Broadcasting is a fundamental primitive in local area networks (LANs).Operations of many data link protocols, for example, ARP (Address Resolution Protocol) and IGMP (Internet Group Management Protocol), must rely on this LAN primitive. To develop the broadcasting service in mobile ad hoc wireless LANs (WLANs) is a challenge. This is because a mobile ad hoc WLAN is a multi-hop wireless network in which messages may travel along several links from the source to the destination via a certain path. Additionally, there is no fixed network topology because of host moving. Furthermore, the broadcast nature of a radio channel makes a packet be transmitted by a node to be able to reach all neighbors. Therefore, the total number of transmissions (forward nodes) is generally used as the cost criterion for broadcasting. The problem of finding the minimum number of forward nodes in a static radio network is NP-complete. Almost all previous works, therefore, for broadcasting in the WLAN are focusing on finding approximation approaches in a, rather than, environment. In this paper, we propose a novel distributed protocol in WLANs to significantly reduce or eliminate the communication overhead in addition to maintaining positions of neighboring nodes. The important features of our proposed protocol are the adaptability to dynamic network topology change and the utilization of the existing routing protocol. The reduction in communication overhead for broadcasting operation is measured experimentally. From the simulation results, our protocol not only has the similar performance as the approximation approaches in the static network, but also outperforms existing ones in the adaptability to host moving.

We develop two algorithms for important problems in mobile ad hoc networks (MANETs). A MANET is a collection of mobile processors (“nodes”) which communicate via message passing over wireless links. Each node can communicate directly with other nodes within a specified transmission radius; other communication is accomplished via message relay. Communication links may go up and down in a MANET (as nodes move toward or away from each other); thus, the MANET can consist of multiple connected components, and connected components can split and merge over time. We first present a deterministic leader election algorithm for asynchronous MANETs along with a correctness proof for it. Our work involves substantial modifications of an existing algorithm and its proof, and we adapt the existing algorithm to the asynchronous environment. Our algorithm’s running time and message complexity compare favorably with existing algorithms for leader election in MANETs. Second, many algorithms for MANETs require or can benefit from knowledge about the size of the network in terms of the number of processors. As such, we present an algorithm to approximately determine the size of a MANET. While the algorithm’s approximations of network size are only rough ones, the algorithm has the important qualities of requiring little communication overhead and being tolerant of link failures.

This thesis presents an intelligent early packet discard (I-EPD) for real-time video streaming over a multi-hop ad hoc network. In a multi-hop ad hoc network, the quality of transferring real-time video streams could be seriously degraded, since every intermediate node (IN) functionally like forwarding device does not possess large buffer and sufficient bandwidth. Even worse, a selected forwarding node could leave or power off unexpectedly which breaks the route to destination. Thus, a video packet temporarily buffered in intermediate nodes may exceed its time constraint when either a congested or failed link occurs; a stale video packet is useless even if it can reach destination after network traffic becomes smooth or failed route is reconfigured. In the proposed I-EPD, an IN can intelligently determine whether a buffered video packet should be discarded based on an estimated time constraint which is calculated from the RTP timestamps and the round trip time (RTT) measured by RTCP. For the purpose of validation, we implement the I-EPD scheme on a Linux-based embedded system. We compare the quality of video streams under different bit rates and different route repair time. In addition, we use PSNR to validate the quality of pictures from the aspect of application layer. The experimental results demonstrate that with I-EPD buffer utilization on IN can be more effectively used and unnecessary bandwidth wastage can be avoided.

This paper studies the integrated mobile ad-hoc networks (MANETs) and Internet network which the Mobile IP and AODV routing protocols are integrated to offer MANET nodes to set up multi-hop routes to the Internet. Gateways act as bridges for forwarding data packets between integrated MANETs and the Internet. Mobile nodes in MANETs must discover available gateways to gain access to the Internet. This study presents an adaptive gateway discovery scheme that balances efficiency and overhead by limiting the flooding scope of gateway advertisement messages. The proposed scheme dynamically adjusts the ADV_TTL according to the average delay time of network. The simulation results showed that the proposed scheme obtains the shortest average delay time while keeping the network a relatively lower overhead.

Abstract Vehicular Ad Hoc Networks (VANET) can provide strong safety for vehicles by taking the advantages of the information which are interchanged among themselves and some infrastructures. Due to this significant application of VANET, message authentication and privacy in VANET is quite critical. Pseudonym PKI technology is a practical solution to ensure the above two properties. However, the performance of the previous works cannot satisfy the requirement for the applications in VANET, such as efficiency and management cost. Most of all pseudonym PKI technologies are comprehensive schemes, like group key and ID-based public key cryptosystem. This also increases the implementation complexity of VANET security. Therefore, we will propose an efficient pseudonym PKI mechanism based on bilinear mapping to improve the performance of the message authentication protocol, certificate tracing and certificate revocation, implementation cost, and management cost.

<p>Technology has reached a point where it has become feasible to develop unmanned aerial vehicles (UAVs), that is aircraft without a human pilot on board. Given that future UAVs can be autonomous and cheap, applications of swarming UAVs are possible. In this thesis we have studied a reconnaissance application using swarming UAVs and how these UAVs can communicate the reconnaissance data. To guide the UAVs in their reconnaissance mission we have proposed a pheromone based mobility model that in a distributed manner guides the UAVs to areas not recently visited. Each UAV has a local pheromone map that it updates based on its reconnaissance scans. The information in the local map is regularly shared with a UAV’s neighbors. Evaluations have shown that the pheromone logic is very good at guiding the UAVs in their cooperative reconnaissance mission in a distributed manner.</p><p>Analyzing the connectivity of the UAVs we found that they were heavily partitioned which meant that contemporaneous communication paths generally were not possible to establish. This means that traditional mobile ad hoc network (MANET) routing protocols like AODV, DSR and GPSR will generally fail. By using node mobility and the store-carry-forward principle of delay-tolerant routing the transfer of messages between nodes is still possible. In this thesis we propose location aware routing for delay-tolerant networks (LAROD). LAROD is a beacon-less geographical routing protocol for intermittently connected mobile ad hoc networks. Using static destinations we have shown by a comparative study that LAROD has almost as good delivery rate as an epidemic routing scheme, but at a substantially lower overhead.</p> / Report code: LiU-Tek-Lic-2008:14

Thesis (Ph.D. (Computer Science)) - Rhodes University, 2008.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 41-44).

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Charles G. Boncelet, Dept. of Computer & Information Sciences. Includes bibliographical references.

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