asynchronous power-saving protocols via quorum systems for ieee 802.11 ad hoc networks
DESCRIPTION
Asynchronous Power-Saving Protocols via Quorum Systems for IEEE 802.11 Ad Hoc Networks. Jehn-Ruey Jiang Hsuan-Chuang University. To Rest, to Go Far!. Outline. IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation - PowerPoint PPT PresentationTRANSCRIPT
Asynchronous Power-Saving Protocols via Quorum Systems for
IEEE 802.11 Ad Hoc Networks
Jehn-Ruey Jiang
Hsuan-Chuang University
To Rest, to Go Far!
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
IEEE 802.11
Approved by IEEE in 1997
Extensions approved in 1999
Standard for Wireless Local Area Networks ( WLAN )
IEEE 802.11 Family(1/2)
802.11a:6 to 54 Mbps in the 5 GHz band
802.11b (WiFi, Wireless Fidelity):5.5 and 11 Mbps in the 2.4 GHz band
802.11g:54 Mbps in the 2.4 GHz band
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
IEEE 802.11 MarketSource: Cahners In-Stat
($ Million)
IEEE 802.11 Components
Station (STA) - Mobile hostAccess Point (AP) - Stations are
connected to access points.Basic Service Set (BSS) - Stations and
the AP within the same radio coverage form a BSS.
Extended Service Set (ESS) - Several BSSs connected through APs form an ESS.
Infrastructure vs Ad-hoc Modesinfrastructure network
ad-hoc network
APAP
AP
wired network
ad-hoc network
Multi-hop ad hoc network
Ad hoc Networks
Ad hoc: formed, arranged, or done (often temporarily) for a particular purpose only
Mobile Ad Hoc Network (MANET):A collection of wireless mobile hosts forming a temporary network without the aid of established infrastructure or centralized administration
Applications of MANETs
Battlefields
Disaster rescue
Spontaneous meetings
Outdoor activities
Single-Hop vs Multi-Hop
Single-HopEach node is within each other’s transmission
rangeFully connected
Multi-HopA node reaches other nodes via a chain of
intermediate nodesNetworks may partition and/or merge
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Power Saving - Overview
Battery is a limited resource for portable devices
Power saving becoming a very hot topic is wireless communication
Solutions:PHY: transmission power controlMAC: power mode managementNetwork Layer: power-aware routing
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?
Source: Prof. Tseng
Power Mode Management
doze mode vs. active mode example:
A is sending to BDoes C need to stay awake?
Source: Prof. Tseng
Power-Aware Routing
Routing in an ad hoc network with energy-saving (prolonging network lifetime) in mind
Example:
Source: Prof. Tseng
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SRCN1 N2
DEST
N4N3
IEEE 802.11 PS Mode(1/2)
Power Consumption: (ORiNOCO IEEE 802.11b PC Gold Card)
Vcc:5V, Speed:11Mbps
IEEE 802.11 PS Mode(2/2)
Environments: Infrastructure
Ad hoc (infrastructureless)Single-hopMulti-hop
PS: Infrastructure (1/3) Clock synchronization is required (via TSF)
The AP is responsible for generating beacons each of which contains a valid time stamp
If the channel is in use, defer beacon transmission until it is free
PS: Infrastructure (2/3) A host always notifies AP its mode A PS host periodically wakes up to listen to
beacons AP keeps a PS host awake by sending
”traffic indication map (TIM)”in a beacon for unicast data
AP keeps all PS hosts awake by sending”delivery traffic indication map (DTIM)”in a beacon for broadcast data
PS: Infrastructure (3/3)
PS : 1-hop Ad hoc Network (1/2)
Beacon Interval Beacon Interval
ATIM Window
ATIM Window
Host A
Host B
Beacon
BTA=2, BTB=5
power saving state
power saving state
Beacon
ATIM
ACK
active state
data frame
ACK
Source: Prof. Tseng
PS: 1-hop Ad hoc Network (2/2)
ATIM
ACK
Data Frame
ACK
Host A
Host B
ATIM Window
Beacon Interval
Power Saving Mode
Beacon Interval Beacon Interval Beacon Interval
Beacon
Host C
ATIM
ACK
Data Frame
ACK
Beacon
Beacon
Beacon
Target Beacon Transmission Time (TBTT)
PS: m-hop Ad hoc Network (1/3)
Problems:Clock Synchronization is hard
due to communication delays and mobility
Network Partitionunsynchronized hosts with different wakeup times may not recognize each other
Clock Drift Example
Max. clock drift for IEEE 802.11 TSF (200 DSSS nodes, 11Mbps, aBP=0.1s)
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
Source: Prof. Tseng
PS: m-hop Ad hoc Network (3/2)
Solution:Not to synchronize hosts’ clocks
But to achieveWakeup predictionNeighbor discovery
PS: m-hop Ad hoc Network (3/3)
Three asyn. solutions:Dominating-Awake-IntervalPeriodical-Fully-Awake-IntervalQuorum-BasedRef:
“Power-Saving Protocols for IEEE 802.11-BasedMulti-Hop Ad Hoc Networks,”Yu-Chee Tseng, Chih-Shun Hsu and Ten-Yueng HsiehInfoCom’2002
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Quorum-based PS Protocol
Quorum interval
Touchdown
A PS host’s beacon can be heard twice or more for every n consecutive beacon intervals, which in turn solvesWakeup predictionNeighbor discovery
Observation
A quorum system may be translated to a power-saving protocol, whose power-consumption is proportional to the quorum size.
