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68
AdHoc Networks Beyond Unit Disk Graphs
, 2003
"... In this paper we study a model for adhoc networks close enough to reality as to represent existing networks, being at the same time concise enough to promote strong theoretical results. The Quasi Unit Disk Graph model contains all edges shorter than a parameter d between 0 and 1 and no edges longer ..."
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Cited by 143 (11 self)
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In this paper we study a model for adhoc networks close enough to reality as to represent existing networks, being at the same time concise enough to promote strong theoretical results. The Quasi Unit Disk Graph model contains all edges shorter than a parameter d between 0 and 1 and no edges longer than 1. We show that  in comparison to the cost known on Unit Disk Graphs  the complexity results in this model contain the additional factor 1/d&sup2;. We prove that in Quasi Unit Disk Graphs flooding is an asymptotically messageoptimal routing technique, provide a geometric routing algorithm being more efficient above all in dense networks, and show that classic geometric routing is possible with the same performance guarantees as for Unit Disk Graphs if d 1/ # 2.
Randomized 3D Geographic Routing
"... Abstract—We reconsider the problem of geographic routing in wireless ad hoc networks. We are interested in local, memoryless routing algorithms, i.e. each network node bases its routing decision solely on its local view of the network, nodes do not store any message state, and the message itself can ..."
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Cited by 47 (0 self)
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Abstract—We reconsider the problem of geographic routing in wireless ad hoc networks. We are interested in local, memoryless routing algorithms, i.e. each network node bases its routing decision solely on its local view of the network, nodes do not store any message state, and the message itself can only carry information about O(1) nodes. In geographic routing schemes, each network node is assumed to know the coordinates of itself and all adjacent nodes, and each message carries the coordinates of its target. Whereas many of the aspects of geographic routing have already been solved for 2D networks, little is known about higherdimensional networks. It has been shown only recently that there is in fact no local memoryless routing algorithm for 3D networks that delivers messages deterministically. In this paper, we show that a cubic routing stretch constitutes a lower bound for any local memoryless routing algorithm, and propose and analyze several randomized geographic routing algorithms which work well for 3D network topologies. For unit ball graphs, we present a technique to locally capture the surface of holes in the network, which leads to 3D routing algorithms similar to the greedyfacegreedy approach for 2D networks. I.
Distributed transactional memory for metricspace networks
 In Proc. International Symposium on Distributed Computing (DISC 2005
, 2005
"... Abstract. Transactional Memory is a concurrent programming API in which concurrent threads synchronize via transactions (instead of locks). Although this model has mostly been studied in the context of multiprocessors, it has attractive features for distributed systems as well. In this paper, we con ..."
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Cited by 30 (0 self)
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Abstract. Transactional Memory is a concurrent programming API in which concurrent threads synchronize via transactions (instead of locks). Although this model has mostly been studied in the context of multiprocessors, it has attractive features for distributed systems as well. In this paper, we consider the problem of implementing transactional memory in a network of nodes where communication costs form a metric. The heart of our design is a new cachecoherence protocol, called the Ballistic protocol, for tracking and moving uptodate copies of cached objects. For constantdoubling metrics, a broad class encompassing both Euclidean spaces and growthrestricted networks, this protocol has stretch logarithmic in the diameter of the network. 1
Greedy Routing with Bounded Stretch
"... Abstract—Greedy routing is a novel routing paradigm where messages are always forwarded to the neighbor that is closest to the destination. Our main result is a polynomialtime algorithm that embeds combinatorial unit disk graphs (CUDGs – a CUDG is a UDG without any geometric information) into O(log ..."
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Cited by 29 (0 self)
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Abstract—Greedy routing is a novel routing paradigm where messages are always forwarded to the neighbor that is closest to the destination. Our main result is a polynomialtime algorithm that embeds combinatorial unit disk graphs (CUDGs – a CUDG is a UDG without any geometric information) into O(log 2 n)dimensional space, permitting greedy routing with constant stretch. To the best of our knowledge, this is the first greedy embedding with stretch guarantees for this class of networks. Our main technical contribution involves extracting, in polynomial time, a constant number of isometric and balanced tree separators from a given CUDG. We do this by extending the celebrated LiptonTarjan separator theorem for planar graphs to CUDGs. Our techniques extend to other classes of graphs; for example, for general graphs, we obtain an O(log n)stretch greedy embedding into O(log 2 n)dimensional space. The greedy embeddings constructed by our algorithm can also be viewed as a constantstretch compact routing scheme in which each node is assigned an O(log 3 n)bit label. To the best of our knowledge, this result yields the best known stretchspace tradeoff for compact routing on CUDGs. Extensive simulations on random wireless networks indicate that the average routing overhead is about 10%; only few routes have a stretch above 1.5. I.
An algorithmic approach to geographic routing in ad hoc and sensor networks
 IEEE/ACM Trans. Netw
"... Abstract—The one type of routing in ad hoc and sensor networks that currently appears to be most amenable to algorithmic analysis is geographic routing. This paper contains an introduction to the problem field of geographic routing, presents a specific routing algorithm based on a synthesis of the g ..."
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Cited by 25 (0 self)
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Abstract—The one type of routing in ad hoc and sensor networks that currently appears to be most amenable to algorithmic analysis is geographic routing. This paper contains an introduction to the problem field of geographic routing, presents a specific routing algorithm based on a synthesis of the greedy forwarding and face routing approaches, and provides an algorithmic analysis of the presented algorithm from both a worstcase and an averagecase perspective. Index Terms—Algorithmic analysis, routing, stretch, wireless networks.
