Optimization Methods for Energy Consumption Estimation in Wireless Sensor Networks

The main problems in wireless sensor technologies are the constrained energy resources (e. g., battery capacity, processing consumption), and their long-lasting operational capacity in the environment while collecting and sending data to the central station. So, in the design and development of wireless sensor networks, one of the main challenges is to achieve maximal battery life. Real time monitoring by implementation of wireless sensor networks contributes to minimization of potential production risks, emerging mainly from environmental influences and human actions. The main goal in this paper is to obtain minimal energy consumption of wireless sensor nodes while collecting distributed data in environmental parameters monitoring. The communication module and the controller should be in idle state as long as possible when they are not active. Energy consumption changes with the frequency of the transmitted measurement data by the sensors and send/receive configuration of the radio frequency modules. Therefore, all of these parameters should be chosen carefully in order to create an optimal environmental monitoring system. In this contribution the stochastic optimization method-genetic algorithm is used to minimize the energy consumption of the wireless sensor nodes depending on the frequency of the transmitted data and the period of the transmission process. The optimization method is implemented for different scenarios while the frequency of the transmitted data is increasing and the period of transmission of all the active components in a sensor node is increasing

Design methodology for ultra low-power analog circuits using next generation BSIM6 MOSFET compact model

The recently proposed BSIM6 bulk MOSFET compact model is set to replace the hitherto widely used BSIM3 and BSIM4 models as the de-facto industrial standard. Unlike its predecessors which were threshold voltage based, the BSIM6 core is charge based and thus physically continuous at all levels of inversion from linear operation to saturation. Hence, it lends itself conveniently for the use of a design methodology suited for low-power analog circuit design based on the inversion coefficient (IC) that has been extensively used in conjugation with the EIN model and allows to make simple calculations of, for example, transconductance efficiency, gain bandwidth product, etc. This methodology helps to make a near-optimal selection of transistor dimensions and operating points even in moderate and weak inversion regions. This paper will discuss the IC based design methodology and its application to the next generation BSIM6 compact MOSFET model. (C) 2013 Elsevier Ltd. All rights reserved

Virtual visual sensors and their application in structural health monitoring

Wireless sensor networks are being increasingly accepted as an effective tool for structural health monitoring. The ability to deploy a wireless array of sensors efficiently and effectively is a key factor in structural health monitoring. Sensor installation and management can be difficult in practice for a variety of reasons: a hostile environment, high labour costs and bandwidth limitations. We present and evaluate a proof-of-concept application of virtual visual sensors to the well-known engineering problem of the cantilever beam, as a convenient physical sensor substitute for certain problems and environments. We demonstrate the effectiveness of virtual visual sensors as a means to achieve non-destructive evaluation. Major benefits of virtual visual sensors are its non-invasive nature, ease of installation and cost-effectiveness. The novelty of virtual visual sensors lies in the combination of marker extraction with visual tracking realised by modern computer vision algorithms. We demonstrate that by deploying a collection of virtual visual sensors on an oscillating structure, its modal shapes and frequencies can be readily extracted from a sequence of video images. Subsequently, we perform damage detection and localisation by means of a wavelet-based analysis. The contributions of this article are as follows: (1) use of a sub-pixel accuracy marker extraction algorithm to construct virtual sensors in the spatial domain, (2) embedding dynamic marker linking within a tracking-by-correspondence paradigm that offers benefits in computational efficiency and registration accuracy over traditional tracking-by-searching systems and (3) validation of virtual visual sensors in the context of a structural health monitoring application

24GHz CMOS direct downconversion receiver front-end and VCO design

Because of advancements in RF CMOS circuits, devices, and passive elements in the last decade, it has become possible to develop a RF system-on-chip (SoC) that integrates RF, analog and digital circuits completely. Direct downconversion, or zero-IF downconversion architecture, shows an advantage over traditional superheterodyne architectures, because it eliminates the image rejection filter and IF filter, and employs only one local oscillator (LO), which reduces the receiver size and power dissipation significantly. For this reason, direct downconversion has drawn more and more attention recently in various wireless applications. However, it also presents some design challenges like flicker noise, DC offsets, even-order distortion, and I/Q mismatches. In this work, a thorough noise analysis and a comprehensive study of the noise mechanism of the low noise amplifier of CMOS direct downconversion receivers (DCR) is given. Also addressed is the design of a cross-coupled LC voltage-controlled oscillator (VCO). For the low noise amplifier, which presents major noise contribution to the DCR front-end, an optimization technique which employs both a parallel capacitance and an inter-stage inductor is proposed. The addition of this capacitance helps keep the active device relatively small, and the analysis on the effects of the inter-stage inductor shows that it helps boost gain of the LNA at the desired operation frequency of 2.4GHz, and offers a lower noise figure. In order to achieve direct downconversion, both a passive switching mixer and an active double-balanced mixer are presented. The passive switching mixer helps solve the problem of flicker noise, but suffers power loss, while the double-balanced architecture helps relieve the problems of DC offset and second-order distortion. The last part of this presentation is about a partially tunable CMOS LC-VCO which achieves good phase noise performance at the cost of smaller tuning range. It uses on-chip spiral inductors and junction varactors in the resonant LC-tank. The presented building blocks can be used for a low-power, low-voltage DCR front-end for 802.11b/g applications. It is concluded that direct downconversion architecture can find its use in low-power, low-cost 802.11b and Bluetooth applications should the circuit design make use of the optimization techniques addressed in this work

