54 research outputs found
A Model-driven Engineering Framework to Support an Architecture-Driven Development and Analysis of WSNs
No full textA model-driven engineering framework for architecting and analysing Wireless Sensor Networks
No full textA Wireless Sensor Network (WSN) is composed of distributed sensors with limited processing capabilities and energy restrictions. These unique attributes pose new challenges amongst which prolonging the WSN lifetime is one of the most important. Challenges are often tackled by a code-and-fix process that relies on low-level hardware and software information
Effects of IDSs on the WSNs Lifetime: Evidence of the Need of New Approaches
No full textA Wireless Sensor Network (WSN) consists of spatially distributed autonomous sensors that monitor environmental data such as temperature, humidity, light, speed and sound. WSNs pose new security challenges because of their unattended nature and limited resources. Although prevention measures such as encryption and firewalls have been successfully applied, the attacker can physically access the node and modify it. Intrusion Detection Systems (IDSs) are a second line of defence that can be used to mitigate this problem. Building IDSs for WSNs is a new challenge because of the limited resources of the WSN nodes. IDS solutions for sensor networks should try to minimise the use of battery of the sensor nodes in order to prolong the network lifetime. In this paper we analyse different solutions that have been proposed for intrusion detection in wireless sensor networks. More specifically we analyse the impact of popular intrusion detection systems on the life time of the WSNs. Our study is quite general since we consider IDSs that are distributed on the sensor nodes and continuously monitor the networks for evidence of attacks. We also consider IDSs that are event triggered, which means that they require agreement between nodes when a suspicious activity is detected. The agreement is used to detect the attack and isolate the attacker. We analyse the effects of IDSs on battery life. The results show that, popular oral message algorithm of Byzantine generals problem should be considered for small scale WSNs because of the overhead introduced in terms of messages exchanged for decision. We conclude our paper with properties and recommendations for IDSs working for WSNs and some future works
Path Loss Effect on Energy Consumption in a WSN
No full textEnergy consumption of nodes is a crucial factor that constrains the networks life time for Wireless Sensor Networks (WSNs). WSNs are composed of small sensors equipped with low-power devices, and have limited battery power supply. The main concern in existing architectural and optimisation studies is to prolong the network lifetime. The lifetime of the sensor nodes is affected by different components such as the microprocessor, the sensing module and the wireless transmitter/receiver. The existing works mainly consider these components to decide on best deployment, topology, protocols and so on. Recent studies have also considered the monitoring and evaluation of the path loss caused by environmental factors. Path loss is always considered in isolation from the higher layers such as application and network. It is necessary to combine path loss computations used in physical layer, with information from upper layers such as application layer for a more realistic evaluation. In this paper, a simulation-based study is presented that uses path-loss model and application layer information in order to predict the network lifetime. Physical environment is considered as well. We show that when path-loss is introduced, increasing the transmission power is needed to reduce the amount of packets lost. This presents a tradeoff between the residual energy and the successful transmission rate when more realistic settings are employed for simulation. It is a challenging task to optimise the transmission power of WSNs, in presence of path loss, because although increasing the transmission power reduces the residual energy, it also reduces the number of retransmissions required
Does the Assumption of Exponential Arrival Distributions in Wireless Sensor Networks Hold?
No full textWireless sensor networks (WSNs) have seen a tremendous growth in various application areas despite prominent performance and availability challenges. Although researchers continue to address these challenges, the type of distributions for arrivals at the cluster head and intermediary routing nodes is still an interesting area of investigation. The general practice in published works is to compare an empirical exponential arrival distribution of WSNs with a theoretical exponential distribution in a Q-Q plot diagram. In this paper, we show that such comparisons based on simple eye checks are not sufficient since, in many cases, incorrect conclusions may be drawn from such plots. After estimating the maximum likelihood parameters of empirical distributions, we generate theoretical distributions based on the estimated parameters. By conducting Kolmogorov-Smirnov test statistics for each generated inter-arrival time distributions, we find out, if it is possible to represent the traffic into the cluster head by using theoretical distribution. Empirical exponential arrival distribution assumption of WSNs holds only for a few cases. The work is further extended to understand the effect of delay on inter-arrival time distributions based on the type of medium access control (MAC) used in WSNs
A4WSN: an architecture-driven modelling platform for analysing and developing WSNs
