MaxHopCount: A New Drop Policy to Optimize Messages Delivery Rate in Delay Tolerant Networks

Communication has become a necessity, not only between every point on the earth, but also on the globe. That includes hard topography, highlands, underwater areas, and also space- crafts on other planets. However, the classic wired internet cannot be implemented in such areas, hence, researchers have invented wireless networks. The big challenge for wireless networking nowadays, is maintaining nodes connected in some difficult conditions, such as intermittent connectivity, power failure, and lot of obstacles for the interplanetary networks. In these challenging circumstances, a new networking model arises; it is Delay Tolerant networking which is based on the Store-Carry-and-Forward mechanism. Thus, a node may keep a message in its buffer for long periods of time; until a delivery or forward chance arises then it transmit it to other nodes. One of the big issues that confront this mechanism is the congestion of nodes buffer due to the big number of messages and the limited buffer size. Here, researchers have proposed buffer management algorithms in order to deal with the buffer overload problem, and they called it Drop Policies. In our present work, we propose a new Drop policy which we have compared to other existing policies in different conditions and with different routing protocols, and it always shows good result in term of number of delivered messages, network overhead and also average of latency

Towards a GNU/Linux IEEE 802.21 Implementation

Abstract-Multiaccess mobile devices and overlapping wireless network deployments have emerged as a next generation network fixture. To make the most of all available networks, mobile devices should be capable of handing over between heterogeneous networks seamlessly and automatically. At the same time, operators should be able to steer network attachment based on their criteria. Although several cross layer mechanisms have been proposed in recent years, only the Media Independent Handover (MIH) Services framework has advanced in any of the established standardization bodies. This paper presents a blueprint for a GNU/Linux implementation of IEEE 802.21. We review the salient points of the standard, introduce our software implementation architecture, detail information gathering in GNU/Linux, and show how our prototype implementation can be used in practice. In contrast with prior published work, this paper presents a real IEEE 802.21 implementation, not an abstracted or reduced MIH-like framework, tested and empirically evaluated over real heterogeneous networks

Opportunistic Localization Scheme Based on Linear Matrix Inequality

Enabling self-localization of mobile nodes is an important problem that has been widely studied in the literature. The general conclusions is that an accurate localization requires either sophisticated hardware (GPS, UWB, ultrasounds transceiver) or a dedicated infrastructure (GSM, WLAN). In this paper we tackle the problem from a different and rather new perspective: we investigate how localization performance can be improved by means of a cooperative and opportunistic data exchange among the nodes. We consider a target node, completely unaware of its own position, and a number of mobile nodes with some self-localization capabilities. When the opportunity occurs, the target node can exchange data with in-range mobile nodes. This opportunistic data exchange is then used by the target node to refine its position estimate by using a technique based on Linear Matrix Inequalities and barycentric algorithm. To investigate the performance of such an opportunistic localization algorithm, we define a simple mathematical model that describes the opportunistic interactions and, then, we run several computer simulations for analyzing the effect of the nodes duty-cycle and of the native self-localization error modeling considered. The results show that the opportunistic interactions can actually improve the self-localization accuracy of a strayed node in many different scenarios

Cryptanalysis of an Efficient Signcryption Scheme with Forward Secrecy Based on Elliptic Curve

The signcryption is a relatively new cryptographic technique that is supposed to fulfill the functionalities of encryption and digital signature in a single logical step. Several signcryption schemes are proposed throughout the years, each of them having its own problems and limitations. In this paper, the security of a recent signcryption scheme, i.e. Hwang et al.'s scheme is analyzed, and it is proved that it involves several security flaws and shortcomings. Several devastating attacks are also introduced to the mentioned scheme whereby it fails all the desired and essential security attributes of a signcryption scheme.Comment: 5 Pages, 2 Figure

