Madhavi W. Subbarao WCTG - NIST

Dynamic Power-Conscious Routing for Mobile Ad-Hoc Networks

Madhavi W. SubbaraoWireless Communications Technology Group

National Institute of Standards and Technology

Madhavi W. Subbarao WCTG - NIST

Outline

• Introduction to MANETs

• Project Overview

• Project Approach

• Results

• Conclusion and Future Directions

Madhavi W. Subbarao WCTG - NIST

Mobile Ad-Hoc Networks (MANET)

• Rapid deployment of autonomous mobile users

• Communication over wireless radio links

• Decentralized structure

• Dynamic topology

• Contend with effects of radio communication

• Stand-alone or connected to larger network

• Examples

– Fire/Rescue operations

– Disaster relief efforts

Madhavi W. Subbarao WCTG - NIST

MANET Routing

• Dynamic routing algorithms: Must adapt to– Entering/departing nodes

– Changes in link quality

– Changes in terrain

– Traffic patterns and interference

– Rate of topological change

• Fast run time compared to rate of topology change

• Low overhead and storage requirements

• High throughput and low packet delay time

• Preserve network requirements (e.g., security)

• Efficient use of power

Madhavi W. Subbarao WCTG - NIST

Motivation

• In emergency situation or disaster, centralized infrastructure may fail

• Research in area focusing on establishing routes– Links either “present” or “absent”

– All “present” links have same link quality

– Generalization - since links have different reliability statistics and power needs!

• Prompted interest to consider– Power consciousness

– Variable link quality

– Distributed routing scheme

Madhavi W. Subbarao WCTG - NIST

ATP / NIST Project Overview

• Investigate importance of power in MANETs

• Make networks more survivable by efficiently using power

• Incorporate physical and link layer structure

• Account for location and surrounding of node

– Capture shadowing and fading effects

– Account for multi-user interference

• Assign cost function indicating TX power needed to reliably communicate over link

• Provide level of “network diversity” by routing around undesirable areas

Madhavi W. Subbarao WCTG - NIST

Benefits of Power-Consciousness

• Prolong life of power supply• LPD & LPI• Less multiuser and adjacent channel interference• Higher spatial reuse• Efficient use of power

– Too low -> disconnected network

– Too high -> excess interference

Madhavi W. Subbarao WCTG - NIST

Minimum Power Routing (MPR)

• Goal: Select path that will require least amount of total power expended, while maintaining acceptable SNR. Alter TX power according to link quality.

• Strategy: Assign link cost as TX power needed to successfully transmit packet on link. Extend concept to other algorithms.

• Transmission from Node i to Node j:

-RX Power

-SNR where

-Compute TX power needed to reliably transmit on link:

ijTijijRij rPKFP

,/

/

ijTijijIijo

Rijij rPS

WPN

DP

)/( WPND

KFS

Iijo

ijij

ijijTij

rSP

Madhavi W. Subbarao WCTG - NIST

MPR implementation

• Use side-information for estimation - test symbols

• Link scale factor estimation :

• Power estimation:

• Link cost update: , = 0.3

• Propagate link costs through network

• Initial approach: use distributed Bellman-Ford algorithm to find most “power-efficient route”

• Comparison between MPR, SD-PC, and MH-PC to see if power-conscious concept benefits MANET routing.

ijTij

ijij

rPS

],[)1(],[ jiCPjiC ij

ijijTij

rSP

Madhavi W. Subbarao WCTG - NIST

Simulation Framework

• Designed and developed simulation framework in OPNET

Madhavi W. Subbarao WCTG - NIST

Simulation experiment: Static network

•16 nodes

•Data rate:10pk/sec

•Load - 10K pk

Efficiency versus packet generation rate for MPR, SD-PC and, MH-PC

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80 100

Packet generation rate (pkt/s)

Eff

icie

ncy MPR

MH-PCSD-PC

Power consumption versus packet generation rate

200300400500600700800

0 50 100

Packet generation rate (pkt/s)

Po

wer

co

nsu

mp

tio

n

(mW

) MPRMH-PCSD-PC

MPR SD-PC MH-PCNumber of hops per

packet3 2.43 1.57 2.5 1.72

Overhead 0.008 0 0 0 0Mean delay perpacket (s)

26 26.35 19.1 25 18.2

Mean power per hop(mW)

96 247 94 257 92

Efficiency 0.94 0.88 0.502 0.90 0.57Throughput (pkt/s) 9.38 8.84 5 9.02 5.77

Madhavi W. Subbarao WCTG - NIST

Power consumption Vs Mobility

200

250

300

350

400

450

500

0 2 4 6 8

Mobility (m/s)

Po

we

r c

on

su

mp

tio

n

(mW

) MPR

MH-PC

SD-PC

Efficiency Vs Mobility

0

20

40

60

80

100

0 2 4 6 8

Mobility (m/s)

Eff

icie

nc

y MPR

MH-PC

SD-PC

Simulation experiment: Mobile network

16 nodes

Data Rate 10 pk/sec

Load - 10K pk

Madhavi W. Subbarao WCTG - NIST

Simulation experiment: Mobile network

MPR efficiency versus update frequency

8082

8486

8890

9294

0 10 20 30

Update frequency (s)

Eff

icie

ncy

Efficiency (data)Efficiency (global)

Variation of mobility for MPR

0

20

40

60

80

100

120

0 2 4 6 8

mobility (m/s)

Eff

icie

nc

y

Efficiency

•Environment same with added mobility - 4m/s

•Mean power per hop averages around 90mW.

Madhavi W. Subbarao WCTG - NIST

MPR Conclusions

• MPR optimizes on link quality and power expended NOT on distance or hops

• Investigation shows benefit by routing on power-conscious route, even though may be longer

• Greatly improve overall efficiency of network by– Routing around heavy shadowing in network

– Altering TX power according to link quality and NOT path loss

• Power-conscious concepts should be extended to other routing protocols.

Madhavi W. Subbarao WCTG - NIST

Future Directions

• Extend power-conscious routing concepts to various distributed routing protocols

• Investigate power-conscious concepts in heterogeneous emergency MANETs (fire, rescue, police, etc.)

• Enhance simulation testbed and compare performance with various MANET protocols

Conference Publications

• IEEE Vehicular Technology Conference Fall 1999

• OPNETWORK Conference Fall 1999