@conference {
	title = {HybridSim: A Modeling and Co-simulation Toolchain for Cyber-Physical Systems},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {10/2013},
	abstract = {Cyber-physical systems (CPS) involve communication networks, computation algorithms, control systems and physical systems. Many CPS, such as Smart Buildings, are subject to very expensive deployment costs and complex network interactions. Thus comprehensive modeling and simulation of such systems are crucial to ensure that they function as intended before deployment. Given the multi-domain nature of CPS, it is more appropriate to use a heterogeneous simulation environment to study system dynamics. In this paper, we design and implement an integrated modeling and co-simulation toolchain, called HybridSim, for the design and simulation of CPS. Firstly, HybridSim can transform and import existing system components from multi-domains into SysML, which enables systems engineers to design CPS with only these imported SysML blocks. Secondly, HybridSim can generate Functional Mock-up Units (FMUs) and configuration scripts directly from SysML designs. Finally, HybridSim can co-simulate these FMUs according to the Functional Mock-up Interface standard to synchronize their corresponding simulators and exchange information between them. We demonstrate the convenience and efficiency of HybridSim using a comprehensive hydronic heating system model for Smart Buildings as the case study to investigate the impact of packet loss and sampling rate introduced by the communication network.},
	address = {Delft, Netherlands},
	booktitle = {Proceedings of 17th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications},
	pages = {pp. 33-40}
}
@conference {
	title = {Storage-centric Sensor Networks for Smart Buildings},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {In my thesis, I propose a model-based systems design framework, called WSNDesign, to facilitate the design and implementation of wireless sensor networks (WSNs). WSNDesign provides a hierarchy of model libraries to model various behaviors and structures of WSNs in the context of Smart Buildings, and introduces a system design flow to compose both continuous-time and event-triggered modules to develop applications with support for performance evaluation. In order to handle various sensor data efficiently, WSNDesign provides a distributed database system, called HybridDB, for data collection and retrieval. HybridDB enables sensors to store large-scale datasets in situ on local NAND ash using a novel resource-aware data storage system, and can process typical queries inWSNs extremely efficiently. In addition, HybridDB supports incremental -approximate querying that enables clients to retrieve a just-sufficient set of sensor data by issuing refinement and zoom-in sub-queries to search events and analyze sensor data efficiently. HybridDB can always return an approximate dataset with guaranteed L1-norm error bound.},
	address = {Philadelphia, PA},
	booktitle = {12th ACM/IEEE Conference on Information Processing in Sensor Networks IPSN 2013}
}
@conference {
	title = {Interactive Tree Decomposition Tool for Reducing System Analysis Complexity},
	author = {Yang, Shahan., Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {We present a graphical tool for the calculation of treewidth, a metric on the parametric structure of a system that is intimately tied to the complexity of system analysis. For many graphically describable systems, such as systems of parametric equations, as in a SysML Parametric diagram, or Bayesian networks or even mind maps and writing term papers, analysis of the system is exponential in treewidth and linear in system size. A tool facilitating comprehensive analysis can serve to bring competitive advantage to a systems engineering workflow by reducing costly unanticipated behaviors. Furthermore, a byproduct of computing treewidth is a framework for enumerating computationally compatible distributed algorithms. In this paper, we pose this NP-complete problem from the perspective of finding satisficing solutions, exposing choices that can influence the complexity of the resulting system to the designer. A designer can contribute two important things to the structure of the system: a visual intuition about the relationships between the underlying objects and the ability to change the relationships themselves at design time to reduce analysis complexity. Having a visual tool that provides instant feedback will help designers achieve an intuitive grasp of the relationship between design decisions and system complexity. As complexity is the root of almost every systems engineering problem, and also something not easily understood, incorporating complexity analysis into a design process should improve resulting system designs. The tool uses a randomized, anytime algorithm for interactive optimization of treewidth. It presents a sequence of choices to a designer and incrementally lowers an upper bound on system treewidth over time. This algorithm is novel, as few algorithms are targeted at interactivity with a human user. We present a number of simple examples for using the tool. We show how our tool helps to decompose some example systems, including a quadrotor optimization, a sensor network optimization, a Bayesian network, and a mind map.},
	address = {Atlanta, GA},
	booktitle = {Conference on Systems Engineering Research (CSER{\textquoteright}13),},
	pages = {pp. 138-147}
}
@conference {
