Self-adaptation in next-generation Internet networks: how to react to traffic changes while respecting QoS?

Next-generation network infrastructure should support different services and several levels of quality of service (QoS) and resilience. The main requirements for such multiservice networks are flexibility, effective utilization of network resources, and ability to react to traffic demand changes with time. These requisites lead to the fact that next-generation networks should, to some extend, be "self-adapting," to cope with the need of promptly reacting to traffic demand changes, in an effective way, while taking into account the different requirements in terms of QoS. This paper sketches the reference network scenario and discusses the subject of self-adapting networks, attempting to focus on the key issues that need to be solved to realize future infrastructures. As a relevant example, this paper briefly reports a system developed by the authors' laboratory that implements a traffic engineering solution able to fulfill the mentioned requirements. This system could be regarded as a first concrete step toward the realization of self-adapting networks. In addition, some relevant results that were obtained either by simulation or by experiments on a real test bed are reported to discuss the main characteristics of such a system and assess the feasibility of the concept. Finally, the paper reviews the main hot issues that need to be addressed, in the authors' opinion, by the international research community.     

Analysis and optimization of InGaAsP electro-absorption modulators

A numerical model of bulk electro-absorption modulators has been developed based on a quasi-two-dimensional drift-diffusion approach which includes both the presence of heterostructures and the Fermi statistics for the carriers. We show that the nonlinear behavior of this type of devices is essentially related to hole pile-up and space-charge effects. The simulation results compare favourably with some laboratory measurements on a fabricated device with abrupt hetero-junctions. Two other types of structures have been simulated, one obtained with the inclusion of a thin quaternary layer and the other with a, graded hetero-junction, which eliminate the hole pile-up at the InGaAsP-InP hetero-interface. The paper demonstrates that it is possible to approach the optimum behavior using both the alternatives considered here. Finally, nonlinear effects in short modulators have been investigated     

Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.     

Performance analysis of wireless broadband systems employingoptical fiber links

This paper reports an analysis of the performance of wireless broadband communication systems employing fiber-optic links to connect the base station with the control station. Rainfall attenuation on the radio link, and nonlinear distortions arising from the direct modulation of the laser source, besides the noise contributions coming out from both the optical transmitter and receiver, are considered in the analysis. As far as the radio link is concerned, the outage probability, due to the rainfall attenuation, is recounted for relevant cases; while, concerning the optical link, several carrier-to-noise ratio curves versus the optical modulation index of the channels are reported, varying different system parameters. With respect to the previous literature, a complete analysis of the optical link performance, in this type of systems, has been accomplished by taking into account, simultaneously, all the effects influencing the performance     

Room-temperature metal stamping by microfluidics

We show the possibility to fabricate highly controlled metal micropatterns on a variety of substrates, such as semiconducting or metallic materials, exploiting a combination of spontaneous galvanic displacement reactions with microfluidics. The process is reliable and quite versatile and allows the fabrication of complex patterns of different metals on a number of substrates in few minutes on a conventional laboratory bench.     

The impact of cross-training on team effectiveness.

The authors examined the role of cross-training in developing shared team-interaction mental models, coordination, and performance in a 2-experiment study using computer simulation methodology (for Experiment 1, N=45 teams; for Experiment 2, N=49 teams). Similar findings emerged across the 2 experiments. First, cross-training enhanced the development of shared team-interaction models. Second, coordination mediated the relationship between shared mental models and team performance. However, there was some inconsistency in the findings concerning the depth of cross-training necessary for improving shared mental models. Results are discussed in terms of the impact of different levels of cross-training on team effectiveness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tutorial: Key Elements for WDM Transport Networks

This paper reports a brief review of the key elements for WDM transport networks. In particular, the transmission aspects, the basic elements of WDM networking, and the issues relating to failure restoration and network management are taken into account.     

Comparison of the performance on prosthodontic criteria of several alternative alloys used for fixed crown and partial denture restorations: Department of Veterans Affairs Cooperative Studies project 147

The purpose of this study was to examine the effects of scopolamine on the physiological patterns occurring prior to and during motion sickness stimulation. In addition, the use of physiological profiles in the prediction of motion sickness was evaluated. Sixty subjects ingested either 0.6 mg scopolamine, 2.5 mg methscopolamine, or a placebo. Heart rate (HR), respiratory sinus arrhythmia (an index of vagal tone), and electrogastrograms were measured prior to and during the exposure to a rotating optokinetic drum. Compared to the other groups, the scopolamine group reported fewer motion sickness symptoms, and displayed lower HR, higher vagal tone, enhanced normal gastric myoelectric activity, and depressed gastric dysrhythmias before and during motion sickness induction. Distinct physiological profiles prior to drum rotation could reliably differentiate individuals who would develop gastric discomfort from those who would not. Symptom-free subjects were characterized by high levels of vagal tone and low HR across conditions, and by maintaining normal (3 cpm) electrogastrographic activity during drum rotation. It was concluded that scopolamine offered motion sickness protection by initiating a pattern of increased vagal tone and gastric myoelectric stability.     

Pixel processing in a memory controller

The SX-a programmable pixel processor implemented in a workstation memory controller chip-aims to perform as well as low-end 2D and 3D graphics processors and to surpass low-end imaging accelerators. The following features help accomplish this goal: large internal register set; vectorized RISC-like instruction set; fast access to both main and video memory; fast pixel operations; free operations; unpolluted cache; and single-chip solution. We describe the workstation configuration we used for our tests and the SX processor architecture, followed by the SX instruction set and sample algorithms. Then we present SX performance results for a wide range of operations