Energy Efficient MAC Protocols For

Ad Hoc Networks

by

Vanitha SivaSubramaniam

Distributed System Design Professor: Dr. Wu Jie

4/10/2003

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OUTLINE

Ad Hoc Networks Power Consumption Solutions For Power Limited Devices Energy Efficient MAC Protocols Conclusion

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AD HOC NETWORKS

Wireless terminals communicating with one another with no pre-existing infrastructure in place– Infrastructure-less

network

Application– Conferencing– Home networking– emergency

services– sensor networks

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筆記型電腦

筆記型電腦

手提電腦

筆記型電腦

膝上型電腦

iBook

筆記型電腦

筆記型電腦

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Problems in Ad Hoc Wireless Networks

Hidden Terminal Exposed Terminal Energy of individual node and of the

network as a whole Mobility

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Power Usage in Different Modes

Model Transmit Receive Standby

GEC Plessey DE6003 2.4 GHz

1.8 W 0.6 W 0.05 W

Lucent’s 15 dBm 2.4 GHz Wavelan radio

1.75 W 1.475W 0.08 W

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Power Consumption in Ad Hoc Networks Wireless hosts are powered by batteries

which provide a limited amount of energy

Third Generation wireless networks carry diverse multimedia traffic – Data, voice and video

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Solutions for Power Limited Devices Low power system design focus on

power usage in CPU, transmitter and receiver embedded in portable devices

Network protocols are designed for energy efficiency

Recent research has been devoted to low-power wireless access protocols like the MAC(Medium Access Protocols)

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Protocol Stack of a Wireless System

Application & Services

OS & Middleware

Network

Data Link

Physical

MAC Protocol

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Functions of Data Link layer

Responsible for wireless link error control

Security (Encryption and Decryption) Mapping network layer packets into

frames Transmission and reception of frames

over the air

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Principles to Conserve Energy at DATA Link (MAC) Level Collision Avoidance Energy Conservation

– Power saving in different mode– Switching between modes

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Medium Access Control Protocol

The MAC protocol simply determines when a node is allowed to transmit its packets and typically controls all access to the physical layer

MAC protocol is responsible for allocating the time frequency space among the mobiles sharing the wireless channel

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DATA Communication in AD Hoc Networks

NODE A (Sender)

NODE B (Receiver)

NODE A Transmitting DATA to NODE B

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2

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RTS- Request To Send

CTS-Clear To Send

ACK-Acknowledge

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Energy Efficient MAC Protocols MACA Protocols

– MACA ( Multiple Access with Collision Avoidance)

– MACA-BI( By Invitation) CSMA Protocols

– DFWMAC (Distributed Foundation Wireless MAC)

– EY-NPMA (Elimination Yield – Non-Preemptive priority Multiple Access)

– DBTMA ( Dual Busy Tone Multiple Access)

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Continue..

Power Conserving MAC Protocols– MARCH (Media Access with Reduced

handshake)– PAMAS (Power–Aware Multi-Access

Protocol with Signaling) Power Control MAC Protocols

– PCM ( Power Control MAC)

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Multiple Access with Collision Avoidance (MACA)

Three way handshake, RTS-CTS-DATA Power control feature: Inhibits a

transmitter when a CTS packet is overheard to limit power

Less DATA packet collisions Resolve the hidden terminal and

exposed node problem

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Handshake in MACA

NODE A (Sender)

NODE B (Receiver)

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MACA-BI( By Invitation)

Two way handshake. RTR (Ready To Receive)-DATA

Receiver sends invitation to the sender Reduces transmit/receive turn around

time ( ie., up to 25 microseconds) Less control packet collisions compared

to MACA

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Handshake in MACA-BI

NODE A (Sender)

NODE B (Receiver)

RTR- Ready To Receive

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DFWMAC ( Distributed Foundation Wireless MAC) Four way handshake RTS-CTS-DATA-ACK A sender node waits for DIFS( Distributed

Inter-Frame Space) before making an RTS attempt

A node enters a SIFS ( Short Inter Frame Space) before sending an ACK frame, DATA and CTS

NAC (Network Allocation Vector) indicates the duration of the current transmission

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Four Way Handshaking in DFWMAC

Sender node

Receiver node

Others

RTS

CTS

DIFSDATA

SIFS

SIFSACK

SIFS

NAV(RTS)NAV(CTS)

NAV(DATA)

NAV- Network Allocation Vector

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EY-NPMA (Elimination Yield-Non- Preemptive Priority Multiple Access) The node senses the medium and starts

transmitting if it finds the channel idle Channel busy: The channel access has

three Phases– Prioritization Phase: Priority is decided– Contention Phase : Nodes of same priority

contend and one station wins• Elimination Phase • Yield Phase

– Transmission Phase : DATA transmission

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DBTMA (Dual Busy Tone Multiple Access)

