ω o and the parameter ω o / Q through adjusting the bias current of the DOCCCII. No critical matching condition is required for realizing all the filter responses, and all the incremental parameter sensitivities are low. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.
TL;DR: A high-output impedance current mode single-input and three-outputs (SITO)-type multifunction filter which employs three dual-output current conveyors to simultaneously realize low-pass, high-pass and band-pass responses is presented.
Abstract: This paper presents a high-output impedance current mode single-input and three-outputs (SITO)-type multifunction filter which employs three dual-output current conveyors to simultaneously realize low-pass, high-pass and band-pass responses. The proposed circuit uses grounded-virtually grounded passive components (which makes the circuit ideal for integration and tuning). Moreover, it has low active and passive component sensitivities and does not require critical matching conditions and cancellation constraints.
TL;DR: In this paper, the performance of conventional equalizers including feedforward equalizer and decision feedback equalizer (DFE) is fundamentally limited by the nonlinearity of square-law detection of the photodiode in direct detection systems.
Abstract: We investigate equalizers for electronic dispersion compensation (EDC) of dispersion limited optical fibre communication links in combination with different modulation formats. We show that the performance of conventional equalizers including feedforward equalizer (FFE) and decision feedback equalizer (DFE) are fundamentally limited by the nonlinearity of square-law detection of the photodiode in direct detection systems. Advanced modulation formats such as differential phase shift keying (DPSK) and optical duobinary further enhance this kind of nonlinearity and degrade further FFE/DFE performance. However, nonlinear FFE–DFE and maximum likelihood sequence estimation (MLSE) take into account the mitigation of nonlinear inter symbol interference (ISI) and hence can achieve much better performance. We show that in contrast to other modulation formats, optical single sideband modulation results in approximately linear distortions after detection and thus a simple linear FFE equalizer can achieve good compensation.
TL;DR: In this paper, a novel edge detection algorithm for color images was described, in which smoothness of each pixel in color image is firstly calculated by means of similarity relation matrix and is normalized to maximum gray level.
Abstract: A novel edge detection algorithm for color images was described in this paper. In the proposed method, smoothness of each pixel in color image is firstly calculated by means of similarity relation matrix and is normalized to maximum gray level. In other words, color image in three-dimensional color spaces is mapped into one dimension. Accordingly the edges are performed in such a way that pixels lower than thresholds are assigned to be edge. Thus with proposed method, edge pixels in a color image are detected simultaneously without any complex calculations such as gradient, Laplace and statistical calculations.
TL;DR: In this article, a CMOS operational transconductance amplifier (OTA) called an EOTA, where its transconductorance gain can be electronically and linearly tuned is proposed.
Abstract: A CMOS operational transconductance amplifier (OTA) called as an EOTA, where its transconductance gain can be electronically and linearly tuned is proposed in this paper The realization method is achieved by squaring the transconductance gain of the balanced CMOS OTA The EOTA transconductance gain can be linearly tuned by an external bias current for three decades The linear input-voltage range of about 1 Vp with less than 1% nonlinearity is obtained The usefulness of the proposed EOTA is demonstrated through application example with a current multiplier The performance of the proposed circuit is discussed and confirmed through PSPICE-simulation results
TL;DR: The total scattering and extinction efficiencies of a nihility cylinder of infinite length and circular cross-section are identical and independent of the polarization state of a normally incident plane wave as discussed by the authors.
Abstract: The total scattering and the extinction efficiencies of a nihility cylinder of infinite length and circular cross-section are identical and independent of the polarization state of a normally incident plane wave.
TL;DR: In this paper, the authors present a study of the dedicated short range communications (DSRC) receiver performance under varying signal to noise ratio, velocity, symbol durations and packet lengths.
Abstract: In this paper, we present a study of the dedicated short range communications (DSRC) receiver performance under varying signal to noise ratio, velocity, symbol durations and packet lengths. Conventional channel estimation, which is used in IEEE 802.11a, assumes static channel characteristics for the entire packet duration. That is found to be infeasible for high velocity DSRC applications. Simulation results show that the packet-error-rate increases with the increase in relative velocity. Viterbi decoding substantially improves the performance, but the sensitivity to Doppler shift still exists. Analysis and simulation results show that extending the symbol duration or increasing packet length results in an increase of the packet-error-rate. These results may serve as benchmarks for future DSRC channel estimation methods.
TL;DR: This design of coherently radiating structures considers the optimization of the spacing between antenna elements by using the well-known method of genetic algorithms to set new design philosophies in antenna arrays.