Ανάλυση Κυρίων Συνιστωσών για την Αποτελεσματική Μετάδοση Πληροφορίας σε Ασύρματα Δίκτυα Αισθητήρων

Οι εφαρμογές που βασίζονται σε Ασύρματα Δίκτυα Αισθητήρων (Wireless Sensor Networks, WSN) επηρεάζονται από πολλούς παράγοντες, όπως σφάλματα μετάδοσης, τοπολογία του δικτύου και την κατανάλωση ενέργειας. Κατά συνέπεια, η ανάπτυξη τέτοιων εφαρμογών εισάγει διάφορες ερευνητικές προκλήσεις. Στη διπλωματική εργασία προτείνεται ένα νέο σχήμα συμπίεσης πληροφορίας πλαισίου με τη βοήθεια των μαθηματικών τεχνικών της Ανάλυσης Κύριων Συνιστωσών (Principal Component Analysis). Το σχήμα αυτό επιτυγχάνει υψηλή συμπίεση σε συσχετισμένα δεδομένα (μετρήσεις θερμοκρασίας και υγρασίας που έχουν ληφθεί σε ανοικτούς χώρους), χωρίς παράλληλα να παρατηρείται σημαντική αύξηση στο σφάλμα.Applications based on Wireless Sensor Networks (WSN) are influenced by many factors such as transmission errors, network topology and power consumption. Consequently, developing such applications introduces several research challenges. The thesis proposes a new compression format information framework with using of mathematical techniques of Principal Component Analysis (Principal Component Analysis). The scheme achieves high compression associated data (temperature and humidity measurements taken outdoors), while no significant increase in error

Two-tier, location-aware and highly resilient key predistribution scheme for wireless sensor networks /

Sensor nodes are low power, tiny, and computationally restricted microelectromechanical devices that usually run on battery. They are capable of communicating over short distances and of sensing information for specific purposes. In sensor networks, large amount of sensor nodes are deployed over a wide region. For secure communication among sensor nodes, secure links must be established via key agreement. Due to resource constraints, achieving such key agreement in wireless sensor networks is non-trivial. Many key establishment schemes, like Diffie-Hellman and public-key cryptography based protocols, proposed for general networks are not so suitable for sensor networks due to resource constraints. Since one cannot generally assume a trusted infrastructure, keys and/or keying materials must be distributed to sensor nodes before deployment of them. Such key distribution schemes are called key predistribution schemes. After deployment, sensor nodes use predistributed keys and/or keying materials to establish secure links using various techniques. In this thesis, we propose a probabilistic key predistribution scheme, in which we assume that certain deployment knowledge is available prior to deployment of sensor nodes. We use a two-tier approach in which there are two types of nodes: regular nodes and agent nodes. Agent nodes, which constitute a small percentage of all nodes, are more capable than regular nodes. Most of the regular nodes can establish shared keys among themselves without the help of agent nodes, whereas some other regular nodes make use of agent nodes as intermediaries for key establishment. We give a comparative analysis of our scheme through simulations and show that our scheme provides good connectivity for the sensor network. Moreover, our scheme exhibits substantially strong node-capture resiliency against small-scale attacks, while the resiliency of the network degrades gracefully as the number of captured nodes increases. In addition, the proposed scheme is scalable such that increasing the number of nodes in the network does not degrade the performance and does not increase the complexity. Another good characteristic of our scheme is that it is resistant against node fabrication and partially resistant against wormhole attacks

