IDEA: Integrated Data and Energy Access for Wireless Sensor Networks (April 2015 - March 2020)
Client:Project Sponsor- NSF
- We will research methods for sharing the channel for the charging and data communication functions in the network, while addressing the challenges posed by phase variance and the constructive and destructive interference of energy signals in space.
- We will propose new routing metrics and protocols for creating energy paths, which will charge only selected sensors to ensure data delivery to the sink occurs timely over these pathways. It will yield concrete insights on the relationship between the number of ETs, their placement, the network lifetime, and the data communication capacity given the energy transfer requests within the network.
- We will answer fundamental questions on how much energy can be obtained through indoor ETs, as well as outdoors from the ambient RF environment in the TV band, leading to the creation of spatiol-temporal energy maps.
- We will transform the concept of RF harvesting sensors to a platform for network deployment through a testbed of software-defined radio ETs and circuit designs for RF harvesting boards.
Key Outcomes and Research Results:
1. Software-Defined Wireless Energy Beamforming: We developed and demonstrated a software-defined solution for wirelessly charging the sensors using RF energy. Here, the actions of more than one energy transmitter (ET) were synchronized in phase and frequency in realtime using periodic feedback from the target sensor, but without any common clock reference. The controller selected the optimal subset of ETs to satisfy the energy request from a given sensor, which cooperatively beamform RF energy towards that sensor.
Fig. 1. Prototyping distributed energy beamfomring with USRPs.
Fig. 2. Architecture of software-defined energy beamforming.
Fig. 3(a) Network architecture of HYDRA where sensors are powered by joint adhoc beamforming from multiple energy transmitters (ETs) and ambient energy sources.
Fig. 3(b) Average received power density at various locations in the Boston area, from ambient sources as well as when the maximum energy harvesting yield source is intelligently chosen through the so called 'cognitive EH' approach.
U. Muncuk, S. Mohanti, K. Alemdar, M Y. Naderi, K. R Chowdhury, “Software-defined Wireless Charging of Internet of Things using Distributed Beamforming," ACM SenSys 2016 - The ACM Conference on Embedded Networked Sensor Systems, Stanford, CA, USA, November 2016. PDF
K. Chowdhury, and M.Y. Naderi, “Distributed Wireless Charging System and Method,” U.S. Application No.: 62/308298.
2. Simultaneous Wireless Energy Transfer and Communication: When data communication and RF energy recharging occur in-band, sharing the RF medium and devoting separate access times for both operations raises architectural and protocol level challenges. We developed a method of concurrent transmission of data and energy to solve this problem, allowing ETs to transmit energy and sensors to transmit data in the sameband synchronously. Our key idea concerned devising a physical layer modulation scheme that allows the data transmitting node to introduce variations in the envelope of the energy signal at the intended recipient. We implemented a proof-of-concept receiver, modeled and validated through extensive experimentation. We also designed a new physical layer mechanism for guaranteed successful delivery of information in a point-to-point link.
Fig. 4. Energy management functions at the sensor, with the harvested energy budget feeding both the sensing as well as future transmission needs.
R. G. Cid-Fuentes, M. Y. Naderi, S. Basagni, K. Chowdhury, A. Cabellos-Aparicio, E. Alarcon, "On Signaling Power: Communications over Wireless Energy", IEEE INFOCOM 2016, San Francisco, CA, USA. PDF
R. G. Cid-Fuentes, M.Y. Naderi, S. Basagni, K. R. Chowdhury, A. Cabellos-Aparicio and E. Alarcón, "An All-Digital Receiver for Low Power, Low Bit-Rate Applications Using Simultaneous Wireless Information and Power Transmission", IEEE ISCAS 2016, Montreal, Canada, May 2016. PDF
3. Wake-Up Receiver & Token Identification using Energy Harvesting: The existing passive wake-up receivers (WuRxs) are radio frequency identification (RFID) tag based, which incur high cost and complexity. In this activity, we studied cost-effective and long-range WuRx solutions for range-based wake-up (RW) as well as directed wake-up (DW). In particular, we considered the case of an RF energy harvesting wireless sensor node and investigate how a low-cost WuRx can be built using an RF energy harvester available at the node.
Fig. 5. Prototype of EH-based passive wake-up receiver.
Fig. 6. (a) Touch energy harvester's schematic, (b) PCB design and token’s schematic.
K. Kaushik, D. Mishra, S. De, K. R. Chowdhury, and W. Heinzelman, “Low-Cost Wake-Up Receiver for RF Energy Harvesting Wireless Sensor Networks,” IEEE Sensors Journal, vol. 16, no. 16, Aug. 2016. PDF
P. Nguyen, U. Muncuk, A. Ashok, K. R. Chowdhury, M. Gruteser, and T. Vu, “Battery-Free Identification Token for Touch Sensing Devices, ACM Conference on Embedded Networked Sensor Systems (SenSys), Stanford, CA, Nov. 2016. PDF
4. Medium Access for Energy Transmitters: We researched, what we call a 'Duty cycled random-phase Multiple Access (DRAMA)' scheme, for wireless RF power transmission. Our approach is based not only in handling the interferences of multiple ETs, but also to benefits from them to broaden the input power range of existing energy harvesters at the sensor nodes. For this, DRAMA relies on the fundamental assumption that efficiency is maximized when the input power varies in time as much as possible, since the energy harvesters operate with increasing efficiency as a function of the input power.
R.G. Cid-Fuentes, M.Y. Naderi, R. Doost, K.R. Chowdhury, A. Cabellos-Aparicio, E. Alarcon, "Leveraging Deliberately Generated Interferences for Multi-sensor Wireless RF Power Transmission", in Proc. IEEE GLOBECOM 2015, San Diego, CA, USA, Dec. 2015. PDF
5. Multi-band Ambient RF Energy Harvesting for Self-powered Sensors: We developed a multi-band adjustable circuit for harvesting from LTE 700MHZ, GSM 850MHZ, and ISM 900MHZ bands with one single circuit. To this end, we designed a tunable impedance matching network composed of off-the-shelf components, such as adjustable capacitors (i.e. trimmers) to adapt the impedance matching network configuration with the selected RF band using a single fabricated ambient RF energy harvesting circuit. Our circuit design is fabricated on the printed circuit board with comprehensive evaluations at each associated frequency to test the power conversion efficiency.
Fig. 7. (a) Overview of our adjustable ambient RF energy harvesting system, (b) Prototype of the circuit.
Fig. 8. (a) Battery-free communications setup with TI eZ430-RF2500 sensors that are powered with LTE signals, (b) Levels of average ambient harvested power at different Boston locations.
U. Muncuk, K. Alemdar, J. D. Sarode, and K. R. Chowdhury, "Multi-band Ambient RF Energy Harvesting Circuit Design for Enabling Battery-less Sensors", IEEE Transaction on Circuits and Systems, May 2017 (submitted)