Wireless sensor networks (WSNs), being a relatively new technology, largely employ protocols designed for other ad hoc networks, especially mobile ad hoc networks (MANETs). However, on the basis of applications, there are many differences between WSNs and other types of ad hoc network and so WSNs would benefit from protocols which take into account their specific properties, especially in routing. Bhatti and Yue (2006) proposed an addressing scheme for multi-hop networks. It provides a systematic address structure for WSNs and allows network topology to avoid the fatal node failure problem which could occur with the ZigBee tree structure. In this work, a new routing strategy is developed based on Bhatti and Yue’s addressing scheme. The new approach is to implement a hybrid flooding scheme that combines flooding with shortest-path methods to yield a more practical routing protocol for static WSN applications. The primary idea is to set a flooding counter K as an overhead parameter of control messages which are used to discover routes between any arbitrary nodes. These route request messages are flooded for K hops and then oriented by shortest-path routing from multiple nodes in the edge of the flooding area to the destination. The simulation results show that this protocol under certain wireless circumstances is more energy conscious and produces less redundancy than reactive ZigBee routing protocol. Another advantage is that the routing protocol can adapt any dynamic environment in various WSN applications to achieve a satisfactory data delivery ratio in exchange for redundancy.

Wireless sensor networks (WSNs) are increasingly being used for monitoring physical environments in lieu of tethered monitoring systems. Being power efficient and wirelessly accessible, WSNs find applications in a variety of domains like health, structural and climate monitoring systems. Despite such diverse use cases, more than often, WSNs are used by researchers with basic or no prior programming experience. Consequently, more time is spent learning to program the sensors than collecting and analysing domain-specific data. To cater to this generic user base, a multi-platform user-friendly programming framework for WSNs has been developed. This framework provides: 1) a visual network comparison tool that analyzes packet traces of two networks to generate a juxtaposed visual comparison of contrasting network characteristics, 2) a scripting language based on the TinyOS sensor network platform that aims at reducing code size and improving programming efficacy, and 3) a visual programming tool with basic sensor drag-and-drop modules for generating simple WSN programs. These tools were also developed to serve as a gentle introduction to the WSN programming environment for middle and high school students. In the absence of resources (sensors), the framework also allows programmers to verify program functionality by remotely simulating and verifying program behaviour in the OMNeT simulation environment.

A wireless sensor network is a collection of numerous sensors distributed on an area of interest to collect and process data from the environment. One particular threat in wireless sensor networks is node compromise attacks, that is, attacks where the adversary gets physical access to a node and to the programs and keying material stored on it. Only authorized queries should be allowed in the network and the integrity and confidentiality of the data that is being collected should be protected. We propose a layered key distribution scheme together with two protocols for query authentication and confidential data aggregation. The layered key distribution is more robust to node and communication failures than a predefined tree structure. The protocols are secure under the assumption that less than n sensor nodes are compromised. n is a design parameter that allows us to trade off security for overhead. When more than n sensor nodes are compromised, our simulations show that the attacker can only introduce unauthorized queries into a limited part of the network and can only get access to a small part of the data that is aggregated in the network. Considering the data collection protocol we also contribute with strategies to reduce the energy consumption of an integrity preserving in-network aggregation scheme to a level below the energy consumption of a non-aggregation scheme. Our improvements reduce node congestion by a factor of three and the total communication load by 30%. Location privacy of the users carrying mobile devices is another aspect considered in this thesis. Considering a mobile sink that collects data from the network, we propose a strategy for data collection that requires no information about the location and movement pattern of the sink. We show that it is possible to provide data collection services, while protecting the location privacy of the sink. When mobile phones with built-in sensors are used as sensor nodes, location information about where the data has been sensed can be used to trace users and infer other personal information about them, like state of health or personal preferences. Therefore, location privacy preserving mechanisms have been proposed to provide location privacy to the users. We investigate how a location privacy preserving mechanism influences the quality of the collected data and consider strategies to reconstruct the data distribution without compromising location privacy. / WISENET

Wireless sensor networks have many sensor devices that send their data to the sink or base station for further processing. This is called direct delivery. But this leads to heavy traffic in the network and as the nodes are limited with energy, this decreases the lifetime of the network. So data aggregation technique is introduced to improve the lifetime. This technique aggregates or merges the multiple incoming packets in to single packet and forwards it to sink. There is different data aggregation techniques based on the topology of the network. This report clearly explains the purpose of data aggregation and gathering in WSN, data aggregation in flat networks and data aggregation in hierarchical networks, different data aggregation techniques in cluster based networks, chain based, tree based and grid based networks. Data aggregation technique can successfully minimize the data traffic and energy consumption only when it is carried out in a secure manner. Part2 of the survey explains the possible attacks that affect data aggregation in wireless sensor network. The secure data aggregation techniques in wireless sensor networks are also discussed in this report.

