We explore the problem of neighbor discovery in a mobile ad hoc network environment. We describe a protocol for learning about neighboring nodes in such an environment. The protocol is used for establishing and tearing down communication links with neighboring nodes as they move from one region of the network to another. The protocol is implemented on top of the abstract MAC layer service presented in [4], which provides reliable message delivery within the local neighborhood and also provides the sender with an acknowledgment when all neighboring nodes have received a message. There is an upper bound, guaranteed by the abstract MAC layer service, on the worst case delay that a message can experience before it is received or acknowledged. We determine the time complexity of the neighbor discovery protocol in terms of the bounded delays provided by the underlying abstract MAC layer.

We define a reliable neighbor discovery layer for mobile adhoc networks and present two algorithms that implement this layer as a service with varying progress guarantees. Our algorithms are implemented atop an abstract MAC layer [13], which deals with the lower level details of collision detection and contention. Specifically, we first describe a basic region-based neighbor discovery protocol with weak progress guarantees. Informally speaking, this protocol does not guarantee communication links when nodes move quickly across region boundaries. To overcome this limitation, we describe a technique that uses a basic neighbor discovery protocol as a black box and boosts its progress guarantees. The key idea behind this technique is to use multiple partitions overlayed in a specific way, and associate with each partition an instance of the basic neighbor discovery protocol. We show the output of these instances can be composed in a way that provides stronger progress guarantees. In the last section of the paper we discuss different user layer algorithms which would benefit from the reliable neighbor discovery layer described in this paper.

11-18 1981). Moreover, a generic representation of time is used, which can be implemented using totally-ordered values that preserve the causality of events, such as logical clocks and perfect clocks. A correctness proof for the algorithm is provided, and it is ensured that in certain well-behaved situations, a new leader is not elected unnecessarily, that is, the algorithm satisfies a stability condition.

We define a reliable neighbor discovery layer for mobile adhoc networks and present two algorithms that implement this layer as a service with varying progress guarantees. Our algorithms are implemented atop an abstract MAC layer [13], which deals with the lower level details of collision detection and contention. Specifically, we first describe a basic region-based neighbor discovery protocol with weak progress guarantees. Informally speaking, this protocol does not guarantee communication links when nodes move quickly across region boundaries. To overcome this limitation, we describe a technique that uses a basic neighbor discovery protocol as a black box and boosts its progress guarantees. The key idea behind this technique is to use multiple partitions overlayed in a specific way, and associate with each partition an instance of the basic neighbor discovery protocol. We show the output of these instances can be composed in a way that provides stronger progress guarantees. In the last section of the paper we discuss different user layer algorithms which would benefit from the reliable neighbor discovery layer described in this paper.

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