SWIPT/WPT RF Energy Harvesting

1. WIRELESS INFORMATION & POWER TRANSFER FOR
ADVANCED WIRELESS COMMUNICATION SYSTEMS
ECE/NIT TRICHY, INDIA
Prof. Dushantha Nalin K. Jayakody, PhD (Dublin), IEEE Senior Member
Professor at School of Computer Science and Robotics
Head, Infocomm Lab
National Research Tomsk Polytechnic University
RUSSIA
Course Coordinator: Prof. Muthu Chidambaranathan
1
Acknowledgement: Scheme for Promotion of Academic & Research Collaboration (SPARC), Ministry of Human Resource Development, India under the No.P145.

2.  The eventual fate of mobile communication is expected to be completely different from what we
experience today
 Ultra top-notch videos and better wide screen resolutions in devices are forcing to look for better
sustainable power sources or Energy Harvesting from external sources
Evolution of Communication networks
 Over the years there has been remarkable growth of mobile communication
 Increase in subscriber base and limited resource, maintaining desirable QoS became difficult
 These issues led researchers to look into new technologies to improve QoS
 Therefore, mobile communication has been continuously evolving from 1G to 5G
2
Introduction

3. 3
Global Mobile Market
Growth
Overview
4%
CAGR
2014-2020
3.6bn
4.6bn
50%
2014
2020
59%
Penetration Rate
2014
2020
5.4%
CAGR
2014-2020
7.3bn
10bn
2014
2020
39%
2014
2020 69%
3G/4G Connections
Smart Phone
Data Traffic Growth
10 Times(2014-2020)
Overview
2014
$1.4tn
Mobile Operator Revenues
3G
4G
5.9
bn
2.6
bn
2020
$1.15tn
CAGR
3.1%
SIM Connections
Source: CCITT/ITU-T (https://www.itu.int/)

4. 4
Global Data Traffic
Growth
Source: CCITT/ITU-T (https://www.itu.int/)

5. 5
Driving Factors for Data
Growth
Source: CCITT/ITU-T
(https://www.itu.int/)

6. 6
Evolution of Communication Generations
Source: Intel Investor Meeting 2017

7. 7
Evolution Towards 5G
 1~10 Gbps data rates
 1 ms round trip latency
 High bandwidth in unit area
 Enormous number of connected devices
 Perceived availability of 99.999%
 Almost 100% coverage
 Reduction in energy usage (Development of green
technology)
 High battery life
• Connect over 50 billion of wireless capability devices.
• Need to be green and sustainable.
[1]. Qualcomm, ‘’5G –Vision for the next generation of connectivity’’, March, 2015.

8. 8
Evolution Towards 5G cont..
5G
1000x
Mobile Data
Volumes
10x-100x
Connected Devices
5x
Lower Latency
10x-100x
End-user Data Rates
10x
Battery Life for Low Power
Devices
Source: METIS
4
G
3G
2G

9. 9
5G Use Cases
Broadband experience
everywhere anytime
Massive Machine
Type Communication
Critical Machine
Type Communication Mass market
personalized TV

10. [2] Dang S, Amin O, Shihada B, Alouini MS. From a Human-Centric Perspective: What Might 6G Be?. arXiv preprint arXiv:1906.00741. 2019 May 9. 10
6G Use Cases

11. 11
Energy Harvesting from Natural Sources
[3] (PDF) Energy-efficient wireless communications: Tutorial, survey, and open issues. Available from: https://www.researchgate.net/publication/220200753_Energy-efficient_wireless_communications_Tutorial_survey_and_open_issues [accessed Dec 11 2019].
What is energy harvesting?
 The process by which energy is derived from
external sources
What are the importance of energy harvesting?
 Converted energy can be stored in capacitors for
short-term use or in batteries for long-term use
 Allows for the battery to taken out of equation of
an application since it sources energy from the
environment
Ways to harvest energy
 Solar power
 Kinetic energy
 RF energy
 etc.…