The purpose of this research is to reduce maintenance resources and improve Escravos–Gas–to–Liquids plant availability (EGTL) in Escravos, Nigeria using wireless condition monitoring. Secondary to the above is to justify the use of this technology over other conventional condition monitoring methods in petrochemical plants with specific reference to cost, reliability and security of the system. Wireless and continuous condition monitoring provides the means to evaluate current conditions of equipment and detect abnormalities. It allows for corrective measures to be taken to prevent upcoming failures. Continuous monitoring and event recording provides information on the energized equipment's response to normal and emergency conditions. Wireless/remote monitoring helps to coordinate equipment specifications and ratings, determine the real limits of the monitored equipment and optimize facility operations. Bentley N, (2005). Using wireless techniques eliminate any need for special cables and wires with lower installation costs if compared to other types of condition monitoring systems. In addition to this, wireless condition monitoring works well under difficult conditions in strategically important locations. The Escravos gas–to–liquid plant in Nigeria, located in a remote and offshore area where accommodation and space for offices is a factor for monitoring plant conditions in every office, is a typical example. Wireless technology for condition monitoring of energized equipment is applicable to both standalone and remote systems. In the research work of Meyer and Brambley (2002), they characterized the current problem with regards to cost effectiveness and availability of wireless condition monitoring. Maintenance of rotating equipment provides probability estimates of the total impact of the problem, cost implication of plant equipment maintenance and describes a generic system in which these developing technologies are used to provide real–time wireless/remote condition monitoring for rotating main air compressor (MAC) units and their components as a case study. Costs with today’s technology are provided and future costs are estimated, showing that benefits will greatly exceed costs in many cases, particularly if low–cost wireless monitoring is used. With management trends such as “re–engineering” and “downsizing” of the available workforce, wireless condition–monitoring of critical machines has been given more importance as a way to ensure quality production with fewer personnel. Wireless condition–monitoring using inexpensive wireless communication technology frees up existing plant maintenance personnel work on machines that are signaling problems and focusing the maintenance efforts away from attempting to work on a large population of machines to only those machines requiring immediate attention. Lloyd and Buddy (200) suggested that Point–to–point wireless data transmission systems, an excellent example of recent technological advances in communication systems, are now practical and cost–effective for industrial use. While both complex infrastructures and complex protocols are required for cellular communications, non– cellular communication systems, such as the point–to–point wireless data transmission system example, require no elaborate infrastructure. Limited research was done on the immediate benefits of implementing wireless condition monitoring systems in plants. All papers on the subject have been drawn up by manufacturers of such equipment. This research will thus also deliver a "third–party" perspective on the effectiveness of such devices, justifying their impact on data gathering security, cost and reliability. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2012.

The objective of the proposed research is to integrate nanotechnology, applied electromagnetics, and inkjet printing fabrication methods to develop a series of novel inkjet-printed RF modules for sensing and communication applications: wireless gas sensor, wearable RFID tag, and RF inductor. Passive, wireless sensors have various applications in a wide range of fields including military, industry, and medicine. However, there are issues such as cost, sensitivity of sensors, manufacturing complexities, and feasibility of further miniaturization of these RF modules. One aspect of this research investigates the feasibility of addressing these issues by integrating nanotechnology and applied electromagnetics. The underlying common theme for the three designs is inkjet-printing silver nanoparticles on organic paper substrate. The research will investigate the characterization of thin film carbon nanotubes and the optimization of inkjet-printing the CNT material on paper substrate followed by the design of a patch antenna based gas sensor. Measurement results from a closed measurement system will be shown. Secondly, an inkjet-printed, conformal, wearable RFID tag on an artificial magnetic conductor is designed and tested using an RFID Reader. Lastly an inkjet-printed high Q RF inductor is designed and integrated with magnetic nanomaterial to evaluate the feasibility of increasing inductance using high permeability nanomaterial. Through the design and testing of the aforementioned three designs, it will be shown that through a multidisciplinary design process, novel, low-cost RF modules can be designed for sensing and communication applications.

