Mobility management support and performance analysis for wireless MPLS networks

Multi‐Protocol Label Switching (MPLS) is deployed in the Internet backbone to support service differentiation and traffic engineering. In recent years, there has been interest in extending the MPLS capability to wireless access networks for mobility management support. In this paper, we present analysis of Micro Mobile MPLS, a new micro‐mobility management scheme which integrates the Mobile IP and MPLS protocols by using two‐level hierarchy architecture. Our proposal supports two protocol variants. First, the fast handoff process, which anticipates the LSP procedure set‐up with neighboring locations where a mobile node (MN) may move to, is provided to reduce service disruption. Second, a new mechanism based on the forwarding chain concept is proposed to track efficiently the host mobility within a domain. This concept can significantly reduce registration update costs and provide low handoff latency. Analytical models are developed and simulations are conducted to justify the benefits of our proposed mechanisms. Copyright © 2006 John Wiley & Sons, Ltd.     

On partial-information optimal singular control problem for mean-field stochastic differential equations driven by Teugels martingales measures

This paper is concerned with partial-information mixed optimal stochastic continuous–singular control problem for mean-field stochastic differential equation driven by Teugels martingales and an independent Brownian motion, where the Teugels martingales are a family of pairwise strongly orthonormal martingales associated with Lévy processes. The control variable has two components; the first being absolutely continuous, and the second singular. Partial-information necessary and sufficient conditions of optimal continuous–singular control for these mean-field models are investigated. As an illustration, this paper studies a partial-information linear quadratic control problem of mean-field type involving continuous–singular control.     

Experimental study of complex two-phase instabilities during the start-up of a vertical thermosyphon reboiler operating under vacuum

This paper reports experimental studies of the start-up at reduced pressures (0.105–0.171 bar) and low heat fluxes (1.23–1.55 kW m⁻²) of the thermosyphon reboiler research facility in the Morton Laboratory at the University of Manchester. This is a full scale replica of an industrial sized natural circulation thermosyphon reboiler comprising 50 vertically mounted 25 mm OD tubes of 3 m length with water as the process fluid in the tubes and with steam condensing in the shell side of the reboiler. Unstable behaviour is obtained at start-up with flow-induced instabilities (geysering) when the level of the liquid within the tubes of the bundle is up to the top tubesheet (100% submergence) and also at 83% submergence of the tubes irrespective of the process pressure. At 100% submergence of the tubes, intermittent reversed flows in the entire loop with substantial vibrations are obtained. Chaotic behaviour is obtained at the lower submergence level of 83%. However, start-up at process pressures of 0.22 and 1.04 bar, and low heat fluxes with the entire thermosyphon loop flooded with liquid completely alleviated the flow-induced instabilities observed at the lower submergence levels within the tubes. The flow in the closed loop of liquid is induced very soon after the steam is introduced into the reboiler due to the buoyancy forces emanating from differences in density around the loop. The start-up is smooth and relatively quick, but further instrumentation and control are required for the introduction of the feed to the thermosyphon system once vapour is generated. A control strategy and procedure is proposed which will avoid the instabilities that inherently occur with start-up procedures currently practised in industry.     

Autonomous miniature flying robots: coming soon! - Research, Development, and Results

The exponential growth of the interest and investigations in UAVs is strongly pushing the emergence of autonomous MFRs. This article presented some developments in the ASL-MFR project. A new design methodology was introduced and applied to a quadrotor and a coaxial helicopter enhancing appreciably the robots characteristics by allowing 100% thrust margin and 30 min autonomy (respectively, 40% and 20 min for CoaX). An original concept of hybrid active and passive control is introduced for CoaX. A simulation software permitting rapid MFR reconfiguration and various testing conditions was shown. Finally, a simulation of an obstacle avoidance controller was presented. The numerous developments presented in this article reinforce our conviction in the emergence of autonomous MFRs.     

