Browsing by Author "Dr. Wenye Wang, Committee Chair"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Performance Evaluation of Handoff between UMTS/802.11b based on Mobile IP and Stream Control Transmission Protocol
    (2005-08-18) Song, Jung Kee; Dr. Wenye Wang, Committee Chair; Dr. David Thuente, Committee Member; Dr. Arne A. Nilsson, Committee Member
    Various wireless networks, contemporarily, have evolved as prime communication methods, encountering convergence paradigm among heterogeneous technologies including applications based on IP, which has given enormous impacts in our way of life because of its proved robustness and scalability as well as ample services. With the synergy of the two technologies, ubiquitous access to all-IP information sources has become reality. For wireless IP services, IP mobility is one of the major issues that should be resolved. Especially, the performance of handoff mechanism is a pithy issue that determines the performance of application level services. Although Mobile IP (MIP) and its extensions, as network layer solutions, have been proposed and standardized, their handoff mechanisms bring unavoidable transmission throughput degradation due to packet loss, registration delay, and transport layer blocking. Moreover, to accommodate MIP, significant quantity of modifications should be brought into each heterogeneous network architecture. In this thesis, we evaluate the performance of a transport layer handoff approach, mobile SCTP (mSCTP), and compare it with that of a network layer solution, MIP. mSCTP is based on Stream Control Transmission Protocol (SCTP), the third general purpose transport layer protocol, standardized by IETF. SCTP conceptually enables seamless handoff in transport layer without any change in IP protocol stack by its multi-homing feature and dynamic address reconfiguration (DAR) extension. We analyze the performance of mSCTP and MIP by introducing handoff delay, end-to-end transmission throughput, and packet loss, and conduct a simulation study of the two protocols in 802.11b WLAN-only and UMTS/802.11b integrated networks using NS-2 network simulator.
  • No Thumbnail Available
    Understanding the Performance and Resilience of Large-Scale Multi-Hop Wireless Networks
    (2010-04-29) Xu, Yi; Dr. Khaled Harfoush, Committee Member; Dr. Yannis Viniotis, Committee Member; Dr. Arne A. Nilsson, Committee Member; Dr. Wenye Wang, Committee Chair
    Wireless networks are becoming an important supplementary technology to the traditional wired networks. They offer convenient and flexible network access for the users to communicate with each other. However, wireless networks confront many technical challenges that limit their full utilization. Especially in large-scale multi-hop networks, the communication quality received by each user depends highly on the cooperation of other users in the network, which is constrained by many factors such as the heterogeneity of user communication devices, the limited availability of radio bandwidth, the difficulty in user coordinations, the mobility of users, and the failure of user devices. We intend to understand the performance and resilience of large-scale multi-hop wireless networks in this dissertation, which will help us utilize the wireless networks effectively, efficiently and reliably. We identify four fundamental performance and resilience aspects to investigate, namely, the information propagation speed, the communication capacity, the topological stability, and the failure resilience. The study on the first two perspectives attempts to minimize the delay and maximize the capacity of large wireless networks, while the study on the last two perspectives evaluates and mitigates the impact of user mobility and failure on the network structure. Specifically, we make the following contributions toward improving the utilization of large-scale wireless networks. First, we have determined the maximum information propagation speed in wireless networks and designed a new routing algorithm to identify the minimum transmission delay path for fastest information delivery. Second, we have demonstrated that the maximum network capacity can be obtained by scheduling user transmissions in localized areas and proposed a practical solution for capacity maximization. Third, we have analyzed the network topological stability with presence of user mobility and developed methods to extend the network topology lifetime. Last, we have characterized the spread of correlated user failures and suggested strategies to prevent failures from wide spreading in large wireless networks. The work in this disseration advances our understanding and enhances our utilization of large-scale multi-hop wireless networks.