T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Low Power Wir elessCommunication Network
DesignMethodologies
WayneE. StarkHuaWang,Andrew Worthen,PaulLiang,
RobbyGupta,JackEast,Al Hero,StephaneLafortune,DemosthenisTeneketzis
Universityof MichiganAnn Arbor, MI 48109
e-mail: [email protected]
1
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objectives� Determinethetrade-off betweenperformanceand
energy in awirelesscommunicationnetwork
(TASK I).
Energy
Performance
2
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Observations
� Theperformanceandenergy consumptionof a
wirelessnetwork is determinedby network
protocol,physicallayersdesign(codingand
modulation)aswell aspropagationanddevice
characterisitics
3
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Observations
� Withoutaconstraintonenergy eachof these
subsystemscanbeoptimizedindividually.
� By imposinganenergy constrainttheoverall
systemsoptimizationrequiresacouplingbetween
thedifferentlayersin thesystemhierarchy.
4
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objectives(cont.)
� Provideamethodologyfor integrateddesign,
optimizationandsimulationof acommunication
systemincludingtheapplicationlayer, network
protocol,datalink layerprotocols,physicallayer
anddevice layer.
5
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Example Scenario(Application Layer)
� Mobilesareinitially locatedin a smallgeographicalregionanddesireto keeptrackof thepositionof othernodesasnodesmove towarda destination(situationawareness).
� Eachnodemovestowardthedestination(1 m/s)but withrandomvariations(uniformover a1 m2 area)andknows itsown position(throughGPS).
� Eachnodehasafinite amountof energy for transmissionofmessagesandprocessingof receivedmessages.
6
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Destination
6km
1km
Nodes
7
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Destination
6km
1km
Nodes
8
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
PropagationEffects� Propagationdecreasesthereceivedpower
proportionalto d4.
10−1
100
101
102
103
−120
−100
−80
−60
−40
−20
0
20
distance (m)
Lo
ss (
dB
)
9
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Amplifier Effects� Theamplifierhaslow efficiency at low drive levels
andhighefficiency athigh levels.
0 2 4 6 8 100
10
20
30
40
50
60
70
80
Pin
(mW)
P out (m
W)
0 2 4 6 8 100
10
20
30
40
50
60
70
Pin
(mW)
Powe
r add
ed e
fficie
ncy
(%)
10
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Observations� Thepropagationeffectwouldseemto imply thatroutingthe
messageswouldbepower efficientwith low power for eachlink.
� Thepower efficiency curvewouldsuggestthatasinglebroadcaststrategy wouldbepower efficientsincetheamplifieris not efficientat low drive levels.
� Higheramplifierintermodulationproductsathighdrivelevelscauseincreasedinterference.
� Whatis theroutingalgorithm/amplifierdrive level for
optimumperformancefor a givenenergy constraint?
11
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Methodology� To determinetradeoff betweenperformanceand
energy for complex systemsanappropriate
combinationof simulationandoptimizationis
necessary. Thesystemsaregenerallytoocomplex
for niceanalyticformulationandthusrequire
simulation.
� Thenumberof parametersis very largesoefficient
optimizationandsimulationis necessary.
12
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Methodology (cont.)
� Webreaktheprobleminto layersandare
investigatingthesimulation/optimizationproblem
andthecouplingbetweenlayers.
13
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
PerformanceOptimization Methodology
Network
SimulationOpt
.
Processing
SimulationOpt
.
Device
Simulation
Opt
imiz
atio
n
Opt
.
Alg
orith
ms
OptimizationCriteria
Scenarios/Requirements
BatteryCapacity
ProtocolCompressionType
CodingType
ModulationType
Frequency
AntennaModelAmplifier Models
Parameters Objective Function
14
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Optimization
� How oftenshouldnodestransmittheir location
packets?
� How muchenergy shouldbeallocatedto the
receiver for processingpackets?
� At whatdrive level shouldtheamplifieroperate?
15
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
Let Gi � j= mean-squareerrorfor user j of theposition
of useri,
G � E � � minEct ,Ecr
Ect Ecr � E
minT � q
1N � N 1 �
∑i
∑j !#" i
Gi � j
E � total energy $ Ect � energy for transmitter$
Ecr � energy for receiver
16
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Protocolat Network Layer� Eachnodecarriesa batterywith a certaincapacityand
broadcastsits positionawarenesspacketeveryT seconds.
� Themobilenetwork usestimedivision multiple access(TDMA), whereeachnodein thenetwork hasits owntransmissiontimeslot.
