Department of Electronic Systems

This paper presents an analysis on the performance of decode-and-forward cooperation transmissions in Rician fading channels. The users send the signals using multiband DS-CDMA transmission; the particular complete complementary code sets are used as spreading sets and to provide orthogonality and signal separation. These codes sets have an impulsive autocorrelation sum among each set and orthogonality along the set size. Under the constraint of half-duplex transmission, the performance of the proposed model is compared to the closed-form theoretical performance under similar transmission conditions and applying the suboptimum maximal ratio combiner model at the receiver stage. Then the proposed model is evaluated against a non-cooperative transmission framework using the same spreading sets over Rician fading channels with different K factors. The performance of the cooperative model is shown to be on the verge of the theoretical performance curves in terms of the probability of error. It also manifests an enhanced performance compared to the non-cooperative algorithm under different channel assumptions.

This paper proposes an adaptive combiner model that maximizes the performance of multi-rate cooperative relaying transmission in resources aware systems. Users’ cooperation is applied to smartly profit from the network resources to reach for efficient multi-rate transmissions. The low rate terminal uses a part of his bandwidth and power to relay the high rate user data side by side with his own data. This results in small performance degradation to the low rate user performance. The combiner model at the high rate terminal is carefully investigated for an optimized system performance and an adaptive combiner is proposed. The model calculates the weights adaptively for each bit based on a dynamic-blind method. The adaptive combiner is evaluated against the maximal-ratio combiner MRC and the equal gain combiner ECG to reach for the best model for the multi-rate relaying framework. Based on half-duplex mode, the probability of error performance is studied and compared for each combiner model under different channel conditions. The results show that the proposed adaptive combiner, characterized by its reliability and simplicity, leads to the best performance compared to the other models

Abstract—This paper develops a practical receiver suggested for cooperative systems using decode-and-forward transmission and compares it to the theoretical sub-optimum λ-MRC receiver model. The proposed receiver model adopts a channel blind λ-combiner and employs a practical estimation of the combiner’s weight λ that changes adaptively for each received bit. The λ estimation process relies on a dynamic-blind calculation performed on the incoming bit stream using an approximate formula. The accuracy of the estimated values of λ against the numerical (optimum) values is verified by comparing their effects on the performance curves. Next, the performance of the proposed receiver is evaluated against the sub-optimum receiver using the closed-form performance equations then verified using an actual implementation of the decode-and-forward cooperative algorithm. The use of the proposed receiver is shown to have reliable performance under different channel assignments and provides adaptiv...

In this paper, we propose a cooperative bandwidth allocation strategy for conventional multi-rate transmission in wireless networks. It efficiently assigns the available bandwidth according to the transmission rate in order to enhance the overall performance without additional power consumption. The low rate users cooperate with the high rate users by dedicating a part of their bandwidth to either relay the data or send a part of it. A thorough performance assessment is performed to evaluate the proposed strategy against the conventional management that fairly share the bandwidth regardless of the transmission rate. The cooperative strategy illustrates in terms of the probability of error and outage an enhanced performance and remarkable capability to support higher rates under different transmission conditions.

This paper adopts an efficient strategy that allocates the network resources to the users according to the transmission rate requirement. Based on cooperation and the use of variable length spreading codes, the terminals requiring high transmission rate are supported by larger bandwidth and power in order to enhance their quality of service. The proposed resource allocation strategy assigns the terminals with low transmission rate to cooperate with those with high transmission rate by dedicating a part of their bandwidth and power to either relay their data or send a part of it. This will result in a slight limitation on the performance of the cooperating terminals (low rate). Two proposed schemes are presented namely the relaying strategy and re‐allocation strategy. These strategies are evaluated against the commonly used rate‐matching algorithm which constrains the terminals to fairly share the bandwidth regardless of the transmission rate. The proposed receiver is simple and effi...

This paper develops a new dynamic-blind estimation of the combiner's weight λ suggested for decode-and-forward cooperative based receivers and provides an empirical form for it. The estimation is performed by applying a monotonically decreasing formula on the incoming bit stream. The performance evaluation is investigated using the analytical probability of error (P e) closed-form of the decode-and-forward cooperative transmissions. An adjacency is illustrated between the performances using the values of λ obtained by the proposed estimation against the use of optimum values of λ found by iterative search. A practical implementation of the decode-and-forward cooperative algorithm is also considered and the performance analysis is studied for different channel assignments. It is demonstrated that the proposed dynamic-blind estimation of λ provides in an overall performance on the verge of that of using optimum values of the combiner's weight λ.

— The purpose of this paper is to introduce and initially evaluate an experimental sensory substitution device (SSD), which converts color to audible sound. Our system, called Colorophone provides continuous information about the color, light intensity and distance. The color sonification method is inspired by the human visual system. While designing sonification method we took into consideration mismatch in sensory bandwidth, possible sensory overload, nature of sensory spatiotemporal continuity and cross-modal correspondences between colors and sounds. We conducted a preliminary experimental evaluation of the color and object recognition abilities as well as orientation ability. We show that blindfolded participants can easily acquire the color information coded in the auditory stimuli generated by the Colorophone system after a short learning session. Our preliminary experiments indicate that sonified color information helps in object identification and enhances orientation ability. The Colorophone proved to be an easy to understand and intuitive visual-to-auditory coding system, which shows promising results in future visual rehabilitation of the blind.

