Sotiris E. Nikoletseas

Sink mobility protocols for data collection in wireless sensor networks

In wireless sensor networks data propagation is usually performed by sensors transmitting data towards a static control center (sink). Inspired by important applications (mostly related to ambient intelligence) and as a first step towards introducing mobility, we propose the idea of having a sink moving in the network area and collecting data from sensors. We propose four characteristic mobility patterns for the sink along with different data collection strategies. Through a detailed simulation study, we evaluate several important performance properties of each protocol. Our findings demonstrate that by taking advantage of the sinks mobility, we can significantly reduce the energy spent in relaying traffic and thus greatly extend the lifetime of the network.

Efficient data propagation strategies in wireless sensor networks using a single mobile sink

Data collection is usually performed in wireless sensor networks by the sensors relaying data towards a static control center (sink). Motivated by important applications (mostly related to ambient intelligence and remote monitoring) and as a first step towards introducing mobility, we propose the basic idea of having a sink moving in the network area and collecting data from sensors. We propose four characteristic mobility patterns for the sink that we combine with different data collection strategies. Through a detailed simulation study, we evaluate several important performance properties of each approach. Our findings demonstrate that by taking advantage of the sinks mobility and shifting work from sensors to the powerful sink, we can significantly reduce the energy spent in relaying traffic and thus greatly extend the lifetime of the network.

A new energy efficient and fault-tolerant protocol for data propagation in Smart Dust networks using varying transmission range

In this work we propose a new energy efficient and fault tolerant protocol for data propagation in wireless sensor networks, the variable transmission range protocol (VTRP). The basic idea of data propagation in VTRP is the varying range of data transmissions, i.e., we allow the transmission range to increase in various ways. Thus data propagation in our protocol exhibits high fault-tolerance (by bypassing obstacles or faulty sensors) and increases network lifetime (since critical sensors, i.e. close to the control center are not overused). As far as we know, it is the first time varying transmission range is used. We implement the protocol and perform an extensive experimental evaluation and comparison to a representative protocol (LTP) of several important performance measures with a focus on energy consumption. Our findings indeed demonstrate that our protocol achieves significant improvements in energy efficiency and network lifetime.

Smart dust protocols for local detection and propagation

Smart Dust is a set of a ast number of ultra-small fully autonomous computing and communication devices, with very restricted energy and computing capabilities, that cooperate to quickly and efficiently accomplish a large sensing task. Smart Dust can be very useful in practice i.e. in the local detection of a remote crucial event and the propagation of data reporting its realization. In this work we make an effort towards the research on smart dust from a basic algorithmic point of view. We first provide a simple but realistic model for smart dust and present an interesting problem, which is how to propagate efficiently information on an event detected locally. Then we present smart dust protocols for local detection and propagation that are simple enough to be implemented on real smart dust systems, and perform, under some simplifying assumptions, a rigorous average case analysis of their efficiency and energy consumption (and their interplay). This analysis leads to concrete results showing that our protocols are very efficient.

Distributed Circle Formation for Anonymous Oblivious Robots

This paper deals with systems of multiple mobile robots each of which observes the positions of the other robots and moves to a new position so that eventually the robots form a circle. In the model we study, the robots are anonymous and oblivious, in the sense that they cannot be distinguished by their appearance and do not have a common x-y coordinate system, while they are unable to remember past actions.

Full Length Article: Biased sink mobility with adaptive stop times for low latency data collection in sensor networks

Collecting sensory data using a mobile data sink has been shown to drastically reduce energy consumption at the cost of increasing delivery delay. Towards improved energy-latency trade-offs, we propose a biased, adaptive sink mobility scheme, that adjusts to local network conditions, such as the surrounding density, remaining energy and the number of past visits in each network region. The sink moves probabilistically, favoring less visited areas in order to cover the network area faster, while adaptively stopping more time in network regions that tend to produce more data. We implement and evaluate our mobility scheme via simulation in diverse network settings. Compared to known blind random, non-adaptive schemes, our method achieves significantly reduced latency, especially in networks with non-uniform sensor distribution, without compromising the energy efficiency and delivery success.

An Efficient Communication Strategy for Ad-hoc Mobile Networks

We investigate the problem of communication in an ad-hoc mobile network, that is, we assume the extreme case of a total absense of any fixed network infrastructure (for example a case of rapid deployment of a set of mobile hosts in an unknown terrain). We propose, in such a case, that a small subset of the deployed hosts (which we call the support) should be used for network operations. However, the vast majority of the hosts are moving arbitrarily according to application needs.We then provide a simple, correct and efficient protocol for communication that avoids message flooding. Our protocol manages to establish communication between any pair of mobile hosts in small, a-priori guaranteed expected time bounds even in the worst case of arbitrary motions of the hosts that not in the support (provided that they do not deliberately try to avoid the support). These time bounds, interestingly, do not depend, on the number of mobile hosts that do not belong in the support. They depend only on the size of the area of motions. Our protocol can be implemented in very efficient ways by exploiting knowledge of the space of motions or by adding more power to the hosts of the support.Our results exploit and further develop some fundamental properties of random walks in finite graphs.

A mobility aware protocol synthesis for efficient routing in ad hoc mobile networks

In mobile ad hoc networks (MANETs), the mobility of the nodes is a complicating factor that significantly affects the effectiveness and performance of the routing protocols. Our work builds upon recent results on the effect of node mobility on the performance of available routing strategies (i.e., path-based, using support) and proposes a protocol framework that exploits the usually different mobility rates of the nodes by adapting the routing strategy during execution. We introduce a metric for the relative mobility of the nodes, according to which the nodes are classified into mobility classes. These mobility classes determine, for any pair of origin and destination, the routing technique that best corresponds to their mobility properties. Moreover, special care is taken for nodes remaining almost stationary or moving with high (relative) speeds. Our key design goal is to limit the necessary implementation changes required to incorporate existing routing protocols into our framework. We provide extensive evaluation of the proposed framework, using a well-known simulator (NS2). Our first findings demonstrate that the proposed framework improves, in certain cases, the performance of existing routing protocols.

50 ways to build your application: A survey of middleware and systems for Wireless Sensor Networks

In this paper, we survey the current state-of-the-art in middleware and systems for Wireless Sensor Networks (WSN). We provide a discussion on the definition ofWSN middleware, design issues associated with it, and the taxonomies commonly used to categorize it. We also present a categorization of a number of such middleware platforms, using middleware functionalities and challenges which we think will play a crucial role in developing software for WSN in the near future. Finally, we provide a short discussion on WSN middleware trends.

Energy efficient protocols for sensing multiple events in Smart Dust networks

Wireless sensor networks are comprised of a vast number of ultra-small, autonomous computing and communication devices, with restricted energy, that cooperate to accomplish a large sensing task. In this work: a) we propose extended versions of two data propagation protocols for such networks: the sleep-awake probabilistic forwarding protocol (SW-PFR) and the hierarchical threshold sensitive energy efficient network protocol (H-TEEN). These non-trivial extensions improve the performance of the original protocols, by introducing sleep-awake periods in the PFR protocol to save energy, and introducing a hierarchy of clustering in the TEEN protocol to better cope with large networks; b) we implemented the two protocols and performed an extensive simulation comparison of various important measures of their performance with a focus on energy consumption; c) we investigate in detail the relative advantages and disadvantages of each protocol; and d) we discuss a possible hybrid combination of the two protocols towards optimizing certain goals.