Visualizations of Wireless Sensor Network Data

Wireless sensor networks can provide large amounts of data that, when combined with pre-processing and data analysis processes, can generate large amounts of data that may be difficult to present in visual forms. Often, understanding of the data and how it spatially and temporally changes as well as the patterns suggested by the data are of interest to human viewers. This chapter considers the issues involved in the visual presentations of such data and includes an analysis of data set sizes generated by wireless sensor networks and a survey of existing wireless sensor network visualization systems. A novel model is presented that can include not only the raw data but also derived data indicating certain patterns that the raw data may indicate. The model is informally presented and a simulation-based example illustrates its use and potential.

Distributed Group Security for Wireless Sensor Networks

Wireless sensor networks (WSNs) are made up of large groups of sensor nodes that usually perform distributed monitoring services. These services are often cooperative and interchange sensitive data, so communications within the group of sensor nodes must be secured. Group key management (GKM) protocols appeared, and were broadly studied, in order to ensure the privacy and authentication throughout the group life. However, GKM for WSNs is already challenging due to the exposed nature of wireless media, the constrained resources of sensor nodes, and the need of ad-hoc self-organization in many scenarios. In this chapter we present the basis of GKM and its state-of-the art for WSNs. We analyze the current non-resolved topics and we present a GKM proposal that solves some of these topics: it minimizes both the rekeying costs when the group membership changes and the routing cost within the group.

Network-Wide Broadcast Service in Wireless Sensor Networks

Network-wide Broadcast is one of the most fundamental services in wireless sensor networks (WSNs). It facilitates sensor nodes to propagate messages across the whole network, serving a wide range of higher-level operations and thus being critical to the overall network design. A distinct feature of WSNs is that many sensor nodes alternate between the active state and the dormant state, so as to conserve energy and extend the lifetime of the network. Unfortunately, the impact of such cycles has been largely ignored in existing network-wide broadcast implementations that adopt the common assumption of all sensor nodes being active all over the whole broadcast process. In this chapter, we first provide a brief survey on previous research works on network-wide broadcast services. We then revisit the network-wide broadcast problem by remodeling it with active/dormant cycles and showing the practical lower bounds for the time and message costs, respectively. We also propose an adaptive algorithm named RBS (Reliable Broadcast Service) for dynamic message forwarding scheduling in this context, which enables a reliable and efficient broadcast service with low delay. The performance of the proposed solution is evaluated under diverse network configurations. The results suggest that the proposed solution is close to the lower bounds of both time and forwarding costs, and it well resists to the network size and wireless loss increases.

Sink Mobility in Wireless Sensor Networks

The use of sink mobility in wireless sensor networks (WSN) is commonly recognized as one of the most effective means of load balancing, ultimately leading to fewer failed nodes and longer network lifetime. The aim of this chapter is to provide a comprehensive overview and evaluation of various WSN deployment strategies involving sink mobility as discussed in the literature to date. The evaluation of the surveyed techniques is based not only on the traditional performance metrics (energy consumption, network lifetime, packet delay); but, more importantly, on their practical feasibility in real-world WSN applications. The chapter also includes sample results of a detailed OPNET-based simulation study. The results outline a few key challenges associated with the use of mobile sinks in ZigBee sensor networks. By combining analytical and real-world perspective on a wide range of issues concerning sink mobility, the content of this book chapter is intended for both theoreticians and practitioners working in the field of wireless sensor networks.

Jamming Attacks and Countermeasures in Wireless Sensor Networks

Guaranteeing security of the sensor network is a challenging job due to the open wireless medium and energy constrained hardware. Jamming style Denial-of-Service attacks is the transmission of radio signals that disrupt communications by decreasing the signal to noise ratio. These attacks can easily be launched by jammer through, either bypassing MAC-layer protocols or emitting a radio signal targeted at blocking a particular channel. In this chapter, we survey different jamming attack models and metrics, and figure out the difficulty of detecting and defending such attacks. We also illustrate the existed detecting strategies involving signal strength and packet delivery ratio and defending mechanisms such as channel surfing, mapping jammed region, and timing channel. After that, we explore methods to localize a jammer, and propose an algorithm Geometric-Covering based Localization. Later, we discuss the future research issues in jamming sensor networks and corresponding countermeasures.

