Controlled Mobility in Mobile Sensor Networks: Advantages, Issues and Challenges

International audienceRecently, wireless self-organizing networks are attracting a lot of interest in the research community. Moreover, in the last decade many mobile devices have appeared in the market. Exploiting mobility in a wireless environment, instead of considering it as a kind of disturbance, is a fundamental concept that the research community is beginning to appreciate now. Of course, the advantages obtainable through the use of the mobility imply the knowledge of the different types of mobility and the way to include it in the management architecture of the wireless networks. In this work we claim that mobility and wireless sensor networks can be considered as two synergetic elements of the same reality. For this purpose, we sketch a macro-classification of the different objectives which can be pursued by controlled mobility. Moreover, we identify and highlight the interactions between this specific type of mobility and the layers of the control stack. Lastly, this paper reports a case study in which we show how controlled mobility can be exploited practically

Data delivery in fragmented wireless sensor networks using mobile agents

In the past few years, research in Wireless Sensor Networks (WSN) has grown at an unprecented rate. This is due to the large number of potential applications and environments WSNs can be used in. Nodes in WSNs communicate in multihop fashion to deliver the sensory information to a central processing unit, such as a base station or a sink node. This form of communication requires a degree of network connectivity which might not be always achievable, either due to the sensor deployment strategy, or due to sensor node failure, which can be malicious, or otherwise. In this thesis, we study the problem of data delivery in disconnected WSNs. A special class of disconnected sensor networks called Fragmented wireless sensor networks (FWSN) is considered. A FWSN consists of several groups of connected sensor nodes that we call fragments . We propose a mobility based approach that exploits resource rich, in terms of power and buffer size, mobile agents that move in the network and operate as data relays between fragments to eventually deliver data to the base station. The movement of the mobile nodes and their role as relay stations is modeled using a closed queueing network approach, which is used to obtain steady state results. Building on these results, we derive the distributions of the fragment-to-fragment and fragment-to-sink delays. The results show that this model accurately captures the system behavior. Using the same model, the effect of the movement policy, the number and speed of mobile relays, and the service time at each fragment on the end-to-end delay has also been studied. The proposed queueing model can also be used to model other roles of the mobile nodes, including their roles as either data collectors or data sinks. We also study some practical issues, including mobility control in large networks and engineering the service time, i.e., the time that an MR spend in relaying data between fragments

Stochastic event capture using mobile sensors subject to a quality metric

Mobile sensors cover more area over a period of time than the same number of stationary sensors. However, the quality of coverage achieved by mobile sensors depends on the velocity, mobility pattern, number of mobile sensors deployed and the dynamics of the phenomenon being sensed. The gains attained by mobile sensors over static sensors and the optimal motion strategies for mobile sensors are not well understood. In this paper we consider the problem of event capture using mobile sensors. The events of interest arrive at certain points in the sensor field and fade away according to arrival and departure time distributions. An event is said to be captured if it is sensed by one of the mobile sensors before it fades away. For this scenario we analyze how the quality of coverage scales with the velocity, path and number of mobile sensors. We characterize the cases where the deployment of mobile sensors ha

Service Provisioning in Mobile Networks Through Distributed Coordinated Resource Management

The pervasiveness of personal computing platforms offers an unprecedented opportunity to deploy large-scale services that are distributed over wide physical spaces. Two major challenges face the deployment of such services: the often resource-limited nature of these platforms, and the necessity of preserving the autonomy of the owner of these devices. These challenges preclude using centralized control and preclude considering services that are subject to performance guarantees. To that end, this thesis advances a number of new distributed resource management techniques that are shown to be effective in such settings, focusing on two application domains: distributed Field Monitoring Applications (FMAs), and Message Delivery Applications (MDAs). In the context of FMA, this thesis presents two techniques that are well-suited to the fairly limited storage and power resources of autonomously mobile sensor nodes. The first technique relies on amorphous placement of sensory data through the use of novel storage management and sample diffusion techniques. The second approach relies on an information-theoretic framework to optimize local resource management decisions. Both approaches are proactive in that they aim to provide nodes with a view of the monitored field that reflects the characteristics of queries over that field, enabling them to handle more queries locally, and thus reduce communication overheads. Then, this thesis recognizes node mobility as a resource to be leveraged, and in that respect proposes novel mobility coordination techniques for FMAs and MDAs. Assuming that node mobility is governed by a spatio-temporal schedule featuring some slack, this thesis presents novel algorithms of various computational complexities to orchestrate the use of this slack to improve the performance of supported applications. The findings in this thesis, which are supported by analysis and extensive simulations, highlight the importance of two general design principles for distributed systems. First, a-priori knowledge (e.g., about the target phenomena of FMAs and/or the workload of either FMAs or DMAs) could be used effectively for local resource management. Second, judicious leverage and coordination of node mobility could lead to significant performance gains for distributed applications deployed over resource-impoverished infrastructures