Computer Science
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The Computer Science Department at Montana State University supports the Mission of the College of Engineering and the University through its teaching, research, and service activities. The Department educates undergraduate and graduate students in the principles and practices of computer science, preparing them for computing careers and for a lifetime of learning.
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Item Computing a consensus trajectory in a vehicular network(Springer Science and Business Media LLC, 2022-09) Zou, Peng; Qingge, Letu; Yang, Qing; Zhu, BinhaiIn this paper, we study the problem of computing a consensus trajectory of a vehicle given the history of Points of Interest visited by the vehicle over a certain period of time. The problem arises when a system tries to establish the social connection between two vehicles in a vehicular network, where three versions of the problem are studied. Formally, given a set of m trajectories, the first version of the problem is to compute a target (median) sequence T over Σ such that the sum of similarity measure (i.e., number of adjacencies) between T and all Si’s is maximized. For this version, we show that the problem is NP-hard and we present a simple factor-2 approximation based on a greedy method. We implement the greedy algorithm and a variation of it which is based on a more natural greedy search on a new data structure called adjacency map. In the second version of the problem where the sequence T is restricted to be a permutation, we show that the problem remains NP-hard but the approximation factor can be improved to 1.5. In the third version where the sequence T has to contain all letters of Σ, we again prove that it is NP-hard. We implement a simple greedy algorithm and a variation of the 1.5-approximation algorithm for the second version, and which are used to construct solution for the third version. Our algorithms are tested on the simulation data and the empirical results are very promising.Item An Architecture of Cloud-Assisted Information Dissemination in Vehicular Networks(2016-05) Binhai, Zhu; Wu, Shaoen; Yang, QingVehicular network technology allows vehicles to exchange real-time information between each other, which plays a vital role in the development of future intelligent transportation systems Existing research on vehicular networks assumes that each vehicle broadcasts collected information to neighboring vehicles, so that information is shared among vehicles. The fundamental problem of what information is delivered with which vehicle(s), however, has not been adequately studied. We propose an innovative cloud-assisted architecture to facilitate intelligent information dissemination among vehicles. Within the novel architecture, virtual social connections between vehicles are created and maintained on the cloud. Vehicles with similar driving histories are considered friends in a vehicular social network (VSN). The closeness of the relation between two vehicles in a VSN is then modeled by the three-valued subjective logic model. Based on the closeness between vehicles, only relevant information will be delivered to vehicles that are likely interested in it. The cloud-assisted architecture coordinates vehicular social connection construction, VSN maintenance, vehicle closeness assessment, and information dissemination.Item An empirical study of reliable networking for vehicular networks using IEEE 802.11n(Inderscience Publishers, Geneva, SWITZERLAND, 2014) Lee, Seungbae; Lim, Alvin; Yang, QingThe IEEE 802.11n technology is becoming more and more prevalent in wireless networks due to its significant enhancements in network performance. To examine whether the reliability of 802.11n is sufficient for vehicular networks, we conducted extensive experiments on inter-vehicle and intra-vehicle communications in vehicular environments. From this empirical study, we found that 802.11n provides high performance with stable throughput and reliable coverage in most cases. However, 802.11n protocols do not detect frequent changes of propagation and polarisation due to vehicle mobility and its rate adaptation algorithms improperly select multi-stream rates under channel fading conditions, although single-stream rates perform better. Moreover, an optimal antenna alignment that enables High Throughput (HT) operation using parallel data streams needs further investigation in vehicular environments. Our findings have profound implications on the protocol design and appropriate configuration for reliable networking in vehicular networks using 802.11n.Item Towards Trustworthy Vehicular Social Network(IEEE, 2015-06) Yang, Qing; Wang, HonggangWireless vehicular networks offer the promise of connectivity to vehicles that could provide a myriad of safety-and driving-enhancing services to drivers and passengers. With wireless technology available on each car, it is expected that huge amounts of information will be exchanged between vehicles or between vehicles and roadside infrastructure. Due to defective sensors, software viruses, or even malicious intent, legitimate vehicles might inject untrustworthy information into the network. Besides relying on the public key infrastructure (PKI), this article proposes a social network approach to study trustworthy information sharing in a vehicular network. We first cover recent research progress in measuring direct trust and modeling in direct trust in online social networks then discuss how to apply them to vehicular social networks despite several pressing research challenges.Item Cyber-Physical Systems for Water Sustainability: Challenges and Opportunities(IEEE, 2015) Wang, Zhaohui; Song, Houbing; Watkins, David W.; Ong, Keat Ghee; Xue, Pengfei; Yang, Qing; Shi, XianmingWater plays a vital role in the proper functioning of the Earth’s ecosystems, and practically all human activities, such as agriculture, manufacturing, transportation, and energy production. The proliferation of industrial and agricultural activities in modern society, however, poses threats to water resources in the form of chemical, biological, and thermal pollution. On the other hand, tremendous advancement in science and technology offers valuable tools to address water sustainability challenges. Key technologies, including sensing technology, wireless communications and networking, hydrodynamic modeling, data analysis, and control, enable intelligently wireless networked water Cyber-Physical Systems (CPS) with embedded sensors, processors, and actuators that can sense and interact with the water environment. This article will provide an overview of water CPS for sustainability from four critical aspects: sensing and instrumentation, communications and networking, computing, and control, and explore opportunities