Spatiotemporal Multicast in Sensor Networks Qingfeng Huang, Chenyang Lu and GruiaCatalin Roman Washi

1
Spatiotemporal Multicast in Sensor
NetworksQingfeng Huang, Chenyang Lu and
Gruia-Catalin RomanWashington UniversitySenSys
'03

• presented by Hyun Bin Lee
• 2004.11.30.

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Contents

• Introduction
• Related Work
• Geocast
• Motivation
• Design Mobicast
• Parameter Analysis
• Discussion

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Introduction

• Unicast
• One-to-one communication
• Telnet, FTP, VOD
• Restricted number of users
• Broadcast
• One-to-all communication
• Overload network PC resource
• Multicast
• One-to-many communication
• IP multicast

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Related Work Geocast

• For mobile ad hoc network
• Geocast region a specified geographical area
• The location information of all the nodes known
  by GPS
• Deliver packets to a group of nodes in geocast
  Region
• Whenever one node in geocast region receives
  message from outside, it will flood it to all its
  neighbors

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Geocast Problem
geocast
re-geocast

• Rectangle A-C Initial geocast area
• B The point of re-issuing request
• L The length of the geocast area
• W The distance betwaeen B and C
• Va The speed of soldier
• Vp The speed of maximum message
• propagation speed

L-W
The number of extra radio transmission per
delivery Mw W / (L-W) The average slack time
Ts (S/Va S/Vp)/2 (L-W)(1/Va
1/Vp)/2 Geocast has fundamental conflict in this
application
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Motivation

• Reduce the slack time
• Reduce the retransmission overhead
• Reliable delivery

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Simple Mobicast
In current delivery zone
Will be in delivery zone soon
Other nodes

• Hold-and-forward strategy
• In current delivery zone deliver and forward
• Will be in delivery zone soon hold and forward
  at the time the delivery zone reaches the node
• Other cases Ignore the message
• Has minimal delivery overhead good slack time
  characteristics
• Not reliable

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Problem of Simple Mobicast
Hole
Delivery zone
There is a hole between X and other nodes in the
delivery zone. The protocol fails to deliver the
mobicast message to node X
To deliver reliably, some nodes that are not in
the delivery zone have to participate in message
forwarding.
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Mobicast Framework
Delivery Zone
Future Delivery Zone
Forwarding Zone
Hold Forward Zone
Headway Distance
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Mobicast Framework

• Two phases
• Initialization phase
• Cruising phase
• Just-in-time
• In forwarding zone forward message immediately
• Will be in forwarding zone hold and forward at
  the time becoming member of the forwarding zone
• Other cases ignore the message

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Undetermined Parameters

• What is the size and shape of forwarding zone?
• What is the headway distance?

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?-Compactness
M(A, B)
ACB, 2 hops
d(A, B)
G(V, E) geometric graph d(i, j)
Euclidean distance between node i and j M(i, j)
Set of shortest hop network paths between node i
and j d(i, j) The minimum Euclidean length of
all paths in M(i, j), also called S2 distance
d(A, B)
ADEB, 3 hops
?-compactness of two nodes d(i, j) d(i, j) /
d (i, j) ?-compactness of network d MINi,j
d(i, j) ?-dilation The inverse of ?-compactness
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Delivery Guarantee
b
c
Foci
a

• Math Concepts
• x2/a2y2/b2 1
• c sqrt(a2-b2)
• Eccentricity e c/a
• Delivery Guarantee
• The ellipse that has A and B as its foci and with
  eccentricity e (network ?-compactness value)
  contains a shortest network path inside it.

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Example
d(A,B)10/15
d(A,D)8/10
d(B,C)6/10
d(A,C)5/5
d(C,D)5/5
d(D,B)5/5
?-compactness d MINi,jd(i, j) / d (i, j) For
any two nodes A and B in the network, there must
exist a shortest network path that is inside the
ellipse which has A and B as its foci with
eccentricity d
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6
5
5
8
10
d(A, B)10, d(A, D)8, d(B, C)6, d(A, C)d(C,
D) d(D, B)5
d MIN (10/15, 8/10, 6/10, 5/5, 5/5, 5/5) 0.6
For A, B. c 10/2 5, c/a e 0.6, so
a25/3, b20/3
x2/(25/3)2 y2/(20/3)2 1
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G-Compactness
?(A,B)10/3
?(A,D)8/2
?(B,C)6/2
?(A,C)5/1
?(C,D)5/1
?(D,B)5/1
h(i, j) The minimum number of network hops
between nodes i and j d(i, j) The Euclidean
distance between node i and j G-Compactness ?
min d(i, j) / h(i, j)
5
6
5
5
8
10

• If a networks G-compactness value is ?, then
  any two nodes in the network separated by a
  distance d must have a shortest path no greater
  than d/? hops

d(A, B)10, d(A, D)8, d(B, C)6, d(A, C)d(C,
D) d(D, B)5
? MIN (10/3, 8/2, 6/2, 5/1, 5/1, 5/1) 3
A, B has path no more than d/? 10/3 3.3 hops
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Headway Distance
V
v
Diagonal length Sd
Headway Distance d

• Result
• ds v?1Sd/?
• Discussion
• The longer transmission delay, the longer
  headway distance
• The larger delivery zone size, the longer
  headway distance
• The faster moving speed, the longer headway
  distance
• The smaller G-Compactness, the longer headway
  distance

• Definition
• ?1 the max one-hop latency of the network
• Sd the diagonal length of a delivery zone
• v the traveling speed
• ? G-Compactness value. ? min d(i, j) / h(i, j)
• ds headway distance

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Summary of Parameter Analysis

• Based on known network topology, we can compute
  the upper bound of forwarding zone and headway
  distance to ensure reliable delivery
• The forwarding zone is k-cover of the delivery
  zone
• The headway distance is also computable

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Conclusions

• Propose a new and interesting application
• Multicast in ad-hoc network
• Analyze the upper bound of parameters for
  reliable delivery