It is a generally accepted fact that software ages over time. This requires software products to be replaced once their ageing inhibits the goals of the organization owning the product. However, few techniques are available for quantifying the negative effects of ageing software. In this extended abstract, we present an approach to quantifying the ageing of a software architecture. The approach can, among others, be used to decide upon the retirement of a software product line. Validation of the approach is in progress, but not reported upon in this extended abstract.
As the number of wireless sensor network applications continues to grow, the need for specialized task scheduling mechanisms, aware of the sensor devices' capabilities and real-time resource availability, is becoming more and more apparent. In this paper, we therefore propose a generic model for task scheduling in heterogeneous networks, which we subsequently use to schedule distributed reasoning tasks, originating from a real-world WSN monitoring and management application. By means of simulation, we evaluate several developed scheduling heuristics and compare the results to an optimal solution of the same WSN task scheduling problem, obtained using ILP. Experiments show that our heuristics produce acceptable task schedules while maintaining a low resource footprint.
Energy harvesting has been steadily gaining interest in the wireless sensor network community. Instead of minimizing the energy consumption and maximizing a network’s operational time, the main challenge in energy harvesting sensor networks is to maximize the utility of the application subject to the harvested energy. One major challenge is to maximize the data delivery rates by exploiting the spatial variations of environmental energy. While there exists a multiplicity of energy-aware routing protocols for sensor networks without energy harvesting capabilities, only a small number of routing protocols have been published which explicitly account for energy harvesting. In this paper, we analyze and compare three state-of-the-art routing algorithms. While the original algorithms assume an idealized medium access control (MAC), a lossless wireless channel and global knowledge, we show that these assumptions lead to delusive results. We detail these findings by showing the influence of a low-power MAC protocol, a realistic wireless channel and the protocol overhead. Moreover, we show how to optimize the parameters of the MAC protocol for a given network configuration. By conducting various evaluations, we identify that our modified version of the R-MPRT algorithm outperforms the evaluated algorithms in scenarios where little energy is harvested from the environment.
The scale and complexity of advanced cyber-physical systems (CPSs) are steadily growing. Most new-generation CPSs being developed or to be developed involve networked embedded computing (NEC) devices. The state of the art in software engineering for such network-based CPSs is weak. Major problems faced are the low quality of network-based CPS software and the low productivity of CPS software engineers. One type of desirable advance in enhancing the state of the art is to establish high-level programming tools boosting the productivity of software engineers. Here additional types of desirable advance are discussed. Specifically, the establishment of methods and tools for quantitatively analyzable fault tolerance design as well as for design of time-constrained security enforcement is proposed.
Using directional antenna in ad hoc networks, offer many benefits in contrast to their classical omni-directional counterparts. The most important benefits are the significant improvement in spatial reuse, reduction of the radio interference, increase in coverage range and subsequently an increase in network capacity on the whole. On the other hand, directional transmission increases the hidden terminal problem and the problem of deafness. To best utilize directional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard for Wireless LANs, assume the omni-directional antenna at its Physical layer and thus does not fully exploit the capabilities of a directional antenna. In this paper, we propose a MAC protocol for wireless ad hoc networks which fully exploits the potentials of directional antennas. We evaluate our work through simulation studies performed on the network simulator – NS2. Numerical results show that our protocol offers significant improvement in throughput when compared to the performance of traditional 802.11 MAC protocol and D-MAC which is a Directional MAC protocol for ad hoc networks.
Next-generation wireless sensor networks will be used for many diverse applications in time-varying network/environment conditions and on heterogeneous sensor nodes. Although Quality of Service (QoS) has been ignored for a long time in the research on wireless sensor networks, it becomes inevitably important when we want to deliver an adequate service with minimal efforts under challenging network conditions. Until now, there exist no general-purpose QoS architectures for wireless sensor networks and the main QoS efforts were done in terms of individual protocol optimizations. In this paper we present a novel layerless QoS architecture that supports protocol-independent QoS and that can adapt itself to time-varying application, network and node conditions. We have implemented this QoS architecture in TinyOS on TmoteSky sensor nodes and we have shown that the system is able to support protocol-independent QoS in a real life office environment.
Recently, smart spaces are being created using RFID or USN technologies in ubiquitous computing environments, and the number of researches and applications related with context-aware systems, which process sensed data collected from numerous sensors and provide automated services properly according to situations, are ever increasing. There are also sharp increase in demands and needs for location-based services using location information, due to the development of wireless internet and mobile systems. This paper proposes a system which allows the users to access desired services by interacting with service providers at any place in various smart spaces using mobile devices such as smart phones. We propose the Location-based Context-Aware Web Service Framework, so called LOCA Framework, by applying SOA model as a way of satisfying these requirements.