� After a transmission,thenoderetransmitsthesamepacketwith probabilityq if thereis enoughenergy left in thebatteryandenoughtime left in its transmissiontimeslot for onepacket transmission.
17
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
ProcessingLayer Block Diagram
Channel
EncoderInterleaver Modulate Spread PA
Channel
DespreadDemodulateDeinterleaverChannel
Decoder
Pcc PInt Pmod Pspread Pamp
PdespreadPdemodPDeintPcd
18
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Goal for ProcessingLayer
Computethepacketerrorprobabilitiesasa function
of thetransmitterandreceiverenergy andreceived
SNRoptimizedover otherparameters.
Pe � fP � Ect $ Ecr $ SNR�
� minNM � ND
gP � Ect $ Ecr $ SNR$ NM $ ND �
NM % bits of quantizationfor demodulator
ND % bits of quantizationfor decoder&
19
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Initial Models for ProcessingLayer� Convolutional,Turbo,(Golayor Hadamard,otherBlock)
ChannelCode
� BPSKModulationwith RaisedCosineFiltering
� Frequency-HoppedSpread-Spectrum
� AWGN,(Flat(Ideal)Rayleigh,PineStreet,AmericanLegionDrive,Measurements)
� TappedDelayLine MatchedFilter (Equalization)
� CoherentDemodulation
� Viterbi Decoding,Iterative Decoding,(Hadamard/Golay)Decoding
20
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Parametersfor Optimization� Block Lengthof Packet
� PreambleSize(for synchronization)
� Numberof Bits/Hop
� SampleRateat Input to Equalizer/MatchedFilter
� Numberof Bits of Quantizationat Input toEqualizer/MatchedFilter
� Numberof Bits of Quantizationfor CoefficientsinEqualizer/MatchedFilter
21
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Parametersfor Optimization (cont.)
� Numberof Tapsin Equalizer/MatchedFilter
� Bits of QuantizationatOutputof Equalizer/MatchedFilter(Input to Decoder)
� Numberof Bits Quantizationin DecoderMetric (e.g.Turboor Convolutionalor Golayor Hadamard)
� Numberof Iterationsfor Iterative Decoder
22
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
ProcessingEnergy Estimation
� Energy dissipationof digital circuitry is estimated
basedon0.6µmstandardcell technology.
� Energy for thecomputationintensive algorithmis
estimatedby summingtheenergy of the
operations.Theenergy for eachindividual
operationis individually synthesizedusingEpoch
CAD tool.
23
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
� Power/Energy consumptionfor thealgorithm
containingintensivememoryaccessor highly
interconnectedstructureareestimatedfrom the
actualcircuit layoutsynthesis(e.g.turbodecoding,
convolutionaldecoding).
� Thesupplyvoltageof thecircuit usedfor the
algorithmimplementationarescaledto handlethe
rangeof operatingspeedsto getthelowestpossible
energy.
24
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Matched Filter Structur e
w0
xk z-1
Qcw1Qc
dQ xk-1( )dQ (xk )z-1
Qcwp-1
dQ (xk-p+1 )
dQ yk^( )
dQ
dQ dQdQ
25
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
MSE Performancefor Matched Filter Alone
2000 3000 4000 5000 6000 7000 8000 9000 10000
0
0.2
0.4
0.6
0.8
1
1.2
Energy per iteration (pJ)
Mea
n S
qu
are
Err
or
Finite Precision Matched Filter Perf. vs. Energy
26
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Power PerformanceTradeoffs for Codes
0 50 100 150 200 250 3002
2.5
3
3.5
4
4.5
5
5.5
6
6.5
convolutional K=7 bit=hard,3,4,5,6
turbo 1 iteration
N=256 bit=2,3,4
N=512 bit=3,4
N=1024 bit=3,4
turbo 2 iterations
turbo 3 iterations
turbo 4 iterations
Decoder Performance vs PowerS
NR
(E
b/N0)
at B
ER
= 1
0−5
Power Dissipation (mW)
27
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Initial SystemAssumptions� Packet lengthof 224(252)informationbitsor 460
(512)channelbits
� Constraintlength7 convolutionalcode(Turbo
code)
� BPSKmodulationwith squareroot raisedcosine
filter (rolloff=0.3)
� Transmitterfilter implementedwith 19 taps
(infinite quantization)
28
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
� Symbolduration20µs.
