Embed Size (px)
Citation preview
Simultaneous Wireless Information and Power Transfer (SWIPT) in 5G Wireless Systems:
Opportunities and Challenges
Shree Krishna Sharma1, Nalin D. K. Jayakody2, Symeon Chatzinotas1
1Interdisciplinary Center for Security, Reliability and Trust (SnT), University of Luxembourg
2National Research Tomsk Polytechnic University, Russia and University of Tartu, Estonia
12th September, 2016, Livorno, Italy
Outline
2
Introduction
RF Energy Harvesting
Operating Modes
SWIPT Receiver Architecture
Trends in SWIPT
SWIPT Techniques
Example Scenarios
Multi-antenna SWIPT Systems
Multiuser MISO SWIPT Systems
Cooperative SWIPT in CR networks
Massive MIMO enabled SWIPT systems
SWIPT with Symbol Level precoding
Case study
Research Challenges
Conclusions
Introduction
Wireless Energy 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
3
Introduction
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.
Comparison of the main wireless energy transfer techniques
RF Energy Harvesting
Main Characteristics Controllable and constant energy transfer over distance for RF energy harvesters
In a fixed scenario, harvested energy is predictable and relatively stable over time due to fixed distance
Rate-energy tradeoff
Doubly near-far problem
RF Sources for energy harvesting
Dedicated RF Sources For the applications with QoS constraints
High deployment cost
Ambient RF Sources
Static ambient RF sources Stable sources such as TV and radio towers
Dynamic ambient RF sources
Time varying sources such as WiFi access point and licensed users in a cognitive radio networks
5
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
Experimental data of RF energy harvesting in various scenarios
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.
RF Energy Harvesting
6
An architecture of RF energy harvesting device
X. Lu, P. Wang, D. Niyato, D. I. Kim and Z. Han, ‘’Wireless Networks With RF Energy Harvesting: A ContemporarySurvey’’, in IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 757-789, Secondquarter 2015.
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 that converts the received RF signals to DC voltage
Operating Modes
Wireless Power Transfer (WPT)
Power transfer in one direction
Continuous and controllable transfer
Applications: charging mobile device and sensor
Techniques: Inductive coupling, Coupled magneticresonance, 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
7
SWIPT Base station
Transceiver
Energy and/or information
receiver
Downlink
Uplink
Energy flow
Information flow
A receiver cannot simultaneously harvest energy and decode information
Different receiver sensitivities Wireless information receiver: > -
60dBm Wireless energy receiver: > -
10dBm
R. Zhang, “Wireless Powered Communication: Opportunities and Challenges’’, ICC Turorial, Sydney, Australia, 2014.
SWIPT Receiver Architecture
8
Types of SWIPT receivers (a) Separated receiver, (b) Time Switching, (c) Power splitting, (d) Integrated receiver
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.
Trends in SWIPT
Harvest and then transmit protocol
Rate-energy trade-off analysis for various networks
Joint Energy & Information Scheduling and Resource Allocation
Dynamic power splitting and antenna switching
Location based transmission scheduling
Harvest energy when user is close to BS
Receive information when user is far from BS
Joint information and energy beamforming
Opportunistic energy harvesting in cognitive radio networks
Crowed Harvesting
9
Trends in SWIPT
Techniques to deal with doubly near-far problem User Cooperation
Cooperative/collaborative SWIPT: Energy/information relaying
Joint beamforming (downlink) and power control (uplink)
Adaptive time allocation in the uplink
Exploitation of interference Interference is harmful to wireless information transmission (treated as noise if not
decodable at receiver
but helpful to wireless energy transmission (additional source of energy harvesting at the receiver)
SWIPT in massive MIMO and mmWave wireless systems
SWIPT in wideband multicarrier systems
10
SWIPT Techniques
Time Division Mode Switching (TDMS) Scheme Transmission interval into two time slots and two receivers coherently switch between the EH and ID
modes
In one time slot, both receivers operate in the EH mode, whereas,
In the other time slot, both receivers switch to the ID mode.
TDMA Scheme In each time slot of TDMA scheme, one receiver operates in the ID mode and the other receiver
operates in the EH mode.