Questions Can any quorum system be translated to
an asyn. PS protocol?
NO!
Which can be?
Those with the Rotation Closure Property !!
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Contributions
Propose the rotation closure property
Propose the lower bound of the quorum size
Propose a novel quorum systems to be translated to an adaptive PS protocol
What are quorum systems? Quorum:
a subset of universal set UE.G. q1={1, 2} and q2= {2, 3} are quorums under U={1,2,3}
Quorum system: a collection of mutually intersecting quorums
E.G. {{1, 2},{2, 3},{1,3}} is a quorum system under U={1,2,3}
Rotation Closure Property
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) =
Examples of quorum systems
Majority quorum system Tree quorum system Hierarchical quorum system Cohorts quorum system ………
Optimal Quorum Size
Optimal quorum size:k, where k(k-1)+1=n and k-1 is a prime power (K n)
Optimal Quorum Systems
Near optimal quorum systemsGrid quorum systemTorus quorum systemCyclic (difference set) quorum system
Optimal quorum systemFPP quorum system
Torus quorum system
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
FPP quorum system
FPP:Finite Projective Plane
Proposed byMaekawa in 1985
For solving distributed mutual exclusion Constructed with a hypergraph Also a Singer difference set quorum system
E-Torus quorum system
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Analysis (1/3)
Active Ratio:the number of quorum intervals over n,where n is cardinality of the universal set
neighbor sensibility (NS)the worst-case delay for a PS host to detect the existence of a newly approaching PS host in its neighborhood
Analysis (2/3)
Analysis (3/3)
Simulation Model
Area: 1000m x 1000m Speed: 2Mbps Radio radius: 250m Battery energy: 100J. Traffic load: Poisson Dist. , 1~4 routes/s,
each having ten 1k packets Mobility: way-point model (pause time: 20s) Routing protocol: AODV
Simulation ParametersUnicast send 454+1.9 * L
Broadcast send 266+1.9 * L
Unicast receive 356+0.5 * L
Broadcast receive 56+0.5 * L
Idle 843
Doze 27 L: packet length
Unicast packet size 1024 bytes
Broadcast packet size 32 bytes
Beacon window size 4ms
MTIM window size 16ms
Simulation Metrics
Survival ratioNeighbor discovery timeThroughputAggregate throughput
Simulation Results (1/10)
0
20
40
60
80
100
120
100 120 140 160 180 200 220 240 260 280 300 320 340
Simulation time (sec)
Surv
ival ra
tio (
%)
C0(98)C20(98)E0(7x14)E20(7x14)AA0AA20
Survival ratio vs. mobility (beacon interval = 100 ms, 100 hosts, traffic load = 1 route/sec).
Simulation Results (2/10)
Neighbor discovery time vs. mobility(beacon interval =100 ms, 100 hosts, traffic load = 1 route/sec).
0
500
1000
1500
2000
2500
3000
0 5 10 15 20
Moving speed (m/sec)
Neig
hb
or
dis
covery
tim
e (
ms)
C(98)
E(7x14)
Simulation Results (3/10)
Throughput vs. mobility(beacon interval = 100 ms, 100 hosts, traffic load = 1 route/sec).
Simulation Results (4/10)
Survival ratio vs. beacon interval length(100 hosts, traffic load = 1 route/sec, moving speed = 0~20 m/sec with
mean = 10m/sec).
Simulation Results (5/10)
Neighbor discovery time vs. beacon interval length(100 hosts, traffic load = 1 route/sec, moving speed = 0~20 m/sec with
mean = 10m/sec).
0
2000
4000
6000
8000
10000
12000
14000
16000
100 200 300 400
Beacon interval (ms)
Nei
ghbor disco
ver
y tim
e (m
s)
C(98)
E(7x14)
Simulation Results (6/10)
Throughput vs. beacon interval length(100 hosts, traffic load = 1 route/sec, moving speed = 0~20 m/sec with
mean =10m/sec).
Simulation Results (7/10)
Survival ratio vs. traffic load(beacon interval = 100 ms, 100 hosts, mobility = 0~20 m/sec with mean =
10 m/sec).
Simulation Results (8/10)
Throughput vs. traffic load(beacon interval =100 ms, 100 hosts, mobility = 0~20 m/sec with mean =
10 m/sec).
Simulation Results (9/10)
Survival ratio vs. host density(beacon interval = 100ms, traffic load 1 route/sec, mobility = 0~20 m/sec
with mean= 10 m/sec).
Simulation Results (10/10)
Throughput vs. host density (beacon interval = 100ms, traffic load 1 route/sec, mobility = 0~20m/sec
with mean= 10 m/sec).
Outline
IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion
Conclusion (1/2) Quorum systems with the rotation closure
property can be translated to an asyn. PS protocol.
The active ratio is bounded by 1/ n, where n is the number of a group of consecutive beacon intervals.
Optimal, near optimal and adaptive AQPS protocols save a lot of energy w/o degrading performance significantly
Conclusion (2/2)Future work:
To incorporate AQPS protocols with those demanding accurate neighboring node’s information, e.g., geometric routing protocols
To incorporate quorum system concept to wireless sensor networks
To incorporate quorum system concept to Bluetooth technology
Q&A