We have carried out at laboratory test to study the feasibility of using thermal radiation detectors for online thermal monitoring of electrical systems in wind turbines. A 25 kW frequency converter is instrumented with a thermal camera, operating in the 8-14 lm wavelength range, and a single-pixel thermopile sensor, operating in the 4-8 lm wavelength range, to monitor the temperature development of the power electronics under various load sequences. Both systems performed satisfactorily with insignificant temperature deviations when compared to data from calibrated point contact sensor. With spatial averaging over a 7 mm 9 7 mm for the camera and temporal averaging over 60 s for the thermopile sensor, we reduce the root mean square noise to 45 mK and 68 mK respectively. The low cost and simple operation of the thermopile sensor make it very attractive for condition monitoring applications, whereas the attractive feature of the camera is the possibility of multi-point or distributed temperature measurements.

Designing of color sonification systems provides a possibility of contribution to various fields ranging from rehabilitation of visually impaired through color perception, multisensory art experience to consciousness studies. The design process itself requires understanding and integrating knowledge from many difficult and inherently different branches of science and the resulting sonification method will be highly dependent on the purpose of the system. We present work in progress on designing and experimental verification of color sonification method that will be implemented in Colorophone-a wearable assistive device for the visually impaired, which enables perception of the information about color through sound. Although our system shows promising results in color and object recognition, we would like to enhance the existing color sonification method by designing a framework for experimental verification of our color sonification algorithm. The goal of this paper is therefore to briefly describe our way of thinking in order to provide the basis for the discussion.

Detecting characteristics of 3D scenes is considered one of the biggest challenges for visually impaired people. This ability is nonetheless crucial for orientation and navigation in the natural environment. Although there are several Electronic Travel Aids aiming at enhancing orientation and mobility for the blind, only a few of them combine passing both 2D and 3D information, including colour. Moreover, existing devices either focus on a small part of an image or allow interpretation of a mere few points in the field of view. Here, we propose a concept of visual echolocation with integrated colour sonification as an extension of Colorophone—an assistive device for visually impaired people. The concept aims at mimicking the process of echolocation and thus provides 2D, 3D and additionally colour information of the whole scene. Even though the final implementation will be realised by a 3D camera, it is first simulated, as a proof of concept, by using VIRCO—a Virtual Reality training...

The purpose of this paper is to introduce and initially evaluate an experimental sensory substitution device (SSD), which converts color to audible sound. Our system, called Colorophone provides continuous information about the color, light intensity and distance. The color sonification method is inspired by the human visual system. While designing sonification method we took into consideration mismatch in sensory bandwidth, possible sensory overload, nature of sensory spatiotemporal continuity and cross-modal correspondences between colors and sounds. We conducted a preliminary experimental evaluation of the color and object recognition abilities as well as orientation ability. We show that blindfolded participants can easily acquire the color information coded in the auditory stimuli generated by the Colorophone system after a short learning session. Our preliminary experiments indicate that sonified color information helps in object identification and enhances orientation ability. The Colorophone proved to be an easy to understand and intuitive visual-to-auditory coding system, which shows promising results in future visual rehabilitation of the blind.

The successful development of a system realizing color sonification would enable auditory representation of the visual environment. The primary beneficiary of such a system would be people that cannot directly access visual information—the visually impaired community. Despite the plethora of sensory substitution devices, developing systems that provide intuitive color sonification remains a challenge. This paper presents design considerations, development, and the usability audit of a sensory substitution device that converts spatial color information into soundscapes. The implemented wearable system uses a dedicated color space and continuously generates natural, spatialized sounds based on the information acquired from a camera. We developed two head-mounted prototype devices and two graphical user interface (GUI) versions. The first GUI is dedicated to researchers, and the second has been designed to be easily accessible for visually impaired persons. Finally, we ran fundamental ...

In this letter, a new form of electromagnetic-quantum equations is proposed. The electric and magnetic potentials are expressed through a single Hertz vector, and the systems of quantum and Maxwell equations are transformed into more compact integro-differential ones. These new forms are given for the Schrödinger, Pauli, Dirac and Klein–Gordon equations, and a practical way to calculate them by available software tools is considered.

In this letter, the results on the development and simulation of new three-dimensional nanotraps for cold dressed atoms are considered. The traps are the multi-cell structures built by crossed non-touching carbon or metallic nanotubes. The trapping effect is tuned by the DC and RF currents to confine the strong- or low-potential seeking atoms far enough from the areas of strong Casimir–Polder and spin-flip forces. It is supposed that the developed and simulated multi-cell structures are pertinent for catching the Bose–Einstein condensates to demonstrate the Josephson effect, and to enable the study of the entanglement of confined clouds in three-dimensional nano-cells.

In this paper, the localization of eigenmodes in quasi-1-D pseudo-random potential lattice electron waveguides is studied using the equivalent circuit method applied to the Schrödinger equation. It is found that the mixed deterministic and random discrete potential and limited waveguide width allow only intermediate localization of modes, and their two main types are discovered: the gap-localized and random-lattice localized modes which are stable toward variation of the waveguide's geometry. These modes can be transformed to each other by proper choosing the waveguide parameters. The discovered and studied effects and created models are interesting in the developments of spatial nano-switches of electron waves.

Analysis of nonlinear pendular motion of free dipoles in electric field suggests development of stochasticity under perturbation in the vicinity of separatrix in the phase space. Maximum width of stochastic layer is discussed in terms of types and frequencies of perturbing fields. Variation of applied static electric field intensity is shown to shift the maximum stochasticity. Stochastic motion of dipoles is expected to considerably affect dielectric properties of the materials where formation of voids favours the free motion of dipoles. The fraction of stochastically moving dipoles in the total number of free dipoles has been estimated.