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Theses and Dissertations - Department of Computer Science

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Browsing Theses and Dissertations - Department of Computer Science by Subject "Electrical engineering"

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    Mult-radio vehicular communication and low data-rate traffic sensing network for intelligent transportation systems
    (University of Alabama Libraries, 2016) Zhao, Lei; Hong, Xiaoyan; University of Alabama Tuscaloosa
    Intelligent Transportation System (ITS) is the integration of advanced communication technologies into the transportation infrastructure and in vehicles. It is aimed to improve transportation safety and to enhance traffic management. Vehicular networks and traffic monitoring are two important research topics in ITS. Dedicated Short-Range Communications (DSRC) is a wireless communication standard specially designed for vehicular networks. DSRC provides traffic safety operations in vehicle-to-vehicle communications and vehicle-to-infrastructure communications with low communication latency and a long transmission rang of up to 1000 meters. Many possible applications are able to be implemented on DSRC. However, the insufficient capacity of a DSRC roadside unit limits the deployment of DSRC in cities. We propose a multi-radio DSRC scheme in this dissertation. Multi-radio technology can improve the safety characters of DSRC, and can increase DSRC bandwidth. Then we analyze and provide the antenna isolation requirement of multi-radio DSRC. The feasibility study in multi-radio DSRC will be discussed in this dissertation too. 40 percent of crashes occurred in the states were intersection-related crashes [76]. It is imperative to monitor intersections. Video cameras are deployed at main intersections for area surveillance, traffic monitoring, traffic light control, ticket issuing, crime fighting, etc. However, the hardware deployment, data transmission, data storage, and real-time data processing of each video camera cost a lot of money. Traffic cameras are only deployed at a few main intersections in most cities. We propose a low cost low data-rate pyroelectric sensing system to monitor non-camera-monitored intersections. A high dynamic signal conditioning circuit for pyroelectric sensor is implemented and tested to detect vehicles. We also propose and evaluate a hierarchical wireless mesh network structure for the pyroelectric sensing system.
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    Protocol design in wireless networks: featuring channel access and vehicular communications
    (University of Alabama Libraries, 2012) Hoque, Mohammad Asadul; Hong, Xiaoyan; Dixon, Brandon; University of Alabama Tuscaloosa
    Wireless Networks provide a very cost efficient solution for data connectivity over wide areas enabling ubiquitous computing environment through multi-hop relay. The scope of this dissertation encompasses two correlated domains of Wireless Network area, one is the Multi-Radio Multi-Channel Wireless Mesh Network (MRMC-WMN) and the other is Vehicular Ad hoc Network (VANET). The research issues studied here are related to IEEE 802.11 based, multi-hop ad hoc wireless network. In the first part, we deal with some of the fundamental issues of Wireless Networks, with particular emphasis given on approaches and techniques for channel assignment and delay analysis in multi-radio multi-channel wireless mesh network. A novel channel assignment scheme has been proposed utilizing Partially Overlapped Channel (POC).We also introduced the notion of I-Matrix as a new interference model which takes into account one additional type of channel interference ignored by most researchers. Specifically, our interference model considers the effect of Self-Interference for multi-radio environment in addition to Adjacent Channel Interference(ACI) and Co-Channel Interference. We evaluate the performance of our POC based channel assignment algorithm in terms of capacity by comparing with the one using only orthogonal channels. Our results show capacity improvement as the increased link assignments at an average of more than 15 percent. The second part presents a spatio-temporal analysis of multi-hop V2V connectivity and network partitioning along with the statistical behavior of urban taxi mobility pattern. We developed two new approaches in analyzing the connectivity. One is the bitwise matrix manipulation for determining multi-hop connectivity and transitive closure. The other is the detection of saturated connectivity based on the k-hop reachability. The proposed algorithm of generating multi-hop reachability and network partition, though not optimal in performance, is better than traditional BFS approach in terms of space and time complexity. We then apply our algorithm for spatio-temporal analysis of urban taxi mobility pattern. Using the presented empirical analyses, wireless researchers can estimate the capabilities and constraints of vehicular communication from connectivity and mobility patterns as well as government can plan and work on issues related to implementing proper DSRC infrastructure for optimal data connectivity in urban area. We also propose an innovative application of V2X communication for Intelligent Transportation System (ITS). The application relates to DSRC based taxi hailing system in urban metropolitan area. The proposed system can work in both presence and absence of ITS infrastructure. Our evaluation results show that the system can not only reduce the passenger's waiting time and driver's empty cruise time, but also increase the overall taxi availability using multi-hop communication.