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An Energy Efficient, Load Balanced Multicast Protocol with Probabilistic Anycast for ZigBee Wireless Sensor Networks
Advisor : Prof. Yu-Chee TsengStudent : Yi-Chen Lu
2009/6/26
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Introduction
A WSN is composed of numerous inexpensive wireless sensor nodes, each of which is normally powered by batteries and has limited computing ability
Wireless sensor nodes are capable of not only collecting, storing, processing environmental information, but also communicating with neighboring nodes
Many research works have been dedicated to WSNs, such as routing, self-organization, deployment, and localization
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Introduction
Multicast is a fundamental routing service of network communication
In WSN, a single message can be delivered to multiple destinations efficiently via multicast communication
In WSN, members may dynamically join and leave the groups
Fruits Area
Drinks Area
Join banana group
Join coke group
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Introduction
ZigBee is a cost-effective wireless networking solution that supports low data-rates, low-power consumption, security, and reliability
Most WSN industries have adopted ZigBee as their communication protocol and developed numerous products
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ZigBee Multicast
In ZigBee, multicast members are physically separated by a hop distance of no more than MaxNonMemberRadius
ZigBee multicast exploits regional flooding to deliver the multicast message
Region bounded by MaxNonMemberRadius
Member Another Member
Drawbacks of ZigBee multicast Heavy traffic
overhead High energy cost Unreliable
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Outline
IntroductionRelated Work
Overlay Multicast Geographic Multicast Relay-Selection Multicast
MotivationGoalProtocol DesignSimulationConclusion
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Overlay Multicast
PAST-DM (Wireless Networks 2007) Applying unicast leads to excessive
energy consumption and redundant transmissions
AOM (ICPPW 2007) Applying broadcast eliminates
redundant transmissions Packet header overhead
Overlay multicast needs extra cost to support dynamic member actions
Fixed delivery paths lead to single-node failure problem
redundant
Destination List & Forwarder List
6 transmissions
4 transmissions
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Geographic Multicast
GMREE (COMCOM 2007) Cost over progress ratio
Drawbacks Packet header overhead Location information must be available Suffer from the face routing cost Do not support dynamic member
joining/leaving Single-node failure problem
S SS
S
S
S
S
S
S
S
S
S
S
S
SS
S
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Relay-Selection Multicast Steiner-tree based multicast
BIP and MIP (MONET 2002)▪ Based on Prim’s algorithm to find
a minimum-cost spanning tree
NJT and TJT (COMCOM 2007 ) ▪ Minimum cost set cover heuristics
Single-node failure problem Computing complexity is high Centralized algorithm must keep global
information Do not support dynamic member joining/leaving Source tree construction overhead
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109
1
3
2
8
7
6
5
S
1 2 3 4 5 6 7
C1 C2 C3 C4 C5
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Motivation
Due to the limited power resource, energy efficient multicast is a critical issue in WSN
ZigBee multicast is not only energy inefficient but also unreliable
Many approaches have been proposed to study on the energy efficient multicast issues in WSN
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Motivation
However, these proposed approaches either have significant drawbacks or are not compatible with ZigBee Single-node failure problem (all) Do not support dynamic member joining/leaving
(all) Packet header overhead (overlay & geographic) Location information (geographic) High computing complexity (geographic & relay) Must keep global information (relay-selection)
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Goal
Propose a multicast routing protocol which has the following features ZigBee Compatible Energy efficient▪ Less energy consumption
Reliable▪ Higher delivery ratio
Load balanced▪ Avoid single-node failure problem▪ Prolong the network lifetime
Support dynamic member joining/leaving
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
Protocol Overview
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S
S
S
S
S
S
SS
S
Probabilistic
Anycast
Random Backoff
Packet Forwardin
g
Coverage Over Cost Ratio
Residual Energy
Forwarding Strategy
