A Charging and Rewarding Scheme for Packet Forwarding

In multi-hop cellular networks, data packets have to be relayed hop by hop from a given mobile station to a base station and vice-versa. This means that the mobile stations must accept to forward information for the benefit of other stations. In this paper, we propose an incentive mechanism that is based on a charging/rewarding scheme and that makes collaboration rational for selfish nodes. We base our solution on symmetric cryptography to cope with the limited resources of the mobile stations. We provide a set of protocols and study their robustness with respect to various attacks. By leveraging on the relative stability of the routes, our solution leads to a very moderate overhead

Node Cooperation in Hybrid Ad hoc Networks

A hybrid ad hoc network is a structure-based network that is extended using multi-hop communications. Indeed, in this kind of network, the existence of a communication link between the mobile station and the base station is not required: A mobile station that has no direct connection with a base station can use other mobile stations as relays. Compared with conventional (single-hop) structure-based networks, this new generation can lead to a better use of the available spectrum and to a reduction of infrastructure costs. However, these benefits would vanish if the mobile nodes did not properly cooperate and forward packets for other nodes. In this paper, we propose a charging and rewarding scheme to encourage the most fundamental operation, namely packet forwarding. We use ``MAC layering" to reduce the space overhead in the packets and a stream cipher encryption mechanism to provide ``implicit authentication" of the nodes involved in the communication. We analyze the robustness of our protocols against rational and malicious attacks. We show that - using our solution - collaboration is rational for selfish nodes. We also show that our protocols thwart rational attacks and detect malicious attacks

ubiSOAP: A Service Oriented Middleware for Ubiquitous Networking

International audienceThe computing and networking capacities of today's wireless portable devices allow for ubiquitous services, which are seamlessly networked. Indeed, wireless handheld devices now embed the necessary resources to act as both service clients and providers. However, the ubiquitous networking of services remains challenged by the inherent mobility and resource constraints of the devices, which make services a priori highly volatile. This paper discusses the design, implementation and experimentation of the ubiSOAP service-oriented middleware, which leverages wireless networking capacities to effectively enable the ubiquitous networking of services. ubiSOAP specifically defines a layered communication middleware that underlies standard SOAP-based middleware, hence supporting legacy Web Services while exploiting nowadays ubiquitous connectivity

Cooperation in Multi-hop Cellular Networks

Naouel Ben Salem, Levente Buttyan, Jean-Pierre Hubaux and Markus Jakobsson abstract: In multi-hop cellular networks, the existence of a communication link between the mobile station and the base station is not required: a mobile station that has no direct connection with a base station can use other mobile stations as relays. Compared with conventional (single-hop) cellular networks, this new generation can lead to a better usage of the available spectrum and to a reduction of infrastructure costs. However, these benefits would vanish if the mobile nodes did not properly cooperate and forward packets for other nodes. In this paper, we propose a charging and rewarding scheme to encourage the most fundamental operation, namely packet forwarding. We analyse the robustness of our protocols against rational and malicious attacks. We show that our protocols thwart rational attacks and detect malicious attacks. We also show that our solution makes collaboration rational for selfish nodes

Joint Synchronization, Routing and Energy Saving in Multi-hop Hybrid Networks

Multi-hop hybrid networks can help providing both high bandwidth and broad coverage for wireless data networks. We focus on CSMA/CA-based networks and take IEEE 802.11 as a concrete example. We show that the three fundamental operations of synchronization, routing and energy saving can be implemented in an integrated way. Our integrated solution is based on the periodic computation of a broadcast tree among the nodes reporting to the same Access Point, starting from the Access Point itself. We use the nodes that are tree vertices as relays for both data and control packets. We propose a distributed neighbor discovery protocol and a simple centralized algorithm for computing the broadcast tree. Our analysis and simulation results show that the proposed solution has low protocol overhead in terms of message passing and execution time, and performs well even if nodes are mobile

