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141
Geographic routing made practical
, 2005
"... Geographic routing has been widely hailed as the most promising approach to generally scalable wireless routing. However, the correctness of all currently proposed geographic routing algorithms relies on idealized assumptions about radios and their resulting connectivity graphs. We use testbed measu ..."
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Cited by 174 (4 self)
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Geographic routing has been widely hailed as the most promising approach to generally scalable wireless routing. However, the correctness of all currently proposed geographic routing algorithms relies on idealized assumptions about radios and their resulting connectivity graphs. We use testbed measurements to show that these idealized assumptions are grossly violated by real radios, and that these violations cause persistent failures in geographic routing, even on static topologies. Having identified this problem, we then fix it by proposing the CrossLink Detection Protocol (CLDP), which enables provably correct geographic routing on arbitrary connectivity graphs. We confirm in simulation and further testbed measurements that CLDP is not only correct but practical: it incurs low overhead, exhibits low path stretch, always succeeds in real, static wireless networks, and converges quickly after topology changes. 1
On the Complexity of Scheduling in Wireless Networks
 MOBICOM '06
, 2006
"... We consider the problem of throughputoptimal scheduling in wireless networks subject to interference constraints. We model the interference using a family of Khop interference models. We define a Khop interference model as one for which no two links within K hops can successfully transmit at the ..."
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Cited by 129 (3 self)
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We consider the problem of throughputoptimal scheduling in wireless networks subject to interference constraints. We model the interference using a family of Khop interference models. We define a Khop interference model as one for which no two links within K hops can successfully transmit at the same time (Note that IEEE 802.11 DCF corresponds to a 2hop interference model.). For a given K, a throughputoptimal scheduler needs to solve a maximum weighted matching problem subject to the Khop interference constraints. For K = 1, the resulting problem is the classical Maximum Weighted Matching problem, that can be solved in polynomial time. However, we show that for K> 1, the resulting problems are NPHard and cannot be approximated within a factor that grows polynomially with the number of nodes. Interestingly, we show that for specific kinds of graphs, that can be used to model the underlying connectivity graph of a wide range of wireless networks, the resulting problems admit polynomial time approximation schemes. We also show that a simple greedy matching algorithm provides a constant factor approximation to the scheduling problem for all K in this case. We then show that under a setting with singlehop traffic and no rate control, the maximal scheduling policy considered in recent related works can achieve a constant fraction of the capacity region for networks whose connectivity graph can be represented using one of the above classes of graphs. These results are encouraging as they suggest that one can develop distributed algorithms to achieve near optimal throughput in case of a wide range of wireless networks.
On delivery guarantees of face and combined greedyface routing in ad hoc and sensor networks
 in Ad Hoc and Sensor Networks”. In Proc. of ACM MobiCom
, 2006
"... It was recently reported that all known face and combined greedyface routing variants cannot guarantee message delivery in arbitrary undirected planar graphs. The purpose of this article is to clarify that this is not the truth in general. We show that specifically in relative neighborhood and Gabr ..."
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Cited by 101 (17 self)
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It was recently reported that all known face and combined greedyface routing variants cannot guarantee message delivery in arbitrary undirected planar graphs. The purpose of this article is to clarify that this is not the truth in general. We show that specifically in relative neighborhood and Gabriel graphs recovery from a greedy routing failure is always possible without changing between any adjacent faces. Guaranteed delivery then follows from guaranteed recovery while traversing the very first face. In arbitrary graphs, however, a proper face selection mechanism is of importance since recovery from a greedy routing failure may require visiting a sequence of faces before greedy routing can be restarted again. A prominent approach is to visit a sequence of faces which are intersected by the line connecting the source and destination node. Whenever encountering an edge which is intersecting with this line, the critical part is to decide if face traversal has to change to the next adjacent one or not. Failures may occur from incorporating face routing procedures that force to change the traversed face at each intersection. Recently observed routing failures which were produced by the GPSR protocol in arbitrary planar graphs result from incorporating such a face routing variant. They cannot be constructed by the well known GFG algorithm which does not force changing the face anytime. Beside methods which visit the faces intersected by the source destination line, we discuss face routing variants which simply restart face routing whenever the next face has to be explored. We give the first complete and formal proofs that several proposed face routing, and combined greedyface routing schemes do guarantee delivery in specific graph classes or even any arbitrary planar graphs. We also discuss the reasons why other methods may fail to deliver a message or even end up in a loop.
XTC: A Practical Topology Control Algorithm for AdHoc Networks
 In 4th International Workshop on Algorithms for Wireless, Mobile, Ad Hoc and Sensor Networks (WMAN
, 2003
"... The XTC adhoc network topology control algorithm introduced in this paper shows three main advantages over previously proposed algorithms. First, it is extremely simple and strictly local. Second, it does not assume the network graph to be a Unit Disk Graph; XTC proves correct also on general weigh ..."
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Cited by 92 (9 self)
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The XTC adhoc network topology control algorithm introduced in this paper shows three main advantages over previously proposed algorithms. First, it is extremely simple and strictly local. Second, it does not assume the network graph to be a Unit Disk Graph; XTC proves correct also on general weighted network graphs. Third, the algorithm does not require availability of node position information. Instead, XTC operates with a general notion of order over the neighbors' link qualities. In the special case of the network graph being a Unit Disk Graph, the resulting topology proves to have bounded degree, to be a planar graph, andon averagecase graphsto be a good spanner.
Target tracking with binary proximity sensors: fundamental limits, minimal descriptions, and algorithms
 in SenSys ’06: Proc. 4th Internat. Conf. on Embedded Networked Sensor Systems, 2006
, 2006
"... We explore fundamental performance limits of tracking a target in a twodimensional field of binary proximity sensors, and design algorithms that attain those limits. In particular, using geometric and probabilistic analysis of an idealized model, we prove that the achievable spatial resolution Δ in ..."
