Wenye Wang

Mobility management in next-generation wireless systems

This paper describes current and proposed protocols for mobility management for public land mobile network (PLMN)-based networks, mobile Internet protocol (IP) wireless asynchronous transfer mode (ATM) and satellite networks. The integration of these networks will be discussed in the context of the next evolutionary step of wireless communication networks. First, a review is provided of location management algorithms for personal communication systems (PCS) implemented over a PLMN network. The latest protocol changes for location registration and handoff are investigated for mobile IP followed by a discussion of proposed protocols for wireless ATM and satellite networks. Finally, an outline of open problems to be addressed by the next generation of wireless network service is discussed.

Survey Paper: A survey on the communication architectures in smart grid

The next-generation electric power systems (smart grid) are studied intensively as a promising solution for energy crisis. One important feature of the smart grid is the integration of high-speed, reliable and secure data communication networks to manage the complex power systems effectively and intelligently. We provide in this paper a comprehensive survey on the communication architectures in the power systems, including the communication network compositions, technologies, functions, requirements, and research challenges. As these communication networks are responsible for delivering power system related messages, we discuss specifically the network implementation considerations and challenges in the power system settings. This survey attempts to summarize the current state of research efforts in the communication networks of smart grid, which may help us identify the research problems in the continued studies.

Survey Cyber security in the Smart Grid: Survey and challenges

The Smart Grid, generally referred to as the next-generation power system, is considered as a revolutionary and evolutionary regime of existing power grids. More importantly, with the integration of advanced computing and communication technologies, the Smart Grid is expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources, as well as distributed intelligence and demand response. Along with the silent features of the Smart Grid, cyber security emerges to be a critical issue because millions of electronic devices are inter-connected via communication networks throughout critical power facilities, which has an immediate impact on reliability of such a widespread infrastructure. In this paper, we present a comprehensive survey of cyber security issues for the Smart Grid. Specifically, we focus on reviewing and discussing security requirements, network vulnerabilities, attack countermeasures, secure communication protocols and architectures in the Smart Grid. We aim to provide a deep understanding of security vulnerabilities and solutions in the Smart Grid and shed light on future research directions for Smart Grid security.The Smart Grid, generally referred to as the next-generation power system, is considered as a revolutionary and evolutionary regime of existing power grids. More importantly, with the integration of advanced computing and communication technologies, the Smart Grid is expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources, as well as distributed intelligence and demand response. Along with the silent features of the Smart Grid, cyber security emerges to be a critical issue because millions of electronic devices are inter-connected via communication networks throughout critical power facilities, which has an immediate impact on reliability of such a widespread infrastructure. In this paper, we present a comprehensive survey of cyber security issues for the Smart Grid. Specifically, we focus on reviewing and discussing security requirements, network vulnerabilities, attack countermeasures, secure communication protocols and architectures in the Smart Grid. We aim to provide a deep understanding of security vulnerabilities and solutions in the Smart Grid and shed light on future research directions for Smart Grid security. 2013 Elsevier B.V. All rights reserved.

A dynamic location management scheme for next-generation multitier PCS systems

Global wireless networks enable mobile users to communicate regardless of their locations. One of the most important issues is location management in a highly dynamic environment because mobile users may roam between different wireless systems, network operators, and geographical regions. A location-tracking mechanism is introduced that consists of intersystem location updates and intersystem paging. Intersystem update is implemented by using the concept of boundary location area, which is determined by a dynamic location update policy in which the velocity and the quality of service are taken into account on a per-user basis. Also, intersystem paging is based on the concept of a boundary location register, which is used to maintain the records of mobile users crossing the boundary of systems. This mechanism not only reduces location-tracking costs, but also significantly decreases call-loss rates and average-paging delays. The performance evaluation of the proposed schemes is provided to demonstrate their effectiveness in multitier personal communication systems.

The predictive user mobility profile framework for wireless multimedia networks

User mobility profile (UMP) is a combination of historic records and predictive patterns of mobile terminals, which serve as fundamental information for mobility management and enhancement of quality of service (QoS) in wireless multimedia networks. In this paper, a UMP framework is developed for estimating service patterns and tracking mobile users, including descriptions of location, mobility, and service requirements. For each mobile user, the service requirement is estimated using a mean-square error method. Moreover, a new mobility model is designed to characterize not only stochastic behaviors, but historical records and predictive future locations of mobile users as well. Therefore, our approach incorporates aggregate history and current system parameters to acquire UMP. In particular, an adaptive algorithm is designed to predict the future positions of mobile terminals in terms of location probabilities based on moving directions and residence time in a cell. Simulation results are shown to indicate that the proposed schemes are effective on mobility and resource management by evaluating blocking/dropping probabilities and location tracking costs in wireless networks.

