Information Gathering in Ad-Hoc Radio Networks with Tree Topology

Chrobák, Marek; Costello, Kevin P.; Gąsieniec, Leszek; Kowalski, Dariusz R.

doi:10.1007/978-3-319-12691-3_11

Cited by 3 publications

(13 citation statements)

References 22 publications

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“…In this model, we give a deterministic algorithm that completes information gathering in time O(n log log n). Our result significantly improves the previous upper bound of O(n log n) from [5]. To our knowledge, no lower bound for this problem is known, apart from the trivial bound of Ω(n) (since each rumor must be received by the root in a different time step).…”

Section: Introductionsupporting

confidence: 56%

“…Related work. The problem of information gathering for trees was introduced in [5], where the model without any collision detection was studied. In addition to the O(n log n)-time algorithm without aggregation -that we improve in this paper - [5] develops an O(n)-time algorithm for the model with aggregation, where a message can include any number of rumors.…”

Section: Introductionmentioning

confidence: 99%

“…The problem of information gathering for trees was introduced in [5], where the model without any collision detection was studied. In addition to the O(n log n)-time algorithm without aggregation -that we improve in this paper - [5] develops an O(n)-time algorithm for the model with aggregation, where a message can include any number of rumors. Another model studied in [5], called fire-and-forward, requires that a node cannot store any rumors; a rumor received by a node has to be either discarded or immediately forwarded.…”

Section: Introductionmentioning

confidence: 99%

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Faster Information Gathering in Ad-Hoc Radio Tree Networks

Chrobák

Costello

2017

Algorithmica

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We study information gathering in ad-hoc radio networks. Initially, each node of the network has a piece of information called a rumor, and the overall objective is to gather all these rumors in the designated target node. The ad-hoc property refers to the fact that the topology of the network is unknown when the computation starts. Aggregation of rumors is not allowed, which means that each node may transmit at most one rumor in one step.We focus on networks with tree topologies, that is we assume that the network is a tree with all edges directed towards the root, but, being ad-hoc, its actual topology is not known. We provide two deterministic algorithms for this problem. For the model that does not assume any collision detection nor acknowledgement mechanisms, we give an O(n log log n)-time algorithm, improving the previous upper bound of O(n log n). We also show that this running time can be further reduced to O(n) if the model allows for acknowledgements of successful transmissions. IntroductionWe study the problem of information gathering in ad-hoc radio networks. Initially, each node of the network has a piece of information called a rumor, and the objective is to gather all these rumors, as quickly as possible, in the designated target node. The nodes communicate by sending messages via radio transmissions. At any time step, several nodes in the network may transmit. When a node transmits a message, this message is sent immediately to all nodes within its range. When two nodes send their messages to the same node at the same time, a collision occurs and neither message is received. Aggregation of rumors is not allowed, which means that each node may transmit at most one rumor in one step.The network can be naturally modeled by a directed graph, where an edge (u, v) indicates that v is in the range of u. The ad-hoc property refers to the fact that the actual topology of the network is unknown when the computation starts. We assume that nodes are labeled by integers 0, 1, ..., n − 1. An information gathering protocol determines a sequence of transmissions of a node, based on its label and on the previously received messages.Our results. In this paper, we focus on ad-hoc networks with tree topologies, that is the underlying ad-hoc network is assumed to be a tree with all edges directed towards the root, although the actual topology of this tree is unknown.

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Section: Introductionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Faster Information Gathering in Ad-Hoc Radio Tree Networks

Chrobák

Costello

2017

Algorithmica

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“…Depending on more specific characteristics of this shared channel, one can model this problem as the information gathering problem either on a complete graph or a star graph, which is a collection of n nodes connected by directed edges to the target node t. (See [23,24,13] for information about contention resolution protocols.) For instance, in [5] a tight bound of Θ(n log n) was given for randomized information gathering on star graphs (or MACs) even if the nodes have no labels (are indistinguishable) and receive no feedback.…”

Section: Additional Context and Motivationsmentioning

confidence: 99%

“…The problem of information gathering for trees was introduced in [5], where an O(n)time algorithm was presented. Other results in [5] include algorithms for the model without rumor aggregation or the model with transmission acknowledgements.…”

Section: Introductionmentioning

confidence: 99%

Information gathering in ad-hoc radio networks with tree topology

Chrobák

Costello

Gąsieniec

et al. 2018

Information and Computation

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We study the problem of information gathering in ad-hoc radio networks without collision detection, focussing on the case when the network forms a tree, with edges directed towards the root. Initially, each node has a piece of information that we refer to as a rumor. Our goal is to design protocols that deliver all rumors to the root of the tree as quickly as possible. The protocol must complete this task within its allotted time even though the actual tree topology is unknown when the computation starts. In the deterministic case, assuming that the nodes are labeled with small integers, we give an O(n)-time protocol that uses unbounded messages, and an O(n log n)-time protocol using bounded messages, where any message can include only one rumor. We also consider fire-and-forward protocols, in which a node can only transmit its own rumor or the rumor received in the previous step. We give a deterministic fire-andforward protocol with running time O(n 1.5 ), and we show that it is asymptotically optimal. We then study randomized algorithms where the nodes are not labelled. In this model, we give an O(n log n)-time protocol and we prove that this bound is asymptotically optimal.

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