Karl Benkic

Using RSSI value for distance estimation in wireless sensor networks based on ZigBee

In todaypsilas modern wireless ZigBee-based modules, there are two well-known values for link quality estimation: RSSI (received signal strength indicator) and LQI (link quality indicator). In respect to wireless channel models, received power should be a function of distance. From this aspect, we believed that RSSI can be used for evaluating distances between nodes. The experiment described in this paper indicates that RSSI is, in fact, a poor distance estimator when using wireless sensor networks in buildings. Reflection, scattering and other physical properties have an extreme impact on RSSI measurement and so we can conclude: RSSI is a bad distance estimator.

The Accuracy of Propagation Models for Distance Measurement between WSN Nodes

The accuracy of RF propagation models for distance measurement between WSN nodes using received signal strength indicator (RSSI) was studied. We implemented two simple propagation models, the free space log-normal model and 2-ray ground reflection model. The results show, that first model is not very precise in closed space (rooms). The second model gives quite well agreement with experimental RSSI measurements for greater distances between transmitting and receiving nodes.

Short-Term Photoplethysmography Embedded in Household Appliances

This paper opens new insights into short-term photoplethysmography (PPG) in dynamic condition when opening a refrigerator. Five hundred twelve PPG signals from fingers of 7 healthy volunteers were acquired simultaneously and analysed for heartbeats. Parallel referential electrocardiogram recordings confirmed the heartbeat detection sensitivity and precision of 97.62% and 90.31%, respectively. We also assessed the mean blood pressure, firstly, by measuring pulse transit times and, secondly, by our novel method based on the blood inflow times at the door opening instants. The models derived with exponential fitting proved the inflow times a robust and accurate blood pressure indicator; the mean absolute error was 1.2±0.9 mmHg.

Performance analysis of improved ZigBee wireless network by simulation

In this paper we analyze performance of IEEE 802.15.4/ZigBee wireless networks in order to use these networks for transmitting different data for medical purposes such as ECG, body temperature, acceleration, etc. The aim of study is to improve efficiency of ZigBee standard by variable time and length of data transmit. The original run-length coded method is described.

Inter power electronic building blocks’ communication over two optical rings

Abstract Power electronic building blocks, initiated and sponsored by the Office of Naval Research, are based on the integration of power semiconductor elements with some degree of intelligence and data communication capability in compact form. This article addresses the communication issues between power electronic building blocks. A study case of Inter PEBB communication is described, based on two-optical ring topology and the possibility of complete implementation in a single FPGA for slave nodes.

Routing tree implementation based on semi-matching algorithm(s)

This paper proposes and evaluates the variation of an algorithm for optimal semi-matching, based on the Hungarian method. The proposed algorithm balances the parent-child vertexes in a bipartite graph and can be applied to a wireless sensor network as an algorithm for building virtual routing tree topology. Virtual routing tree topology optimizes the minimum number of message hops to the sink and load balancing. The proposed algorithm runs faster than other compared methods. Virtual topology (spanned tree) is used during very simple routing protocol. Experimental results show that the proposed algorithm preserves the energy, excludes bottle necks, red spots, and expands the lifetime of a network.