Middleware Support for Wireless Sensor Networks

Wireless sensor networks (WSNs) are gaining visibility due to several sophisticated applications in which they play a key role, such as in pervasive computing and context-aware systems. However, the evolution of WSN capabilities, especially regarding their ability to provide information, brings complexity to their development, in particular for those application developers that are not familiar with the technology underlying and needed to support WSNs. In order to address this issue and allow the use of the full potential of the sensor network capabilities, the use of a middleware that raises the abstraction level and hides much of the WSN complexity is a promising proposal. However, the development of a middleware for WSNs is not an easy task. Systems based on WSNs have several issues that make them quite different from conventional networked computer systems, thus requiring specific approaches that largely differ from the current solutions. The proposal of this chapter is to address the complexity of middleware made for sensor networks, presenting a taxonomy that characterizes the main issues in the field. An overview of the state-of-the-art is also provided, as well as a critical assessment of existing approaches.

Privacy and Trust Management Schemes of Wireless Sensor Networks

Until recently, researchers have focused on the cryptographic-based security issues more intensively than the privacy and trust issues. However, without the incorporation of trust and privacy features, cryptographic-based security mechanisms are not capable of singlehandedly providing robustness, reliability and completeness in a security solution. In this chapter, we present generic and flexible taxonomies of privacy and trust. We also give detailed critical analyses of the state-of-the-art research, in the field of privacy and trust that is currently not available in the literature. This chapter also highlights the challenging issues and problems.

Joint Link Scheduling and Topology Control for Wireless Sensor Networks with SINR Constraints

This chapter studies the joint link scheduling and topology control problems in wireless sensor networks. Given arbitrarily located sensor nodes on a plane, the task is to schedule all the wireless links (each representing a wireless transmission) between adjacent sensors using a minimum number of timeslots. There are two requirements for these problems: first, all the links must satisfy a certain property, such as that the wireless links form a data gathering tree towards the sink node; second, all the links simultaneously scheduled in the same timeslot must satisfy the SINR constraints. This chapter focuses on various scheduling algorithms for both arbitrarily constructed link topologies and the data gathering tree topology. We also discuss possible research directions.

A Survey on Applied Cryptography in Secure Mobile Ad Hoc Networks and Wireless Sensor Networks

Many secure mobile ad hoc networks (MANETs) and wireless sensor networks (WSNs) use techniques of applied cryptography. Numerous security routing protocols and key management schemes have been designed based on public key infrastructure (PKI) and identity-based cryptography. Some of these security protocols are fully adapted to fit the limited power, storage, and CPUs of these networks. For example, one-way hash functions have been used to construct disposable secret keys instead of creating public/private keys for the public key infrastructure. In this survey of MANET and WSN applications we present many network security schemes using cryptographic techniques and give three case studies of popular designs.

Connected k-Coverage Protocols for Densely Deployed Wireless Sensor Networks

In this chapter, we study duty-cycling to achieve both k-coverage and connectivity in highly dense deployed wireless sensor networks, where each location in a convex sensor field (or simply field) is covered by at least k active sensors while maintaining connectivity between all active sensors. Indeed, the limited battery power of the sensors and the difficulty of replacing and/or recharging batteries on the sensors in hostile environments require that the sensors be deployed with high density in order to extend the network lifetime. Also, the sensed data originated from source sensors (or simply sources) should be able to reach a central gathering node, called the sink, for further analysis and processing. Thus, network connectivity should be guaranteed so sources can be connected to the sink via multiple communication paths. Finally, wireless sensor networks suffer from scarce energy resources. A more practical deployment strategy requires that all the sensors be duty-cycled to save energy. With duty-cycling, sensors can be turned on or off according to some scheduling protocol, thus reducing the number of active sensors required for k-coverage and helping all sensors deplete their energy as slowly and uniformly as possible. We also extend our discussion to connected k-coverage with mobile sensors as well as connected k-coverage in a three-dimensional deployment area. Furthermore, we discuss the applicability of our protocols to heterogeneous wireless sensor networks.