Ack Mechanism
Multicast Informatio
n Table (MIT)
S
S
S
S
S
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Protocol Flow
MIT Maitenance
Radom Backoff
Discard
Forward
Rebroadcast
Ack Mechanis
m
Forwarding Strategy
Initiate A Multicast
Receive A Multicast Packet
Coverage Over Cost Ratio
Residual Energy
Wait for twait
Backoff for tb
Multicasting
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Outline
Introduction Related Work Motivation Goal Protocol Design
MIT Maintenance Multicasting
Simulation Conclusion
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Outline
Introduction Related Work Motivation Goal Protocol Design
MIT Maintenance Multicasting
Simulation Conclusion
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MIT Maintenance
Multicast Information Table (MIT) Reachable members within
MaxNonMemberRadius hops Hop distances to the reachable members
MIT
Member Hop Count
m1 h1
m2 h2
… …
mn hn
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MIT Maintenance Example
1 10
6
5
4
3
7
11
2 8
9
18
19
15
13
12 21
20
17
16
14
23
22
24
25
HELLO
1 10
6
5
4
3
7
11
2 8
9
18
19
15
13
12 21
20
17
16
14
23
22
24
25
1 10
6
5
4
3
7
11
2 8
9
18
19
15
13
12 21
20
17
16
14
23
22
24
25
MIT 11
15 1MIT 14
15 1
MIT 10
15 1
MIT 12
15 1
MIT 18
15 1HELLO
MIT 25
15 2
MIT 20
15 2
MIT 21
15 2
MIT 17
15 2
MIT 16
15 2
MIT 3
15 2
MIT 9
15 2
MIT 13
15 2
Region bounded by MaxNonMemberRadius = 2
1 10
6
5
4
3
7
11
2 8
9
18
19
15
13
12 21
20
17
16
14
23
22
24
25
MIT 1
15 3
MIT 2
15 3
MIT 4
15 3
MIT 6
15 3
MIT 8
15 3MIT 19
15
3
MIT 22
15 3
MIT 23
15 3
MIT 24
15 3
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
HELLO
MIT Maintenance Example
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1
5
8
15
21
MIT 21
15 2
MIT 1
5 2
8 2
15 3
MIT 5
1 2
8 3
MIT 8
1 2
5 3
15 3
MIT 15
1 3
8 3
21 2
MaxNonMemberRadius = 2
MIT keeps the information of only the members located within the region bounded by MaxNonMemberRadius hops
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Outline
Introduction Related Work Motivation Goal Protocol Design
MIT Maintenance Multicasting
Simulation Conclusion
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Protocol Flow
MIT Maitenance
Radom Backoff
Discard
Forward
Rebroadcast
Ack Mechanis
m
Forwarding Strategy
Initiate A Multicast
Receive A Multicast Packet
Coverage Over Cost Ratio
Residual Energy
Wait for twait
Backoff for tb
Multicasting
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Multicasting
Our protocol adopts a probabilistic anycast mechanism based on the coverage over cost ratio and each node’s residual energy
Our protocol is similar to the relay-selection approaches
However, the selection of relay nodes is determined by the receivers, rather than by the senders
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Probabilistic Anycast
Random Back-off
Packet Forwarding
Probabilistic Anycast
•Coverage Over Cost Ratio• Residual Energy
•Forwarding Strategy•Ack Mechanism
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Probabilistic Anycast Illustration
S
S
Node S multicasts a message
Node S’s neighbors, A, B, and C receive the message
Node A, B, and C back off for an interval which is calculated according to The coverage over
cost ratio Its own residual
energy
When the backoff timer expires The node forwards
the message if its destination set is not empty
The node does not forward the message if its destination set is empty
B covers all my
reachable members
{Y}
As the network topology changes and the power of each node depletes, the set of forwarders will be different
Therefore, our protocol is able to achieve energy efficiency and load balance while avoiding single-node failure problem
After sending out the message, node S waits
for a period of time twait to
confirm the forwarding status
Node S decides whether to retransmit the packet according to whether the forwarders cover all the destination members or not
To X, Y, ZTo X, Y
To Z
No retransmission because A, B, and C have covered X,Y,
and Z
Candidate Relay
Candidate Relay
Candidate Relay
C
B
A
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Initiating A Multicast
Packet
M H
m1 2
m2 2
m3 3
Eavg
S
Multicast to {m1, m2, m3} ; the hop distance
to them is {2, 2, 3 }
Destination Set M = {m1, m2, m3}Distance Set H = {2, 2, 3 }
The average residual energy of my neighbors
is Eavg
Average residual energy of the neighbors = Eavg
MIT
m1 2
m2 2
m3 3
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Upon Receipt of A Multicast Packet
Packet
M H
m1 2
m2 2
m3 3
Eavg(S)
S
MIT
S 1
m2 3
m3 2
S XPacke
t
M H
m3 2
Eavg(X)
Sm2
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Roger that!
