A Topology Control in Wireless Networks

Eiman Alotaibi

Department of Computer Science

University of California, Davis

11/13/2009 2

Network Design Problems

Problem Given Minimize w.r.t s.t

CA τ, λi,j T Ci,j D

FA τ, Ci,j T λi,j 0 ≤ λi,j ≤

µCi,j

CFA τ T Ci,j, λi,j D

TCFA - T τ, Ci,j, λi,j D

Co

mp

lex

ity

- τ = Network Topology - λi,j = flow on link (i,j)

- µ = average packet size - Ci,j = capacity of link (i,j)

- T = Average System Delay

- D = Maximum cost i,j i,j

(i,j) E

d C D

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 3

In Wireless Mesh Network

Each radio has a limited capacity

- This can be used as a constraint

instead of Cost Constraint

Wireless Channel is a shared channel

Interference limits the effective capacity

11/13/2009 4

Cross-Layer Design

CA in wireless network

should also take into

account Interference

Interference depends on

- Topology

- PHY Layer technology

- Antenna Beam pattern

Transport

“Flow Control”

Network

“Routing”

PHY/MAC

“Resource Allocation”

“Scheduling”

“Tx-Rx”

“Interference”

• Benefits of Cross Layer Design

• PHY layer limitations are considered

• Network resources are utilized to the best possible extent

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 5

Wireless Constraints

Primary Interference Constraint:

Signal-to-Interference-and-Noise Ratio (SINR) Constraint:

Self Interference Collision Multicast

t

i,j i,j

o p,q,i,j p,q(p,q) L

G P

N I P

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 6

Channel, Capacity, and Flow Assignment

(CCFA)

Given:

- Network Topology, source-destination demands γs,d

- Number of non-overlapping channels K

- Number of Network Interface Cards (NICs) on each node qi

Minimize: T

With respect to: {Ci,j}, {λi,j}, and Hi,j ∈ {1,…,K}

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 7

Network Utility

Efficiency of a WMN

Utility U is defined to include both throughput and delay

Em = “ Throughput emphasis factor ”

- How much is throughput emphasized over delay

Generalized version of Kleinrock’s “Power” of a network

s,d

s,d

Total Throughput

TotalDemand D D

Em

UT

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 8

Channel Assignment

Traffic Profiling

Multichannel Capacity

and Flow Assignment

(MCFA)

U(n)-U(n-1) ≤ ε

Yes

Channels

No

Channels, Capacities, and Flows

Capacities and Flows

Link Flows

Overall CCFA Algorithm

Ref: Channel, Capacity, and Flow Assignment in Wireless Mesh Networks

Presentation, by Vishwanath Ramamurthi

11/13/2009 9

Topology CFA

Given:

- Number of nodes and their locations

- Number of interfaces per node

- Source-destination traffic demands γs,d

Minimize: T

- With respect to: {Ci,j}, {λi,j}, and т

Output:

- Optimal Network Topology

11/13/2009 10

Why Topology CFA in WMN?

Fully

connected

Tree Star

No. of links high low low

Reliability high low low

Interference high low high

Power high low high

11/13/2009 11

Algorithm

Step1: Start with a fully connected Network

Step2: Apply CCFA

Step3: for each node ni, sort (in a descending order) the outgoing-link capacities

Step4: Select the minimum third-link capacity among all nodes to be the value of the threshold capacity (Cth)

Step5: Eliminate links with capacities less than a threshold (Cij < Cth), create new topology. If no link is eliminated, then stop and output the topology

Step6: Redistribute the capacities and flows of the deleted links by repeating steps 2-5 (input topology for step 2 in each iteration will be changed)

11/13/2009 12

Fully connected

Topology

CCFA

Cij < Cth for

all links

Eliminate

link ij

output: TopologyNo

Yes

For each node (ni), sort Cij for

all adjacent nodes (nj)

Calculate Cth

Cth = min(third-link capacity)

Create new

topology

Topology CFA

11/13/2009 13

Threshold (Cth)

Maintain at least 2-connected network

Cth has to be less than the second biggest link capacity

adjacent to any node

Cth is the third minimum link capacity among all nodes

11/13/2009 14

Threshold (Cth)

