On Burst Length Distribution and Preemption Probabilities in OBS Networks with Burst Segmentation

Recently, preemption techniques have attracted considerable attention as a means to provide differentiated quality of service in optical burst switching (OBS) networks. This paper is focused on the analysis of preemption probabilities for bursts within the same priority class. As proposed by Vokkarane and Jue ((2003)* IEEE J Select Areas Commun 21(7): 1198–1209) an incoming burst will preempt the burst in service, within the same priority class, if the residual length of the burst in service is smaller than the incoming burst length. For a general case with wavelength conversion, the preemption probability of contending bursts with a generic service distribution, not necessarily exponential, is analyzed. First, we show that the size distribution for the preempting bursts is shifted to larger values, in comparison to the original burst size distribution. Second, we obtain an upper and lower bound for the preemption probability. Finally, the asymptotic behavior of the OBS switch is analyzed showing that preemption will always occur for a very large number of wavelengths.     

SDN-based wireless user management system

The degradation of end-to-end quality of service (QoS) on mobile users is becoming a common issue for IEEE 802.11 infrastructure-based networks in crowded areas. This research tackles the issue by employing an SDN framework on an integrated wireless/wired environment. Thereby, we present the development and implementation of a system that performs user management by analyzing the network load from the OpenFlow statistics, as well as the wireless information collected from the associated users. In order to analyse the behaviour of the proposed user migration algorithm, we evaluate the system under scenarios with different traffic load and user session duration. From the experiments, we observed that in several cases wireless users get a considerable QoS improvement at the application layer (up to 30% improvement in throughput and up to 20% in delay in our simulations) once the system is activated. Based on the results, we present an analysis on how and when user migration in multi-access point IEEE 802.11 networks can be most effective.     

A Switched Opamp-Based Bandpass Filter: Design and Implementation in a 0.35 μm CMOS Technology

A fully differential SC bandpass filter (central frequency, 58 kHz; Q = 15; and voltage gain, 8) based on the switched-opamp approach is designed and implemented in this work. The filter operates from a single 1 V supply voltage and is realized in a 0.35 m CMOS technology. It has been characterized with a sampling frequency of 1 MHz and its power consumption is about 230 W. As a main internal filter component, an appropiate switched opamp was also designed. Its common-mode feedback circuit was implemented by using an error amplifier and sampling of the output common-mode voltage is carried out by applying a DC offset to level shift the common-mode sample. It provides an accurate common-mode output for a wide temperature and supply voltage ranges.     

Installation d’essais pour la modélisation à échelle réduite des impulsions électromagnétiques

This paper presents a test platform for the scale modeling of electromagnetic pulse effects. The different elements of the installation, i.e. a vertical conical antenna placed on a metallic reference plane, a fast rise time supply generator and a data acquisition and processing facility are described. The field of the antenna has also been studied using a Numerical Electromagnetic Code (Nec)based on the moments method and a comparison with the measurements has been performed. Conclusions resulting from this first stage in the construction of the scale modeling installation are presented.     

CAC-OLSR: Extending OLSR to Provide Admission Control in Wireless Mesh Networks

This work presents an admission control mechanism for multi-hop wireless mesh networks based on the IEEE 802.11 standard and the OLSR routing protocol. This mechanism, called CAC-OLSR, aims at ensuring that traffic flows with quality of service (QoS) requirements, especially voice and video, are only admitted in the mesh network if it has available resources in order to provide flow requirements. In addition, QoS requirements of previously admitted traffic flows cannot be violated. The proposal was evaluated with NS-2 and Evalvid simulations.     

X-SAR interferometry: first results

Repeat-pass interferometry data were acquired during the first and second SIR-C/X-SAR missions in April and October 1994. This paper presents the first results from X-SAR interferometry at four different sites. The temporal separations were one day and six months. At two sites the coherence requirements were met, resulting in high quality interferograms. A digital elevation model in ground range geometry has been derived. The limitations of the X-SAR interferometry are discussed     

Amplification of Cerenkov Luminescence Using Semiconducting Polymers for Cancer Theranostics

The therapeutic efficacy of photodynamic therapy is limited by the ability of light to penetrate tissues. Due to this limitation, Cerenkov luminescence (CL) from radionuclides has recently been proposed as an alternative light source in a strategy referred to as Cerenkov radiation-induced therapy (CRIT). Semiconducting polymer nanoparticles (SPNs) have ideal optical properties, such as large absorption cross-sections and broad absorbance, which can be utilized to harness the relatively weak CL produced by radionuclides. SPNs can be doped with photosensitizers and have ≈100% energy transfer efficiency by multiple energy transfer mechanisms. Herein, an optimized photosensitizer-doped SPN is investigated as a nanosystem to harness and amplify CL for cancer theranostics. It is found that semiconducting polymers significantly amplify CL energy transfer efficiency. Bimodal positron emission tomography (PET) and optical imaging studies show high tumor uptake and retention of the optimized SPNs when administered intravenously or intratumorally. Lastly, it is found that photosensitizer-doped SPNs have excellent potential as a cancer theranostics nanosystem in an in vivo tumor therapy study. This study shows that SPNs are ideally suited to harness and amplify CL for cancer theranostics, which may provide a significant advancement for CRIT that are unabated by tissue penetration limits.     

Multidimensional Waveform Encoding: A New Digital Beamforming Technique for Synthetic Aperture Radar Remote Sensing

This paper introduces the innovative concept of multidimensional waveform encoding for spaceborne synthetic aperture radar (SAR). The combination of this technique with digital beamforming on receive enables a new generation of SAR systems with improved performance and flexible imaging capabilities. Examples are high-resolution wide-swath radar imaging with compact antennas, enhanced sensitivity for applications like alongtrack interferometry and moving object indication, and the implementation of hybrid SAR imaging modes that are well suited to satisfy hitherto incompatible user requirements. Implementation-specific issues are discussed and performance examples demonstrate the potential of the new technique for different remote sensing applications.     

A time Petri net-based method for embedded hard real-time software synthesis

Over the last few years, embedded software synthesis has drawn much attention. However, few works deal with software synthesis for hard real-time systems considering arbitrary inter-tasks precedence and exclusion relations. Code generation for meeting all timing and resource constraints is not a trivial task. Thus, this research area has several open issues, mainly related to generation of predictable-guaranteed scheduled code. The method proposed in this paper starts from a high-level specification, and automatically translates such specification into a time Petri net model; this model is adopted for finding a feasible static schedule meeting all constraints. If found, the approach generates a scheduled code, based on the found feasible schedule. Therefore, the user just enter the specification and receives, as result, the scheduled code. Thus, all intermediary phases are hidden from the users.