ALBERT

Beschreibung: In cognitive radio networks, the secondary users (SUs) switch the data transmission to another empty spectrum band to give priority to primary users (PUs). In this paper, channel switching in cognitive radio mobile ad hoc networks (CR-MANETs) through an established route is modeled. The probability of channel availability in this route is calculated based on the PU's activity, SU's mobility, and channel heterogeneity. Based on the proposed model, the channel and link availability time are predicted. These predictions are used for channel assignment in the proposed channel allocation scheme. A handoff threshold as well as a life time threshold is used in order to reduce the handoff delay and the number of channel handoffs originating from the short channel usage time. When the channel handoff cannot be done due to the SU's mobility, the local flow handoff is performed to find an appropriate node in the vicinity of a potential link breakage and transfer the current data flow to it. The local flow handoff is performed to avoid possible flow disruption and also to reduce the delay caused by the link breakage. The study reveals that the channel heterogeneity and SU's mobility must be considered as important factors, which affect the performance of the handoff management in the CR-MANETs. The results emphasize on the improvement of the route maintenance probability after using the local flow handoff. It is also stated that the amounts of handoff requirement and handoff delay are decreased after using the predicted channel usage life time and handoff threshold time.

Beschreibung: Due to interference between co-located wireless networks, obtaining accurate channel assessment becomesincreasingly important for wireless network configuration. This information is used, amongothers, for cognitive radio solutions and for intelligent channel selection in wireless networks. Solutionssuch as spectrum analyzers are capable of scanning a wide spectrum range, but are not dedicatedfor channel occupation assessment because they are extremely costly and not able to perform continuousrecording for a time period longer than a few seconds. On the other hand, low-cost solutionslack the flexibility and required performance in terms of configuration and sensing efficiency. To remedythe situation, this paper presents an alternative for channel assessment on top of a commercialsoftware-defined radio platform. Although there exist software solutions for performing spectrumsensing on such platforms, to the best of our knowledge, continuous spectrum sensing and long-termrecording remain challenging. We propose a pioneering solution that is capable of seamless spectrumsensing over a wide spectrum band and guarantees sufficient flexibility in terms of configurations. Theproposed solution is validated experimentally. We demonstrate two advantages of seamless spectrumsensing: the capability of accurate channel occupancy measurement and detecting transient signalssuch as Bluetooth.

Beschreibung: Long-term monitoring of an environment is a fundamental requirement for most wireless sensornetworks. Owing to the fact that the sensor nodes have limited energy budget, prolonging theirlifetime is essential in order to permit long-term monitoring. Furthermore, many applications requiresensor nodes to obtain an accurate estimation of a point-source signal (for example, an animal call orseismic activity). Commonly, multiple sensor nodes simultaneously sample and then cooperate toestimate the event signal. The selection of cooperation nodes is important to reduce the estimationerror while conserving the network's energy. In this paper, we present a novel method for sensor dataacquisition and signal estimation, which considers estimation accuracy, energy conservation, andenergy balance. The method, using a concept of 'virtual clusters,' forms groups of sensor nodes withthe same spatial and temporal properties. Two algorithms are used to provide functionality. The'distributed formation' algorithm automatically forms and classifies the virtual clusters. The 'roundrobin sample scheme' schedules the virtual clusters to sample the event signals in turn. Theestimation error and the energy consumption of the method, when used with a generalized sensingmodel, are evaluated through analysis and simulation. The results show that this method can achievean improved signal estimation while reducing and balancing energy consumption.

Beschreibung: We study the problem of achieving maximum network throughput with fairness among the flows at the nodes in a wireless mesh network, given their location and the number of their half-duplex radio interfaces. Our goal is to find the minimum number of non-overlapping frequency channels required to achieve interference-free communication. We use our existing Select x for less than x topology control algorithm (TCA) to build the connectivity graph (CG), which enhances spatial channel reuse to help minimize the number of channels required. We show that the TCA-based CG approach requires fewer channels than the classical approach of building the CG based on the maximum power. We use multi-path routing to achieve the maximum network throughput and show that it provides better network throughput than the classical minimum power-based shortest path routing. We also develop an effective heuristic method to determine the minimum number of channels required for interference-free channel assignment.

Beschreibung: Excessive depth perception in 3D video is one of the major factors that causes discomfort to the viewer and that can decrease the viewer's quality perception of 3D video. With the idea of real-time quality control of 3D videos, we proposed an edge-based sparse disparity estimation algorithm with a novel similarity metric. The comparative assessment with other four state-of-the-art similarity metrics, implemented within the proposed edge-based disparity estimator, showed higher performance for the novel metric. User tests are conducted to assess the relation between certain disparity statistics and user perception of 3D scene quality that is a retrospective subjective experience of quality. Subjective tests indicate that the viewer discomfort can be predicted best by using maximum and slew rate of 95 percentile scene disparities together.

Beschreibung: In this paper, we address the issue of collaborative information processing for diffusive source localization and tracking using wireless sensor networks capable of sensing in dispersive medium/environment. We first determine the space-time concentration distribution of the dispersion from physical modeling and mathematical formulations of an underwater oil spill scenario, considering the effect of laminar water velocity as an external force. For static diffusive source localization, we propose two parametric estimation techniques based on maximum-likelihood (ML) and best linear unbiased estimator for the special case of our physical dispersion model. We prove the consistency and asymptotic normality of the obtained ML solution when the number of sensor nodes and samples approach infinity, and derive the Cramér-Rao lower bound on its performance. We also propose a particle filter-based target tracking scheme for moving diffusive source and derive the posterior Cramér-Rao lower bound for the moving source state estimates as a theoretical performance bound. The performance of the proposed schemes are shown through numerical simulations and compared with the derived theoretical bounds.

Beschreibung: Radio frequency identification (RFID) is a promising wireless technology for using tiny, remotely powered chips as identifiers. The number of RFID applications is rapidly increasing because RFID technology is convenient, fast, and contactless. However, collisions occur when multiple tags simultaneously transmit their IDs. Therefore, an efficient anti-collision algorithm is needed to accelerate tag identification. In some applications, the reader may repeatedly identify staying tags, which constantly exist in the reader's range. The adaptive query splitting algorithm (AQS) was proposed for reserving information obtained from the last identification process to enable rapid re-identification of staying tags. However, since AQS is a non-blocking algorithm that allows newly arriving tags to use the slots reserved for staying tags, collisions among them are problematic. Thus, semi-blocking AQS (SBA) proposed in this study is designed to reduce the collisions between arriving tags and staying tags by applying a semi-blocking technique in which only a minority of arriving tags use the slots reserved for staying tags. By counting the number of minor arriving tags, SBA estimates the number of unrecognized arriving tags and generates proper queries to minimize their collisions. The identification delay of SBA is analyzed, and simulation results show that SBA significantly outperforms AQS.

Beschreibung: Using the impulse responses of these multipath channels, the bit error rate (BER) performance for binary pulse amplitude modulation impulse radio ultra-wideband communication system is calculated. The optimization location of receiving antenna is investigated by dynamic differential evolution (DDE) and genetic algorithm (GA) to minimize the outage probability. Numerical results show that the performance for reducing BER and outage probability by DDE algorithm is better than that by GA.

Beschreibung: For unmanned air vehicles (UAVs) to survive hostile operational environments, it is always preferableto utilize all wireless positioning sources available to fuse a robust position. While belief propagationis a well-established method for all source data fusion, it is not an easy job to handle all themathematics therein. In this work, a comprehensive mathematical framework for belief propagationbasedall-source positioning of UAVs is developed, taking wireless sources including GlobalNavigation Satellite Systems (GNSS) space vehicles, peer UAVs, ground control stations, and signalof opportunities. Based on the mathematical framework, a positioning algorithm named Beliefpropagation-based Opportunistic Positioning of UAVs (BOPU) is proposed, with an unscented particlefilter for Bayesian approximation. The robustness of the proposed BOPU is evaluated by a fictitiousscenario that a group of formation flying UAVs encounter GNSS countermeasures en route. Fourdifferent configurations of measurements availability are simulated. The results show that theperformance of BOPU varies only slightly with different measurements availability.

