Trajectory based forwarding (TBF) is a novel method to forward packets in a dense ad hoc network that makes it possible to route a packet along a predefined curve. It is a generalization of source based routing and Cartesian forwarding in that the trajectory is set by the source, but the forwarding decision is based on the relationship to the trajectory rather than the final destination. The fundamental aspect of TBF is that it decouples path naming from the actual path, thereby providing a common framework for applications such as: flooding, unicast, multicast and multipath routing, and discovery in ad hoc networks. TBF requires that nodes know their position relative to a coordinate system. While a global coordinate system a#orded by a system such as GPS would be ideal, in this paper we propose Local Positioning System (LPS), a method that only positions the nodes along the trajectory, by making use of other node capabilities, such as angle of arrival or range estimations, compasses and accelerometers. We explore several forwarding strategies that are appropriate for these node capabilities.

In recent years, several position-based routing protocols have been developed for mobile ad hoc networks. Many of these protocols assume a location service is available that provides location information on the nodes in the network. In this chapter, we survey all the proposed location information services that exist in the literature to date. We classify these location information services into three categories: proactive location database systems, proactive location dissemination systems, and reactive location systems.

Coping with mobility and dynamism is one of the biggest challenges in ad hoc networks. An essential requirement for such networks is a service that can establish communication sessions between mobile nodes whose location is unknown. A location service for ad hoc networks is a distributed algorithm that allows any source node s to know the location of any destination node t, simply by knowing t's network identifier.

We present a new approach, the GeoQuorums approach, for implementing atomic read/write shared memory in mobile ad hoc networks. Our approach is based on associating abstract atomic objects with certain geographic locations. We assume the existence of focal points, geographic areas that are normally "populated" by mobile nodes.

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A Persistent Node is a redundant distributed mechanism for storing a key/value pair reliably in a geographically local network. In this paper, I develop a method of establishing Persistent Nodes in an amorphous matrix. I address issues of construction, usage, atomicity guarantees and reliability in the face of stopping failures. Applications include routing, congestion control, and data storage in gigascale networks.

Mobile ad-hoc networks (MANETs) are failure-prone environments; it is common for mobile wireless nodes to intermittently disconnect from the network, e.g., due to signal blockage. This paper focuses on withstanding such failures in large MANETs: we present Octopus, a fault-tolerant and efficient position-based routing protocol. Fault-tolerance is achieved by employing redundancy, i.e., storing the location of each node at many other nodes, and by keeping frequently refreshed soft state. At the same time, Octopus achieves a low location update overhead by employing a novel aggregation technique, whereby a single packet updates the location of many nodes at many other nodes. Octopus is highly scalable: for a fixed node density, the number of location update packets sent does not grow with the network size. And when the density increases, the overhead drops. Thorough empirical evaluation using the ns2 simulator with up to 675 mobile nodes shows that Octopus achieves excellent fault-tolerance at a modest overhead: when all nodes intermittently disconnect and reconnect, Octopus achieves the same high reliability as when all nodes are constantly up. 1

Abstract — In mobile sensor networks, self-deployment and relocation are two different research issues, both of which involve autonomous sensor movement. They share in most cases a common goal, that is, to improve overall network sensing coverage. Under this circumstance, some self-deployment algorithms may be applied to solving relocation problem without modification. However, considering efficiency, they will not be a good option in the scenario with high sensor failure rate. Existing sensor relocation protocols are not quite practical because they rely on strong assumptions and/or have weakness in maintaining network topology. In this paper, we propose a distributed zone-based sensor relocation protocol, ZONER, for mobile sensor networks on the basis of a restricted flooding technique, i.e., ZFlooding. Requiring zero-knowledge about sensor field, the ZONER is able to effectively discover previously-deployed redundant sensors without being concerned with obstacles or network ununiformity, and it relocates them in a shifting way to replace failed nonredundant ones without changing network topology. At the end of the paper, we prove the correctness of the ZONER and point out our future work. I.

Sensor relocation protocols can be employed as fault tolerance approach to offset the coverage loss caused by node failures. We introduce a novel localized structure, information mesh, for publishing and retrieving node location information. Based on the structure, we propose a Mesh-based Sensor Relocation Protocol (MSRP) for mobile sensor networks. MSRP maintains a sensor network’s sensing coverage by replacing failed sensors with nearby redundant ones using near optimal time delay and balanced energy consumption. Simulation indicates that it guarantees closest node replacement with high probability (> 96%) and with considerably low message overhead. We show that MSRP is superior to the existing sensor relocation schemes for its localized message transmissions and optimal (constant) per node storage load.

Quorum systems are a mechanism for obtaining fault-tolerance and efficient distributed systems. We consider geographic quorum systems; a geographic quorum system is a partition of a set X of sites in the plane (representing servers) into quorums (i.e. clusters) of size k. The distance between a point p and a cluster C is the Euclidean distance between p and the site in C that is the farthest from p. We present a near linear time constant-factor approximation algorithm for partitioning X into clusters, such that, the maximal distance between a point in the underlying region and its closest cluster is minimized. Next, we describe a data-structure for answering (approximately) nearest-neighbor queries on such a clustering. Finally, we study the problem of partitioning into clusters with an additional loadbalancing requirement. 1