7. GI/ITG KuVS Fachgespräch Drahtlose Sensornetze

In dem vorliegenden Tagungsband sind die Beiträge des Fachgesprächs Drahtlose Sensornetze 2008 zusammengefasst. Ziel dieses Fachgesprächs ist es, Wissenschaftlerinnen und Wissenschaftler aus diesem Gebiet die Möglichkeit zu einem informellen Austausch zu geben – wobei immer auch Teilnehmer aus der Industrieforschung willkommen sind, die auch in diesem Jahr wieder teilnehmen.Das Fachgespräch ist eine betont informelle Veranstaltung der GI/ITG-Fachgruppe „Kommunikation und Verteilte Systeme“ (www.kuvs.de). Es ist ausdrücklich keine weitere Konferenz mit ihrem großen Overhead und der Anforderung, fertige und möglichst „wasserdichte“ Ergebnisse zu präsentieren, sondern es dient auch ganz explizit dazu, mit Neueinsteigern auf der Suche nach ihrem Thema zu diskutieren und herauszufinden, wo die Herausforderungen an die zukünftige Forschung überhaupt liegen.Das Fachgespräch Drahtlose Sensornetze 2008 findet in Berlin statt, in den Räumen der Freien Universität Berlin, aber in Kooperation mit der ScatterWeb GmbH. Auch dies ein Novum, es zeigt, dass das Fachgespräch doch deutlich mehr als nur ein nettes Beisammensein unter einem Motto ist.Für die Organisation des Rahmens und der Abendveranstaltung gebührt Dank den beiden Mitgliedern im Organisationskomitee, Kirsten Terfloth und Georg Wittenburg, aber auch Stefanie Bahe, welche die redaktionelle Betreuung des Tagungsbands übernommen hat, vielen anderen Mitgliedern der AG Technische Informatik der FU Berlin und natürlich auch ihrem Leiter, Prof. Jochen Schiller

Contribution to the design of VANET routing protocols for realistic urban environments