Beschreibung: One of the key problems in distributed video coding is the generation of the side information. This task consists of producing an estimation of an image given some neighboring ones, such as those taken by the same camera at different time instants, or, in the case of multiview setups, images taken at the same time instant by different cameras. If both estimations are available, a further problem arises, that is how to merge them in order to create a single side information. This problem is very relevant since a good estimation of the unknown image will require only a few bits to be corrected. Considering a multiview distributed video coding setup, we propose a novel technique for inter-view interpolation based on an occlusion prediction, a new fusion technique based on occlusion detection, and finally an adaptive validation step for switching among the three possible side information images: temporal, inter-view and fusion.We provide a comprehensive set of experimental results, which indicate bit-rate reductions of more than 9 % in the average; moreover, we observe much more consistent results with respect to state-of-the-art techniques.

Beschreibung: The collision frequency function for aerosol particles has already been calculated for the free molecule regime and for the continuum range. The present work, taking into account the influence of internal force fields such as magnetic force, electric force and molecular forces, created by particles themselves, recalculated the collision frequency in the case of particles much smaller than the mean free path of the gas (free molecule regime). Attractive forces increase naturally the collision frequency, while repulsive forces decrease it. The calculation was performed for all types of central forces deriving from a potential, including Coulomb forces and Van der Waals forces.

Beschreibung: As the basis of modern industry, the roles materials play are becoming increasingly vital in this day and age. With many superior physical properties over conventional fluids, the low melting point liquid metal material, especially room-temperature liquid metal, is recently found to be uniquely useful in a wide variety of emerging areas from energy, electronics to medical sciences. However, with the coming enormous utilization of such materials, serious issues also arise which urgently need to be addressed. A biggest concern to impede the large scale application of room-temperature liquid metal technologies is that there is currently a strong shortage of the materials and species available to meet the tough requirements such as cost, melting point, electrical and thermal conductivity, etc. Inspired by the Material Genome Initiative as issued in 2011 by the United States of America, a more specific and focused project initiative was proposed in this paper—the liquid metal material genome aimed to discover advanced new functional alloys with low melting point so as to fulfill various increasing needs. The basic schemes and road map for this new research program, which is expected to have a worldwide significance, were outlined. The theoretical strategies and experimental methods in the research and development of liquid metal material genome were introduced. Particularly, the calculation of phase diagram (CALPHAD) approach as a highly effective way for material design was discussed. Further, the first-principles (FP) calculation was suggested to combine with the statistical thermodynamics to calculate the thermodynamic functions so as to enrich the CALPHAD database of liquid metals. When the experimental data are too scarce to perform a regular treatment, the combination of FP calculation, cluster variation method (CVM) or molecular dynamics (MD), and CALPHAD, referred to as the mixed FP-CVMCALPHAD method can be a promising way to solve the problem. Except for the theoretical strategies, several parallel processing experimental methods were also analyzed, which can help improve the efficiency of finding new liquid metal materials and reducing the cost. The liquid metal material genome proposal as initiated in this paper will accelerate the process of finding and utilization of new functional materials.

Beschreibung: According to the ongoing IEEE 802.11ac amendment, the wireless network is about to embrace the gigabit-per-second raw data rate. Compared with previous IEEE standards, this significant performance improvement can be attributed to the novel physical and medium access control (MAC) features, such as multi-user multiple-input multiple-output transmissions, the frame aggregation, and the channel bonding. In this paper, we first briefly survey the main features of IEEE 802.11ac, and then, we evaluate these new features in a fully connected wireless mesh network using an analytic model and simulations. More specifically, the performance of the MAC scheme defined by IEEE 802.11ac, which employs the explicit compressed feedback (ECFB) mechanism for the channel sounding, is evaluated. In addition, we propose an extended request-to-send/clear-to-send scheme that integrates the ECFB operation to compare with the IEEE 802.11ac-defined one in saturated conditions. The comparison of the two MAC schemes is conducted through three spatial stream allocation algorithms. A simple but accurate analytical model is derived for the two MAC schemes, the results of which are validated with simulations. The observations of the results not only reveal the importance of spatial stream allocations but also provide insight into how the newly introduced features could affect the performance of IEEE 802.11ac-based wireless mesh networks.

Beschreibung: In this paper, we derive a performance comparison between two training-based schemes for multipleinputmultiple-output systems. The two schemes are the time-division multiplexing scheme and therecently proposed data-dependent superimposed pilot scheme. For both schemes, a closed-form expressionfor the bit error rate (BER) is provided. We also determine, for both schemes, the optimalallocation of power between the pilot and data that minimizes the BER.

Beschreibung: Im nationalen Forschungsprojekt „Multifunktionales Batteriespeichersystem (MBS)“ wurden offene Fragen bezüglich der technischen Umsetzbarkeit und der Wirtschaftlichkeit eines netzgekoppelten Batteriespeichersystems mit einer Vanadium-Redox-Flow-Batterie in Kombination mit den Erzeugungsanlagen Photovoltaik und Kleinwindkraft zur intelligenten Vermarktung von erneuerbarer Energie beantwortet (Sterrer et al., Multifunktionales Batteriespeichersystem – MBS-Endbericht. Industrielle Forschung im Rahmen der österreichischen Programmlinie Neue Energie 2020, 3. Ausschreibung, noch nicht veröffentlicht, 2013 ). Die technische Umsetzung und der Demonstrationsbetrieb einer Pilotanlage während zweier Jahre zeigten, dass das Batteriespeichersystem für eine intelligente Vermarktung von erneuerbarer Energie sowie zur Bereitstellung von Systemdienstleistungen zur Netzstabilisierung geeignet ist. Jedoch zeigte die Untersuchung von unterschiedlichen Vermarktungsstrategien für die Pilotanlage, eine Großspeicheranlage und gepoolte PV/Batteriespeicheranlagen sowie deren Erlösmöglichkeiten an den Energiehandels- und Regelenergiemärkten, dass für sämtliche untersuchten Einsatzstrategien in absehbarer Zeit keine positiven Deckungsbeiträge erwirtschaftet werden können. Wenn jedoch die angestrebten Batteriezielkosten von ca. 250 €/kWh bis zum Jahr 2030 erreicht werden, scheint eine zukünftige Umsetzung von Vanadium-Redox-Flow-Batterien, vor allem in Großanlagen (z. B. 10 MW, 100 MWh), für die Teilnahme am Regelenergiemarkt realistisch.

Beschreibung: Special Issue on "Advanced Distributed Wireless Communication Techniques - Theory and Practice"

Beschreibung: “Partial pressure” in humid air is a question very much concerned by scientists and no satisfactory answer has been found to date. This paper proposes a novel method to obtain the “partial pressures” of the water vapor and dry air in humid air. The results obtained by the proposed method are quite different from that obtained by Dalton’s partial pressure law. The fundamental behaviors of water vapor and dry air are studied in depth in wide pressure and temperature ranges. Semi-permeable membrane models are proposed and applied for both saturated and unsaturated humid air. “Improvement factors” are developed to quantitatively describe the magnitude of the interaction between dissimilar molecules. One discovery is that the “partial pressure” of the water vapor in saturated humid air equals P s , rather than ( f · P s ) which was formerly believed. The other is that the interaction between dissimilar molecules may be omitted when temperature is above “cutting-off temperature” for unsaturated humid air. This paper satisfactorily answers the quest of “partial pressures” in humid air from a new perspective.

Beschreibung: Query-by-Example Spoken Term Detection (QbE STD) aims at retrieving data from a speech data repository given an acoustic query containing the term of interest as input. Nowadays, it has been receiving much interest due to the high volume of information stored in audio or audiovisual format. QbE STD differs from Automatic speech recognition (ASR) and keyword spotting (KWS)/spoken term detection (STD) since ASR is interested in all the terms/words that appear in the speech signal and KWS/STD relies on a textual transcription of the search term to retrieve the speech data. This paper presents the systems submitted to the ALBAYZIN 2012 QbE STD evaluation held as a part of ALBAYZIN 2012 evaluation campaign within the context of the IberSPEECH 2012 Conferencea. The evaluation consists of retrieving the speech files that contain the input queries, indicating their start and end timestamps within the appropriate speech file. Evaluation is conducted on a Spanish spontaneous speech database containing a set of talks from MAVIR workshopsb, which amount at about 7 h of speech in total. We present the database metric systems submitted along with all results and some discussion. Four different research groups took part in the evaluation. Evaluation results show the difficulty of this task and the limited performance indicates there is still a lot of room for improvement. The best result is achieved by a dynamic time warping-based search over Gaussian posteriorgrams/posterior phoneme probabilities. This paper also compares the systems aiming at establishing the best technique dealing with that difficult task and looking for defining promising directions for this relatively novel task.

