Tsenka Stoyanova

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.

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.

Experimental evaluation of a WSN platform power consumption

Critical characteristics of wireless sensor networks, as being autonomous and comprising small or miniature devices are achieved at the expense of very strict available energy related limitations. Therefore, it is apparent that optimal resource management is among the most important challenges in WSNs development and success.

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.

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.

Integrated Toolset for WSN Application Planning, Development, Commissioning and Maintenance: The WSN-DPCM ARTEMIS-JU Project

In this article we present the main results obtained in the ARTEMIS-JU WSN-DPCM project between October 2011 and September 2015. The first objective of the project was the development of an integrated toolset for Wireless sensor networks (WSN) application planning, development, commissioning and maintenance, which aims to support application domain experts, with limited WSN expertise, to efficiently develop WSN applications from planning to lifetime maintenance. The toolset is made of three main tools: one for planning, one for application development and simulation (which can include hardware nodes), and one for network commissioning and lifetime maintenance. The tools are integrated in a single platform which promotes software reuse by automatically selecting suitable library components for application synthesis and the abstraction of the underlying architecture through the use of a middleware layer. The second objective of the project was to test the effectiveness of the toolset for the development of two case studies in different domains, one for detecting the occupancy state of parking lots and one for monitoring air concentration of harmful gasses near an industrial site.

Evaluation and managing sensor network connectivity trough a set of graph theory methods

Connectivity is crucial feature of every network and assuring it, is fundamental for the network operation and efficiency. This work presents a connectivity evaluation algorithm based on graph theory methods, which can be used for simulation and analysis of the network regarding its connectivity in pre-deployment phase. For each network topology the following metrics can be computed: the number of the network parts, the number of the single critical node and the number of the double critical nodes, i.e., any node or combination of two nodes, which failure partitions the network. In case that the network is partitioned, the number of the isolated nodes, the number of the sub-network parts and the number of nodes belonging to each part are also calculated and enumerated.