Remove member originator/previous hop to avoid loop
Remove the members which are further
from me than from the previous hop to
avoid detours
MIT
m1 2
m2 2
m3 3
Packet
M H
m3 2
Eavg(X)
Generate a random backoff period
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Random Backoff
Random Back-off
Packet Forwarding
Probabilistic Anycast
•Coverage Over Cost Ratio• Residual Energy
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Coverage Over Cost Ratio Coverage Over Cost Ratio
The coverage over cost ratio is targeted at reaching as many member nodes as possible while consuming as little energy as possible
ontransmissibroadcast single one ofcost energy the:
MIT theofentry each in counts hop of sum the: TL
MIT in the members reachable ofnumber the: D
(1) 1DTL
D
tx
tx
E
Ef
X
A
B
Y C
B
A
Number of covered
members
Estimated energy cost Superior
in forwardin
g
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Radom Backoff
The backoff timer interval tb is generated randomly within the range [0, T]
With greater f value, T should be smaller The single-node failure problem is still
unsolved
erRadiusMaxNonMembEf
E
Nf
ff
ff
TT
tx
tx
max
1
)1(
min
max
minmax
min
max
Normalize f to a parameter α to show the influence of coverage over cost ratio on the backoff interval
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Random Backoff
We further introduce the idea of load balance to our protocol
Therefore, a node which has more energy and covers more destination members with less energy cost has a better chance to generate a shorter backoff interval
The data delivery paths are dynamically adjusted during each propagation according to the instant network condition
(2) )1( maxr
avg
E
ETT S
S
S
S
Superior in
forwarding
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Packet Forwarding
Random Back-off
Packet Forwarding
Probabilistic Anycast
•Forwarding Strategy•Ack Mechanism
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Packet Forwarding
Packet
M H
Eavg(S)
S
MIT
m1 2
m2 2
m3 3
X
Y
Z
MIT
S 1
m2 3
m3 2
MIT
S 1
m1 1
m2 1
MIT
S 1
m1 1
Packet
M H
m3 2
Eavg(X)
Packet
M H
m1 1
m2 1
Eavg(Y)Packet
M H
Eavg(Z)
Roger that!
Roger that!
Roger that!
twait
Generate a random backoff period
Generate a random backoff period
Generate a random backoff period
Wait for a period of time twait
m1 1
m3
m1
m2
3
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m1 is covered by node Y
m1 and m2 are
forwarded by node Y
m3 is forwarded by
node X
The members I want to
forward to are all covered by other nodes
All the destination
members are forwarded
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Simulation
Simulation Environment
Simulation Duration 105 sec
Area 35m * 35m
Number of Nodes 100~500 (Random deployment)
Number of Members 10 (Randomly generated)
MaxNonMemberRadius 5
Transmission Range 6m
MAC IEEE 802.15.4 MAC with unslotted CSMA-CA
Max Backoff Interval 5ms
Transmission Rate 250Kbps
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Simulation
100 200 300 400 5000
5
10
15
20
25
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ZigBee Proposed protocol
Network size
Late
ncy (
ms)
100 200 300 400 5000
100
200
300
400
500
600
700
800
900
1000
ZigBee Proposed protocol
Network Size
Nu
mb
er
of
packets
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Outline
Introduction Related Work Motivation Goal Protocol Design Simulation Conclusion
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Conclusion
Energy efficient multicast is a critical issue in WSN Many approaches have been proposed, but they fail
to achieve energy efficiency and load balance at the same time
We propose a ZigBee compatible multicast protocol Energy efficient Load balanced Reliable Support dynamic member joining/leaving
Simulation result shows that our protocol outperforms ZigBee in energy consumption and latency
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Q&A
Thanks