Davut Incebacak

Optimal number of routing paths in multi-path routing to minimize energy consumption in wireless sensor networks

In wireless sensor networks, multi-path routing is proposed for energy balancing which prolongs the network lifetime as compared to single-path routing where utilization of a single route between a source node and the base station results in imbalanced energy dissipation. While it is evident that increasing the number of routing paths mitigates the problem of energy over-utilization in a subset of nodes acting as relays, the net effect of the proliferation of multiple routing paths on energy balancing remains unclear. It is imperative to keep the number of routing paths as low as possible without significantly deteriorating the network lifetime; therefore, determination of the optimal number of routing paths in multi-path routing by considering the tradeoff in routing complexity and network lifetime extension is an interesting research problem. In this study, to investigate the impact of the number of routing paths in multi-path routing on network-wide energy balancing under optimal operating conditions, we build a novel mixed integer programming framework. We explore the parameter space consisting of a number of paths, number of nodes, maximum transmission range, network area, and network topology. The results of the analysis show that by utilizing the optimization scheme proposed, it is possible to achieve near-optimal energy consumption (within 1.0% neighborhood of the case where no restrictions are imposed on the number of routing paths in multi-path routing) using at most two paths for each node.

The impact of link unidirectionality and reverse path length on wireless sensor network lifetime

The occurrence of unidirectional links in wireless sensor networks (WSNs) is an inherent feature of wireless communication. Transceiver characteristics, asymmetric interference, and many other properties of the electromagnetic propagation environment result in link unidirectionality, however, transmission power heterogeneity is the dominant factor that creates unidirectional links. Most of the data transfer mechanisms designed for wireless networks work only on bidirectional links, yet, there are some mechanisms capable of utilizing unidirectional links. Employment of a multi-hop reverse path for acknowledgement delivery is the key concept and hop length of the reverse path is an important design criterion in such mechanisms. If the maximum reverse path length is allowed to take large values then the number of usable unidirectional links increases. Increasing the number of available links leads to better energy balancing and longer network lifetime. But is it necessary to keep the reverse path length large to achieve the maximum network lifetime possible? In this study, we investigate the effects of reverse path length in WSNs with unidirectional links induced by transmission power heterogeneity on network lifetime through a novel mixed integer programming framework. Our results show that reverse path length has significant impact on WSN lifetime.

Investigating the Tradeoffs between Spatial Granularity and Energy Requirements in Wireless Sensor Networks

In some wireless sensor network applications like precision agriculture, the network area is divided into a number of well-defined regions (spatial granules) and for each spatial granule a separate measurement is made. In performing the task of collecting the data pertaining to these measurements, there is an inherent tradeoff between number of spatial granules and minimum energy requirements of sensor nodes deployed in the area. In this paper, through a linear programming (LP) framework, we investigate the impact of spatial granularity of measurements on the energy requirements of sensor network. Once redundancy is defined in this context as the duplication of data collected for each granule, our LP model also allows us to determine almost achievable performance benchmarks in idealized yet practical settings which are achievable when redundancy is totally eliminated.

The impact of scalable routing on lifetime of smart grid communication networks

Abstract The paradigm of sensors organized in a multi-hop wireless network has been recognized as a cost effective way to satisfy the real-time sensing and communication needs of a smart grid. For wireless sensor networks, one of the most important design goals is the maximization of network lifetime. Scalability, on the other hand, is also of utmost importance for any given network design problem and especially in a wide area smart grid deployment scenario. Improving scalability requires the network flows to be more localized, however, localizing network operations works against the utilization of some optimal paths required for load balancing and lifetime prolonging. Therefore, lifetime maximization and scalability are two design criteria acting against each other. In this study, a characterization of achievable network lifetime as a function of level of localization of the routing operations under optimal conditions is performed using three localized routing approaches. We build a novel Mixed Integer Programming (MIP) framework with a special emphasis on the details of energy dissipation terms in sensor nodes to model the network behavior correctly. Numerical analysis performed using the developed MIP framework enables us to quantify the impact of different levels of route localization on network lifetime.