TDMA via Deterministic Signal for Energy Harvesting If one user operates in the EH mode, the transmitter may simply transmit some deterministic signals
(e.g., training/pilot signals) known to both receivers
Power Splitting Scheme The received signal is split into two parts for simultaneous EH and ID
11
C. Shen, W. C. Li and T. H. Chang, "Wireless Information and Energy Transfer in Multi-Antenna Interference Channel," in IEEE Transactions on Signal Processing, vol. 62, no. 23, pp. 6249-6264, Dec.1, 2014.
Multi-antenna SWIPT Systems
Example: MISO broadcast system: exploit near-far channel conditions
Schedule near users for energy harvesting (EH)
Schedule far users for information decoding (ID)
Multi-antenna Interference channel
Cross-link signals can degrade the information sum rate
At the same time boosts energy harvesting of the receivers
12
Illustrations of multi-antenna base station with ID and EH receivers
R. Zhang, “Wireless Powered Communication: Opportunities and Challenges’’, ICC Turorial, Sydney, Australia, 2014.
Multiuser MISO SWIPT Systems
Scenario: Multi-antenna AP transmitting simultaneously to multiple single-antenna
receivers which implement either EH or ID, but not both at the same time
Problem :joint information and energy transmit beamforming design to maximize the
weighted sum-power transferred to all EH receivers subject to a given set of minimum SINR
constraints at different ID receivers
Two types of ID receivers
Type I do not possess the capability of cancelling
the interference from simultaneously transmitted energy signals
Type 2 and possess the interference cancellation capability
13 J. Xu, L. Liu and R. Zhang, "Multiuser MISO Beamforming for Simultaneous Wireless Information and Power
Transfer," in IEEE Transactions on Signal Processing, vol. 62, no. 18, pp. 4798-4810, Sept.15, 2014.
With Type I ID receivers, separate information and energy
beamforming design approach performs severely worse
than the optimal joint design
In contrast, dedicated energy beamforming is beneficial
when ID receivers possess the capability of cancelling the
interference from energy signals, even with suboptimal
designs
Cooperative SWIPT in CR networks
14
Two level Information and energy cooperation First phase: Information cooperation
PT broadcasts the primary signal and after receiving it, the ST retransmits it to the PU
Second phase: energy cooperation
PT transmits power to the ST via either cable or wireless medium, such that the ST can obtain extra power to help the PU, as well as serve its own SU.
G. Zheng, Z. Ho, E. A. Jorswieck and B. Ottersten, "Information and Energy Cooperation in Cognitive Radio Networks,"
in IEEE Transactions on Signal Processing, vol. 62, no. 9, pp. 2290-2303, May1, 2014.
Three cooperation schemes Ideal cooperation : primary information is non-
causally known at the ST and the transmit power can
be shared between the PT and the ST
Power splitting scheme: ST uses part of received
signal for ID and the rest for EH
Time splitting scheme: a fraction of time is reserved
for wireless energy transfer from the PT to the ST and
the rest of time is used for information listening and
forwarding.
Massive MIMO enabled SWIPT systems
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
received 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 throughput and harvested energy
Interference effect
a balance of the tradeoff in the presence of interference
Large number of antennas
Need of a low-complexity antenna partition strategy
15 H. Wang, W. Wang, X. Chen and Z. Zhang, "Wireless information and energy transfer in interference aware massive
MIMO systems," 2014 IEEE Global Communications Conference, Austin, TX, 2014, pp. 2556-2561.
Symbol Level Precoding for SWIPT Systems
Traditional concept
Interference is always harmful
New concept
Taking advantage of constructive interference among the users as a source of both useful
information signal energy and electrical wireless energy
Data-aided precoding (symbol level precoding)
With the knowledge of both the instantaneous CSI and the data symbols at the BS, the
received interference can be constructive or destructive
Destructive interference deteriorates performance while constructive one moves the
received symbols away from the decision thresholds of the constellation, thus improving
the detection.
Symbol level precoding for SWIPT
To exploit the constructive interference for both information decoding and energy
harvesting
16
S. Timotheou, G. Zheng, C. Masouros and I. Krikidis, "Symbol-level precoding in MISO broadcast channels for SWIPT systems," 2016 23rd International Conference on Telecommunications (ICT), Thessaloniki, 2016, pp. 1-5.