12. 12
Energy Problem in Wireless
Communications
 ICT is contributing heavily in global greenhouse gas emission since the amount of energy for ICT increases dramatically
 It is reported that the total energy consumed by the infrastructure of cellular wireless networks, wired communication
networks, and internet takes up more than 3% of the worldwide electric energy consumption nowadays [3]
 On the other hand, mobile terminals in wireless systems necessitate energy saving since the development of battery
technology is much slower as compared with the increase of energy consumption
 Recently, energy-efficient system design has been received much
attention in both industrial and academia
[3] (PDF) Energy-efficient wireless communications: Tutorial, survey, and open issues. Available from: https://www.researchgate.net/publication/220200753_Energy-efficient_wireless_communications_Tutorial_survey_and_open_issues [accessed Dec 11 2019].
 Recently, several attempts have been made to implement self sustainable
communication systems with EH techniques

13. 13
Energy Problem in Wireless
Communications
 Emergence of multi-media rich wireless applications has created a high demand for energy.
 Therefore, limited operational lifetime of such wireless terminals imposes strict constraints on the network
performance.
 Energy harvesting communications have emerged as a viable solution to supply power to wireless devices by letting
them scavenge energy from resources such as photovoltaic, wind, vibrational, thermoelectric, and RF signals.
 Characteristics of the propagation environment is an important factor for wireless power transmission and the received
power level depends on the range of frequencies used.
 3 Main EF-EH techniques; Wireless Energy Harvesting, Wireless Power Transfer (WPT), and Simultaneous Wireless
Information & Power Transfer (SWIPT).
[3] (PDF) Energy-efficient wireless communications: Tutorial, survey, and open issues. Available from: https://www.researchgate.net/publication/220200753_Energy-efficient_wireless_communications_Tutorial_survey_and_open_issues [accessed Dec 11 2019].

14. 14
Definition: This approach refers to harvesting energy from the ambient RF signals available in the environment.
While solutions based on TV broadcasting, WiFi, and GSM signals have been developed, an issue with the
approach is the variable nature of the ambient RF signal sources.
 The efficiency of the RF energy harvester depends on
 Efficiency of the antenna
 Accuracy of the impedance matching between the antenna and the voltage multiplier
 Power efficiency of the voltage multiplier in rectifier circuit that converts the received RF signals to DC voltage
 Pathloss and shadowing effects ec.
Wireless Energy
Harvesting cont..

15. 15
Wireless Energy
Harvesting
Wireless sources for energy harvesting
 Ambient RF sources
 Static ambient RF sources
• Stable sources such as TV and radio towers
 Dynamic ambient RF sources
• Time varying sources such as Wi-Fi access point and
licensed users in a cognitive radio networks

16. 16
System Architecture of RF energy harvesting device
 An RF energy harvesting node consists of the following major
components
 Application
 A low power microcontroller, to process data from the application
 A low-power RF transceiver
 An energy harvester
 An impedance matching
 Rectifier circuit
 Power management module – Adopt two methods to control the incoming energy flow
• Harvest-use
• Harvest-store-use
 Energy storage or rechargeable battery
RF Energy Harvesting
cont..
[5] X. Lu, P. Wang, D. Niyato, D. I. Kim and Z. Han, ‘’Wireless Networks With RF Energy Harvesting: A Contemporary Survey’’, in IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 757-789, Secondquarter 2015.
Fig. The schematic diagram of the WPT module

17. 17
Wireless Energy
Harvesting cont..
 Wireless Energy harvesting
 Converts RF signal energy into DC power
 RF energy is available in a wide array of frequency bands due to
everyday technologies
 Cell Phones
 Radio Towers
 Wi-Fi routers
 Laptops
 TV signals
Source Source Power Frequency Distance Energy harvested
rate
Isotropic RF Tx 4 W 902-928 MHz 15 m 5.5 µW
Isotropic RF Tx 1.78 W 868 25 m 2.3 µW
TX91501
Powercaster Tx
3 W 915 MHz 5 m 189 µW
TX91501
Powercaster Tx
3 W 915 MHz 11 m 1 µW
KING-TV tower 960 kW 672-680 MHz 4.1 km 60 µW
Table. Experimental data of RF EH in various scenarios
[4] X. Lu, P. Wang, D. Niyato, D. I. Kim and Z. Han, ‘’Wireless Networks With RF Energy Harvesting: A Contemporary Survey’’, in IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 757-789, Secondquarter 2015.