Design and implementation of a cognitive node for heterogeneous wireless ad-hoc

In this thesis, the design of a cognitive network layer solution for a scenario with mobile devices is presented. Cognitive networks are able to sense the environment and adapt in order to find the best performance of the network at any moment. The final objective is to carry out a design of a node of the network which has incorporated in it up to three different technologies, which are WLAN, Bluetooth and ZigBee. The node is able to determine whether a technology should be used or not based on the network state. In order to find out the network state, a routing protocol based on Link State to provide the full view of the network is designed. Adaptive routing metrics have been designed in order to determine the best performance of the network to meet the QoS requirements considering what service is being required by the application and therefore to choose what technology is more appropriated for the connection. Those metrics are based on the capacity of the link, which takes into account the technology, the delay and the packet error rate of itself, and the utilization level. Then, Dijkstras’ algorithm is computed to solve the routing problem based on the adaptive weights instead of using the traditional hop-based count as a cost function. Furthermore, a heterogeneous cognitive wireless ad-hoc network testbed is implemented to analyze the behavior of the cognitive network when different types of services are used. On top of the cognitive network layer, an application to arrange meetings is implemented. Meeting rooms offer two different type of service for the guests, video and data service. Thus, clients are able to configure a video conference with the meeting room in case they cannot attend the meeting

Secure Incentives to Cooperate for Wireless Networks

The operating principle of certain wireless networks makes essential the cooperation between the mobile nodes. However, if each node is an autonomous selfish entity, cooperation is not guaranteed and therefore we need to use incentive techniques. In this thesis, we study cooperation in three different types of networks: WiFi networks, Wireless Mesh Networks (WMNs), and Hybrid Ad-hoc networks. Cooperation has a different goal for each of these networks, we thus propose incentive mechanisms adapted to each case. In the first chapter of this thesis, we consider WiFi networks whose wide-scale adoption is impeded by two major hurdles: the lack of a seamless roaming scheme and the variable QoS experienced by the users. We devise a reputation-based solution that (i) allows a mobile node to connect to a foreign Wireless ISP in a secure way while preserving his anonymity and (ii) encourages the WISPs to cooperate, i.e., to provide the mobile clients with a good QoS. Cooperation appears here twofold: First, the mobile clients have to collaborate in order to build and maintain the reputation system and second, the use of this reputation system encourages the WISPs to cooperate. We show, by means of simulations, that our reputation model indeed encourages the WISPs to behave correctly and we analyze the robustness of our solution against various attacks. In the second chapter of the thesis, we consider Wireless Mesh Networks (WMNs), a new and promising paradigm that uses multi-hop communications to extend WiFi networks. Indeed, by connecting only one hot spot to the Internet and by deploying several Transit Access Points (TAPs), a WISP can extend its coverage and serve a large number of clients at a very low cost. We analyze the characteristics of WMNs and deduce three fundamental network operations that need to be secured: (i) the routing protocol, (ii) the detection of corrupt TAPs and (iii) the enforcement of a proper fairness metric in WMNs. We focus on the fairness problem and propose FAME, an adaptive max-min fair resource allocation mechanism for WMNs. FAME provides a fair, collision-free capacity use of the WMN and automatically adjusts to the traffic demand fluctuations of the mobile clients. We develop the foundations of the mechanism and demonstrate its efficiency by means of simulations. We also experimentally assess the utility of our solution when TAPs are equipped with directional antennas and distinct sending and receiving interfaces in the Magnets testbed deployed in Berlin. In the third and last chapter of this thesis, we consider Hybrid Ad-hoc networks, i.e., infrastructured networks that are extended using multi-hop communications. We propose a secure set of protocols to encourage the most fundamental operation in these networks, namely packet forwarding. This solution is based on a charging and rewarding system. We use "MAC layering" to reduce the space overhead in the packets and a stream cipher encryption mechanism to provide "implicit authentication" of the nodes involved in the communication. We analyze the robustness of our protocols against rational and malicious attacks. We show that the use of our solution makes cooperation rational for selfish nodes. We also show that our protocols thwart rational attacks and detect malicious attacks

Estimação de Qualidade de Enlace e Alocação Dinâmica de Canais em Redes de Sensores sem Fio Industriais

