Current and future trends in sensor networks: a survey
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paper_title: Optimal design of fault tolerant sensor networks

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The selection of measurements is one of the most important problems in the design of process instrumentation. This paper deals with the design of sensor networks such that the observability of the variables, which are necessary for the process control, remains satisfied in the presence of sensor failures. Pseudo-minimal and minimal sensor sets are organized into an oriented graph which contains all the possible reconfiguration paths for which those variables remain observable. A bottom-up analysis of this graph allows one to compute reliability functions which evaluate the robustness of the observability property with respect to sensor failures. The design of optimal sensor networks thus resumes to finding pseudo-minimal sensor sets such that the mean time before losing the observability property is larger than a pre-defined value.
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paper_title: Handbook Of Batteries

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Part 1 Principles of operation: basic concepts electrochemical principles and reactions factors affecting battery performance standardization of batteries battery design selection and application of batteries. Part 2 Primary batteries: zinc-carbon (Leclanche) cells magnesium and aluminium cells alkaline-manganese dioxide cells mercuric oxide cells silver oxide cells zinc/air cells lithium cells solid electrolyte batteries. Part 3 Reserve batteries: magnesium water-activated batteries spin-dependent reserve batteries liquid ammonia systems lithium anode reserve batteries thermal batteries. Part 4 Secondary batteries: lead acid batteries industrial nickel-cadmium batteries vented nickel-cadmium batteries sealed nickel-cadmium batteries nickel-zinc batteries iron electrode batteries silver-oxide batteries nickel-hydrogen batteries nickel-metal hydride batteries rechargeable alkaline-manganese dioxide batteries. Part 5 Advanced battery systems: ambient temperature lithium batteries zinc/bromine batteries metal/air batteries lithium/iron sulphide batteries sodium beta batteries.
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paper_title: Electrochemical‐Thermal Model of Lithium Polymer Batteries

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A mathematical model has been developed to study heat transfer and thermal management of lithium-polymer batteries. Temperature dependent parameters including the diffusion coefficient of lithium ions, ionic conductivity of lithium ions, transference number of lithium ions, etc., have been added to a previously developed electrochemical model to more completely characterize the thermal behavior of the lithium-polymer system. In addition, experimental studies of the discharge behavior and heat generation rate of lithium-polymer cells have been conducted. Comparisons between experimental and mathematical results are presented. Finally different thermal management approaches are discussed.
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paper_title: Battery-driven system design: a new frontier in low power design

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As an increasing number of electronic systems are powered by batteries, battery life becomes a primary design consideration. Maxiimizing battery life requires system designers to develop an understanding of the capabilities and limitations of the batteries that power such systems, and to incorporate battery considerations into the system design process. Recent research has shown that, the amount of energy that can be supplied by a given battery varies significantly, depending on how the energy is drawn. Consequently, researchers are attempting to develop new battery-driven approaches to system design, which deliver battery life improvements over and beyond what can be achieved through conventional low-power design techniques. This paper presents an introduction to this emerging area, surveys promising technologies that have been developed for battery modeling and battery-efficient system design, and outlines emerging industry standards for smart battery systems.
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paper_title: A PSPICE macromodel for lithium-ion batteries

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Battery models for simulation are useful for estimating operating life, stability, transient response, and related characteristics in circuits and systems. This paper presents a parametric PSPICE macromodel for simulating lithium-ion batteries. Comparisons of the simulation with experimental data from 1.25 Ah lithium-ion cells are then made.
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paper_title: Dynamic source routing in ad hoc wireless networks

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An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. In such an environment, it may be necessary for one mobile host to enlist the aid of other hosts in forwarding a packet to its destination, due to the limited range of each mobile host’s wireless transmissions. This paper presents a protocol for routing in ad hoc networks that uses dynamic source routing. The protocol adapts quickly to routing changes when host movement is frequent, yet requires little or no overhead during periods in which hosts move less frequently. Based on results from a packet-level simulation of mobile hosts operating in an ad hoc network, the protocol performs well over a variety of environmental conditions such as host density and movement rates. For all but the highest rates of host movement simulated, the overhead of the protocol is quite low, falling to just 1% of total data packets transmitted for moderate movement rates in a network of 24 mobile hosts. In all cases, the difference in length between the routes used and the optimal route lengths is negligible, and in most cases, route lengths are on average within a factor of 1.01 of optimal.
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paper_title: Base-station repositioning for optimized performance of sensor networks

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Most of the energy aware routing approaches for unattended wireless sensor networks pursue multi-hop paths in order to minimize the total transmission power. Since almost in all sensor networks data are routed towards a single sink (base-station), hops close to that sink become heavily involved in packet forwarding and thus their batteries get depleted rather quickly. In this paper we investigate the potential of base-station repositioning for enhanced network performance. We address issues related to when should the base-station be relocated, where it would be moved to and how to handle its motion without any effect on data traffic. Our approach tracks the distance from the closest hops to the base-station and the traffic density through these hops. When a hop that forward high traffic is further than a threshold the base-station qualifies the impact of the relocation on the network performance and moves if the overhead is justified. The presented approach is validated in a simulated environment.
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paper_title: Distributed power control in ad-hoc wireless networks