Beschreibung: Per-cell codebook-based limited feedback is highly desirable in coordinated multi-point (CoMP) systems owing to flexibility and compatibility. Except for the per-cell codeword indices, each user should feed back other information for the central unit to reconstruct global channel direction information (CDI) and estimate channel quality information (CQI) for downlink transmission. In this paper, we analyze the essential feedback information for per-cell codebook-based coherent CoMP systems. To show what should be fed back to estimate the CQI, we first derive a conservative CQI estimation to avoid the outage in transmission, which depends on the quantization accuracy and the norm of the global channel. We then analyze whether the per-cell small-scale fading channel norms are necessary to feed back in obtaining the global channel norm and reconstructing the global CDI. Next, we analyze whether the feedback of phase ambiguity (PA) is necessary. Both the analysis and simulation results show that the global channel norm should be fed back instead of the per-cell channel norms. The benefit of the PA feedback is evident only when the number of base stations is large and the number of antennas at each base station is small.

Beschreibung: In estimating emissions reductions brought about by renewables in China, much of existing research assumes that renewables displace coal power. In this paper, this assumption is challenged and the potential environmental effects of photovoltaic (PV) power in North-west China are reevaluated when the marginal generator actually being displaced is taken into account. The annual PV power generation in the North-west Grid is estimated, in this paper, to be as high as 17900GW·h in 2015, roughly equaling to the output of 1.5 nuclear power plants in the US today. The total associated emission reduction in 2015 will at most be 0.36 percent of SO 2 and 0.25 percent of NO x emissions from their 2010 levels in China. Further, PV power may render no emissions reduction at all if it displaces hydropower, which is often used to meet peak demand in the North-west Grid in China. These results imply that a more cost-effective area of focus in the short-term may be on desulfurization and denitrification technologies for coal plants.

Beschreibung: In this paper, we introduce a modified cellular particle filter (CPF) which we mapped on a graphics processing unit (GPU) architecture. We developed this filter adaptation using a state-of-the art CPF technique. Mapping this filter realization on a highly parallel architecture entailed a shift in the logical representation of the particles. In this process, the original two-dimensional organization is reordered as a one-dimensional ring topology. We proposed a proof-of-concept measurement on two models with an NVIDIA Fermi architecture GPU. This design achieved a 411-µs kernel time per state and a 77-ms global running time for all states for 16,384 particles with a 256 neighbourhood size on a sequence of 24 states for a bearing-only tracking model. For a commonly used benchmark model at the same configuration, we achieved a 266-µs kernel time per state and a 124-ms global running time for all 100 states. Kernel time includes random number generation on the GPU as well as with curand. These results attest to the effective and fast use of the particle filter in high-dimensional, real-time applications.

Beschreibung: Objective metrics for visual quality assessment often base their reliability on the explicit modeling of the highly non-linear behavior of human perception; as a result, they may be complex and computationally expensive. Conversely, machine learning (ML) paradigms allow to tackle the quality assessment task from a different perspective, as the eventual goal is to mimic quality perception instead of designing an explicit model the human visual system. Several studies already proved the ability of ML-based approaches to address visual quality assessment; nevertheless, these paradigms are highly prone to overfitting, and their overall reliability may be questionable. In fact, a prerequisite for successfully using ML in modeling perceptual mechanisms is a profound understanding of the advantages and limitations that characterize learning machines. This paper illustrates and exemplifies the good practices to be followed.

Beschreibung: As the geostationary orbit (GEO) is congested in the commercial Ku band, the adjacent satellites willreceive the interference from small aperture terminals which have a wide field of view. To reducethe interference toward the adjacent satellites, code division multiple access (CDMA) with spreadspectrum needs to be adopted in the satellite communications on-the-move system. However, themutual interference between CDMA users leads to the performance loss, which is not acceptable forthe power-sensitive small aperture terminals, and the computation complexity is still an intractableproblem when the conventional iterative minimum mean square error (MMSE) scheme is employedto suppress the multiple access interference (MAI) in satellite systems especially that is coded bylow-density parity-check (LDPC) code. Moreover, the long transmission delays of different userscaused by the long transmission distance require the robustness of the interference suppression forthe asynchronous case. In this paper, a joint chip-level algorithm for CDMA multiuser detectionand LDPC decoding with a new and simple iterative structure based on belief propagation (BP)for satellite systems is developed, which integrates the iterations of multiuser detection and theiterations of LDPC decoding with factor graphs. Through analysis and simulations, it is verified thatthe proposed algorithm is robust to the asynchronous CDMA satellite system, and with the similariterative complexity, the performance of the proposed algorithm outperforms that of the conventionaliterative MMSE scheme in the asynchronous CDMA satellite system.

Beschreibung: In this paper, we propose the use of bit-interleaved coded modulation in alternate-relaying decode-and-forward cooperative communication systems. At the destination, we exploit the interference signal, which results from the simultaneous transmission of data streams through both direct and one of the relay channels to develop an optimal detector. It is shown that the proposed detector can be implemented by parallel concatenating maximum \textit{a posteriori} (MAP) algorithms and demappers to the decoders. The detector exchanges soft information between the decoders and the MAP algorithms in an iterative way for performance improvement. The proposed optimal detector requires a long delay as the destination has to receive and store the entire frame before performing data detection. To avoid this, a sub-optimal detector is also proposed. Unlike the optimal detector, the sub-optimal one exploits two consecutive received packets to decode one packet. It turns out that the sub-optimal detector has less reduced delay, complexity, memory size, and bandwidth loss with a slight increase of the bit-error-rate. Extensive simulation results are presented to demonstrate the effectiveness of the proposed detectors.

Beschreibung: Opportunistic routing (OR) protocols for ad hoc networks basically consist of selecting a few forwardersbetween the source and destination and prioritizing their transmission. The performance ofOR protocols depends on how these two steps are performed. The aim was to reduce the numberof transmissions to deliver packets to the destination. In this paper, we first present a mathematicalmodel to compute the total number of packets including duplicate packets generated by OR protocols.We use the model to analyse well-known OR protocols and understand the reason behind theirincrease in number of transmissions. Next, we propose an OR scheme transmission-aware opportunisticad hoc routing (TOAR) protocol, which attempts to minimize retransmissions. Our proposedOR protocol uses tree structures to select forwarders and prioritize them. The use of tree structureshelps in identifying primary forwarders which carry packets farthest to the destination during eachtransmission round. TOAR also helps in choosing secondary forwarders which will transmit packetsmissed out by the forwarder. The optimized selection of forwarders results in significant reduction inretransmissions, a smaller forwarder list set, and improvement in goodput.

Beschreibung: This contribution focuses on different topics covered by the special issue titled 'Hardware Implementation of Machine vision Systems' including FPGAs, GPUS, embedded systems, multicore implementations for image analysis such as edge detection, segmentation, pattern recognition and object recognition/interpretation, image enhancement/restoration, image/video compression, image similarity and retrieval, satellite image processing, medical image processing, motion estimation, neuromorphic and bioinspired vision systems, video processing, image formation and physics based vision, 3D processing/coding, scene understanding, and multimedia.

Beschreibung: Today, the problem of designing suitable multiprocessor architecture tailored for a target applicationfield raises the need for a fast and efficient multiprocessor system-on-chip (MPSoC) designenvironment. Additionally, the implementation of image processing applications on MPSoC systemwill need to exploit the parallelism and the pipelining in algorithms with the hope of deliveringsignificant reduction in execution times. To take advantage of parallelization on homogeneousMPSoCs and to reduce the programming effort, the proposed design methodology offers moreopportunities for accelerating the parallelization of sequential processing image algorithms on pipelinearchitecture. Our approach provides rapid prototyping tool as a graphic programming environment(CubeGen). Further, it offers a set of parallel software skeletons as a communication library,providing a software abstraction to enable quick implementation of complex image processingapplications on field-programmable gate array (FPGA) platform. The design of homogeneousnetwork of communicating processor is presented from the hardware and software specification downto synthesizable hardware description. Then, we extend our approach to support more complexapplications by implementing a soft multiprocessor for 'multihypotheses model-driven approach forroad recognition' and show the impact of various configuration choices (hardware and software) tomatch the specific application needs. Using the images of a real road scene, the performance resultsof the road recognition algorithm on a Xilinx Virtex-6 FPGA platform not only achieve the desiredlatency but also further improve the tracking performance which depends mainly on the number ofhypotheses.

