Transcript Virtual Surrounding Face Geocasting with Guaranteed

Virtual Surrounding Face Geocasting with
Guaranteed Message Delivery for Ad Hoc
and Sensor Networks
Jie Lian, Kshirasagar Naik
University of Waterloo, ON, Canada
Yunhao Liu, Lei Chen
The 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
query
end users
sink
response
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
Some concerns:
• Cost
• Potential collision
• Delivery speed
s
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Another Problem in RFIFT
• In some cases, RFIFT needs to be modified to
guarantee message delivery
y
Region
z
u
y
s
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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
w
u
s
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Termination Condition
MSG2
f
Region
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MSG1(h, Right)
h
y
s
MSG2(f, Left)
g
MSG1
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Special Case 1 in VSFG
• Boundary of VSF connected via internal nodes z & t
v
w
x
u
g
t
Region
z
y
Component 1
Component 2
s
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Special Case 2 of VSFG
• VSF connected via external crossing edge yu
w
v
u
x
Region
g
Component 1
s
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Component 2
y
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Special Case 2 in RFIFT
• RFIFT has much longer delivery time
Region
x
u
s
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
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Void network with 30 voids
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Simulation Results: Random Network
Average degree of network
Total cost of geocasting
(Thousands)
Face traversal cost
(Thousands)
Costs for base networks with 3  1.5 geocasting regions
Average degree of network
Average degree of network
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Total cost of geocasting
(Thousands)
Face traversal cost
(Thousands)
Costs for base networks with 5  2.5 geocasting regions
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Simulation Results: Void Network
IFT-C: total cost of RFIFT
IFT-Cf: face traversal cost of RFIFT
Cost of geocasting
(Thousands)
Cost of geocasting
(Thousands)
VSF-C: total cost of VSFG
VSF-Cf: face traversal cost of VSF
Average degree of network
Average degree of network
Void networks with 15 voids and 3  1.5 regions
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Void networks with 30 voids and 3  1.5 regions
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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
–
–
–
–
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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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UDG
Planar Graphs
Two nodes can find if they are RNG/GG neighbors
By their local knowledge.
However nodes can not do the same thing in UDel.
GG
RNG

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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
u2
F4
F3
u
y
x
u13
v2
F2
u6
v3
u12
F1
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v4
z
w
u5
v1
u1
v
u4
u3
u7
u11
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u8
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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 locationbased 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.
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