Dominating Set Based Support for Distributed Services in Mobile Ad Hoc Networks

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Dominating Set Based Support for Distributed Services in Mobile Ad Hoc Networks

Károly Farkas, Florian Maurer, Lukas Ruf,

Bernhard Plattner

5

^th

April, 2006, Vancouver

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Introduction

Popularity of mobile devices and ubiquitous environments

Emergence of self-organized and ad hoc communication paradigms

- Popularity of mobile devices and ubiquitous environments

- Emergence of self-organized and ad hoc communication paradigms

Support for Distributed Services

in Mobile Ad Hoc Networks

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Contribution Overview

Zone-Based Game Architecture

By the aid of graph theory

● Zone Server selection via Dominating Set (DS) computation

● Maintenance of the zones and Zone Servers in case of topology changes

Support for Distributed Services in Mobile Ad Hoc Networks

But How?

Zone-Based Game Architecture

By the aid of graph theory

● Zone Server selection via Dominating Set (DS) computation

● Maintenance of the zones and Zone Servers in case of topology changes

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Outline

Introduction

Zone-Based Game Architecture

Priority Based Selection (PBS) Algorithm

Performance of PBS

Conclusions and Future Work

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Zone-Based Game Architecture

Zone Red Zone Green

Introduction Zone-based Arch. PBS Alg. Performance of PBS Conclusions

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Challenges

Create the zones in the network

Select the Zone Server nodes

Maintain the zones and Zone Servers in case of dynamic topology changes

- Create the zones in the network

- Select the Zone Server nodes

- Maintain the zones and Zone Servers in case of dynamic topology changes

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Our Approach

Compute and maintain a Dominating Set (DS) of the network graph ⇒ Priority Based

Selection (PBS) algorithm

Dominator Dominatee S={3,5}

Dominating Set: For a graph G=(V, E), a DS is a subset S ⊆ V, such that for all nodes v ∈ V, either v ∈ S or a neighbor u of v is in S

1

2 4 6 7

3 5

Zone Green

Zone Red

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Assumptions for Zone Server Selection

Ad hoc network

● Not fragmented

● Knowledge about the neighbor nodes (routing protocol)

Nodes

● Unique ID

● Node weight

● Co-operative behavior

Ad hoc network

● Not fragmented

● Knowledge about the neighbor nodes (routing protocol)

Nodes

● Unique ID

● Node weight

● Co-operative behavior

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Requirements for Zone Server Selection

Dominating Set

● Minimum 2 nodes

● Node weighted

● Good Minimum Dominating Set (MDS) approximation

Algorithm

● Completely distributed

● Update mechanism for mobility maintenance

● Low time and message complexity

Dominating Set

● Minimum 2 nodes

● Node weighted

● Good Minimum Dominating Set (MDS) approximation

Algorithm

● Completely distributed

● Update mechanism for mobility maintenance

● Low time and message complexity

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Priority Based Selection (PBS) Algorithm

A node can be in one of the following states:

● DOMINATOR (Server)

● DOMINATEE (Client)

● INT_CANDIDATE (Internal Candidate)

● EXT_CANDIDATE (External Candidate)

A node can be in one of the following states:

● DOMINATOR (Server)

● DOMINATEE (Client)

● INT_CANDIDATE (Internal Candidate)

● EXT_CANDIDATE (External Candidate)

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Main Idea Behind the PBS Algorithm

status = INT_CANDIDATE or EXT_CANDIDATE;

while v has INT_CANDIDATE neighbors within distance 2 do - send neighborlist;

- receive neighborlist;

- change to DOMINATEE, if neighbor is DOMINATOR;

- change to DOMINATOR, if v has highest priority within distance 2 among the nodes with INT_CANDIDATE status;

od

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Priority Computation

A node has higher priority than another if

● the node has higher node weight;

● if tie: the node has higher span value (INT_CANDIDATE neighbors);

● if tie: the node has more neighbors with DOMINATOR status;

● if tie: the node has a lower ID.

