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Sökning: WFRF:(Mishra Deepak)

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4.
  • Ahuja, Bhawna, et al. (författare)
  • Novel QoS-Aware Physical Layer Security Analysis Considering Random Inter-node Distances
  • 2019
  • Ingår i: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781538680889 - 9781538680896
  • Konferensbidrag (refereegranskat)abstract
    • Physical layer security (PLS) in wireless communication has gained recent attention due to the emergence of new technological breakthroughs in this space. Since the internode distances have been noted to play a key role in the desired security performance, we propose a novel quality-of-service-aware PLS model that incorporates the random spatial deployment of the legitimate users and a potential attacker. This proposed model considers practical constraints like maximum separation between legitimate users and eavesdropping capability of attacker. In this regard, a novel concept of eavesdropping zone is also introduced. Eventually, closed-form expressions are derived for secrecy outage probability using the probabilistic inter-node distance distributions between the legitimate users and attacker to shed key analytical insights like optimal parameter designing to achieve a desired secrecy performance. Lastly, specific simulation results, presented to validate the analytical claims and provide key secured system designing perspectives, corroborate the potential of the proposed framework for more accurately characterizing the desired PLS performance from both the legitimate users and attackers point-of-view.
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5.
  • Beal, Jacob, et al. (författare)
  • Robust estimation of bacterial cell count from optical density
  • 2020
  • Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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6.
  • Callejas, Ileana A., et al. (författare)
  • Effect of COVID-19 Anthropause on Water Clarity in the Belize Coastal Lagoon
  • 2021
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • The Coronavirus disease 2019 (COVID-19) pandemic halted human activities globally in multiple sectors including tourism. As a result, nations with heavy tourism, such as Belize, experienced improvements in water quality. Remote sensing technologies can detect impacts of “anthropauses” on coastal water quality. In this study, moderate resolution imaging spectroradiometer (MODIS) satellite data were employed along the Belizean coast to investigate impacts of the COVID-19 shutdown on water quality. The attenuation coefficient at 490 nm, Kd(490), was used as an indicator of water quality, with a lower Kd(490) indicating increased water clarity. Four Coastal Management Zones were characterized by marine traffic as high traffic areas (HTAs) and two as low traffic areas (LTAs). Monthly composites for two periods, 2002–2019 (baseline) and 2020 were examined for Kd(490). For months prior to the COVID-19 shutdown in Belize, there was generally no significant difference in Kd(490) (p &gt; 0.05) between 2020 and baseline period in HTAs and LTAs. Through the shutdown, Kd was lower in 2020 at HTAs, but not for LTAs. At the LTAs, the Kd(490)s observed in 2020 were similar to previous years through October. In November, an unusually active hurricane season in 2020 was associated with decreased water clarity along the entire coast of Belize. This study provides proof of concept that satellite-based monitoring of water quality can complement in situ data and provide evidence of significant water quality improvements due to the COVID-19 shutdown, likely due to reduced marine traffic. However, these improvements were no longer observed following an active hurricane season.
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7.
  • De, Swades, et al. (författare)
  • Stochastic Solar Harvesting Characterization for Sustainable Sensor Node Operation
  • 2019
  • Ingår i: IET Wireless Sensor Systems. - : Institution of Engineering and Technology (IET). - 2043-6386 .- 2043-6394. ; 9:4, s. 208-217
  • 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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8.
  • Gupta, Isha, et al. (författare)
  • Triple Bottom Line : Evidence from aviation sector
  • 2020
  • Ingår i: International Journal of Business Ethics and Governance. - Istanbul, Turkey : EuroMid Academy of Business & Technology (EMABT). - 2717-9923. ; , s. 71-80
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The COVID-19 has spread with alarming speed bringing the global economy to a stand-still. As countries have imposed tight restrictions, the aviation industry is severely hit and its revenues sorely plummeted. The study aims to analyze the impact of Covid-19 on the aviation industry. Its main purpose is to alleviate the pandemic effect by applying the Triple Bottom Line (TBL) approach. TBL mainly addresses sustainability and focuses on three dimensions: people, planet, and performance. The aviation industry can sustain its revenues by adopting disruptive and innovative strategies that can counteract pollution effect (planet scale). Furthermore, it should urgently integrate artificial intelligence and machine learning in its booking system (people scale) to compensate for ongoing travel cancellations, delay, and headcounts reduction.  To regain customers’ confidence, and boost its performance, the aviation industry should apply innovative plans such as electronic waivers, free cancellation, no-fee itinerary change.
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9.
  • Gupta, Nishant, et al. (författare)
  • Trajectory and Resource Allocation for UAV Replacement to Provide Uninterrupted Service
  • 2023
  • Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 71:12, s. 7288-7302
  • Tidskriftsartikel (refereegranskat)abstract
    • Unmanned aerial vehicles (UAVs) have emerged as a specular technology that can assist the terrestrial base stations. However, the battery limitation of UAV inhibits the system performance by decreasing the overall lifespan of coverage provided by the UAV, driving the necessity of replacement and recharging. Thus, the energy-depleted UAV must be returned to a charging station and be replaced by a fully charged UAV to increase the service span. Therefore, this paper presents a novel framework of UAV replacement to maintain coverage continuity in a UAV-assisted wireless communication system when a serving UAV runs out of energy. Our objective during this replacement process is to maximize the minimum achievable throughput to the UAV-served ground users by jointly optimizing the three-dimensional (3D) multi-UAV trajectory and resources allocated to the users from the individual UAVs. The formulated problem is non-convex for which an efficient algorithm based on successive convex approximation and alternating optimization is proposed. Numerical results provide insights into the UAV trajectories and the effectiveness of the proposed scheme compared to the existing benchmark schemes.
