New distributed algorithm for connected dominating set in wireless ad hoc network
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New Distributed Algorithm for Connected Dominating Set in Wireless Ad Hoc Network. Khaled M. Alzoubi, Peng-Jun Wan, Ophir Frieder Proceedings of the 35 th Hawaii International Conference on System Sciences, Jan. 2002. 93321530 游精允. 2005/06/07. Outline. Introduction

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New distributed algorithm for connected dominating set in wireless ad hoc network

New Distributed Algorithm for Connected Dominating Set in Wireless Ad Hoc Network

Khaled M. Alzoubi, Peng-Jun Wan, Ophir Frieder

Proceedings of the 35th Hawaii International Conference on System Sciences, Jan. 2002

93321530

游精允

2005/06/07


Outline
Outline Wireless Ad Hoc Network

  • Introduction

  • Lower Bound on Message Complexity

  • Algorithms

    • Das et al’s algorithm

    • Wu and Li’s algorithm

    • Stojmenovic et al’s algorithm

    • Main algorithm

  • Conclusion

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Introduction
Introduction Wireless Ad Hoc Network

  • Unit-disk graph:

    A geometric graph in which there is an edge between

    two nodes if and only if their distance is at most one.

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  • Dominating set: Wireless Ad Hoc Network

    Given a graph G = (V, E), a dominating set of G is a subset D ⊆ V, such that .

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  • Connected dominating set: Wireless Ad Hoc Network

    (1) CD is a dominating set of G.

    (2) G[D], the subgraph induced by D is connected.

    Minimum connected dominated set (MCDS)

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Lower bound on message complexity
Lower Bound on Message Complexity Wireless Ad Hoc Network

  • Theorem 1: [2] In asynchronous rings with point-to-point transmission, any distributed algorithm for leader election in sends at least (n log n) messages.

  • Theorem 2/3/4: In asynchronous wireless ad hoc networks whose unit-disk graph is a ring, any distributed algorithm for leader election / spanning tree / nontrivial CDS sends at least (n log n) messages.

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Algorithms
Algorithms Wireless Ad Hoc Network

  • Das et al’s algorithm (1997)

  • Wu and Li’s algorithm (1999)

  • Stojmenovic et al’s algorithm (2001)

  • Main algorithm (2002)

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Das et al s algorithm

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Das et al’s algorithm

  • Greedily finds a minimal dominated set.

  • Then finds a MST and output its internal nodes.

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deg( Wireless Ad Hoc Networkvk) = 2k+k+1

deg(u1) = 2k+k

deg(vk–1) = 2k–1

deg(u1) = 2k–1–1

CDS: {v1, v2, … , vk}

optCDS: {u1, u2}

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  • Since Wireless Ad Hoc Networkn = k + 2k+1, the lower bounds is (lg n)/2–1 of the algorithm. (ratio = O(lg n))

  • Message complexityO(n2).

  • Time complexity O(n2).

  • The implementation lacks lack mechanisms to bridge two consecutive stages.

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Wu and li s algorithm

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Wu and Li’s algorithm

  • The initial connected dominating set U consists of all nodes which have at least two non-adjacent neighbors.

  • Locally redundant:

    It has either a neighbor in U with larger ID which dominates

    all other neighbors of u, or two adjacent neighbors with larger

    IDs which together dominates all other neighbors of u.

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|CDS| = Wireless Ad Hoc Networkn

|optCDS| = 2

ratio = n/2

  • Message complexityO(n2).

  • Time complexity O(3).

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Stojmenovic et al s algorithm

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Stojmenovic et al’s algorithm

  • Independent set:

    Given a graph G = (V, E), a independent set of G is a subset S ⊆ V, such that no two vertices of S are adjacent in G.

    • A maximal independent set is a independent dominating set

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  • Each node has a unique rank parameter as the ID.

  • Each node which has the lowest rank among all neighbors broadcasts a message declaring itself as a cluster-head.

  • Whenever a node receives a message for the first time from a cluster-head, it broadcasts a message giving up the opportunity as a cluster-head.

  • Whenever a node has received the giving-up messages from all of its neighbors with lower ranks, if there is any, it broadcasts a message declaring itself as a cluster-head.

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  • After a node learns the status of all neighbors, it joins the cluster centered at the neighboring cluster-head with the lowest rank by broadcasting the rank of such cluster head. The border-nodes are those which are adjacent to some node from a different cluster.

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1 Wireless Ad Hoc Network

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|CDS| = n

|optCDS| = 1

ratio = n

  • Message complexityO(n) ~ O(n2).

  • Time complexity O(n) ~ O(n2).

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Main algorithm mis

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Main algorithm (MIS)

  • The distributed leader election algorithm. (1998)

    • O(n) time complexity and O(n log n) message complexity, to construct a rooted spanning tree T rooted at a node v.

  • Each node identifies its tree level with respect to T.

  • The ranks of all nodes are sorted in the lexicographic order.

  • Message complexityO(nlogn).

  • Time complexity O(n).

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  • Theorem 7: The distance between any pair of complementary subsets of U is exactly two hops.

    Proof(1/2): Let U = {ui: 1 ik} where ui is the ith node which is marked red. For any 1 jk, let Hj be the graph over {ui: 1 ij} in which a pair of nodes is connected by an edge if and only if their graph distance in G is two.

    Since H1 consists of a single vertex, it is connected trivially.

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  • Theorem Wireless Ad Hoc Network 7: The distance between any pair of complementary subsets of U is exactly two hops.

    • Proof(2/2): Assume that Hj-1 is connected for some j 2. When the node uj is marked red, its parent in T must be already marked orange. Thus, there is some node ui with 1 i < j which is adjacent to uj ’s parent in T. So (ui, uj) is an edge in Hj. As Hj-1 is connected, so must be Hj.

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  • Lemma Wireless Ad Hoc Network8: The size of any independent set in a unit-disk graph G = (V, E) is at most 4opt + 1.

    (opt = |MCDS|)

  • Proof(1/2): Claim: Any independent set size is at most 5opt.

    Let U be any independent set of V , and let T* be any spanning tree of an MCDS. Consider an arbitrary preorder traversal of T given by v1, v2, …, vopt.

U

U1

U2

……

Uopt

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  • Lemma Wireless Ad Hoc Network8: The size of any independent set in a unit-disk graph G = (V, E) is at most 4opt + 1.

    (opt = |MCDS|)

  • Proof(2/2): Let U1 be the set of nodes in U that are adjacent to v1. For any 2 iopt, let Ui be the set of nodes in U that are adjacent to vi but none of v1, v2, …, vi-1. |U1|  5, For any 2 iopt, at least one node in v1, v2, …, vi-1 is adjacent to vi. This implies that |Ui|  4.

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Main algorithm dominating tree

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Main algorithm (Dominating Tree)

  • Message complexityO(n log n).

  • Time complexity O(n).

    ratio = 2|U| – 1

    = 2(4opt + 1) – 1

    = 8opt + 1

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Conclusion
Conclusion Wireless Ad Hoc Network

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