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© 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.
© Robert W. Heath Jr. (2016)
2
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]
© Robert W. Heath Jr. (2016)
3
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]
© Robert W. Heath Jr. (2016)
Network model
4
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]
© Robert W. Heath Jr. (2016)
Channel model
5
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.
© Robert W. Heath Jr. (2016)
Performance metrics
6
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)
Energy outage threshold
[1]T.A.Khan,A.Alkhateeb andR.W.HeathJr.,“Millimeter waveenergyharvesting,”toappearinIEEETrans.WirelessCommun, 2016.
© Robert W. Heath Jr. (2016)
7
Energy coverage probability (wireless power transfer)
Derived tractable analytical expressions using stochastic geometry
Energy outage threshold
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
© Robert W. Heath Jr. (2016)
8
Overall success probability (info and power)
Energy coverage or SINR coverage expressions recovered as limiting cases
Energy outage threshold
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.
© Robert W. Heath Jr. (2016)
Results: Wireless Power Transfer
9
© Robert W. Heath Jr. (2016)
Connected case, already aligned
10
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)
© Robert W. Heath Jr. (2016)
Non-connected case, randomly aligned
11
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
© Robert W. Heath Jr. (2016)
Connected case, already aligned
12
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
© Robert W. Heath Jr. (2016)
Non-connected case, not aligned
13
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
© Robert W. Heath Jr. (2016)
Different fractions of connected users
14
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
© Robert W. Heath Jr. (2016)
Results: Simultaneous wireless information and power transfer
15
© Robert W. Heath Jr. (2016)
Overall success probability
16
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
© Robert W. Heath Jr. (2016)
Low-power SWIPT receiver architecture
17
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.
© Robert W. Heath Jr. (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
© Robert W. Heath Jr. (2016)
Questions?
19
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.