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Transcript of Presented by Jehn-Ruey Jiang Department of Computer Science and Information Engineering
A Hybrid Power-Saving Protocol byDual-Channel and Dual-Transmission-Range Clustering for IEEE 802.11-Based MANETs
Presented by
Jehn-Ruey JiangDepartment of Computer Science and Information Engineering
National Central University
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To Rest, to Go Far!!
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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IEEE 802.11 Overview
Approved by IEEE in 1997 Extensions approved in 1999 (High Rate) Standard for Wireless Local Area Networ
ks (WLAN)
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WLAN Market
Source: wireless.industrial-networking.com
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IEEE 802.11 Family(1/2)
802.11 (1997) 2 Mbps in the 2.4 GHz band
802.11b (1999) (WiFi, Wireless Fidelity) 5.5 and 11 Mbps in the 2.4 GHz band
802.11a (1999) (WiFi5) 6 to 54 Mbps in the 5 GHz band
802.11g (2001) 54 Mbps in the 2.4 GHz band
802.11n (2005) (MIMO) 108 Mbps in the 2.4 and the 5 GHz bands
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IEEE 802.11 Family(2/2)
802.11c support for 802.11 frames
802.11d new support for 802.11 frames
802.11e QoS enhancement in MAC
802.11f Inter Access Point Protocol
802.11h channel selection and power control
802.11i security enhancement in MAC
802.11j 5 GHz globalization
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Infrastructure vs. Ad-hoc Modes
Infrastructure Network
Ad-Hoc network
APAP
AP Wired Network
Ad-Hoc network
Multi-hop Ad Hoc Network
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Ad Hoc Network (1/3)
A collection of wireless mobile hosts forming a temporary network without the aid of established infrastructure or centralized administration by D. B. Johnson et al.
Also called MANET(Mobile Ad hoc Network) by Internet Society IETF
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Ad Hoc Network (2/3)
Single-Hop Each node is within each other’s transm
ission range Fully connected
Multi-Hop A node reaches another node via a chain
of intermediate nodes Networks may partition and/or merge
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Ad Hoc Network (3/3)
Application Battlefields Disaster Rescue Spontaneous Meetings Outdoor Activities
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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Power Saving Problem
Battery is a limited resource for portable devices
Battery technology does not progress fast enough
Power saving becomes a critical issue in MANETs, in which devices are all supported by batteries
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Solutions to Power Saving Problems
PHY Layer: transmission power control Huang (ICCCN’01), Ramanathan (INFOCOM’0
0) MAC Layer: power mode management
Tseng (INFOCOM’02), Chiasserini (WCNC’00) Network Layer: power-aware routing
Singh (ICMCN’98), Ryu (ICC’00)
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Transmission Power Control
Tuning transmission energy for higher channel reuse
Example: A is sending to B (based on IEEE 802.11) Can (C, D) and (E, F) join?
A
BCD
F E
No!Yes!
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Power Mode Management
Doze mode vs. Active mode Example:
A is sending to B Does C need to stay awake?
A
B
C
No!
It can turn off its radio to save energy!
But it should turn on its radio periodiclally for possible data comm.
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Power-Aware Routing
Routing in an ad hoc network with energy-saving (prolonging network lifetime) in mind
Example:
+
–
+
–
+
–
+
–
+
–
+
–
SRCN1 N2
DEST
N4N3
Better!!
