Siemens (Portugal)

The energy consumption problem in the mobile industry has become crucial. For the sustainable growth of the mobile industry, energy efficiency (EE) of wireless systems has to be significantly improved. Plenty of efforts have been invested in achieving green wireless communications. This article provides an overview of network energy saving studies currently conducted in the 3GPP LTE standard body. The aim is to gain a better understanding of energy consumption and identify key EE research problems in wireless access networks. Classifying network energy saving technologies into the time, frequency, and spatial domains, the main solutions in each domain are described briefly. As presently the attention is mainly focused on solutions involving a single radio base station, we believe network solutions involving multiple networks/systems will be the most promising technologies toward green wireless access networks.

Recently, Ethernet Passive Optical Networks (EPONs) have received a great deal of interest as a promising cost-effective solution for next-generation high-speed access networks. This is confirmed by the formation of several fora and working groups that contribute to their development; namely, the EPON Forum (http://www.ieeecommunities.org/epon), the Ethernet in the First Mile Alliance (http://www.efmalliance.org), and the IEEE 802.3ah working group (http://www.ieee802.org/3/efm), which is responsible for the standardization process. EPONs are a simple, inexpensive, and scalable solution for high-speed residential access, capable of delivering voice, high-speed data, and multimedia services to end users (Kramer, Mukherjee &Maislos, 2003; Kramer & Pesavento, 2002; Lorenz, Rodrigues & Freire, 2004; Pesavento, 2003; McGarry, Maier & Reisslein, 2004). An EPON combines the transport of IEEE 802.3 Ethernet frames over a low-cost and broadband point-to-multipoint passive optical fiber infrastructure connecting the Optical Line Terminal (OLT) located at the central office to Optical Network Units (ONUs), usually located at the subscriber premises. In the downstream direction, the EPON behaves as a broadcast and select shared medium, with Ethernet frames transmitted by the OLT reaching every ONU. In the upstream direction, Ethernet frames transmitted by each ONU will only reach the OLT, but an arbitration mechanism is required to avoid collisions.

The complexities of common equalizer schemes are analytically analyzed in this paper in terms of complex multiplications per bit. Based on this approach we compare the complexity of mode-division multiplexed digital signal processing algorithms with different numbers of multiplexed modes in terms of modal dispersion and distance. It is found that training symbol based equalizers have significantly lower complexity compared to blind approaches for long-haul transmission. Among the training symbol based schemes, OFDM requires the lowest complexity for crosstalk compensation in a mode-division multiplexed receiver. The main challenge for training symbol based schemes is the additional overhead required to compensate modal crosstalk, which increases the data rate. In order to achieve 2000 km transmission, the effective modal dispersion must therefore be below 6 ps/km when the OFDM specific overhead is limited to 10%. It is concluded that for few mode transmission systems the reduction of modal delay is crucial to enable long-haul performance.

Abstract Organizations are under increased pressure to improve their sustainable performance through the adoption of green supply chain management (GSCM) practices. Small and medium enterprises (SMEs) have lagged behind larger corporations due to a number of factors. Chief among these factors is the lack of resources and capabilities. In this study, we investigate whether entrepreneurial orientation as a distinctive firm‐level resource contributes to the successful implementation of GSCM practices within SMEs. We use primary data obtained from 316 manufacturing SMEs and analyze the data by using a fuzzy‐set qualitative comparative analysis (fsQCA). Our findings show four equifinal configurations of GSCM practices and the components of entrepreneurial orientation (EO) that lead to high environmental performance. Two practices, “eco‐design” and “internal environmental management”, are present in all configurations, with the latter being the single core condition. The components of EO are present in all the configurations. Three distinct configurations lead to the simultaneous achievement of high environmental performance and high economic performance. Some noticeable differences appear in these configurations: “internal environmental management” is no longer a core condition, instead external practices (“green purchasing,” “cooperation with customers including environmental requirements,” and “investment recovery”) and “risk‐taking” become core conditions. We exptrapolate our findings into a set of propositions that expand theory on the link between entrepreneurial orientation and sustainable performance. Our study provides insights for managers who seek to infuse entrepreneurial thoughts and actions into their green supply chain initiatives.

In this letter, a nonlinear semi-analytical model (NSAM) for simulation of few-mode fiber transmission is proposed. The NSAM considers the mode mixing arising from the Kerr effect and waveguide imperfections. An analytical explanation of the model is presented, as well as simulation results for the transmission over a two mode fiber (TMF) of 112 Gb/s using coherently detected polarization multiplexed quadrature phase-shift-keying modulation. The simulations show that by transmitting over only one of the two modes on TMFs, long-haul transmission can be realized without increase of receiver complexity. For a 6000-km transmission link, a small modal dispersion penalty is observed in the linear domain, while a significant increase of the nonlinear threshold is observed due to the large core of TMF.

