2006 9 14 kim young hoon
This presentation is the property of its rightful owner.
Sponsored Links
1 / 22

2006/9/14 Kim Young Hoon PowerPoint PPT Presentation


  • 44 Views
  • Uploaded on
  • Presentation posted in: General

A Topology Control Approach for Utilizing Multiple Channels in Multi-Radio Wireless Mesh Networks (broadnet2005) Mahesh K. Marina, Samir R. Das. 2006/9/14 Kim Young Hoon. Contents. Introduction Problem Formulation Channel Assignment Algorithm Simulations Results Conclusions. Contents.

Download Presentation

2006/9/14 Kim Young Hoon

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


2006 9 14 kim young hoon

A Topology Control Approach for Utilizing Multiple Channels in Multi-Radio Wireless Mesh Networks (broadnet2005)Mahesh K. Marina, Samir R. Das

2006/9/14

Kim Young Hoon


Contents

Contents

  • Introduction

  • Problem Formulation

  • Channel Assignment Algorithm

  • Simulations Results

  • Conclusions


Contents1

Contents

  • Introduction

  • Problem Formulation

  • Channel Assignment Algorithm

  • Simulations Results

  • Conclusions


Introduction

Introduction

  • Wireless mesh networks

    • Wired router nodes/wireless nodes

    • No need of infrastructure

    • Wider coverage

  • Mesh networks with multi-hop extension of 802.11 standard

    • Different from 802.11 LANs: risk of disconnection

    • All nodes use same channel in mesh for connectivity

  • Inefficient Utilization of Available Channels

  • Need to use Multiples Channels


Introduction1

Introduction

  • Single radio for multiple channels?

    Possible. But need of ...

    • Dynamically switch between channels

    • Tight time synchronization among nodes

      • Slow switching

         reducing synchronization requirements and overhead,

         increasing end-to-end delay

    • Require MAC or hardware modification

  • Therefore, Multiple radios per node

    • Effective use of given channels

    • Overcoming the deficiencies of single radio


Introduction2

Introduction

  • What happens in multi-radio mesh network?

    • Disconnection between nodes can happen

    • Node’s transmission is interfered by other nodes’

  • So, a key issue in multi-radio mesh network architecture is Channel Assignment Problem.


Introduction3

Introduction

  • Channel Assignment Problem

    • has to balance between connectivity and interference

    • is viewed as topology control problem (adjustable links between nodes in wireless)

      In this paper, authors proposed base channel assignment

      to obtain an initial, well-connected topology.


Contents2

Contents

  • Introduction

  • Problem Formulation

  • Channel Assignment Algorithm

  • Simulations Results

  • Conclusions


Problem formulation

Problem Formulation

  • Channel Assignment Problem belongs to the class of NP-complete

    Proof flow)

Channel Assignment Problem

Topology Control Problem

Topology Control’s Target

 Reducing Interference

Channel Assignment Problem

 Optimization Problem

Optimization Problem

 Decision Problem

Showing that decision problem is in NP-complete (using minimum edge coloring)

For more detail, see 2nd part of the paper


Channel assignment algorithm

Channel assignment algorithm

  • CLICA (Connected Low Interference Channel Assignment)

    • Polynomial time heuristic

    • Order nodes by their degree of flexibility

      • degree of flexibility: amount of freedom when choosing channel

    • Greedily assign channel between nodes


Channel assignment algorithm1

Coloring uncolored links with a common color to already assigned radios

Coloring nodes which have no available radios

Greedily coloring uncolored links

Channel assignment algorithm


Channel assignment algorithm case 1

Channel assignment algorithm - case 1

Initial order: a-d-c-b

  • Starting from a, assign channel a-b, b’s priority bumps up

  • Assign channel b-c, and c-d in similar manner

  • Node a and d have a common channel, so assign that to a-d

<1>

<5>

b

a

c

<2>

<6>

<4>

d

<7>

<3>


Channel assignment algorithm case 2

Channel assignment algorithm - case 2

Node a and d has two radios

  • Starting from a, assign channel a-b, b’s priority bumps up

  • Assign channel b-c, and c-d in similar manner

  • Node a and d have additional radios, so assign different channel to a-d

<1>

<5>

b

a

c

<2>

<6>

<4>

d

<7>

<3>


Channel assignment algorithm2

Channel assignment algorithm

  • Each coloring decision is made in a greedy fashion

    • Locally optimal choice

  • Theorem 2: CLICA algorithm yields a connectivity preserving color assignment


Contents3

Contents

  • Introduction

  • Problem Formulation

  • Channel Assignment Algorithm

  • Simulations Results

  • Conclusions


Simulation results part 1

Simulation Results – part 1

  • Graph-based simulations

    • Interference and capacity properties of topologies generated by different channel assignment algorithms

      • Compared with CCA (Common Channel Assignment – assign same set of channelr to all nodes)

    • Measure:

      • Maximum link conflict weight – network wide interference

      • Maximum number of concurrent transmissions – total one-hop capacity


Simulation results part 11

Simulation Results – part 1

  • CCA

    • CCA interference performance is unaffected by the number of channels

    • CCA capacity performance shows a linear growth

  • CLICA

    • As the number of radios increases, interference goes up and capacity shows marginal perfromance

    • Minimum interference doesn’t match maximum capacity

      DUE TO HEURISTIC NATURE


Simulation results part 2

Simulation Results – part 2

  • Ns-2 simulations

    • Evaluating the performance of CLICA

    • Aggregate throughput and average delay

    • 50 nodes with 250m TX range in 1000m x 1000m

    • 550m interference range

    • 802.11 physical layer model in ns-2

    • Fixed data rate of 2Mbps


Simulation results part 2 single hop performance

Simulation Results – part 2: Single hop performance


Simulation results part 2 multihop performance

Simulation Results – part 2: Multihop performance


Conclusions

Conclusions

  • The authors

    • have formulated base channel assignment as a topology control optimization problem

    • solved the channel assignment (radio-channel mapping) problem in greedy way (called CLICA)

    • shows the interference-reducing results by simulations


2006 9 14 kim young hoon

Q&A


  • Login