Towards database support for moving object data

To narrow down moving object challenges, the focus of this thesis is on four issues, namely, uncertainty handling for moving object data, faithful trajectory representation, trajectory compression techniques, and similarity measures for trajectories

Outlier detection techniques for wireless sensor networks: A survey

In the field of wireless sensor networks, those measurements that significantly deviate from the normal pattern of sensed data are considered as outliers. The potential sources of outliers include noise and errors, events, and malicious attacks on the network. Traditional outlier detection techniques are not directly applicable to wireless sensor networks due to the nature of sensor data and specific requirements and limitations of the wireless sensor networks. This survey provides a comprehensive overview of existing outlier detection techniques specifically developed for the wireless sensor networks. Additionally, it presents a technique-based taxonomy and a comparative table to be used as a guideline to select a technique suitable for the application at hand based on characteristics such as data type, outlier type, outlier identity, and outlier degree

Trajectory Representation in Location-Based Services: Problems and Solution

Recently, much work has been done in feasibility studies on services offered to moving objects in an environment equipped with mobile telephony, network technology and GIS. However, despite of all work on GIS and databases, the situations in which the whereabouts of objects are constantly monitored and stored for future analysis are an important class of problems that present-day database/GIS has difficulty to handle. Considering the fact that data about whereabouts of moving objects are acquired in a discrete way, providing the data when no observation is available is a must. Therefore, obtaining a "faithful representation" of trajectories with a sufficient number of discrete (though possibly erroneous) data points is the objective of this research

Protecting informative messages over burst error channels in chain-based wireless sensor networks

Regardless of the application, the way that data and information are disseminated is an important aspect in Wireless Sensor Networks (WSNs). The wireless data dissemination protocol should often guarantee a minimum reliability requirement. In this regard and to well-balance the energy and reliability, the more important packets should be protected by more powerful error control codes than the less important ones. This information-aware capability allows a system to deliver critical information with high reliability but potentially at a higher resource cost. In this paper, we first find and evaluate the factors that may influence the importance level of a packet and then design an error control approach by adaptively selecting codes for each individual links which experience long-term-fading and for each individual packet at run-time instead of applying network-wide settings prior to deployment. Moreover, we target the poor-explored chain-based topology that is of interest for many applications (e.g. monitoring bridge, tunnel, etc.). Simulation results validate the superiority of our approach compared with a number of Reed-Solomon-based error control approaches

Impact Analysis of Different Scheduling and Retransmission Techniques on an Underwater Routing Protocol

Despite many advances in the area of Underwater Wireless Sensor Networks (UWSN) during the last years, still many challenges need to be successfully tackled before large-scale deployment of underwater sensor networks becomes a reality. UWSNs usually employ acoustic channels for communications, which compared with radio-frequency channels, allow much lower bandwidths and have longer propagation delays. In the past, different methods have been proposed to define how a node must acquire the channel in order to start a transmission. Given the large propagation delays of underwater communication channels, a TDMA-based approach may need big time-guards. On the other hand, the very same large propagation delay increases the occurrence of the hidden terminal problem in a CSMA-based approach. In this paper, impacts of utilization of different scheduling and retransmission techniques on an underwater routing protocol will be analyzed. This analysis, in which energy consumption, packet delay, number of duplicate packets, and packet loss are considered, will be carried out by means of simulation using the Network Simulator 3 and a subset of EDETA (Energy-efficient aDaptive hiErarchical and robusT Architecture) routing protocol recently adapted to UWSN

SVGOpen Conference Guide: An overview

Context-aware applications are emerging on a daily basis and location information proves to be one of the key components in this domain. This stems from the fact that location information enables and facilitates reasoning about what users are doing (user's behavioural patterns) and what users are interested in. Availability of campus-wide WLAN infrastructure at University of Twente (UT) and the fact that SVGOpen 2005 was scheduled to be held at UT, were two strong driving forces towards building a location-aware conference guide. In this paper, a privacy-sensitive, location-aware service architecture is presented, which utilizes a calibration-free localization technique. The presented architecture uses existing WLAN infrastructure for cost efficiency, and uniquely incorporates the location information into Jini service discovery platform. Vector graphics provide better support for highly dynamic interface. Among all available vector formats, SVG proves to be a better choice to design the dynamic user interface and hence it was used in our implementation

A trust-based probabilistic coverage algorithm for wireless sensor networks

Sensing coverage is a fundamental issue for many applications in wireless sensor networks. Due to sensors resource limitations, inherent uncertainties associated with their measurements, and the harsh and dynamic environment in which they are deployed, having a QoS-aware coverage scheme is a must. In this paper, we propose a Trust-based Probabilistic Coverage algorithm, which leverages the trust concept to tackle the uncertainties introduced by the nodes and the environment, in which they operate. We formulate this problem as an Integer Linear Programming (ILP) problem, which is able to always guarantee the required QoS despite uncertainties introduced by node and/or environment. In consideration of the limitation of ILP, we also put forward a greedy heuristic algorithm to achieve almost the same ILP results without suffering from complexities imposed by ILP. We examine our heuristic with different input parameters and compare it with the ILP approach. Simulation results are presented to verify our approaches