On a Hybrid Preamble/Soft-Output Demapper Approach for Time Synchronization for IEEE 802.15.6 Narrowband WBAN

In this paper, we present a maximum likelihood (ML) based time synchronization algorithm for Wireless Body Area Networks (WBAN). The proposed technique takes advantage of soft information retrieved from the soft demapper for the time delay estimation. This algorithm has a low complexity and is adapted to the frame structure specified by the IEEE 802.15.6 standard for the narrowband systems. Simulation results have shown good performance which approach the theoretical mean square error limit bound represented by the Cramer Rao Bound (CRB)

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

Performance Study of a Near Maximum Likelihood Code-Aided Timing Recovery Technique

International audienceIn this paper, we propose a new code-aided (CA) timing recovery algorithm for various linear constant modulus constellations based on the Maximum Likelihood (ML) estimator. The first contribution is the derivation of a soft estimator expression of the transmitted symbol instead of its true or hard estimated value which is fed into the timing error detector (TED) equation. The proposed expression includes the Log-Likelihood Ratios (LLRs) obtained from a turbo decoder. Our results show that the proposed CA approach achieves almost as good results as the data-aided (DA) approach over a large interval of SNR values while achieving a higher spectral efficiency. We also derive the corresponding CA Cramer Rao Bounds (CRB) for various modulation orders. Contrarily to former work, we develop here the CRB analytical expression for different M-PSK modulation orders and validate them through comparison to empirical CRB obtained by Monte Carlo iterations. The proposed CA estimator realizes an important gain over the non data-aided approach (NDA) and achieves a smaller gap when compared to its relative CA CRB, especially at moderate SNR values where modern systems are constrained to work

CRB derivation and new Code-Aided timing recovery technique for QAM modulated signals

International audience— * In this paper, we propose a maximum likelihood based Code-Aided (CA) timing recovery algorithm for square-QAM modulated signals. We also theoretically derive the analytical expression of the CA Cramer-Rao Bound for time delay estimation. Our simulations show that the proposed CA approach realizes a performance equivalent to the Data-Aided (DA) approach over a large interval of signal to noise ratio (SNR) values

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

QoS and Energy Aware Cooperative Routing Protocol for Wildfire Monitoring Wireless Sensor Networks

Wireless sensor networks (WSN) are presented as proper solution for wildfire monitoring. However, this application requires a design of WSN taking into account the network lifetime and the shadowing effect generated by the trees in the forest environment. Cooperative communication is a promising solution for WSN which uses, at each hop, the resources of multiple nodes to transmit its data. Thus, by sharing resources between nodes, the transmission quality is enhanced. In this paper, we use the technique of reinforcement learning by opponent modeling, optimizing a cooperative communication protocol based on RSSI and node energy consumption in a competitive context (RSSI/energy-CC), that is, an energy and quality-of-service aware-based cooperative communication routing protocol. Simulation results show that the proposed algorithm performs well in terms of network lifetime, packet delay, and energy consumption

Direct Access to N‐tert‐Butanesulfinyl Imines from Aryl Iodides, Alkenyl Alcohols, and N‐tert‐Butanesulfinamide

The reaction of aryl iodides, N‐tert‐butanesulfinamide, and allyl or homoallyl alcohol in the presence of a catalytic amount of Pd(OAc)2, NaHCO3 as a base, and TBAB leads to the formation of N‐tert‐butanesulfinyl imines in moderate yields. In this one‐pot process, a sequential Heck‐type arylation of the alkenol, isomerization of the double bond, and imine formation take place.We thank our Ministerio de Ciencia e Innovación (MCINN; projects CONSOLIDER INGENIO 2010-CDS2007-00006, CTQ2011-24165), the Ministerio de Economía y Competitividad (MINECO; project CTQ2014-53695-P, CTQ2014-51912-REDC, CTQ2016-81797-REDC, CTQ2017-85093-P), the FEDER, the Generalitat Valenciana (PROMETEO 2009/039, PROMETEOII/2014/017), the University of Alicante, the Ministère de l'Enseignement Supérieur et de la Recherche Scientifique Algérienne, Direction de la Coopération et des Echanges Interuniversitaires, Programme de Formation Résidentielle à l'Étranger au titre de l'année universitaire 2016/2017: Programme National Exceptionnel (PNE) for continued financial support

An improved method for the estimation of firing rate dynamics using a Kaiser window /

The aim of this thesis is to develop a novel technique for the estimation of firing rate dynamics from single-unit recordings of neural pulse trains. This method applies an offline digital filtering technique to extract information transmitted by a neuron in teens of a rate code. While there is increasing evidence that the traditional rate coding cannot account for all the information transmitted by a cell, and that information may also be contained in the precise timing of spikes, the firing rate signal remains the benchmark by which the vast majority of electrophysiological studies relating neural activity to functional behaviour have been interpreted. Nevertheless, there does not seem to be an agreement on a single definition of a rate code let alone a consensus on an optimal estimation method. This study raises significant concerns about the validity of some of the most common methods in systems neuroscience, and proposes a simple yet more robust alternative. This latter is based on the convolution of the spike train with an optimally designed Kaiser window. Using computer-simulated as well as experimental data obtained from single-unit recordings of vestibular canal afferents, the proposed technique is shown to consistently outperform the current methods and even to permit robust estimations under time-varying conditions. These results suggest that estimates acquired with the conventional methods are biased and hence models of neural dynamics based on these latter may not be reliable

A soft maximum likelihood technique for time delay recovery

International audienceTime delay synchronization is crucial for the reception quality in digital transmission systems. In this contribution, we consider a maximum likelihood approach and incorporate a soft-demapper to improve the synchronization performance. In particular, the proposed scheme allows to update the time delay at each symbol with an adaptive loop using the Log-Likelihood Ratio (LLR) of each bit provided by the demapper. Simulation results show that the proposed approach provides improvements compared to non data aided approach while avoiding data aided approach overhead

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