	title = {HybridStore: An Efficient DataManagement System for Hybrid Flash-based Sensor Devices},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {In this paper, we propose HybridStore, a novel efficient resourceaware data management system for flash-based sensor devices to store and query sensor data streams. HybridStore has three key features. Firstly, it takes advantage of the on-board random-accessible NOR flash in current sensor platforms to guarantee that all NAND pages used by it are fully occupied and written in a purely sequential fashion, and expensive in-place updates and out-of-place writes to an existing NAND page are completely avoided. Thus, both raw NAND flash chips and FTL-equipped (Flash Translation Layer) flash packages can be supported efficiently. Secondly, HybridStore can process typical joint queries involving both time windows and key value ranges as selection predicate extremely efficiently, even on large-scale datasets. It organizes a data stream into segments and exploits a novel index structure that consists of the inter-segment skip list, and the in-segment β-Tree and Bloom filter of each segment. Finally, HybridStore can trivially support time-based data aging without any extra overhead because no garbage collection mechanism is needed. Our implementation and evaluation with a large-scale real-world dataset in TinyOS reveals that HybridStore can achieve remarkable performance at a small cost of constructing the index.},
	address = {Ghent, Belgium},
	booktitle = {10th European Conference on Wireless Sensor Networks},
	pages = {pp. 50-66}
}
@conference {
	title = {Minimizing Aggregation Latency under the Physical Interference Model in Wireless Sensor Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2012},
	month = {11/2012},
	abstract = {Wireless Sensor Networks (WSNs) have been widely~recognized as a promising technology that can enhance various~aspects of today{\textquoteright}s electric power systems, making them a vital~component of the smart grid. Efficient aggregation of data~collected by sensors is crucial for a successful WSN-based smart~grid application. Existing works on the Minimum Latency Aggregation~Scheduling (MLAS) problem in WSNs usually adopt the~protocol interference model, which is a tremendous simplification~of the physical reality faced in wireless networks. In contrast,~the more realistic physical interference model has been proved~to have the potential to increase the network capacity. In this~paper, we propose a distributed algorithm to minimize the data~aggregation latency under the physical interference model, which~jointly considers routing, power assignment and transmission~scheduling.~},
	address = {Tainan City , Taiwan},
	booktitle = {Third International Conference on Smart Grid Communications (IEEE SmartGridComm 2012)},
	pages = {pp. 19-24}
}
@conference {
	title = {Integrated Modeling and Simulation Framework for Wireless Sensor Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2012},
	month = {06/2012},
	abstract = {Existing ad hoc system design methods for Wireless Sensor Networks (WSNs) suffer from lack of reusability. In addition, the interactions between the continuous-time physical environments and WSNs have not been well studied. In this paper, we propose a model-based systems design (MBSD) framework for WSNs, which is a systematic methodology applying systems engineering principles to enhance model reusability and collaborations among multiple modeling domains. Firstly, we describe a hierarchy of model libraries to model various behaviors and structures of WSNs, including physical environments, physical platforms, communication and computation components, system services and applications. Based on the MBSD framework, we introduce a system design flow to compose both continuoustime and event-triggered modules to develop applications with support for performance study by simulations. Next, we briefly describe the main modules for physical platforms, the Media Access Control (MAC) layer, wireless channels and physical environments, which are developed using the Systems Modeling Language (SysML), Simulink and Modelica. Finally, we use a building thermal control system as the case study to demonstrate the composability, reusability and flexibility of the proposed MBSD framework.},
	address = {Toulouse, France},
	booktitle = {21st IEEE International Conference on Collaboration Technologies and Infrastructures (WETICE 2012- CoMetS track)},
	pages = {pp. 268-273}
}
@conference {
	title = {Performance Analysis of Time-Critical Peer-to-Peer Communications in IEEE 802.15.4 Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {Existing works on the performance analysis of IEEE 802.15.4 networks with peer-to-peer (P2P) topologies assume the non-beacon unslotted mode in the MAC layer, which is not suitable for time-critical communications required by many applications, such as control, actuation and monitoring applications. In this paper, we introduce an enhanced guaranteed timeslot (GTS) mechanism which can support time-critical P2P communications in wireless sensor networks (WSNs). A Markov chain that takes into account retransmission limits, acknowledgements, unsaturated traffic and packet delivery ratios of links is proposed to model P2P communications using this enhanced GTS mechanism. Based on this model, we analyze the expected reliability and energy consumptions under various traffic conditions. In addition, the impacts of MAC parameters on these performance indexes are analyzed. Monte Carlo simulations show that our theoretical analysis is quite accurate, and thus can be used as guidance for networks configuration in WSNs.},
	address = {Kyoto, Japan},
	booktitle = {IEEE International Conference on Communications (ICC 2011)},
	pages = {pp. 1-6}
}
@conference {
	title = {Studying Real-time Traffic in Multi-hop Networks Using the EMANE Emulator: Capabilities and Limitations},
	author = {Jain, Kaustubh., Roy-Chowdhury, Ayan., Somasundaram, Kiran K., Wang, Baobing., Baras, John S.},
	year = {2011},
	month = {03/2011},
	abstract = {In this paper, we provide an open-source software emulator setup for MANETs and study its fidelity in providing reliable performance estimates for real-time traffic. We emulate the IEEE 802.11 MAC/PHY (DCF) using the EMANE software emulator deployed on a cluster and run experiments for different multi-hop wireless scenarios. As an instance, we study the performance of real-time streaming media over a mesh network supported by OLSR. We also use the setup to analyze the impact of the wireless network on the self-similarity of the traffic.},
	address = {Barcelona, Spain},
	booktitle = {SIMUTools 2011- 4th International Conference on Simulation Tools and Techniques},
	pages = {pp. 93-95}
}