Beschreibung: A new protocol, called fully distributed space-time coded (FDSTC) protocol having information exchange between relays, is proposed and compared with the conventional distributed space-time coded (DSTC) protocol using non-regenerative relays (NR-relays) and regenerative relays (R-relays). Closed-form error probabilities are derived to verify the simulations. In terms of error performance, the FDSTC protocol gets significant average signal-to-noise ratio (SNR) gains (3.7 dB for NR-relays and 18.1 dB for R-relays). In addition, the impact of the relative distance of relays on the required SNR is reduced up to 70\%. The system diversity order using the FDSTC protocol is higher than that using the DSTC protocol (especially, the FDSTC protocol obtains full diversity with NR-relays). As a result, at the same spectral efficiency, FDSTC has better performance in terms of outage probability in high SNR regions. In terms of energy efficiency, the FDSTC protocol is shown to outperform DSTC for long-range transmissions.

Beschreibung: In this paper, a new class of Fourier-based matrices is studied for deterministic compressed sensing.Initially, a basic partial Fourier matrix is introduced by choosing the rows deterministically fromthe inverse discrete Fourier transform (DFT) matrix. By row/column rearrangement, the matrix isrepresented as a concatenation of DFT-based submatrices. Then, a full or a part of columns of theconcatenated matrix is selected to build a new $M \times N$ deterministic compressed sensing matrix, where $M=p^r$ and $N=L (M+1)$ for prime $p$, and positive integers $r$ and $L \leq M-1$. Theoretically,the sensing matrix forms a tight frame with small coherence. Moreover, the matrix theoreticallyguarantees unique recovery of sparse signals with uniformly distributed supports. From the structureof the sensing matrix, the fast Fourier transform (FFT) technique can be applied for efficient signalmeasurement and reconstruction. Experimental results demonstrate that the new deterministic sensingmatrix shows empirically reliable recovery performance of sparse signals by the CoSaMP algorithm.

Beschreibung: 4G cellular systems envisions a comprehensive all-IP-based solution, including voice, data, and streamed multimedia at much higher data rates and spectral efficiency. Emerging standards and technologies like LTE and M-WiMAX are actually leading towards this vision. The objective of this special issue is to address specific research research issues and solutions on different aspects of 4G wireless systems and beyond. The total six papers included in this special issue demonstrates research outcomes in different aspects of 4G wireless, like scheduling, resource allocation, cognitive and cooperative communications, multicast services and coverage and planning of small cells. We hope that the research results included in this special issue will serve as an important step for further research and development in 4G wireless communication systems.

Beschreibung: This paper has two main contributions. The first is a Bayesian framework for removing two common types of degradations on video known as blotches and line scratches. Most removal techniques assume complete obliteration of the original data at the corrupted sites. This often leads to the introduction of restoration artifacts during removal. Our framework is based on modeling corruption as a semi-transparent layer. This model was introduced earlier by Ahmed et al. (ICIP 2009) for the problem of blotch removal. We show much more blotch removal results than the previous work, and we extend the semi-transparent corruption model to the problem of line removal. The second contribution of this paper is an automated technique for ground-truth generation from infrared scans of corruptions. Previous ground-truth generation efforts require manually inpainting the corrupted regions. The restoration results are evaluated by comparing the reconstructed data against the ground-truth estimates. Comparisons with current blotch and line removal techniques show that the proposed corruption removal framework produces better removal and generates less restoration artifacts.

Beschreibung: The modern society evolves into a sensorial network environment where individual sensor data can be transformed into cumulative and comprehensive representation for human. In a real time, it is independent of current location or behavior. The only limits to increase productivity and to create a smarter surrounding environment are personal habits and technology progress. The paper describes sensorial framework, which is dealing with the current aspects of technology, sociology, and usability in daily life usage of ubiquitous mobile devices with sensors, and arising computed and energy power. Nowadays, most of the common tasks of our lives are mainly influenced by network and social connectivity where infrastructural speed limits are provided by the information flow.

Beschreibung: A novel speech bandwidth extension method based on audio watermark is presented in this paper. The time-domain and frequency-domain envelope parameters are extracted from the high-frequency components of speech signal, and then these parameters are embedded in the corresponding narrowband speech bit stream by the modified least significant bit watermark method which uses perception property. At the decoder, the wideband speech is reproduced with the reconstruction of high-frequency components based on the parameters extracted from bit stream of the narrowband speech. The proposed method can decrease poor auditory effect caused by large local distortion. The simulation results show that the synthesized wideband speech has low spectral distortion and its speech perception quality is greatly improved.

Beschreibung: Cognitive radio (CR) enriches wireless technology systems by harnessing spectrum white spaces. Such systems require continuous and reliable sensing to provide high-quality service to their users and to minimize the interference they may cause to legacy networks. As the simplicity of implementation of energy detectors and their incoherent requirements make them an ideal candidate for this type of application, this work provides a further mathematical analysis to the probability of detection over different fading channels. We derive a tight closed-form expression for the probability of detection over Nakagami channels. In addition, we introduce an accurate recursive algorithm to compute the probability of detection for an odd degree of freedom over additive white Gaussian noise channels, which has been overlooked in the literature so far. Finally, we present the simulation results which concur with the numerical results and which are also a perfect match with the mathematical expressions derived.

Beschreibung: We investigate the estimation of the time of arrival (ToA) of a radio signal transmitted over a flat-fading channel. The path attenuation is assumed to depend only on the transmitter-receiver distance and the path loss exponent (PLE) which, in turn, depends on the physical environment. All previous approaches to the problem either assume that the PLE is perfectly known or rely on estimators of the ToA which do not depend on the PLE. In this paper, we introduce a novel analysis of the performance of the maximum likelihood (ML) estimator of the ToA under an imperfect knowledge of the PLE. Specifically, we carry out a Taylor series expansion that approximates the bias and the root mean square error of the ML estimator in closed form as a function of the PLE error. The analysis is first carried out for a path loss model in which the received signal gain depends only on the PLE and the transmitter-receiver distance. Then, we extend the obtained results to account also for shadow fading scenarios. Our computer simulations show that this approximate analysis is accurate when the signal-to-noise ratio (SNR) of the received signal is medium to high. A simple Monte Carlo method based on the analysis is also proposed. This technique is computationally efficient and yields a better approximation of the ML estimator in the low SNR region. The obtained analytical (and Monte Carlo) approximations can be useful at the design stage of wireless communication and localization systems.

Beschreibung: In this paper, efficient power allocation strategies for multi-hop multi-branch amplify-and-forward networks are developed in generalized fading environments. In particular, we consider the following power optimization schemes: \emph{i)} minimizing of the all transmission powers subject to an outage constraint; and \emph{ii)} minimizing the outage probability subject to constraint on total transmit powers. In this work, we first derive asymptotically tight approximations for the statistics of the received SNR in the system under study with maximal ratio combining (MRC) and selection combining (SC) combiners. With the statistical characterization of the received SNR, we then carryout a thorough performance analysis of the system. Finally, the asymptotic expression of the outage probability is used to formulate the original optimization problems using geometric programming. The geometric programming can be readily transformed into nonlinear convex optimization problem and therefore solved efficiently and globally using the interior-point methods. Numerical results are provided to substantiate the analytical results and to demonstrate the considerable performance improvement achieved by the power allocation.

Beschreibung: The technology for through-wall human detection with ultra-wideband (UWB) radar was discussed. Due to the large amount of UWB radar data, compressive sensing theory was introduced and compressed UWB radar data can be collected. The singular value decomposition algorithm was used to acquire the singular values of compressed radar data. The compressed UWB radar data were collected at two statuses of human being for gypsum wall. The experimental results showed that the singular values with a human target were increased compared with those without a target.