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10.
  • Kaushik, K., et al. (författare)
  • Experimental demonstration of multi-hop RF energy transfer
  • 2013
  • 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
  • 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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11.
  • Kaushik, K., et al. (författare)
  • Low-cost wake-up receiver for RF energy harvesting wireless sensor networks
  • 2016
  • Ingår i: IEEE Sensors Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-437X .- 1558-1748. ; 16:16, s. 6270-6278
  • 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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12.
  • Kaushik, K., et al. (författare)
  • RF energy harvester-based wake-up receiver
  • 2015
  • Ingår i: Sensors Journal IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479982035 - 9781479982028 ; , s. 6270-6278
  • 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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13.
  • Kristan, Matej, et al. (författare)
  • The Sixth Visual Object Tracking VOT2018 Challenge Results
  • 2019
  • Ingår i: Computer Vision – ECCV 2018 Workshops. - Cham : Springer Publishing Company. - 9783030110086 - 9783030110093 ; , s. 3-53
  • Konferensbidrag (refereegranskat)abstract
    • The Visual Object Tracking challenge VOT2018 is the sixth annual tracker benchmarking activity organized by the VOT initiative. Results of over eighty trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis and a “real-time” experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. A long-term tracking subchallenge has been introduced to the set of standard VOT sub-challenges. The new subchallenge focuses on long-term tracking properties, namely coping with target disappearance and reappearance. A new dataset has been compiled and a performance evaluation methodology that focuses on long-term tracking capabilities has been adopted. The VOT toolkit has been updated to support both standard short-term and the new long-term tracking subchallenges. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website (http://votchallenge.net).
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14.
  • Kristan, Matej, et al. (författare)
  • The Visual Object Tracking VOT2016 Challenge Results
  • 2016
  • Ingår i: COMPUTER VISION - ECCV 2016 WORKSHOPS, PT II. - Cham : SPRINGER INT PUBLISHING AG. - 9783319488813 - 9783319488806 ; , s. 777-823
  • Konferensbidrag (refereegranskat)abstract
    • The Visual Object Tracking challenge VOT2016 aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 70 trackers are presented, with a large number of trackers being published at major computer vision conferences and journals in the recent years. The number of tested state-of-the-art trackers makes the VOT 2016 the largest and most challenging benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the Appendix. The VOT2016 goes beyond its predecessors by (i) introducing a new semi-automatic ground truth bounding box annotation methodology and (ii) extending the evaluation system with the no-reset experiment.
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15.
  • Kristan, Matej, et al. (författare)
  • The Visual Object Tracking VOT2017 challenge results
  • 2017
  • Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2017). - : IEEE. - 9781538610343 ; , s. 1949-1972
  • Konferensbidrag (refereegranskat)abstract
    • The Visual Object Tracking challenge VOT2017 is the fifth annual tracker benchmarking activity organized by the VOT initiative. Results of 51 trackers are presented; many are state-of-the-art published at major computer vision conferences or journals in recent years. The evaluation included the standard VOT and other popular methodologies and a new "real-time" experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The VOT2017 goes beyond its predecessors by (i) improving the VOT public dataset and introducing a separate VOT2017 sequestered dataset, (ii) introducing a realtime tracking experiment and (iii) releasing a redesigned toolkit that supports complex experiments. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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16.
  • Kumar, Sidharth, et al. (författare)
  • An accurate channel model for optimizing effect of non-LOS component in RF energy transfer
  • 2017
  • Ingår i: 23rd National Conference on Communications, NCC 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509053568 - 9781509053575 ; , s. 1-6
  • 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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17.
  • Kumar, Sidharth, et al. (författare)
  • RF Energy Transfer Channel Models for Sustainable IoT
  • 2018
  • Ingår i: IEEE Internet of Things Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2327-4662. ; 5:4, s. 2817-2828
  • 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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18.
  • Li, Guoxin, et al. (författare)
  • Cooperative NOMA With Incremental Relaying: Performance Analysis and Optimization
  • 2018
  • Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9545 .- 1939-9359. ; 67:11, s. 11291-11295
  • Tidskriftsartikel (refereegranskat)abstract
    • In conventional cooperative non-orthogonal multiple access (NOMA) networks, spectral efficiency loss occurs due to a half-duplex constraint. To address this issue, we propose an incremental cooperative NOMA (ICN) protocol for a two-user downlink network. In particular, this protocol allows the source to adaptively switch between a direct NOMA transmission mode and a cooperative NOMA transmission mode according to a 1-bit feedback from the far user. We analytically prove that the proposed ICN protocol outperforms the conventional cooperative NOMA protocol. In addition, an optimal power allocation strategy at the source is studied to minimize the asymptotic system outage probability. Finally, numerical results validate our theoretical analysis. present insights, and quantify the enhancement achieved over the benchmark scheme.
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19.
  • Li, Gen, et al. (författare)
  • Optimal Open-Loop MIMO Precoder Design
  • 2020
  • Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 24:9, s. 2075-2079
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiple-input multiple-output (MIMO) is a favorable technique that can improve system capacity and performance through spatial multiplexing. However, the performance gets degraded over the correlated wireless channels. In this letter, we consider a point-to-point MIMO system and jointly optimize both the precoding matrix and the difference between two transmit vectors to resist transmit correlation. The simulation results demonstrate that the proposed method can get average 75% gain comparing with the existing method in terms of the minimum pairwise error probability.