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Cited by 76 (6 self)
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We explore fundamental performance limits of tracking a target in a twodimensional field of binary proximity sensors, and design algorithms that attain those limits. In particular, using geometric and probabilistic analysis of an idealized model, we prove that the achievable spatial resolution Δ in localizing a target’s trajectory is of the order of 1 ρR, where R is the sensing radius and ρ is the sensor density per unit area. Using an Occam’s razor approach, we then design a geometric algorithm for computing an economical (in descriptive complexity) piecewise linear path that approximates the trajectory within this fundamental limit of accuracy. We employ analogies between binary sensing and sampling theory to contend that only a “lowpass ” approximation of the trajectory is attainable, and explore the implications of this observation for estimating the target’s velocity. We show through simulation the effectiveness of the geometric algorithm in tracking both the trajectory and the velocity of the target for idealized models. For nonideal sensors exhibiting sensing errors, the geometric algorithm can yield poor performance. We show that nonidealities can be handled well using a particle filter based approach, and that geometric postprocessing of the output of the Particle Filter algorithm yields an economical path description as in the idealized setting. Finally, we report on our labscale experiments using motes with acoustic sensors to validate our theoretical and simulation results.
Localized Topology Control for Heterogeneous Wireless Adhoc Networks
, 2004
"... We study topology control in heterogeneous wireless ad hoc networks, where mobile hosts may have different maximum transmission powers and two nodes are connected iff they are within the maximum transmission range of each other. We present several strategies that all wireless nodes selfmaintain sp ..."
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Cited by 67 (10 self)
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We study topology control in heterogeneous wireless ad hoc networks, where mobile hosts may have different maximum transmission powers and two nodes are connected iff they are within the maximum transmission range of each other. We present several strategies that all wireless nodes selfmaintain sparse and power efficient topologies in heterogeneous network environment with low communication cost. The first structure is sparse and can be used for broadcasting. While the second structure keeps the minimum power consumption path, and the third structure is a length and power spanner with a bounded degree. Both the second and third structures are power efficient and can be used for unicast. Here a structure is power efficient if the total power consumption of the least cost path connecting any two nodes in it is no more than a small constant factor of that in the original heterogeneous communication graph. All our methods use at most O(n) total messages, where each message has O(log n) bits.
Initializing Newly Deployed Ad Hoc and Sensor Networks
 in Proceedings of 10 th Annual International Conference on Mobile Computing and Networking (MOBICOM
, 2004
"... A newly deployed multihop radio network is unstructured and lacks a reliable and e#cient communication scheme. In this paper, we take a step towards analyzing the problems existing during the initialization phase of ad hoc and sensor networks. Particularly, we model the network as a multihop quasi ..."
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Cited by 67 (15 self)
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A newly deployed multihop radio network is unstructured and lacks a reliable and e#cient communication scheme. In this paper, we take a step towards analyzing the problems existing during the initialization phase of ad hoc and sensor networks. Particularly, we model the network as a multihop quasi unit disk graph and allow nodes to wake up asynchronously at any time. Further, nodes do not feature a reliable collision detection mechanism, and they have only limited knowledge about the network topology. We show that even for this restricted model, a good clustering can be computed e#ciently. Our algorithm e#ciently computes an asymptotically optimal clustering. Based on this algorithm, we describe a protocol for quickly establishing synchronized sleep and listen schedule between nodes within a cluster. Additionally, we provide simulation results in a variety of settings.
Unit Disk Graph Approximation
 In Workshop on Discrete Algorithms and Methods for Mobile Computing and Communications (DIALM
, 2004
"... Finding a good embedding of a unit disk graph given by its connectivity information is a problem of practical importance in a variety of fields. In wireless ad hoc and sensor networks, such an embedding can be used to obtain virtual coordinates. In this paper, we prove a nonapproximability result f ..."
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Cited by 62 (10 self)
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Finding a good embedding of a unit disk graph given by its connectivity information is a problem of practical importance in a variety of fields. In wireless ad hoc and sensor networks, such an embedding can be used to obtain virtual coordinates. In this paper, we prove a nonapproximability result for the problem of embedding a given unit disk graph. Particularly, we show that if nonneighboring nodes are not allowed to be closer to each other than distance 1, then two neighbors can be as far apart as #, where # goes to 0 as n goes to infinity, unless P = NP . We further show that finding a realization of a dquasi unit disk graph with 1/ # 2 is NP hard.
On the pitfalls of geographic face routing
 in Proc. of DIALMPOMC
, 2005
"... Geographic face routing algorithms have been widely studied in the literature [1, 8, 13]. All face routing algorithms rely on two primitives: planarization and face traversal. The former computes a planar subgraph of the underlying wireless connectivity graph, while the latter defines a consistent f ..."
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Cited by 59 (0 self)
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Geographic face routing algorithms have been widely studied in the literature [1, 8, 13]. All face routing algorithms rely on two primitives: planarization and face traversal. The former computes a planar subgraph of the underlying wireless connectivity graph, while the latter defines a consistent forwarding mechanism for routing around “voids. ” These primitives are known to be provably correct under the idealized unitdisk graph assumption, where nodes are assumed to be connected if and only if they are within a certain distance from each other. In this paper we classify the ways in which existing planarization techniques fail with realistic, nonideal radios. We also demonstrate the consequences of these pathologies on reachability between node pairs in a real wireless testbed. We then examine the various face traversal rules described in the literature, and identify those [12, 16] that are robust to violations of the unitdisk graph assumption.