Three radio over fiber link types are compared to assess their relative performance for the optical transmission of next generation wireless signals having multiple wideband radio channels with high-level modulation. These links differ in their choice of modulation device; either a directly modulated laser (DML) or external modulation using a Mach-Zehnder modulator (MZM) or a reflective semiconductor optical amplifier (RSOA). The DML and RSOA link types are shown to suffer minimal degradation of the uplink wireless range compared to the baseline value without an optical link, using optimum components in terms of cost and performance. The optimum technology depends on the relative merits of simplicity (DML) or optical network architecture flexibility (RSOA).

We propose a noniterative digital backward propagation technique, based on an inverse modified Volterra series transfer function to postcompensate transmission linear and nonlinear impairments in the presence of optical noise. Using a single-channel 40-Gb/s nonreturn-to-zero quadrature phase-shift-keying optical signal propagated over 20 × 80 km of standard single-mode fiber, and performing digital postcompensation around the Nyquist rate, our compensation algorithm is able to surpass the maximum accuracy obtained with a symmetric split-step Fourier method, enabling us to increase the nonlinear tolerance by approximately 2 dB.

A highly linear optical transmitter for radio-over-fiber subcarrier-multiplexed systems is presented. An integrated dual Mach-Zehnder modulator (MZM) is utilized to combine an optical carrier suppressed signal with an optical carrier. The proposed transmitter enables more than 10-dB improvement in the carrier-to-interference ratio compared to a quadrature biased MZM, and similar results to low biased MZM considering similar insertion loss. Negligible radio-frequency power dependence with temperature-induced bias drift is reported, while the low biased MZM is penalized by more than 12 dB for a 15% bias drift. The proposed transmitter reduces the minimum error vector magnitude from 4.2% to 3.5%, when compared to quadrature biased MZM, for a 54-Mb/s orthogonal frequency-division-multiplexed signal.

Dynamic contrast-enhanced magnetic resonance (DCE-MR) of the breast is especially robust for the diagnosis of cancer in high-risk women due to its high sensitivity. Its specificity may be, however, compromised since several benign masses take up contrast agent as malignant lesions do. In this paper, we propose a novel method of 3D multifractal analysis to characterize the spatial complexity (spatial arrangement of texture) of breast tumors at multiple scales. Self-similar properties are extracted from the estimation of the multifractal scaling exponent for each clinical case, using lacunarity as the multifractal measure. These properties include several descriptors of the multifractal spectra reflecting the morphology and internal spatial structure of the enhanced lesions relatively to normal tissue. The results suggest that the combined multifractal characteristics can be effective to distinguish benign and malignant findings, judged by the performance of the support vector machine classification method evaluated by receiver operating characteristics with an area under the curve of 0.96. In addition, this paper confirms the presence of multifractality in DCE-MR volumes of the breast, whereby multiple degrees of self-similarity prevail at multiple scales. The proposed feature extraction and classification method have the potential to complement the interpretation of the radiologists and supply a computer-aided diagnosis system.

A sensing head configuration and the necessary interrogation parameters to simultaneously measure strain and temperature using a single fiber Bragg grating (FBG) are presented and demonstrated. By writing the FBG in a linearly etched fiber, we were able to use the information encoded in the peak wavelength and in the spectral width of the FBG. The spectral width of the grating depends uniquely on the applied strain and is temperature independent. An uncertainty of ±15.26 ¿¿ and ±1.92°C was achieved in the experimental verification.

The emergence of new Internet paradigms has changed the common properties of network data, increasing the bandwidth consumption and balancing traffic in both directions. These facts raise important challenges, making it necessary to devise effective solutions for managing network traffic. Since traditional methods are rather ineffective and easily bypassed, particular attention has been paid to the development of new approaches for traffic classification. This article surveys the studies on peer-to-peer traffic detection and classification, making an extended review of the literature. Furthermore, it provides a comprehensive analysis of the concepts and strategies for network monitoring.

Service providers emphasize the need for faster, cheaper and more reliable deployment of broadband networks, therefore making the hardware manufacturers pursue innovative solutions driving down component complexity, installation time, required skill level and, ultimately, the overall deployment cost for an access network structure. The current dramatic increase in the fiber-to-the-home (FTTH) deployment pace along with the general desire to eventually migrate completely to these systems, puts the passive optical network (PON) deployment issues in the spotlight of current academic and system vendor research. Numerous publications explore new technology developments leading to the reduction in the overall costs required to deploy FTTH networks today, especially in terms of the PON structure, installation time, and required craftsman skill level.

The study of power system of relays requires some previous experience in this field. Laboratories focusing on teaching and researching the area of power-system protection have therefore been amply reported. However, these facilities require the actual presence of the students in the laboratories. To overcome this problem, a power-system-relaying remote laboratory has been developed. To implement this laboratory, a testing system of the relay operating characteristic, together with Matlab-based software, was developed. This remote laboratory enables real power-system-relaying experiments through the Internet. In fact, the user can remotely test a real relay disoperation. This system will therefore allow proficient analysis of sensitivities to relay settings and network configurations.