R1 R2 R3

R4 R5

1

5

4

7 9 8

10

12

1110

R1

C15 = 11

C14 = 10

C13 = 5

C12 = 1

R2

C25 = 9

C24 = 7

C23 = 4

C21 = 1

R3

C35 = 10

C34 = 8

C31 = 5

C32 = 4

R4

C45 = 12

C41 = 10

C43 = 8

C42 = 7

R5

C54 = 12

C51 = 11

C53 = 10

C52 = 9

11/13/2009 15

Testbed layout (Kemper Hall 2nd floor)

12f

12f

12f 48f60f60f

50f

12f

36f36f

38f

24f

GWGW

R1R4

R2

R3

R5

11/13/2009 16

Testbed layout (distances)

72 171.6

18.3

191

R4

290

157

138.3

200

221

179

221

242.9184

186

146

GW

R1R4

R2

R3

R5

11/13/2009 17

Tested Topologies

R1 R2 R3

R4 R5

Tree Topology

R1 R2 R3

R4 R5

GW GW

Star Topology

R1 R2 R3

R4 R5

4-connected Topology

R1 R2 R3

R4 R5

5-connected Topology

GW GW

11/13/2009 18

Tested Topologies

Option 2 Topology

GW

R1 R2 R3

R4 R5

11/13/2009 19

Assumptions

All links are located within one interference range

Single channel

Single radio per node

Traffic at each node follow the same pattern

(Du(i) = Dd(i) = xMbps)

11/13/2009 20

Results (2Mbps)Normalized Network Utility

0

0.2

0.4

0.6

0.8

1

1.2

5-Conn 4-Conn Option 2 Tree Star

Topology

U (

No

rmailzed

)

Aggregate Network Throughput

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

5-Conn 4-Conn Option 2 Tree Star

Topology

Ag

gre

gate

Th

rou

gh

pu

t

(Mb

ps)

Total Capacity Utilized

0

20

40

60

80

100

120

140

5-Conn 4-Conn Option 2 Tree Star

Topology

Cap

acit

y (

Mb

ps)

Network Delay

0

20

40

60

80

100

120

140

160

5-Conn 4-Conn Option 2 Tree Star

Topology

Dela

y (

ms)

11/13/2009 21

Results (12Mbps)Aggregate Network Throughput

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

5-Conn 4-Conn Option 2 Tree Star

Topology

Ag

gre

gate

Th

rou

gh

pu

t

(Mb

ps)

Total Capacity Utilized

0

20

40

60

80

100

120

140

5-Conn 4-Conn Option 2 Tree Star

Topology

Cap

acit

y (

Mb

ps)

Network Delay

0

20

40

60

80

100

120

140

160

5-Conn 4-Conn Option 2 Tree Star

Topology

Dela

y (

ms)

Normalized Network Utility

0

0.2

0.4

0.6

0.8

1

1.2

5-Conn 4-Conn Option 2 Tree Star

Topology

U (

No

rmali

zed

)

11/13/2009 22

Aggregate Network Throughput

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

5-Conn 4-Conn Option 2 Tree Star

Topology

Ag

gre

gate

Th

rou

gh

pu

t

(Mb

ps)

Total Capacity Utilized

0

20

40

60

80

100

120

140

5-Conn 4-Conn Option 2 Tree Star

Topology

Cap

acit

y (

Mb

ps)

Network Delay

0

20

40

60

80

100

120

140

160

5-Conn 4-Conn Option 2 Tree Star

Topology

Dela

y (

ms)

Normalized Network Utility

0

0.2

0.4

0.6

0.8

1

1.2

5-Conn 4-Conn Option 2 Tree Star

Topology

U (

No

rmali

zed

)

Results (54Mbps)

11/13/2009 23

Tested Topologies

Option 2 Topology

GW

R1 R2 R3

R4 R5

11/13/2009 24

ResultsNormalized Network Utility

0

0.2

0.4

0.6

0.8

1

1.2

5-Conn 4-Conn Option 2 Tree Star

Topology

U (

no

rmali

zed

)

2Mbps

12Mbps

54Mbps

Normalized (Log scale) Network Utiloity

0.0001

0.001

0.01

0.1

1

10

100

5-Conn 4-Conn Option 2 Tree Star

Topology

U (

No

rmali

zed

in

Lo

g

scale

) 2Mbps

12Mbps

54Mbps

11/13/2009 25

What is next!

Test the following cases:

- varies number of radios (available capacity)

- varies number of links

- varies the transmission power

- multi-channel

Develop TCFA mathematical equations

11/13/2009 26

Q&A

Thank you