One of the main concerns of the cities' administration is mobility management. In Intelligent Transportation Systems (ITS), pedestrians, vehicles and public transportation systems could share information and react to any situation in the city. The information sensed by vehicles could be useful for other vehicles and for the mobility authorities. Vehicular Ad hoc Networks (VANETs) make possible the communication between vehicles (V2I) and also between vehicles and fixed infrastructure (V2I) managed by the city's authorities. In addition, VANET routing protocols minimize the use of fixed infrastructure since they employ multi-hop V2V communication to reach reporting access points of the city. This thesis aims to contribute in the design of VANET routing protocols to enable reporting services (e.g., vehicular traffic notifications) in urban environments. The first step to achieve this global objective has been the study of components and tools to mimic a realistic VANET scenario. Moreover, we have analyzed the impact of the realism of each one of those components in the simulation results. Then, we have improved the Address Resolution procedure in VANETs by including it in the routing signaling messages. Our approach simplifies the VANET operation and increases the packet delivery ratio as consequence. Afterwards, we have tackled the issue of having duplicate packets in unicast communications and we have proposed routing filters to lower their presence. This way we have been able to increase the available bandwidth and reduce the average packet delay with a slight increase of the packet losses. Besides, we have proposed a Multi-Metric Map aware routing protocol (MMMR) that incorporates four routing metrics (distance, trajectory, vehicle density and available bandwidth) to take the forwarding decisions. With the aim of increasing the number of delivered packets in MMMR, we have developed a Geographical Heuristic Routing (GHR) algorithm. GHR integrates Tabu and Simulated Annealing heuristic optimization techniques to adapt its behavior to the specific scenario characteristics. GHR is generic because it could use any geographical routing protocol to take the forwarding decisions. Additionally, we have designed an easy to implement forwarding strategy based on an extended topology information area of two hops, called 2-hops Geographical Anycast Routing (2hGAR) protocol. Results show that controlled randomness introduced by GHR improves the default operation of MMMR. On the other hand, 2hGAR presents lower delays than GHR and higher packet delivery ratio, especially in high density scenarios. Finally, we have proposed two mixed (integer and linear) optimization models to detect the best positions in the city to locate the Road Side Units (RSUs) which are in charge of gathering all the reporting information generated by vehicles.Una de las principales preocupaciones en la administración de las ciudades es la gestión de la movilidad de sus vehículos, debido a los problemas de tráfico como atascos y accidentes. En los sistemas inteligentes de transporte (SIT), peatones, vehículos y transporte público podrán compartir información y adaptarse a cualquier situación que suceda en la ciudad. La información obtenida por los sensores de los vehículos puede ser útil para otros vehículos y para las autoridades de movilidad. Las redes ad hoc vehiculares (VANETs) hacen posible la comunicación entre los propios vehículos (V2V) y entre vehículos y la infraestructura fija de la red de la ciudad (V2I). Asimismo, los protocolos de encaminamiento para redes vehiculares minimizan el uso de infraestructura fija de red, ya que los protocolos de encaminamiento VANET emplean comunicaciones multisalto entre vehículos para encaminar los mensajes hasta los puntos de acceso de la red en la ciudad. El objetivo de esta tesis doctoral es contribuir en el diseño de protocolos de encaminamiento en redes ad hoc vehiculares para servicios de notificaciones (p.ej. reportes del estado del tráfico) en entornos urbanos. El primer paso para alcanzar este objetivo general ha sido el estudio de componentes y herramientas para simular un escenario realista de red ad hoc vehicular. Además, se ha analizado el impacto del nivel de realismo de cada uno de los componentes de simulación en los resultados obtenidos. Así también, se ha propuesto un mecanismo de resolución de direcciones automático y coherente para redes VANET a través del uso de los propios mensajes de señalización de los protocolos de encaminamiento. Esta mejora simplifica la operación de una red ad hoc vehicular y como consecuencia aumenta la tasa de recepción de paquetes. A continuación, se ha abordado el problema de la aparición inesperada de paquetes de datos duplicados en una comunicación punto a punto. Para ello, se ha propuesto el filtrado de paquetes duplicados a nivel del protocolo de encaminamiento. Esto ha producido un incremento del ancho disponible en el canal y una reducción del retardo medio en la trasmisión de un paquete, a costa de un mínimo aumento de la pérdida de paquetes. Por otra parte, hemos propuesto un protocolo de encaminamiento multi-métrica MMMR (Multi-Metric Map-aware Routing protocol), el cual incorpora cuatro métricas (distancia al destino, trayectoria, densidad de vehículos y ancho de banda) en las decisiones de encaminamiento. Con el objetivo de aumentar la tasa de entrega de paquetes en MMMR, hemos desarrollado un algoritmo heurístico de encaminamiento geográfico denominado GHR (Geographical Heuristic Routing). Esta propuesta integra las técnicas de optimización Tabu y Simulated Annealing, que permiten a GHR adaptarse a las características específicas del escenario. Adicionalmente, hemos propuesto 2hGAR (2-hops Geographical Anycast Routing), un protocolo de encaminamiento anycast que emplea información de la topología de red a dos saltos de distancia para tomar la decisión de encaminamiento de los mensajes. Los resultados muestran que la aleatoriedad controlada de GHR en su operación mejora el rendimiento de MMMR. Asimismo, 2hGAR presenta retardos de paquete menores a los obtenidos por GHR y una mayor tasa de paquetes entregados, especialmente en escenarios con alta densidad de vehículos. Finalmente, se han propuesto dos modelos de optimización mixtos (enteros y lineales) para detectar los mejores lugares de la ciudad donde ubicar los puntos de acceso de la red, los cuales se encargan de recolectar los reportes generados por los vehículos.Postprint (published version

Interference and power control in ad hoc wireless networks

This thesis looks at the problem of interference when Power Control is applied to maximize the network capacity. In ad hoc networks, the RTS/CTS dialog or virtual carrier sensing is less effective since a transmission takes place over three ranges: interference range, carrier sense range and transmission range. The values of interference range do not interrupt a transmission if it is close to noise floor, however the carrier sense range is capable of disrupting a transmission. Location, packet size and the traffic must be considered as important parameters in power control protocols. The majority of the work is focused at the physical and link layers

AN ADAPTIVE INFORMATION DISSEMINATION MODEL FOR VANET COMMUNICATION

Vehicular ad hoc networks (VANETs) have been envisioned to be useful in road safety and many commercial applications. The growing trend to provide communication among the vehicles on the road has provided the opportunities for developing a variety of applications for VANET. The unique characteristics of VANET bring about new research challenges