The coordination methodologies of CAMBADA, a robotic soccer team designed to participate in the RoboCup middle-size league (MSL), are presented. The approach, which relies on information sharing and integration within the team, is based on formations, flexible positionings and dynamic role and positioning assignment. Role/positioning assignment follows a new priority-based algorithm that maintains a competitive formation, covering the most important roles/positionings when malfunctions lead to a reduction of the team size. Coordinated procedures for passing and setplays have also been implemented. With this design, CAMBADA reached the 1st place in the RoboCup'2008 world championship. Competition results and performance measures computed from logs and videos of real competition games are presented and discussed.

This letter proposes the use of a refractive index profile with a graded core and a cladding trench for the design of few-mode fibers, aiming an arbitrary differential mode delay (DMD) flattened over the C+L band. By optimizing the core grading exponent and the dimensioning of the trench, a deviation lower than 0.01 ps/km from a target DMD is observed over the investigated wavelength range. Additionally, it is found that the dimensioning of the trench is almost independent of the target DMD, thereby enabling the use of a simple design rule that guarantees a maximum DMD deviation of 1.8 ps/km for a DMD target between -200 and 200 ps/km.

This study proposes a methodology to support coding professionals in assigning ICD-9-CM codes to inpatient episodes. This subject has been predominantly addressed through the use of natural language processing methods, which show limited generalizability. To surpass this issue, this paper proposes a methodology entailing an adaptive data processing method based on structured electronic health record data, whereby raw clinical data is mapped into a feature set, and based on which supervised learning algorithms are trained. After applying a filter method for feature selection, support vector machine (SVM) classifiers are trained to obtain predictions for assigning codes to each episode. This approach is tested using a dataset of inpatient episodes from a department of Internal Medicine. Classifiers exhibited F1-measure values around 52%. Recall was generally higher than precision, which is considered valuable for coding support purposes. Analyzing results on an individual code basis sheds light on some key-issues regarding the use of structured electronic health record data in supporting clinical coding.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present, for the first time, extensive simulation and experimental characterizations of single SOA-MZI-based multiwavelength conversion (MWC) of NRZ data at 10 Gb/s and RZ data at 40 Gb/s under various parametric conditions deploying ITU standard 100- and 200-GHz channel spacing. We analyze, in particular, the physical performance impairments caused by high-order four-wave mixing interference. Our simulation results indicate the promising performance of the MWC up to eight channels with 200-GHz channel spacing. We further experimentally demonstrate four-channel 10-Gb/s error-free MWC with signal regeneration possibilities and 40-Gb/s MWC with moderate penalties, based on commercially available integrated SOA-MZIs. We obtained clear, open converted eye diagrams and achieved negligible difference in channel performance among all MWC channels at both bit rates. Our results proved the excellent performance of a simple scheme for various future network and system applications, such as all-optical wavelength multicast and grid networking. </para>

This letter proposes a new power equalization scheme based on cascaded semiconductor optical amplifiers, for 10-Gb/s ethernet passive optical networks with uneven topology. For networks with a large number of subscribers, the proposed equalization scheme enables a 16-dB reduction of the receiver dynamic range.

A simple high-speed data transmitter to generate optical single-sideband (OSSB) signals using different electrical signaling formats is presented. The OSSB signal is generated by combining the information signal with the Hilbert transform of that signal, obtained by means of electrical processing. A detailed mathematical model is introduced to evaluate the transmitter performance, considering the generation of OSSB signals with different electrical signaling formats. Two signaling formats are evaluated and compared: nonreturn-to-zero (NRZ) and alternate mark inversion. The optimum transmitter operation conditions, namely bias and drive voltages, are derived according to the signaling format used and confirmed experimentally. Transmission tests conducted using 10-Gb/s OSSB-NRZ signals to assess the improvement obtained by electrical dispersion compensation show a significant mitigation of the dispersion distortion.

A concerted fight against botnets is needed in order to avoid them from becoming a serious threat to global security in the forthcoming years. Zombie detection is currently performed at the host and/or network levels, but these options have important drawbacks: antivirus, firewalls and anti-spyware are not effective against this threat because they are not able to detect hosts that are compromised via new or target specific malicious software and were not designed to protect the network from external attacks or vulnerabilities that are already present inside the local area network. To overcome these limitations, we propose a new botnet detection approach based on the identification of traffic patterns: since each network application, whether it is licit or illicit, has a characteristic traffic pattern that can uniquely identify it, the detection framework will rely on an Artificial Neural Network to identify the licit and illicit patterns. After the identification phase, the system will generate alarms to the system administrator, that can trigger the most appropriate security actions, like blocking the corresponding IP addresses, putting them under a deeper surveillance or acting over some suspicious network segment. A general detection framework was developed in order to incorporate the detection methodology itself, as well as the data collection and storage modules and all the necessary management functions. Some performance tests were already carried out on the proposed system and the results obtained show that the system is stable and fast and the detection approach is efficient, since it provides high detection rates with low computational overhead.