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20.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Achievable throughput in relay-powered RF harvesting cooperative sensor networks
  • 2016
  • Ingår i: Twenty Second National Conference on Communication (NCC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509023615 - 9781509023622 ; , s. 1-6
  • 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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21.
  • Mishra, Deepak, et al. (författare)
  • CHANNEL ESTIMATION AND LOW-COMPLEXITY BEAMFORMING DESIGN FOR PASSIVE INTELLIGENT SURFACE ASSISTED MISO WIRELESS ENERGY TRANSFER
  • 2019
  • Ingår i: 2019 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP). - : IEEE. - 9781479981311 ; , s. 4659-4663
  • Konferensbidrag (refereegranskat)abstract
    • Usage of passive intelligent surface (PIS) is emerging as a low-cost green alternative to massive antenna systems for realizing high energy beamforming (EB) gains. To maximize its realistic utility, we present a novel channel estimation (CE) protocol for PIS-assisted energy transfer (PET) from a multiantenna power beacon (PB) to a single-antenna energy harvesting (EH) user. Noting the practical limitations of PIS and EH user, all computations are carried out at PB having required active components and radio resources. Using these estimates, near-optimal analytical active and passive EB designs are respectively derived for PB and PIS, that enable efficient PET over a longer duration of coherence block. Nontrivial design insights on relative significance of array size at PIS and PB are also provided. Numerical results validating theoretical claims against the existing benchmarks demonstrate that with sufficient passive elements at PIS, we can achieve desired EB gain with reduced active array size at PB.
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22.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Charging time characterization for wireless RF energy transfer
  • 2015
  • 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
  • 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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23.
  • Mishra, Deepak, et al. (författare)
  • Coverage-Constrained Utility Maximization of UAV
  • 2019
  • Ingår i: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781538680889 - 9781538680896
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we consider a UAV-assisted communication system comprising of single UAV serving to heterogeneous users having different data rate and coverage demands. Specifically, we propose a novel utility-aware transmission protocol to maximize the UAV utility by allowing it to simultaneously serve the highest possible number of users with available energy resources. In this regard, first we derive a closed-form expression for rate-coverage probability of a user considering Rician fading to incorporate the strong line of sight (LoS) component in UAV communication. Next, we formulate an optimization problem P to maximize the UAV utility under energy resources and rate-coverage constraints. Since, P is non-convex and combinatorial in nature, to provide global optimal solution, an equivalent distributed problem is formulated and a joint optimization algorithm is proposed which provide closed-form solution for joint-optimal power and time allocation. With the help of numerical investigation, we validate our coverage analysis and discuss the design insights on the optimal solution. We observe that the proposed joint-optimal resource allocation scheme can yield a significant gain in the UAV utility by making it to serve 60% more users as compared to benchmark fixed allocation scheme.
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24.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Dilemma at RF Energy Harvesting Relay : Downlink Energy Relaying or Uplink Information Transfer?
  • 2017
  • Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 16:8, s. 4939-4955
  • 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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25.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Effects of Practical Rechargeability Constraints on Perpetual RF Harvesting Sensor Network Operation
  • 2016
  • Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 4, s. 750-765
  • 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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26.
  • Mishra, Deepak, et al. (författare)
  • Efficacy of Hybrid Energy Beamforming With Phase Shifter Impairments and Channel Estimation Errors
  • 2019
  • Ingår i: IEEE Signal Processing Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1070-9908 .- 1558-2361. ; 26:1, s. 99-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Hybrid energy beamforming (HEB) can reduce the hardware cost, energy consumption, and space constraints associated with massive antenna array transmitter (TX). With a single radio frequency chain having N digitally controlled phase shifter pairs, one per antenna element, theoretically achieving the same performance as a fully digital beamforming architecture with N RF chains, this letter investigates the practical efficacy of the HEB. First adopting the proposed analog phase shifter impairments model and exploiting the channel reciprocity along with the available statistical information, we present a novel approach to obtain an accurate minimum mean-square error estimate for the wireless channel between TX and energy receiver (RX). Then, tight analytical approximation for the global optimal time allocation between uplink channel estimation and downlink energy transfer operations is derived to maximize the mean net harvested energy at RX. Numerical results, validating the analysis and presenting key design insights, show that with an average improvement of 58% over the benchmark scheme, the optimized HEB can help in practically realizing the fully digital array gains.
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27.
  • Mishra, Deepak, et al. (författare)
  • EFFICACY OF MULTIUSER MASSIVE MISO WIRELESS ENERGY TRANSFER UNDER IQ IMBALANCE AND CHANNEL ESTIMATION ERRORS OVER RICIAN FADING
  • 2018
  • Ingår i: 2018 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP). - : IEEE. - 9781538646588 - 9781538646595 ; , s. 3844-3848
  • Konferensbidrag (refereegranskat)abstract
    • We investigate the practical realization of energy beamforming gains in the downlink wireless power transfer from a massive antenna radio frequency (RF) source to multiple single antenna energy harvesting (EH) users. Assuming channel reciprocity for the uplink and downlink channels undergoing Rician fading, we first obtain the least-squares and linear-minimum-mean-square-error channel estimates using the energy-constrained pilot signal transmission from EH users. Due to the usage of low cost hardware at the users and for realizing massive antenna system at the RF source, these estimates are strongly influenced by the transmitter and receiver in-phase-and-quadrature-phase imbalance (IQI). Using these channel estimates, we next derive the harvested power at each user by applying the source transmit precoding that maximizes the sum harvested power among the users. Selected results generated considering practical RF EH system parameters show that IQI and channel estimation errors can lead to about 30% degradation in the sum EH performance.