M. Alodeh, S. Chatzinotas and B. Ottersten, "Constructive Interference through Symbol Level Precoding for Multi-LevelModulation," 2015 IEEE Global Communications Conference (GLOBECOM), San Diego, CA, 2015, pp. 1-6.
Symbol Level Precoding for SWIPT Systems
Problem: Symbol level precoding design which minimizes the transmit power while guaranteeing QoS and energy harvesting constraints for generic phase shift keying modulated signals.
17 S. Timotheou, G. Zheng, C. Masouros and I. Krikidis, "Symbol-level precoding in MISO broadcast channels for SWIPT
systems," 2016 23rd International Conference on Telecommunications (ICT), Thessaloniki, 2016, pp. 1-5.
A QPSK constellation example for information decoding with constructive interference
Constructive interference can be exploited to improve the signal power as well as act as a source of wireless power transfer
Case study on Hardware Impairment in WPCN assisted Cognitive - DF Relaying
18
Cognitive relay network: No direct link One primary receiver Three nodes relay Rayleigh fading channel
Secondary users RF energy harvesting relay Two-way DF relaying protocol
2 data transmission protocols 2 energy transfer policies
Transmission rule Harvest then transmit Relay transmit data in half-duplex
mode
D. K. Nguyen and D. N. K. Jayakody, "Self-Powered Two-Way Cognitive Relay Networks:Protocol Design and Performance Analysis," submitted to IEEE Access ??
Two-way relaying with RF energy transfer data frame structure• TDBC: EH can be either DS or SFS
19
MABC: EH can be either DS or SFS
T
TD. K. Nguyen and D. N. K. Jayakody, "Self-Powered Two-Way Cognitive Relay Networks:Protocol Design and Performance Analysis," submitted to IEEE Access
Energy Harvesting Phase
• Dual-source (DS) Single-fixed source (SFS)
Both A and B transmit RF signal to R in the energy harvesting phase
The harvested power at R is 𝐸𝐻
Only one B or A transmits RF signal to R in the energy harvesting phase
The harvested power at R is 𝐸𝐻
Effect of Hardware Impairment in Throughput
1. Energy transfer policy left a small effect while hardware impairment caused a big loss
2. Rate 𝑅𝐴 = 𝑅𝐵 =2 [bits/s/Hz], the ceiling throughput are 1.6, 1.07, 1 and 0.67 [bits/s/Hz].
3. α (time ratio) gave a big different on ceiling throughput
Throughput vs. 𝜸 = 𝑰𝑷 𝑵𝒐
(𝜿𝑨𝟐 = 𝜿𝑩
𝟐 = 𝜿𝑹𝟐 = 𝟎. 𝟎𝟖, 𝟎. 𝟏𝟕𝟓 )
D. K. Nguyen and D. N. K. Jayakody, "Self-Powered Two-Way Cognitive Relay Networks:Protocol Design and Performance Analysis," submitted to IEEE Access
Bistatic Scatter Radio for RF 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
Novel research area 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
22 N. Fasarakis-Hilliard, P. N. Alevizos and A. Bletsas, "Coherent Detection and Channel Coding for Bistatic Scatter Radio Sensor Networking," in IEEE Transactions on Communications, vol. 63, no. 5, pp. 1798-1810, May 2015.
Challenges in SWIPT
Rate-energy tradeoff: two competitive objectives
Doubly near-far problem
CSI acquisition for information/energy beamforming
Feedback overhead
the effect of antenna correlation
the effect of imperfect channel reciprocity
Devising low-complexity antenna partition algorithms
Investigating optimal design for joint energy and information beamforming and scheduling
Adaptive bandwidth/carrier allocation, time allocation
Low-complexity transceivers for symbol level precoding
Need of high efficiency microwave power source (transmitter)
Need of high efficiency microwave rectifier (receiver)
All have to be lightweight to reduce deployment cost
23
Conclusions
An emerging concept for 5G and beyond wireless
Emerging trend in exploiting
SWIPT in massive MIMO systems
Cooperative techniques
Data-aided precoding design
Multicarrier systems
SWIPT with NOMA and other 5G technologies
Several challenges from practical perspectives Need of low-complexity solutions
Need of extensive research to implement
Besides technical, environmental, cost and health issues
Hardware impairment in SWIPT assisted wireless networks
24