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Our Focus
Among the three solutions: PHY Layer: transmission power control MAC Layer: power mode management Network Layer: power-aware routing
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IEEE 802.11 PS Mode
An IEEE 802.11 Card is allowed to turn off its radio to be in the PS mode to save energyPower Consumption:(ORiNOCO IEEE 802.11b PC Gold Card)
Vcc:5V, Speed:11Mbps
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MAC Layer Power-Saving Protocol
Two types of MAC layer PS protocol for IEEE 802.11-based MANETs Synchronous (IEEE 802.11 PS Protocol)
Synchronous Beacon IntervalsFor sending beacons and ATIM (Ad hoc Traffic Indicat
ion Map) Asynchronous [Tseng et. al. 2002][Jiang et. al. 200
3]Asynchronous Beacon IntervalsFor sending beacons and MTIM (Multi-Hop Traffic Ind
ication Map)
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Beacon:
1.For a device to notify its existence to others
2.For devices to synchronize their clocks
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IEEE 802.11 PS Protocol
Beacon Interval Beacon Interval
Host A
Host B
ATIM Window
ATIM Window
Beacon Frame
Target Beacon Transmission Time(TBTT)
No ATIM means no data to send
or to receive with each other
ATIM Window
Clock Synchronized by TSF (Time Synchronization Function)
ATIM Window
ATIM
ACK
Data Frame
ACK
Active mode
Active modePower saving Mode
Power saving Mode
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IEEE 802.11 PS Protocol (cont.)
Suitable for Single-hop environment Advantages
More power efficiency Low active ratio (less duty cycle)
Drawbacks Clock synchronization for multi-hop
networks is costly and even impossible Network partitioning Not Scalable
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Clock Drift Example
Max. clock drift for IEEE 802.11 TSF (200 DSSS nodes, 11Mbps, aBP=0.1s)
200 s MaximumTolerance
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Network-Partitioning Example
Host A
Host B
A
B
C D
E
F
Host C
Host D
Host E
Host F
╳
╳
ATIM window
╳
╳
Network Partition
The blue ones do not know the existence of the red ones, not to
mention the time when they are awake.
The red ones do not know the existence of the blue ones, not to
mention the time when they are awake.
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Asynchronous PS Protocols (1/2)
Try to solve the network partitioning problem to achieve Neighbor discovery Wakeup prediction
Without synchronizing hosts’ clocks
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Asynchronous PS Protocols (2/2)
Three existent asynchronous PS protocols
Dominating-Awake-Interval
Periodical-Fully-Awake-Interval
Quorum-Based
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What is a quorum?
minimum number of people who must be present at a meeting (of a committee, etc) before it can proceed and its decisions, etc can be considered valid-- Oxford Dictionary
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What is a quorum again?
From Math.quorums:mutually intersecting subsets of a universal set U
E.G.{1, 2}, {2, 3} and {1,3} are quorums under U={1,2,3}
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Numbering Beacon Intervals
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
And they are organized
as a n n array
n consecutive beacon intervals are numbered as 0 to n-1
101514131211109876543210 …
Beacon interval
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Quorum Intervals (1/4)
Intervals from one row and one column are called
Quorum Intervals
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
Example:Quorum intervals arenumbered by2, 6, 8, 9, 10, 11, 14
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Quorum Intervals (2/4)
Intervals from one row and one column are called
Quorum Intervals
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
Example:Quorum intervals arenumbered by0, 1, 2, 3, 5, 9, 13
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Quorum Intervals (3/4)
Any two sets of quorum intervals have two common members
For example:The set of quorum intervals {0, 1, 2, 3, 5, 9, 13} and the set of quorum intervals{2, 6, 8, 9, 10, 11, 14} have two common members:
2 and 915141312
111098
7654
3210
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Quorum Intervals (4/4)
1514131211109876543210
2 151413121110987654310
2 overlapping quorum intervals
Host DHost C
2 151413121110987654310Host D
1514131211109876543210Host C
Even when the beacon interval numbers are not aligned (they are rotated), there are always at least two overlapping quorum intervals
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Structure of Quorum Intervals
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Networks Merge Properly
Host A
Host B
A
B
C D
E
F
Host C
Host D
Host E
Host F
ATIM window
Beacon window
Monitor window
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Quorum Systems Help with the Proof
What is a quorum system?A collection of mutually intersecting subsets of an universal set U, where each subset is called a quorum.E.G. {{1, 2},{2, 3},{1,3}} is a quorum system under U={1,2,3}, where {1, 2}, {2, 3} and {1,3} are quorums.
Not all quorum systems are applicable to QAPS
Only those quorum systems with the rotation closure property are applicable.