  •  
28.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Energy-Aware mode selection for throughput maximization in RF-Powered D2D Communications
  • 2018
  • Ingår i: GLOBECOM 2017 - 2017 IEEE Global Communications Conference. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509050192 - 9781509050208 ; , s. 1-6
  • Konferensbidrag (refereegranskat)abstract
    • Doubly-near-far problem in RF-powered networks can be mitigated by choosing appropriate device-To-device (D2D) communication mode and implementing energy-efficient information transfer (IT). In this work, we present a novel RF energy harvesting architecture where each transmitting-receiving user pair is allocated a disjoint channel for its communication which is fully powered by downlink energy transfer (ET) from hybrid access point (HAP). Considering that each user pair can select either D2D or cellular mode of communication, we propose an optimized transmission protocol controlled by the HAP that involves harvested energy-Aware jointly optimal mode selection (MS) and time allocation (TA) for ET and IT to maximize the sum-Throughput. Jointly global optimal solutions are derived by efficiently resolving the combinatorial issue with the help of optimal MS strategy for a given TA for ET. Closed-form expressions for the optimal TA in D2D and cellular modes are also derived to gain further analytical insights. Numerical results show that the joint optimal MS and TA, which significantly outperforms the benchmark schemes in terms of achievable RF-powered sum-Throughput, is closely followed by the optimal TA scheme for D2D users. In fact, about 2/3 fraction of the total user pairs prefer to follow the D2D mode for efficient RF-powered IT.
  •  
29.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Energy harvesting and sustainable M2M communication in 5G mobile technologies
  • 2016
  • Ingår i: Internet of Things (IoT) in 5G Mobile Technologies. - Cham : Springer. - 9783319309118 - 9783319309132 ; , s. 99-125
  • Bokkapitel (refereegranskat)abstract
    • With the fast growth of heterogeneous low-cost and high-end mobile devices, there is a need for green designs for ubiquitous development of Internet of things (IoT) due to both health and environment concerns. Unlike other energy harvesting techniques, radio frequency (RF) energy harvesting offers controlled and predictable energy replenishment, which can aid meeting the quality of service requirements of machine-to-machine (M2M) communications. This chapter evaluates the major challenges on the feasibility of RF-powered sustainable M2M communications in 5G mobile technologies and state-of-the-art research toward their practical implementation. Strategies for improving the RF energy transfer efficiency to realize the perpetual operation of IoT are also discussed.
  •  
30.
  • Mishra, Deepak, et al. (författare)
  • Energy Sustainable IoT With Individual QoS Constraints Through MISO SWIPT Multicasting
  • 2018
  • Ingår i: IEEE Internet of Things Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2327-4662. ; 5:4, s. 2856-2867
  • Tidskriftsartikel (refereegranskat)abstract
    • Enabling technologies for energy sustainable Internet of Things (IoT) are of paramount importance since the proliferation of high data rate demands of low power network devices. In this paper, we consider a multiple input single output (MISO) multicasting system comprising of a multiantenna transmitter (TX) simultaneously transferring information and power to data hungry IoT nodes. Each IoT device is assumed to be equipped with power splitting (PS) hardware that enables energy harvesting (EH) and imposes an individual quality of service (QoS) constraint to the downlink communication. We study the joint design of TX precoding and IoT PS ratios for the considered MISO simultaneous wireless information and power transfer multicasting system with the objective of maximizing the minimum harvested energy among IoT, while satisfying their individual QoS requirements. In our novel EH fairness maximization formulation, we adopt a generic EH model capturing practical rectification operation, and resulting in a nonconvex optimization problem. For this problem, we first present an equivalent semi-definite relaxation formulation and then prove it possesses unique global optimality. We also derive tight upper and lower bounds on the globally optimal solution that are exploited in obtaining low complexity algorithmic implementations for the targeted joint design. Analytical expressions for the optimal TX beamforming directions, power allocation, and PS ratios are also presented. Representative numerical results including comparisons with benchmark designs corroborate the utility of proposed framework and provide useful insights on the interplay of key system parameters.
  •  
31.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Harvested power fairness optimization in MISO SWIPT multicasting IoT with individual constraints
  • 2018
  • Ingår i: 2018 IEEE International Conference on Communications (ICC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538631805 - 9781538631812 ; , s. 1-6
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we consider a Multiple Input Single Output (MISO) multicasting Internet of Things (IoT) system comprising of a multiantenna Transmitter (TX) that simultaneously transfers information and power to low power and data hungry IoT devices. Each IoT device is assumed to be equipped with Power Splitting (PS) hardware that enables Energy Harvesting (EH) and imposes an individual Quality of Service (QoS) constraint to the downlink communication. We study the joint design of TX precoding and IoT PS ratios for the considered MISO Simultaneous Wireless Information and Power Transfer (SWIPT) multicasting IoT with the objective of maximizing the minimum harvested energy among IoT, while satisfying their individual QoS requirements. In our novel EH fairness maximization formulation, we adopt a generic Radio Frequency (RF) EH model capturing practical rectification operation, and resulting in a nonconvex optimization problem. For this problem, we first present an equivalent Semi- Definite Relaxation (SDR) for the considered design problem and prove that it possesses unique global optimality. Then, capitalizing on our derived tight upper and lower bounds on the optimal solution, we present an efficient algorithmic implementation for the jointly optimal TX precoding and IoT PS ratio parameters. Insights on the optimal TX precoding structure are also presented. Representative numerical results including comparisons with benchmark schemes corroborate the usefulness of the proposed design and provide useful insights on the interplay of critical system parameters on the optimized power vs achievable rate trade off.