No full textThis paper proposes A4WSN, an architecture-driven modelling platform for the development and the analysis of wireless sensor networks (WSNs). A WSN consists of spatially distributed sensor nodes that cooperate in order to accomplish a specific task. Sensor nodes are cheap, small, and battery-powered devices with limited processing capabilities and memory. WSNs are mostly developed directly on the top of the operating system. They are tied to the hardware configuration of the sensor nodes, and their design and implementation can require cooperation with a myriad of system stakeholders with different backgrounds. The peculiarities of WSNs and current development practices bring a number of challenges, ranging from hardware and software coupling, limited reuse, and the late assessment of WSN quality properties. As a way to overcome a number of existing limitations, this study presents a multi-view modelling approach that supports the development and analysis of WSNs. The framework uses different models to describe the software architecture, hardware configuration, and physical deployment of a WSN. A4WSN allows engineers to perform analysis and code generation in earlier stages of the WSN development life cycle. The A4WSN platform can be extended with third-party plug-ins providing additional analysis or code generation engines. We provide evidence of the applicability of the proposed platform by developing PlaceLife, an A4WSN plug-in for estimating the WSN lifetime by taking various physical obstacles in the deployment environment into account. In turn, PlaceLife has been applied to a real-world case study in the health care domain as a running example
Deployment Challenges and Developments in Wireless Sensor Network Clustering
No full textClustering techniques for wireless sensor networks
(WSNs) have been extensively studied and proven to improve the
network lifetime, a primary metric, used for performance evaluation
of sensor networks. Although introduction of clustering
techniques has the potential to reduce energy consumption and
extend the lifetime of the network by decreasing the contention
through either power control or node scheduling, scalability
remains an issue. Therefore, the optimality of the cluster size still
needs to be thoroughly investigated. In this paper, a single cluster
head (CH) queuing model is presented. Using an event based
simulation tool (Castalia), key issues that affect the practical
deployment of clustering techniques in wireless sensor networks
are analysed. These include identifying the bottlenecks in terms
of cluster scalability and predicting the nature of data packets
arrival distribution at the CH. Results presented show that this
analysis can be used to specify the size of a cluster, when a
specific flow of data is expected from the sensing nodes based on
a particular application and also the distribution of the interarrival
times of data packets at the CH follows exponential
distribution.
Index Terms—Wireless Sensor Networks, modelling, performance,
cluster size, scalability, clustering, distributio
A survey study on MAC and routing protocols to facilitate energy efficient and effective UAV-based communication systems
No full textProcess Integration Approaches to Improve the Techno-Economic Feasibility of Torrefaction Process
No full textOver the past few years, the torrefaction process has evolved into a promising pre-treatment process to improve the properties of biomass to a level at which it is competitive with coal. However, in order to make torrefied biomass pellets an economically viable alternative to coal and wood pellets, the techno-economic feasibility of the torrefaction process needs to be improved. Thus, new process configurations are required to produce torrefied biomass pellets and other high value products from the torrefaction process. This thesis presents new process configurations, which have been evaluated with laboratory experiments, process simulations and mathematical modeling.Two different biomass samples i.e. eucalyptus clone and pinewood were used in torrefaction experiments. Initially, the effect that torrefaction pretreatment has on the kinetics, reaction mechanisms and heat flow during biomass pyrolysis was studied using TGA and DSC analysis. The results showed that the pyrolysis reaction mechanism varied significantly with torrefaction treatment. The heat flow data from DSC showed that torrefied biomass pyrolysis requires more energy than dried biomass in order to initiate the pyrolysis reactions.In the second stage, the anaerobic digestion of torrefaction condensate for the efficient utilization of torrefaction volatiles was studied through batch anaerobic digestion assays. Torrefaction condensate produced at 225, 275 and 300 °C was used at various substrate to inoculum ratio i.e. 0.1, 0.2 and 0.5. The methane yield was in the range of 430 - 492 mL/g volatile solids (VS) and 430 - 460 mL/g VS under mesophilic and thermophilic conditions, respectively. With the higher loading, i.e. > 0.2 VSsubstrate:VSinoculum, the production of methane was inhibited because of the inhibitory compounds in the torrefaction condensate, such as furfural and guaiacol.Large quantities of binders are required to make the pelletization process effective and to improve the quality of the pellets. An innovative process configuration is hereby proposed for detoxifying the torrefaction condensate and to reduce the binders’ requirement. The removal of a major inhibitory compound, i.e. furfural, through adsorption using torrefied biomass as an adsorbent was also studied. The adsorption of furfural from the torrefaction condensate at 250 g/L dosage was around 54%. Finally, the influence of the detoxification of the torrefaction condensate on the AD process was studied through batch assays.Finally, the experimental results were used to simulate industrial scale operations to evaluate the feasibility of integrating the torrefaction process with anaerobic digestion. In addition, different process integration approaches were studied to identify possible heat energy recovery options in the torrefaction process, on its own, and also when integrated with AD. The standalone torrefaction process was compared with three different process configurations, which varied according to the intended application for the produced biogas. The mass balance showed that biomethane can be produced at 369 m3/h, at 10 t/h of torrefied biomass pellets production capacity. A sensitivity analysis showed that the cost of the feedstock has a significant effect on the economics of the overall process. The economic analysis showed that the price of torrefied biomass pellets could be significantly reduced if the torrefaction process is integrated with AD
- …