18. 18
Wireless Energy
Harvesting cont..
[6] Hemour S, Wu K. Radio-frequency rectifier for electromagnetic energy harvesting: Development path and future outlook. Proceedings of the IEEE. 2014 Oct 14;102(11):1667-91.
[7] Valenta CR, Durgin GD. Harvesting wireless power: Survey of energy-harvester conversion efficiency in far-field, wireless power transfer systems. IEEE Microwave Magazine. 2014 May 6;15(4):108-20.
Existing Practical Results
 Assuming input power 1 Watt, 5-dBi Tx/Rx antenna gain, a continuous wave at 915 MHz [6][7]
• 50% at 1m
• 25% at 10m
• 5% at 30m
 However, when input power decrease energy harvesting efficiency also decrease as follows
• Input power 10 mW -> 80%
• Input power 100 μW -> 40%
• Input power 10 μW -> 20%
• Input power 1 μW -> 2%
 This is due to the rectifier sensitivity with the diode not being easily turned on at low input power
 Thus, different no of diodes need to be included in rectifying antenna depends on the received input power

19. 19
RF Energy Harvesting
cont..
[6] Clerckx B, Bayguzina E. Low-complexity adaptive multisine waveform design for wireless power transfer. IEEE Antennas and Wireless Propagation Letters. 2017 May 23;16:2207-10.
Fig. Examples of single series, voltage doubler, and diode bridge rectifiers,
designed for an average RF input power of −20dBm at 5.18GHz [6]
• Match the antenna impedance to the rectifier input impedance
• A single diode is commonly preferred at low power (1-500 µW) because the
amount of input power required to switch on the rectifier is minimized
• Multiple diodes are on the other hand favored at higher input power,
typically above 500 µW
• Topologies using multiple rectifying devices each one optimize for different
range of input power levels also is a possibility

20. 20
The Diode Linear and Nonlinear
Models
[6] Clerckx B, Bayguzina E. Low-complexity adaptive multisine waveform design for wireless power transfer. IEEE Antennas and Wireless Propagation Letters. 2017 May 23;16:2207-10.
Fig. Diode I – V characteristics
• Region corresponds diode linear model
• Region corresponds diode non-linear model
• Diode act as a resistor

21. 21
The Saturation Nonlinear Model
[6] Clerckx B, Bayguzina E. Low-complexity adaptive multisine waveform design for wireless power transfer. IEEE Antennas and Wireless Propagation Letters. 2017 May 23;16:2207-10.
• Saturated non-linear model characterizes another source of non-linearity in the rectenna that originated from the
saturation of the output DC power beyond a certain input RF power due to the diode breakdown
• Diode breakdown occurs when the diode is reversed biased with a voltage across the diode being larger than the diode
breakdown voltage
• At such a voltage, the breakdown is characterized by a sudden increase of the current flowing in the opposite direction
• This can occur typically when the input power to the rectifier is too large for the power regime it has designed for
Maximal harvested power (constant)
Constant a and b capture the joint
effects of resistance, capacitance
and circuit sensitivity
Received power

22. 22
Wireless Powered-
Communications
 Wireless Power Transfer (WPT)
 Power transfer in one direction
 Continuos and controllable transfer
 Applications: charging mobile device and sensor
 Techniques: Inductive coupling, Coupled magnetic resonance, EM
radiation, RF energy beamforming
 Wireless Powered Communication Network (WPCN)
 Wireless power transfer in the downlink
 Information transfer with wireless harvested energy
 Doubly near-far problem
 Applications: sensor network charging and info collection, RFID
 Simultaneous Wireless Information and Power Transfer (SWIPT)
 Info and energy transmit simultaneously in downlink
 Applications: heterogeneous sensor networks, IoT devices, cellular
system
 Rate-and-energy tradeoff
 Wirelessly Powered Backscatter Communication (WPBC)
 Energy is transferred in the down-link and information is transferred in
the uplink
 Backscatter modulation at a tag is used to reflect and modulate the
incoming RF signal for communication with a reader
 A receiver cannot simultaneously harvest energy and
decode information
 Different receiver sensitivities
 Wireless information receiver: > -60dBm
 Wireless energy receiver: > -10dBm