Adaptação da taxa de transmissão em redes veiculares

Mestrado em Engenharia Eletrónica e TelecomunicaçõesAo longo dos últimos anos, vários progressos em comunicações sem fios têm extendido investigações a novas áreas, onde soluções baseadas em redes com fios são impraticáveis. Neste contexto apareceram as Vehicular Ad hoc NETworks (VANETs), uma classe emergente das redes Ad Hoc, para interligação e comunicação entre veículos. Devido ás suas características peculiares como alta mobilidade, topologia dinâmica, frequente perda de conectividade, as VANETs enfrentam vários desafios para definir protolocos e mecanismos fiáveis, como a adaptação da taxa de transmissão. De facto, a monitorização do tráfego das ruas através de aplicações são o núcleo das VANETs cujo desempenho depende da taxa de envio de pacotes e da taxa de sucesso que estas redes conseguem oferecer. Mecanismos de adaptação da taxa de transmissão têm como objetivo evitar a degradação do desempenho da rede devido a uma escolha muito elevada da taxa de transmissão, quando a qualidade do canal está deteorada, ou devido à utilização de uma taxa muito baixa quando as condições da qualidade do canal melhoram. Uma vez que os dispositivos que operam segundo a norma IEEE 802.11p suportam várias taxas de transmissão, é importante que estes possam adaptar a taxa de forma dinâmica de modo a obter um desempenho elevado. Assim é essencial ter um mecanismo de adaptação da taxa de transmissão que seja robusto e capaz de lidar com elevadas flutuações e assimetrias do canal, transmissões em rajada e de duração inconstante, e perda de pacotes devido ás condições do meio e à existência de terminais escondidos. Assim sendo, esta dissertação permite avaliar e comparar os mecanismos existentes para redes sem fios, em ambientes veiculares usando o Network Simulator 3 (NS-3) e o Simulator of Urban Mobility (SUMO). Depois de analisar os principais mecanismos presentes na literatura, foram selecionados quatro para serem testados: Adaptive Auto Rate Fall Back-Collision Detection (AARF-CD), Collision-Aware Rate Adaptation (CARA), Minstrel e o Ideal. Serão considerados dois tipos de cenários: auto-estrada e urbano. A comparação dos algoritmos será baseada em métricas conhecidas como a taxa de envio de pacotes, taxa de sucesso e a percentagem de retransmissões para vários níveis de transmissão. Os resultados experimentais mostraram que o AARFCD atingiu um desempenho superior, quando comparado com os restantes algoritmos. O CARA foi o segundo melhor algoritmo segundo as métricas consideradas. De realçar que o AARF-CD obteve uma taxa de sucesso superior ao do CARA, apesar deste oferecer uma taxa de envio de pacotes superior em certos cenários. Em relação ao atraso na rede, tanto o AARFCD como o CARA alcançaram resultados similares. Foi também concluído que algoritmos com diferenciação de perdas de pacotes como o AARF-CD e o CARA oferecem uma melhor adaptação da taxa de transmissão. Por fim, é sugerido um algoritmo de adatação da taxa de transmissão que tem em conta parâmetros externos, como a velocidade, distância e a densidade de veículos. Cada parâmetro é considerado de acordo com a sua influência na transmissão de dados através de pesos. Desta forma os parâmetros que afetam mais a adaptação da taxa de transmissão serão associados a pesos maiores. A adaptação da taxa de transmissão será baseada num processo de pesos, de acordo com o efeito das condições exteriores no desempenho da rede.Over the last years, several progresses in wireless communications have extended research in new sub-areas, where wired solutions are impracticable. In this context, VANETs arose as an emerging area of wireless ad hoc networks, which connect and allow communication between vehicles. Due to its peculiar characteristics such as high mobility, dynamic topology and frequent loss of connectivity, VANETs face many challenges to de ne reliable protocols and mechanisms like rate adaptation schemes. Indeed tra c querying and road sensing applications are the core of VANETs whose performance depends on the throughput and the success ratio these networks can provide. Rate adaptation mechanisms aim to avoid performance network degradation due to rate over-selection when channel quality is deteriorated or rate under-selection when channel quality improves. Since IEEE 802.11p supports multi-rate capabilities, devices must adapt their transmission rate dynamically in order to achieve a high performance. Thus it is critical to have a robust rate adaptation mechanism that can deal with high uctuation and asymmetry of channels, bursty and infrequent duration transmissions, and loss packet own to the extreme environment conditions or hidden terminals. Thereby, this dissertation evaluates and compares the existing rate adaptation mechanisms for wireless in vehicular environments, using NS-3 and SUMO. Four mechanisms: AARF-CD, CARA, Minstrel and Ideal were selected to be compared, after analysing the main mechanisms across literature. It will be considered two types of scenarios: highway and urban scenario. The comparison between the algorithms will be based on known metrics: network throughput, success ratio, delay and percentage of retransmissions. Experimentation results showed that AARF-CD achieved higher performance when compared with the remaining algorithms in both scenarios. CARA was the second best algorithm, considering the same metrics. Although CARA provides higher throughput in certain scenarios, it is outperformed by AARF-CD in terms of rate success. Regarding delay, AARF-CD and CARA attained similar results. It was also concluded that algorithms with loss di erentiation such as AARF-CD and CARA provide better rate adaptation. Finally, it is suggested a rate adaptation algorithm which considers external parameters like velocity, distance and density of nodes. Each parameter is considered according to its impact in the data transmission through weights. Parameters that a ect more the rate adaptation are associated to larger weights. Thus, the rate adaptation is based on a weighted process according to the e ect of external conditions in the network performance