In order to improve efficiency and reliability of the world's power grids, sensors are being deployed for constant status monitoring. Placing inexpensive wireless sensors on high-voltage power lines presents a new challenge to the RF engineer. Large electric field intensities can exist around a wireless sensor antenna on a high-voltage power line, leading to the formation of a corona plasma. A corona plasma is a partially ionized volume of air formed through energetic electron-molecule collisions mediated by a strong electric field. This corona can contain large densities of free electrons which act as a conducting medium, absorbing RF energy and detuning the sensor's antenna. Through the use of low-profile antennas and rounded geometries, the possibility for corona formation on the antenna surface is greatly reduced, as compared with wire antennas. This study looks at the effects of a corona plasma on a patch antenna, which could be used in a power line sensor. The corona's behavior in the presence of an electromagnetic plane wave is analyzed mathematically to understand the dependence of attenuation on frequency and electron density. A Drude model is used to convert plasma parameters such as electron density and collision frequency to a complex permittivity that can be incorporated in antenna simulations. Using CST Microwave Studio, a 5.8 GHz patch antenna is simulated with a plasma material on its surface, of varying densities and thicknesses. Power absorption by the plasma dominates the power loss, as opposed to detuning. A wideband patch is simulated to show that the detuning effects by the plasma can be further reduced. Power absorption by the plasma is significant for electron densities greater than 10¹⁸ m⁻³. However, small point corona are found to have little effect on antenna radiation.

Context represents any knowledge obtained from Wireless Sensor Networks (WSNs) about the object being monitored (such as time and location of the sensed events). Time and location are important constituents of context as the information about the events sensed in WSNs is comprehensive when it includes spatio-temporal knowledge. In this thesis, we first concentrate on the development of a suite of lightweight algorithms on temporal event ordering and time synchronization as well as localization for WSNs. Then, we propose an energy-efficient clustering routing protocol for WSNs that is used for message delivery in the former algorithm. The two problems - temporal event ordering and synchronization - are dealt with together as both are concerned with preserving temporal relationships of events in WSNs. The messages needed for synchronization are piggybacked onto the messages exchanged in underlying algorithms. The synchronization algorithm is tailored to the clustered topology in order to reduce the overhead of keeping WSNs synchronized. The proposed localization algorithm has an objective of lowering the overhead of DV-hop based algorithms by reducing the number of floods in the initial position estimation phase. It also randomizes iterative refinement phase to overcome the synchronicity of DV-hop based algorithms. The position estimates with higher confidences are emphasized to reduce the impact of erroneous estimates on the neighbouring nodes. The proposed clustering routing protocol is used for message delivery in the proposed temporal algorithm. Nearest neighbour nodes are employed for inter-cluster communication. The algorithm provides Quality of Service by forwarding high priority messages via the paths with the least cost. The algorithm is also extended for multiple Sink scenario. The suite of algorithms proposed in this thesis provides the necessary tool for providing spatio-temporal context for context-aware WSNs. The algorithms are lightweight as they aim at satisfying WSN's requirements primarily in terms of energy-efficiency, low latency and fault tolerance. This makes them suitable for emergency response applications and ubiquitous computing.

In this thesis, an investigation of the performance of multipath routing in Wireless Sensor Networks (WSN) is performed. The communication in the network under study is to take place from individual nodes to the sink node. The investigation involved multipath finding methods in WSN. Also, it involves investigating the weight assignment, traffic splitting and route selection methods for the different paths discovered by each node in the WSN. Also, a comparison between Hybrid Routing Protocol, Source Routing Protocol and Diffusion Routing Protocol is performed. A simple traffic routing algorithm for each routing protocol has been developed to conceptualize how the network traffic is routed on a set of active paths. The investigation of the Hybrid, Source and Diffusion Routing Protocol involved using multiple paths simultaneously to transmit messages that belong to the same flow by using a weight assigned to each path and transmit each message as a whole. Finally, the power consumption and the QoS in terms of message delays for a WSN were investigated and compared between different protocols.

Data aggregation is an important technique in wireless sensor networks. The data are gathered together by data fusion routines along the routing path, which is called data-centralized routing. We propose a localized, Delay-bounded and Energy-efficient Data Aggregation framework(DEDA) based on the novel concept of DEsired Progress (DEP). This framework works under request-driven networks with realistic MAC layer protocols. It is based on localized minimal spanning tree (LMST) which is an energy-efficient structure. Besides the energy consideration, delay reliability is also considered by means of the DEP. A node’s DEP reflects its desired progress in LMST which should be largely satisfied. Hence, the LMST edges might be replaced by unit disk graph (UDG) edges which can progress further in LMST. The DEP metric is rooted on realistic degree-based delay model so that DEDA increases the delay reliability to a large extent compared to other hop-based algorithms. We also combine our DEDA framework with area coverage and localized connected dominating set algorithms to achieve two more resilient DEDA implementations: A-DEDA and AC-DEDA. The simulation results confirm that our original DEDA and its two enhanced variants save more energy and attain a higher delay reliability ratio than existing protocols.