An opportunistic indoors positioning scheme based on estimated positions

The localization requirements for mobile nodes in wireless (sensor) networks are increasing. However, most research works are based on range measurements between nodes which are often oversensitive to the measurement error. In this paper we propose a location estimation scheme based on moving nodes that opportunistically exchange known positions. The user couples a linear matrix inequality (LMI) method with a barycenter computation to estimate its position. Simulations have shown that the accuracy of the estimation increases when the number of known positions increases, the radio range decreases and the node speeds increase. The proposed method only depends on a maximum RSS threshold to take into account a known position, which makes it robust and easy to implement. To obtain an accuracy of 1 meter, a user may have to wait at the same position for 5 minutes, with 8 pedestrians moving within range on average

Group behavior impact on an opportunistic localization scheme

In this paper we tackled the localization problem from an opportunistic perspective, according to which a node can infer its own spatial position by exchanging data with passing by nodes, called peers. We consider an opportunistic localization algorithm based on the linear matrix inequality (LMI) method coupled with a weighted barycenter algorithm. This scheme has been previously analyzed in scenarios with random deployment of peers, proving its effectiveness. In this paper, we extend the analysis by considering more realistic mobility models for peer nodes. More specifically, we consider two mobility models, namely the Group Random Waypoint Mobility Model and the Group Random Pedestrian Mobility Model, which is an improvement of the first one. Hence, we analyze by simulation the opportunistic localization algorithm for both the models, in order to gain insights on the impact of nodes mobility pattern onto the localization performance. The simulation results show that the mobility model has non-negligible effect on the final localization error, though the performance of the opportunistic localization scheme remains acceptable in all the considered scenarios

LPKI - A Lightweight Public Key Infrastructure for the Mobile Environments

The non-repudiation as an essential requirement of many applications can be provided by the asymmetric key model. With the evolution of new applications such as mobile commerce, it is essential to provide secure and efficient solutions for the mobile environments. The traditional public key cryptography involves huge computational costs and is not so suitable for the resource-constrained platforms. The elliptic curve-based approaches as the newer solutions require certain considerations that are not taken into account in the traditional public key infrastructures. The main contribution of this paper is to introduce a Lightweight Public Key Infrastructure (LPKI) for the constrained platforms such as mobile phones. It takes advantages of elliptic curve cryptography and signcryption to decrease the computational costs and communication overheads, and adapting to the constraints. All the computational costs of required validations can be eliminated from end-entities by introduction of a validation authority to the introduced infrastructure and delegating validations to such a component. LPKI is so suitable for mobile environments and for applications such as mobile commerce where the security is the great concern.Comment: 6 Pages, 6 Figure

Towards a GNU/Linux IEEE 802.21 Implementation

Abstract-Multiaccess mobile devices and overlapping wireless network deployments have emerged as a next generation network fixture. To make the most of all available networks, mobile devices should be capable of handing over between heterogeneous networks seamlessly and automatically. At the same time, operators should be able to steer network attachment based on their criteria. Although several cross layer mechanisms have been proposed in recent years, only the Media Independent Handover (MIH) Services framework has advanced in any of the established standardization bodies. This paper presents a blueprint for a GNU/Linux implementation of IEEE 802.21. We review the salient points of the standard, introduce our software implementation architecture, detail information gathering in GNU/Linux, and show how our prototype implementation can be used in practice. In contrast with prior published work, this paper presents a real IEEE 802.21 implementation, not an abstracted or reduced MIH-like framework, tested and empirically evaluated over real heterogeneous networks

Performance Model for a Conservative Distributed Simulation Environment Using Null Messages to Avoid Deadlock

