| 1. |
- De, Swades, et al.
(författare)
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Stochastic Solar Harvesting Characterization for Sustainable Sensor Node Operation
- 2019
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Ingår i: IET Wireless Sensor Systems. - : Institution of Engineering and Technology (IET). - 2043-6386 .- 2043-6394. ; 9:4, s. 208-217
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Tidskriftsartikel (refereegranskat)abstract
- Self-sustainability of low power wireless sensor nodes is the need of the hour to realize ubiquitous wireless networks. To address this requirement we investigate the practical feasibility of sustainable green sensor network with solar-powered nodes. We propose simple yet efficient (i) analytical circuit model for solar panel assisted supercapacitor charging and (ii) statistical model for characterizing the solar intensity distribution. Combining these circuit and statistical models, we derive a novel solar charging rate distribution for the solar-powered supercapacitor. To gain analytical insights, we also propose an ideal diode based tight approximation for the practical supercapacitor charging circuit model. The accuracy of these proposed analytical models have been validated by extensive numerical simulations based on the real-world data, i.e., solar intensity profile and solar panel characteristics. The derived solar charging rate distribution is used to investigate the supported sampling rate of the node with different varying number of on-board sensors for a given energy outage probability. Results suggest that for an energy outage probability of 0.1, at New Delhi, a 40 F supercapacitor and a 3 W solar panel can support the operation of Waspmote with 6 on-board toxic gas sensors with a sampling rate of 65 samples per day. Further, we use the proposed models to estimate the practical supercapacitor and solar panel sizes required to ensure sustainability of sensor node operation at different geographical locations with varying sensing rate.
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| 2. |
- Kaushik, K., et al.
(författare)
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Experimental demonstration of multi-hop RF energy transfer
- 2013
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Ingår i: 2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467362351 ; , s. 538-542
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Konferensbidrag (refereegranskat)abstract
- Batteries of field nodes in a wireless sensor network pose an upper limit on the network lifetime. Energy harvesting and harvesting aware medium access control protocols have the potential to provide uninterrupted network operation, as they aim to replenish the lost energy so that energy neutral operation of the energy harvesting nodes can be achieved. To further improve the energy harvesting process, there is a need for novel schemes so that maximum energy is harvested in a minimum possible time. Multi-hop radio frequency (RF) energy transfer is one such solution that addresses these needs. With the optimal placement of energy relay nodes, multi-hop RF energy transfer can save energy of the source as well as time for the harvesting process. In this work we experimentally demonstrate multi-hop RF energy transfer, wherein two-hop energy transfer is shown to achieve significant energy and time savings with respect to the single-hop case. It is also shown that the gain obtained can be translated to energy transfer range extension.
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| 3. |
- Kaushik, K., et al.
(författare)
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Low-cost wake-up receiver for RF energy harvesting wireless sensor networks
- 2016
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Ingår i: IEEE Sensors Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-437X .- 1558-1748. ; 16:16, s. 6270-6278
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Tidskriftsartikel (refereegranskat)abstract
- The existing passive wake-up receivers (WuRxs) are radio frequency identification (RFID) tag based, which incur high cost and complexity. In this paper, we study cost-effective and long-range WuRx solutions for range-based wake-up (RW) as well as directed wake-up (DW). In particular, we consider 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. Experimental results show that our developed prototype can achieve a wake-up range of 1.16 m with +13 dBm transmit power. Furthermore, our empirical study shows that at +30 dBm transmit power the wake-up distance of our developed RW module is >9 m. High accuracy of DW is demonstrated by sending a 5-bit ID from a transmitter at a bit rate up to 33.33 kbps. Finally, we present optimized WuRx designs for RW and DW using Agilent advanced design system, which offer up to 5.69 times higher wake-up range for RW and energy savings per bit of about 0.41 mJ and 21.40 nJ, respectively, at the transmitter and the sensor node in DW.
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| 4. |
- Kaushik, K., et al.