  •  
32.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Harvested power maximization in QoS-Constrained MIMO SWIPT with generic RF harvesting model
  • 2018
  • Ingår i: 2017 IEEE 7th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538612514 - 9781538612507 - 9781538612521 ; , s. 1-5
  • Konferensbidrag (refereegranskat)abstract
    • We consider the problem of maximizing the harvested power in Multiple Input Multiple Output (MIMO) Simultaneous Wireless Information and Power Transfer (SWIPT) systems with power splitting reception. Different from recently proposed designs, we target with our novel problem formulation at the jointly optimal transmit precoding and receive uniform power splitting (UPS) ratio maximizing the harvested power, while ensuring that the Quality-of-Service (QoS) requirement of the MIMO link is satisfied. We assume generic practical Radio Frequency (RF) Energy Harvesting (EH) receive operation that results in a non-convex optimization problem for the design parameters, which we then solve optimally after formulating it in an equivalent generalized convex form. Our representative results including comparisons of achievable EH gains with benchmark schemes provide key insights on various system parameters.
  •  
33.
  • Mishra, Deepak, 1990-, et al. (författare)
  • I2ER : Integrated information and energy relaying protocol for RF powered communication network
  • 2017
  • Ingår i: IEEE International Conference on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1550-3607 .- 1938-1883. ; , s. 1-646
  • Tidskriftsartikel (refereegranskat)abstract
    • Performance of RF powered communication network is bottlenecked by short downlink energy transfer range and doubly-near-far problem faced in uplink information transfer to Hybrid Access Point (HAP). Theses 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 of R by proposing a novel integrated information and energy relaying (i2 ER) protocol. It also provides insights on the relay positions suited for either energy relaying (ER), or information relaying (IR), or where neither ER nor IR will be useful. In this regard, while considering Rician fading channels, we derive the expression for mean harvested dc power at S via energy transfer from HAP and ER from R. We also derive the closed-form outage probability expression for decode-and-forward relaying with maximal-ratio-combining at HAP over Rician channels. Finally numerical results validating the analytical results and providing insights on the relaying role (ER and/or IR) of RF harvesting helping node are presented.
  •  
34.
  • Mishra, Deepak, 1990-, et al. (författare)
  • i2RES : Integrated information relay and energy supply assisted RF harvesting communication
  • 2017
  • Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 65:3, s. 1274-1288
  • Tidskriftsartikel (refereegranskat)abstract
    • To overcome finite lifetime bottleneck in the ubiquitous deployment of low-power wireless devices in Internet-of-Things, we propose a novel integrated information relay and energy supply (i2RES)-assisted RF harvesting co-operative communication model. i2RES aids the communication between two distant energy-constrained wireless nodes by: 1) RF energy transfer to the source and 2) relaying source data along with supplying energy to the destination. To enable efficient i2RES-powered information transfer to the destination, we first derive and then maximize the delay-limited achievable throughput over Rician channels by jointly optimizing time allocation for information and energy transfer along with relative position of i2RES between source and destination. Although the throughput maximization problem is nonconvex and highly nonlinear, we prove its generalized-convexity and obtain the global-optimal numerical solutions. To gain analytical insights, we also derive tight closed-form approximation for the optimized solutions. Numerical results validate the analysis and demonstrate significant gain in throughput performance via our proposed optimization schemes under practical hardware constraints. Finally, we discuss how the analysis and optimization results can be extended to general RF-EH system settings with relaxed constraints.
  •  
35.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Implementation of multi-path energy routing
  • 2014
  • Ingår i: 2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479949120 ; , s. 1834-1839
  • Konferensbidrag (refereegranskat)abstract
    • Harvesting energy from radio frequency (RF) waves brings us closer to achieving the goal for perpetual operation of a wireless sensor network (WSN) by replenishing the batteries of the sensor nodes. However, due to restrictions on the maximum transmitted power, path loss, and receiver sensitivity, only a small amount of energy can be harvested. While a dedicated RF source alleviates the problem to some extent, novel techniques are required to boost the energy transfer efficiency of the source. In this paper, we provide the first experimental demonstration of multi-path energy routing (MPER) for the case of a sparsely distributed WSNs and show its improved performance over direct energy transfer (DET). In addition, we extend this concept to the case of densely distributed WSNs and experimentally demonstrate and compare the gains obtained by 2- and 3-path energy routing over DET. Our experimental results show that significant energy gains can be achieved in a dense network deployment even when the node to be charged is partially blocked by the neighboring nodes.
  •  
36.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Joint Optimization Schemes for Cooperative Wireless Information and Power Transfer Over Rician Channels
  • 2016
  • Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 64:2, s. 554-571
  • Tidskriftsartikel (refereegranskat)abstract
    • Simultaneous wireless information and power transfer (SWIPT) can lead to uninterrupted network operation by integrating radio frequency (RF) energy harvesting with data communication. In this paper, we consider a two-hop source-relay-destination network and investigate the efficient usage of a decode-and-forward (DF) relay for SWIPT toward the energy-constrained destination. In particular, by assuming a Rician fading environment, we jointly optimize power allocation (PA), relay placement (RP), and power splitting (PS) so as to minimize outage probability under the harvested power constraint at the destination node. We consider the two possible cases of source-to-destination distance: (1) small distance with direct information transfer link; and (2) relatively large distance with no direct reachability. Analytical expressions for individual and joint optimal PA, RP, and PS are obtained by exploiting convexity of outage minimization problem for the no direct link case. In case of direct source-to-destination link, multipseudoconvexity of joint-optimal PA, RP, and PS problem is proved, and alternating optimization is used to find the global optimal solution. Numerical results show that the joint optimal solutions, although strongly influenced by the harvested power requirement at the destination, can provide respectively 64% and 100% outage improvement over the fixed allocation scheme for without and with direct link.