Beschreibung: Second order statistics play an important role in data modeling. Nowadays there is a tendency toward measuringmore signals with higher resolution (e.g. high resolution video), causing a rapid increase of dimensionality of themeasured samples, while the number of samples remains more or less the same. As a result the eigenvalueestimates are significantly biased as described by the Marcenko Pastur equation for the limit of both the numberof samples and their dimensionality going to infinity. By introducing a smoothness factor, we show that theMarcenko Pastur equation can be used in practical situations where both the number of samples and theirdimensionality remain finite.Based on this result we derive methods, one already known and one new to our knowledge, to estimate thesample eigenvalues when the population eigenvalues are known. However, usually the sample eigenvalues areknown and the population eigenvalues are required. We therefore applied one of the these methods in afeedback loop, resulting in an eigenvalue bias correction method.We compare this eigenvalue correction method with state-of-the-art methods, and show that our methodoutperforms other methods particularly in real life situations often encountered in biometrics: underdeterminedconfigurations, high dimensional configurations and configurations where the eigenvalues are exponentiallydistributed.

Beschreibung: The theory of compressive sensing is briefly introduced, and some construction methods for measurement matrix are deduced. A measurement matrix based on Kronecker product is devised, and it has been proved in mathematical proof. Numerical simulations on 2-D image verify that the proposed measurement matrix has better performance in storage space, construction time, and image reconstruction effect when compared with commonly used matrices in compressive sensing. This novel measurement matrix offers great potential for hardware implementation of compressive sensing in image and high-dimensional signal.

Beschreibung: Hyperspectral imaging is a growing area in remote sensing in which an imaging spectrometer collects hundreds of images (at different wavelength channels) for the same area on the surface of the Earth. Hyperspectral images are extremely high-dimensional, and require on-board processing algorithms able to satisfy near real-time constraints in applications such as wildland fire monitoring, mapping of oil spills and chemical contamination, etc. One of the most widely used techniques for analyzing hyperspectral images is spectral unmixing, which allows for sub-pixel data characterization. This is particularly important since the available spatial resolution in hyperspectral images is typically of several meters, and therefore it is reasonable to assume that several spectrally pure substances (called endmembers in hyperspectral imaging terminology) can be found within each imaged pixel. There have been several efforts towards the efficient implementation of hyperspectral unmixing algorithms on architectures susceptible of being mounted onboard imaging instruments, including field programmable gate arrays (FPGAs) and graphics processing units (GPUs). While FPGAs are generally difficult to program, GPUs are difficult to adapt to onboard processing requirements in spaceborne missions due to its extremely high power consumption. In turn, with the increase in the number of cores, multi-core platforms have recently emerged as an easier to program platform compared to FPGAs, and also more tolerable radiation and power consumption requirements. However, a detailed assessment of the performance versus energy consumption of these architectures has not been conducted as of yet in the field of hyperspectral imaging, in which it is particularly important to achieve processing results in real-time. In this article, we provide a thoughtful perspective on this relevant issue and further analyze the performance versus energy consumption ratio of different processing chains for spectral unmixing when implemented on multi-core platforms.

Beschreibung: The H.264/AVC video coding standard introduces some improved tools in order to increase compression efficiency. Moreover, the multi-view extension of H.264/AVC, called H.264/MVC, adopts many of them. Among the new features, variable block-size motion estimation is one which contributes to high coding efficiency. Furthermore, it defines a different prediction structure that includes hierarchical bidirectional pictures, outperforming traditional Group of Pictures patterns in both scenarios: single-view and multi-view. However, these video coding techniques have high computational complexity. Several techniques have been proposed in the literature over the last few years which are aimed at accelerating the inter prediction process, but there are no works focusing on bidirectional prediction or hierarchical prediction. In this article, with the emergence of many-core processors or accelerators, a step forward is taken towards an implementation of an H.264/AVC and H.264/MVC inter prediction algorithm on a graphics processing unit. The results show a negligible rate distortion drop with a time reduction of up to 98% for the complete H.264/AVC encoder.

Beschreibung: Accurate three-dimensional (3D) tracking in bistatic forward scatter radar (BFSR) is a challenging problem because of absent range resolution and poor measurements. In this article, an accurate 3D tracking method of BFSR is proposed. Aiming to overcome the filter divergence caused by large initial state estimation error, firstly, an accurate initial state estimation approach is presented based on analytic derivation and Levenberg--Marquardt algorithm, which has the potential to improve the accuracy of initial state estimation. Furthermore, in order to reduce the computation cost of filtering process and speed up the filtering convergence rate, the accurate initial state estimation and extended Kalman filter algorithm in BFSR are combined to achieve a precise target 3D tracking. Finally, the proposed accurate tracking method is verified through comparative analysis of the simulation results.

Beschreibung: The important techniques in processing hyperspectral data acquired by interference imaging spectrometer onboard Small Satellite Constellation for Environment and Disaster mitigation (HJ-1A) are studied in this article. First, a new noise estimation method, named residual-scaled local standard deviations, is used to analyze the noise condition of HJ-1A hyperspectral images. Then, an optimized maximum noise fraction (OMNF) transform is proposed for dimensionality reduction of HJ-1A images, which adopts an accurately estimated noise covariance matrix for noise whitening. The proposed OMNF method is less sensitive to noise distribution and interference existence, thus it can more efficiently compact useful data information in a low-dimensional space. The proposed OMNF is evaluated through two applications, i.e., spectral unmixing and classification, using the HJ-1A image acquired at the Bohai Sea area in China. It demonstrates that the proposed OMNF provides better performance in comparison with other traditional dimensionality reduction methods.

Beschreibung: In this paper, we suggest a general model for the fixed-valued impulse noise and propose a two-stage method for high density noise suppression while preserving the image details. In the first stage, we apply an iterative impulse detector, exploiting the image entropy, to identify the corrupted pixels and then employ an Adaptive Iterative Mean filter to restore them. The filter is adaptive in terms of the number of iterations, which is different for each noisy pixel, according to the Euclidean distance from the nearest uncorrupted pixel. Experimental results show that the proposed filter is fast and outperforms the best existing techniques in both objective and subjective performance measures.

Beschreibung: A comparison of 4 x 4 multiple-input multiple-output wireless local area network wireless communication characteristics for six different geometrical shapes is investigated. These six shapes include the straight shape corridor with rectangular cross section, the straight shape corridor with arched cross section, the curved shape corridor with rectangular cross section, the curved shape corridor with arched cross section, the L-shape corridor, and the T-shape corridor. The impulse responses of these corridors are computed by applying shooting and bouncing ray/image (SBR/Image) techniques along with inverse Fourier transform. By using the impulse response of these multipath channels, the mean excess delay, root mean square (RMS) delay spread for these six corridors can be obtained. Numerical results show that the capacity for the rectangular cross section corridors is smaller than those for the arched cross section corridors regardless of the shapes. And the RMS delay spreads for the T-and the L-shape corridors are greater than the other corridors.

Beschreibung: In this article, we study the medium access control (MAC) problem inunderwater wireless acoustic networks. We explore the random accessand handshaking (i.e., RTS/CTS) techniques in both single-channeland multi-channel network scenarios. We model and analyze these twoapproaches, and conduct extensive simulations to study theirperformance in various network conditions. Based on our results, weobserve that the performance of both approaches are affected by manyfactors such as data rate, propagation delay and packet size. Ourresults show that the RTS/CTS approach is more suitable for densenetworks with high date rate, whereas the random access approach ispreferred in sparse networks with low data rate. Our results alsodemonstrate that multi-channel techniques can potentially help uscombat the long delay feature of underwater acoustic channels.However, uncoordinated random channel access cannot fully exploitthe advantages of the multi-channel network settings and it performseven worse than the single-channel random access protocol. Only withcareful design and coordination such as multi-channel access withRTS/CTS handshaking process, can multi-channel MAC protocols greatlyimprove the system performance. We believe that this study willprovide useful guidelines for efficient MAC design in underwaterwireless acoustic networks.

