Fundamentals of Wireless Information and Power Transfer: From RF Energy Harvester Models to Signal and System Designs (1803.07123v1)

Abstract: Radio waves carry both energy and information simultaneously. Nevertheless, Radio-Frequency (RF) transmission of these quantities have traditionally been treated separately. Currently, we are experiencing a paradigm shift in wireless network design, namely unifying wireless transmission of information and power so as to make the best use of the RF spectrum and radiations as well as the network infrastructure for the dual purpose of communicating and energizing. In this paper, we review and discuss recent progress on laying the foundations of the envisioned dual purpose networks by establishing a signal theory and design for Wireless Information and Power Transmission (WIPT) and identifying the fundamental tradeoff between conveying information and power wirelessly. We start with an overview of WIPT challenges and technologies, namely Simultaneous Wireless Information and Power Transfer (SWIPT),Wirelessly Powered Communication Network (WPCN), and Wirelessly Powered Backscatter Communication (WPBC). We then characterize energy harvesters and show how WIPT signal and system designs crucially revolve around the underlying energy harvester model. To that end, we highlight three different energy harvester models, namely one linear model and two nonlinear models, and show how WIPT designs differ for each of them in single-user and multi-user deployments. Topics discussed include rate-energy region characterization, transmitter and receiver architecture, waveform design, modulation, beamforming and input distribution optimizations, resource allocation, and RF spectrum use. We discuss and check the validity of the different energy harvester models and the resulting signal theory and design based on circuit simulations, prototyping and experimentation. We also point out numerous directions that are promising for future research.

• The paper introduces a unified design that integrates wireless data and power transfer via SWIPT, WPCN, and WPBC paradigms.
• It compares three energy harvester models—linear, nonlinear diode, and saturation nonlinear—to reveal their distinct impact on performance.
• Experimental and simulation results validate channel-adaptive designs that boost harvested power and efficiency, enabling energy-autonomous IoT systems.

Overview of Wireless Information and Power Transfer: Theoretical Foundations and System Design

The paper "Fundamentals of Wireless Information and Power Transfer: From RF Energy Harvester Models to Signal and System Designs" offers a comprehensive examination of the developing integration of wireless information transfer (WIT) and wireless power transfer (WPT), challenging traditional design paradigms by proposing unified solutions for simultaneous data and energy transmission.

Key Contributions

The authors delineate several key themes:

1. Conceptual Framework for WIPT: The convergence of wireless communication and power into a unified design paradigm, exemplified in Simultaneous Wireless Information and Power Transfer (SWIPT), Wirelessly Powered Communication Networks (WPCN), and Wirelessly Powered Backscatter Communication (WPBC).
2. Energy Harvester Models: Three distinct models are examined. The linear model simplifies the relationship between input and output powers; however, it lacks nuance when dealing with real-world nonlinearities. Conversely, the nonlinear diode model incorporates these complexities through higher-order terms. Lastly, the saturation nonlinear model addresses output power plateauing using a logistic function representing the harvested power.
3. Signal and System Design Dependencies: The paper asserts that accurate modeling of energy harvesters is crucial for effective system design, challenging the adequacy of naive linear understandings and promoting advanced signal adaptations to exploit nonlinear behaviors.
4. Rate-Energy Trade-offs: Across single and multi-user deployments, the interplay between achievable data rates and harvested energies varies significantly based on the chosen energy harvester model, with non-traditional nonlinear approaches sometimes unlocking superior performance metrics.
5. Prototype Validations: Experimental and simulation results for channel-adaptive designs affirm the theoretical predictions, emphasizing increased harvested power and efficiency when accountably integrating nonlinear characteristics.

Implications and Future Directions

From a theoretical perspective, the exploration encourages revisiting foundational WPT assumptions, including waveform design and modulation strategy adjustments, ultimately suggesting a complex interdependency between harvester characteristics and optimal transmission protocols.

Practically, the insights are directly relevant to the deployment of energy-autonomous IoT devices and systems, as they facilitate reduced energy dependencies, promoting infrastructure scalability within next-generation wireless networks.

Potential future developments involve refining energy harvester models to enhance predictive fidelity, optimizing signal processing algorithms under constrained resources, and further exploring the multi-user communication scenarios to harvest peak efficiency.

In conclusion, the research elucidates a meaningful step toward a deeply integrated information and power wireless system, presenting theoretical and practical frameworks ripe for exploration by the wireless research community.