(författare)
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RF energy harvester-based wake-up receiver
- 2015
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Ingår i: Sensors Journal IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479982035 - 9781479982028 ; , s. 6270-6278
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Konferensbidrag (refereegranskat)abstract
- Wake-up receivers (WuRxs) can improve the lifetime of a wireless sensor network by reducing energy consumption from undesirable idle listening. The amplitude level of the incoming RF signal is used by a WuRx to generate an interrupt and wake up the radio of a sleeping sensor node. Existing passive WuRx designs are generally based on RFID tags that incur high cost and complexity. Thus, there is a need for cost-effective and low-complexity WuRxs suited for both long-range and directed wake-ups. In this work, we present a WuRx design using an RF energy harvesting circuit (RFHC). Experimental results show that our RFHC-based WuRx can provide a wake-up range sensitivity around 4 cm/mW at low transmit RF powers (<; 20 mff), which scales to a long wake-up range at high powers. Our design also obtains accurate selective wake-ups. We finally present simulation-based studies for optimizing the design of RFHCs that enhance decoding efficiency with improved rise and fall times.
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| 5. |
- Kumar, Sidharth, et al.
(författare)
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An accurate channel model for optimizing effect of non-LOS component in RF energy transfer
- 2017
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Ingår i: 23rd National Conference on Communications, NCC 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509053568 - 9781509053575 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Self-sustainability of wireless sensor nodes can be realized with the help of controlled radio frequency energy transfer (RF-ET). However due to significant energy loss in wireless dissipation, there is a need for novel schemes to improve the end-To-end RF-ET efficiency. In this work we propose a new channel model for accurately characterizing the harvested DC power at the receiver. This model incorporates the effects of non-line of sight (NLOS) component along with the other factors, such as, polarization of transmitting field, radiation pattern of transmit and receive antennas, polarization loss factor, and efficiency of power harvester circuit. We have validated accuracy of the proposed model by carrying out experiments in an anechoic chamber. In addition to this characterization, we formulate an optimization problem by accounting for the effect of NLOS component to maximize the RF-ET efficiency. To solve this nonconvex problem, we present a computationally-efficient golden section based iterative algorithm. Finally, via numerical investigation we show that significant efficiency improvement can be achieved with
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| 6. |
- Kumar, Sidharth, et al.
(författare)
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RF Energy Transfer Channel Models for Sustainable IoT
- 2018
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Ingår i: IEEE Internet of Things Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2327-4662. ; 5:4, s. 2817-2828
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Tidskriftsartikel (refereegranskat)abstract
- Self-sustainability of wireless nodes in Internet-of-Things applications can be realized with the help of controlled radio frequency energy transfer (RF-ET). However, due to significant energy loss in wireless dissipation, there is a need for novel schemes to improve the end-to-end RF-ET efficiency. In this paper, first we propose a new channel model for accurately characterizing the harvested dc power at the receiver. This model incorporates the effects of nonline of sight (NLOS) component along with the other factors, such as radiation pattern of transmit and receive antennas, losses associated with different polarization of transmitting field, and efficiency of power harvester circuit. Accuracy of the model is verified via experimental studies in an anechoic chamber (a controlled environment). Supported by experiments in controlled environment, we also formulate an optimization problem by accounting for the effect of NLOS component to maximize the RF-ET efficiency, which cannot be captured by the Friis formula. To solve this nonconvex problem, we present a computationally efficient golden section-based iterative algorithm. Finally, through extensive RF-ET measurements in different practical field environments we obtain the statistical parameters for Rician fading as well as path loss factor associated with shadow fading model, which also asserts the fact that Rayleigh fading is not well suited for RF-ET due to presence of a strong line of sight component.
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| 7. |
- Mishra, Deepak, 1990-, et al.
(författare)
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Achievable throughput in relay-powered RF harvesting cooperative sensor networks
- 2016
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Ingår i: Twenty Second National Conference on Communication (NCC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509023615 - 9781509023622 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Aiming at uninterrupted sensor network, we consider a radio frequency (RF) harvesting cooperative communication scenario, where the field nodes (information sources) are powered by RF energy transfer (RFET) from a relay. The relay node can be either connected to the power grid or positioned at some ambient energy harvesting favorable location for the desired energy supply. To further reduce the field nodes’ energy consumption, the relay node decodes-and-forwards the field data to the information sink in a two-hop half-duplex fashion. In the relay-powered cooperative network (RPCN), we derive closed form expressions of the ergodic capacity and achievable throughput for each source-destination pair. Achievable sum-throughput as a function of different system parameters, e.g., RFET time, RF-to-DC conversion efficiency, relay location, channel conditions, and relay transmit power is numerically evaluated. Significant throughput performance imp
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| 8. |
- Mishra, Deepak, 1990-, et al.