Beschreibung: In order to mitigate the mutual interference between ultra-wideband (UWB) impulse radio and other existing wireless systems, a novel adaptive interference-avoiding UWB pulse, in the context of the appealing cognitive radio, is presented based on the radial basis function neural networks. Theoretical and implementation architecture for UWB pulse generator is addressed. Transmission performance in the presence of narrowband interference including tone interference is comprehensively analyzed. The presented generator can adaptively change the spectrum shape of UWB signals according to the authorized users' working states, and hence the mutual interference between UWB and other systems sharing the frequency bands can efficiently be avoided. The critical performance indication parameters, such as the SNR, SIR, and BER of UWB communication links, are also derived. Performance evaluations and comparisons between the proposed scheme and other pulse optimization methods have been provided based on the extensive numerical simulations. It is demonstrated that the presented pulse can indeed achieve much superior performance in terms of either single-link BER or anti-jamming capability.

Beschreibung: Non-line-of-sight (NLOS) error is a bottleneck problem influencing positioning accuracy. However, a large number of scatterers distribute randomly in the surrounding of the mobile station (MS) in the dense multipath environment, such as urban. In most cases, there is no obstacle between scatterer and MS. So, the geographic information of scatterers around MS can be used to restraint NLOS errors and improve the positioning accuracy. If scatterer can be regarded as the virtual base station (BS), the precondition of the positioning algorithm is easier to satisfy than the traditional positioning algorithm, such as circle positioning algorithm. The algorithm proposed in this article selects suitable scatterers with linear constraints by analyzing the Doppler frequency shift of received signals which reflected by scatterers. Thereby, the selected scatterers and only two real BSs form a complete positioning system. In addition, because MS is motionless in most scenarios, BS must be moving to acquire the Doppler frequency shift. The algorithm proposed in this article is adjusted for the scenarios. And the scatterers with linear constraint can also be utilize fully. Simulation results show the algorithm proposed in this article in two different scenarios, not only simplifies the traditional algorithm, but also achieves the higher positioning accuracy.

Beschreibung: This article explores the effects of quantization offeedback information on energy consumption in multiuser wirelesscommunication systems. In order to optimize the energy consumptionof the system, the article concentrates on the amount of transmitenergy, the additional energy due to quantization and theprobability of power outage. Closed form expressions for suchparameters are obtained, where the impact of the number ofquantization bits is explicitly outlined. An optimization problem isthen formulated to find the optimum number of quantization bits ableto minimize the consumption in the energy resources. Simulationsdemonstrate the good results obtainable with the presentedoptimization strategy, and provide effective validation of theanalytic solution presented in the article.

Beschreibung: Analytical expressions have been obtained for calculating an optimal waveform of the pulse exciting elements of an ultra-wideband antenna array. The criterion of optimality is the minimum of integral side-lobe level. The proposed approach enables us to take into account the signal duration and spectrum limitations and also the impulse response of antenna elements.

Beschreibung: The method of current and charge integral equations [1] is applied to numerical electrodynamic analysis of radiation and impedance matching characteristics of parabolic antennas with reflector diameter from 0.5 to 10λ. As a result as opposed to the current method relying on physical optics approximation the influence of feed on reflector’s radiation pattern, the influence of reflector on feed’s impedance matching and the contribution of feed’s rear radiation into reflector’s radiation pattern are all accounted for. A new model of representing a parabolic surface in the form of its square approximation is suggested, which provides almost uniform partitioning grid and has at least 2.5 times less boundary elements that the common revolution surface representation while having the same sampling coefficient. Dependences of antenna’s directivity on reflector dimensions (0.5–10λ) are calculated for six different focus distance to reflector’s diameter ratios using the developed by the authors crystal_U software package. The calculated results are confirmed by good matching with well-known experimental results.

Beschreibung: A dynamic coordinate measurements model for an arbitrary target is synthesized using Doppler measurements from three satellites. The model allows conducting posterior estimation using well-known methods of stochastic filtering theory based on code pseudorange measurements.

Beschreibung: The paper considers principles of designing an auto-generator with optical channel in the feedback circuit based on magnetic-optical crystal, in which magnetic-mechanical oscillations take place. A reference design of auto-generator based on yttrium iron garnet is provided along with its experimental research results.

Beschreibung: It is presented is the possibility to solve the inverse variation problem based on the determination of a primary functional by the results of minimum mean-square error in optimal linear filtering of the signal theory.

Beschreibung: A composite matrix cipher consisting of four partial ciphers and based on perfect binary arrays has been proposed. This cipher possesses an easily controlled level of data protection from unauthorized access and other practically acceptable computational properties.

Beschreibung: The strict expression for probability of a false alarm of is maximal likelihood algorithm of detection of rectangular radiopulses with unknown amplitude and duration is found by means of solution of the Fokker-Planck-Kolmogorov equation with division variables method. In contrast to known before solution, the expression is correct for any detection thresholds and arbitrary a priory value of definite interval of durations.

Beschreibung: Characteristics of efficient estimates of the range, velocity, and acceleration of a rapidly fluctuating target have been obtained during the probing with a sequence of optical pulses. The losses in estimation accuracy of the range, velocity, and acceleration caused by the presence of non-informative parameters have been also found.

Beschreibung: Asymptotic expressions for the characteristics of quasi-likelihood estimation of image area have been obtained by using the local Markov approximation method. It was shown that the accuracy of area estimation is determined by the magnitude of intensity jump over the boundary limiting the area occupied by image.

Beschreibung: This paper considers a phase recovery method for the coherent carrier frequency of the signal Revised by a digital receiver using a unit of digital recovery of the coherent carrier phase. The use of digital phase filter makes it possible to do without the application of traditional phase-locked loop frequency control. The paper also presents a technique for deriving a transfer function of the specified digital filter and considers the issue of its robustness in relation to self-excitation. In addition, the paper presents a functional diagram of this filter.

Beschreibung: Simplified expressions are obtained for the calculation of the eigenfrequencies of a biconical cavity with large apex angles with the use of two symmetrical points at the boundaries of overlapping partial regions in the form of a spherical sector. Using these expressions, the dependence of the cavity eigenfrequencies on the apex angles of the conical elements is studied, and the results are compared with those obtained by the classical finite-element method. The applicability range of the simplified expressions is identified, and recommendations on their use are given.

Beschreibung: Acomparative analysis of the noise immunity and computational complexity of variousGSM signal demodulators in the analyzer of base stations has been carried out, and recommendations were provided for the selection of demodulator depending on the signal environment and acceptable complexity of its implementation.

Beschreibung: Two new presentation forms of multilevel de Bruijn sequences (BS) have been introduced as geometric and algebraic structures. The attractive and practical properties of these structures have been found. This formed the basis for proposing a constructive method for the synthesis of generating and complete classes of BS. It has been shown that the application of the found classes of quaternary BS in encryption ensures a two-fold reduction of the memory space required for storing the cryptographic substitution boxes (S-boxes).

Beschreibung: Linear programming (LP) decoding is an alternative to iterative algorithms for decoding low density parity check (LDPC) codes. Although the practical performance of LP decoding is comparable to message-passing decoding, a significant advantage is its relative amenability to nonasymptotic analysis. Moreover, there turn out to be a number of important theoretical connections between the LP decoding and standard forms of iterative decoding. These connections allow theoretical insight from the LP decoding perspective to be transferred to iterative decoding algorithms. These advantages encouraged many researchers to work in this recent decoding technique for LDPC codes. In this paper, LP decoding for LDPC code is extensively reviewed and is discussed in different segmented areas.

Beschreibung: The paper considers various structureless inertial non-linear models of power amplifiers and methods of their identification. Based on polynomial model with memory and Volterra model the influence of different kinds of input signals, their bandwidth and average power on precision of power amplifier modeling and complexity of model implementation.

Beschreibung: Carrier frequency offset (CFO) due to Doppler frequency shift or frequency mismatch between the transmitter’s and receiver’s oscillators can introduce severe inter-symbol and inter-carrier interference into OFDM systems. A simplified OFDM system model is considered to analyze effects of CFO in theory and simulation. The article briefly reviews some traditional CFO estimation algorithms. Relying on relatively good correlation characteristic of pseudo-noise (PN) sequence, the PN preamble based algorithm of CFO estimation is developed. Performance characteristics of traditional and the new improved algorithms are simulated under different conditions. Results indicate that the PN preamble based algorithm of CFO estimation is more accurate, resource-saving and robust even under poor communications channel condition, such as low SNR and big normalized CFO.

