Suleyman Uludag

Survey A survey of routing protocols for smart grid communications

With the recent initiatives to upgrade the existing power grid to the Smart Grid (SG), there has been a significant interest in the design and development of an efficient communications infrastructure for connecting different components of the SG. In addition to the currently used underlying networks and protocols, new wired/wireless approaches are being planned for deployment for different components/applications of the SG. Based on the data requirements of the applications, new challenges have arisen at the network layer of the protocol stack with respect to routing and data forwarding. In this paper, we focus on the routing issues in the SG communications infrastructure which consists of different network components, such as Home Area Networks (HANs), Neighborhood Area Networks (NANs) and Wide Area Networks (WANs). We provide a comprehensive survey of the existing routing research and analyze the advantages and disadvantages of the proposed protocols with respect different applications areas. We also identify the future research issues that are yet to be addressed with respect to the applications and network components. This survey is the first to identify routing design issues for the SG and categorize the proposed routing protocols from the SG applications perspective. We believe that this work will be valuable for the utilities and other energy companies whose target is to develop and deploy a specific SG application that may span different network components. In addition, this work will provide valuable insights for the newcomers who would like to pursue routing related research in the SG domain.

Distributed Recovery from Network Partitioning in Movable Sensor/Actor Networks via Controlled Mobility

Mobility has been introduced to sensor networks through the deployment of movable nodes. In movable wireless networks, network connectivity among the nodes is a crucial factor in order to relay data to the sink node, exchange data for collaboration, and perform data aggregation. However, such connectivity can be lost due to a failure of one or more nodes. Even a single node failure may partition the network, and thus, eventually reduce the quality and efficiency of the network operation. To handle this connectivity problem, we present PADRA to detect possible partitions, and then, restore the network connectivity through controlled relocation of movable nodes. The idea is to identify whether or not the failure of a node will cause partitioning in advance in a distributed manner. If a partitioning is to occur, PADRA designates a failure handler to initiate the connectivity restoration process. The overall goal in this process is to localize the scope of the recovery and minimize the overhead imposed on the nodes. We further extend PADRA to handle multiple node failures. The approach, namely, MDAPRA strives to provide a mutual exclusion mechanism in repositioning the nodes to restore connectivity. The effectiveness of the proposed approaches is validated through simulation experiments.

Internet packet loss: measurement and implications for end-to-end QoS

We analyze a month of Internet packet loss statistics for speech transmission using three different sets of transmitter/receiver host pairs. Our results indicate that packet loss is highly bursty, with the majority of individual losses occurring in a relatively small number of bursts. We find that loss exhibits dependence in most cases, but is not always well modeled as dependent. We introduce an analytical technique for measuring loss dependency. We also consider the asymmetry of round trip packet loss, and find that most loss on a round trip path occurs in either one direction or the other. We introduce a normalized metric for measuring loss asymmetry and apply it to our measurements. Finally we discuss the implications of our study for the next generation of real time voice services in the Internet.

Distributed Recovery of Actor Failures in Wireless Sensor and Actor Networks

Wireless sensor and actor networks (WSANs) additionally employ actor nodes within the wireless sensor network (WSN) which can process the sensed data and perform certain actions based on this collected data. In most applications, inter-actor coordination is required to provide the best response. This suggests that the employed actors should form and maintain a connected inter-actor network at all times. However, WSANs often operate unattended in harsh environments where actors can easily fail or get damaged. Such failures can partition the inter-actor network and thus eventually make the network useless. In order to handle such failures, we present a connected dominating set (CDS) based partition detection and recovery algorithm. The idea is to identify whether the failure of a node causes partitioning or not in advance. If a partitioning is to occur, the algorithm designates one of the neighboring nodes to initiate the connectivity restoration process. This process involves repositioning of a set of actors in order to restore the connectivity. The overall goal in this restoration process is to localize the scope of the recovery and minimize the movement overhead imposed on the involved actors. The effectiveness of the approach is validated through simulation experiments.

Analysis of Topology Aggregation techniques for QoS routing

We study and compare topology aggregation techniques used in QoS routing. Topology Aggregation (TA) is defined as a set of techniques that abstract or summarize the state information about the network topology to be exchanged, processed, and maintained by network nodes for routing purposes. Due to scalability, aggregation techniques have been an integral part of some routing protocols. However, TA has not been studied extensively except in a rather limited context. With the continuing growth of the Internet, scalability issues of QoS routing have been gaining importance. Therefore, we survey the current TA techniques, provide methodology to classify, evaluate, and compare their complexities and efficiencies.