23. 23
Wireless Power Transfer
(WPT)
 WPT concept was originally devised by Nikola Tesla in the 1890s
 Refers to the transmission of electrical energy from a power source by means of electromagnetic
fields, to an electrical component or a portion of a circuit that consumes electrical power without the
aid of wired interconnections
Fig. RF Wireless Power Transfer
Non-radiative (Near-Field)
 Techniques
 Inductive Coupling
 Resonant Inductive Coupling
 Air Ionization (lightening)
 Capacitive coupling
 Applications
 Electric automobile charging
 Consumer Electronics
 charging cellular phones, laptops,
and other portable electronic
devices
 Industrial applications
Radiative (Far-Field)
Techniques
 RF Power Transmission
 LASER Power Transmission
Applications
 Solar power satellites
 Wireless powered drone aircraft
 Cellular networks
 Wireless sensor networks
 Internet of Things (IoT)
 Very low power devices or sensor
network
 High power space, military, or
industrial applications

24. 24
Simultaneous Information and Power
Transfer (SWIPT)
 SWIPT, a recently developed technique, which allows signals that carry information
also to be used to harvest and transfer energy
 In general, EH and ID not possible to be performed on the same received signal
 Single antenna receiver may not be able to facilitate a reliable energy supply
Fig. SWIPT via static and mobile base stations
SWIPT Receiver Architecture
Fig. SWIPT Receiver Architecture

25. 25
Interference Exploitation
 Traditional Concept
 Interference is treated as a limiting factor which affects QoE
 Main design goal is to provide low or no interference
 Perfect SI cancellation is not possible due to nonlinear
distortion caused by transmitter and receiver imperfections
 New Concept
 Recently, a focus has been on potential use of interference in
wireless communication systems
 Interference exploitation can improve reliability, security and
achievable rate
 Taking advantage of constructive interference among the users
as a source of both useful information signal energy and
electrical wireless energy
 Interference Exploitation in SWIPT
 Interference plays a notable role in SWIPT enable communication systems
 Once interference link becoming a disturbance for the ID process, it can be useful to EH process
 However, a proper trade-off required between ID and EH
 In constructive interference concept, interference can be harvested both as a source of wireless power
and a source of useful signal power

26. 26
cont..
Noise from the signal
conversion from RF to
baseband
D.N.K. Jayakody, J.Thompson, S. Chatzinotas, S. Durrani, “Wireless Information and Power Transfer: A New Paradigm for Green Communications,” Springer International Publishing, Jul 20, 2017.
Fig. Block diagram of the power splitting SWIPT approach at the receiver with SWIPT beamforming and
constructive SWIPT beamforming

27. 27
Emerging SWIPT Scenarios

28. 28
Communication
 In FD communication both ends of the transmission link can
transmit and receive signals simultaneously
 Not encourage until recently due to the bottleneck of Self
Interference
 FD wireless powered communication
 Exhibit higher throughput gains
 Undesirable SI component can be converted into an
extra source of energy
 FD base stations can receive information and transfer
energy at the same time
 FD nodes capable of WPT are ideal for 5G small cell
implementations
Fig. FD wireless powered bi-directional communication system.
Chapter 2 (M. Mohammadi, B. K. Chalise, and H. A. Suraweera, Full-Duplex Wireless-Powered Communications)of D.N.K. Jayakody, J.Thompson, S. Chatzinotas, S. Durrani, “Wireless Information
and Power Transfer: A New Paradigm for Green Communications,” Springer International Publishing, Jul 20, 2017.