Beschreibung: Characteristics of quasi-likelihood estimates of the target range, velocity, and acceleration have been obtained during the probing with a sequence of optical pulses. The losses in accuracy of quasi-likelihood estimates as compared with the accuracy of maximum likelihood estimates were also found.

Beschreibung: This article presents a numerical solution for radiation from a novel coaxial horn with a partial dielectric loading. The horn is represented as a set of three-layer dielectric loaded coaxial waveguide sections. Characteristic equation has been obtained to calculate phase coefficients for hybrid modes in each section. Applying mode matching technique generalised scattering matrices for each junction between the sections have been obtained, besides that power coupling integrals for each of three different type of junctions have been found in closed-form solutions. Cascading these scattering matrices with transmission matrices of each section yields a generalised scattering matrix of the horn. For the given excitation at the throat of the horn, amplitude and phase of eigenmodes at the aperture of the horn have been determined. Finally, Fourier transform integral of the aperture electric field has been applied to solve radiation problem of the horn. Numerical results on propagation and radiation characteristics of the first four hybrid modes of the horn are presented and it is validated that this solution can be successfully used for full-wave electromagnetic analysis and optimisation of multiband dielectric loaded coaxial feeds.

Beschreibung: The absolute maximum of Gaussian Markov’s stationary process is obtained by means of solution of the Fokker-Planck-Kolmogorov equation with method of variables division. It is shown, known results are special cases of obtained solution. The probability of process location in one of half-plane of its values is specified.

Beschreibung: Der Ausbau der erneuerbaren Energien auf einen Anteil von mindestens 80 % an der Bruttostromerzeugung, der nach dem Energiekonzept der deutschen Bundesregierung bis zum Jahr 2050 erreicht werden soll, ist ein zentraler Bestandteil der Energiewende. Die VDE-Studie „Energiespeicher für die Energiewende“ widmet sich der Frage, welcher Speicherungsbedarf erforderlich ist, um dieses Ziel zu erreichen, und welche Auswirkungen die Speicher sowie ihr Einsatz auf das Übertragungsnetz haben.

Beschreibung: In this paper, a simple strategy based differential evolution was proposed for solving the problem of multi-objective environmental optimal power flow considering a hybrid model (Wind-Shunt-FACTS). The DE algorithm optimized simultaneously a combined vector control based active power of wind sources and reactive power of multi STATCOM exchanged with the electrical power system to minimize fuel cost and emissions. The proposed strategy was examined and applied to the standard IEEE 30-bus with smooth cost function to solve the problem of security environmental economic dispatch considering multi distributed hybrid model based wind and STATCOM controllers. In addition, the proposed approach was validated on a large practical electrical power system 40 generating units considering valve point effect. Simulation results demonstrate that choosing the installation of multi type of FACTS devices in coordination with many distributed wind sources is a vital research area.

Beschreibung: The implementation of a simple power converter for a wound rotor induction generator employing a three phase diode bridge rectifier and a line commutated inverter in the rotor circuit for super synchronous speeds has been proposed. The detailed working of the system in power smoothing mode and maximum power point tracking mode is presented. The current flow in the rotor circuit is controlled (by controlling the firing angle of the line commutated inverter) for controlling the stator power in both the modes. An 8 bit PIC microcontroller has been programmed to vary the firing angle of the line commutated inverter. Experiments have been carried out on a 3-phase, 3.73 kW, 400 V, 50 Hz, 4-pole, 1500 r/min wound rotor induction generator and the results obtained with the generator supplying power in both the modes are furnished. The complete scheme has been modeled using MATLAB/SIMULINK blocks and a simulation study has been conducted. The experimental waveforms are compared with the simulation results and a very close agreement between them is observed.

Beschreibung: The energy consumption of office buildings in China has been growing significantly in recent years. Obviously, there are significant relationships between building envelope and the energy consumption of office buildings. The 8 key building envelope influencing factors were found in this paper to evaluate their effects on the energy consumption of the air-conditioning system. The typical combinations of the key influencing factors were performed in Trnsy simulation. Then on the basis of the simulated results, the multiple regression models were developed respectively for the four climates of China—hot summer and warm winter, hot summer and cold winter, cold, and severely cold. According to the analysis of regression coefficients, the appropriate building envelope design schemes were discussed in different climates. At last, the regression model evaluations consisting of the simulation evaluations and the actual case evaluations were performed to verify the feasibility and accuracy of the regression models. The error rates are within ±5% in the simulation evaluations and within ±15% in the actual case evaluations. It is believed that the regression models developed in this paper can be used to estimate the energy consumption of office buildings in different climates when various building envelope designs are considered.

Beschreibung: Unit commitment (UC) is an optimization problem used to determine the operation schedule of the generating units at every hour interval with varying loads under different constraints and environments. Many algorithms have been invented in the past five decades for optimization of the UC problem, but still researchers are working in this field to find new hybrid algorithms to make the problem more realistic. The importance of UC is increasing with the constantly varying demands. Therefore, there is an urgent need in the power sector to keep track of the latest methodologies to further optimize the working criterions of the generating units. This paper focuses on providing a clear review of the latest techniques employed in optimizing UC problems for both stochastic and deterministic loads, which has been acquired from many peer reviewed published papers. It has been divided into many sections which include various constraints based on profit, security, emission and time. It emphasizes not only on deregulated and regulated environments but also on renewable energy and distributed generating systems. In terms of contributions, the detailed analysis of all the UC algorithms has been discussed for the benefit of new researchers interested in working in this field.

Beschreibung: A deep analysis of orbiting scroll wraps was conducted in this paper by using ANSYS and SolidWorks. Through the modal analysis, the involute of the circle profile orbiting scroll wrap demonstrated a large span in natural frequencies, which led to more superiority in avoiding structural resonances. Based on the dynamic harmonic analysis, loads of frequency changes were gained and the stress and strain distribution of the orbiting scroll wrap in the most dangerous working conditions were obtained, which determined the segments with maximum stress and strain-displacement properties. Two paths defined to elucidate further the structural characteristics of the exhaust chamber provided evidence for the initial correction of orbiting wraps. The results of the present study offer a theoretical basis for the design and manufacture of scroll wraps, and providing a new way to evaluate different scroll wraps.

Beschreibung: This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages. First, a switching model is developed based on quasi-linear inductance profile. Next, based on the switching behaviour, a time average model is obtained to measure the difference between the excitation and generation time in each switching cycle. Finally, to track control voltage and current wave shapes, a small signal model is designed. The effectiveness of the complete multilevel model combining electrical machine, power converter, load and control with programming language is demonstrated through simulations. A PI controller is used for controlling the voltage of the generator. The results presented show that the controller exhibits accurate tracking control of load voltage under different operating conditions. This demonstrates that the proposed model is able to perform an accurate control of the generated output voltage even in transient situations. The simulation is performed to choose the control parameters and study the performance of switched reluctance generator prior to its actual implementation. Initial experimental results are presented using NI-Data acquisition card to control the output power according to load requirements.

Beschreibung: Firewalls are network devices dedicated to analysing and filtering the traffic in order to separate network segments with different levels of trust. Generally theyare placed on the network perimeter and are used to separate the Intranet fromthe Internet. Firewalls are used to forbid some protocols, to shape thebandwidth resources, and to perform deep packet inspection in order to spotmalicious or unauthorized contents passing through the network. In a wirelessmulti-hop network the concept of perimeter is hard to identify and the firewallfunction must be implemented on every node together with routing. But whenthe network size grows, the rule-set used to configure the firewall may growaccordingly and introduce latencies and instabilities for the low-power meshnodes.We propose a novel concept of firewall in which every node filters the trafficonly with a portion of the whole rule-set in order to reduce its computationalburden. Even if at each hop we commit some errors, we show that the filteringefficiency measured for the whole network can achieve the desired precision, with a positive effect on the available network resources. This approach is different from the protection of a space behind a wall: We use the term waterwall to indicate a more distributed and homogeneous filtering function spreadamong all the nodes in the network.

