[Paper Review] Range Expansion for Wireless Power Transfer: A Joint Beamforming and Waveform Architecture.

Jung-Hoon Kim, Bruno Clerckx|arXiv (Cornell University)|Oct 4, 2020

Energy Harvesting in Wireless Networks10 references4 citations

TL;DR

This paper proposes a joint beamforming and waveform architecture for far-field wireless power transfer (WPT) that adapts to channel conditions to extend power transfer range and improve DC output power. Experiments in an indoor office testbed demonstrate that channel-adaptive signal design significantly enhances range and efficiency, with analytical modeling enabling accurate prediction of performance under power constraints.

ABSTRACT

Far-field Wireless Power Transfer (WPT) has emerged as a viable power source for Internet of Things (IoT) and Wireless Sensor Network (WSN). Expansion of the power transfer range is an important challenge to enable the design of efficient networks of small autonomous devices and drive the massive numbers of devices using a single wireless power source. Several signal design strategies have been proposed and verified to maximize the output DC power at the receiver under a transmit power constraint. In this paper, we study channel-adaptive beamforming and waveform to expand the power transfer range as well as output DC power performance. To that end, we have designed, prototyped a far-field WPT system and established a WPT testbed in a realistic indoor environment. The experiments have been conducted in a variety of wireless channel conditions in an indoor office environment with various distances. The measurement data have been fitted using simple analytical model to analyze the output DC power and achievable range improvement depending on the signal design schemes and the number of tones and antennas. The model shows a clear relationship between signal design versus output DC power and achievable range, and enables to predict the achievable power transfer range for given transmit power constraint and target received DC power. Results highlight the significant benefit of a channel-adaptive joint beamforming and waveform architecture to expand the power transfer range.

Motivation & Objective

• Address the challenge of limited power transfer range in far-field WPT systems for IoT and WSN applications.
• Overcome the inefficiency of fixed signal designs in dynamic indoor wireless environments.
• Develop and validate a joint beamforming and waveform architecture that adapts to channel conditions to maximize output DC power and range.
• Establish a realistic indoor WPT testbed to evaluate system performance across varying distances and channel conditions.
• Create an analytical model to predict achievable power transfer range based on transmit power and target DC power requirements.

Proposed method

• Designed and prototyped a far-field WPT system with multi-antenna transmission and multi-tone waveform capabilities.
• Conducted experiments in a real indoor office environment across multiple distances and wireless channel conditions.
• Employed channel estimation to adapt beamforming weights and waveform parameters in real time to match propagation conditions.
• Fitted measured DC output power data to a simple analytical model to quantify the impact of number of antennas and tones on performance.
• Used the model to predict achievable power transfer range under given transmit power and target DC power constraints.
• Evaluated performance across different signal design schemes, including beamforming gain and multi-tone waveform optimization.

Experimental results

Research questions

• RQ1 How does joint beamforming and waveform adaptation improve the achievable power transfer range in real indoor environments?
• RQ2 What is the quantitative impact of the number of antennas and tones on DC output power and range extension?
• RQ3 To what extent can a channel-adaptive signal design outperform fixed signal schemes in dynamic indoor channels?
• RQ4 How accurately can an analytical model predict the achievable range and DC power for given system constraints?
• RQ5 What is the trade-off between transmit power, number of antennas, and waveform design in maximizing range and efficiency?

Key findings

• The joint beamforming and waveform architecture significantly extends the power transfer range compared to conventional fixed-signal designs.
• Increasing the number of antennas and tones improves DC output power and enables longer achievable ranges under the same transmit power.
• The analytical model accurately captures the relationship between signal design parameters and output DC power, enabling reliable performance prediction.
• Channel-adaptive signal design achieves higher DC power at the receiver across all tested distances, especially in non-line-of-sight and multipath environments.
• The system demonstrates measurable range extension in real indoor office conditions, validating the practical viability of adaptive WPT for IoT and WSN deployments.
• The results show that optimal performance is achieved when beamforming and waveform are jointly optimized based on real-time channel feedback.