(författare)
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Charging time characterization for wireless RF energy transfer
- 2015
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Ingår i: IEEE Transactions on Circuits and Systems - II - Express Briefs. - : Institute of Electrical and Electronics Engineers (IEEE). - 1549-7747 .- 1558-3791. ; 62:4, s. 362-366
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Tidskriftsartikel (refereegranskat)abstract
- Wireless energy transfer to the onboard energy storage element using dedicated radio frequency (RF) energy source has the potential to provide sustained network operations by recharging the sensor nodes on demand. To determine the efficiency of RF energy transfer (RFET), characterization of recharging process is needed. Different from classical capacitor-charging operation, the incident RF waves provide constant power (instead of constant voltage or current) to the storage element, which requires a new theoretical framework for analyzing the charging behavior. This work develops the charging equation for replenishing an energy-depleted storage element by RFET. Since the remaining energy on a sensor node is a random parameter, the RF charging time distribution for a given residual voltage distribution is also derived. The analytical model is validated through hardware experiments and simulations.
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| 9. |
- Mishra, Deepak, 1990-, et al.
(författare)
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Dilemma at RF Energy Harvesting Relay : Downlink Energy Relaying or Uplink Information Transfer?
- 2017
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 16:8, s. 4939-4955
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Tidskriftsartikel (refereegranskat)abstract
- The performance of RF powered communication networks is bottlenecked by the short downlink energy transfer range and the doubly near-far problem faced in uplink information transfer to hybrid access point (HAP). These problems can be resolved by cooperation of an RF energy harvesting node R present between HAP and RF energy harvesting information source S. However, there lies a dilemma at R on whether to transfer its harvested energy to S or to act as an information relay for transferring its data to HAP in a two-hop fashion. This paper resolves this dilemma at R by providing insights into its optimal positions suited for either energy relaying (ER) or information relaying (IR). It also investigates the possibilities of integrated ER and IR along with the regions where neither ER nor IR will be useful. In this regard, while considering Rician fading channels and practical nonlinear RF energy harvesting model, the expression for mean harvested dc power at S via energy transfer from HAP and ER from R is first derived. The closed-form outage probability expression is also derived for decode-and-forward relaying with maximal-ratio-combining at HAP over Rician channels. Using these expressions, insights into optimal relaying mode is obtained along with global-optimal utilization of harvested energy at R for ER and IR to maximize the delay-limited RF-powered throughput. Numerical results validate the analysis and provide insights into the optimal relaying mode.
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| 10. |
- Mishra, Deepak, 1990-, et al.
(författare)
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Effects of Practical Rechargeability Constraints on Perpetual RF Harvesting Sensor Network Operation
- 2016
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 4, s. 750-765
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Tidskriftsartikel (refereegranskat)abstract
- Green perpetual sensor network operation is the need of the hour for critical applications, such as surveillance, military, and environment monitoring. Mobile integrated data collection and recharging is a promising approach to meet this requirement by routinely visiting the field nodes for collecting the sensed data and supplying energy via radio frequency (RF) energy transfer. Practical constraints, such as self-discharge and aging effects of the energy storage element (supercapacitor), significantly impact the renewable energy cycle (REC) and, hence, strongly influence the performance of RF energy harvesting networks. To account for the nonidealities in practical supercapacitors, in this paper, a circuit model for REC is proposed, and corresponding RF charging time and node lifetime expressions are derived. Hardware experiments are performed to validate the proposed REC model. REC for complicated supercapacitor models is characterized using duality principle and a generic simulation model. Using the developed analytical models for practical supercapacitors, the size of network for perpetual operation is estimated, which is demonstrated to be significantly less than that predicted by considering ideal supercapacitor behavior. For example, with three-branch supercapacitor model, the estimated sustainable network size is shown to be nearly 52% less than that offered by the ideal supercapacitor model. © 2013 IEEE.
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