A conservative distributed simulation requires all logical processes (LPs) to follow the causality constraint requirement. This implies that all event-messages are processed in strictly timestamp order. Apart from the timestamp of each event generated by LPs, synchronization between all LPs is the second most important requirements. Finally, there must not be a deadlock in the distributed environment. A deadlock may occur when there is no events present in the queue of LP. In such case, to avoid deadlock, Chandy-Misra-Bryant presented an algorithm called Null Message Algorithm (NMA) [3]. These null messages are passed as an event-message to other LPs and it stored in one of queues of LPs. This null message indicates that till the time stamp of that null message, all other events in the queue which have lesser time stamp than null message’s time stamp are safe to process. It means that there won’t be any arrival of any events from that logical process until current simulation time is equal to the time stamp of the null message. With the time stamp of the null message, a Lookahead value is added to the time stamp of that null message. This Lookahead value can be measure on certain kind of parameters such as delay to transmit a message, propagation delay, etc. therefore, calculating value of Lookahead is the most important part as Lookahead value affects the performance of the conservative distributed event simulation. Proper value of Lookahead can reduce the number of null messages which decreases the traffic of the network. In this paper, we demonstrate some calculation on the Lookahead which shows the performance of the distributed event simulation

Comparative market analysis and economic simulation for Morocco of the parabolic trough and dish CSP technologies

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2014Nos últimos anos tem-se notado um rápido desenvolvimento, ainda que diferenciado das tecnologias de concentração solar CSP (concentradores parabólicos lineares e de Fresnel, discos parabólicos e torres de concentração solar). O objetivo desta Tese consiste em comparar a tecnologia parabólica linear com o disco parabólico e em analisar a viabilidade económica para um projeto em Marrocos. É apresentada uma análise geral da tecnologia e uma análise de mercado. Por fim é construída uma base de dados contendo as centrais atualmente existentes e planeadas em projetos para o futuro. A comparação dos dois mercados leva a concluir que os sistemas parabólicos lineares se encontram num estado muito mais avançado do que os sistemas baseados em discos parabólicos. Desenvolver uma análise de projeto para o disco parabólico não faria sentido, visto que não existem produtos comerciais para aplicações em larga escala, o que levaria à necessidade de fazer várias suposições para vários parâmetros-chave. Foi então desenvolvido uma análise de projeto para o sistema parabólico linear. Foram escolhidas as cidades com maior número de habitantes em Marrocos, para as quais se construiu uma base de dados de condições ambientais e recurso solar para, por fim, calcular a produção de eletricidade utilizando o programa SAM. Para dois dimensionamentos diferentes da central, adaptados a uma integração de CSP na rede elétrica de 5% e 20% respetivamente, foram calculados indicadores tais como o LCOE, a TIR e o VAL. Os melhores resultados foram obtidos para locais com maior recurso solar e com o dimensionamento adaptado a uma integração de 20% de CSP. A TIR foi estimada com 10.2% para Tânger e 9.9% para a zona de Salé, Rabat e Kenitra.Developments in the past years have differentiated CSP (concentrating solar power) technologies (parabolic trough, power tower, parabolic dish and linear Fresnel) in terms of matureness. The aim of this Thesis is to compare the parabolic trough technology with the parabolic dish and to evaluate the economic feasibility of a project in Morocco. A general survey of the technology is presented and a market analysis is carried out. Finally the currently running power plants and planned projects are brought together in a database and presented. After comparing the two technologies, it was clear that parabolic trough is in a much more mature state than the parabolic dish, in terms of market penetration. In fact, project analysis for the parabolic dish would not make sense as there are no commercial products for large scale and many assumptions would need to be made. Therefore a project analysis was developed only for the parabolic trough technology. For the location, the largest cities in Morocco were chosen, an ambient and solar database was created and the annual electricity generation was calculated using the program SAM. Indicators such as the LCOE, IRR and NPV were calculated for two different power plant designs, one adapted for 5% of CSP integration in the grid and one for 20% of CSP integration. Locations with higher solar resource and 20% of CSP integration have the best results. For the IRR 10.2% is estimated for Tangier and 9.9% for the area of Salé Rabat and Kenitra. Estimated net present values are 3.7 M€ for Tangier and 0.7 M€ for Sale, Rabat and Kenitra