An Energy-Efficient An Energy-Efficient MAC Protocol for MAC Protocol for Wireless Sensor Wireless Sensor NetworksNetworksQingchun Ren and Qilian LiangQingchun Ren and Qilian Liang

Department of Electrical Engineering, University of TDepartment of Electrical Engineering, University of Texas at Arlingtonexas at Arlington

IEEE Globecom 2005IEEE Globecom 2005

OutlineOutline

IntroductionIntroduction Protocol description and discussionProtocol description and discussion

– Basic parameter designBasic parameter design– Phase switch schedulePhase switch schedule– Time-slot assignmentTime-slot assignment

SimulationsSimulations ConclusionsConclusions

IntroductionIntroduction

1.1. Most energy-efficient MAC Most energy-efficient MAC protocols assume perfect protocols assume perfect network time synchronizationnetwork time synchronization

– Clock driftsClock drifts exist exist

IntroductionIntroduction

2.2. The The durationduration of power on/off is of power on/off is seldom discussedseldom discussed

3.3. Traffic arrival rate for different Traffic arrival rate for different nodes at different time is nodes at different time is fluctuatingfluctuating

Goals of This PaperGoals of This Paper

Propose an energy-efficient MAC Propose an energy-efficient MAC protocol toprotocol to– Remove tight dependency on time Remove tight dependency on time

synchronizationsynchronization– Apply fuzzy logic rescheduling Apply fuzzy logic rescheduling

schemescheme– Compensate clock driftsCompensate clock drifts

ASCEMAC ASCEMAC (Asynchronous Energy-(Asynchronous Energy-Efficient MAC Protocol)Efficient MAC Protocol)

ASCEMAC Protocol ASCEMAC Protocol ModelModel

1. TRFR-Phase: cluster members transmit message to cluster head

2. Schedule-Phase: cluster head broadcasts it’s scheduling

3. On-Phase: two of the cluster members communicate directly

4. Off-phase: all nodes turn their transceivers off

TRFR Message FormatTRFR Message Format

Information for a cluster head to determine the

scheduling

Parameter DesignParameter Design

Combine

Tn: on phase duration

Tf: off-phase duration

Td: slot time

Wmax: maximum waiting time

λi: traffic arrival rate for node i

Ki: buffer size

Parameter DesignParameter Design

The goal of adjusting parametersThe goal of adjusting parameters– Extend the power off timeExtend the power off time– Adjust the data packet waiting time Adjust the data packet waiting time

to an acceptable valueto an acceptable value

Schedule Message Schedule Message FormatFormat

Interval of Schedule Interval of Schedule BroadcastBroadcast

ξξii is the interval adjusting function is the interval adjusting function Three parameters are used to design Three parameters are used to design ξξii

– Ante1Ante1: ratio of nodes having overflow buff: ratio of nodes having overflow bufferer

– Ante2Ante2: ratio of failure transmission rate: ratio of failure transmission rate– Ante3Ante3: ratio of unsuccessful transmission : ratio of unsuccessful transmission

rate(?)rate(?)

Using Fuzzy FunctionUsing Fuzzy Function

The authors mention that The authors mention that ξξii is defuzz is defuzzified by ified by

E. H. Mandani, “Application of fuzzy logic to approximate reasoning using linguistic systems”, IEEE Trans. On system, Man, and Cybernetics,vol. 26, no. 12, pp. 1182-1191, 1977.

Time-slot assignmentTime-slot assignment

△t1: time difference between nodes

Ts,min: the least time needed to detect thesynchronization information

Successful transmission rate

Successful transmission rate

Rules for Time Slot Rules for Time Slot AllocationAllocation Ante1: traffic arrival rateAnte1: traffic arrival rate Ante2: unsuccessful transmission Ante2: unsuccessful transmission

raterate

SimulationSimulation

Simulation Simulation EnvironmentEnvironment

SimulatorSimulator OPNETOPNET

AreaArea 100m x 100m100m x 100m

Radio rangeRadio range 30m30m

Symbol rateSymbol rate 40 Ksps40 Ksps

Data frame lengthData frame length 1024 bits1024 bits

Clock drift rangeClock drift range 1 to 100us1 to 100us

Successful Successful Transmission RateTransmission Rate

Average Waiting TimeAverage Waiting Time

Average Energy UtilityAverage Energy Utility

Successful Successful Transmission RateTransmission Rate

Node Density Node Density AdaptationAdaptation

Traffic Strength Traffic Strength AdaptationAdaptation

ConclusionsConclusions

ASCEMAC acquires the optimal valueASCEMAC acquires the optimal values of essential algorithm parameterss of essential algorithm parameters– Ensure average successful transmission Ensure average successful transmission

raterate– Decrease the data packet average waitiDecrease the data packet average waiti

ng timeng time– Reduce energy consumptionReduce energy consumption

Thank you!!Thank you!!

AntesAntes

Rescheduling BroacastRescheduling Broacast

Slot AssignmentSlot Assignment