Simultaneous Wireless Information and Power Transfer (SWIPT) in 5G Wireless Systems: Opportunities and Challenges

Transcription

1 Simultaneous Wireless Information and Power Transfer (SWIPT) in 5G Wireless Systems: Opportunities and Challenges Shree Krishna Sharma 1, Nalin D. K. Jayakody 2, Symeon Chatzinotas 1 1 Interdisciplinary Center for Security, Reliability and Trust (SnT), University of Luxembourg 2 National Research Tomsk Polytechnic University, Russia and University of Tartu, Estonia 12 th September, 2016, Livorno, Italy

2 Outline 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 2

3 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

4 Introduction Comparison of the main wireless energy transfer techniques 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 , Secondquarter

5 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 Source Isotropic RF Tx Isotropic RF Tx TX91501 Powercast er Tx TX91501 Powercast er Tx KING-TV tower Source Power Time varying sources such as WiFi access point and licensed users in a cognitive radio networks Frequ ency 4 W MHz Dist anc e 15 m Energy harvested rate 5.5 µw 1.78 W m 2.3 µw 3 W m 189 µw MHz 3 W 915 MHz 960 kw MHz 11 m 4.1 km 1 µw 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 , Secondquarter

6 RF Energy Harvesting An architecture of RF energy harvesting device 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 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 , Secondquarter

7 Operating Modes Wireless Power Transfer (WPT) Power transfer in one direction Continuous and controllable transfer Applications: charging mobile device and sensor Downlink Energy flow Information flow Techniques: Inductive coupling, Coupled magnetic resonance, EM radiation, RF energy beamforming SWIPT Base station Transceiver Uplink 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 Energy and/or information receiver 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,

8 SWIPT Receiver Architecture 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 , Secondquarter

9 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

10 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

11 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 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 , Dec.1,

12 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 Illustrations of multi-antenna base station with ID and EH receivers R. Zhang, Wireless Powered Communication: Opportunities and Challenges, ICC Turorial, Sydney, Australia,

13 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 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 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 , Sept.15,

14 Cooperative SWIPT in CR networks 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. Three cooperation schemes Ideal cooperation : primary information is noncausally 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. 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 , May1,

15 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 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

16 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 S. Timotheou, G. Zheng, C. Masouros and I. Krikidis, "Symbol-level precoding in MISO broadcast channels for SWIPT systems," rd International Conference on Telecommunications (ICT), Thessaloniki, 2016, pp M. Alodeh, S. Chatzinotas and B. Ottersten, "Constructive Interference through Symbol Level Precoding for Multi-Level Modulation," 2015 IEEE Global Communications Conference (GLOBECOM), San Diego, CA, 2015, pp

17 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. 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 S. Timotheou, G. Zheng, C. Masouros and I. Krikidis, "Symbol-level precoding in MISO broadcast channels for SWIPT systems," rd International Conference on Telecommunications (ICT), Thessaloniki, 2016, pp

18 Case study on Hardware Impairment in WPCN assisted Cognitive - DF Relaying 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?? 18

19 Two-way relaying with RF energy transfer data frame structure TDBC: EH can be either DS or SFS T MABC: EH can be either DS or SFS D. K. Nguyen and D. N. K. Jayakody, "Self-Powered Two-Way Cognitive Relay Networks: T Protocol Design and Performance Analysis," submitted to IEEE Access 19

20 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 E H Only one B or A transmits RF signal to R in the energy harvesting phase The harvested power at R is E H

21 Effect of Hardware Impairment in Throughput Throughput vs. γ = I P N o (κ 2 A = κ 2 B = κ 2 R = 0. 08, ) 1. Energy transfer policy left a small effect while hardware impairment caused a big loss 2. Rate R A = R B = 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 D. K. Nguyen and D. N. K. Jayakody, "Self-Powered Two-Way Cognitive Relay Networks: Protocol Design and Performance Analysis," submitted to IEEE Access

22 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 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 , May

23 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

24 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

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