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FAR: Face-Aware Routing for Mobicast in Large-Scale Sensor Networks
QINGFENG HUANGPalo Alto Research Center (PARC) Inc.andSANGEETA BHATTACHARYA, CHENYANG LU, and GRUIA-CATALIN ROMANWashington University in St. Louis
ACM Transactions on Sensor Networks (TOSN), November 2005ACM Transactions on Sensor Networks (TOSN), November 2005
Chien-Ku Lai
Outline
IntroductionMobicast OverviewFace-Aware Routing for MobicastTopology DiscoverySimulation ResultsConclusion
Introduction
Wireless Sensor NetworksMobicast
Introduction- Wireless Sensor Networks
Wireless sensor networks : are large-scale distributed embedded systems com
posed of small devices sensors wireless communication interfaces microprocessors maybe some actuators
will soon be feasible to deploy dense collections of sensors to perform distributed micro-sensing of physical environments
Introduction- Wireless Sensor Networks (cont.)
Many sensor network applications have fundamental spatiotemporal constraints
an intruder tracking application example an information scouting example
Introduction- Mobicast
Mobicast represents a new information dissemination
paradigm with spatiotemporal semanticsallow applications to specify their spatiotem
poral constraints by requesting a mobile delivery zone
in turn enables the application to build a continuously changing group configuration
Introduction- Mobicast (cont.)
ChallengeHole
Introduction
This article presents :a new Face-Aware Routing protocol (FAR) f
or mobicasta related spatial neighborhood discovery alg
orithm
Mobicast Overview
Limitation of Approaches Based on GeocastAdvantages of Just-in-Time Delivery
About Mobicast
The mobicast service supports a type of application information delivery request right-place and right-time just-in-time
Limitation of Approaches Based on Geocast
Duplicate area
Advantages of Just-in-Time Delivery
Face-Aware Routing for Mobicast
The Planar Spatial NeighborhoodFace-Aware Routing
About face routing
The idea of face routing is inspired by previous geometric routing algorithmsCompass routingFACE-2GPSRGOAFR+
Faces
The Planar Spatial Neighborhood
A
Face
D Spatial neighborE
C
BP
F
The Planar Spatial Neighborhood
G
Face
Spatial neighbor
C
BP
F
L
N
HI
J
K
M
The Planar Spatial Neighborhood
M
Face
D Spatial neighborE
CF
L
N
G O
HI
J
K
Face-Aware Routing
The face-aware algorithm consists of two methods for forwarding packets:greedy forwarding timed forwarding
About FAR
Packet Format
Greedy Forwarding
Timed Forwarding
Protocol Termination
Packet Format
Packet header
1 2 3 4 5 6 7 8
Sender location
Packet sending time-stamp
Initial delivery zone coordinates
Delivery zone velocity
Message lifetime
Message type
Sender packet sequence number
The last forwarder location
• identify each packet on the network
Greedy Forwarding
Greedy forwarding applies to all nodes that are currently (or previously) covered by the mobica
st delivery zone or have at least one spatial neighbor that is currentl
y (or previously) covered by the mobicast delivery zone
In such cases, a node forwards a new packet in an “as-soon-as possible” fashion
Timed Forwarding
Timed forwarding applies to a node that has no spatial neighbor in the current delive
ry zonebut either itself will soon be in the delivery zone or has at least one spatial neighbor that will be in
the delivery zone
Example
G
L
M
E
FI
HP
C
BA
J
D
NK
P G
L
M
EN
F
AA
JC
B
D
K
Greedy forwarding mode
Timed forwarding mode
Timed Forwarding (cont.)
the expected 1-hop network latency
the hop distance
The forwarding decision of X is as follows:(1) If Ta ≤ 0 forward the packet as soon as possible(2) If Ta > 0 delay the forwarding for time length Ta
Protocol Termination
A packet is not simply ignored if it has expired
An expired packet is dropped only in the timed forwarding mode
If a node is in greedy forwarding mode it will forward the packet even if the packet h
as expired
FAR assumption
The perpendicular span to be no smaller than the maximum communication range
Topology Discovery
Face IdentificationFace Traversal TerminationCost MinimizationThe Outer Face
Topology Discovery
Face Identification
How to make each discovery message traverse the correct face ?using a ring-buffer on each node for storing
the incident planar edges
A
B C
DA’s ring-buffer:
A-B
A-C
A-D
Face Traversal Termination
How to determine when a message has traversed the whole face ?A node determines if an incoming discovery
message dm has completed a full traversal of a face by the following criterion :
the outgoing edge for dm is contained in its ordered traversal list
“when the message comes back to a node already traversed” does not work
Face Traversal Termination
Example
G
Cost Minimization
How to coordinate between nodes such that only one discovery message flows around each face ?On each face, ideally one traversing discove
ry message will suffice
Cost Minimization (cont.)
Two strategies for reducing the number of discovery messagesRandom starting timeStarting location-based tiebreaking rule
east is preferred, if there is still a tie, north is preferred
The Outer Face
A practical way to identify an “outer” face is from its sizea discovery message has a max hop count
Simulation Results
Spatial ReliabilityTemporal Characteristics
Simulation environment
600 sensors1000 × 400 m2 areadispersed randomly under the uniform di
stribution120 × 100 m2 rectangular delivery zoneNS2 network simulatorIEEE 802.11 MAC protocol
Spatial Reliability
Average and Standard Deviation of Delivery Ratio of FAR, Greedy and Geocast
Temporal Characteristics- Slacktime
Temporal Characteristics- Slacktime (cont.)
Temporal Characteristics- Slacktime (cont.)
Conclusion
FARSpatial neighborhood discovery protocol
Conclusion- FAR
FARa new face aware mobicast routing protocol
which, in theory, reliably delivers messages spatially
has good mobicast temporal characteristics relies on the notion of spatial neighborhoods features a novel timed face aware forwardin
g method
Conclusion- Spatial neighborhood discovery protocol
This paper addressed key issues a spatial neighborhood discovery protocol must consider face identificationdiscovery terminationduplicate elimination
Question?
Thank you.Thank you.