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A-B. B-C. D-E. C-D. A. B. C. D. E. Minimum Interference Channel Assignment in Multi-Radio Wireless Mesh Networks. Anand Prabhu Subramanian, Rupa Krishnan, Samir R. Das, Himanshu Gupta, Computer Science Department SUNY at Stony Brook http://www.wings.cs.sunysb.edu. Motivation.

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slide1

A-B

B-C

D-E

C-D

A

B

C

D

E

Minimum Interference Channel Assignment in Multi-Radio Wireless Mesh Networks

Anand Prabhu Subramanian, Rupa Krishnan, Samir R. Das, Himanshu Gupta, Computer Science Department

SUNY at Stony Brook http://www.wings.cs.sunysb.edu

Motivation

  • When (v,w) in E is assigned i , then nodesv and w have atleast one radio assigned to i

Generate a random partition s;

bestCol = f(s); sol = s;

While <end condition>{

Generate η neighbors with moves not in tabu list;

choose the neighbor (s’) with minimum cost;

s = s’;

Add the move from s to s’ to tabu list;

If(f(s) < bestCol){

bestCol = f(s);

sol = s;

}

}

Conflict Graph

  • Increasing interest in using wireless mesh networks (WMNs) as backbone networks recently
  • Multihop nature of such wireless networks have a serious capacity problem [gupta & kumar]
  • Main cause - INTERFERENCE
  • Two interfering links can operate simultaneously in orthogonal channels

- 3 channels in 802.11b and 12 channels in 802.11a

  • Mesh routers can be equipped with multiple radios and operate on orthogonal channels to reduce interference
  • Interference in the network is modeled using a conflict graph
  • In the conflict graph Gc = (Vc,Ec), Vc = E
  • There is an edge between two node u,v in Vc if the edges represented by them in G interfere
  • We can represent a variety of interference models
  • The number of colors γ(i) assigned to a node i in G by the first phase is the number of distinct colors assigned to its edges
  • We define a violation metric as

α (i) = γ(i) - Ri

  • We take the edge-colored communication graph as input for phase II

Communication Graph

Conflict Graph

Problem Definition

  • Given K orthogonal channels and Ri radios in each node i in the network, design an efficient channel assignment algorithm that preserves

- Connectivity as in the single channel case

- Minimizes interference as much as possible

Sort the nodes in G in non-increasing order of violation

For each node i in V do

while α (i) > 0 do

Merge two edge-connected components of node i

which will give least increase in conflict

α (i) = α (i) - 1

  • Channel assignment problem – NP HARD
  • Our aim is to come up with an efficient heuristic

Channel Assignment Algorithm

Simulation

Problem Formulation

  • 50 node network in a 300x300m area
  • Transmission range 150m
  • 95% confidence interval shown
  • We consider a wireless mesh network with stationary wireless routers equipped with multiple radios
  • Network modeled as an undirected graph G=(V,E)
  • V is the vertex set and e =(v,w) is in E if u, v in V are within each others’ transmission range
  • K available channels numbered from 1 to K
  • Each node i has Ri radios where 1 < Ri <= K
  • Problem modeled as a constrained edge-coloring problem where each edge in E is assigned one of the K channels
  • Two phase algorithm
  • First Phase – K partition the conflict graph
  • This phase does not consider that each node has limited number of radios (interface constraint)
  • A feasible solution is any K partition of Vc
  • Let I(Si) be the edges in Ec that have both end points in Si
  • The cost f(s)of the solution s is
  • We need to find a solution s with minimum f(s)

S={S1,…,Sk}

Future Work

  • Design Centralized Approximation Algorithm
  • Design Distributed Algorithm
  • Implement in real test bed

ICNP 2005

Anand Prabhu Subramanian { anandps@cs.sunysb.edu }