Self-similarity of Internet packet delay

In this paper we present results which suggest that Internet packet delay, when viewed as a time series, is self-similar in nature. A self-similar phenomenon displays the same or similar statistical properties across a wide range of time scales. Self-similarity has previously been observed in the magnitude of traffic transmitted on local-area and wide-area networks. Our research is the first to explore the self-similarity of traffic delay rather than traffic magnitude. Our results imply that the delay experienced by application layer protocols is extremely bursty and that traditional Poisson models cannot accurately predict the degree of burstiness. Furthermore, we present evidence that the degree of self-similarity for a round-trip path in the Internet may be correlated with the packet loss observed on that path.

Implementing IT0/CS0 with scratch, app inventor forandroid, and lego mindstorms

The trend of declining enrollment and interest in computing fields, combined with increased demand from the industry, challenges instructors to come up with new, fresh and appealing methodologies to attract and retain students. Further, with the diffusion of information and computing technologies into almost all fields of study, introductory computing courses for non-majors need approaches that motivate students to feel comfortable with the life-long learning of computing concepts and tools. The goal of this paper is to summarize our teaching experience blending the aforementioned two needs into one course that may be considered as a type of CS0/IT0 course. With the pedagogical underpinnings stemming from constructionist learning and contextualized computing education, we present our motivation and the details of a course that uses the Scratch programming language, App Inventor for Android, and Lego Minstorm robotics.

A taxonomy and evaluation for developing 802.11-based wireless mesh network testbeds

The definition of wireless mesh networks (WMNs) has been used in the literature to connote and epitomize the ideal, ubiquitous, pervasive, and autonomic networking technology. An increasing interest has been emerging on the development of 802.11-based WMN testbeds to test the new ideas and approaches more realistically as opposed to relying solely on simulations. Although the developed testbeds have provided several insights to researchers for furthering the technology, there are still several issues that need to be addressed, particularly, with the approval of new standards, such as IEEE 802.11s, IEEE 802.11n, and IEEE 802.16, and upcoming protocols, such as IEEE 802.11ac, 802.11ad, 802.11ah, and 802.11af TV White Space efforts. In this paper, our goal is to provide a taxonomy and insightful guidelines for the creation of 802.11-based WMN testbeds as well as to identify several features that future WMN testbeds should possess. Utilizing these features, we evaluate the existing WMN testbeds. Finally, in addition to the existing WMN testbed experiments conducted at several layers of the protocol stack, we provide a list of open future research issues that can benefit from experiments on WMN testbeds. Copyright

Secure and Scalable Data Collection With Time Minimization in the Smart Grid

Deployment of data generation devices such as sensors and smart meters have been accelerating toward the vision of smart grid. The volume of data to be collected increases tremendously. Secure, efficient, and scalable data collection becomes a challenging task. In this paper, we present a secure and scalable data communications protocol for smart grid data collection. Under a hierarchical architecture, relay nodes [also known as data collectors (DCs)] collect and convey the data securely from measurement devices to the power operator. While the DCs can verify the integrity, they are not given access to the content, which may pave the way for third party providers to deliver value-added services or even the data collection itself. We further present optimization solutions for minimizing the total data collection time.

Teaching computing and programming fundamentals via App Inventor for Android

In this age of growing importance for interdisciplinary studies, the field of computing, and its indispensable component, programming, have become increasingly important not only for STEM areas but also for many other fields. Computational chemistry, bio-informatics, computational linguistics, computational toxicology, etc. are just a few examples of the crossover disciplines that benefit significantly from the developments in the computing and Information Technology (IT). Instructors are facing more challenges today than ever in trying to come up with new, fresh and appealing methodologies to attract and retain students in delivering computing and IT related topics to a much broader audience. Computing courses and topics both for majors and non-majors need new approaches that motivate students to feel comfortable with the lifelong learning of computing concepts and tools. The goal of this paper is to summarize our teaching experience in and the great potential of App Inventor for Android (AIA) in broadening the appeal and diffusion of fundamental computing and programming concepts. With a pedagogical foundation stemming from constructionist learning and contextualized computing education, we present our motivation and the details of courses that can greatly benefit from AIA.