Wireless networks allow a more flexible model of communication than traditional networks since the user is not limited to a fixed physical location. Unlike cellular wireless networks, an ad hoc wireless network does not have any fixed communication infrastructure. For an active connection, the end host as well as the intermediate nodes can be mobile. Therefore routes are subject to frequent disconnections. In such an environment, it is important to minimize disruptions caused by the changing topology for critical application such as voice and video. This presents a difficult challenge for routing protocols, since rapid reconstruction of routes is crucial in the presence of topology changes. By exploiting non-random behaviors for the mobility patterns that mobile users exhibit, we can predict the future state of network topology and perform route reconstruction proactively in a timely manner. Moreover, by using the predicted information on the network topology, we can eliminate transmis...

Abstract – Wireless networks allow a more flexible communication model than traditional networks since the user is not limited to a fixed physical location. Unlike cellular wireless networks, ad hoc wireless networks do not have any fixed communication infrastructure. In ad hoc networks, routes are mostly multihop and network hosts communicate via packet radios. Each host moves in an arbitrary manner and thus routes are subject to frequent disconnections. In typical mobile networks, nodes exhibit some degree of regularity in the mobility pattern. By exploiting a mobile user’s non-random traveling pattern, we can predict the future state of network topology and thus provide a transparent network access during the period of topology changes. In this paper we present various enhancements to unicast and multicast routing protocols using mobility prediction. The proposed scheme utilizes GPS location information. By simulation, we evaluate the effectiveness of mobility prediction. I.

Ad hoc networks are gaining increasing popularity in recent years because of their ease of deployment. No wired base station or infrastructure is supported, and each host communicasts one another via packet radios. In ad hoc networks, routing protocols are challenged with establishing and maintaining multihop routes in the face of mobility, bandwidth limitation and power constraints. In this dissertation, we study the routing strategies for ad hoc networks. On-demand routing protocols and table-driven algorithms are analyzed and compared against each other. Our study shows that on-demand protocols are better suited for mobile networks because they generate less control overhead and manage the mobility in a more efficient manner. Simulation experiments also indicate that providing multiple routes is beneficial in increasing the robustness against mobility.

Abstract- Geographic routing in mobile ad hoc networks has proved to provide drastic performance improvement over strictly address-centric routing schemes. While geographic routing has been shown to be correct and efficient when location information is accurate, its performance in the face of location errors is not well understood. In this paper, we study the effect of inaccurate location information caused by node mobility under a rich set of scenarios and mobility models. We identify two main problems, named LLNK and LOOP, that are caused by mobility-induced location errors. Based on analysis via ns-2 simulations, we propose two mobility prediction schemes--- neighbor location prediction (NLP) and destination location prediction (DLP) to mitigate these problems. Simulation results show noticeable improvement under all mobility models used in our study. Our schemes achieve up to 27 % improvement in packet delivery and 37 % reduction in network resource wastage on average without incurring any additional communication or intense computation. 1.

Due to limited functionalities and potentially large number of sensors, existing routing strategies proposed for mobile ad hoc networks are not directly applicable to wireless sensor networks. In this paper, we present a meshed multipath routing (M-MPR) protocol with selective forwarding (SF) of packets and end-to-end forward error correction (FEC) coding. We also describe a meshed multipath searching scheme suitable for sensor networks, which has a reduced signaling overhead and nodal database. Our performance evaluations show that (1) M-MPR achieves a much improved throughput over conventional disjoint multipath routing with comparable power consumption and receiver complexity; (2) to successfully route a message using FEC coding, selective forwarding (SF) consumes much less network resources, such as channel bandwidth and battery power, than packet replication (or limited flooding).

Existing on-demand ad hoc network routing protocols continue using a route until a link breaks. During the route reconstruction, packets can be dropped, which will cause significant throughput degradation. In this thesis, we add a link breakage prediction algorithm to one on-demand routing protocol: the Dynamic Source Routing (DSR) protocol. The mobile node that implements the prediction algorithm uses signal power strength from the received packets to predict the link breakage time, and sends a warning to the source node of the packet if the link is soon-to-be-broken. The source node can perform a pro-active route rebuild to avoid disconnection. Experiments demonstrate that adding link breakage prediction to DSR, even considering the increased number of control messages (at most 33.5%), can significantly reduce the total number of dropped data packets (at least 20%) due to link breakage by reducing the number of broken links. We believe that TCP can potentially benefit well from the pro-active route maintenance to increase throughput, which is affected by broken links. We also propose a modification plan for AODV and make recommendations about further improvement on DSR based on the link breakage prediction. ACKNOWLEDGEMENT I would like to thank my supervisor, Professor Thomas Kunz, for his guidance and direction for this thesis, for the many interesting discussions we had. I greatly benefit from his detailed comments and insights that help me clarify my ideas and present the materials in a suitable way. I would like to thank the teachers at the School of Computer Science and Department of Systems and Computer Engineering, Carleton University for all the things I learned here. I would also like to thank Mr. John Knox for his assistance and support of computer s...

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Abstract: In distributed and mobile environments, the connections among the hosts on which a software system is running are often unstable. As a result of connectivity losses, the overall availability of the system decreases. The distribution of software components onto hardware nodes (i.e., deployment architecture) may be ill-suited for the given target hardware environment and may need to be altered to improve the software system’s availability. The critical difficulty in achieving this task lies in the fact that determining a software system’s deployment that will maximize its availability is an exponentially complex problem. In this paper, we present an automated, flexible, software architecturebased solution for disconnected operation that increases the availability of the system during disconnection. We provide a fast approximative solution for the

This paper addresses the problem of using unrealistic mobility scenarios for simulation of ad-hoc routing protocols. We present CAD-HOC, a cousin tool to Network Simulator (ns), which allows ad-hoc networking experimentation to be performed under visually realistic scenarios such as an airport or a bus terminal, buildings, highways and other facilities. CADHOC focuses on capturing the visual scenario and transforming it into mobility and connection benchmarks, which are subsequently fed to ns to drive simulation experiments.

Most existing on-demand mobile ad hoc network routing protocols continue using a route until a link breaks. During the route reconstruction, packets can be dropped, which will cause significant throughput degradation. In this paper, we add a link breakage prediction algorithm to the Dynamic Source Routing (DSR) protocol. The mobile node uses signal power strength from the received packets to predict the link breakage time, and sends a warning to the source node of the packet if the link is soon-to-be-broken. The source node can perform a pro-active route rebuild to avoid disconnection. Experiments demonstrate that adding link breakage prediction to DSR can significantly reduce the total number of dropped data packets (by at least 20%). The tradeoff is an increase in the number of control messages by at most 33.5%. We also found that the proactive route maintenance does not cause significant increase in average packet latency and average route length. Enhanced route cache maintenance based on the link status can further reduce the number of dropped packets. 1.