A parameter estimation method for a target object in an area that sensors monitor is described, where the parameters to be estimated are the perimeter length, the size, and a parameter determined by the interior angles of the target object. The estimation method does not use sensor location information, only the binary information on whether each sensor detects the target object. First, the sensing area of each sensor is assumed to be line-segment-shaped, which is a model of an infrared distance measurement sensor. Second, based on the analytical results of assuming line-segment-shaped sensing areas, we developed a unified equation that works with general sensing areas and general target-object shapes to estimate the parameters of the target objects. Numerical examples using computer simulation show that our method yields accurate results.
Wireless sensors with accelerometers are widely used in various studies on human body movements. The most challenging problem in a small body-attachable sensing unit is how to maximize the battery lifetime. Previously, the preferred approach was to reduce the number of transmissions through data compression. Compressed Sensing(C-S) is an emerging alternative approach that aggressively reduces the samples yet permits the reconstruct of the original analog signal. C-S has the great potential to be extremely effective due to the universality and lower complexity of sensor implementation. In this paper, we investigate the nature of various human body movements. We examine the performance of the C-S framework in terms of the energy savings in a real testbed. Our experimental results show that the C-S framework can save up to 40% of energy in the sensing unit, compared with the traditional data compression scheme.
Symbol synchronization is a critical component in the design of an underwater acoustic modem. Without accurate symbol synchronization, higher bit error rates incur thus reducing the reliability and quality of service of the wireless network. This paper provides a practical description of the design choices and hardware implementation details required to build a compact and efficient symbol synchronizer suitable for a short-range, low-power underwater FSK acoustic modem. Experimental results show the design meets the timing requirements of the underwater modem and provides accurate synchronization while consuming only 0.240W power in a Spartan3 xc3s2000 FPGA.
This paper proposes a data dissemination framework to support participatory sensing in a disaster response network formed by mobile, battery-driven devices in case of a large-scale outage or infrastructure failure. Such networks are often unpredictable, heterogeneous, and constrained in terms of energy, bandwidth, and storage. The delivery ratio of the messages highly depends on the routing information used to decide on optimal message forwarding and replication. Various routing metrics are employed in different network environments, ranging from a static connected network to a mobile disconnected environment. In this unpredictable and heterogeneous environment, no single metric results in optimal decisions at all times. We propose a framework that can use several widely used metrics as plug-ins thereby making more intelligent decisions through a dynamic combination of these metrics. Since every routing metric makes specific assumptions about the underlying network, its routing information becomes more accurate when these assumptions hold (e.g. static nodes or certain mobility patterns). Our protocol automatically adapts to a previously unknown network where the appropriate routing assumptions can not be determined beforehand or is different throughout the network. We evaluate the protocol rigorously to illustrate how our combination mechanism provides accurate information from a set of metrics which may disagree. We compare our protocol against widely used sensor network and DTN routing protocols and show that it provides a higher delivery ratio in a wide range of scenarios.
The recent proliferation of satellite imaging technologies and advancements of internet infrastructure have encouraged provisions of satellite image services in web environments. However, most of these services still rely upon low-resolution satellite images combined with DEM. In this paper, we propose the adaptive rendering engine which renders high-spatial resolution satellite images for proficient streaming services on web. From the Mt. Bukhan data as a pilot study, it is shown that the proposing approach efficiently solves graphical issues in real time processing of large geographical area.
Many enterprise applications can benefit from the use of wireless sensors, for example for monitoring location and state of goods. While modern backend IT systems use elaborate Service Oriented Architectures based on Web Services, the resource constraints of sensor nodes require highly optimized embedded programming and proprietary networking protocols. This paper aims at bridging this gap by extending Web Service Oriented Architectures to wireless sensors in a standard compliant way while not exceeding the constrained resources of sensor nodes - thus contributing to the formation of a Web of Things. In particular, we enable self-description of embedded Web services through efficient compression of WSDL documents, we support discovery of embedded Web services by means of an efficient embedded discovery protocol, and we enable backend IT systems to invoke embedded Web services on sensor nodes and vice versa by providing an open framework for protocol conversion. We implement our proposal to obtain key performance figures.
Wireless sensor networks have been studied for several applications. Disaster damage monitoring is one of the significant applications in sensor networks. If sensors are set up in buildings or on water pipelines, they could detect damage, victims trapped beneath rubble, or water leakage in case of a natural disaster. Since such a monitoring system is required to operate for a long term (e.g. several years) by batteries, power consumption of a node would be a critical issue. To fulfill the requirement, intermittent operation is employed in several medium access control (MAC) protocols in sensor networks. Moreover, those monitoring systems have to deal with several types of information, such as temperature, acceleration, alarm signals and so on, in some cases including image data to comprehend surrounding conditions. Some of them are gathered periodically, and some are in event-driven operation. Due to the diversity of information resources in sensor networks, the monitoring system requires short latency in bidirectional communications to control the process of data transmission dynamically. Considering these conditions, this paper describes a damage monitoring scheme using bidirectional low latency operation on a MAC protocol, which implements a short latency on bidirectional transmission in an active/sleep operation mode. Some fundamental evaluations show that the protocol is capable of achieving the short latency.