A node has higher priority than another if

● the node has higher node weight;

● if tie: the node has higher span value (INT_CANDIDATE neighbors);

● if tie: the node has more neighbors with DOMINATOR status;

● if tie: the node has a lower ID.

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Mobility Maintenance in the PBS Algorithm

msgsent

roundfinished

finished

s1

s2

s3

Receive neighborlists

Status determined Send neighborlist

Send neighborlist

Determine status

Change happened, Send neighborlist

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Analysis of the PBS Algorithm Building an initial DS:

O(k(Δ+1)) Message size per round:

Lower bound: Ω(3) Upper bound: O(n) Rounds:

Optional Connected DS

O(n) Messages per round:

O(log Δ) MDS approximation:

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State-Of-The-Art DS Computation Algorithms

*The values in the highlighted area are the same as in case of PBS

N/A N/A

PBS O(n) O(n) messages, size O(k(Δ+1)) No O(logΔ)

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Performance of the PBS Algorithm

Simulation settings*

● Network Simulator NS-2, Version 2.28

● 3 scenarios (School Yard, Train, Test)

● 15 and 35 nodes forming the network

● Adapted mobility models

● Typical real-time multiplayer game traffic between player nodes

● Background traffic

● Game sessions of 900 seconds

Simulation settings*

● Network Simulator NS-2, Version 2.28

● 3 scenarios (School Yard, Train, Test)

● 15 and 35 nodes forming the network

● Adapted mobility models

● Typical real-time multiplayer game traffic between player nodes

● Background traffic

● Game sessions of 900 seconds

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Simulation Results in Detail (1/2)

Scenario Avg.

[kbps]

S. dev.

[kbps]

School Yard w/15 nodes 0.040 0.012 0.090 1.322 0.042 0.182 Train w/15 nodes

0.008 0.003 0.015 0.180 0.011 Test w/15 nodes

School Yard w/35 nodes Train w/35 nodes

Test w/35 nodes 0.053

Scenario Avg.

[ms]

S. dev.

[ms]

School Yard w/15 nodes 159 111 185 283 153 510 Train w/15 nodes

0.172 0.178 0.188 0.251 0.193 Test w/15 nodes

Test w/35 nodes 0.311

Bandwidth (total = 2 Mbps): Determination delay:

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Simulation Results in Detail (2/2)

Scenario Avg. S. dev.

School Yard w/15 nodes 0.6 1.6 0.8 3.6 4.4 Train w/15 nodes

0.5 1.3 0.6 0.8 1.2 Test w/15 nodes

Number of DS changes:

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Bandwidth

● 0.02-0.6 % of 2 Mbit/s

● Will not cause any problems

Determination delay

● ~100-500 ms depending on the number of 1-hop neighbors

Number of DS changes

● Relatively small in scenarios with few nodes

● Increases with the increasing number of nodes and higher mobility level

Summary of Simulation Results

Bandwidth

● 0.02-0.6 % of 2 Mbit/s

● Will not cause any problems

Number of DS changes

● Relatively small in scenarios with few nodes

● Increases with the increasing number of nodes and higher mobility level

Determination delay

● ~100-500 ms depending on the number of 1-hop neighbors

*More simulation results in the Proceedings

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Conclusions

PBS computes a close to minimal node weighted DS with similar performance to the state-of-art DS computation algorithms

PBS offers continuous maintenance of the computed DS

The computed DS can be used for creating a zone-based distributed service architecture

- PBS computes a close to minimal node weighted DS with similar performance to the state-of-art DS computation algorithms - PBS offers continuous maintenance of the

computed DS

- The computed DS can be used for creating a zone-based distributed service architecture

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Future Work

PBS enhancements

● Include a more sophisticated weight computation method

● Include mobility prediction

Scenarios

● Test PBS in more realistic mobility scenarios

Testbed measurements

● Investigate the performance of PBS in real environment

PBS enhancements

● Include a more sophisticated weight computation method

● Include mobility prediction

Scenarios

● Test PBS in more realistic mobility scenarios

For more information visit: www.siramon.org

Testbed measurements

● Investigate the performance of PBS in real environment

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