Review and evaluation of security threats on the communication networks in the smart grid

The smart grid, generally referred to as the next-generation power electric system, relies on robust communication networks to provide efficient, secure, and reliable information delivery. Thus, the network security is of critical importance in the smart grid. In this paper, we aim at classifying and evaluating the security threats on the communication networks in the smart grid. Based on a top-down analysis, we categorize the goals of potential attacks against the smart grid communication networks into three types: network availability, data integrity and information privacy. We then qualitatively analyze both the impact and feasibility of the three types of attacks. Moreover, since network availability is the top priority in the security objectives for the smart grid, we use experiments to quantitatively evaluate the impact of denial-of-service (DoS) attacks on a power substation network. Our work provides initial experimental data of DoS attacks against a power network and shows that the network performance degrades dramatically only when the DoS attack intensity approaches to the maximum.

ART: an asymmetric and reliable transport mechanism for wireless sensor networks

Existing solutions for reliable data transmission in wireless networks are aimed to offer reliable message or per transport segment delivery. However, densely deployed sensor nodes can generate many redundant messages that essentially indicate the same event from the area of interest, thus this message-level reliability can pose significantly high and unnecessary communication overhead. In this paper, we address the reliability problem by defining event reliability and query reliability to reduce extra cost of reliable transport services. Unlike other studies on transport protocols for Wireless Sensor Networks (WSN), we consider event delivery in conjunction with query delivery. For the purpose, we propose an energy-aware sensor classification algorithm to construct a network topology that is composed of sensors in providing desired level of event and query reliability. We evaluate the performance of the proposed approach and conclude that significant savings on communication costs are attainable while achieving event and query reliability.

Effective paging schemes with delay bounds as QoS constraints in wireless systems

In this paper new paging schemes are presented for locating mobile users in wireless networks. Paging costs and delay bounds are considered since paging costs are associated with bandwidth utilization and delay bounds influence call setup time. In general, location tracking schemes require intensive computation to search for a mobile terminal in current PCS networks. To reduce the paging costs, three new paging schemes, reverse, semi-reverse and uniform, are introduced to provide a simple way of partitioning the service areas and decrease the paging costs based on each mobile terminals location probability distribution. Numerical results demonstrate that our approaches significantly reduce the paging costs for various probability distributions such as uniform, truncated discrete Gaussian, and irregular distributions.

Intersystem location update and paging schemes for multitier wireless networks

Global wireless networks enable mobile users to communicate regardless of their locations. One of the most important issues is location management in a highly dynamic environment because mobile users may roam between different wireless networks, network operators, and geographical regions. In this paper, a location tracking mechanism is introduced, which consists of intersystem location updates using the concept of boundary location area (BLA) and paging using the concept of boundary location register (BLR). The BLA is determined by a dynamic location update policy in which the velocity and the quality of service (QoS) are taken into account on a per-user basis. The BLR is used to maintain the records of mobile users crossing the boundary of networks. This mechanism not only reduces location tracking costs but also significantly decreases call loss rates and average paging delays. The performance evaluation of the proposed schemes is provided to demonstrate their effectiveness in multitier wireless networks.

An Empirical Study of Communication Infrastructures Towards the Smart Grid: Design, Implementation, and Evaluation

The smart grid features ubiquitous interconnections of power equipments to enable two-way flows of electricity and information for various intelligent power management applications, such as accurate relay protection and timely demand response. To fulfill such pervasive equipment interconnects, a full-fledged communication infrastructure is of great importance in the smart grid. There have been extensive works on disparate layouts of communication infrastructures in the smart grid by surveying feasible wired or wireless communication technologies, such as power line communications and cellular networks. Nevertheless, towards an operable, cost-efficient and backward-compatible communication solution, more comprehensive and practical understandings are still urgently needed regarding communication requirements, applicable protocols, and system performance. Through such comprehensive understandings, we are prone to answer a fundamental question, how to design, implement and integrate communication infrastructures with power systems. In this paper, we address this issue in a case study of a smart grid demonstration project, the Future Renewable Electric Energy Delivery and Management (FREEDM) systems. By investigating communication scenarios, we first clarify communication requirements implied in FREEDM use cases. Then, we adopt a predominant protocol framework, Distributed Network Protocol 3.0 over TCP/IP (DNP3 over TCP/IP), to practically establish connections between electric devices for data exchanges in a small-scale FREEDM system setting, Green Hub. Within the real-setting testbed, we measure the message delivery performance of the DNP3-based communication infrastructure. Our results reveal that diverse timing requirements of message deliveries are arguably primary concerns in a way that dominates viabilities of protocols or schemes in the communication infrastructure of the smart grid. Accordingly, although DNP3 over TCP/IP is widely considered as a smart grid communication solution, it cannot satisfy communication requirements in some time-critical scenarios, such as relay protections, which claim a further optimization on the protocol efficiency of DNP3.