Wireless sensor networks (WSNs) are attracting great interest in a number of application domains concerned with monitoring and control of physical phenomena, as they enable dense and untethered deployments at low cost and with unprecedented flexibility. However, application development is still one of the main hurdles to a wide adoption of WSN technology. In current real-world WSN deployments, programming is typically carried out very close to the operating system, therefore requiring the programmer to focus on low-level system issues. This not only distracts the programmer from the application logic, but also requires a technical background rarely found among application domain experts. The need for appropriate high-level programming abstractions, capable of simplifying the programming chore without sacrificing efficiency, has long been recognized, and several solutions have hitherto been proposed, which differ along many dimensions. In this article, we survey the state of the art in programming approaches for WSNs. We begin by presenting a taxonomy of WSN applications, to identify the fundamental requirements programming platforms must deal with. Then, we introduce a taxonomy of WSN programming approaches that captures the fundamental differences among existing solutions, and constitutes the core contribution of this article. Our presentation style relies on concrete examples and code snippets taken from programming platforms representative of the taxonomy dimensions being discussed. We use the taxonomy to provide an exhaustive classification of existing approaches. Moreover, we also map existing approaches back to the application requirements, therefore providing not only a complete view of the state of the art, but also useful insights for selecting the programming abstraction most appropriate to the application at hand.

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Programming wireless sensor networks: Fundamental concepts and state of the art

Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automation where WSNs may be used for monitoring and control of industrial plants and equipment. However, the requirements in the industrial systems differ from the general WSN requirements. In recent years, standards have been defined by several industrial alliances. These standards are specified as frameworks with modifiable parts that can be defined based on the particular application of WSN. However, limited work has been done on defining industry-specific protocols that could be used as a part of these standards. In this survey, we discuss representative protocols that meet some of the requirements of the industrial applications. Since the industrial applications domain in itself is a vast area, we divide them into classes with similar requirements. We discuss these industrial classes, set of common requirements and various state-of-the-art WSN standards proposed to satisfy these requirements. We then present a broader view towards the WSN solution by discussing important functions like medium access control, routing, and transport in detail to give some insight into specific requirements and the classification of protocols based on certain factors. We list and discuss representative protocols for each of these functions that address requirements defined in the industrial classes. Security function is discussed in brief, mainly in relation to industrial standards. Finally, we identify unsolved challenges that are encountered during design of protocols and standards. In addition some new challenges are introduced and discussed.

An Industrial Perspective on Wireless Sensor Networks — A Survey of Requirements, Protocols, and Challenges

The conventional border patrol systems suffer from intensive human involvement. Recently, unmanned border patrol systems employ high-tech devices, such as unmanned aerial vehicles, unattended ground sensors, and surveillance towers equipped with camera sensors. However, any single technique encounters inextricable problems, such as high false alarm rate and line-of-sight-constraints. There lacks a coherent system that coordinates various technologies to improve the system accuracy. In this paper, the concept of BorderSense, a hybrid wireless sensor network architecture for border patrol systems, is introduced. BorderSense utilizes the most advanced sensor network technologies, including the wireless multimedia sensor networks and the wireless underground sensor networks. The framework to deploy and operate BorderSense is developed. Based on the framework, research challenges and open research issues are discussed.

BorderSense: Border patrol through advanced wireless sensor networks

As the number of computing devices embedded into engineered systems continues to rise, there is a widening gap between the needs of the user to control aggregates of devices and the complex technology of individual devices. Spatial computing attempts to bridge this gap for systems with local communication by exploiting the connection between physical locality and device connectivity. A large number of spatial computing domain specic languages (DSLs) have emerged across diverse domains, from biology and recongurable computing, to sensor networks and agent-based systems. In this paper, we develop a framework for analyzing and comparing spatial computing DSLs, survey the current state of the art, and provide a roadmap for future spatial computing DSL investigation.

Organizing the Aggregate: Languages for Spatial Computing

Body Sensor Networks (BSNs) represent an emerging technology which has received much attention recently due to its enormous potential to enable remote, real-time, continuous and non-invasive monitoring of people in health-care, entertainment, fitness, sport, social interaction. Signal processing for BSNs usually comprises of multiple levels of data abstraction, from raw sensor data to data calculated from processing steps such as feature extraction and classification. This paper presents a multi-layer task model based on the concept of Virtual Sensors to improve architecture modularity and design reusability. Virtual Sensors are abstractions of components of BSN systems that include sensor sampling and processing tasks and provide data upon external requests. The Virtual Sensor model implementation relies on SPINE2, an open source domain-specific framework that is designed to support distributed sensing operations and signal processing for wireless sensor networks and enables code reusability, efficiency, and application interoperability. The proposed model is applied in the context of gait analysis through wearable sensors. A gait analysis system is developed according to a SPINE2-based Virtual Sensor architecture and experimentally evaluated. Obtained results confirm that great effectiveness can be achieved in designing and implementing BSN applications through the Virtual Sensor approach while maintaining high efficiency and accuracy.

From Modeling to Implementation of Virtual Sensors in Body Sensor Networks

Initial deployments of wireless sensor networks (WSNs) were based on a many-to-one communication paradigm, where a single sink collects data from a number of data sources. Recently, however, scenarios with multiple sinks are increasingly being proposed, e.g., to deal with actuator nodes or to support high-level programming abstractions. The resulting many-to-many communication makes the existing solutions for single-sink scenarios inefficient.

In this paper, we propose a scheme for routing data efficiently from multiple sources to multiple sinks. We first study the problem from a theoretical standpoint, by mapping it to the multi-commodity network design problem. This allows us to derive an optimal solution that, albeit based on global knowledge and therefore impractical, provides us with a theoretical lower bound to evaluate decentralized solutions against. Then, we propose our own decentralized scheme, based on a periodic adaptation of the message routes aimed at minimizing the number of network links exploited. The resulting protocol is simple and easily implementable on WSN devices. The evaluation of our implementation shows that our protocol generates 50% less overhead than the base scheme without adaptation, a result close to the theoretical optimum we derived.

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Efficient routing from multiple sources to multiple sinks in wireless sensor networks

Recent trends in wireless sensor network (WSN) applications exhibit increasing degrees of decentralization. This is particularly true of scenarios where the data reported by sensors is used to control actuators affecting the environment. Implementing this control loop in a decentralized fashion is much more complex than in mainstream, single-sink, sense-only applications.In this paper we describe virtual nodes, a programming abstraction simplifying the development of decentralized WSN applications. The data acquired by a set of sensors can be collected, processed according to an application-provided aggregation function, and then perceived as the reading of a single virtual sensor. Dually, a virtual actuator provides a single entry point for distributing commands to a set of real actuator nodes. The set of physical nodes to be abstracted into a virtual one is specified using logical neighborhoods [11, 12]. Using virtual nodes, the programmer focuses on the application logic, rather than on low-level implementation details. We present the programming language constructs supporting virtual nodes, exemplify their use, and show that they can be implemented by making efficient use of communication resources.

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Pietro Ciciriello

Papers

Efficient routing from multiple sources to multiple sinks in wireless sensor networks

Building virtual sensors and actuators over logical neighborhoods