Abstract: The design problem of coherently radiating structures in a linear array geometry is dealt with. The key idea is to accept the unavoidable presence of the mutual coupling between antenna elements but force it to be coherent by including additional passive elements in between the active ones. This design of coherently radiating structures considers the optimization of the spacing between antenna elements by using the well-known method of genetic algorithms. Simulation results for coherently radiating structures with uniform and non-uniform separation are provided. A comparative analysis of the performance of different coherently radiating structures is achieved in order to set new design philosophies in antenna arrays.
TL;DR: This paper investigates the performance of interrupt coalescing analytically and compares it with that of normal interruption, and considers two types of coalescing (viz. count-based and time-based).
Abstract: System performance of Gigabit network hosts can be severely degraded due to interrupt overhead caused by heavy incoming traffic. One of the most popular solutions to mitigate such overhead is interrupt coalescing in which a single interrupt is generated for multiple incoming packets. This is opposed to normal interruption in which an interrupt is generated for every incoming packet. In this paper we investigate the performance of interrupt coalescing analytically and compare it with that of normal interruption. We consider two types of coalescing (viz. count-based and time-based). The system performance is studied in terms of throughput, CPU availability for user applications, latency and packet loss.
TL;DR: It is shown that the handover latency decreases when the UMTS and WLAN are coupled in the proposed way, and the proposed coupling scheme differentiates the data paths according to the type of the traffic and can accommodate traffic from WLAN efficiently, with guaranteed QoS and seamless mobility.
Abstract: We propose a hybrid coupling scheme to support interworking between UMTS and WLAN networks. Under the Tight-coupled system, it is expected that WLAN users can also use UMTS services with guaranteed QoS and seamless mobility. However, the interworking is problematic. The capacity of UMTS core network nodes cannot accommodate the bulky data traffic from WLAN, since the core network nodes are designed to handle the small-sized data of circuit voice calls or short packets. The proposed coupling scheme differentiates the data paths according to the type of the traffic and can accommodate traffic from WLAN efficiently, with guaranteed QoS and seamless mobility. We compare the handover procedures of the proposed coupling strategy with those of the loose and tight coupled schemes. In addition, we analyze the delay based on signaling costs during vertical handover. It is shown that the handover latency decreases when the UMTS and WLAN are coupled in the proposed way.
TL;DR: An efficient HW/SW codesign architecture for H.263 video encoder and its FPGA implementation is presented and a 15.8-16.5 times improvement in coding speed is obtained compared to the software based solution.
Abstract: In this paper, we present an efficient HW/SW codesign architecture for H.263 video encoder and its FPGA implementation. Each module of the encoder is investigated to find which approach between HW and SW is better to achieve real-time processing speed as well as flexibility. The hardware portions include the Discrete Cosine Transform (DCT), inverse DCT (IDCT), quantization (Q) and inverse quantization (IQ). Remaining parts were realized in software executed by the NIOS II softcore processor. This paper also introduces efficient design methods for HW and SW modules. In hardware, an efficient architecture for the 2-D DCT/IDCT is suggested to reduce the chip size. A NIOS II Custom instruction logic is used to implement Q/IQ. Software optimization technique is also explored by using the fast block-matching algorithm for motion estimation (ME). The whole design is described in VHDL language, verified in simulations and implemented in Stratix II EP2S60 FPGA. Finally, the encoder has been tested on the Altera NIOS II development board and can work up to 120 MHz. Implementation results show that when HW/SW codesign is used, a 15.8-16.5 times improvement in coding speed is obtained compared to the software based solution.
TL;DR: In this paper, the stability problems of two new current-mode analog filters employing multiple output current controlled conveyors (MOCCCIIs) were investigated, and a single pole model was replaced for each non-ideal current gain of the MOCCCII.
Abstract: Analog circuit designers have usually focused on the design of circuits employing a minimum number of components, occupying less area and dissipating less power. However, some important issues such as signal limitations and especially stability problems of the analog circuits have not received considerable attention in the literature. Hence, the work described in this paper deals with the stability problems of two new current-mode analog filters employing multiple output current controlled conveyors (MOCCCIIs). Toward that end, a single pole model is replaced for each non-ideal current gain of the MOCCCIIs. Both of the novel universal current-mode active-C filters can simultaneously realize low-pass, band-pass and high-pass/notch filter responses. SPICE and MATLAB simulation results are given to verify the theoretical analysis.
TL;DR: In this article, the authors implemented full-wave rectifiers using operational transconductance amplifiers (OTAs) as only main active circuit elements. But the typical problems of the OTA circuit, such as the input voltage swing limitation and the temperature dependence of the OTAs gain, have been improved.