29. 29
Bistatic Scatter Radio for Energy
Harvesting
 Conventional monostatic method: carrier emitter and the reader are in
a single reader box as in widely used RFID systems
Emerging Bistatic scatter radio concept
the carrier emitter is displaced from SDR reader where backscattered signals
are received
long range scatter radio communication for sensor networks
Easier setup with multiple carrier emitters and one centralized reader
 Future Directions
Carrier emitters in Bistatic scatter radio as a Potential RF harvesting source
Exploiting scatter radio emitter’s transmissions to capture much more
unused ambient energy

30. 30
WPT/SWIPT on Cooperative
Relaying
 Two levels of Information and Power cooperation
 First time slot : Access point transmits wireless RF energy and Information Simultaneously. The relays harvest energy from the access point.
 Second time slot: Relay harvested energy uses to re-transmission signalling to the destination.
 Relays can also harvest energy from the RF signals of the UL transmission.
D.N.K. Jayakody, J.Thompson, S. Chatzinotas, S. Durrani, “Wireless Information and Power Transfer: A New Paradigm for Green Communications,” Springer International Publishing, Jul 20, 2017.

31. 31
SWIPT-assisted NOMA
Fig. NOMA basic principle
Fig. NOMA in multi cell scenario
 NOMA and SWIPT concepts can be combined naturally
 SWIPT can be applied to the neighbouring-users to improve
the reliability of the remote user

32. 32
cont..
 Cooperative NOMA and SWIPT communication
concepts can be integrated together
 Carefully selection of network parameters, such as
transmission rate or PS coefficient can lead to
acceptable system performance
 Harvested energy can be used for the relay
transmission without exploiting own battery power
 Future Directions
 Theoretical analysis is required
 Interference exploitation
 Complexity of 5G and requirements of SWIPT in
receiver design.
 Resource Allocation.
 Channel estimation.
Energy Transfer
Fig. NOMA Cooperative with SWIPT

33. 33
Secure WPT/SWIPT
Transmission
Fig. SWIPT scenario in Broadcasting nature
 In SWIPT to expedite the EH process, the transmitter is able to
emit a highly boosted signal
 This prompt an expanded defencelessness to eavesdroppers
 Both power transfer efficiency and information security are
equally important
 Employing separated receiver mode
 Particular receiver assigned for confidential information
decoding
 Rest of the receivers assigned for EH
 Artificial noise will be used to interfere with the eavesdroppers
 Future Directions
 New design of physical layer security in SWIPT enable
communication systems
 Efficient resource allocation
 Analysis of possible solutions in different types of SWIPT
enabled communication networks

34. 34
SWIPT-assisted mmWave
Communication
 mmWave one of key candidates in 5G.
 mmWave has been identified as a promising avenue for WPT due to:
 Very high frequencies
 Narrow beam
 Large array gains
 A dense network with mmWave base stations.
 With the new IoT trend, many low powered connected devices can harvest energy from mmWave RF signals.
Fig. mmWave enabled SWIPT scheme for smart city

35. 35
SWIPT enabled Wireless Sensor
Networks (WSNs)
 WSNs has come to significant attention with IoT
 Some of the devices are very small and place in
hazardous or remote areas with limited human access.
 Replacing batteries or stable power source is an issue for
WSNs.
 SWITP enabled WSNs
 Sensors can harvest energy from natural energy
sources and RF signals transmitted by the base
station.
 Use harvested energy for information transmission
to destinations.
Fig. SWIPT enabled WSN system. Energy harvesting policies based on the
solar and RF WPT & EH
Fig. Illustration of the components of a wireless sensor node
D.N.K. Jayakody, J.Thompson, S. Chatzinotas, S. Durrani, “Wireless Information and Power Transfer: A New Paradigm for Green Communications,” Springer International Publishing, Jul 20, 2017.

36. 36
SWIPT enabled Wireless Sensor
Networks cont..
 Three main energy costs in wireless sensors
 RF transmission and reception
 Information sensing and processing
 Other basic processing while being active (energy consumption of microcontroller, etc. )
 IoT require various more complicated sensing functions with higher energy requirement than transmitter
 Charged coupled device
 Complementary metal oxide semiconductor image sensors
 High rate and resolution acoustic and seismic sensors
 Challenges
 Sensor power consumption
 The age of Information
 Future Directions
 New sensing and transmission protocol
 Analysis if delay related metrics in WSNs
 Use of interference for WSNs EH operations
 Physical layer security in the design of SWIPT enable WSNs
Fig. A clustered SWIPT enabled WSN