This work addresses the problem of balancing the trade-off between the energy expenses due to communication vs. the accuracy of the trajectories representation in Wireless Sensor Networks (WSN) where the spatio-temporal data is obtained by tracking. We consider some of the approaches used by the Moving Objects Databases (MOD) and Computational Geometry (CG) communities, and we demonstrate that, with appropriate modifications, they can yield benefits in WSN in terms of energy savings. Towards that, we developed distributed algorithms that implement the Dead-Reckoning policy for managing the transient location-in-time information of mobile entities, whose localization is done by tracking sensors. In addition, we developed a distributed variant of the Douglas-Peuker heuristic for polyline reduction from CG literature, augmented with temporal awareness. Our experiments demonstrate the benefits in terms of reducing the communication overheads, while keeping the error boundaries at acceptable levels. Although it may seem counter-intuitive at first, we also demonstrate that an attempt to merge the Dead-Reckoning and Douglas-Peuker approaches, need not yield additional improvements of the in-network energy savings, due to the complementary nature of the data reduction in the two approaches.
As sensor networks are finding widespread use across many applications, designers increasingly must not only focus on application development, but also on sensor network optimizations. Given the complexities of sensor networks and the difficulty of analyzing the long-term effects of design changes within a deployed system, simulation is often the only feasible option for evaluating such optimizations.The Arizona Transaction-Level Simulator for Sensor Networks (ATLeS-SN) is a transaction-level modeling based sensor network simulation environment emphasizing modular design for modeling various components within sensor nodes and across the sensor network. We provide an overview of our proposed ATLeS-SN simulation framework and highlight the benefits of this framework for a building monitor application and a forest fire detection and propagation tracking application.
In mobile wireless sensor networks (MWSNs), since sensor nodes are highly resource constrained, it is effective to retrieve sensor observations using a top-k query, in which the observations are ordered by the value (or score) of a particular type of sensor, and the query-issuing node acquires sensor observations with the k highest scores. In our previous work, we proposed a message processing method for a topk query in mobile ad hoc networks (MANETs) for reducing traffic and keeping the accuracy of the query result. This method basically works well, however, it cannot avoid the deterioration of the accuracy when network partitioning occurs. In this paper, we assume MWSNs and propose data replication methods for keeping high accuracy of the query result even at the point of network partitioning. The proposed methods replicate sensor observations with high scores when each node sends and relays sensor observations to the query-issuing node.
Ubiquitous computing envisions applications that provide seamless and distraction-free support for everyday tasks. To achieve this goal, applications must be able to adapt to their environment and to the intents of their users. Thereby, they need to automate adaptation decisions to minimize the resulting distraction. As a consequence, it is necessary to acquire an understanding of the user’s current situation to ensure that the automation results in a desirable application behavior. The wide-spread use of personal mobile devices provides a promising technical basis to acquire this knowledge in a seamless manner. However, in order to account for the resource limitations of such devices, existing personal context recognition systems are typically highly specialized and cannot be adapted easily to different scenarios. In this paper, we motivate the need for an generic personal context recognition system and we derive the requirements on such systems. As an approach towards creating such a system, we describe NARF - our ongoing effort to create an adaptive context recognition framework. To assess the benefits and limitations of the architecture, we discuss an application that we have built using our current prototypical implementation of this framework.
We present an application of an open source platform for wireless body sensor network called DexterNet to the problem of monitoring different subjects. The architecture of the system consists of three layers. At the body sensor layer (BSL), the integrated monitoring of a person's activities, geographic location, and air pollution exposures occurs. At the personal network layer (PNL), a wireless mobile device worn by the person summarizes the sensed data, and provides information feedback. The mobile device communicates wirelessly over the Internet with the third global network layer (GNL), in which a web server provides the following four information services: a clinical module that supports the healthcare management of different health problems cases, a personal health module that supports individual prevention of some health symptoms, a community module that supports participatory sensing, and a health research module that supports the collection of anonymous sensor data for research into the risk factors associated with the given health issues. We illustrate the potential for the system to serve as a comprehensive strategy to manage different health cases .
This paper suggests a framework for the book evolution in ubiquitous computing age. Based on the review of the academic researches and industrial development, we suggest the three dimensions of the evolution of books: digitalization, augmentation, and hypermediation. Based on the framework, we suggest three research and business development directions: 1) Open Hypermediation, 2) e-Book Augmentation, and 3) Mobile-Device Based Augmentation.
