Title: Spatiotemporal Multicast in Sensor Networks Qingfeng Huang, Chenyang Lu and GruiaCatalin Roman Washi
1Spatiotemporal Multicast in Sensor
NetworksQingfeng Huang, Chenyang Lu and
Gruia-Catalin RomanWashington UniversitySenSys
'03
- presented by Hyun Bin Lee
- 2004.11.30.
2Contents
- Introduction
- Related Work
- Geocast
- Motivation
- Design Mobicast
- Parameter Analysis
- Discussion
3Introduction
- 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
4Related 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
5Geocast 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
6Motivation
- Reduce the slack time
- Reduce the retransmission overhead
- Reliable delivery
7Simple 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
8Problem 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.
9Mobicast Framework
Delivery Zone
Future Delivery Zone
Forwarding Zone
Hold Forward Zone
Headway Distance
10Mobicast 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
11Undetermined Parameters
- What is the size and shape of forwarding zone?
- What is the headway distance?
12?-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
13Delivery 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.
14Example
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
5
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
15G-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
16Headway 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
17Summary 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
18Conclusions
- Propose a new and interesting application
- Multicast in ad-hoc network
- Analyze the upper bound of parameters for
reliable delivery