Two channels– Data Channel- Data packets– Control Channel- RTS and CTS

Two out-of-band busy tones– Receive busy tone– Transmit busy tone

Resolve Hidden terminal problem

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Handshake in DBTMA

NODE A (Sender)

NODE B (Receiver)

Receive Busy Tone

Transmit Busy Tone

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MARCH (Media Access with Reduced Handshake)

Less number of handshakes : Reduces the control overhead by reducing the number of RTS’s along the multi-hop path

Exploits overhearing by using omni directional antenna

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Handshake Mechanism in MARCH

RTS1

CTS1CTS1

DATA

DATA

CTS2

DATA

CTS2

A B C D

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PAMAS ( Power Aware Multi-Access Protocol with Signaling) Separate signal channel Conserves battery power : Power off nodes

not transmitting or receiving Wait-for CTS state :

– After a node sends RTS Await DATA state:

– After a node sends a CTS Transmit DATA state:

– After a node gets a CTS Binary Exponential Backoff (BEB): Doubling

wait time in sender node

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Power Control MAC Protocol

Power Control MAC (PCM)– PCM periodically increases the transmit

power to max. power during the DATA packet transmission

– PCM achieves throughput comparable to IEEE 802.11 with less energy

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CB D

A

E

Transmission Range, Carrier Sensing Zone and Carrier Sensing Range

Transmission Range

Carrier Sensing Zone

Carrier Sensing Range

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Power Control MAC (PCM) Source and destination transmit the

RTS and CTS using max. power. Source transmit DATA using a lower

power level Source node periodically transmits

DATA at max. power, to avoid collision

Destination transmits ACK using minimum power required to reach the source node

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A B

DATA

RTS C D

CTS

ACK

DATA Transmission -Power Control MAC Protocol

A BSender Node Receiver Node

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CONCLUSION

Of the many protocols existing only few of them focus on the conservation of battery power

MACA Vs MACA-BI: MACA-BI reduces transmit/receive turn around time, hence saves power while changing the mode– MACA-BI has less control packet collisions

compared to MACA– In CBR ( Constant Bit Rate) traffic MACA-BI has

high efficiency, but in bursty traffic performance degrades compared to MACA

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Continue

DFWMAC Vs EY-NPMA: DFWMAC has more throughput than EY-NPMA [2]

PAMAS : Power saving range 10%-50% [4] without affecting delay or throughput PCM: Power Control MAC requires a

frequent increase and decrease in transmit power, hence implementation difficult [3]

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References1. Ad Hoc Mobile Wireless Networks: Protocols and Systems, C-K

Toh.

2. Ajay Chandra V.Gummalla and John O. Limb, Georgia Institute of Technology, “Wireless Medium Access Control Protocol”, IEEE communications Survey, 2000.

3. Eun-Sun Jung and Nitin H. Vaidya, “A Power Control MAC Protocol for Ad Hoc Networks”, MOBICOM’02, September 23 – 28, 2002.

4. Suresh Singh and C.S.Raghavendra, “PAMAS-Power Aware Multi-Access Protocol With Signalling for Ad hoc networks”, in ACM Computer Communications Review, July 1998.

5. C-K. Toh, Vasos Vassiliou, Guillermo Guichal and C-H. Shih,”March: A Medium Access Control Protocol for Multihop Wireless Ad Hoc Networks”, Proceedings of IEEE Military Communications Conference( MILCOM), Los Angeles,2000.

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Continue6. Fabrizio Talucci and Mario Gerla, “MACA-BI(MACA By

Invitation): A Wireless MAC Protocol for High Speed Ad Hoc Networking”, Proc. IEEE ICUPC ’97,1997

7. Kyu-Tae Jin and Dong-Ho Cho, “Optimal Threshhold Energy level of Energy Efficient MAC for Energy-limited Ad-hoc Networks, IEEE 2001.

8. Jyh-Cheng Chen, Krishna m. Sivalingam, Prathima Agarwal, and Shalinee kishore, “ A Comparison of MAC Protocols for Wireless Local Networks Based on Battery Power Consumption”, IEEE INFOCOM, Mar. 1998.

9. J. Weinmiller et al., “Performance Study of Access Control in Wireless LAN’s – IEEE 802.11 DFWMAC and ETSI RES 10 HIPERLAN”, Mobile Networks and Application,vol. 2, no1, 1997, pp 55-67.

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