� Frequency-hoppedwith 23 (32)bits/hop,20(16)
hopsperpacket
� Nonlinearamplification(modelfrom device layer)
� AdditivewhiteGaussiannoisechannel
29
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Initial SystemAssumptions(cont.)� Variablesignalenergy-to-noisedensityratio (SNR)
� Idealdown conversion(frequency dehopping)
� Matchedfilter implementedwith a tapdelayline
modelwith 19 tapsandND bitsof quantizationfor
thecoefficientsandtheinput sampledat four times
thedatarate.
� Convolutionaldecoderwith NE bits of quantization
� Variablereceiver processingenergy constraint
30
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Packet Err or Probability vs. Ect, Ecr
4
6
8
10
x 10−4 1.922.12.22.32.42.52.62.7
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ecr (J)
Performance vs. Energies
Ect (J)
Pac
ket e
rror
rat
e
PacketErrorProbabilityfor SNR=1,2,3,4,5dB
31
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Notes
This plot shows thebit errorrateasa functionof the
receiverprocessingenergy constraintandthe
transmitteramplifierenergy constraint.Thesurfaces
are,from topdown, SNR=1dB, 2 dB, 3dB,4 dB, and
5 dB. ThegridsareinterpolatedandtheSNR=5dB
datais extrapolatedfrom thesimulationresults.
32
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
Next we renormalizeour resultsby relatingthe
receivedSNRto Ect , N0 � 174dBm/Hzandanoise
figureof 3 dB.
SNR � PoutTsGtGrh2t h2
r ηrηt
d4N0
wherePout � f1 � Ect � .
33
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
distances=3162m,3320m,3558m,3953m
34
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
46
810 x 10
−4
1.8 2 2.2 2.4 2.6 2.8
x 10−4
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies
Ecr (J)
Pac
ket e
rror
rat
e
35
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
46
810 x 10
−4
1.8 2 2.2 2.4 2.6 2.8
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies
Ecr (J)
Bit
erro
r ra
te
36
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Flat RayleighFading (SNR=8,12,15dB)
4
6
8
10
x 10−4
22.12.22.32.42.52.62.7
x 10−4
10−3
10−2
10−1
Ect (J)Ecr (J)
Performance vs. Energies: Flat Rayleigh channelB
it er
ror
rate
37
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Fading with Interleaving (SNR=3,6,9)
4
6
8
10
x 10−4
22.12.22.32.42.52.62.7
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies: Flat Rayleigh channel, SNR=3,6,9 dB
Ecr (J)
Bit
erro
r ra
te
38
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Conclusions
Error ratesignificantlylargerwith Rayleighfading
without interleaving.
39
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
Considerthecasewhereeachnodeis transmittinga
fractionα of thetime andreceiving packetsa fraction
1 α of thetime. Weoptimizethedesignto getthe
lowestpacketerrorratefor agivenaverageenergy per
packet. In otherwords,for E given,find theoptimal
performancesubjectto
αEct � 1 α � Ecr ' E
This givesthesolutionto theabove optimization
40
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
problemusingtheprocessinglayermodelandchannel
propagationmodelgivenabove.
41
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function (d=3320m)
2 3 4 5 6 7 8 9
x 10−4
10−3
10−2
10−1
100
Average packet energy (J)
pack
et e
rror
rat
e
Performance vs. Weighted Total Energy
α=0.125 α=0.5 α=0.8
42
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Thefloor in performanceoccursbecausethe
transmitterhasamaximumoutputpower (becauseof
theamplifier)
43
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function for Turbo Codes
distance=3200m
2 3 4 5 6 7 8 9 10 11
x 10−4
10−4
10−3
10−2
10−1
100
Average packet energy (J)
pack
et e
rror
rat
e
α=0.5
α=0.8
α=0.125
44
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Conclusion
� For low power levelsthetransmittedpowergain in
usingturbocodesdoescompensatefor the
additionalcomplexity at thereceiver.
� For largerpower levelsweexpectthis to reverse.
45
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Optimal Parameters(α ( 0 ) 125)
2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
x 10−4
0.5
1
1.5
2
2.5x 10
−4
aver
age
com
pone
nt e
nerg
y (J
)
2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
x 10−4
10−3
10−2
10−1
100
Average packet energy (J)
pack
et e
rror
rat
e
Uppercurve is receiverpower andlowercurve is
transmitterpower.
46
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Optimal Parameters(α ( 0 ) 5)
3 3.5 4 4.5 5 5.5 6 6.5
x 10−4
0
1
2
3
4
5x 10
−4
aver
age
com
pone
nt e
nerg
y (J
)
3 3.5 4 4.5 5 5.5 6 6.5
x 10−4
10−3
10−2
10−1
100
Average packet energy (J)
pack
et e
rror
rat
e
Uppercurve is transmitterpower andlowercurve is
receiverpower.
47
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Amplifier Effects
Considerdifferentbiasvoltagesasoptimization
parameterratherthanbackoff.
48
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
0 5 10 15 20 25 30 350
20
40
60
80
100
120
140
160
180
Pin (mW)
Pout
(mW)
vd=34 5 6 7
0 5 10 15 20 25 30 350
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Pin (mW)
Powe
r added
efficie
ncy (%
)
vd=34 5 6 7
49
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
0 0.5 1 1.5 2 2.5
x 10−3
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
Average packet energy (J)
pack
et er
ror r
atePerformance vs. Weighted Total Energy
α =0.125α =0.5 α =0.8
IBO=1 dB
50
T� H� E� U� N� I� V� E� R� S I T� Y� O F� M� I� C� H
I�G�A�N�1� 8� 1� 7� ElectricalEngineeringandComputerScience
Objective Function
2.5 3 3.5 4 4.5 5 5.5
x 10−4
10−8
10−6
10−4
10−2
100
Average packet energy (J)
pack
et e
rror r
ate
Performance vs. Weighted Total Energy (α = 0.125)
IBO=2 dB IBO=1 dB IBO=0.5 dB
51
T* H+ E, U- N. I/ V0 E1 R2 S3 I4 T5 Y6 O7 F8 M9 I: C; H
I<G=A>N?1@ 8A 1B 7C ElectricalEngineeringandComputerScience
PerformanceEvaluation
1
2
3
x 10−3
1.922.12.22.32.42.5
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies
Ecr (J)
Pack
et e
rror r
ate
IBO=2 dB
52
T* H+ E, U- N. I/ V0 E1 R2 S3 I4 T5 Y6 O7 F8 M9 I: C; H
I<G=A>N?1@ 8A 1B 7C ElectricalEngineeringandComputerScience
PerformanceEvaluation
01
23
x 10−31.922.12.22.32.42.5
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies
Ecr (J)
Pack
et e
rror r
ate
IBO=1 dB
53
T* H+ E, U- N. I/ V0 E1 R2 S3 I4 T5 Y6 O7 F8 M9 I: C; H
I<G=A>N?1@ 8A 1B 7C ElectricalEngineeringandComputerScience
SystemEvaluation
0
1
2
3
x 10−3
1.922.12.22.32.42.5
x 10−4
10−5
10−4
10−3
10−2
10−1
100
Ect (J)
Performance vs. Energies
Ecr (J)
Pack
et e
rror r
ate
IBO=0.5dB
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Simulation Times
In orderto producethesimulation5 differentPin drive
levelswerechosen,and5 differentSNR’s were
chosenandthenoptimizedover theparameters(bits
of quanitzationfor matchedfilter anddecoder).This
resultedin about250differentsimulationswhich
takesabout3 daysrunningon20SparcUltra 10s.
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Overall Optimization and Simulation
PoutEct
q, T, Ect
E , Ect cr
PePout
Optimization
ProcessingLayer
SNR
Position Error
Device Layer
DistributedSystemLayer
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Overall Optimization and Simulation
Step1: Optimizationprogramdeterminesparameters
Ect D Ecr D T D q.
Step2: Deviceandprocessinglayerdetermines
Pout D Eat D Ear amplifieroutputpower.
Pout E f1 F Ect G
Eat E f2 F Ect GEar E f3 F Ecr G
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This is actualenergy perpacket consumed(which
might belessthantheenergy constraint)
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Overall Optimization and Simulation
Step3: Distributedsystem(network) layer
determinesSNR.
SNR E PoutTsGtGrh2t h2
r ηrηt
d4N0
wherePoutH amplifieroutputpower TsH channelsymbolduration
GtH transmitterantennagain GrH receiver antennagain
htH transmitterantennaheight hrH receiver antennaheight
ηtH transmitterantennaefficiency ηrH receiver antennaefficiency
dH distance N0H thermalnoisepowerdensity
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Overall Optimization and Simulation
Step4: ProcessinglayerdeterminesPe, packeterror
probability. This is actuallydoneoff line resulting
in a function fI 4 usedby thenetwork layer:
Pe E fI 4 F Ect D Ecr D SNRG
Step5: Network layerusesPe to determineif the
simulatedpacket transmissionleadsto acorrect
receptionor not; it thenupdatesthepositionerror.
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Overall Simulation and Optimization
J For agivenparametersetrun 40parallel
simulationsof network performance(mean-square
error).Usethefirst 30 thatfinish.
J Usesimulatedannealingwith thehide-and-seek
algorithmto determineparametersvaluesfor each
iteration
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MSE vs. Energy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 11
2
3
4
5
6
7
8
9
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
one−hop broadcastingmulti−hop routing
Drop Zone 1km x 1km50mW AmplifierConvolutional CodePacket Length 224 bits
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MSE vs. Energy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 11
2
3
4
5
6
7
8
9
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
50mW Amplifier 120mW Amplifier
Drop Zone 2km x 2kmConvolutional CodePacket Length 224 bitsOne−hop Broadcasting
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MSE vs. Energy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 11
2
3
4
5
6
7
8
9
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
one−hop broadcastingmulti−hop routing
Drop Zone 2km x 2km 50mW Amplifier Convolutional Code Packet Length 224 bits
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MSE vs. Energy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 11
2
3
4
5
6
7
8
9
10
11
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
turbo code convolutional code
Drop Zone 1km x 1km50 mW AmplifierPacket Length 224 bitsOne−hop Broadcasting
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MSE vs. Energy
0 1 2 3 4 5 6 7 82.5
3
3.5
4
4.5
5
5.5
6
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
turbo code convolutional code
Drop Zone 2km x 2km 50mW Amplifier Packet Length 1024 bitsOne−hop Broadcasting
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MSE vs. Energy
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 11
2
3
4
5
6
7
8
9
10
11
Battery Capacity (Joule)
Ave
rag
e P
osi
tio
n E
stim
atio
n E
rro
r (m
eter
)Average Position Estimation Error As a Function of Battery Capacity
turbo code convolutional code
Drop Zone 2km x 2km 50 mW Amplifier Packet Length 224 bitsOne−hop Broadcasting
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Conclusions
J A methodologyfor optimizingandsimulatinga
wirelesscommunicationnetwork including,
applicationlayer, network protocol,processing
layeranddevice layerwith significantlylower
computationthanabruteforceapproachhasbeen
achieved.
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J Themethodologyhasbeenverifiedfor anexample
scenario.Themethodologyallowsusto compare
differenttypesof routingalgorithmstakinginto
accountdeviceeffects(amplifiernonlinearity, for
example),propagationeffects,modulationand
codingeffectsaswell aspower consumptionof
digital. circuitry.
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Next Steps:Network Layer
K Comparedifferentroutingalgorithms
K Examinemethodologiesfor differentcontrolfunctionsandtheireffecton thecommunicationalgorithms
K Investigateoptimizationof OFDM for highspeedcommunications.
K Determineamethodologyfor couplingincrementalredundancy transmissionwith theoverall simulation.
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Next Steps:ProcessingLayer
J Incorporateadaptiveequalizationinto simulation
(with preamble).
J Incorporateothercodes(e.g.turbocodes)into the
simulation.
J Incorporateadjacentchannelinterferenceinto the
simulation.
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Next Steps:ProcessingLayer (cont.)
J Investigatedifferentmodulationtechniquesandthe
interactionwith theamplifier
simulation/optimization
J Investigateoptimizationof OFDM for highspeed
communications.
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Next Steps:DeviceLevel
J Incorporateanalogdecodingsimulationfor
iterative receiversinto simulation
J Incorporatefadingchannelmodelsinto simualtion
J Incorporatedirectionalantennasinto
simulation/optimization
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Next Steps:DeviceLevel (cont.)J Incorporatetherecentresultsfor nonlinear
amplifiersbelow into thesimulation(JackEast)
1. Discovereda new techniquefor nonlinearsimulationusingharmonicbalnanceandfixedpoint techniques
2. Extendedconventionalnonlinearmicrowavesimulationtoolsfor widebanddigitally modulatedsignalsusingareducedcomplexity approach
3. Discovereda new optimizationalgorithmthateliminatestehneedfor gradientcalculationwhichsignificantlyreducesthecomputationalcomplexity
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Publication
[1] W. Stark,H. Wang,A. Worthen,P. Liang,
A. Hero,S.Lafortune,andD. Teneketzis,“Low
energy wirelesscommunicationnetwork
design,” 2000AllertonConferenceon
Communication,Control andComputing,
October2000.
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Outside Opinion
Date: Fri, 10 Nov 2000 17:38:43 -0800 (PST)
From: Andrea Goldsmith <[email protected]>
Subject: thanks for the talk slides and paper
Wayne,
Thanks much for the slides and paper from your
Allerton talk. It’s really great stuff.
Andrea
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