  •  
37.
  • Mishra, Deepak, et al. (författare)
  • Jointly Optimal Spatial Channel Assignment and Power Allocation for MIMO SWIPT Systems
  • 2018
  • Ingår i: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2162-2337 .- 2162-2345. ; 7:2, s. 214-217
  • Tidskriftsartikel (refereegranskat)abstract
    • The joint design of spatial channel assignment and power allocation in multiple input multiple output (MIMO) systems capable of simultaneous wireless information and power transfer is studied. Assuming availability of channel state information at both communications ends, we maximize the harvested energy at the multi-antenna receiver, while satisfying a minimum information rate requirement for the MIMO link. We first derive the globally optimal eigenchannel assignment and power allocation design, and then present a practically motivated tight closed-form approximation for the optimal design parameters. Selected numerical results verify the validity of the optimal solution and provide useful insights on the proposed designs as well as the Pareto-optimal rate-energy tradeoff.
  •  
38.
  • Mishra, Deepak, et al. (författare)
  • Low-Complexity Beamforming Designs and Channel Estimation for Passive-Intelligent-Surface-Assisted MISO Energy Transfer
  • 2023
  • Ingår i: IEEE Internet of Things Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2327-4662. ; 10:9, s. 8286-8304
  • Tidskriftsartikel (refereegranskat)abstract
    • The usage of passive intelligent surface (PIS) is emerging as a low-cost green alternative to massive antenna systems for realizing high-energy beamforming (EB) gains. Considering the limited computational capability and constant-envelope precoding for PIS, we propose three novel low-complexity passive EB designs for optimizing the efficacy of PIS-assisted energy transfer (PET) from a multiantenna power beacon (PB) to a single-antenna energy harvesting (EH) user. The first EB design involves solving a univariate equation, and closed forms expressed are presented for the other two. Further, to maximize the practical utility of PET, we introduce a novel channel estimation (CE) protocol for obtaining least-squares estimators for the channels as required for EB designing. Using them, we also derive closed-form expressions for optimal PIS location and optimal time allocation between CE and PET within each coherence block to maximize the users net harvested energy. Numerical results verify the CE analysis and validate the novel analytical bound derived for received power during PET and proposed PIS designs quality against existing benchmarks. We show that the proposed jointly optimal design for PET can yield a significant improvement of about 15 dB, and a reduced active array size at PB can achieve the desired EB gain with sufficient passive elements at PIS. Finally, we also briefly discuss how the proposed CE and EB designs can be extended to the multiuser settings.
  •  
39.
  • Mishra, Deepak, et al. (författare)
  • Monostatic Backscattering Detection by Multiantenna Reader
  • 2019
  • Ingår i: CONFERENCE RECORD OF THE 2019 FIFTY-THIRD ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS &amp; COMPUTERS. - : IEEE. - 9781728143002 ; , s. 697-701
  • Konferensbidrag (refereegranskat)abstract
    • The limitations of backscatter communication (BSC) can be overcome by exploiting advantages of the multiple-input-multiple-output (MIMO) technology at the reader. In this paper we propose a novel maximum eigenvalue based BSC detection protocol for a monostatic MIMO reader to minimize the underlying bit error rate (BER). Specifically, two orthonormal sequences for the backscattering coefficients (BC) at the single-antenna tag are used to exploit the rank-one property of the cascaded BSC channels in monostatic settings for detection at the reader without requiring any help from the low-power tag in channel estimation. Lastly, the efficacy of the proposed detection protocol is numerically quantified while shedding key insights on the impact of the key simulation parameters like rice factor, orthonormal sequence length, array size, and signal-to-noise-ratio on the achievable BER.
  •  
40.
  • Mishra, Deepak, et al. (författare)
  • Multi-Tag Backscattering to MIMO Reader: Channel Estimation and Throughput Fairness
  • 2019
  • Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 18:12, s. 5584-5599
  • Tidskriftsartikel (refereegranskat)abstract
    • Green low power networking with the least requirement of dedicated radio resources is need of the hour which has led to the upsurge of backscatter communication (BSC) technology. However, this inherent potential of BSC is challenged by hardware constraints of the underlying tags. We address this timely concern by investigating the practical efficacy of multiple-input-multiple-output (MIMO) technology in overcoming the fundamental limitations of BSC. Specifically, we first introduce a novel least-squares based channel estimation (CE) protocol for multi-tag BSC settings that takes care of both the unintended ambient reflections and the inability of tags in performing estimation by themselves. Then using it, a nontrivial low-complexity algorithm is proposed to obtain the optimal transceiver designs for the multiantenna reader to maximize the minimum value of the lower-bounded backscattered throughput among the single-antenna semi-passive tags. Additional analytical insights on both individually and jointly-optimal precoding vector and detector matrix at the reader are provided by exploring the asymptotically-optimal transceiver designs. Lastly detailed numerical investigation is carried out to validate the theoretical results and quantify the practically realizable throughput fairness. Specifically, more than seven-fold increase in the common-backscattered-throughput among tags as achieved by the proposed designs over the relevant benchmarks corroborates their practical significance.
  •  
41.
