Jin Myoung Kim

Path renewal method in filtering based wireless sensor networks.

In applications of wireless sensor networks, there are many security issues. Attackers can create false reports and transmit the reports to the networks. These false reports can lead not only false alarms, but also the depletion of limited energy resources. In order to filter out such false reports during the forwarding process, Ye et al. proposed the statistical en-route filtering (SEF). Several research efforts to enhance the efficiency of SEF have been made. Especially, the path selection method proposed by Sun et al. can improve the detection power of SEF by considering the information on the filtering keys of and distances of upstream paths. However, such selection mechanism could lead to favored paths in heavy traffic, which would result in unbalanced energy consumption. In this paper, we propose a path renewal method to provide load balancing for sensor networks in terms of energy consumption. In our method, a node renews its upstream path to save energy resources if the remaining energy of and the communication traffic of the node exceed some threshold values. We show the effectiveness of the proposed method in terms of balanced energy consumption and filtering power by providing simulation results.

WiP Abstract: From Design to Operation of a Large-Scale CPS

CPS has broad spectrum of system features. A LCPS (Large-scale CPS) has a number of computing entities and physical systems including various sensors and actuators. The design and implementation of a LCPS must be more difficult and different from those of stand-alone CPS because it has more heterogeneity, more unreliability, more complexity and more unpredictability. Therefore, a LCPS must be developed under the systematic method in order to make fault-free control software at design time. In addition, LCPS requires control middleware supporting different or orthogonal QoS (Quality of Service) requirements of the subsystems composing LCPS.

A * -based key tree structure generation for group key management in wireless sensor networks

The application of wireless sensor networks to areas such as combat field surveillance, terrorist tracking and highway traffic monitoring requires secure communication among the sensor nodes within the networks. Logical key hierarchy (LKH) is a tree-based key management model which provides secure group communication. When a sensor node is added or evicted from the communication group, LKH updates the group key in order to ensure the security of the communications. In order to efficiently update the group key, we propose an A^*-based key tree structure, an extension to LKH, that reduces the number of re-key messages by considering the addition and eviction ratios of the history data. For the generation of the proposed key tree structure the A^* algorithm is applied, in which the branching factor at each level can take on different value. The experimental results demonstrate the efficiency of the proposed key tree structure against the existing key tree structures of fixed branching factors.

Location Based Hierarchical Secure Multicast Group Building in Wireless Sensor Networks

In large-scale wireless sensor networks, multicast is an important routing service for the efficient data distribution required for activities, such as filtering scheme updates, the redistribution of the cryptography keys and targeted queries. Especially, the redistribution of cryptography keys is important for the robust secure communication within the multicast group. In this paper, we propose a hierarchical secure multicast group building method. In order to build the groups, we exploit genetic algorithms by considering the location information of the sensor nodes. We show the efficiency of our proposal through simulation, in terms of the standard deviation among group members.

Secure Multicast Tree Structure Generation Method for Directed Diffusion Using A* Algorithms

The application of wireless sensor networks to areas such as combat field surveillance, terrorist tracking, and highway traffic monitoring requires secure communication among the sensor nodes within the networks. Logical key hierarchy (LKH) is a tree based key management model which provides secure group communication. When a sensor node is added or evicted from the communication group, LKH updates the group key in order to ensure the security of the communications. In order to efficiently update the group key in directed diffusion, we propose a method for secure multicast tree structure generation, an extension to LKH that reduces the number of re-keying messages by considering the addition and eviction ratios of the history data. For the generation of the proposed key tree structure the A* algorithm is applied, in which the branching factor at each level can take on different value. The experiment results demonstrate the efficiency of the proposed key tree structure against the existing key tree structures of fixed branching factors.

DEV&DESS-Based Real-Time Distributed Simulation Method Using DDS for Design Verification of Cyber-Physical Systems

CPS (cyber-physical systems) which consists of connected and diverse embedded systems and physical systems are a new paradigm. Traditional systems were usually considered to be passive and dumb parts in physical systems, but with CPS, we have to take into account what are being moved or changed in the physical systems. So, as increasing the complexity of CPS, potential errors in the systems also increase. In this paper, for enhancing the reliability of CPS, we exploit an executable-model-based design methodology and propose a distributed simulation method to verify the design of CPS. For the design of the systems including discrete and continuous factors, we apply DEV&DESS formalism and simulate models in distributed simulation environments through DDS middleware. We also illustrate the applications of CPS with our modeling tool.

A Study on Design of Communication Protocol for CPS Simulation

The term “cyber-physical system (CPS)” refers to a computing system that integrates physical processes and computational devices via a network. There are many physical and computational devices in a CPS, which can function automatically through inter-device interactions. Because a CPS is usually used for large-scale complex systems, to ensure reliable CPS operation, its design and execution should be verified through simulations. For CPS simulation, a communication protocol should be established for data transmission between physical systems and the corresponding simulation models during the simulation, including control algorithms for regulating differences between the two systems. First, because physical systems and simulation models are advanced in real time and logical time, respectively, time regulation methods should be included in the control algorithm. Second, to simulate various types of physical systems, a flexible simulation environment, independent of the operating environment such as the type of communication middleware, is required. In this paper, we propose a communication protocol for data transmission between physical systems and simulation models via a middle layer that contains the policies for handling the two different clocks of each system: virtual and real. The proposed communication protocol can be used not only for communication between the two systems but also for overcoming the problems caused by the differences in their operating environments. The contribution of this work is in that it defines a communication protocol and proposes methods for controlling different types of systems.

XML Representation of System Entity Structure for Distributed Modeling Simulation

Distributed simulation refers to the execution of a complex model on geographically dispersed simulators, and it can increase the speed of a simulation and eventually decrease the simulation execution time. The distributed simulation enables models to be executed in physically distributed position. The system entity structure (SES) is used to represent the structural relation of simulation models and there are several SES’s XML representation methods. To make use of the SES in a distributed simulation environment, the revision of existing XML representation is needed. In this paper, we propose revised XML representation for loading models dynamically in the distributed simulation environment. A template of XML representation is defined to meet a number of modeling requirements, and it shows the specific information of model’s hierarchy and coupling. Each simulator’s model loader analyzes the XML-based SES representations and loads information of a model dynamically. We validate our method using a coupled model example.

Simulation Modeling of TSK Fuzzy Systems for Model Continuity

This paper presents an approach to formally model Takagi–Sugeno–Kang (TSK) fuzzy systems without the use of any external components. In order to keep the model continuity, the formal simulation model for a TSK fuzzy system is comprised of three types of reusable sub-models involving primitive operations. Thus, the model can be executed even on limited computational platforms, such as embedded controllers.

Fuzzy based path renewal method in filtering based WSNs

Statistical en-route filtering scheme is proposed by Ye et al to detect and drop a fabricated report. In this paper, we propose a fuzzy based path renewal method.