O uso de Redes de Sensores sem Fio Industriais (RSSFIs) para implementar aplicações de monitoramento ou controle apresenta vantagens em comparação ao uso de redes cabeadas, como a maior flexibilidade e o menor custo de implantação. No entanto, é necessário lidar com problemas típicos das redes sem fio, como interferência e o alto nível de atenuação em pequena e larga escala. Além disso, as características do canal sem fio variam com o tempo e uma RSSFI deve ser capaz de se adaptar a essas variações para manter boa qualidade de serviço durante sua operação. Estratégias adaptativas, como a alocação dinâmica de canais, permitem lidar com os problemas mencionados. Para isso, o primeiro passo é estimar a qualidade dos enlaces, de modo que os nós da rede possam decidir se uma mudança de canal é necessária. Esta tese apresenta como contribuição um novo estimador de qualidade de enlace (LQE) e um novo tipo de nó, o nó LQE, que estima a qualidade dos enlaces em tempo real, usando informações obtidas a partir do transceptor, e informações extraídas de pacotes de dados recebidos. O estimador proposto considera problemas causados pelo perfil de multipercurso do ambiente na qualidade do canal,interferência e assimetria. Um protótipo foi desenvolvido e a solução foi validada por meio de experimentos em um ambiente industrial real. Diferente de outros LQEs encontrados na literatura, a solução proposta não gera tráfego extra na rede e não causa sobrecarga nos nós finais. Com base no LQE proposto, um novo protocolo de acesso ao meio foi desenvolvido. O protocolo usa adaptação de canal para a transmissão de pacotes de dados e salto em frequência para a transmissão de pacotes em broadcast. A taxa de recepção de pacote média na camada de aplicação permaneceu perto do pico para todos os cenários avaliados com o protocolo proposto, mesmo considerando as variações na qualidade dos canais ao longo do tempo. Os resultados indicam que o protocolo proposto apresenta desempenho superior aos protocolos de acesso ao meio definidos pelos padrões para RSSFI, em termos de confiabilidade e determinismo. Vários resultados experimentais obtidos em ambientes industriais também são descritos e é proposto um novo modelo para simulação de protocolos multicanais. O modelo é capaz de capturar os efeitos de atenuação por multipercurso, sombreamento, assimetria, as características não estacionárias do canal sem fio e a descorrelação entre diferentes canais.Industrial Wireless Sensor Networks (IWSNs), that is used to implement monitoring and control applications, presents certain advantages when compared to wired networks, including higher flexibility and lower deployment costs. However, it is necessary to deal with typical problems of wireless networks, such as interference and a high attenuation, in small and large scale. In addition, the characteristics of the wireless channel may change over time, and an IWSN needs to self adapt to these variations to maintain a good quality of service during its operation. Adaptive mechanisms, such as, dynamic channel allocation, are used to deal with the aforementioned problems. For this, the first step is to estimate the link quality, so that the network nodes can decide if a channel change is needed. This thesis presents as a contribution a novel Link Quality Estimator (LQE), and a new type of node, the LQE node, that estimates the quality of the links in real-time, using information obtained from the transceiver, and information obtained from received data packets. The proposed LQE deals with the problems caused by the multipath profile of the environment in channel quality, interference and asymmetry. A prototype was developed and the LQE was validated by experiments in an actual industrial environment. Different from other LQEs in the literature, the solution proposed in this thesis does not cause overhead at the end-nodes and on the network. Based on the proposed LQE, a novel MAC protocol was developed. The protocol uses channel adaptation for the transmission of unicast data packets, and frequency hopping for the transmission of broadcast packets. The packet reception rate at the application layer was at the peak for all scenarios that were evaluated using the proposed protocol, even considering the variations in channel quality over time. The results indicate that the proposed protocol presents a better performance in comparison to the MAC protocols defined by the standards for IWSN, in terms of reliability and determinism. Several experimental results obtained in industrial environments are also described, and a new model for simulation of multi-channel protocols is proposed. The model includes the effects of multipath fading, shadowing, asymmetry, the non-stationary characteristics of the channel, and the uncorrelation of the different channels