and design challenges of relevant techniques.Item Comparative Investigation on CSMA/CA-Based Opportunistic Random Access for Internet of Things(IEEE, 2014-01) Tang, Chong; Song, Lixing; Balasubramani, Jagadeesh; Wu, Shaoen; Biaz, Saad; Yang, Qing; Wang, HonggangWireless communication is indispensable to Internet of Things (IoT). Carrier sensing multiple access/collision avoidance (CSMA/CA) is a well-proven wireless random access protocol and allows each node of equal probability in accessing wireless channel, which incurs equal throughput in long term regardless of the channel conditions. To exploit node diversity that refers to the difference of channel condition among nodes, this paper proposes two opportunistic random access mechanisms: overlapped contention and segmented contention, to favor the node of the best channel condition. In the overlapped contention, the contention windows of all nodes share the same ground of zero, but have different upper bounds upon channel condition. In the segmented contention, the contention window upper bound of a better channel condition is smaller than the lower bound of a worse channel condition; namely, their contention windows are segmented without any overlapping. These algorithms are also polished to provide temporal fairness and avoid starving the nodes of poor channel conditions. The proposed mechanisms are analyzed, implemented, and evaluated on a Linux-based testbed and in the NS3 simulator. Extensive comparative experiments show that both opportunistic solutions can significantly improve the network performance in throughput, delay, and jitter over the current CSMA/CA protocol. In particular, the overlapped contention scheme can offer 73.3% and 37.5% throughput improvements in the infrastructure-based and ad hoc networks, respectively.Item ES-MPICH2: A Message Passing Interface with Enhanced Security(IEEE, 2012-01) Ruan, Xiaojun; Yang, Qing; Alghamdi, Mohammed I.; Yin, Shu; Qin, XiaoAn increasing number of commodity clusters are connected to each other by public networks, which have become a potential threat to security sensitive parallel applications running on the clusters. To address this security issue, we developed a Message Passing Interface (MPI) implementation to preserve confidentiality of messages communicated among nodes of clusters in an unsecured network. We focus on M PI rather than other protocols, because M PI is one of the most popular communication protocols for parallel computing on clusters. Our MPI implementation-called ES-MPICH2-was built based on MPICH2 developed by the Argonne National Laboratory. Like MPICH2, ES-MPICH2 aims at supporting a large variety of computation and communication platforms like commodity clusters and high-speed networks. We integrated encryption and decryption algorithms into the MPICH2 library with the standard MPI interface and; thus, data confidentiality of MPI applications can be readily preserved without a need to change the source codes of the MPI applications. MPI-application programmers can fully configure any confidentiality services in MPICHI2, because a secured configuration file in ES-MPICH2 offers the programmers flexibility in choosing any cryptographic schemes and keys seamlessly incorporated in ES-MPICH2. We used the Sandia Micro Benchmark and Intel MPI Benchmark suites to evaluate and compare the performance of ES-MPICH2 with the original MPICH2 version. Our experiments show that overhead incurred by the confidentiality services in ES-MPICH2 is marginal for small messages. The security overhead in ES-MPICH2 becomes more pronounced with larger messages. Our results also show that security overhead can be significantly reduced in ES-MPICH2 by high-performance clusters. The executable binaries and source code of the ES-MPICH2 implementation are freely available at http:// www.eng.auburn.edu/~xqin/software/es-mpich2/.Item ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios(Springer, 2010-02) Yang, Qing; Lim, Alvin; Li, Shuang; Fang, Jian; Agrawal, PrathimaMulti-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.Item Experimental Study: A LQI-Based Ranging Technique in ZigBee Sensor Networks(Inderscience Publishers, Geneva, SWITZERLAND, 2015) Yang, Ting; Yang, Qing; Cheng, LihuaRanging technology which estimates the distance between two communicating wireless nodes has been widely used as a necessary component in localization solutions for wireless sensor networks (WSN). LQI (Link Quality Indicator) is a metric introduced in IEEE 802.15.4 that measures the error in the incoming modulation of successfully received packets that pass the CRC (Cyclic Redundancy Check). Because of low system cost and less computational complexity, LQI-based ranging techniques are increasingly applied in Zigbee sensor networks. However, due to the environmental affects and electronic noise generated by hardware, raw LQI data could not be directly aligned with distances. To eliminate errors in LQI data and obtain higher ranging accuracy, we design and evaluate a novel LQI-based ranging technique which includes three essential data processing components: pre-correction, error compensation and mixed regression analysis. First, anchor nodes with known locations are used in pre-correction process to correct LQI measurements against the empirical regression function obtained from historical data. Then, error compensation is applied to eliminate the intrinsic error in LQI data. Finally, ranging results are refined by the mixed regression analysis. The proposed ranging technique is implemented and evaluated on a Zigbee sensor prototype Tarax. Experiment results show that the average ranging error is less than 1m, confirming that the proposed technique is able to achieve higher ranging accuracy and suitable for localization applications in WSN.Item Jamming and Anti-jamming Techniques in Wireless Networks: A Survey(Inderscience Publishers, Geneva, SWITZERLAND, 2014) Grover, Kanika; Lim, Alvin; Yang, QingBecause of the proliferation of wireless technologies, jamming in wireless networks has become a major research problem due to the ease in blocking communication in wireless networks. Jamming attacks are a subset of denial of service (DoS) attacks in which malicious nodes block legitimate communication by causing intentional interference in networks. To better understand this problem, we need to discuss and analyze, in detail, various techniques for jamming and anti-jamming in wireless networks. There are two main aspects of jamming techniques in wireless ad hoc networks: types of jammers and placement of jammers for effective jamming. To address jamming problem, various jamming localization, detection and countermeasure mechanisms are studied. Finally, we describe the open issues in this field, such as energy efficient detection scheme and jammer classification.