Milan Simek

A new approach for multi-sink environments in WSNs

Wireless Sensor Networks are low cost networks constituted by modest devices with limited resources, whose main function is monitoring. Based on the low price of these devices, it will be cheap to deploy a large amount of nodes to monitor a large area. However, to provide an efficient ad hoc network using these limited devices, new and optimized algorithms should be proposed. Most of the current work about WSNs are based on simulation studies and do not take in consideration engineering processes. This paper presents a Multi-Sink Node alternative to multi-hop solutions. The proposed solution also provides a new system for the discovery of devices and services over IPv6, allowing nodes to be automatically incorporated in the nearest WSN. This paper also presents a paradigm to efficiently provide mobility, granting a fast handover of nodes between different WSNs, without loosing the connection.

Comprehensive Performance Analysis of ZigBee Technology Based on Real Measurements

Although the ZigBee technology is massively deployed the performance question still remains unanswered. There is a lack of serious performance evaluations and thus this paper provides a comprehensive and unbiased study of the ZigBee PRO technology. An extensive real measurement was conducted to accomplish this task. We found out a big performance gap among ZigBee implementations even though they are compliant with the ZigBee standard. The presented results and analysis could be beneficial for many wireless sensor network developers.

Investigation of radio channel uncertainty in distance estimation in wireless sensor networks

The distance estimation between nodes is a crucial requirement for localization and object tracking. Received signal strength (RSS) measurement is one of the used methods for the distance estimation in wireless networks. Its main advantage is that there are no additional hardware requirements. This paper describes a lateration approach for localization and distance estimation using RSS. For the purpose of investigation of RSS uncertainty, several scenarios were designed for both indoor and outdoor measurements. The first set of RSS measurement scenarios was proposed with the intention of hardware independent investigation of radio channel. For the second set of measurements, we employed IRIS sensor nodes to evaluate the distance estimation with certain devices. The experiments considered also obstacles in the radio channel. The results obtained in the proposed scenarios present usability of the method under different conditions. There is also a signal propagation model constructed from measured data at a node, which subsequently serves for distance determination.

Measurement of LowPAN Network Coexistence with Home Microwave Appliances in Laboratory and Home Environments

Due to a low installation cost of communication infrastructure, Low Power Wireless Area Networks (low PAN) presents an efficient solution for home and building automation. The low PANs operate in a microwave radio band that is often shared by several home appliances. Laptops, wireless routers, cordless phones and microwave ovens occupy the 2.4 GHz band without any channel allocation and thus interoperability with the low PAN systems presents a significant challenge. Therefore, we have performed several laboratory experiments to study the coexistence of low PAN devices with WiFi equipped laptop, WiFi router and microwave oven. The performance evaluation was based on a measurement of Packet Delivery Ratio (PDR) metric. Results shows that presence of the home appliances in the low PAN environment significantly affects the low PAN communication efficiency. Furthermore, we have deployed Zigbee based wireless network in the home environment to study the communication performance in area perturbed by common home radio interferences and obstacles. The lessons learned from network deployment are also presented within the paper.

Comparison of hardware and software based encryption for secure communication in wireless sensor networks

This paper deals with the energy efficient issue of cryptographic mechanisms used for secure communication between devices in wireless sensor networks. Since these devices are mainly targeted for low power consumption appliances, there is an effort for optimization of any aspects needed for regular sensor operation. On a basis of utilization of hardware cryptographic accelerators integrated in microcontrollers, this article provides the comparison between software and hardware solutions. Proposed work examines the problems and solutions for implementation of security algorithms for WSN devices. Because the speed of hardware accelerator should be much higher than the software implementation, there are examination tests of energy consumption and validation of performance of this feature. Main contribution of the article is real testbed evaluation of the time latency and energy requirements needed for securing the communication. In addition, global evaluation for all important network communication parameters like throughput, delay and delivery ratio are also provided.

SensMap: Web framework for complex visualization of indoor & outdoor sensing systems

Technology of Wireless Sensor Networks as a part of Internet of Things world has experienced very dramatic development boom in recent decades. One can say that technology for smart sensing, even the wireless one is already in its mature state. With the huge mass of IoT data that will appear in the Internet in the next years, the rise of novel web-cloud services has been fomented. In this paper we introduce novel web-based Visualization Framework called SensMap that serves for user-friendly interpretation of IoT data stored in the Xively web-cloud. The SensMap framework offers three different visualization perspectives based on the location of sensor devices. These perspectives together with the operation fundamentals of the SensMap are introduced within this paper.

Energy demands of 802.15.4/ZigBee communication with IRIS sensor motes

Limited energy sources of nodes in wireless sensor networks require a careful consideration of energy consumption of all processes during the sensors deployment. To analyze energy consumption and to predict a lifetime of a network, a comprehensive energy model based on commercial products is necessary. Therefore, we have focused on the analysis of energy consumption during RF communication with particular 802.15.4 compliant nodes. We have designed experimental testbed and explored the scenario of node association and data transmission. For the measurement we used IRIS sensor nodes with 802.15.4/Zigbee protocol stack and shunt connection. The results show that energy consumption cannot be calculated only from datasheet values of current drain and length of a packet but intervals of listening and waiting between transmissions play important role as well.

Why should multicast be used in WSNs

Wireless sensor networks present a great potential in monitoring systems. A vast scope of applications can take advantage of WSNs and, mainly because of their own nature, the aggregation of WSN nodes into groups provides more potential solutions when compared with traditional monitoring systems. This paper introduces the issue of multicast messages and their impact on battery resources of WSNs. It presents a study based on a real implementation to evaluate the energy consumed by each node when a multicast or unicast is used. A study of the multicast impact in the neighbourhood is also presented in this paper.

Wireless Sensor Networks in Intensive Care Units

Knowledge of patients weight is essential for daily practice in intensive care units. Many medications, including anticoagulants, nutrition, antibiotics and vasopressors are dependent on weight and height for precise dosing. Patients weight is used to adjust the dose of many drugs, and the dosages of infusions of vasoactive drugs are expressed in micrograms per kilogram of body weight per minute so that cardiovascular function can be assessed and comparisons between patients can be made. This paper presents a new laboratorial prototype based on wireless sensor networks to measure weight of patients. The technology proposed presents several advantages like simplicity and robustness, resulting in an alternative approach that can be used massively replacing old and expensive solutions in intensive care units. The platform implemented monitors the weight of each bedfast patient, triggering an alarm every time an unusual situation occurs. It also provides a complete suite of tools to manage, access and control all situations related to each patient.

Evaluation of PHY layer throughput of ultra wide band IEEE 802.15.4a technology

The ultra wide band transmission present the effective solution for the precise ranging and high data rates applications. Standard IEEE 802.15.4 defining PHY and MAC layers for the low power wireless devices was in 2007 extended by amendments aiming to include the ultra wide band frequency bands in order to react on the demands for the ranging and high data rates low power applications. This standard is referred to as IEEE 802.15.4a. We have proposed the mathematical model of the transmission duration estimation. The mathematical model was applied at the set of configuration parameters such as length of the synchronization preamble, pulse repetition frequency and payload size in order to comprehensively analyze the system throughput at the physical layer.