Fotis Kerasiotis

Evaluation of impact factors on RSS accuracy for localization and tracking applications

The use of RSSI (Received Signal Strength Indicator), obtained automatically with the received messages in most sensor radios, is the popular way for estimating the location of the mobile wireless object. The great variation of RSS (Received Signal Strength), which may result in inaccurate estimations, is compensated by the fact that RSS does not require any additional hardware, as in the case of ultrasound and radar techniques, and may reduce the sensor node power consumption, size and cost. This paper investigates the impact of a series of parameters on RSS by experimenting with Tmote Sky nodes in real outdoor environments. Besides the operating frequency, the transmitterreceiver distance, the variation of transceivers, the antenna orientation, and the environment specifics were found as important factors for creating accurate models, which would serve in tracking and localization applications.

Battery Lifetime Prediction Model for a WSN Platform

Wireless Sensor Network devices have by nature limited available energy to perform a wide range of demanding tasks. In order to maximize their operation lifetime, optimal resource management is an important challenge and its success requires methodical modeling of the factors contributing to the overall power consumption. Moreover, the power consumed is not always useful on its own, but it should rather express the expected lifetime concerning the device’s normal operation. To achieve such awareness, this paper contributes with a measuring methodology which involves combining power consumption of platform elementary functionalities with battery discharge characteristics, so that a practical, yet accurate battery lifetime prediction model can be formed.

A Practical RF Propagation Model for Wireless Network Sensors

In the present work, we propose a practical RF propagation model – Free-space Outdoor Model – suitable for WSN due to the fact that it considers the most important WSN constraints and RF signal propagation path loss factors. The model is based on combining four path loss factors, which cause distortion and weakening of the RF signal, i.e. free-space path loss, ground reflection path loss, RSS uncertainty and antenna pattern irregularity. The proposed model is verified with actual measurements realized with Tmote Sky sensor node equipped with 2.4GHz CC2420 radio module.

Evaluation of impact factors on RSS accuracy for localization and tracking applications in sensor networks

The use of Received Signal Strength Indicator (RSSI), obtained automatically with the received messages in most sensor radios, is a popular way for estimating the location of a mobile wireless object. The great variation of Received Signal Strength (RSS), which may result in inaccurate estimations, is compensated by the fact that RSS does not require any additional hardware, and may reduce the sensor node power consumption, size and cost. The present work investigates the impact of variety of parameters on RSS by experimenting with Tmote Sky nodes in real-field outdoor environments. Besides the operating frequency, the transmitter–receiver distance, the variation of transceivers, the antenna orientation, and the environment specifics were found as important factors for creating accurate models, which would serve in tracking and localization applications.

Modeling of the RSS Uncertainty for RSS-Based Outdoor Localization and Tracking Applications in Wireless Sensor Networks

In the present study, we investigate the variability of the RF signal, measured as Received Signal Strength (RSS), in outdoor unobstructed environment aiming at modeling of the RSS uncertainty for the needs of the outdoor RSS-based localization and tracking applications. The modeling approach is based on determining empirically the relation between the RSS mean value and the RSS data deviation. Two modeling tasks are performed, namely RSS-static and RSS-mobile, representing the situation when the localized sensor node is immobile and when it is mobile, i.e., attached to a person. The performed simulation of RSS variance shows good correspondence to the measured variance, which validates the proposed approach.

CSMA-MAC Performance Evaluation for WSN Applications

This paper studies the MAC layer performance in demanding wireless sensor networks. The requirements for wireless MAC are discussed based on a prominent CSMA-based MAC protocol evaluation varying critical network parameters. The objective is to investigate the current radio access technologies suitability for wireless sensor networked applications. The channel access mechanisms are analyzed in more detail, important performance parameters are derived and their behavior in different traffic scenarios is investigated through simulation based analysis.

Developing wireless sensor network applications based on a function block programming abstraction

The dynamic environments where Wireless Sensor Networks (WSNs) are being deployed, nowadays, necessitate the design of appropriate middleware architectures which provide flexible mechanisms to adapt application behavior while making wise utilization of the constrained resources. In combination with heterogeneity issues which usually appear in such networks, this results in high complexity of the application development typically involving the usage of a low or high level programming language in order to assure efficient operation of the network. To deal with these challenges, a modular middleware architecture is proposed which supports a programming abstraction based on the automation domain notion of function blocks (FBs). The network is (re)programmed with new applications in the form of mobile agents which are injected from a base station, while the Service Oriented Architecture (SOA) paradigm is adopted considering the function blocks as services distributed in the WSN nodes according to the resources of the underlying devices. Each agent is a schematic description of wirings between function blocks which are allocated by the middleware in the neighborhood of a target node, being in this way highly autonomous and adaptive, while presenting low resource utilization overhead as it is shown by an application case study.

An overview of development problems in WSNs

As wireless sensor networks (WSNs) are being developed for a wide range of application fields of real-time monitoring and control, a design overview seems important so as to investigate alternative communication aspects while treating the WSN as a whole system. As applications become more demanding the need to consider also deployment constraints and application particularities on top of the commonly used network factors, leads to new integrated design methodologies for addressing all complexity degrees of such systems. In this paper, problems concerning the design aspect of todays WSN applications are presented, which are reasoned to multiple impact factors, to accent design directions and options.

Communication-Aware Deployment for Wireless Sensor Networks

Deployment of senor nodes brings the challenging question on how to place the sensor nodes in order to achieve a particular coverage degree with optimum number of nodes. An important factor, which deployment process also should take into account is the radio signal propagation to guarantee reliable communication links among the network. In the present work, we firstly define a pre-deployment simulation framework and then propose RF signal propagation-based connectivity algorithm (RFCA) for outdoor applications. The RFCA utilizes RF signal propagation model for prediction of received signal strength (RSS). Several parameters of the system are considered for the RSS prediction: the RF frequency, the transmission power, the transmitter-receiver distance, their height from the ground and the antennas characteristics (gain, polarization, etc.). We demonstrate that RFCA is able to find the most appropriate deployment parameters from the communication point of view (height, distance, and transmission power) for positioning of the sensor nodes.

A Topology-Oriented Solution Providing Accuracy for Outdoors RSS-Based Tracking in WSNs

As tracking applications for moving objects become more challenging, demands for accurate and reliable tracking methods using wireless sensor networked devices increase. The use of received signal strength (RSS) of the propagated signals, provided by most sensor radios, is the popular means of achieving such a task. Despite the great RSS variation, which may result in inaccurate estimation of the mobile object position, the advantage is that RSS does not require any additional hardware as in cases like radar and ultrasound techniques and may lower the cost and the size of WSN devices. Parameters such as height from the ground and distance between nodes are examined for their impact on RSS in outdoor environments using the Tmote-Sky platform. Optimal parameter ranges are derived for solving major problems caused by node mobility as well as fading and reflection phenomena of the propagated signal.