In modern communication systems, wireless ad hoc networking has become an irreplaceable technology where communication infrastructure is insufficient or unavailable. An ad hoc network is a collection of self-organizing nodes that are rapidly deployable and adaptable to frequent topology changes. In this dissertation, the key problems related to the network layer (i.e., forwarding, routing, and network-layer topology control) are addressed. The problem of unfair forwarding in ad hoc nodes is identified and cross-layer solutions are proposed. Because a typical ad hoc node functions both as a router and a host, severe unfairness occurs between originated and forwarded packets which eventually leads to a serious starvation problem. The results show that, to restore the fairness and enhance the capacity efficiency, non-traditional queueing schemes are required where both the network and the MAC layers should be considered together. Routing is a critical protocol, which directly affects the scalability and reliability of wireless ad hoc networks. A good routing protocol for wireless ad hoc networks should overcome the dynamic nature of the topology arising from unreliable wireless links and node mobility. In ad hoc networks, it is very important to balance the route accuracy and overhead efficiency. A number of routing protocols have been proposed for wireless ad hoc networks, but it is well known that current routing protocols scale poorly with the number of nodes, the number of traffic flows, the intensity of mobility. The main objective of this dissertation is to provide efficient routing protocols for different types of wireless ad hoc networks including wireless mesh networks (WMNs), mobile ad hoc networks (MANETs), and wireless sensor networks (WSNs). Since each category has different assumptions and constraints, different solutions should be considered. WMNs and WSNs have low mobility and centralized (one-to-any) traffic patterns while MANETs have relatively high mobility and uniform (any-to-any) traffic patterns. WSNs are highly resource-constrained while WMNs are not. A new routing protocol specially designed for WMNs is proposed. Simulation experiments show that the protocol outperforms existing generic ad hoc routing protocols. This improvement is enabled by the essential characteristics of WMNs, and as a result, the protocol does not rely on bandwidth-greedy flooding mechanism. For MANET routing, an existing de facto the standard Internet intra-AS (autonomous system) routing protocol is extended to enhance the scalability in ad hoc environments. When extended for MANETs, Open Shortest Path First (OSPF) is expected to provide the benefits of maturity, interoperability, and scalability. The scalability extension is two-fold: the notions of distance effect and multiple areas are explored as extensions. Both approaches provide significant gain in scalability by efficiently reducing flooding overhead without compromising routing or forwarding performance. Finally, a new scalable and reliable sensor network routing is proposed. Since WSNs are the most resource-constrained type of ad hoc networks, the protocol should be very simple yet reliable. The proposed WSN routing protocol is designed to provide reliability (via multi-path redundancy), scalability (with efficiently contained flooding), and flexibility (source-tunable per-packet priority), which are achieved without adding protocol complexity or resource consumption. The protocol is implemented on real sensor motes and its performance is tested through outdoor sensor field deployments. The results show that the protocol outperforms even sophisticated link estimation based sensor network routing protocols.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-08172006-150002 |
| Date | 21 August 2006 |
| Creators | Jun, Jangeun |
| Contributors | Mihail L. Sichitiu, Arne A. Nilsson, George N. Rouskas, Do Young Eun |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-08172006-150002/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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