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69
DRAND: Distributed randomized TDMA scheduling for wireless ad hoc networks
 in MobiHoc
, 2006
"... This paper presents a distributed implementation of RAND, a randomized time slot scheduling algorithm, called DRAND. DRAND runs in O(δ) time and message complexity where δ is the maximum size of a twohop neighborhood in a wireless network while message complexity remains O(δ), assuming that message ..."
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Cited by 99 (2 self)
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This paper presents a distributed implementation of RAND, a randomized time slot scheduling algorithm, called DRAND. DRAND runs in O(δ) time and message complexity where δ is the maximum size of a twohop neighborhood in a wireless network while message complexity remains O(δ), assuming that message delays can be bounded by an unknown constant. DRAND is the first fully distributed version of RAND. The algorithm is suitable for a wireless network where most nodes do not move, such as wireless mesh networks and wireless sensor networks. We implement the algorithm in TinyOS and demonstrate its performance in a real testbed of Mica2 nodes. The algorithm does not require any time synchronization and is shown to be effective in adapting to local topology changes without incurring global overhead in the scheduling. Because of these features, it can also be used even for other scheduling problems such as frequency or code scheduling (for FDMA or CDMA) or local identifier assignment for wireless networks where time synchronization is not enforced.
Selfstabilizing population protocols
 In Ninth International Conference on Principles of Distributed Systems
"... This paper studies selfstabilization in networks of anonymous, asynchronously interacting nodes where the size of the network is unknown. Constantspace protocols are given for Dijkstrastyle roundrobin token circulation, leader election in rings, 2hop coloring in degreebounded graphs, and estab ..."
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Cited by 43 (7 self)
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This paper studies selfstabilization in networks of anonymous, asynchronously interacting nodes where the size of the network is unknown. Constantspace protocols are given for Dijkstrastyle roundrobin token circulation, leader election in rings, 2hop coloring in degreebounded graphs, and establishing consistent global orientation in an undirected ring. A protocol to construct a spanning tree in regular graphs using O(log D) memory is also given, where D is the diameter of the graph. A general method for eliminating nondeterministic transitions from the selfstabilizing implementation of a large family of behaviors is used to simplify the constructions, and general conditions under which protocol composition preserves behavior are used in proving their correctness.
Deterministic distributed vertex coloring in polylogarithmic time
 In Proc. of the 29th ACM Symp. on Principles of Distributed Computing
, 2010
"... Consider an nvertex graph G = (V,E) of maximum degree ∆, and suppose that each vertex v ∈ V hosts a processor. The processors are allowed to communicate only with their neighbors in G. The communication is synchronous, i.e., it proceeds in discrete rounds. In the distributed vertex coloring problem ..."
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Cited by 28 (6 self)
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Consider an nvertex graph G = (V,E) of maximum degree ∆, and suppose that each vertex v ∈ V hosts a processor. The processors are allowed to communicate only with their neighbors in G. The communication is synchronous, i.e., it proceeds in discrete rounds. In the distributed vertex coloring problem the objective is to color G with ∆ + 1, or slightly more than ∆ + 1, colors using as few rounds of communication as possible. (The number of rounds of communication will be henceforth referred to as running time.) Efficient randomized algorithms for this problem are known for more than twenty years [1, 19]. Specifically, these algorithms produce a (∆+1)coloring within O(log n) time, with high probability. On the other hand, the best known deterministic algorithm that requires
INFUSE: A TDMA based data dissemination protocol for sensor networks
 International Journal on Distributed Sensor Networks (IJDSN
, 2004
"... Reliable dissemination of bulk data is one of the important problems in sensor networks. For example, programming or upgrading the software in sensors at runtime requires reliable dissemination of a new program across the network. In this paper, we present Infuse, a time division multiple access ( ..."
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Cited by 28 (7 self)
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Reliable dissemination of bulk data is one of the important problems in sensor networks. For example, programming or upgrading the software in sensors at runtime requires reliable dissemination of a new program across the network. In this paper, we present Infuse, a time division multiple access (TDMA) based reliable data dissemination protocol. Infuse takes two input parameters: (i) the choice of the recovery algorithm (from one of two presented in this paper) to deal with unexpected channel errors (e.g., message corruption, varying signal strength), and (ii) whether a sensor should listen only to a subset of its neighbors to reduce the amount of active radio time. Based on these parameters, we obtain four possible versions of Infuse. We compare the performance of these versions to assist a designer in selecting the appropriate version based on the network characteristics. Furthermore, we demonstrate Infuse in the context of network programming.
The abstract MAC layer
, 2009
"... Abstract. A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local broadcast communication, with timing guarantees stated in terms of a ..."
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Cited by 21 (14 self)
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Abstract. A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local broadcast communication, with timing guarantees stated in terms of a collection of abstract delay functions applied to the relevant contention. Algorithm designers can analyze their algorithms in terms of these functions, independently of specific channel behavior. Concrete implementations of the Abstract MAC Layer over basic radio network models generate concrete definitions for these delay functions, automatically adapting bounds proven for the abstract service to bounds for the specific radio network under consideration. To illustrate this approach, we use the Abstract MAC Layer to study the new problem of MultiMessage Broadcast, a generalization of standard singlemessage broadcast, in which any number of messages arrive at any processes at any times. We present and analyze two algorithms for MultiMessage Broadcast in static networks: a simple greedy algorithm and one that uses regional leaders. We then indicate how these results can be extended to mobile networks. 1
Deploying Wireless Networks with Beeps
"... We present the discrete beeping communication model, which assumes nodes have minimal knowledge about their environment and severely limited communication capabilities. Specifically, nodes have no information regarding the local or global structure of the network, do not have access to synchronized ..."