Beschreibung: Recently, real-time simulation of renewable energy sources are indispensible for evaluating the performance of the maximum power point tracking (MPPT) controller, especially in the photovoltaic (PV) system in order to reduce cost in the testing phase. Nowadays, real time PV simulators are obtained by using analog and/or digital components. In this paper, a real-time simulation of a PV system with a boost converter was proposed using only the digital signal processor (DSP) processor with two DC voltage sources to emulate the temperature and irradiation in the PV system. AMATLAB/ Simulink environment was used to develop the real-time PV system with a boost converter into a C-program and build it into a DSP controller TMS320F28335. Besides, the performance of the real-time DSP-based PV was tested in different temperature and irradiation conditions to observe the P-V and V-I characteristics. Further, the performance of the PV with a boost converter was tested at different temperatures and irradiations using MPPT algorithms. This scheme was tested through simulation and the results were validated with that of standard conditions given in the PV data sheets. Implementation of this project helped to attract more researchers to study renewable energy applications without real sources. This might facilitate the study of PV systems in a real-time scenario and the evaluation of what should be expected for PV modules available in the market.

Beschreibung: Die Energiewende führt in Europa zum raschen Ausbau der erneuerbaren Energien (EE), insbesondere von Windenergie und Photovoltaik. Wegen der kurzen Volllaststunden sind hohe Leistungen zu installieren, die aber die Netzspitzenlast und die vorhandenen Speicherpotenziale überschreiten können und damit nicht adäquat genutzt werden können. Der Ausbau der zentralen und dezentralen Speicherkapazitäten ist eine Notwendigkeit auf dem Weg zur überwiegend regenerativen Energieversorgung.

Beschreibung: Effective utilization of renewable energy sources and efficient management of electric energy are essential for any developing countries like India. This can be envisioned through the implementation of concepts of smart grid (SG). One of the key requisites for SG implementation is that the grid should be completely observable. Renovation of conventional Indian power grid to a SG necessitates incorporation of the phasor measurement units (PMUs) in the present power grid measurement and monitoring system. Since the cost of PMU is high and any bus containing a PMU makes the neighboring connected buses observable, optimal placement of PMUs is very important for complete observability of the grid. This paper proposes optimal redundant geographical locations in the northern, eastern and north-eastern regions of Indian power grid for PMU placement. The PMUs installed in these geographical locations will make the grid completely observable and maintain the observability under the conditions of failure of some PMUs or branch outages. Integer linear programming has been used for finding the optimal PMU locations. The results proposed in this paper can be a stepping stone for revamping the Indian power grid to a SG ensuring complete observability during different contingency conditions.

Beschreibung: If the heat of road surface can be stored in summer, the road surface temperature will be decreased to prevent permanent deformation of pavement. Besides, if the heat stored is released, it can supply heat for buildings or raise the road surface temperature for snow melting in winter. A road-solar energy system was built in this study, and the heat transfer mechanism and effect of the system were analyzed according to the monitored solar radiant heat, the solar energy absorbed by road and the heat stored by soil. The results showed that the road surface temperature was mainly affected by solar radiation, but the effect is hysteretic in nature. The temperature of the solar road surface was 3°C–6°C lower than that of the ordinary road surface. The temperature of the solar road along the vertical direction was 2°C–5°C lower than that of the ordinary road. The temperature difference increased as the distance to the heat transfer tubes decreased. The average solar collector efficiency of the system was 14.4%, and the average solar absorptivity of road surface was 36%.

Beschreibung: We propose a relaying scheme based on superposition coding (SC) with discrete adaptive modulation and coding (AMC) for a three-node wireless relay system, based on half duplex transmission, where each node decodes messages by successive interference cancelation (SIC). Unlike the previous works where the transmission rate of each link is assumed to achieve Gaussian channel capacity, we design a practical superposition-coded relaying scheme with discrete AMC while taking into account the effect of decoding errors at each stage of the SIC process at each node. In our scheme, hierarchical modulation (HM) is used to create an SC message composed of one basic and one superposed message with optimized power allocation. We firstly introduce the proposed scheme without forward error correction (FEC) for high signal-to-noise ratio (SNR) region and provide the optimal power allocation between the superimposed messages. Next, we extend the uncoded scheme to incorporate FEC to overcome bad channel conditions. The power allocation in this case is based on an approximated expression of the bit error rate (BER). Numerical results show the performance gains of the proposed SC relaying scheme with HM compared to conventional schemes, over a large range of SNRs.

Beschreibung: We consider the Gaussian framework for reverberant audio source separation, where the sources aremodeled in the time-frequency domain by their short-term power spectra and their spatial covariancematrices. We propose two alternative probabilistic priors over the spatial covariance matrices whichare consistent with the theory of statistical room acoustics and we derive expectation-maximizationalgorithms for maximum a posteriori (MAP) estimation. We argue that these algorithms provide astatistically principled solution to the permutation problem and to the risk of overfitting resultingfrom conventional maximum likelihood (ML) estimation. We show experimentally that in a semi-informed scenario where the source positions and certain room characteristics are known, the MAPalgorithms outperform their ML counterparts. This opens the way to rigorous statistical treatment ofthis family of models in other scenarios in the future.

Beschreibung: In this paper, we address the problem of quantizer design optimized for a source localization applicationin acoustic sensor networks where physically separated sensors make measurements of acousticsignal energy, quantize them, and transmit the quantized data to a fusion node, which then producesan estimate of the source location. We propose an iterative regular quantizer design algorithm thatminimizes the localization error. To construct regular quantization partitions, we suggest the averagedistance error as a metric in the functional quantization since the distance is monotonic in each sensorreading. Furthermore, to guarantee minimization of the localization error, we propose a new techniqueto update the codewords and prove that the localization error can be reduced at each iterationwhile the average distance error remains nonincreasing by applying our update technique. Our experimentsshow that our proposed algorithm yields significantly improved performance as comparedwith traditional quantizer designs.

Beschreibung: In this paper, a reduced complexity Log-MAP algorithm based on a non-recursive approximation of the max* operator is presented and studied for turbo trellis-coded modulation (TTCM) systems. In the algorithm, denoted as AvN Log-MAP, the max* operation is generalized and performed on n ¿ 2 arguments. The approximation is derived from the Jensen inequality. The non-recursive form of the max* calculations allows to achieve significant reduction in the decoding effort in comparison to the conventional Log-MAP algorithm. Bit-error rate performance simulation results for serial and parallel TTCM schemes in the additive white Gaussian noise and uncorrelated Rayleigh fading channels show that the AvN Log-MAP algorithm performs close to the Log-MAP. Performance and complexity comparisons of the AvN Log-MAP algorithm against the Log-MAP and several relevant reduced complexity turbo decoding algorithms proposed in the literature reveal, that it offers favorable low computational effort for the price of small performance degradation.

Beschreibung: In this article, we investigate the information-theoretical performance of a cooperative orthogonalfrequency division multiplexing (OFDM) system with imperfect channel estimation. Assuming thedeployment of training-aided channel estimators, we derive a lower bound on the achievable rate forthe cooperative OFDM system with amplify-and-forward relaying over frequency-selective Rayleighfading channels. The bound is later utilized to allocate power among the training and datatransmission phases. Numerical results demonstrate that the proposed power allocation schemebrings between 5 and 19% improvement depending on the level of signal-to-noise ratio and relaylocations.

Beschreibung: Online tracking has shown to be successful in tracking of previously unknown objects. However, there are two important factors which lead to drift problem of online tracking, the one is how to select the exact labeled samples even when the target locations are inaccurate, and the other is how to handle the confusors which have similar features with the target. In this article, we propose a robust online tracking algorithm with adaptive samples selection based on saliency detection to overcome the drift problem. To deal with the problem of degrading the classifiers using mis-aligned samples, we introduce the saliency detection method to our tracking problem. Saliency maps and the strong classifiers are combined to extract the most correct positive samples. Our approach employs a simple yet saliency detection algorithm based on image spectral residual analysis. Furthermore, instead of using the random patches as the negative samples, we propose a reasonable selection criterion, in which both the saliency confidence and similarity are considered with the benefits that confusors in the surrounding background are incorporated into the classifiers update process before the drift occurs. The tracking task is formulated as a binary classification via online boosting framework. Experiment results in several challenging video sequences demonstrate the accuracy and stability of our tracker.