Abstract: The implementation of full-wave rectifiers using operational transconductance amplifiers (OTAs) as only main active circuit elements is presented in this paper. The proposed scheme makes use of the characteristic of the differential amplifier inside the OTA and avoids the use of diodes. The typical problems of the OTA circuit, the input voltage swing limitation and the temperature dependence of the OTA transconductance gain, have been improved. Simulation and experimental results demonstrate the performance of the proposed rectifier are included.
TL;DR: A new edge detection algorithm is proposed that can reasonably consider White-Gaussian noise reduction and correct location of edge, and provides its specific arithmetic process.
Abstract: Because corruption of image by White-Gaussian noise is a frequently encountered problem in acquisition, transmission and processing of image, and classical edge detection operators such as Roberts, Sobel, Prewitt and LOG operator have the deficiency of being sensitive to White-Gaussian noise, this paper proposes a new edge detection algorithm for Image corrupted by White-Gaussian noise that can reasonably consider White-Gaussian noise reduction and correct location of edge, and provides its specific arithmetic process. Finally, the comparison based on principle of new edge detection algorithm and classical edge detection operator is done, the experimental results indicate that the performance of new edge detection algorithm is better than that of classical edge detection operator.
TL;DR: In this article, a coplanar waveguide (CPW)-fed triangular planar monopole antenna is proposed to achieve a wideband dual-frequency design of a triangular patch and the gap distance for the CPW feeding structure.
Abstract: A novel and simple wideband dual-frequency design of a coplanar waveguide (CPW)-fed triangular planar monopole antenna is proposed. By the proper choice of the flare angle for the triangular patch and the gap distance for the CPW feeding structure, an additional resonant mode and wide impedance matching can be realized. Both theoretical and experimental results of bandwidths and radiation characteristics for prototypes of the proposed antenna have been presented and discussed. The measured - 10 dB impedance bandwidth at the lower band (1.71 GHz) is about 240 MHz and that at the upper band (5.62 GHz) reaches about 2 GHz, which cover the DCS1800 and the IEEE 802.11a 5.2/5.8 GHz WLAN standards, respectively. Good monopole-like radiation patterns with antenna gains of 2.3–3.6 dBi and 3.9–5.6 dBi over the lower and upper bands, respectively, have also been obtained.
TL;DR: This work has developed a framework that can be used for easy testing of different concepts and has proved that the combination of these techniques into a unified system provides a much more stable system.
Abstract: A new approach to collaborative user modelling is presented in this paper. We have developed a framework that can be used for easy testing of different concepts. We have also introduced three different areas where collaborative modelling can be further improved. For the first phase of testing, we have created a hybrid system based on three different collaborative recommender techniques. Since this system implements multiple collaboration techniques, we decided to call this approach Combined Collaborative Recommender. Although each prediction technique can produce adequate results, we have proved that the combination of these techniques into a unified system provides a much more stable system. It should also be pointed out that these analyses were done using a very large dataset (more than 2 million ratings) providing reliable results. Results of these optimisations are presented along with pointers for further development.
TL;DR: This paper proposes a simple scheme that combines the multiple descriptions transform coding method with the discrete wavelet transform (DWT) and shows that the proposed DWT technique outperforms both objectively and subjectively the method based on DCT in the case of packet loss.
Abstract: The objective of multiple description coding (MDC) is to represent a source into multiple descriptions such that various reconstruction qualities are obtained from different subsets of the descriptions. In this paper, we propose a simple scheme that combines the multiple descriptions transform coding (MDTC) method with the discrete wavelet transform (DWT). We compare the performance of the proposed scheme with a discrete cosine transform (DCT)-based scheme prevalent in other papers. Simulation results show that our proposed DWT technique outperforms both objectively and subjectively the method based on DCT in the case of packet loss.
TL;DR: In this paper, a compound probability density function (pdf) model is used to evaluate the performance of wireless systems in shadowed fading channels, where both the desired and cochannels are subject to shadowing and fading.
Abstract: Wireless communication systems are subject to short- and long-term fading of the channel. Instead of the commonly used Nakagami–lognormal model to account for the conditions existing in these shadowed fading channels, a compound probability density function (pdf) model is used to evaluate the performance of wireless systems. While the Nakagami–lognormal lacks a closed-form solution to the pdf of the received power in shadowed fading channels, the compound pdf has an analytical expression for the pdf of the received signal power. The synergy between these two models for the analysis of wireless systems is explored by calculating the bit error rate in a DPSK modem as well as the outage probability in a wireless system in a shadowed fading channel. This is followed by the computation of the outage probability in the general case where both the desired and cochannels are subject to shadowing and fading. The analyses were carried out for both fixed number of cochannels and random number of cochannels. Results demonstrate the usefulness of the compound pdf model for the performance analyses of wireless systems in shadowed fading channels.