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Cited by 18 (2 self)
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We present the discrete beeping communication model, which assumes nodes have minimal knowledge about their environment and severely limited communication capabilities. Specifically, nodes have no information regarding the local or global structure of the network, do not have access to synchronized clocks and are woken up by an adversary. Moreover, instead on communicating through messages they rely solely on carrier sensing to exchange information. This model is interesting from a practical point of view, because it is possible to implement it (or emulate it) even in extremely restricted radio network environments. From a theory point of view, it shows that complex problems (such as vertex coloring) can be solved efficiently even without strong assumptions on properties of the communication model. We study the problem of interval coloring, a variant of vertex coloring specially suited for the studied beeping model. Given a set of resources, the goal of interval coloring is to assign every node a large contiguous fraction of the resources, such that neighboring nodes have disjoint resources. A kinterval coloring is one where every node gets at least a 1/k fraction of the resources. To highlight the importance of the discreteness of the model, we contrast it against a continuous variant described in [17]. We present an O(1) time algorithm that with probability 1 produces a O(∆)interval coloring. This improves an O(log n) time algorithm with the same guarantees presented in [17], and accentuates the unrealistic assumptions of the continuous model. Under the more realistic discrete model, we present a Las Vegas algorithm that solves O(∆)interval coloring in O(log n) time with high probability and describe how to adapt the algorithm for dynamic networks where nodes may join or leave. For constant degree graphs we prove a lower bound of Ω(log n) on the time required to solve interval coloring for this model against randomized algorithms. This lower bound implies that our algorithm is asymptotically optimal for constant degree graphs.
Transformations for writeallwithcollision model
 Computer Communications (Elsevier
, 2003
"... Dependable properties such as selfstabilization are crucial requirements in sensor networks. One way to achieve these properties is to utilize the vast literature on distributed systems where such selfstabilizing algorithms have been designed. Since these existing algorithms are designed in read/w ..."
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Cited by 17 (8 self)
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Dependable properties such as selfstabilization are crucial requirements in sensor networks. One way to achieve these properties is to utilize the vast literature on distributed systems where such selfstabilizing algorithms have been designed. Since these existing algorithms are designed in read/write model (or variations thereof), they cannot be directly applied in sensor networks. For this reason, we consider a new atomicity model, write all with collision (WAC), that captures the computations of sensor networks and focus on transformations from read/write model to WAC model and vice versa. We show that the transformation from WAC model to read/write model is stabilization preserving, and the transformation from read/write model to WAC model is stabilization preserving for timed systems. In the transformation from read/write model to WAC model, if the system is untimed (asynchronous) and processes are deterministic then under reasonable assumptions, we show that (1) the resulting program in WAC model can allow at most one process to execute, and (2) the resulting program in WAC model cannot be stabilizing.
Selfstabilizing deterministic TDMA for sensor networks
 PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING AND INTERNET TECHNOLOGY (ICDCIT), LNCS 3816
, 2005
"... An algorithm for time division multiple access (TDMA) is found to be applicable in converting existing distributed algorithms into a model that is consistent with sensor networks. Such a TDMA service needs to be selfstabilizing so that in the event of corruption of assigned slots and clock drift, ..."
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Cited by 16 (0 self)
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An algorithm for time division multiple access (TDMA) is found to be applicable in converting existing distributed algorithms into a model that is consistent with sensor networks. Such a TDMA service needs to be selfstabilizing so that in the event of corruption of assigned slots and clock drift, it recovers to states from where TDMA slots are consistent. Previous selfstabilizing solutions for TDMA are either randomized or assume that the topology is known upfront and cannot change. Thus, the question of feasibility of selfstabilizing deterministic TDMA algorithm where topology is unknown remains open. In this paper, we present a selfstabilizing, deterministic algorithm for TDMA in networks where a sensor is aware of only its neighbors. This is the first such algorithm that achieves these properties. Moreover, this is the first algorithm that demonstrates the feasibility of stabilizationpreserving, deterministic transformation of a shared memory distributed program on an arbitrary topology into a program that is consistent with the sensor network model.
Coloring Unstructured Wireless MultiHop Networks
 In PODC
, 2009
"... We present a randomized coloring algorithm for the unstructured radio network model, a model comprising autonomous nodes, asynchronous wakeup, no collision detection and an unknown but geometric network topology. The current stateoftheart coloring algorithm needs with high probability O(∆·log n) ..."
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Cited by 15 (4 self)
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We present a randomized coloring algorithm for the unstructured radio network model, a model comprising autonomous nodes, asynchronous wakeup, no collision detection and an unknown but geometric network topology. The current stateoftheart coloring algorithm needs with high probability O(∆·log n) time and uses O(∆) colors, where n and ∆ are the number of nodes in the network and the maximum degree, respectively; this algorithm requires knowledge of a linear bound on n and ∆. We improve this result in three ways: Firstly, we improve the time complexity, instead of the logarithmic factor we just need a polylogarithmic additive term; more specifically, our time complexity is O( ∆ + log ∆ · log n) given an estimate of n and ∆, and O( ∆ + log 2 n) without knowledge of ∆. Secondly, our vertex coloring algorithm needs ∆ + 1 colors only. Thirdly, our algorithm manages to do a distanced coloring with asymptotically optimal O(∆) colors for a constant d.