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


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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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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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Application Battlefields Disaster Rescue Spontaneous Meetings Outdoor Activities

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Outline


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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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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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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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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


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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


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


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


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


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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


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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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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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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)

Presented by Jehn-Ruey Jiang Department of Computer Science and Information Engineering

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