LCS Publication Details
Publication Title: GeoQuorums: Implementing Atomic Memory in Mobile Ad Hoc Networks
Publication Author: Dolev, Shlomi
Additional Authors: Seth Gilbert, Nancy A. Lynch, Alex A. Shvartsman, Jennifer L. Welch
LCS Document Number: MIT-LCS-TR-900a
Publication Date: 2-25-2004
LCS Group: Theory of Computation
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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. For example, a focal point may be a road junction, a scenic observation point, or a water resource in the desert. Mobile nodes that happen to populate a focal point participate in implementing a shared atomic object, using a replicated state machine approach. These objects, which we call focal point objects, are then used to implement atomic read/write operations on a virtual shared object, using our new GeoQuorums algorithm. The GeoQuorums algorithm uses a quorum-based strategy in which each each quorum consists of a set of focal point objects. The quorums are used to maintain the consistency of the shared memory and to tolerate limited failures of the focal point objects, caused by depopulation of the corresponding geographic areas. We present a mechanism for changing the set of quorums on the fly, thus improving efficiency. Overall, the new GeoQuorums algorithm efficiently implements read and write operations in a highly dynamic, mobile network.
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