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Optimal Quorum System (1/2)
Quorum Size Lower Bound for quorum systems satisfying the rotation closure property:k, where k(k-1)+1=n, the cardinality of the universal set, and k-1 is a prime power(k n )
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Optimal Quorum System (2/2)
Optimal quorum system FPP quorum system
Near optimal quorum systems Grid quorum system Torus quorum system Cyclic (difference set) quorum system E-Torus quorum system
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QAPS: Quorum-based Asynchronous Power Saving Protocols
Advantages Do not need synchronized clocks Suitable for multi-hop MANETs Asynchronous neighbor discovery and wa
keup predictionDrawbacks
Higher active ratio than the synchronous PS protocol
Not suitable for high host density environment
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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HPS Overview
A Hybrid PS protocol Synchronous – IEEE 802.11 PS protocol Asynchronous – QAPS
Forming clustering networks Utilizing the concepts of dual-channel an
d dual-transmission-range Taking advantages of two types of PS pro
tocols To reduce the active ratio Suitable for multi-hop MANETs
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Cluster Forming
0
100
200
300
400
500
600
700
800
900
1000
0 100 200 300 400 500 600 700 800 900 1000
Simulation area (X-axis)
Sim
ulat
ion
area
(Y
-axi
s)Cluster Head Cluster Member
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Dual transmission ranges
Cluster head uses Range RA for inter-cluster transmission Range RB for intra-cluster transmission
E
FRA
RB
E, F: cluster heads
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Dual channels
Two non-interfering comm. channels are used Channel A for inter-cluster transmission Channel B for Intra-cluster transmission
E F
RA
RB
E, F: cluster heads
Channel AChannel B
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Two types of beacon frames
Intra-cluster beacon Send in channel B with transmission range RB
For cluster forming For clock synchronization
Inter-cluster beacon Send in channel A with transmission range RA
For neighboring cluster heads discovery For wakeup prediction
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Practical Considerations
Dual transmission ranges Practical for IEEE 802.11 Standard More power efficiency
Dual channels Practical for IEEE 802.11 Standard Non-interfering channels (such as 1, 6, 11) Inter-cluster and Intra-cluster comm. can
take place simultaneously
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Clustering
Who is Boss? If somebody near me says that he/she is
Boss, then I am his/her employee.
If nobody is Boss, then I am Boss.
Boss should keep whistling periodically to summon employees. He/She should relay messages for employees and thus spend more energy.
An employee just keep watching if Boss is there.
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State Transition
Listening State
Cluster Member State Cluster Head State
Do not receive intra-cluster beacon in channel B over ( q+1 beacon intervals + a random backoff time)
A host enters the network initially
Receive an intra-cluster beacon in channel B from the cluster head
Do not receive intra-cluster beacon in channel B from cluster head over q+1 beacon intervals Broadcast intra-
cluster beacon every non-quorum interval
Receive an intra-cluster beacon in channel B during (q+1 beacon intervals + a random backoff time)
Dismissal mechanism is invoked
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x yRB
RA v.s. RB
One extreme case for infinite host density:
RA = RB+
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x yRB RB
RA v.s. RB
One extreme case for infinite host density:
RA = 2RB-
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x yRB RB
RB
z
RA v.s. RB
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Structure of Beacon Intervals
B M B M B’ M’
Active period
Active period in channel A
quorum Interval non-quorum Interval
B
B’ M’
Cluster Head
Cluster members
M
B’ M’
: Beacon window and MTIM window in channel A
: Beacon window and MTIM window in channel B
: Monitor mode in channel A
: PS mode
Active period in channel B
quorum Interval non-quorum Interval
Active period in channel B
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Dismissal Mechanism (1/2)
To keep the fraction of cluster heads ASAP when network topology changes
To balance the load of cluster heads But how?
: Cluster heads
High priority
Dismissal (back to listening state)
Low priority
Dismissal Mechanism is invoked
To detect if hosts are moving too close.
To take service time and residual engergy into consideration.