Effects of handshake hop length of unidirectional links on the lifetime of wireless sensor networks

Most of the data transfer mechanisms designed for wireless sensor networks (WSNs) work only on bidirectional links, yet, there are some mechanisms capable of utilizing unidirectional links which have been caused by transmission power heterogeneity. Employment of a multi-hop reverse path for acknowledgement delivery is the key concept in these designs. If the maximum reverse path length is allowed to take larger values then the number of usable unidirectional links increases. Increasing the number of available links leads to better energy balancing and longer network lifetime. But is it necessary to keep the reverse path length large to achieve maximum network lifetime possible? In this study, we investigate the effects of reverse path length in WSNs with unidirectional links induced by transmission power heterogeneity on network lifetime through a novel mixed integer programming (MIP) framework. Our results show that reverse path length has significant impact on WSN lifetime.

Network lifetime maximization and localized routing tradeoff in wireless sensor networks

Maximization of lifetime is one of the most important design goals in Wireless sensor networks (WSN). On the other hand, for any given network design problem scalability is also of utmost importance. Yet, these two design goals are acting against each other. In this study, a characterization of achievable network lifetime as a function of the degree of localization of the routing operations under ideal conditions by using three localized routing approaches is performed. We built a novel linear programming framework to model the network behavior and by using the framework sampled the parameter space.

Energy Cost of Mitigating Physical Attacks in Wireless Sensor Networks

Physical attacks, which aim to render one or more sensor nodes non-operational by physically capturing and destroying them, are among the most serious security threats in Wireless Sensor Networks (WSNs). In case of dense deployment (a desirable property in the design of WSNs) multiple sensor nodes acquire redundant (highly correlated) data. As a result, even if some nodes are dead, the remaining nodes can successfully complete the sensing task. However, as the number of nodes in the network decreases, the remaining nodes are burdened with the extra load (energy dissipation). In this study, we investigate the energy cost of survivability in the presence of physical attacks through a novel Linear Programming framework. We explore the energy dissipation characteristics of the network for different physical attack scenarios.

Work in progress - iterative curriculum development for an interdisciplinary online-taught IT course

Today, students acquire basic computer skills at the early stages of their lives through several courses taken at schools before university and social online environments where they can engage with their friends. As a result, students may become more reluctant to attend similar courses in universities. A similar situation has arisen recently with a service course, which is given to all first year undergraduate students in METU. A survey conducted two years ago showed that most students already acquire skills in basic word processing and spreadsheet tools before they have started their studies in the university. Therefore, a revision of the contents was required. After working with educators, librarians and looking into several curriculums, a new course outline was formed. This paper explains the motivations, experiences and outcome of developing a brand new curriculum for a first year course, which aims to make student computer and information literate.

Towards Trustable Digital Evidence with PKIDEV: PKI Based Digital Evidence Verification Model

How to Capture and Preserve Digital Evidence Securely? For the investigation and prosecution of criminal activities that involve computers, digital evidence collected in the crime scene has a vital importance. On one side, it is a very challenging task for forensics professionals to collect them without any loss or damage. On the other, there is the second problem of providing the integrity and authenticity in order to achieve legal acceptance in a court of law. By conceiving digital evidence simply as one instance of digital data, it is evident that modern cryptography offers elegant solutions for this second problem. However, to our knowledge, there is not any previous work proposing a systematic model having a holistic view to address all the related security problems in this particular case of digital evidence verification. In this paper, we present PKIDEV (Public Key Infrastructure based Digital Evidence Verification model) as an integrated solution to provide security for the process of capturing and preserving digital evidence. PKIDEV employs, inter alia, cryptographic techniques like digital signatures and secure time-stamping as well as latest technologies such as GPS and EDGE. In our study, we also identify the problems public-key cryptography brings when it is applied to the verification of digital evidence.