Cooperation-aided solutions for data delivery in challenged wireless networks

• Main Author: Yang, Shengbo
• Other Authors: Lee Bu Sung
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Computer science and engineering::Computer systems organization::Computer-communication networks
• Online Access: http://hdl.handle.net/10356/51269
• Institution: Nanyang Technological University

To satisfy people’s increasing demand for network connectivity and Internet access, several new wireless network paradigms, such as Mobile Ad Hoc Networks (MANETs), Vehicular Ad Hoc Networks (VANETs) and Pocket Switched Networks (PSNs), are emerging in recent years. These networks not only extend the wireless network coverage and make several new applications possible, but also bring great challenges. In this dissertation, the author widely exploits the cooperation opportunities among mobile nodes in the proposed network design to improve the system performance. It shows that the cooperation, if well utilized, is able to enhance the network robustness, increase the effective data rate and reduce the energy consumption. According to the specific challenges of the different wireless networks, different solutions are provided. Firstly, the author addresses the problem of delivering data packets for highly dynamic MANETs in a reliable and timely manner. Most existing ad hoc routing protocols are susceptible to node mobility, especially for large-scale networks. Driven by this issue, the author proposes an efficient Position-based Opportunistic Routing (POR) protocol which takes advantage of the stateless property of geographic routing and the broadcast nature of wireless medium. When a data packet is sent out, some of the neighbor nodes cooperatively take turn to forward the packet if it is not relayed by the specific best forwarder within a certain period of time. By utilizing such in-theair backup, communication is maintained without being interrupted. The additional latency incurred by local route recovery is greatly reduced and the duplicate relaying caused by packet reroute is also decreased. The author then pays attention to a specific type of VANETs – drive-thru networks, which depend on roadside units (RSUs) to provide vehicular users with intermittent Internet access service. Focusing on the downlink service, MaxCD – a joint multiflow scheduling and cooperative downloading protocol is proposed with the goal of maximizing the amount of data packets that can be downloaded per drive-thru. Based on the macro-level opportunistic scheduling and node cooperation, the best wireless link(s) (with the highest data rate) between the RSU and vehicular users can always be utilized. In addition, a multi-channel collision-free relay mechanism is designed to address the reliable and fast data exchange issue when the vehicular users are outside the service area of the RSU. Finally, the author considers the energy-efficient contact discovery issue in Delay Tolerant Networks (DTNs). Contact discovery is a fundamental premise of information exchange in DTNs. However, the intermittent connectivity nature of DTNs makes energy efficient contact discovery a tough challenge. In this work, the author considers a specific type of DTNs, Pocket Switched Networks (PSNs), in which the nodes’ mobility pattern shows strong social property – several nodes periodically gather at certain hot spots and form well connected clusters. Based on such mobility pattern, cooperation among nodes is exploited in the proposed contact discovery design. The nodes that have already joined a cluster collaboratively wake up to discover new contacts. With local synchronization and complementary consideration of possible traffic congestion, both the theoretical analysis and simulation results show that the proposed cooperative duty cycling (CDC) greatly reduces the energy consumption while achieving comparable data delivery performance for such DTNs.