  • Mishra, Deepak, et al. (författare)
  • Novel Multiantenna Reader Design for Multi-Tag Backscattered Throughput Fairness Maximization
  • 2019
  • Ingår i: 2019 IEEE 20TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC 2019). - : IEEE. - 9781538665282
  • Konferensbidrag (refereegranskat)abstract
    • The green low power networking potential of backscatter communication technology can be practically realized by efficiently using a multiantenna reader for tackling the hardware constraints of the underlying tags. We address this timely requirement by investigating the optimal transceiver designs for the multiantenna reader to maximize the minimum backscattered throughput among the single-antenna semi-passive tags. Novel analytical insights on the jointly-optimal precoding vector and detector matrix at the reader are also provided by exploring the asymptotically-optimal designs. Lastly, the numerical results corroborate the nontrivial analytical proposals and demonstrate a significant 47% increase in achievable common-backscattered-throughput among tags as compared to the relevant benchmarks.
  •  
42.
  • Mishra, Deepak, et al. (författare)
  • Optimal Channel Estimation for Hybrid Energy Beamforming Under Phase Shifter Impairments
  • 2019
  • Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 67:6, s. 4309-4325
  • Tidskriftsartikel (refereegranskat)abstract
    • Smart multiantenna wireless power transmission can enable perpetual operation of energy harvesting (EH) nodes in the Internet-of-Things. Moreover, to overcome the increased hardware cost and space constraints associated with having large antenna arrays at the radio frequency (RF) energy source, the hybrid energy beamforming (EBF) architecture with single RF chain can be adopted. Using the recently proposed hybrid EBF architecture modeling the practical analog phase shifter impairments (API), we derive the optimal least-squares estimator for the energy source to an EH user channel. Next, the average harvested power at the user is derived while considering the nonlinear RF EH model and a tight analytical approximation for it is also presented by exploring the practical limits on the API. Using these developments, the jointly global optimal transmit power and time allocation for channel estimation (CE) and EBF phases, that maximizes the average energy stored at the EH user is derived in closed form. Numerical results validate the proposed analysis and present nontrivial design insights on the impact of API and CE errors on the achievable EBF performance. It is shown that the optimized hybrid EBF protocol with joint resource allocation yields an average performance improvement of 37% over benchmark fixed allocation scheme.
  •  
43.
  • Mishra, Deepak, et al. (författare)
  • Optimal Channel Estimation for Reciprocity-Based Backscattering With a Full-Duplex MIMO Reader
  • 2019
  • Ingår i: IEEE Transactions on Signal Processing. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1053-587X .- 1941-0476. ; 67:6, s. 1662-1677
  • Tidskriftsartikel (refereegranskat)abstract
    • Backscatter communication (BSC) technology can enable ubiquitous deployment of low-cost sustainable wireless devices. In this paper, we investigate the efficacy of a full-duplex multiple-input-multiple-output reader for enhancing the limited communication range of monostatic BSC systems. As this performance is strongly influenced by the channel estimation (CE) quality, we first derive a novel least-squares estimator for the forward and backward links between the reader and the tag, assuming that reciprocity holds and K orthogonal pilots are transmitted from the first K antennas of an N antenna reader. We also obtain the corresponding linear minimum-mean square-error estimate for the backscattered channel. After defining the transceiver design at the reader using these estimates, we jointly optimize the number of orthogonal pilots and energy allocation for the CE and information decoding phases to maximize the average backscattered signal-to-noise ratio (SNR) for efficiently decoding the tags messages. The unimodality of this SNR in optimization variables along with a tight analytical approximation for the jointly global optimal design is also discoursed. Lastly, the selected numerical results validate the proposed analysis, present key insights into the optimal resource utilization at reader, and quantify the achievable gains over the benchmark schemes.
  •  
44.
  • Mishra, Deepak, et al. (författare)
  • Optimal Least Squares Estimator and Precoder for Energy Beamforming Over IQ-Impaired Channels
  • 2019
  • Ingår i: IEEE Signal Processing Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1070-9908 .- 1558-2361. ; 26:8, s. 1207-1211
  • Tidskriftsartikel (refereegranskat)abstract
    • Usage of low-cost hardware in large antenna arrays and low-power wireless devices in Internet of Things (IoT) has led to the degradation of practical beamforming gains due to the underlying hardware impairments, such as in-phase and quadrature-phase imbalance (IQI). To address this timely concern, we present a new nontrivial closed-form expression for the globally optimal least squares estimator (LSE) for the IQI-influenced channel between a multiantenna transmitter and single-antenna IoT device. Thereafter, to maximize the realistic transmit beamforming gains, a novel precoder design is derived that accounts for the underlying IQI for maximizing received power in both single and multiuser settings. Finally, the simulation results, demonstrating a significant -8 dB improvement in the mean squared error of the proposed LSE over existing benchmarks, show that the optimal precoder designing is more critical than accurately estimating IQI-impaired channels. Also, the proposed jointly optimal LSE and beamformer outperforms the existing designs by providing 24% enhancement in mean signal power received under IQI.
  •  
45.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Optimal power allocation and relay placement for wireless information and RF power transfer
  • 2016
  • Ingår i: IEEE International Conference on Communications (ICC) Date of Conference. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1-6
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we develop an optimization framework to jointly optimize the efficiency of wireless information and RF power transfer to the destination of a two hop decode- and-forward source-relay-destination network. In particular, we investigate the performance of three optimization schemes: (i) optimal power allocation (PA) with fixed relay placement (RP), (ii) optimal RP with fixed PA, and (iii) joint optimization of PA and RP, for minimizing the outage probability under the harvested power constraint at the destination. In absence of direct source to destination reachability, closed-form global-optimal solutions are obtained for all three optimization schemes. Numerical results show that the optimized schemes significantly outperform fixed allocation and the joint optimal PA and RP provides an outage improvement of about 35%. Also, a tradeoff exists between minimized outage probability and minimum required average harvested power at destination for its uninterrupted operation.