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Distance Default Dismissal Range = 1/5 RB
By RSSI estimation Priority (exchanged in inter-cluster
beacons) Cluster head service time
Short service time Low priority Remaining battery energy
High remaining battery energy Low priority
Cluster head IDSmall cluster head ID Low priority
Dismissal Mechanism (2/2)
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Cluster Forming (1/2)
0
100
200
300
400
500
600
700
800
900
1000
0 100 200 300 400 500 600 700 800 900 1000
Simulation area (X-axis)
Sim
ulat
ion
area
(Y-a
xis)
Cluster Head Cluster Member
100 hosts
33 cluster heads
67 cluster members
RB
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Cluster Forming (2/2)
0
100
200
300
400
500
600
700
800
900
1000
0 100 200 300 400 500 600 700 800 900 1000
Simulation area (X-axis)
Sim
ulat
ion
area
(Y
-axi
s)Cluster Head Cluster Member
500 hosts
45 cluster heads
455 cluster members
RB
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Routing (1/5)
Based on AODV RREQ (Route request) ONLY rebroadcast by
cluster heads Intra-RREQ : within a cluster using channel B Inter-RREQ : between cluster heads using channe
l A RREP (Route reply)
Intra-RREP : within a cluster using channel B Inter-RREP : between cluster heads using channel
A
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1. If the source host is a member, it undergoes MTIM-ACK-RREQ-RREQ message exchange with the cluster head using channel B with transmission range RB.
2. If the cluster head receives no RREP in the same beacon interval, it will rebroadcast the RREQ to all its neighboring cluster heads using channel A with transmission range RA.
3. If a host originates or receives a RREP, it will remains in active mode in channel A. This is prepared for the upcoming data transmission.
Routing (2/5)
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Routing (3/5)
Non-Quorum Interval
RREQ
ATIM Window
ATIM Window
ATIM
ACK
Active mode
Active mode
Cluster member
X
Cluster head
ATIM Window
Active mode
Cluster member
Y
RREP
RREQ
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MTIMRREQ
Routing (4/5)
RB
Cluster member
Cluster head A
Cluster head C
Cluster head B
RA
ACK
RREQ
RREQ
X
Y
RREP
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Routing (5/5)
0
100
200
300
400
500
600
700
800
900
1000
0 100 200 300 400 500 600 700 800 900 1000
Simulation area (X-axis)
Sim
ulat
ion
area
(Y
-axi
s)
Cluster Head Cluster Member
Source
Destination
RB = Intra-cluster broadcast
RA = Inter-cluster broadcast
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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Simulation Results
Parameters Area size : 1000mx1000m RA : 250m RB : 125m Mobility : 0~10m/sec with pause time 20 secon
ds Traffic load : 1~4 routes/sec Number of hosts : 100~1000 hosts
Performance metrics Cluster head ratio Survival ratio Throughput
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Cluster Head Ratio
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800 900 1000
Number of hosts
Rat
io o
f cl
ust
er h
ead
s (%
) Speed=0
Speed=5
Speed=10
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Survival Ratio
0
20
40
60
80
100
120
100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440
Simulation time (sec)
Surv
ival
rati
o (%
)
HPS, 100 hosts, speed=10
HPS, 200 hosts, speed=10
E-Torus(4x8), 100 hosts, speed=10
E-Torus(4x8), 200 hosts, speed=10
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Throughput Comparison with QAPS
0100020003000400050006000700080009000
10000110001200013000140001500016000
0 5 10
Moving speed (m/sec)
Thr
ough
put x
Lif
etim
e (K
B)
0
5
10
15
20
25
30
35
Thr
ough
put (
KB
/sec
)
AA, Th x Life HPS, Th x LifeE-Torus(4x8), Th x Life AA, ThHPS, Th E-Torus(4x8), Th
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Outline
IEEE 802.11 MANETs Power Saving Problem Hybrid Power Saving Protocols Simulation Results Conclusion
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Conclusion (1/2)
Taking advantages of both the sync. and async. PS protocol, and utilizing the concepts of dual-channel and dual-transmission-range To save more energy To accommodate more hosts Without clock synchronization No network partitioning
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Conclusion (2/2)
Adopting cluster-based routing to reduce the number of routing request rebroadcasts dramatically
Using dismissal mechanism to void the ever-increasing of cluster he
ads to make the protocol adaptive to topolo
gy changingPractical for IEEE 802.11-based MANE
Ts
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References:
1. Yu-Chee Tseng, Chih-Shun Hsu and Ten-Yueng Hsieh, “Power-Saving Protocols for IEEE 802.11-Based Multi-Hop Ad Hoc Networks,” InfoCom’2002, 2002
2. Jehn-Ruey Jiang, Yu-Chee Tseng, Chih-Shun Hsu and Ten-Hwang Lai, “Quorum-based asynchronous power-saving protocols for IEEE 802.11 ad hoc networks,” ACM Journal on Mobile Networks and Applications, Feb. 2005. (ICPP 2003 Best Paper Award)
3. Jehn-Ruey Jiang, Chau-Yuan Yang, Ting-Yao Chiou and Shing-Tsaan Huang, "A Hybrid Power-Saving Protocol by Dual-Channel and Dual-Transmission-Range Clustering for IEEE 802.11-Based MANETs," International Journal of Pervasive Computing and Communications, to appear.