Capacity Optimization of MIMO Wireless Communication Systems Using a Hybrid Genetic-Taguchi Algorithm

The purpose of this paper is to use a hybrid Taguchi-genetic algorithm to optimize the capacity of MIMO systems with different linear array geometrical configurations at both communication ends (Transmitter and Receiver). The method combines the traditional genetic algorithm, known to have a powerful global exploration capability, and the Taguchi method, which can exploit the optimum offspring and thus, enhance the genetic algorithm. The idea is to use the spatial channel model where the effect of mutual coupling is considered. Each array geometrical configuration has its own contribution in the total channel matrix depending on its physical parameters. The end result is to find out which combination(s) produce the highest capacity value.     

A new worm propagation threat in BitTorrent: modeling and analysis

Peer-to-peer (P2P) networking technology has gained popularity as an efficient mechanism for users to obtain free services without the need for centralized servers. Protecting these networks from intruders and attackers is a real challenge. One of the constant threats on P2P networks is the propagation of active worms. Recent events show that active worms can spread automatically and flood the Internet in a very short period of time. Therefore, P2P systems can be a potential vehicle for active worms to achieve fast worm propagation in the Internet. Nowadays, BitTorrent is becoming more and more popular, mainly due its fair load distribution mechanism. Unfortunately, BitTorrent is particularly vulnerable to topology aware active worms. In this paper we analyze the impact of a new worm propagation threat on BitTorrent. We identify the BitTorrent vulnerabilities it exploits, the characteristics that accelerate and decelerate its propagation, and develop a mathematical model of their propagation. We also provide numerical analysis results. This will help the design of efficient detection and containment systems.     

Sub-Wavelength Solutions for Next-Generation Optical Networks [Topics in Optical Communications]

The recent trend in optical networks is switching packets directly in the optical domain. The aim is to benefit from both packet flexibility and optical transparency. In this article, we review current optical architectures that try to reconcile these two requirements. We discuss the challenges encountered in these new architectures and their respective niches. To meet the requirements of next-generation high-speed optical networks, we also propose a new solution based on the distribution of the aggregation process in the network. The feasibility of this scheme and the benefit that it provides over existing solutions are analyzed in this article.     

Experiments on two immiscible fluids in spherical Couette flow

This paper deals with the experimental instabilities analysis of spherical Couette flow. We consider the flow of two immiscible fluids superimposed between concentric spheres when the outer sphere is fixed and the inner one rotates. The working fluids have rather different viscosities and thus different Reynolds numbers. The obtained results are compared with a reference case of filled gap using one fluid (Γ _max = 20). Experiments are performed for different aspect ratio values, and Laser photometric technique is used for visualization. Our analysis is mainly focused on the type of instabilities and their relationship with the laminar-turbulent transition regime. We intend to explore the combined effects of the aspect ratio and the interaction between the two superposed fluids on the appearance of different instability evolutions. The evolution of the phase velocity for different aspect ratio of heavy fluid Γ _HF = H _HF/d is presented. The immiscible fluids are separated by a liquid–liquid interface (water–oil). In order to control instability occurrence, Taylor number variation is presented versus aspect ratio. Instability phenomena are found to be the same as for the nominal case for large heavy fluid aspect ratios. The first equatorial symmetry breaking of the flow is observed for a critical value Γ _c  = 13 where the Taylor vortex flow is introduced with three stationary cells. For the same aspect ratio, the interaction of the immiscible fluids leads to the appearance of gravitational waves near the equatorial zone. A surface cell, starting before the appearance of Taylor vortices, is detected in the light fluid for low aspect ratios. This cell of Ekman type has not been observed before, to our best knowledge, in spherical Couette flow.     