  •  
46.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Optimal relay placement in two-hop RF energy transfer
  • 2015
  • Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 63:5, s. 1635-1647
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, wireless radio frequency energy transfer (RFET) has emerged as an effective technology for prolonging lifetime of the energy-limited wireless sensor networks. However, low RFET efficiency is still a fundamental bottleneck in its widespread usage. Multi-hop RF energy transfer (MHET) can improve the RFET efficiency by deploying relay nodes that scavenge the dispersed energy and transfer it to the nearby sensor node. The efficiency of MHET is strongly influenced by the relay node’s placement. To maximize the RFET efficiency for a two-hop scenario, in this paper a novel optimization model is proposed to determine the optimal relay placement (ORP) on an Euclidean x-y plane. Nontrivial tradeoff between the energy scavenged at the relay versus the effective energy delivered by the relay to the target node is investigated. Due to the nonconvex and highly nonlinear nature of the optimization problem, an α-based branch and bound algorithm has been used. The proposed optimization model is further extended by incorporating distributed beamforming to enhance the RFET efficiency. Numerical results illustrate that the proposed algorithm provides convergence to the ∈-global optimal solution in a few iterations, and ORP provides significant energy saving over arbitrary relay positions for commercial RF energy harvesting systems.
  •  
47.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Optimal time allocation for RF-powered DF relay-assisted cooperative communication
  • 2016
  • Ingår i: Electronics Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0013-5194 .- 1350-911X. ; 52:14, s. 1274-1276
  • Tidskriftsartikel (refereegranskat)abstract
    • A decode-and-forward (DF) relay-assisted RF-powered cooperative communication between an RF energy harvesting source and an information sink is considered. DF relay aids the communication between these two distant wireless nodes by (i) RF energy transfer to the source, and (ii) relaying source data to the sink. To enable efficient RF-powered delay-constrained information transfer to the sink under Rayleigh fading, joint global-optimal time allocations for information and energy transfer are derived. Impact of relay position on throughput and optimality of the analytical solutions are numerically investigated.
  •  
48.
  • Mishra, Deepak, et al. (författare)
  • Optimizing Reciprocity-Based Backscattering with a Full-Duplex Antenna Array Reader
  • 2018
  • Ingår i: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC). - : IEEE. - 9781538635124 ; , s. 11-15
  • Konferensbidrag (refereegranskat)abstract
    • Backscatter communication (BSC) technology can enable ubiquitous deployment of low-cost sustainable wireless devices. In this work we investigate the efficacy of a full-duplex antenna array reader in overcoming the limited communication range bottleneck of monostatic BSCs. As performance is strongly influenced by the channel estimation (CE) quality, we first derive a novel least-squares estimator (LSE) for the forward and backward links between the reader and the tag, assuming that reciprocity holds. After defining the transceiver design at reader using this LSE, we optimize the energy allocation for the CE and information decoding phases, to maximize the average backscattered signal-to-noise ratio (SNR). The unimodality of this SNR in optimization variable along with a tight approximation for the global optimal design are also presented. Lastly, numerical results validate the proposed analysis and present key insights into the optimal LSE and energy allocation.
  •  
49.
  • Mishra, Deepak, et al. (författare)
  • Passive Intelligent Surface Assisted MIMO Powered Sustainable IoT
  • 2020
  • Ingår i: ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : IEEE. - 9781509066322 - 9781509066315 ; , s. 8961-8965
  • Konferensbidrag (refereegranskat)abstract
    • Lately, Passive Intelligent Surfaces (PIS) are being recognized to play an important role in meeting the timely demand of low-cost green sustainable Internet of Things (IoT). In this paper, we focus on maximizing the sum received power among the energy harvesting IoT users by jointly optimizing the active precoder for multi-antenna power beacon and the passive constant-envelope precoding based phase shifters (PS) design for PIS. Here, a multiuser channel estimation protocol is first introduced to obtain the least-squares estimators for the underlying effective cascaded channel links involved in the PIS assisted multi-antenna wireless power transfer as desired for the optimal precoder and PS designing. Thereafter, new semi-closed-form expressions for the proposed optimal active and passive beamforming design are derived so as to meet the low-complexity requirements of IoT communications. Finally, the numerical results are presented to validate the key nontrivial analytical claims and demonstrate the significant performance enhancement in terms of sum harvested energy among IoT users over conventional designs.
  •  
50.
  • Mishra, Deepak, 1990-, et al. (författare)
  • Relay-assisted RF harvesting sensor networks
  • 2016
  • Ingår i: 2016 13th IEEE Annual Consumer Communications &amp; Networking Conference (CCNC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 791-792
  • Konferensbidrag (refereegranskat)abstract
    • We propose a relay-assisted RF harvesting sensor network (R2FSN) model, where the field nodes having finite battery capacity are powered by RF energy transfer (RFET) from a single relay, thus leading to perpetual sensor network operation. The relay node also forwards the field data to the information sink in a two-hop, half-duplex decode-and-forward fashion. We derive closed-form expression of the average end-to-end signal-to-noise ratio (SNR) for each source-destination link in cooperative R2FSN. The performance improvement provided by R2FSN over conventional RF-powered networks is numerically investigated along with the impact of RFET time and relay location on the maximum and minimum average end-to-end SNR over all links.
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