37. 37
SWIPT enabled MIMO
Systems
 In MIMO network, all receivers/users terminals are battery limited.
 Most of the works tried to integrate SWIPT with MIMO defines two user groups to serve
 Users receiving information and Users receiving power to recharge their power sources
 Once the quantity of relay antennas grow in the network, sum rate expression and harvested energy have been
derived at considerable amount.
 Benefits
 Massive MIMO system can provide a large number of degree of freedom, which benefits the performance for both ID and EH.
 Enhancement in energy and spectral efficiencies to address the following challenges of practical energy harvesting technique
 Receive low signal strength due to path loss
 Inherent low RF to DC conversion efficiency
 Challenges
 Antenna selection with ID/EH Mode
 A part of antennas for ID and remaining for EH
 Tradeoff b/w achieved throughtput and harvested energy
 Interference effect
 A balance of the trade-off in the presence of interference
 Large number of antennas
 Need of a low-complexity antenna partition strategy. Fig. A basic MIMO broadcast system.
D.N.K. Jayakody, J.Thompson, S. Chatzinotas, S. Durrani, “Wireless Information and Power Transfer: A New Paradigm for Green Communications,” Springer International Publishing, Jul 20, 2017.

38. 38
Systems cont..
 Secure beamforming for MIMO broadcasting with wireless information and power transfer
Fig. The system model of a basic MIMO I-E broadcasting system.
 Q. Shi, W. Xu, J. Wu, E. Song and Y. Wang, “Secure Beamforming for MIMO Broadcasting With Wireless Information and Power Transfer,” IEEE Transactions on Wireless Communications, vol. 14,
no. 5, pp. 2841-2853, May 2015.
Fig. The secrecy rate vs. total transmission power.
Fig. The secrecy rate vs. number of transmit antennas.
Fig. The secrecy rate vs. harvested power.
AN = Artificial Noise

39. 39
SWIPT assisted Device-to-Device
Communication
 D2D communication provides direct communication between
the devices.
 Due to energy constraint in transmitters, SWIPT with D2D
identified as progressive research area.
 User equipment relay harvests energy from base station and
uses it for D2D communication.
 Future Directions
 Limited research conducted on SWIPT enable D2D
communication.
 Following factors need to be address to improve the
power transfer efficiency:
 Power control
 Resource allocations
 Relay node association
 Relay node selection and management
 Mode switching
Fig. SWIPT assisted D2D communication network.

40. 40
• Dushantha Nalin K. Jayakody, John Thompson, Symeon Chatzinotas, and Salman Durrani "Wireless Information and Power Transfer: A New Green
Communications Paradigm", Springer-Verlag New York, USA, April 2018.
• T. D. Ponnimbaduge Perera, D. N. K. Jayakody, S. K. Sharma, S. Chatzinotas and J. Li, "Simultaneous Wireless Information and Power Transfer
(SWIPT): Recent Advances and Future Challenges," in IEEE Communications Surveys & Tutorials, vol. 20, no. 1, pp. 264-302, Firstquarter 2018
• Perera TD, Jayakody DN. Analysis of time-switching and power-splitting protocols in wireless-powered cooperative communication system. Physical
Communication. 2018 Dec 1;31:141-51.
• A. Rajaram, R. Khan, S. Tharranetharan, Dushantha Nalin K. Jayakody , R. Dinis , S. Panic, Novel SWIPT Schemes for 5G Wireless Networks, Sensors,
March 2019. https://doi.org/10.3390/s19051169
• A. Rajaram, Dushantha Nalin K. Jayakody, R. Dinis and N. Kumar, "Receiver Design to Employ Simultaneous Wireless Information and Power
Transmission with Joint CFO and Channel Estimation, " IEEE Access, vol. 7, pp. 9678-9687, 2019
• A. Ranajam, B. Chen, Dushantha Nalin K. Jayakodya and R. Dinis, Modulation-based Simultaneous Wireless Information and Power Transfer, IEEE
Communication Letters
Further Reading

41. 41
Thank You
nalin@tpu.ru / nalin.jayakody@ieee.org
Acknowledgement: Scheme for Promotion of Academic &
Research Collaboration (SPARC), Ministry of Human Resource
Development, India under the No.P145.