Intensive sequential chemotherapy with repeated blood stem-cell support for untreated poor-prognosis non-Hodgkin's lymphoma

PURPOSE: To demonstrate the feasibility and efficacy of six ambulatory high-dose sequential chemotherapy courses that include three intensified cycles supported by stem-cell infusion in high-risk and high-intermediate-risk untreated non-Hodgkin's lymphoma (NHL) patients. PATIENTS AND METHODS: A pilot nonrandomized study included 20 untreated patients aged less than 60 years with aggressive histologically identified NHL and two or three adverse-prognosis criteria (International Index). Patients received an ambulatory regimen with high-dose chemotherapy supported by granulocyte colony-stimulating factor (G-CSF) and repeated peripheral-blood stem-cell (PBSC) infusion. The median age was 39 years (range, 20 to 59), with 13 men and seven women. Chemotherapy consisted of one cycle every 21 days for a total of six cycles. The first three cycles (A1, A2, and A3) consisted of cyclophosphamide (Cy) 3,000 mg/m2, doxorubicin (Doxo) 75 mg/m2, and vincristine 2 mg (plus corticosteroids). The last three cycles (B4, B5, and B6) consisted of the same drug combination plus etoposide 300 mg/m2 and cisplatin 100 mg/m2. For an expected duration of 18 weeks, the projected dose-intensity was 25 mg/m2/wk for Doxo and 1,000 mg/m2/wk for Cy. G-CSF 300 micrograms was administered from day 6 following each cycle until neutrophil reconstitution. Two aphereses were performed at approximately day 13 after each A cycle, and PBSCs were injected at day 4 of each B cycle. Radiotherapy on tumor masses > or = 5 cm was scheduled after completion of the last cycle. RESULTS: The median duration of grade 4 neutropenia was 1 day (range, 0 to 7) for each A cycle and 4 days (range, 1 to 10) for each B cycle (P = .02). The median duration of grade 4 thrombopenia was 0 days (range, 0 to 8) for each A cycle and 6 days (range, 1 to 21) for each B cycle (P < .001). Hospitalization for febrile neutropenia was required for 18% and 44% of patients during cycles A and B, respectively (P < .01). Only three patients did not complete the protocol: one due to emergency surgery after cycle B4, one who died after cycle B5 from interstitial pneumonia, and one with delayed hematologic reconstitution after cycle B4. Chemotherapy delivery was optimal (median actual relative dose-intensity, 97%; range, 66 to 100). The median total dose administered over 18 weeks was 18,000 mg Cy (range, 12,000 to 18,000), 450 mg Doxo (range, 300 to 450), 900 mg etoposide (range, 300 to 900), and 300 mg cisplatin (range, 100 to 300). Evaluation of response after six courses showed 13 complete remissions ([CRs] 65%), four partial remissions (PRs), two nonresponses (NRs), and one toxic death. With a median follow-up period of 25 months (range, 16 to 43), 15 patients are alive, with 12 in continuous first CR; five patients relapsed (four of four PRs and one of 13 CRs). Two-year survival and failure-free survival (FFS) rates are 73% and 56%, respectively. The disease-free survival (DFS) rate for the CRs is 86%. CONCLUSION: PBSC support contributes to the feasibility of first-line, very-high-dose, ambulatory chemotherapy delivery in poor-risk NHL and is associated with a high rate of remission and FFS.     

Time-variant balanced routing strategy for underwater wireless sensor networks

In the past decade, researchers’ interest in Underwater Wireless Sensors Networks has rapidly increased. There are several challenges facing the lifetime of UWSNs due to the harsh characteristics of the underwater environment. Energy efficiency is one of the major challenges in UWSNs due to the limited battery budget of the sensor nodes. In this paper, we aim at tackling the energy sink-hole problem that especially hits nodes close to the sink when they run out of battery power before other sensors in the network. We prove that we can evenly distribute the transmission load among mobile sensor nodes by letting sensor nodes adjust their transmission ranges. In this paper, we suppose that sensor nodes may adjust their transmission power up to three levels. Consequently, we strive for deriving the optimal load weight for each possible transmission power level that leads to fair energy consumption among all underwater sensors while taking into account the underwater sensors mobility. Performance results show that energy sink-hole problem is overcame and hence the network lifetime is maximized.