Security protocols suite for machine-to-machine systems

Nowadays, the great diffusion of advanced devices, such as smart-phones, has shown that there is a growing trend to rely on new technologies to generate and/or support progress; the society is clearly ready to trust on next-generation communication systems to face today’s concerns on economic and social fields. The reason for this sociological change is represented by the fact that the technologies have been open to all users, even if the latter do not necessarily have a specific knowledge in this field, and therefore the introduction of new user-friendly applications has now appeared as a business opportunity and a key factor to increase the general cohesion among all citizens. Within the actors of this technological evolution, wireless machine-to-machine (M2M) networks are becoming of great importance. These wireless networks are made up of interconnected low-power devices that are able to provide a great variety of services with little or even no user intervention. Examples of these services can be fleet management, fire detection, utilities consumption (water and energy distribution, etc.) or patients monitoring. However, since any arising technology goes together with its security threats, which have to be faced, further studies are necessary to secure wireless M2M technology. In this context, main threats are those related to attacks to the services availability and to the privacy of both the subscribers’ and the services providers’ data. Taking into account the often limited resources of the M2M devices at the hardware level, ensuring the availability and privacy requirements in the range of M2M applications while minimizing the waste of valuable resources is even more challenging. Based on the above facts, this Ph. D. thesis is aimed at providing efficient security solutions for wireless M2M networks that effectively reduce energy consumption of the network while not affecting the overall security services of the system. With this goal, we first propose a coherent taxonomy of M2M network that allows us to identify which security topics deserve special attention and which entities or specific services are particularly threatened. Second, we define an efficient, secure-data aggregation scheme that is able to increase the network lifetime by optimizing the energy consumption of the devices. Third, we propose a novel physical authenticator or frame checker that minimizes the communication costs in wireless channels and that successfully faces exhaustion attacks. Fourth, we study specific aspects of typical key management schemes to provide a novel protocol which ensures the distribution of secret keys for all the cryptographic methods used in this system. Fifth, we describe the collaboration with the WAVE2M community in order to define a proper frame format actually able to support the necessary security services, including the ones that we have already proposed; WAVE2M was funded to promote the global use of an emerging wireless communication technology for ultra-low and long-range services. And finally sixth, we provide with an accurate analysis of privacy solutions that actually fit M2M-networks services’ requirements. All the analyses along this thesis are corroborated by simulations that confirm significant improvements in terms of efficiency while supporting the necessary security requirements for M2M networks

