Ali Abedi

Wireless sensor systems for space and extreme environments : a review

Using wireless sensor network (WSN) for building new sensing and actuating applications in space and extreme environments (SEEs) can fuel a new application paradigm if it can be adopted into a new strategy. This complementary contribution from the Guest Editors carries an important message of breaking away from conventional WSN research and developments and adopting a heterogeneous agile unconventional wireless sensing (UWS) approach deployment. For this, we urge the use of lightweight WSN known as wireless sensor systems (WSS) to develop optimized solutions for SEE. This paper also discusses some critical technologies of WSS-SEE and includes three key aspects of a new approach to examine: 1) the characterizes of SEE; 2) potential applications of UWS; and 3) heterogeneously nature of the applications. A further clarification for deployment of UWS is demonstrated using a table with six groups of typical application areas from the recent publications media.

Inverse Hysteresis Phenomena During CO and C3H6 Oxidation over a Pt/Al2O3 Catalyst

It is well known that conversion as a function of temperature hysteresis can occur during ignition and extinction exothermic reaction experiments, such as CO oxidation over Pt/Al2O3, with the activity during the ignition process not matching that during the extinction process. Conversions being higher during extinction than that during ignition are often observed. Several explanations have been proposed in which heat effects, different catalyst surface states, and different Pt oxidation states are the most common. In this work CO oxidation hysteresis behavior, when in a mixture with C3H6, was investigated. The results show that when C3H6 was absent, CO oxidation followed normal hysteresis behavior; however, when C3H6 was added to the mixture, the catalytic activity during the extinction phase decreased. As the C3H6 concentration in the mixture increased, the hysteresis loop became smaller and ultimately reverse hysteresis was observed. The decrease in catalytic activity during extinction was due to the formation of C3H6 oxidation intermediate species. These species competed with CO for active sites, thus inhibiting CO oxidation, and were not present during ignition as CO was the dominant adsorbed species when starting at low temperature.Graphical Abstract

Distributed Turbo Coding and Decoding for Wireless Sensor Networks

In this article a distributed turbo coding and iterative decoding scheme is introduced. The proposed scheme with low complexity is suitable for wireless sensor networks applications where many sensors sense similar sources resulting in correlated data sampling. Encoders reside in these sensor nodes which are close to the source, while decoders reside in another group of nodes acting as distributed decoder and relay. The decoder structure is presented using a simple suboptimal solution derived from the maximum a posteriori probability decision rule. Simulation results demonstrates a marked bit error performance at high signal to noise ratios.

Propagation Engineering in Wireless Communications

Propagation Engineering in Wireless Communications covers the basic principles needed for understanding of radiowaves propagation for common frequency bands used in radio-communications. This book includes descriptions of new achievements and new developements in propagation models for wireless communication. The book is intended to bridge the gap between the theoretical calculations and approaches to the applied procedures needed for radio links design in a proper manner. The authors intention is to emphasize propagation engineering by giving sufficient fundamental information and then going on to explain the use of basic principles together with technical achievements in this field.

An analytical method for approximate performance evaluation of binary linear block codes

An analytical method for approximate performance evaluation of binary linear block codes using an additive white Gaussian noise channel model with binary phase-shift keying modulation is presented. We focus on the probability density function of the bit log-likelihood ratio (LLR), which is expressed in terms of the Gram-Charlier series expansion. This expansion requires knowledge of the statistical moments of the bit LLR. We introduce an analytical method for calculating these moments. This is based on some recursive calculations involving certain weight enumerating functions of the code. It is proved that the approximation can be as accurate as desired, if we use enough terms in the Gram-Charlier series expansion. Numerical results are provided for some examples, which demonstrate close agreement with simulation results.

Wireless acoustic wave sensors and systems for harsh environment applications

This paper reviews current progress in the area of wireless microwave acoustic sensor technology, and discusses advances in wireless interrogation systems that can operate in harsh environments. The use of wireless, battery-free, low maintenance surface acoustic wave (SAW) sensors has been successfully demonstrated in applications including high temperature turbine engines and inflatable aerospace structures. Wireless interrogation of multiple sensors up to 910°C has been established and sensor tests in gas turbine engine are reported. This paper elaborates on several aspects of the technology, including: high-temperature thin-film electrode and sensor development, temperature cycling, thermal-shock behavior, testing in turbine engine environments, sensor packaging and attachment, wireless operation, and adaptation to energy and industrial applications.

A reputation-based Stackelberg game approach for spectrum sharing with cognitive cooperation

In this paper, we consider the problem of spectrum sharing with cooperation in a wireless system with two pairs of source-destination links, which have different priorities to access the channel. The cognitive low priority user (LPU) cooperates with the high priority user (HPU), acting as a relay, in exchange for an opportunity to access the channel. We study the interactions between the HPU and the LPU using a game theoretical approach to search for the optimal time allocation for individual transmissions and cooperation among users. We propose a new Stackelberg game formulation, in which the reputation of both users is considered to encourage cooperation and prevent misbehavior. The proposed utility functions are designed so that fairness and energy efficiency are taken into account.

On minimum number of wireless sensors required for reliable binary source estimation

The CEO problem of estimating a single binary data source using multiple observations is considered. A closed form equation for maximum achievable information capacity of the system is derived for different system parameters including number of sensors, observation accuracy and channel quality. A new criterion for sensor clustering is provided based on the minimum number of sensors required to achieve arbitrarily low estimation error using different coding rates. A distributed joint source-channel coding (D-JSCC) scheme is proposed as an implementation example. The proposed coding scheme is based on the parallel concatenated convolutional codes (PCCC) that achieves high BER performance utilizing the number of sensors determined by the derived criterion1.

Distributed homology algorithm to detect topological events via wireless sensor networks

Wireless sensor networks (WSNs) can span large geographical regions and collaboratively monitor environmental phenomena, for example, forest fires. By designing a WSN to detect changes to such phenomena, current environmental monitoring systems could be supplemented, if not replaced. This research focuses on incremental insertion events, arising from the elevation of a single nodes sensor reading between two consecutive states of network operation. Homology, a field of topology, is used to detect and differentiate between incremental insertion events of interest. Particular homology tools are translated to a distributed environment for 2-dimensional WSN deployments. The result is a novel distributed algorithm that can compute an incremental insertion event associated with a region comprising n nodes in O(n) time, using O(n) storage, and O(n) data passed via messages. A small-scale, laboratory testbed is developed to evaluate the algorithm. Deployment results indicate that only nodes in physical proximity to an event are tasked, thereby conserving network resources and allowing multiple disparate events to be simultaneously monitored. Further, transmission cost is shown to vary linearly with the size of the evolving region, confirming one component of the formal analysis.

Wireless sensor system based on SAW coded passive devices for multiple access

This work reports on a wireless sensor system based on coded direct sequence spread spectrum differential delay line surface acoustic wave devices. Spread spectrum techniques were used to interrogate prototype sensor devices with embedded quasi-orthogonal coding, thus allowing multiple device access by the system implemented. A base station unit incorporating analog and reconfigurable digital circuitry has been designed and constructed to interrogate the sensor devices. Sensor and system operation were experimentally verified. The system was validated for temperature sensing.