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Q&A
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The States (1/3)
Listening State Listen in channel B for intra-cluster beacons for
a period of (q+1 beacon intervals plus a random back-off time)
0-15 time slots with each time slot occu
pying 20 μs
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The States (2/3)
Cluster Head state Running async PS protocol
for inter-cluster comm. Running sync PS protocol
for inter-cluster comm.
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The States (3/3)
Cluster Member State Synchronizing its clock with the cluster
head’s Running sync PS protocol Adopting cluster head’s quorum information
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Rotation Closure Property (1/3)
Definition. Given a non-negative integer i and a quorum H in a quorum system Q under U = {0,…, n1}, we define rotate(H, i) = {j+ijH} (mod n).
E.G. Let H={0,3} be a subset of U={0,…,3}. We have rotate(H, 0)={0, 3}, rotate(H, 1)={1,0}, rotate(H, 2)={2, 1}, rotate(H, 3)={3, 2}
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Rotation Closure Property (2/3)
Definition. A quorum system Q under U = {0,…, n1} is said to have the rotation closure property ifG,H Q, i {0,…, n1}: G rotate(H, i) .
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Rotation Closure Property (3/3)
For example, Q1={{0,1},{0,2},{1,2}} under
U={0,1,2}} Q2={{0,1},{0,2},{0,3},{1,2,3}}
under U={0,1,2,3}
Because {0,1} rotate({0,3},3) = {0,1} {3, 2} =
Closure
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Examples of quorum systems
Majority quorum system Tree quorum system Hierarchical quorum system Cohorts quorum system ………
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FPP quorum system
Proposed by Maekawa in 1985 For solving distributed mutual exclusion Constructed with a hypergraph
An edge can connect more than 2 vertices FPP:Finite Projective Plane
A hypergraph with each pair of edges having exactly one common vertex
Also a Singer difference set quorum system
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FPP quorum system Example
0 1 2
3 4
5
6
A FPP quorum system:{ {0,1,2}, {1,5,6}, {2,3,6}, {0,4,6}, {1,3,4}, {2,4,5}, {0,3,5} }
0
3
5
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Torus quorum system
For a tw torus, a quorum contains all elements from some column c, plus w/2 elements, each of which comes from column c+i, i=1.. w/2
171615141312
11109876
543210
One full column
One half column cover in a wrap around manner
{ {1,7,13,8,3,10}, {5,11,17,12,1,14},…}
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Cyclic (difference set) quorum system
Def: A subset D={d1,…,dk} of Zn is called a difference set if for every e0 (mod n), thereexist elements di and djD such that di-dj=e.
{0,1,2,4} is a difference set under Z8
{ {0, 1, 2, 4}, {1, 2, 3, 5}, {2, 3, 4, 6}, {3, 4, 5, 7},{4, 5, 6, 0}, {5, 6, 7, 1}, {6, 7, 0, 2}, {7, 0, 1, 3} }is a cyclic (difference set) quorum system C(8)
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E-Torus quorum system
Trunk
Branch
Branch
Branch
Branch
cyclic
cyclic
E(t x w, k)