Almost optimal asynchronous rendezvous in infinite multidimensional grids
 IN: PROC. OF THE 24TH INT. SYMP. ON DISTRIBUTED COMPUTING (DISC). VOLUME 6343 OF LECTURE NOTES IN COMPUTER SCIENCE
, 2010
"... Two anonymous mobile agents (robots) moving in an asynchronous manner have to meet in an infinite grid of dimension δ> 0, starting from two arbitrary positions at distance at most d. Since the problem is clearly infeasible in such general setting, we assume that the grid is embedded in a δdimen ..."
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Cited by 17 (1 self)
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Two anonymous mobile agents (robots) moving in an asynchronous manner have to meet in an infinite grid of dimension δ> 0, starting from two arbitrary positions at distance at most d. Since the problem is clearly infeasible in such general setting, we assume that the grid is embedded in a δdimensional Euclidean space and that each agent knows the Cartesian coordinates of its own initial position (but not the one of the other agent). We design an algorithm permitting the agents to meet after traversing a trajectory of length O(d δ polylog d). This bound for the case of 2dgrids subsumes the main result of [12]. The algorithm is almost optimal, since the Ω(d δ) lower bound is straightforward. Further, we apply our rendezvous method to the following network design problem. The ports of the δdimensional grid have to be set such that two anonymous agents starting at distance at most d from each other will always meet, moving in an asynchronous manner, after traversing a O(d δ polylog d) length trajectory. We can also apply our method to a version of the geometric rendezvous problem. Two anonymous agents move asynchronously in the δdimensional Euclidean space. The agents have the radii of visibility of r1 and r2, respectively. Each agent knows only its own initial position and its own radius of visibility. The agents meet when one agent is visible to the other one. We propose an algorithm designing the trajectory of each agent, so that they always meet after traveling a total distance of O( ( d)), where r = min(r1, r2) and for r ≥ 1. r)δpolylog ( d r 1
Location Services in Wireless Ad Hoc and Hybrid Networks: A Survey
 134  Computer Science Department  Ph.D. Thesis PHD200905  2009
, 2006
"... Location services are used in mobile ad hoc and hybrid networks either to locate the geographic position of a given node in the network or for locating a data item (content). One of the main usages of position location services is in location based routing algorithms. In particular, geographic rout ..."
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Cited by 15 (3 self)
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Location services are used in mobile ad hoc and hybrid networks either to locate the geographic position of a given node in the network or for locating a data item (content). One of the main usages of position location services is in location based routing algorithms. In particular, geographic routing protocols can route messages more efficiently to their destinations based on the destination node’s geographical position, which is provided by a location service. A content location service provides to the requesting node either the requested data itself or the identifier of the node that stores this data. Sometimes the position of the node that stores the data is also provided. Such data location services are useful for implementing contentsharing applications, cooperative caching, and publish subscribe systems. In this paper we present a taxonomy of location services and survey known techniques for constructing such a service in wireless ad hoc and hybrid networks. 1
SelfStabilizing Mobile Node Location Management and Message Routing
, 2005
"... We present simple algorithms for achieving selfstabilizing location management and routing in mobile adhoc networks. While mobile clients may be susceptible to corruption and stopping failures, mobile networks are often deployed with a reliable GPS oracle, supplying frequent updates of accurate re ..."
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Cited by 15 (7 self)
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We present simple algorithms for achieving selfstabilizing location management and routing in mobile adhoc networks. While mobile clients may be susceptible to corruption and stopping failures, mobile networks are often deployed with a reliable GPS oracle, supplying frequent updates of accurate real time and location information to mobile nodes. Information from a GPS oracle provides an external, shared source of consistency for mobile nodes, allowing them to label and timestamp messages, and hence aiding in identification of, and eventual recovery from, corruption and failures. Our algorithms use a GPS oracle. Our algorithms also take advantage of the Virtual Stationary Automata programming abstraction, consisting of mobile clients, virtual timed machines called virtual stationary automata (VSAs), and a local broadcast service connecting VSAs and mobile clients. VSAs are distributed at known locations over the plane, and emulated in a selfstabilizing manner by the mobile nodes in the system. They serve as faulttolerant building blocks that can interact with mobile clients and each other, and can simplify implementations of services in mobile networks. We implement three selfstabilizing, faulttolerant services, each built on the prior services: (1) VSAtoVSA geographic routing, (2) mobile client location management, and (3) mobile client endtoend
The Virtual Node Layer: A Programming Abstraction for Wireless Sensor Networks ∗
"... The Virtual Node Layer (VNLayer) programming abstraction provides programmable, predictable automata—virtual nodes—emulated by the lowlevel network nodes. This simplifies the design and rigorous analysis of applications for the wireless sensor network setting, as the layer can mask much of the unce ..."
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Cited by 13 (7 self)
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The Virtual Node Layer (VNLayer) programming abstraction provides programmable, predictable automata—virtual nodes—emulated by the lowlevel network nodes. This simplifies the design and rigorous analysis of applications for the wireless sensor network setting, as the layer can mask much of the uncertainty of the underlying components. In this paper, we define a general VNLayer architecture, and then use this framework to design a practical VNLayer implementation, optimized for realworld use. We then discuss our experience deploying this implementation on a testbed of handheld computers, and in a custombuilt packetlevel simulator, and present a sample application—a virtual traffic light—to highlight the power and utility of our abstraction. We conclude with a survey of additional applications that are wellsuited to this setting. Categories and Subject Descriptors