Interference and Service Discovery in Multi-Hop Ad Hoc Networks

Alex VarshavskyUniversity of Toronto

2

Multi-Hop Mobile Ad Hoc Networks (MANETs)

Wireless medium Mobile nodes No fixed infrastructure Each node acts as router Applications

Relief operations Battlefield

A

F

3

4

Multi-hop Networks No Spatial Reuse

AFB

C D E

5

Multi-hop NetworksSpatial Reuse

AFB

C D E

6

Throughput Measurement

Chains of different length

Traffic pattern Constant Bit Rate (CBR)

……

7

0

100

200

300

400

500

600

700

800

900

40 104 168 232 296 360 424 488 552 616 680 744 808 872 936

Sending Rate (Kb/s)

Ave

rag

e T

hro

ug

hp

ut

(Kb

/s)

2 3 4 5 6 11

CBR Throughput

55%

Drop

8

Wireless Transmission

A B CDATA DATA

Collision

Hidden terminal

CSMA/CD doesn’t work

Use CSMA/CA

9

Interference Range

A B CDATA D

Interference Range = 550m

Transmission Range = 250m

10

The Hidden Terminal Problem

A B CDATA D E F

DATACollision

11

CBR Throughput

0

100

200

300

400

500

600

700

800

900

40 104

168

232

296

360

424

488

552

616

680

744

808

872

936

Sending Rate (Kb/s)

Ave

rag

e T

hro

ug

hp

ut (K

b/s

)

2 3 4 5 6 11

• Self-interference

• Throughput depends

• route length

• sending rate

12

13

MANET in Action

Gee…I wear a Video CameraCool !

I act as Video

Redirector

14

MANET in Action

I still wear a Video Camera

Now I act as Video Redirecto

r

15

Service Location Protocol (SLP)

Discover services Two modes of operation

Centralized Distributed

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Service Location Protocol (SLP)Centralized Mode

User Agent

Service Agent

DirectoryAgent

Camera Video RedirectorFind “video redirector” !

Register “video redirector”

Find “video redirector” !

Register “video redirector”

C

D

S1

S2

17

Service Location Protocol (SLP)Centralized Mode

User Agent

Service Agent

DirectoryAgent

Camera Video RedirectorFind “video redirector” !

Register “video redirector”

Find “video redirector” !

Register “video redirector”

C

D

S2

S1

18

Service Location Protocol (SLP)Centralized Mode

User Agent

Service Agent

DirectoryAgent

Camera Video RedirectorFind “video redirector” !

Register “video redirector”

Find “video redirector” !

Register “video redirector”

C

D

I found the video redirecto

r

S2

S1

19

Service Location Protocol (SLP)Distributed Mode

User Agent

Service Agent

Camera Video RedirectorFind “video redirector” !

Register “video redirector”

Find “video redirector” !

C

S1

S2

20

Service Location Protocol (SLP) Distributed Mode

User Agent

Service Agent

Camera Video RedirectorFind “video redirector” !

Register “video redirector”

Find “video redirector” !

C

I found the video redirecto

r

S1

S2

21

Service Discovery in MANETs

Centralized Hard to maintain Easy to lose

Distributed Large overhead Large overhead

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