Detection and Prevention of Blackhole Attack in the AOMDV Routing Protocol

Mobile ad-hoc network is a collection of dynamically organized nodes where each node acts as a host and router. Mobile ad-hoc networks are characterized by the lack of preexisting infrastructures or centralized administration. So, they are vulnerable to several types of attacks, especially the Blackhole attack. This attack is one of the most serious attacks in this kind of mobile networks. In this type of attack, the malicious node sends a false answer indicating that it has the shortest path to the destination node by increasing the sequence number and decreasing the number of hops. This will have a significant negative impact on source nodes which send their data packets through the malicious node to the destination. This malicious node drop received data packets and absorbs all network traffic. In order overcome this problem, securing routing protocols become a very important requirement in mobile ad-hoc networks. Multipath routing protocols are among the protocols affected by the Blackhole attack. In this paper, we propose an effective and efficient technique that avoids misbehavior of Blackhole nodes and facilitates the discovery for the most reliable paths for the secure transmission of data packets between communicating nodes in the well-known Ad hoc On-demand multi-path routing protocol (AOMDV). We implement and simulate our proposed technique using the ns 2.35 simulator. We also compared on how the three routing protocols AOMDV, AOMDV under Blackhole attack (BHAOMDV), and the proposed solution to counter the Blackhole attack (IDSAOMDV) performs. The results show the degradation on how AOMDV under attack performs, it also presents similarities between normal AOMDV and the proposed solution by isolating misbehaving node which has resulted in increase the performance metrics to the standard values of the AOMDV protocol

Link Quality and MAC-Overhead aware Predictive Preemptive Multipath Routing Protocol for Mobile Ad hoc Networks

In Ad Hoc networks, route failure may occur due to less received power, mobility, congestion and node failures. Many approaches have been proposed in literature to solve this problem, where a node predicts pre-emptively the route failure that occurs with the less received power. However, these approaches encounter some difficulties, especially in scenario without mobility where route failures may arise. In this paper, we propose an improvement of AOMDV protocol called LO-PPAOMDV (Link Quality and MAC-Overhead aware Predictive Preemptive AOMDV).  This protocol is based on new metric combine two routing metrics (Link Quality, MAC Overhead) between each node and one hop neighbor. Also we propose a cross-layer networking mechanism to distinguish between both situations, failures due to congestion or mobility, and consequently avoiding unnecessary route repair process. The LO-PPAOMDV was implemented using NS-2. The simulation results demonstrate the merits of our proposed LO-PPAOMDV with approximately 10-15% increase in the packet delivery ratio while average end-to-end delay is reduced by 20%, and normalized routing load is reduced about 45%, also with 7% increase in the throughput, when compared with PPAOMDV

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

A energy-conserving predictive preemptive multipath routing protocol for adhoc networks: a lifetime improvement

Mobile device are widely used today in MANETs, due to their rich functionality. However, route failure may occur due to lower receive signal strength, mobility, congestion and device failures. Also, the battery life of these devices is very limited and deploying high resource consuming applications such as streaming on these mobile devices, is a challenging task. It is extremely important to efficiently use of the contained resources on these devices when they participate in a mobile ad hoc network. In this paper, we propose an optimization of the cross-layer networking mechanism. Our work focuses on MAC and routing layers of the OSI stack. We propose a cooperation of the routing layer with the MAC layer power-control technique to decrease the energy consumption in transmission within adhoc networks. We propose an energy-conserving multipath routing protocol for adhoc networks lifetime improvement protocol called E-PPAOMDV (Energy aware Predictive Preemptive AOMDV). This protocol is based on new metric to preserves the residual energy of nodes and balances the consumed energy to increase the network lifetime. Also, we propose a mechanism based on Newton interpolation, to distinguish between both situations, failures due to congestion or mobility, and consequently avoiding unnecessary route repair process. The E-PPAOMDV was implemented using NS-2. The simulation results demonstrate the merits of our proposed E-PPAOMDV. Our proposal improves the performance of mobile ad hoc networks by extending the lifetime of the network and decreasing the average consumed energy with approximately 1 to 3%, while the average end-to-end delay is reduced by 33%, normalized routing load by 20 to 27%; also, increasing the packet delivery ratio with approximately 2-10%  and the throughput with 5%  when compared with AOMR-LM

Conception d'un jeu de ressources libres pour le TAL arabe sous Unitex

International audienceThis paper aims to describe the process of building a free Arabic package for the Unitex framework: we proposed a test corpus, we chose a tag set suited to this task and we build dictionaries respecting the LADL DELA format. We describe each of the above particularly the building of dictionaries, for which we designed algorithms for automatic generation of verb and noun inflection graphs. We use the word-based inflection foundations and we define for each lexeme a set of themes. For the verbs, we use five themes given by the user and the graphs generate up to 264 inflected verbal forms; for the nouns and adjectives we use one or at most two themes and the produced graphs generate 63 inflected forms

Traditional orchards and drivers of reproductive performance in a Northern Algerian population of laughing doves (spilopelia senegalensis)

As a good example of species which have adapted in specific anthropogenic habitats as traditional orchards, we studied the breeding ecology of a northern Algerian population of Laughing Doves. We built multifactorial models for three components of Laughing Dove reproductive performance *clutch size, number of hatchlings, and number of fledglings* using generalized linear models (GLM). None of the studied factors: orchard type, laying period, nest location or nest size was affecting clutch size. Number of chicks hatched per nest was affected by orchards type and laying period. Based on model averaged estimates, the hatching success of Laughing Dove was negatively related to “olive orchards and early timing of breeding” (β = −0.53; z = −2.16; p = 0.3). Whereas the number of chicks fledged per nest only differed with orchard type, and model averaged estimates showed a negative relation to olive orchards (β = −0.30 ± 0.17; z = −1.72, p = 0.28). No other variables, horizontal and vertical location or nest size, were related to the variation in breeding performance. So, we suggest that the main drivers of nest failures and reproductive performance of Laughing Doves were egg predation and other variables which are not investigated

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed