simultaneous wireless information and power transfer...

© Robert W. Heath Jr. (2016)

Simultaneous Wireless Information and Power Transfer (SWIPT) at Millimeter Wave (mmWave)

Robert W. Heath Jr., Talha Khan and Ahmed AlkhateebDepartment of Electrical and Computer Engineering, The University of Texas at Austin, USA

www.profheath.org

Supported by the Army Research Office under grant W911NF-14-1-0460, and gifts from Mitsubishi Electric Research Labs, Cambridge and Nokia.


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Millimeter wave wireless power transfer

[1]T.S.Rappaport,R.W.HeathJr.,R.Daniels,andJ.Murdock,MillimeterWaveWirelessCommunications.Pearson Education,2014.[2]S.Rangan etal., “Millimeter-wave cellularwirelessnetworks:Potentialsandchallenges,”Proc.IEEE,vol.102,pp.366–385,Mar.2014.

Is mmWave attractive for wireless power transfer?

mmWave BS

Smart house

Smart building

Smart bridge

Smart person??

Smart car

Large arrays and highly directional beams

Blockage can impair performance

RX

Dense BS deployment

mmWave is come for 5G cellular

mmWave sensitive to blockages [1,2]


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Motivating prior work

[1]J.Charthad etal.,“System-level analysisoffar-fieldradiofrequencypowerdelivery formm-sizedsensornodes,”IEEETrans.CircuitsSyst.I:Reg.Papers,vol.63,pp.300–311,Feb.2016.[2]M.Tabesh etal., “Apower-harvestingpad-lessmillimeter-sized radio,”IEEE J.Solid-StateCircuits,vol.50,pp.962–977,Apr.2015.[3]K.HuangandV.Lau,“Enablingwirelesspowertransferincellularnetworks:Architecture,modelinganddeployment,”IEEETrans.WirelessCommun.,vol.13,pp.902–912,Feb.2014.[4]I.Krikidis,“Simultaneousinformationandenergytransferinlargescale networkswith/withoutrelaying,” IEEETrans.Commun.,vol.62,pp.900–912,Mar.2014.[5]S.Bietal., “Wirelesspoweredcommunication:opportunitiesandchallenges,”IEEECommun.Mag.,vol.53,pp.117–125,Apr.2015.[6]T.Bai andR.Heath,“Coverageandrateanalysisformillimeter-wave cellularnetworks,”IEEETrans.WirelessCommun.,vol.14,pp.1100–1114,Feb.2015.[7]S.Singhetal., “Tractablemodelforrate inself-backhauledmillimeterwavecellularnetworks,”IEEE J.Sel.AreasCommun.,vol.33,pp.2196–2211,Oct.2015.

Millimeter wave energy harvesting circuit design [1-2]

Prior analyses not applicable to mmWave SWIPT [3-7]

SWIPT does not incorporate the key mmWave features [3-5]

Work on mmWave cellular treats SINR and rate coverage only [6,7]

Power consumption in microwatts [1,2]


Network model

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NLOS link

LOS link

Nonconnecteduser

Connected user

Random blockages

mmWaveBS

LOS link

LOS link: not blocked by a building

NLOS link: intercepted by a building

TX/RX beams already aligned

TX/RX beams randomly oriented

Poisson point processes (PPPs) model node locations [1]T.A.Khan,A.Alkhateeb,andR.W.HeathJr.,“Millimeter waveenergyharvesting,” toappearinIEEETrans.WirelessCommun, 2016.[2]T.Bai andR.Heath,“Coverageandrateanalysisformillimeter-wavecellular networks,” IEEETrans.WirelessCommun.,vol.14,pp.1100–1114, Feb.2015.

PPP blockages of random sizes

and orientations [2]


Channel model

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𝜃�̅� MmDistance-dependent path loss:

Path loss intercepts

noise

LOS:NLOS:

𝛿ℓ ∈ M,m, 0 with prob.𝜃2𝜋 ,

�̅�2𝜋 ,1 −

𝜃 + �̅�2𝜋

Directivity gain b/w rx and ℓ𝑡ℎtx:

Rectifier efficiency

Path loss exponents

Link distance

Harvestedenergy

Small-scale fading power: modeled as Γ(𝑁5,

678) for LOS, Γ(𝑁7,

67:) for NLOS link

Sectorized antenna model captures directional arrays

Different propagation characteristics for LOS/NLOS links

Our analytical model captures key mmWave characteristics[1]T.A.Khan,A.Alkhateeb,andR.W.HeathJr.,“Millimeter waveenergyharvesting,” toappearinIEEETrans.WirelessCommun, 2016.[2]T.Bai andR.Heath,“Coverageandrateanalysisformillimeter-wavecellular networks,” IEEETrans.WirelessCommun.,vol.14,pp.1100–1114, Feb.2015.


Performance metrics

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Derived tractable analytical expressions using stochastic geometry [1]

BS density SINR outage threshold

Energy outage threshold

Power splitting ratio

S: useful signal powerI: interference power

Harvested energy

2. Overall success probability (both information and power transfer)

1. Energy coverage probability (wireless power transfer only)


[1]T.A.Khan,A.Alkhateeb andR.W.HeathJr.,“Millimeter waveenergyharvesting,”toappearinIEEETrans.WirelessCommun, 2016.


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Energy coverage probability (wireless power transfer)

Derived tractable analytical expressions using stochastic geometry


T.A.Khan,A.Alkhateeb andR.W.HeathJr.,“Millimeter waveenergyharvesting,”IEEETrans.WirelessCommun, 2016.

BS densityProb. of LOS connection

Directivity gain

Number of terms in approximation (use N=5 )

Path loss exponent

BS transmitpower

Generalized incomplete gamma function


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Overall success probability (info and power)

Energy coverage or SINR coverage expressions recovered as limiting cases


SINR outage threshold

Power splitting ratio

constant - depends on outage thresholds, rectifier efficiency, activation threshold, and circuit noise

SINR coverage probability

Energy coverage probability

BS density

T.A.Khan,A.Alkhateeb andR.W.HeathJr.,“Millimeter waveenergyharvesting,”IEEETrans.WirelessCommun, 2016.


Results: Wireless Power Transfer

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Connected case, already aligned

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Narrower antenna beams improve energy coverage

for connected users

Simulation Parameters: P=43 dBm, W=100 MHz, BS density 100 per sq. km (mmWave), 25 per sq. km (UHF), Single omnidirectional rx antenna for both. No blockage considered for UHF.

narrower beam(larger gain)


Non-connected case, randomly aligned

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Wider antenna beams improve

energy coverage for nonconnected users

Simulation Parameters: P=43 dBm, W=100 MHz, BS density 100 per sq. km (mmWave), 25 per sq. km (UHF), 8 txantennas (UHF), Single omnidirectional rxantenna for mmWave and UHF. No blockage considered for UHF.

wider beam(less gain)

10-15dB worse than connected


Connected case, already aligned

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Millimeter wave energy coverage potentially better

than UHF

Simulation Parameters: P=43 dBm, W=100 MHz, BS density 25 per sq. km (UHF), Tx antenna beam pattern [10 dB,-10 dB, 30°, 330°] (mmW), 8 txantennas (UHF), Single omnidirectional rx antenna for mmWave and UHF. No blockage considered for UHF.

Density increases


Non-connected case, not aligned

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Performance still improves over UHF

Simulation Parameters: P=43 dBm, W=100 MHz, BS density 25 per sq. km (UHF), Tx antenna beam pattern [10 dB,-10 dB, 30°, 330°] (mmWave), 8 txantennas (UHF), Single omnidirectional rx antenna for mmWave and UHF. No blockage considered for UHF.

Density increases

10-15dB worse than connected


Different fractions of connected users

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Optimize antenna beamwidth to

maximize network-wide energy

coverage

Simulation Parameters: P=43 dBm, W=100 MHz, BS density 200 per sq. km, Single omnidirectional rxantenna. Energy outage threshold is -70 dB for connected and -85 dB for nonconnected users.

beamwidth decreases


Results: Simultaneous wireless information and power transfer

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Overall success probability

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Simulation Parameters: P=43 dBm, W=100 MHz, BS density 200 per sq. km, Single omnidirectional rx antenna, energy outage threshold is fixed to –70 dB, circuit noise power is -80 dB, transmit antenna beam pattern is [15 dB, -15 dB, 10°, 350°].

Optimal splitting ratio higher at larger SINR outage

thresholds

Divert more power for information decoder to

improve SINR


Low-power SWIPT receiver architecture

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proposed

digital MRC

Performs well despite lower complexity vs. power hungry digital receivers

RF combining vector implemented by switches

[1] T. A. Khan , A. Alkhateeb, and R. W. Heath Jr.,“Millimeter wave energy harvesting,” to appear in IEEE Trans. Wireless Commun, 2016.


Conclusions

18[1] T. A. Khan , A. Alkhateeb, and R. W. Heath Jr.,“Millimeter wave energy harvesting,” to appear in IEEE Trans. Wireless Commun, 2016.[2] T. A. Khan , A. Alkhateeb, and R. W. Heath Jr.,“Energy coverage in millimeter wave energy harvesting networks,” in Proc. 2015 IEEE GlobecomWorkshops, pp. 1-6, Dec. 2015.

Characterized information and power transfer performance

at mmWave

Proposed low-power switch-based SWIPT receiver architecture

Future Work

Performs well relative to power-hungry digital receivers

SWIPT in mmWave ad hoc networks

low-power SWIPT architecture, 1-bit ADCs

Narrow beams help connected users

Wider beams help nonconnected users

Beamwidth needs to be optimized for the general case


Questions?

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Detailed work available onlineo T. Khan, A. Alkhateeb, R. Heath,“Millimeter wave energy harvesting,” IEEE Trans.

Wireless Commun, vol. 15, no. 9, pp. 6048-6062, Sept. 2016.o T. Khan, A. Alkhateeb, R. Heath,“Energy coverage in millimeter wave energy

harvesting networks,” in Proc. 2015 IEEE Globecom Workshops, pp. 1-6, Dec 2015.

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