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Mobile ad-hoc networking involves peer-to-peer communication in a network with a dynamically changing topology. Achieving energy efficient communication in such a network is more challenging than in cellular networks since there is no centralized arbiter such as a base station that can administer power management. We propose and evaluate a power control loop, similar to those commonly found in cellular CDMA networks, for ad-hoc wireless networks. We use a comprehensive simulation infrastructure consisting of group mobility, group communication and terrain blockage models. A major focus of research in ad-hoc wireless networking is to reduce energy consumption because the wireless devices are envisioned to have small batteries and be incapable of energy scavenging. We show that this power control loop reduces energy consumption per transmitted byte by 10-20%. Furthermore, we show that it increases overall throughput by 15%.
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paper_title: An energy-efficient MAC protocol for wireless sensor networks

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This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s.
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paper_title: Evaluation of the multipath characteristics of the impulse radio channel

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In order to estimate the performance of impulse radio communication systems, a characterization of the channel is required. In particular, knowledge of the multipath angle and time-of-arrival distributions is useful for predicting the performance of diversity reception schemes. In this paper, the CLEAN algorithm is applied to ultra-wide bandwidth (UWB) signals received on an array of sensors in order to resolve the incident signal components.
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paper_title: Data aggregation in wireless sensor networks - exact and approximate algorithms

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A fundamental challenge in the design of wireless sensor networks (WSNs) is to maximize their lifetimes. Data aggregation has emerged as a basic approach in WSNs in order to reduce the number of transmissions of sensor nodes, and hence minimizing the overall power consumption in the network. We study optimal data aggregation in WSNs. Data aggregation is affected by several factors, such as the placement of aggregation points, the aggregation function, and the density of sensors in the network. The determination of an optimal selection of aggregation points is thus extremely important. We present exact and approximate algorithms to find the minimum number of aggregation points in order to maximize the network lifetime. Our algorithms use a fixed virtual wireless backbone that is built on top of the physical topology. We also study the tradeoffs between energy savings and the potential delay involved in the data aggregation process. Numerical results show that our approach provides substantial energy savings.
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paper_title: Aggregation tree construction in sensor networks

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Large-scale wireless sensor networks are expected to play an increasingly important role in future civilian and military settings. Collaborative microsensors could be very effective in monitoring their operations. However, low power and in-network data processing make data-centric routing in wireless sensor networks a challenging problem. In this paper we propose heuristics to construct and maintain an aggregation tree in sensor networks. This aggregation tree can be used to facilitate data-centric routing. The main idea is to turn off the radio of all leaf nodes to save power, and thereby extending the network lifetime. Therefore, in order to save the number of broadcasting messages, only the nonleaf nodes in the tree are in charge of data aggregation and traffic relaying. In this paper, we propose an efficient energy-aware distributed heuristic to generate the aggregation tree, which we refer to as EADAT. Our EADAT algorithm makes no assumption on local network topology, and is based on residual power. It makes use of neighboring broadcast scheduling and distributed competition among neighbors. These novel concepts make EADAT very efficient and effective, as demonstrated by our simulation experiments with NS2.
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paper_title: Battery-aware static scheduling for distributed real-time embedded systems

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This paper addresses battery-aware static scheduling in battery-powered distributed real-time embedded systems. As suggested by previous work, reducing the discharge current level and shaping its distribution are essential for extending the battery lifespan. We propose two battery-aware static scheduling schemes. The first one optimizes the discharge power profile in order to maximize the utilization of the battery capacity. The second one targets distributed systems composed of voltage-scalable processing elements (PEs). It performs variable-voltage scheduling via efficient slack time re-allocation, which helps reduce the average discharge power consumption as well as flatten the discharge power profile. Both schemes guarantee the hard real-time constraints and precedence relationships in the real-time distributed embedded system specification. Based on previous work, we develop a battery lifespan evaluation metric which is aware of the shape of the discharge power profile. Our experimental results show that the battery lifespan can be increased by up to 29% by optimizing the discharge power file alone. Our variable-voltage scheme increases the battery lifespan by up to 76% over the non-voltage-scalable scheme and by up to 56% over the variable-voltage scheme without slack-time re-allocation.
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Title: Current and Future Trends in Sensor Networks: A Survey

Section 1: Introduction
Description 1: This section introduces sensor networks and provides an overview of their applications, importance, and differences from other wireless networks.

Section 2: Sensor Networks
Description 2: This section describes the components and configurations of sensor networks and their operational modes.

Section 3: Design Factors
Description 3: This section discusses the key design factors for sensor networks, including fault tolerance, scalability, cost, and power consumption.

Section 4: Batteries
Description 4: This section explores battery technologies, modeling approaches, and strategies for enhancing power supply in sensor networks.

Section 5: Routing and MAC Protocols
Description 5: This section reviews routing and medium access control (MAC) protocols tailored for sensor networks, focusing on power efficiency and network topology.

Section 6: Communication
Description 6: This section examines communication techniques, including radio transmission, modulation schemes, and technologies like Ultra Wide Band (UWB) for sensor networks.

Section 7: Data Aggregation
Description 7: This section covers data aggregation techniques to optimize energy consumption and improve the performance of sensor networks.

Section 8: Processors
Description 8: This section discusses low power processor design techniques and the potential use of FPGA technology in sensor networks.

Section 9: Conclusion
Description 9: This section summarizes the challenges, current trends, and future directions for wireless sensor networks.