Study of Techniques For Reliable Data Transmission In Wireless Sensor Networks

This thesis addresses the problem of traffic transfer in wireless sensor networks (WSN). In such networks, the foremost challenge in the design of data communication techniques is that the sensor's transceiver circuitry consumes the major portion of the available power. Thus, due to stringent limitations on the nodes' hardware and power resources in WSN, data transmission must be power-efficient in order to reduce the nodes' power consumption, and hence to maximize the network lifetime while satisfying the required data rate. The transmit power is itself under the influence of data rate and source-destination distance. Thanks to the dense deployment of nodes in WSN, multi-hop communication can be applied to mitigate the transmit power for sending bits of information, i.e., gathered data by the sensor nodes to the destination node (gateway) compared to single-hop scenarios. In our approach, we achieve a reasonable trade-off between power-efficiency and transmission data rate by devising cooperative communication strategies through which the network traffic (i.e. nodes' gathered information) is relayed hop-by-hop to the gateway. In such strategies, the sensor nodes serve as data originator as well as data router, and assist the data transfer from the sensors to the gateway. We develop several data transmission schemes, and we prove their capability in transmitting the data from the sensor nodes at the highest possible rates allowed by the network limitations. In particular, we consider that (i) network has linear or quasi-linear topology, (ii) nodes are equipped with half-duplex radios, implying that they cannot transmit and receive simultaneously, (iii) nodes transmit their traffic at the same average rate. We compute the average data rate corresponding to each proposed strategy. Next, we take an information-theoretic approach and derive an upper bound to the achievable rate of traffic transfer in the networks under consideration, and analyze its tightness. We show that our proposed strategies outperform the conventional multi-hop scheme, and their average achievable rate approaches the upper bound at low levels of signal to noise ratio

Power-aware systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 147-156).In this thesis, we formalize the notion of power-aware systems and present a methodology to systematically enhance power-awareness. We define a power-aware system as one which scales its power consumption with changes in its operating scenario with a view to maximizing its energy efficiency. Operating scenarios are primarily characterized by five dimensions - input statistics, output quality requirements, tolerable latency (and/or throughput constraints), internal state and environmental conditions. We quantify the power-awareness of a system by equating it to the energy efficiency with which it can track changes along these dimensions. This is done by comparing the system's energy consumption in a scenario to that of a dedicated system constructed to execute only that scenario as energy efficiently as possible. We then propose a systematic technique that enhances the power-awareness of a system by composing ensembles of point systems. This technique is applied to multipliers, register-files, digital filters and variable-voltage processors demonstrating increases in battery-lifetimes of 60%-200%. In the second half of this thesis we apply power-awareness concepts to data-gathering wireless networks. We derive fundamental bounds on the lifetime of networks and demonstrate the tightness of these bounds using a combination of analytical arguments and simulation. Finally, we show that achieving a high degree of power-awareness in a wireless sensor network is equivalent to optimally or near-optimally solving the role-assignment problem. Provably optimal role assignment strategies using linear programming are presented. Hence, optimal strategies can be determined in a time that is polynomial in the number of nodes. As a result of applying power-awareness formalisms, the energy efficiency, and hence the lifetime of data gathering networks increases significantly over power-unaware schemes.by Manish Bhardwaj.S.M

Energy-efficient design and implementation of turbo codes for wireless sensor network

The objective of this thesis is to apply near Shannon limit Error-Correcting Codes (ECCs), particularly the turbo-like codes, to energy-constrained wireless devices, for the purpose of extending their lifetime. Conventionally, sophisticated ECCs are applied to applications, such as mobile telephone networks or satellite television networks, to facilitate long range and high throughput wireless communication. For low power applications, such as Wireless Sensor Networks (WSNs), these ECCs were considered due to their high decoder complexities. In particular, the energy efficiency of the sensor nodes in WSNs is one of the most important factors in their design. The processing energy consumption required by high complexity ECCs decoders is a significant drawback, which impacts upon the overall energy consumption of the system. However, as Integrated Circuit (IC) processing technology is scaled down, the processing energy consumed by hardware resources reduces exponentially. As a result, near Shannon limit ECCs have recently begun to be considered for use in WSNs to reduce the transmission energy consumption [1,2]. However, to ensure that the transmission energy consumption reduction granted by the employed ECC makes a positive improvement on the overall energy efficiency of the system, the processing energy consumption must still be carefully considered.The main subject of this thesis is to optimise the design of turbo codes at both an algorithmic and a hardware implementation level for WSN scenarios. The communication requirements of the target WSN applications, such as communication distance, channel throughput, network scale, transmission frequency, network topology, etc, are investigated. Those requirements are important factors for designing a channel coding system. Especially when energy resources are limited, the trade-off between the requirements placed on different parameters must be carefully considered, in order to minimise the overall energy consumption. Moreover, based on this investigation, the advantages of employing near Shannon limit ECCs in WSNs are discussed. Low complexity and energy-efficient hardware implementations of the ECC decoders are essential for the target applications