11/14/ 2006 ICNP 2006 1

Virtual Surrounding Face Geocasting with Guaranteed Message Delivery for Ad Hoc and Sensor Networks

Jie Lian, Kshirasagar NaikUniversity of Waterloo, ON, Canada

Yunhao Liu, Lei ChenThe Hong Kong University of Science and Technology,

Hong Kong, China

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Sensor Networks

Sink

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Geocasting in Sensor Networks

end usersquery

respons

e

sink

sensor

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Existing Approaches: Restricted Flooding

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Existing Approaches

• Approaches with delivery guarantee

– DFFTT: Depth-First Face Tree Traversal

– RFIFT: Restricted Flooding with Intersected Face

Traversal

– EZMG: Entrance Zone Multicasting-based Geocasting

– Drawbacks :Complex, longer delivery time, high

message cost, potentially series contention.

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RFIFT Basic

s

Some concerns:• Cost• Potential collision• Delivery speed

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Another Problem in RFIFT

s

Region

uy

• In some cases, RFIFT needs to be modified to guarantee message delivery

y

z

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Our Goals

• Guaranteed message delivery

• Short delivery time

• Low transmission cost

• Avoid potential message collisions

• Reducing message complexity of RFIFT:

– (3n +k) 2n+k (hopefully!)

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Virtual Surround Face (VSF)

u

v

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Example of VSF Geocasting

su

w

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Termination Condition

y

s

Region g

MSG1

MSG2

h

f

MSG1(h, Right)

MSG2(f, Left)

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v

y

Special Case 1 in VSFG

• Boundary of VSF connected via internal nodes z & t

s

Region

xu

w

t g

z

Component 2Component 1

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Special Case 2 of VSFG

• VSF connected via external crossing edge yu

v

s

Region

xuw

y

z

Component 2Component 1

g

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Special Case 2 in RFIFT

• RFIFT has much longer delivery time

s

Region x

u

34 time slots in RFIFT vs 12 time slots in VSFG

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Asymptotical bound of VSFG

• The message complexity of VSF traversal is

bounded by 2n, where n is the number of nodes

located on VSF boundary.

• The message complexity of face traversal in

RFIFT is bounded by 3n.

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Simulation Setup• Two types of simulated networks

– Random network: randomly deployed node in a 20 20 square area.– Void network: From random networks, a number of 1.5 1.5 square

voids are randomly generated and all nodes within voids are removed.

• Geocasting region: randomly generated rectangular regions• Performance metric: number of messages required

Void network with 15 voids Void network with 30 voids

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0

5

10

15

20

25

0 10 20 30 40 50

Average degree of network

VSF

IFT

0

11

22

33

44

0 10 20 30 40 50

Average degree of network

VSF

IFT

Simulation Results: Random Network

0

4

8

12

16

20

24

0 10 20 30 40 50

Average degree of network

VSF

IFT

0

3

6

9

12

15

0 10 20 30 40 50

Average degree of network

VSF

IFT

Average degree of network Average degree of network

Fac

e tr

aver

sal c

ost

(T

hou

san

ds)

Tot

al c

ost

of g

eoca

stin

g(T

hou

san

ds)

Average degree of network Average degree of network

Fac

e tr

aver

sal c

ost

(T

hou

san

ds)

Tot

al c

ost

of g

eoca

stin

g(T

hou

san

ds)

Costs for base networks with 5 2.5 geocasting regions

Costs for base networks with 3 1.5 geocasting regions

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0

4

8

12

16

20

0 10 20 30 40 50

Average degree of network

VSF-C

IFT-C

VSF-Cf

IFT-Cf

0

4

8

12

16

20

0 10 20 30 40 50

Average degree of network

VSF-C

IFT-C

VSF-Cf

IFT-Cf

Simulation Results: Void Network

Average degree of network Average degree of network

Cos

t of

geo

cast

ing

(T

hou

san

ds)

Cos

t of

geo

cast

ing

(Th

ousa

nd

s)Void networks with 15 voids and 3 1.5 regions Void networks with 30 voids and 3 1.5 regions

VSF-C: total cost of VSFG

VSF-Cf: face traversal cost of VSF

IFT-C: total cost of RFIFT

IFT-Cf: face traversal cost of RFIFT

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Conclusion

• Design of VSF

• Guaranteed message delivery

• Fast delivery due to concurrent double directional

traversal

• Low transmission cost

• Low probability of collision occurrences

• Scalability

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Future Work

• Reducing face traversal cost by designing shortcut algorithm

• Designing localized dominating-set based flooding algorithm

to replace restricted flooding in VSFG.

• Analyzing the impact of location errors on VSFG and

providing respective solutions.

• Studying VSFG on realistic network model, not unit disk

graphs.

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Termination Condition• Observation

– When a node starting a VSF traversal by using Right- and Left-hand simultaneously, the two traversal messages with eventually meet at a node on the boundary VSF.

• Precondition– A VSF node u receives a traversal message from node v MSG1(v, Rule1) but not been forwarded to next node yet.

– Node u receives another traversal message MSG(w, Rule2).

• Termination Condition– If the next visited node of MSG1 is w;

– If the next visited node of MSG2 is v;

– If Rule1 is not same as Rule2;

– Node u terminates the face traversal (discards MSG1 and MSG2).

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Unit Disk Graph and Planar Graph

• Unit disk graph (UDG)– Identical transmission range, which is treated as unity.

– Two nodes are neighbors if their distance is less than 1.

– Simplified network model

• Planar graph– A graph without two edges crossing one another

– Example planar graphs deduced from UDG:

• Relative neighborhood graph (RNG)

• Gabriel graph (GG)

• Unit Delaney Triangulation (UDel)

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Planar GraphsUDG

GGRNG UDel

Two nodes can find if they are RNG/GG neighborsBy their local knowledge.

However nodes can not do the same thing in UDel.

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Face and Face Traversal in GG

• Four faces: F1, F2, F3, and F4, where F4 is an exterior face (open area)

• Traversing F1 by using Right-Hand rule starting from u

v

F3

F1

F4

u

z

w

x

y

F2

u1

u2 u3

u5

u6

u7

u8u9u10

u11

u12

u13

v1

v2v4

v3

u4

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VSF Geocasting

• VSF Forwarding– A source node s selects a geographical point in a geocasting region

closest to the source node as the destination reference point p.

– Node s transmits a geocasting message towards p by using location-based routing until a node u on the boundary of the VSF is found.

• VSF Traversal (Double direction traversal)– Node u as chosen above starts VSF traversal using Right-hand rule

and Left-hand rule simultaneously.

• VSF Restricted Flooding– Each node in the geocasting region overhearing a geocasting

message for the first time broadcasts the message.