Delay tolerant networking in a shopping mall environment

The increasing popularity of computing devices with short-range wireless offers new communication service opportunities. These devices are small and may be mobile or embedded in almost any type of object imaginable, including cars, tools, appliances, clothing and various consumer goods. The majority of them can store data and transmit it when a wireless, or wired, transmitting medium is available. The mobility of the individuals carrying such short-range wireless devices is important because varying distances creates connection opportunities and disconnections. It is likely that successful forwarding algorithms will be based, at least in part, on the patterns of mobility that are seen in real settings. For this reason, studying human mobility in different environments for extended periods of time is essential. Thus we need to use measurements from realistic settings to drive the development and evaluation of appropriate forwarding algorithms. Recently, several significant efforts have been made to collect data reflecting human mobility. However, these traces are from specific scenarios and their validity is difficult to generalize. In this thesis we contribute to this effort by studying human mobility in shopping malls. We ran a field trial to collect real-world Bluetooth contact data from shop employees and clerks in a shopping mall over six days. This data will allow the informed design of forwarding policies and algorithms for such settings and scenarios, and determine the effects of users' mobility patterns on the prevalence of networking opportunities. Using this data set we have analysed human mobility and interaction patterns in this shopping mall environment. We present evidence of distinct classes of mobility in this situation and characterize them in terms of power law coefficients which approximate inter-contact time distributions. These results are quite different from previous studies in other environments. We have developed a software tool which implements a mobility model for "structured" scenarios such as shopping malls, trade fairs, music festivals, stadiums and museums. In this thesis we define as structured environment, a scenario having definite and highly organised structure, where people are organised by characteristic patterns of relationship and mobility. We analysed the contact traces collected on the field to guide the design of this mobility model. We show that our synthetic mobility model produces inter-contact time and contact duration distributions which approximate well to those of the real traces. Our scenario generator also implements several random mobility models. We compared our Shopping Mall mobility model to three other random mobility models by comparing the performances of two benchmark delay tolerant routing protocols, Epidemic and Prophet, when simulated with movement traces from each model. Thus, we demonstrate that the choice of a mobility model is a significant consideration when designing and evaluating delay-tolerant mobile ad-hoc network protocols. Finally, we have also conducted an initial study to evaluate the effect of delivering messages in shopping mall environments by exclusively forwarding them to customers or sellers, each of which has distinctive mobility patterns

LVMM: The Localized Vehicular Multicast Middleware - a Framework for Ad Hoc Inter-Vehicles Multicast Communications

This thesis defines a novel semantic for multicast in vehicular ad hoc networks (VANETs) and it defines a middleware, the Localized Vehicular Multicast Middleware (LVMM) that enables minimum cost, source-based multicast communications in VANETs. The middleware provides support to find vehicles suitable to sustain multicast communications, to maintain multicast groups, and to execute a multicast routing protocol, the Vehicular Multicast Routing Protocol (VMRP), that delivers messages of multicast applications to all the recipients utilizing a loop-free, minimum cost path from each source to all the recipients. LVMM does not require a vehicle to know all other members: only knowledge of directly reachable nodes is required to perform the source-based routing

Delay tolerant networking in a shopping mall environment

The increasing popularity of computing devices with short-range wireless offers new communication service opportunities. These devices are small and may be mobile or embedded in almost any type of object imaginable, including cars, tools, appliances, clothing and various consumer goods. The majority of them can store data and transmit it when a wireless, or wired, transmitting medium is available. The mobility of the individuals carrying such short-range wireless devices is important because varying distances creates connection opportunities and disconnections. It is likely that successful forwarding algorithms will be based, at least in part, on the patterns of mobility that are seen in real settings. For this reason, studying human mobility in different environments for extended periods of time is essential. Thus we need to use measurements from realistic settings to drive the development and evaluation of appropriate forwarding algorithms. Recently, several significant efforts have been made to collect data reflecting human mobility. However, these traces are from specific scenarios and their validity is difficult to generalize. In this thesis we contribute to this effort by studying human mobility in shopping malls. We ran a field trial to collect real-world Bluetooth contact data from shop employees and clerks in a shopping mall over six days. This data will allow the informed design of forwarding policies and algorithms for such settings and scenarios, and determine the effects of users' mobility patterns on the prevalence of networking opportunities. Using this data set we have analysed human mobility and interaction patterns in this shopping mall environment. We present evidence of distinct classes of mobility in this situation and characterize them in terms of power law coefficients which approximate inter-contact time distributions. These results are quite different from previous studies in other environments. We have developed a software tool which implements a mobility model for "structured" scenarios such as shopping malls, trade fairs, music festivals, stadiums and museums. In this thesis we define as structured environment, a scenario having definite and highly organised structure, where people are organised by characteristic patterns of relationship and mobility. We analysed the contact traces collected on the field to guide the design of this mobility model. We show that our synthetic mobility model produces inter-contact time and contact duration distributions which approximate well to those of the real traces. Our scenario generator also implements several random mobility models. We compared our Shopping Mall mobility model to three other random mobility models by comparing the performances of two benchmark delay tolerant routing protocols, Epidemic and Prophet, when simulated with movement traces from each model. Thus, we demonstrate that the choice of a mobility model is a significant consideration when designing and evaluating delay-tolerant mobile ad-hoc network protocols. Finally, we have also conducted an initial study to evaluate the effect of delivering messages in shopping mall environments by exclusively forwarding them to customers or sellers, each of which has distinctive mobility patterns